Experimental Group

Leader's Picture
Group Leader
Yasuyuki AKIBAD.Sci.
  • 1987年日本学術振興会特別研究員(DC)
  • 1988年東京大学原子核研究所・助手
  • 1997年高エネルギー加速器研究機構素粒子原子核研究所・助手
  • 2003年理化学研究所・副主任研究員
  • 2004年米国ブルックヘブン国立研究所(BNL)RHIC 加速器・PHENIX 実験の副実験 代表者
  • 2008年理化学研究所仁科加速器研究センター・副主任研究員
    兼 理研BNL 研究センター実験研究グループリーダー

Research Areas

RIKEN BNL Research Center (RBRC) Experimental Group studies the strong interactions (QCD) using RHIC accelerator at Brookhaven National Laboratory, the world first heavy ion collider and polarized p+p collider. We have three major activities: Spin Physics at RHIC, Heavy ion physics at RHIC, and detector upgrades of PHENIX experiment at RHIC. We study the spin structure of the proton using the polarized proton-proton collisions at RHIC. This program has been promoted by RIKEN's leadership. The first focus of the research is to measure the gluon spin contribution to the proton spin. Our recent data analysis has shown that the proton spin carried by the gluons is small, which is a very striking finding beyond our expectations. The aim of Heavy ion physics at RHIC is to re-create Quark Gluon Plasma, the state of Universe just after the Big Bang. Two important discoveries, jet quenching effect and strong elliptic flows, have established that new state of dense matter is indeed produced in heavy ion collisions at RHIC.We are proceeding to understand the nature of the matter. Recently, we have measured direct photons in Au+Au collisions for 1<pT<3 GeV/c , where thermal radiation from hot QGP is expected to dominate. The comparison between the data and theory calculations indicates that the initial temperature of 300 MeV to 600 MeV is achieved. These values are well above the transition temperature to QGP, which is calculated to be approximately 170 MeV by lattice QCD calculations. We has major roles in detector upgrades of PHENIX experiment. We have completed a silicon vertex tracker (VTX) and installed it in PHENIX in 2010.With this new detector we can measure produciton of heavy quarks (charm and bottom) in pp and AA collisions. We also have leading role in construction and operaton of the new muon trigger system to measure W-bosons at RHIC.

Research Subject

  1. Experimental Studies of the Spin Structure of the Nucleon
  2. Study of Quark-Gluon Plasma at RHIC
  3. Detector upgrade of PHENIX experiment at RHIC

List of Selected Publications

  1. PHENIX Collaboration (A. Adare et al.):
    "Inclusive cross section and double-helicity asymmetry for pi0 production at midrapidity in p+p collisions at sqrt(s)=510 GeV"
    Phys. Rev. D93, 011501 (2016)
  2. PHENIX Collaboration (A. Adare et al.):
    "Observation of direct-photon collective flow in sqrt(s_NN)=200 GeV Au+Au collisions"
    Phys. Rev. Lett. 109, 122302 (2012)
  3. PHENIX Collaboration (A. Adare et al.):
    "Cross Section and Parity-Violating Spin Asymmetries of W Boson Production in polarized p+p Collisions at sqrt(s)=500 GeV"
    Phys. Rev. Lett. 106, 062001 (2011)
  4. PHENIX Collaboration (A. Adare et al.):
    "Enhanced Production of Direct Photons in Au+Au Collisions at sqrt(s_NN)=200 GeV and Implications for the Initial Temperature"
    Phys. Rev. Lett. 104, 132301 (2010)
  5. PHENIX Collaboration (Stephen Scott Adler et al.):
    "Measurement of direct photon production in p + p collisions at s**(1/2) = 200-GeV."
    Phys.Rev.Lett.98:012002 (2007)
  6. PHENIX Collaboration (A. Adare et al.):
    "J/psi Production vs Centrality, Transverse Momentum, and Rapidity in Au+Au Collisions at s(NN)**(1/2) = 200-GeV."
    Phys.Rev.Lett.98:232301 (2007)
  7. PHENIX Collaboration (A. Adare et al.):
    "Energy Loss and Flow of Heavy Quarks in Au+Au Collisions at s(NN)**(1/2) = 200-GeV"
    Phys.Rev.Lett.98:172301 (2007)
  8. PHENIX Collaboration (Adcox, K. et al.):
    "Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration"
    Nucl.Phys., A757, 184-283 (2005).
  9. PHENIX Collaboration (Adler, al.):
    "Midrapidity Neutral Pion Production in Proton-Proton Collisions at s**(1/2)=200 GeV"
    Phys.Rev.Lett., 91, 241803 (2003).
  10. PHENIX Collaboration (Adcox, K. et al.):
    "Suppression of hadrons with large transverse momentum in central Au+Au collisions at s(NN)**(1/2) = 130-GeV"
    Phys.Rev.Lett., 88, 022301 (2002).