Experimental Group
Group Leader: Yasuyuki AKIBA (D.Sci.)
Research Areas
| The RIKEN BNL Research Center (RBRC), Experiment Group studies the internal spin structure of the proton, using the first polarized proton collider at Brookhaven, RHIC, which has been promoted with RIKEN's leadership. The group leads and participates in three general areas: developing the world's highest energy polarized proton beams, developing probes of the proton's spin content, and seeking a global understanding of all proton spin data. For the proton beam, the group has developed two new methods to measuring the proton beam polarization at high energy, one using proton-Carbon Coulomb Nuclear Interference and the other using very forward neutron asymmetry discovered by our own. Recent data analysis has shown that the proton spin carried by gluons is indeed small, which is a very striking finding beyond our expectations. With collaboration with the BELLE experiment at High Energy Accelerator Research Organization (KEK), we have discovered that quark fragments can determine the spin direction of the mother quark. RHIC stands for Relativistic Heavy Ion Collider, aiming also to create Quark Gluon Plasma, the state of Universe just after the Big Bang. Until now, jet quenching effect and elliptic flows of produced particles are discovered, which have proven that the new state of dense matter is indeed created. We are proceeding to understand the nature of this matter. |
Research Subjects
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List of Selected Publications
| (1) | PHENIX Collaboration (A. Adare et al.): " Inclusive cross-section and double helicity asymmetry for pi0 production in p + p collisions at s**(1/2) = 200-GeV: Implications for the polarized gluon distribution in the proton." Phys.Rev.D76:051106 (2007). |
| (2) | Bazilevsky, A., et al.: " Single Transverse-Spin Asymmetry in Very Forward and Very Backward Neutral Particle Production for Polarized Proton Collisions at s**(1/2) = 200-GeV." Phys.Lett.B650:325-330 (2007). |
| (3) | 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). |
| (4) | PHENIX Collaboration (A. Adare et al.): " 3. 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). |
| (5) | 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). |
| (6) | PHENIX Collaboration (Adler, S.S. et al.): " Measurement of transverse single-spin asymmetries for mid-rapidity production of neutral pions and charged hadrons in polarized p+p collisions at s**(1/2) = 200-GeV." Phys.Rev.Lett., 95, 202001 (2005). |
| (7) | 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). |
| (8) | PHENIX Collaboration (Adler, S.S. et al.): " Double helicity asymmetry in inclusive mid-rapidity pi0 production for polarized p + p collisions at s**(1/2) = 200-GeV." Phys.Rev.Lett., 93, 202002 (2004). |
| (9) | PHENIX Collaboration (Adler, S.S.et al.): " Elliptic flow of identified hadrons in Au+Au collisions at s(NN)**(1/2) = 200-GeV." Phys.Rev.Lett., 91, 182301 (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). |