Nonperturbative-transverse-momentum broadening in dihadron angular correlations in \sqrt{s_{{}_{NN}}}=200 GeV proton-nucleus collisions

Nonperturbative-transverse-momentum broadening in dihadron angular correlations in GeV proton-nucleus collisions

C. Aidala Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040, USA    Y. Akiba akiba@rcf.rhic.bnl.gov RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    M. Alfred Department of Physics and Astronomy, Howard University, Washington, DC 20059, USA    V. Andrieux Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040, USA    N. Apadula Iowa State University, Ames, Iowa 50011, USA    H. Asano Kyoto University, Kyoto 606-8502, Japan RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan    B. Azmoun Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    V. Babintsev IHEP Protvino, State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, 142281, Russia    N.S. Bandara Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003-9337, USA    K.N. Barish University of California-Riverside, Riverside, California 92521, USA    S. Bathe Baruch College, City University of New York, New York, New York, 10010 USA RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    A. Bazilevsky Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    M. Beaumier University of California-Riverside, Riverside, California 92521, USA    R. Belmont University of Colorado, Boulder, Colorado 80309, USA    A. Berdnikov Saint Petersburg State Polytechnic University, St. Petersburg, 195251 Russia    Y. Berdnikov Saint Petersburg State Polytechnic University, St. Petersburg, 195251 Russia    D.S. Blau National Research Center “Kurchatov Institute”, Moscow, 123098 Russia National Research Nuclear University, MEPhI, Moscow Engineering Physics Institute, Moscow, 115409, Russia    M. Boer Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA    J.S. Bok New Mexico State University, Las Cruces, New Mexico 88003, USA    M.L. Brooks Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA    J. Bryslawskyj Baruch College, City University of New York, New York, New York, 10010 USA University of California-Riverside, Riverside, California 92521, USA    V. Bumazhnov IHEP Protvino, State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, 142281, Russia    S. Campbell Columbia University, New York, New York 10027 and Nevis Laboratories, Irvington, New York 10533, USA    V. Canoa Roman Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    R. Cervantes Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    C.Y. Chi Columbia University, New York, New York 10027 and Nevis Laboratories, Irvington, New York 10533, USA    M. Chiu Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    I.J. Choi University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA    J.B. Choi Deceased Chonbuk National University, Jeonju, 561-756, Korea    Z. Citron Weizmann Institute, Rehovot 76100, Israel    M. Connors Georgia State University, Atlanta, Georgia 30303, USA RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    N. Cronin Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    M. Csanád ELTE, Eötvös Loránd University, H-1117 Budapest, Pázmány P. s. 1/A, Hungary    T. Csörgő Eszterházy Károly University, Károly Róbert Campus, H-3200 Gyöngyös, Mátrai út 36, Hungary Institute for Particle and Nuclear Physics, Wigner Research Centre for Physics, Hungarian Academy of Sciences (Wigner RCP, RMKI) H-1525 Budapest 114, POBox 49, Budapest, Hungary    T.W. Danley Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701, USA    M.S. Daugherity Abilene Christian University, Abilene, Texas 79699, USA    G. David Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA Debrecen University, H-4010 Debrecen, Egyetem tér 1, Hungary Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    K. DeBlasio University of New Mexico, Albuquerque, New Mexico 87131, USA    K. Dehmelt Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    A. Denisov IHEP Protvino, State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, 142281, Russia    A. Deshpande Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973-5000, USA Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    E.J. Desmond Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    A. Dion Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    D. Dixit Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    J.H. Do Yonsei University, IPAP, Seoul 120-749, Korea    A. Drees Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    K.A. Drees Collider-Accelerator Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    J.M. Durham Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA    A. Durum IHEP Protvino, State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, 142281, Russia    A. Enokizono RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan Physics Department, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima, Tokyo 171-8501, Japan    H. En’yo RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan    S. Esumi Tomonaga Center for the History of the Universe, University of Tsukuba, Tsukuba, Ibaraki 305, Japan    B. Fadem Muhlenberg College, Allentown, Pennsylvania 18104-5586, USA    W. Fan Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    N. Feege Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    D.E. Fields University of New Mexico, Albuquerque, New Mexico 87131, USA    M. Finger Charles University, Ovocný trh 5, Praha 1, 116 36, Prague, Czech Republic    M. Finger, Jr. Charles University, Ovocný trh 5, Praha 1, 116 36, Prague, Czech Republic    S.L. Fokin National Research Center “Kurchatov Institute”, Moscow, 123098 Russia    J.E. Frantz Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701, USA    A. Franz Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    A.D. Frawley Florida State University, Tallahassee, Florida 32306, USA    Y. Fukuda Tomonaga Center for the History of the Universe, University of Tsukuba, Tsukuba, Ibaraki 305, Japan    C. Gal Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    P. Gallus Czech Technical University, Zikova 4, 166 36 Prague 6, Czech Republic    P. Garg Department of Physics, Banaras Hindu University, Varanasi 221005, India Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    H. Ge Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    F. Giordano University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA    Y. Goto RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    N. Grau Department of Physics, Augustana University, Sioux Falls, South Dakota 57197, USA    S.V. Greene Vanderbilt University, Nashville, Tennessee 37235, USA    M. Grosse Perdekamp University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA    T. Gunji Center for Nuclear Study, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan    H. Guragain Georgia State University, Atlanta, Georgia 30303, USA    T. Hachiya Nara Women’s University, Kita-uoya Nishi-machi Nara 630-8506, Japan RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    J.S. Haggerty Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    K.I. Hahn Ewha Womans University, Seoul 120-750, Korea    H. Hamagaki Center for Nuclear Study, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan    H.F. Hamilton Abilene Christian University, Abilene, Texas 79699, USA    S.Y. Han Ewha Womans University, Seoul 120-750, Korea RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan    J. Hanks Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    S. Hasegawa Advanced Science Research Center, Japan Atomic Energy Agency, 2-4 Shirakata Shirane, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195, Japan    T.O.S. Haseler Georgia State University, Atlanta, Georgia 30303, USA    X. He Georgia State University, Atlanta, Georgia 30303, USA    T.K. Hemmick Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    J.C. Hill Iowa State University, Ames, Iowa 50011, USA    K. Hill University of Colorado, Boulder, Colorado 80309, USA    A. Hodges Georgia State University, Atlanta, Georgia 30303, USA    R.S. Hollis University of California-Riverside, Riverside, California 92521, USA    K. Homma Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, Japan    B. Hong Korea University, Seoul, 136-701, Korea    T. Hoshino Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, Japan    N. Hotvedt Iowa State University, Ames, Iowa 50011, USA    J. Huang Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    S. Huang Vanderbilt University, Nashville, Tennessee 37235, USA    K. Imai Advanced Science Research Center, Japan Atomic Energy Agency, 2-4 Shirakata Shirane, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195, Japan    M. Inaba Tomonaga Center for the History of the Universe, University of Tsukuba, Tsukuba, Ibaraki 305, Japan    A. Iordanova University of California-Riverside, Riverside, California 92521, USA    D. Isenhower Abilene Christian University, Abilene, Texas 79699, USA    D. Ivanishchev PNPI, Petersburg Nuclear Physics Institute, Gatchina, Leningrad region, 188300, Russia    B.V. Jacak Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    M. Jezghani Georgia State University, Atlanta, Georgia 30303, USA    Z. Ji Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    X. Jiang Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA    B.M. Johnson Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA Georgia State University, Atlanta, Georgia 30303, USA    D. Jouan IPN-Orsay, Univ. Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, BP1, F-91406, Orsay, France    D.S. Jumper University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA    J.H. Kang Yonsei University, IPAP, Seoul 120-749, Korea    D. Kapukchyan University of California-Riverside, Riverside, California 92521, USA    S. Karthas Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    D. Kawall Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003-9337, USA    A.V. Kazantsev National Research Center “Kurchatov Institute”, Moscow, 123098 Russia    V. Khachatryan Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    A. Khanzadeev PNPI, Petersburg Nuclear Physics Institute, Gatchina, Leningrad region, 188300, Russia    C. Kim University of California-Riverside, Riverside, California 92521, USA Korea University, Seoul, 136-701, Korea    E.-J. Kim Chonbuk National University, Jeonju, 561-756, Korea    M. Kim RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan Department of Physics and Astronomy, Seoul National University, Seoul 151-742, Korea    D. Kincses ELTE, Eötvös Loránd University, H-1117 Budapest, Pázmány P. s. 1/A, Hungary    E. Kistenev Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    J. Klatsky Florida State University, Tallahassee, Florida 32306, USA    P. Kline Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    T. Koblesky University of Colorado, Boulder, Colorado 80309, USA    D. Kotov PNPI, Petersburg Nuclear Physics Institute, Gatchina, Leningrad region, 188300, Russia Saint Petersburg State Polytechnic University, St. Petersburg, 195251 Russia    S. Kudo Tomonaga Center for the History of the Universe, University of Tsukuba, Tsukuba, Ibaraki 305, Japan    B. Kurgyis ELTE, Eötvös Loránd University, H-1117 Budapest, Pázmány P. s. 1/A, Hungary    K. Kurita Physics Department, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima, Tokyo 171-8501, Japan    Y. Kwon Yonsei University, IPAP, Seoul 120-749, Korea    J.G. Lajoie Iowa State University, Ames, Iowa 50011, USA    A. Lebedev Iowa State University, Ames, Iowa 50011, USA    S. Lee Yonsei University, IPAP, Seoul 120-749, Korea    S.H. Lee Iowa State University, Ames, Iowa 50011, USA Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    M.J. Leitch Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA    Y.H. Leung Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    N.A. Lewis Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040, USA    X. Li Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA    S.H. Lim Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA Yonsei University, IPAP, Seoul 120-749, Korea    M.X. Liu Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA    V.-R. Loggins University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA    S. Lökös ELTE, Eötvös Loránd University, H-1117 Budapest, Pázmány P. s. 1/A, Hungary Eszterházy Károly University, Károly Róbert Campus, H-3200 Gyöngyös, Mátrai út 36, Hungary    K. Lovasz Debrecen University, H-4010 Debrecen, Egyetem tér 1, Hungary    D. Lynch Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    T. Majoros Debrecen University, H-4010 Debrecen, Egyetem tér 1, Hungary    Y.I. Makdisi Collider-Accelerator Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    M. Makek Department of Physics, Faculty of Science, University of Zagreb, Bijenička c. 32 HR-10002 Zagreb, Croatia    V.I. Manko National Research Center “Kurchatov Institute”, Moscow, 123098 Russia    E. Mannel Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    M. McCumber Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA    P.L. McGaughey Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA    D. McGlinchey University of Colorado, Boulder, Colorado 80309, USA Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA    C. McKinney University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA    M. Mendoza University of California-Riverside, Riverside, California 92521, USA    W.J. Metzger Eszterházy Károly University, Károly Róbert Campus, H-3200 Gyöngyös, Mátrai út 36, Hungary    A.C. Mignerey University of Maryland, College Park, Maryland 20742, USA    D.E. Mihalik Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    A. Milov Weizmann Institute, Rehovot 76100, Israel    D.K. Mishra Bhabha Atomic Research Centre, Bombay 400 085, India    J.T. Mitchell Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    G. Mitsuka KEK, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    S. Miyasaka RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan Department of Physics, Tokyo Institute of Technology, Oh-okayama, Meguro, Tokyo 152-8551, Japan    S. Mizuno RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan Tomonaga Center for the History of the Universe, University of Tsukuba, Tsukuba, Ibaraki 305, Japan    P. Montuenga University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA    T. Moon Yonsei University, IPAP, Seoul 120-749, Korea    D.P. Morrison Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    S.I. Morrow Vanderbilt University, Nashville, Tennessee 37235, USA    T. Murakami Kyoto University, Kyoto 606-8502, Japan RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan    J. Murata RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan Physics Department, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima, Tokyo 171-8501, Japan    K. Nagai Department of Physics, Tokyo Institute of Technology, Oh-okayama, Meguro, Tokyo 152-8551, Japan    K. Nagashima Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, Japan RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan    T. Nagashima Physics Department, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima, Tokyo 171-8501, Japan    J.L. Nagle University of Colorado, Boulder, Colorado 80309, USA    M.I. Nagy ELTE, Eötvös Loránd University, H-1117 Budapest, Pázmány P. s. 1/A, Hungary    I. Nakagawa RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    K. Nakano RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan Department of Physics, Tokyo Institute of Technology, Oh-okayama, Meguro, Tokyo 152-8551, Japan    C. Nattrass University of Tennessee, Knoxville, Tennessee 37996, USA    T. Niida Tomonaga Center for the History of the Universe, University of Tsukuba, Tsukuba, Ibaraki 305, Japan    R. Nishitani Nara Women’s University, Kita-uoya Nishi-machi Nara 630-8506, Japan    R. Nouicer Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    T. Novák Eszterházy Károly University, Károly Róbert Campus, H-3200 Gyöngyös, Mátrai út 36, Hungary Institute for Particle and Nuclear Physics, Wigner Research Centre for Physics, Hungarian Academy of Sciences (Wigner RCP, RMKI) H-1525 Budapest 114, POBox 49, Budapest, Hungary    N. Novitzky Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    A.S. Nyanin National Research Center “Kurchatov Institute”, Moscow, 123098 Russia    E. O’Brien Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    C.A. Ogilvie Iowa State University, Ames, Iowa 50011, USA    J.D. Orjuela Koop University of Colorado, Boulder, Colorado 80309, USA    J.D. Osborn Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040, USA    A. Oskarsson Department of Physics, Lund University, Box 118, SE-221 00 Lund, Sweden    G.J. Ottino University of New Mexico, Albuquerque, New Mexico 87131, USA    K. Ozawa KEK, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan Tomonaga Center for the History of the Universe, University of Tsukuba, Tsukuba, Ibaraki 305, Japan    V. Pantuev Institute for Nuclear Research of the Russian Academy of Sciences, prospekt 60-letiya Oktyabrya 7a, Moscow 117312, Russia    V. Papavassiliou New Mexico State University, Las Cruces, New Mexico 88003, USA    J.S. Park Department of Physics and Astronomy, Seoul National University, Seoul 151-742, Korea    S. Park RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan Department of Physics and Astronomy, Seoul National University, Seoul 151-742, Korea Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    S.F. Pate New Mexico State University, Las Cruces, New Mexico 88003, USA    M. Patel Iowa State University, Ames, Iowa 50011, USA    W. Peng Vanderbilt University, Nashville, Tennessee 37235, USA    D.V. Perepelitsa Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA University of Colorado, Boulder, Colorado 80309, USA    G.D.N. Perera New Mexico State University, Las Cruces, New Mexico 88003, USA    D.Yu. Peressounko National Research Center “Kurchatov Institute”, Moscow, 123098 Russia    C.E. PerezLara Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    J. Perry Iowa State University, Ames, Iowa 50011, USA    R. Petti Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    M. Phipps Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA    C. Pinkenburg Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    R.P. Pisani Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    A. Pun Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701, USA    M.L. Purschke Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    P.V. Radzevich Saint Petersburg State Polytechnic University, St. Petersburg, 195251 Russia    K.F. Read Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA University of Tennessee, Knoxville, Tennessee 37996, USA    D. Reynolds Chemistry Department, Stony Brook University, SUNY, Stony Brook, New York 11794-3400, USA    V. Riabov National Research Nuclear University, MEPhI, Moscow Engineering Physics Institute, Moscow, 115409, Russia PNPI, Petersburg Nuclear Physics Institute, Gatchina, Leningrad region, 188300, Russia    Y. Riabov PNPI, Petersburg Nuclear Physics Institute, Gatchina, Leningrad region, 188300, Russia Saint Petersburg State Polytechnic University, St. Petersburg, 195251 Russia    D. Richford Baruch College, City University of New York, New York, New York, 10010 USA    T. Rinn Iowa State University, Ames, Iowa 50011, USA    S.D. Rolnick University of California-Riverside, Riverside, California 92521, USA    M. Rosati Iowa State University, Ames, Iowa 50011, USA    Z. Rowan Baruch College, City University of New York, New York, New York, 10010 USA    J. Runchey Iowa State University, Ames, Iowa 50011, USA    A.S. Safonov Saint Petersburg State Polytechnic University, St. Petersburg, 195251 Russia    T. Sakaguchi Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    H. Sako Advanced Science Research Center, Japan Atomic Energy Agency, 2-4 Shirakata Shirane, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195, Japan    V. Samsonov National Research Nuclear University, MEPhI, Moscow Engineering Physics Institute, Moscow, 115409, Russia PNPI, Petersburg Nuclear Physics Institute, Gatchina, Leningrad region, 188300, Russia    M. Sarsour Georgia State University, Atlanta, Georgia 30303, USA    S. Sato Advanced Science Research Center, Japan Atomic Energy Agency, 2-4 Shirakata Shirane, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195, Japan    B. Schaefer Vanderbilt University, Nashville, Tennessee 37235, USA    B.K. Schmoll University of Tennessee, Knoxville, Tennessee 37996, USA    K. Sedgwick University of California-Riverside, Riverside, California 92521, USA    R. Seidl RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    A. Sen Iowa State University, Ames, Iowa 50011, USA University of Tennessee, Knoxville, Tennessee 37996, USA    R. Seto University of California-Riverside, Riverside, California 92521, USA    A. Sexton University of Maryland, College Park, Maryland 20742, USA    D. Sharma Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    I. Shein IHEP Protvino, State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, 142281, Russia    T.-A. Shibata RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan Department of Physics, Tokyo Institute of Technology, Oh-okayama, Meguro, Tokyo 152-8551, Japan    K. Shigaki Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, Japan    M. Shimomura Iowa State University, Ames, Iowa 50011, USA Nara Women’s University, Kita-uoya Nishi-machi Nara 630-8506, Japan    T. Shioya Tomonaga Center for the History of the Universe, University of Tsukuba, Tsukuba, Ibaraki 305, Japan    P. Shukla Bhabha Atomic Research Centre, Bombay 400 085, India    A. Sickles University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA    C.L. Silva Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA    D. Silvermyr Department of Physics, Lund University, Box 118, SE-221 00 Lund, Sweden    B.K. Singh Department of Physics, Banaras Hindu University, Varanasi 221005, India    C.P. Singh Department of Physics, Banaras Hindu University, Varanasi 221005, India    V. Singh Department of Physics, Banaras Hindu University, Varanasi 221005, India    M.J. Skoby Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040, USA    M. Slunečka Charles University, Ovocný trh 5, Praha 1, 116 36, Prague, Czech Republic    M. Snowball Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA    R.A. Soltz Lawrence Livermore National Laboratory, Livermore, California 94550, USA    W.E. Sondheim Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA    S.P. Sorensen University of Tennessee, Knoxville, Tennessee 37996, USA    I.V. Sourikova Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    P.W. Stankus Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA    S.P. Stoll Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    T. Sugitate Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, Japan    A. Sukhanov Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    T. Sumita RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan    J. Sun Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    Z. Sun Debrecen University, H-4010 Debrecen, Egyetem tér 1, Hungary    S. Suzuki Nara Women’s University, Kita-uoya Nishi-machi Nara 630-8506, Japan    J. Sziklai Institute for Particle and Nuclear Physics, Wigner Research Centre for Physics, Hungarian Academy of Sciences (Wigner RCP, RMKI) H-1525 Budapest 114, POBox 49, Budapest, Hungary    K. Tanida Advanced Science Research Center, Japan Atomic Energy Agency, 2-4 Shirakata Shirane, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195, Japan RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973-5000, USA Department of Physics and Astronomy, Seoul National University, Seoul 151-742, Korea    M.J. Tannenbaum Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    S. Tarafdar Vanderbilt University, Nashville, Tennessee 37235, USA Weizmann Institute, Rehovot 76100, Israel    A. Taranenko National Research Nuclear University, MEPhI, Moscow Engineering Physics Institute, Moscow, 115409, Russia    G. Tarnai Debrecen University, H-4010 Debrecen, Egyetem tér 1, Hungary    R. Tieulent Georgia State University, Atlanta, Georgia 30303, USA IPNL, CNRS/IN2P3, Univ Lyon, Université Lyon 1, F-69622, Villeurbanne, France    A. Timilsina Iowa State University, Ames, Iowa 50011, USA    T. Todoroki RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973-5000, USA Tomonaga Center for the History of the Universe, University of Tsukuba, Tsukuba, Ibaraki 305, Japan    M. Tomášek Czech Technical University, Zikova 4, 166 36 Prague 6, Czech Republic    C.L. Towell Abilene Christian University, Abilene, Texas 79699, USA    R.S. Towell Abilene Christian University, Abilene, Texas 79699, USA    I. Tserruya Weizmann Institute, Rehovot 76100, Israel    Y. Ueda Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, Japan    B. Ujvari Debrecen University, H-4010 Debrecen, Egyetem tér 1, Hungary    H.W. van Hecke Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA    J. Velkovska Vanderbilt University, Nashville, Tennessee 37235, USA    M. Virius Czech Technical University, Zikova 4, 166 36 Prague 6, Czech Republic    V. Vrba Czech Technical University, Zikova 4, 166 36 Prague 6, Czech Republic Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8, Czech Republic    N. Vukman Department of Physics, Faculty of Science, University of Zagreb, Bijenička c. 32 HR-10002 Zagreb, Croatia    X.R. Wang New Mexico State University, Las Cruces, New Mexico 88003, USA RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    Z. Wang Baruch College, City University of New York, New York, New York, 10010 USA    Y.S. Watanabe Center for Nuclear Study, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan    C.P. Wong Georgia State University, Atlanta, Georgia 30303, USA    C.L. Woody Physics Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    C. Xu New Mexico State University, Las Cruces, New Mexico 88003, USA    Q. Xu Vanderbilt University, Nashville, Tennessee 37235, USA    L. Xue Georgia State University, Atlanta, Georgia 30303, USA    S. Yalcin Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    Y.L. Yamaguchi RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973-5000, USA Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794-3800, USA    H. Yamamoto Tomonaga Center for the History of the Universe, University of Tsukuba, Tsukuba, Ibaraki 305, Japan    A. Yanovich IHEP Protvino, State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, 142281, Russia    J.H. Yoo Korea University, Seoul, 136-701, Korea RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    I. Yoon Department of Physics and Astronomy, Seoul National University, Seoul 151-742, Korea    H. Yu New Mexico State University, Las Cruces, New Mexico 88003, USA Peking University, Beijing 100871, People’s Republic of China    I.E. Yushmanov National Research Center “Kurchatov Institute”, Moscow, 123098 Russia    W.A. Zajc Columbia University, New York, New York 10027 and Nevis Laboratories, Irvington, New York 10533, USA    A. Zelenski Collider-Accelerator Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA    S. Zharko Saint Petersburg State Polytechnic University, St. Petersburg, 195251 Russia    L. Zou University of California-Riverside, Riverside, California 92521, USA
August 27, 2019
Abstract

The PHENIX collaboration has measured high- dihadron correlations in , Al, and Au collisions at GeV. The correlations arise from inter- and intra-jet correlations and thus have sensitivity to nonperturbative effects in both the initial and final states. The distributions of , the momentum component of the associated hadron perpendicular to the trigger hadron, are sensitive to initial and final state transverse momenta. These distributions are measured multi-differentially as a function of , the longitudinal momentum fraction of the associated hadron with respect to the trigger hadron. The near-side momentum widths, sensitive to fragmentation transverse momentum, show no significant broadening between Au, Al, and . The away-side nonperturbative momentum widths are found to be broadened in Au when compared to ; however, there is no significant broadening in Al compared to collisions. The data also suggest that the away-side transverse momentum broadening is a function of , the number of binary nucleon-nucleon collisions, in the interaction. The potential implications of these results with regard to transverse momentum broadening and energy loss of partons in a nucleus, among other nuclear effects, are discussed.

PHENIX Collaboration

I Introduction

High energy collisions of protons with nuclei provide a testing ground for quantum chromodynamics (QCD). In particular, when large transverse momentum scales are involved, the collisions can probe the quark and gluon, collectively referred to as partons, structure of the nucleus. Proton-nucleus (A) collisions have traditionally been used as a control to identify final-state nuclear effects in high energy nucleus-nucleus collisions where a strongly interacting quark-gluon plasma (QGP) is formed Adcox et al. (2005). However, measurements in A collisions have revealed many surprising results that have yet to be completely reconciled with each other; these have shown that understanding and explaining many different “cold” nuclear matter effects is already a challenging endeavor Hen et al. (2017); Chatrchyan et al. (2013); Cronin et al. (1975); Adcox et al. (2002).

For example, in the initial-state, nuclei are known to be more complex than just a simple linear superposition of nucleons (see e.g. Ref. Hen et al. (2017) for a review). Nuclear parton distribution functions (PDFs) are known to have several regions where they deviate from simple superpositions of nucleon PDFs as a function of the longitudinal momentum fraction that the parton carries of the nucleon. Understanding how the partonic degrees of freedom lead to nuclear structure will be a major achievement of QCD; however, there is still significant effort required in understanding the physical origin of these measured nuclear modifications. Final-state hadronization from a nucleus can also be modified similarly to nuclear PDFs in the initial state. In particular, semi-inclusive deep-inelastic scattering (SIDIS) experiments have shown that high hadrons are suppressed in electron-nucleus relative to electron-deuterium collisions Airapetian et al. (2003), where is the longitudinal momentum fraction of the outgoing hadron with respect to the fragmenting parton. This suppression was found to be dependent on the nuclear target size Airapetian et al. (2007). In addition, a particle species dependence was observed, which may reflect differences in the nuclear modification of quark and/or antiquark fragmentation functions and possible differences in meson versus baryon production from nuclei Airapetian et al. (2003, 2007).

Several proposed signatures of the QGP have also been measured in A collisions where the overall system size created in the collision was once expected to be too small. Collective behavior has been observed across large pseudorapidity ranges in high multiplicity A collisions Chatrchyan et al. (2013); Aad et al. (2013); Aidala et al. (2017, 2018). Additionally, the enhancement of strangeness in hadron production in high multiplicity A collisions has recently been measured Adam et al. (2016). Surprisingly, both of these phenomena have also been observed in high multiplicity collisions Aad et al. (2016a); Adam et al. (2017). However, the suppression of high inclusive hadrons or jets in A collisions with respect to collisions has not been measured Adler et al. (2003a); Aad et al. (2015). These results were first used to establish final-state QGP interactions as the cause of high hadron suppression in nucleus-nucleus collisions Adcox et al. (2002); Chatrchyan et al. (2011). However, the recent addition of collective and strange hadron measurements but lack of hadron suppression in A collisions has complicated the idea that a QGP may be formed in smaller collision systems.

Another unexpected physical effect in A collisions is the so-called “Cronin” effect, which refers to an enhancement in the inclusive hadron spectrum with respect to collisions at moderate of approximately GeV/ which persists over a wide range of center-of-mass energies Cronin et al. (1975); Adler et al. (2003a); Aad et al. (2016b). This effect has also been observed at moderate in electron-nucleus collisions Airapetian et al. (2003), where a significant dependence of the enhancement on the longitudinal momentum fraction of the hadron was found Airapetian et al. (2007). While this was first proposed to be due to multiple scattering effects in the nuclear medium, more recent measurements have shown that hadronization also plays a role Adare et al. (2013). Additional measurements that go beyond single inclusive hadrons may be able to shed further light on this phenomenon in A collisions. For example, dijet measurements in the kinematic regime of the Cronin effect have shown that the initial-state partonic transverse momentum is a function of the nucleus size Corcoran et al. (1991), which has not been observed at large jet transverse momentum Adam et al. (2015).

The lack of understanding of the underlying physical sources of these phenomena motivates measurements in new kinematic regimes with different observables. Here we present a measurement of dihadron angular correlations in , Al, and Au collisions at midrapidity collected by the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC). The unique capabilities of RHIC allow for a nuclear size dependence to be studied in = 200 GeV A collisions. High two-particle angular correlations have been theoretically considered as a probe for energy loss in A and A+A collisions via their transverse momentum broadening Baier et al. (1997, 2000); Tannenbaum (2017); however, the various aforementioned effects should also be considered as they will play a role in both collision systems. The present measurements will contribute to our understanding of the rich phenomena in hadronic interactions involving nuclei.

Ii Methods

In 2015, the PHENIX experiment Adcox et al. (2003a) at RHIC collected data from , Al, and Au collisions at  GeV. A total minimum bias integrated luminosity of 60, 0.69, and 0.21 pb for , Al, and Au, respectively, was used for the analysis of dihadron correlations. From these total integrated luminosities, data quality assurance and collision vertex position cm cuts were applied. The PHENIX detector measures two-particle angular correlations of neutral pions and charged hadrons, -h, with its electromagnetic calorimeter (EMCal) and drift chamber (DC) and pad chamber (PC) tracking system. These central arms cover an azimuthal range of   radians and a pseudorapidity range of . Detailed descriptions of the PHENIX central arms can be found in Refs. Adcox et al. (2003b); Aphecetche et al. (2003). In A collisions, the centrality class is determined with the forward beam-beam counters (BBCs) Ikematsu et al. (1998), where the centrality percentiles are defined by the multiplicity measured in the nucleus-going BBC following the procedure in Ref. Adare et al. (2014).

The EMCal is used to identify high neutral pions to construct the correlation functions. A high-energy-photon trigger is used to identify events with a high photon from a decay. Photons are identified using a shower shape cut that removes charged hadrons as well as most high energy clusters that overlap with another photon. The neutral pions are reconstructed via their two photon decay, where the granularity of the EMCal allows reconstruction up to approximately 20 GeV in this channel. In this analysis neutral pions are collected in the range GeV/.

The DC and PC tracking system measures nonidentified charged hadrons in the event with the triggered high photon. Two PCs, located radially behind the DC, are used to identify and match tracks in the DC with hits in the PCs. This track matching condition reduces background from secondary tracks due to conversions or decays. A ring-imaging erenkov system is also used to reject electrons from the charged hadron sample. With these conditions, the DC and PC tracking system is also used to reject tracks in the EMCal that happen to shower and are thus background for the identification. Nonidentified charged hadrons are collected between GeV/ in correlation with the high .

The correlations are constructed similarly to previous PHENIX two-particle correlation analyses, see e.g. Refs. Adler et al. (2006); Adare et al. (2010); Aidala et al. . Per-trigger yields are constructed for a given observable, such as , which show the yield of charged hadrons per-trigger and are defined by

(1)

To account for the PHENIX acceptance, the raw correlations are divided by a mixed-event background correlation function, . The background correlation is constructed with neutral pions and charged hadrons from the same data taking period but different event number; the events are required to have a similar centrality and z-vertex. To account for the efficiency of the PHENIX detector, the correlation functions are also corrected by a charged hadron efficiency defined as in Eq. 1, which is determined with a single particle Monte Carlo generator as well as a full GEANT description of the PHENIX apparatus Adler et al. (2003b). After these corrections, the correlations are normalized by the total number of trigger particles measured to construct the per-trigger yield and correspond to full azimuthal acceptance within .

Figure 1: A schematic diagram showing a dihadron correlation in the transverse plane. Vector quantities are shown in bold. The red vectors are the two partons, which are acoplanar due to initial-state partonic , while the two black vectors are the measured trigger and associated hadron, slightly displaced from the partons due to final-state from fragmentation. The quantities and are shown as blue and green vectors, respectively.

Correlation functions are typically constructed in terms of the azimuthal angle between the trigger and associated particle. Here we choose to construct the correlations as a function of the momentum space vector component and , defined as

(2)

and

(3)

The quantities and give the transverse momentum component and longitudinal momentum fraction, respectively, of the associated hadron with respect to the trigger . These quantities are schematically diagrammed in Fig. 1, where the Figure shows a two-particle correlation in the transverse plane and quantities in bold represent vectors. In this diagram, two hadrons (black vectors) fragment from two high partons (red vectors) from a two-to-two partonic scattering. The partons are originally acoplanar due to their initial-state transverse momenta (); the two hadrons may acquire additional acoplanarity due to final-state transverse momentum () during the fragmentation process. In the diagram the final-state transverse momentum is perpendicular to the parton axis and denoted as and , which are assumed to be Gaussian such that . The quantity can be nonzero because of these transverse momentum contributions, while is a proxy for the momentum fraction that the final-state hadron carries with respect to the parton. In the figure, is shown multiplied by to explicitly show the comparison between and . When is small, the two-particle correlation is nearly back-to-back and the acoplanarity is generated by nonperturbative and  Aidala et al. ; Adare et al. (2017). Additional nonperturbative interactions within the nucleus may contribute to this quantity in A collisions.

Systematic uncertainties are assigned for the charged hadron efficiency and for the underlying event background subtraction procedure. The systematic uncertainty on the charged hadron yields is determined to be an overall normalization uncertainty of 9% on the per-trigger yields. The dominant contribution is due to the uncertainty that arises from matching tracks in the PHENIX drift chamber to the outermost pad chamber; however, there are also contributions from the overall tracking resolution of the detector and the Monte Carlo determination of the nonidentified charged hadron efficiency. The underlying event background is statistically subtracted with fits to the away-side correlation functions as described in Ref. Adare et al. (2017); these fits determine the percentage of underlying event background level with respect to the jet yield. The systematic uncertainty is determined by altering the underlying event region by based on the fit results. This uncertainty varies from less than 1% at small to several percent at large where the underlying event contribution, and thus background-to-signal, is larger.

Iii Results

Examples of the away-side per-trigger yields as a function of are shown in several bins of in Fig. 2. The per-trigger yields for Au and collisions are shown as open and filled points, respectively. A transition from nonperturbative behavior in the nearly back-to-back 0 ( ) region to perturbative next-to-leading order behavior at larger can be seen at varying values of , depending on the bin. This change in shape is highlighted by Gaussian fits to the small region, drawn in Fig. 2 as dotted and solid lines for Au and , respectively. The fit ranges vary depending on the bin as the nonperturbative region is a function of and thus  Aidala et al. . The fit ranges are chosen to give the best /NDF, and a systematic uncertainty is assigned based on this choice as described later. These fits clearly do not describe the data at larger values of where the data exhibit a more power-law like behavior. This transition indicates a change from sensitivity to nonperturbative to perturbative physics effects.

Figure 2: The away-side per-trigger yields are shown in both Au and collisions for several bins of . Gaussian fits, shown as dotted lines for Au and solid lines for , are shown to the small distributions, highlighting the nonperturbative to perturbative transition.
Figure 3: The near-side per-trigger yields are shown in both Au and collisions for several bins of . Gaussian fits, shown as dotted lines for Au and solid lines for , are performed at small where nonperturbative behavior is dominant in the 0 region.

Examples of the near-side per-trigger yields as a function of are shown in several bins of in Fig. 3. The near-side per-trigger yields show a much narrower distribution than the away-side per-trigger yields due to the differences between intra-jet correlations and inter-jet correlations, respectively. In particular, the near-side correlations are only sensitive to fragmentation transverse momentum, because the and hadron are fragmented from the same hard parton. However, the away-side correlations are sensitive to both initial and final state transverse momentum. Because the initial-state is much larger than final-state (see e.g. Adler et al. (2006); Adare et al. (2010)), this leads to a broader distribution on the away-side than the near-side. Nonetheless, a nonperturbative Gaussian region can still be identified on the near side as shown in Fig. 3, similarly to the away side, with a power law spectrum at larger that is not well described by the Gaussian fit.

To measure the nonperturbative momentum widths, the Gaussian widths are extracted from the fits to both the near and away side distributions. Systematic uncertainties on the Gaussian widths are estimated by increasing the fit range by 0.2 GeV/ in and taking the absolute value of the difference of the resulting Gaussian width. To study any modification in A compared to collisions the squared width difference is determined between the A and Gaussian widths, mathematically defined as . These differences are shown in Fig. 4 as a function of for the near and away side correlation functions, for both Al and Au collisions. The near-side width differences in the left column of Fig. 4 show no significant modification within uncertainties between both Al or Au and collisions at all values of . Similar results have been seen in dihadron correlations Viinikainen (2017) and fragmentation function studies with full jet reconstruction Aaboud et al. (2018) in Pb collisions. However, the away-side width differences in Au and collisions show modification as seen in the bottom-right panel of Fig. 4. There is no significant away-side broadening between Al and collisions as seen in the top right panel of Fig. 4 within the assigned systematic uncertainties.

Figure 4: The Gaussian width differences are shown for the near-side (a) and away-side (b) between Al and collisions and for the near-side (c) and away-side (d) between Au and collisions as a function of .

There is an indication that the away-side squared Gaussian width differences depend on the nucleus size as indicated in the right column of Fig. 4. To study this further, the per-trigger yields were split into two centrality bins in the Au data and the same analysis was performed. The centrality in A collisions is converted to values of with the method in Ref. Adare et al. (2014), where is defined as the average number of nucleon-nucleon collisions in a given event class. Figure 5 shows the squared width differences in A and collisions as a function of in the two bins where a nonzero Gaussian width difference is observed. The values of these squared width differences are shown in Tab. 1. The data are fit with linear functions which are shown on the figure and indicate that the squared width differences exhibit a positive correlation with . The slopes of the fits were found to be  (stat)  (sys) and 0.015  (stat)  (sys) for the smaller and larger bins, respectively. When the data is fit to a constant of 0, the per number of degree of freedom becomes approximately 5 for and approximately 8 for . The measured slopes differ from a slope of 0 with p values of approximately 0.055 and 0.01, for the smaller and larger bin respectively, where the statistical and systematic uncertainties on the slopes were added in quadrature. This suggests that the interpretation of no transverse momentum broadening in A compared to is inconsistent with the data.

Figure 5: The Gaussian width differences between A and are shown in two bins as a function of . Linear fits are shown for each bin, which exhibit a positive dependence with .
System
Al 2.1 0.1 0.15–0.25 0.017 0.004 0.013
Au 4.4 0.6 0.15–0.25 0.016 0.004 0.034
Au 7.7 0.6 0.15–0.25 0.045 0.005 0.013
Al 2.1 0.1 0.25–0.50 0.020 0.017 0.022
Au 4.4 0.6 0.25–0.50 0.039 0.018 0.023
Au 7.7 0.6 0.25–0.50 0.105 0.022 0.016
Table 1: The values of the Gaussian width differences between A and and their statistical and systematic uncertainties are shown, corresponding to Fig. 5. Units are for the width differences and their uncertainties.

Iv Discussion

There are a number of different physical processes that could be contributing to the apparent broadening of the away-side nonperturbative momentum widths in A compared to collisions, as discussed in the Introduction. The apparent lack of broadening on the near-side indicates that additional nonperturbative radiation during fragmentation in A is small. This may suggest that the fragmentation of the hard scattered parton into hadrons occurs outside any nuclear medium that is present; therefore, this fragmentation is similar between A and collisions and is independent of the presence of a nucleus in the kinematic region probed by this data.

In the last decade, significant emphasis has been placed on the observation of collective effects in A collisions. The effects of contributions from and Fourier harmonics were studied and found to be negligible in the present analysis; this is because the Gaussian widths are almost entirely constrained by correlations in the range of radians around . In this small range, any modulation from collective dynamics was found to contribute on average less than 1% to the normalization of the correlation functions. Additionally, the correlations are collected in the midrapidity region where the between the high trigger and associated particle is small and thus the jet dynamics will be dominant. For this reason, any contribution from collective dynamics can be neglected in these results.

The modification observed in this analysis is found in a similar kinematic region to where the so-called “Cronin” peak has been observed. In the bins where the broadened widths are observed, associated hadrons corresponding to trigger neutral pions in the range GeV/ are approximately in the range GeV/. The Cronin effect was once attributed to multiple scattering of partons within a nuclear medium; however, recent measurements revealed a particle ID dependence and have shown that additional final-state effects must also be present Adare et al. (2013). Additional nonperturbative initial-state partonic can also contribute to the Cronin peak, to which this measurement is sensitive. Nonetheless, multiple scattering interactions within the nucleus could manifest themselves as collisional energy loss or elastic scatterings leading to an angular broadening, both of which could lead to the observed away-side momentum width broadening in A collisions. Two-particle correlations may provide additional constraints on the underlying physical mechanism which leads to this phenomenon. Future measurements with particle identification will play an important role in identifying the cause of the Cronin peak, as a particle species dependence has been measured in Au Adare et al. (2013) collisions.

Figure 6: The correlation between and is shown as determined in a PYTHIA simulation for -hadron correlations in the same kinematic regime as measured in the data. The correlation may provide insight into the origins of the inclusive hadron enhancement at moderate in A collisions.

In Ref. Airapetian et al. (2007) a strong dependence on to the inclusive charged hadron enhancement in collisions was found. In particular, the largest enhancement was found for hadrons. Figure 6 shows the correlation between and for -hadron correlations in = 200 GeV collisions as determined in a PYTHIA6 Sjostrand et al. simulation with the default tune. The correlations are determined in the Monte Carlo simulation in the same kinematic regime as the data to draw a better comparison between and to this analysis. Figure 6 shows that , where the transverse momentum broadening is observed to be the largest, corresponds approximately to a range of covering . This is in a similar region to where Ref. Airapetian et al. (2007) sees the largest inclusive hadron enhancement in collisions. However, it should also be considered that the two measurements cover a much different range, which may also be relevant in this comparison.

Nuclear PDFs can also play a role; in particular the nuclear PDFs are known to vary with the longitudinal momentum fraction of the parton probed Geesaman et al. (1995); Hen et al. (2017). These measurements are in a kinematic region that may be sensitive to the anti-shadowing region around 0.1. The correlation functions are also sensitive to a small transverse momentum scale, and thus can also probe the transverse-momentum-dependent parton distribution functions of the nucleus. Dijet measurements, where the jets have an average GeV/, have shown that there is a larger acoplanarity in A compared to collisions Corcoran et al. (1991), indicating that there is a nuclear size dependence to initial-state partonic transverse momentum in the kinematic regime where Cronin effects may be expected to be relevant. However, the observation from the present measurement that the broadening depends on could indicate that the broadening is not simply due to additional transverse momentum from the nucleus size.

The transverse momentum broadening may also be due to soft radiative energy loss within the nucleus. Energy loss in cold nuclear matter has been previously studied with the Drell-Yan process Vasilev et al. (1999). Transverse momentum broadening has also been measured to be nonzero in SIDIS interactions Airapetian et al. (2010). While the Drell-Yan measurement is only sensitive to initial-state partonic energy loss, the SIDIS measurement and the measurement presented here are sensitive to both initial and final state energy loss. Global analyses which utilize all of these data may provide further insight into the origins of the measured transverse momentum broadening in nuclear Drell-Yan, SIDIS, and A  dihadrons processes. The difference in between A+A and collisions has been used to estimate the energy loss per unit length within the QGP in AuAu collisions Tannenbaum (2017). Given that there is an observed difference in the widths between A and collisions this indicates that small energy losses have been measured in these dihadron correlations. Calculations for energy loss in a nucleus have been performed for both RHIC and Large-Hadron-Collider energies in the dijet and direct photon-hadron channel as well as in collisions Xing et al. (2012).

V Conclusion

In summary, high dihadron correlations have been measured in  GeV , Al, and Au collisions. The distributions are measured on the near and away side of the trigger hadron and the distributions are fit with Gaussian functions to extract the nonperturbative transverse momentum width in each system. The widths are compared across the various collision systems to search for modifications present in the nuclear collisions. No near-side modification is observed within uncertainties in the A collisions, indicating that intra-jet radiation effects from nuclei are small in these systems. In contrast, the away-side widths are broadened in Au compared to at moderate values of , while no significant modification was observed in Al compared to . This was observed to be a function of the centrality or of the A collision, which suggests a path length dependence to the transverse momentum broadening.

A number of different physical effects may contribute to the measured transverse momentum broadening in A collisions. In particular, contributions from long range correlations were systematically studied and found to be small. The correlations are constructed in a kinematic regime where “Cronin” effects are known to be large; therefore, multiple initial-state scatterings or parton recombination effects in the final state may be contributing to the broadening. The correlations are also sensitive to the partonic initial-state transverse momentum, and thus may indicate additional primordial partonic in nuclei when compared to a free nucleon. However, the dependence of the broadening on suggests a path length dependence to hard scattered partonic energy loss, which may be due to radiative or elastic interactions with the nuclear remnants. Considering these different qualitative physics mechanisms, and the many different processes and/or observables with which they have been measured, will be an important endeavor in understanding hadronic interactions involving nuclei. Future measurements, especially at an electron-ion collider, will continue to shed light on the many physical phenomena that occur in proton-nucleus collisions.

Acknowledgements.
We thank the staff of the Collider-Accelerator and Physics Departments at Brookhaven National Laboratory and the staff of the other PHENIX participating institutions for their vital contributions. We acknowledge support from the Office of Nuclear Physics in the Office of Science of the Department of Energy, the National Science Foundation, Abilene Christian University Research Council, Research Foundation of SUNY, and Dean of the College of Arts and Sciences, Vanderbilt University (U.S.A), Ministry of Education, Culture, Sports, Science, and Technology and the Japan Society for the Promotion of Science (Japan), Conselho Nacional de Desenvolvimento Científico e Tecnológico and Fundação de Amparo à Pesquisa do Estado de São Paulo (Brazil), Natural Science Foundation of China (People’s Republic of China), Croatian Science Foundation and Ministry of Science and Education (Croatia), Ministry of Education, Youth and Sports (Czech Republic), Centre National de la Recherche Scientifique, Commissariat à l’Énergie Atomique, and Institut National de Physique Nucléaire et de Physique des Particules (France), Bundesministerium für Bildung und Forschung, Deutscher Akademischer Austausch Dienst, and Alexander von Humboldt Stiftung (Germany), J. Bolyai Research Scholarship, EFOP, the New National Excellence Program (ÚNKP), NKFIH, and OTKA (Hungary), Department of Atomic Energy and Department of Science and Technology (India), Israel Science Foundation (Israel), Basic Science Research Program through NRF of the Ministry of Education (Korea), Physics Department, Lahore University of Management Sciences (Pakistan), Ministry of Education and Science, Russian Academy of Sciences, Federal Agency of Atomic Energy (Russia), VR and Wallenberg Foundation (Sweden), the U.S. Civilian Research and Development Foundation for the Independent States of the Former Soviet Union, the Hungarian American Enterprise Scholarship Fund, the US-Hungarian Fulbright Foundation, and the US-Israel Binational Science Foundation.

References

  • Adcox et al. (2005) K. Adcox et al. (PHENIX Collaboration), “Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration,” Nucl. Phys. A 757, 184 (2005).
  • Hen et al. (2017) O. Hen, G. A. Miller, E. Piasetzky,  and L. B. Weinstein, “Nucleon-Nucleon Correlations, Short-lived Excitations, and the Quarks Within,” Rev. Mod. Phys. 89, 045002 (2017).
  • Chatrchyan et al. (2013) S. Chatrchyan et al. (CMS Collaboration), “Observation of long-range near-side angular correlations in proton-lead collisions at the LHC,” Phys. Lett. B 718, 795 (2013).
  • Cronin et al. (1975) J. W. Cronin, H. J. Frisch, M. J. Shochet, J. P. Boymond, R. Mermod, P. A. Piroue,  and R. L. Sumner, ‘‘Production of hadrons with large transverse momentum at 200, 300, and 400 GeV,” Phys. Rev. D 11, 3105–3123 (1975).
  • Adcox et al. (2002) K. Adcox et al. (PHENIX Collaboration), “Suppression of hadrons with large transverse momentum in central Au+Au collisions at = 130-GeV,” Phys. Rev. Lett. 88, 022301 (2002).
  • Airapetian et al. (2003) A. Airapetian et al. (HERMES Collaboration), ‘‘Quark fragmentation to , , , and anti- in the nuclear environment,” Phys. Lett. B 577, 37 (2003).
  • Airapetian et al. (2007) A. Airapetian et al. (HERMES Collaboration), “Hadronization in semi-inclusive deep-inelastic scattering on nuclei,” Nucl. Phys. B 780, 1 (2007).
  • Aad et al. (2013) G. Aad et al. (ATLAS Collaboration), “Observation of Associated Near-Side and Away-Side Long-Range Correlations in =5.02 TeV Proton-Lead Collisions with the ATLAS Detector,” Phys. Rev. Lett. 110, 182302 (2013).
  • Aidala et al. (2017) C. Aidala et al. (PHENIX Collaboration), “Measurement of long-range angular correlations and azimuthal anisotropies in high-multiplicity Au collisions at GeV,” Phys. Rev. C 95, 034910 (2017).
  • Aidala et al. (2018) C. Aidala et al. (PHENIX Collaboration), “Measurements of Multiparticle Correlations in Collisions at 200, 62.4, 39, and 19.6 GeV and Collisions at 200 GeV and Implications for Collective Behavior,” Phys. Rev. Lett. 120, 062302 (2018).
  • Adam et al. (2016) J. Adam et al. (ALICE Collaboration), “Multi-strange baryon production in p-Pb collisions at TeV,” Phys. Lett. B 758, 389 (2016).
  • Aad et al. (2016a) G. Aad et al. (ATLAS Collaboration), “Observation of Long-Range Elliptic Azimuthal Anisotropies in 13 and 2.76 TeV Collisions with the ATLAS Detector,” Phys. Rev. Lett. 116, 172301 (2016a).
  • Adam et al. (2017) J. Adam et al. (ALICE Collaboration), “Enhanced production of multi-strange hadrons in high-multiplicity proton-proton collisions,” Nature Phys. 13, 535 (2017).
  • Adler et al. (2003a) S. S. Adler et al. (PHENIX Collaboration), “Absence of suppression in particle production at large transverse momentum in = 200 GeV +Au collisions,” Phys. Rev. Lett. 91, 072303 (2003a).
  • Aad et al. (2015) G. Aad et al. (ATLAS Collaboration), “Centrality and rapidity dependence of inclusive jet production in TeV proton-lead collisions with the ATLAS detector,” Phys. Lett. B 748, 392 (2015).
  • Chatrchyan et al. (2011) S. Chatrchyan et al. (CMS Collaboration), “Observation and studies of jet quenching in PbPb collisions at nucleon-nucleon center-of-mass energy = 2.76 TeV,” Phys. Rev. C 84, 024906 (2011).
  • Aad et al. (2016b) G. Aad et al. (ATLAS Collaboration), “Transverse momentum, rapidity, and centrality dependence of inclusive charged-particle production in TeV +Pb collisions measured by the ATLAS experiment,” Phys. Lett. B 763, 313 (2016b).
  • Adare et al. (2013) A. Adare et al. (PHENIX Collaboration), “Spectra and ratios of identified particles in Au+Au and +Au collisions at GeV,” Phys. Rev. C 88, 024906 (2013).
  • Corcoran et al. (1991) M. D. Corcoran et al. (E609 Collaboration), “Evidence for multiple scattering of high-energy partons in nuclei,” Phys. Lett. B 259, 209 (1991).
  • Adam et al. (2015) J. Adam et al. (ALICE Collaboration), “Measurement of dijet in p–Pb collisions at =5.02 TeV,” Phys. Lett. B 746, 385 (2015).
  • Baier et al. (1997) R. Baier, Y. L. Dokshitzer, A. H. Mueller, S. Peigne,  and D. Schiff, “Radiative energy loss and broadening of high-energy partons in nuclei,” Nucl. Phys. B 484, 265 (1997).
  • Baier et al. (2000) R. Baier, D. Schiff,  and B. G. Zakharov, “Energy loss in perturbative QCD,” Ann. Rev. Nucl. Part. Sci. 50, 37 (2000).
  • Tannenbaum (2017) M. J. Tannenbaum, ‘‘Measurement of in relativistic heavy ion collisions using di-hadron correlations,” Phys. Lett. B 771, 553 (2017).
  • Adcox et al. (2003a) K. Adcox et al. (PHENIX Collaboration), “PHENIX detector overview,” Nucl. Instrum. Methods Phys. Res., Sec. A 499, 469 (2003a).
  • Adcox et al. (2003b) K. Adcox et al. (PHENIX Collaboration), “PHENIX central arm tracking detectors,” Nucl. Instrum. Methods Phys. Res., Sec. A 499, 489 (2003b).
  • Aphecetche et al. (2003) L. Aphecetche et al. (PHENIX Collaboration), “PHENIX calorimeter,” Nucl. Instrum. Methods Phys. Res., Sec. A 499, 521 (2003).
  • Ikematsu et al. (1998) K. Ikematsu et al., “A Start- timing detector for the collider experiment PHENIX at RHIC-BNL,” Nucl. Instrum. Methods Phys. Res., Sec. A 411, 238 (1998).
  • Adare et al. (2014) A. Adare et al. (PHENIX Collaboration), “Centrality categorization for in high-energy collisions,” Phys. Rev. C 90, 034902 (2014).
  • Adler et al. (2006) S. S. Adler et al. (PHENIX Collaboration), “Jet properties from dihadron correlations in collisions at = 200 GeV,” Phys. Rev. D 74, 072002 (2006).
  • Adare et al. (2010) A. Adare et al. (PHENIX Collaboration), “High direct photon and triggered azimuthal jet correlations and measurement of for isolated direct photons in + collisions at GeV,” Phys. Rev. D 82, 072001 (2010).
  • (31) C. Aidala et al. (PHENIX Collaboration), “Nonperturbative transverse-momentum-dependent effects in dihadron and direct photon-hadron angular correlations in + collisions at GeV,” arXiv:1805.02450 [submitted to Phys. Rev. D].
  • Adler et al. (2003b) S. S. Adler et al. (PHENIX Collaboration), “PHENIX on-line and off-line computing,” Nucl. Instrum. Methods Phys. Res., Sec. A 499, 593 (2003b).
  • Adare et al. (2017) A. Adare et al. (PHENIX Collaboration), “Nonperturbative-transverse-momentum effects and evolution in dihadron and direct photon-hadron angular correlations in collisions at =510 GeV,” Phys. Rev. D 95, 072002 (2017).
  • Viinikainen (2017) J. Viinikainen (ALICE Collaboration), ‘‘Jet transverse fragmentation momentum from h–h correlations in pp and p–Pb collisions,” Proceedings, 8th International Conference on Hard and Electromagnetic Probes of High-energy Nuclear Collisions: Hard Probes 2016 (HP2016): Wuhan, Hubei, China, September 23-27, 2016Nucl. Part. Phys. Proc. 289-290, 293 (2017).
  • Aaboud et al. (2018) M. Aaboud et al. (ATLAS Collaboration), “Measurement of jet fragmentation in 5.02 TeV proton-lead and proton-proton collisions with the ATLAS detector,” Nucl. Phys. A 978, 65 (2018).
  • (36) T. Sjostrand, S. Mrenna,  and P. Z. Skands, “PYTHIA 6.4 Physics and Manual,” J. High Energy Phys. 05 (2006) 026.
  • Geesaman et al. (1995) D. F. Geesaman, K. Saito,  and A. W. Thomas, “The nuclear EMC effect,” Ann. Rev. Nucl. Part. Sci. 45, 337–390 (1995).
  • Vasilev et al. (1999) M. A. Vasilev et al. (NuSea Collaboration), “Parton energy loss limits and shadowing in Drell-Yan dimuon production,” Phys. Rev. Lett. 83, 2304 (1999).
  • Airapetian et al. (2010) A. Airapetian et al. (HERMES Collaboration), “Transverse momentum broadening of hadrons produced in semi-inclusive deep-inelastic scattering on nuclei,” Phys. Lett. B 684, 114 (2010).
  • Xing et al. (2012) H. Xing, Z.-B. Kang, I. Vitev,  and E. Wang, ‘‘Transverse momentum imbalance of back-to-back particle production in p+A and e+A collisions,” Phys. Rev. D 86, 094010 (2012).
Comments 0
Request Comment
You are adding the first comment!
How to quickly get a good reply:
  • Give credit where it’s due by listing out the positive aspects of a paper before getting into which changes should be made.
  • Be specific in your critique, and provide supporting evidence with appropriate references to substantiate general statements.
  • Your comment should inspire ideas to flow and help the author improves the paper.

The better we are at sharing our knowledge with each other, the faster we move forward.
""
The feedback must be of minimum 40 characters and the title a minimum of 5 characters
   
Add comment
Cancel
Loading ...
304880
This is a comment super asjknd jkasnjk adsnkj
Upvote
Downvote
""
The feedback must be of minumum 40 characters
The feedback must be of minumum 40 characters
Submit
Cancel

You are asking your first question!
How to quickly get a good answer:
  • Keep your question short and to the point
  • Check for grammar or spelling errors.
  • Phrase it like a question
Test
Test description