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System size dependence of associated yields in hadron-triggered jets
STAR Collaboration,Abelev, B.I.,Aggarwal, M.M.,Ahammed, Z.,Anderson, B.D.,Arkhipkin, D.,Averichev, G.S.,Balewski, J.,Barannikova, O.,Barnby, L.S.,Baudot, J.,Baumgart, S.,Beavis, D.R.,Bellwied, R.,Bene North-Holland Pub. Co 2010 Physics letters: B Vol.683 No.2
We present results on the system size dependence of high transverse momentum di-hadron correlations at s<SUB>NN</SUB>=200 GeV as measured by STAR at RHIC. Measurements in d+Au, Cu+Cu and Au+Au collisions reveal similar jet-like near-side correlation yields (correlations at small angular separation -Δφ∼0, Δη∼0) for all systems and centralities. Previous measurements have shown that the away-side (Δφ∼π) yield is suppressed in heavy-ion collisions. We present measurements of the away-side suppression as a function of transverse momentum and centrality in Cu+Cu and Au+Au collisions. The suppression is found to be similar in Cu+Cu and Au+Au collisions at a similar number of participants. The results are compared to theoretical calculations based on the parton quenching model and the modified fragmentation model. The observed differences between data and theory indicate that the correlated yields presented here will further constrain dynamic energy loss models and provide information about the dynamic density profile in heavy-ion collisions.
Longitudinal spin transfer toΛandΛ¯hyperons in polarized proton-proton collisions ats=200 GeV
Abelev, B. I.,Aggarwal, M. M.,Ahammed, Z.,Alakhverdyants, A. V.,Anderson, B. D.,Arkhipkin, D.,Averichev, G. S.,Balewski, J.,Barannikova, O.,Barnby, L. S.,Baumgart, S.,Beavis, D. R.,Bellwied, R.,Benedo American Physical Society 2009 PHYSICAL REVIEW D - Vol.80 No.11
The BRAHMS Experiment at the Relativistic Heavy Ion Collider
Y. K. Lee,I. G. Bearden,D. Beavis,C. Besliu,Y. Blyakhman,J. Brzychczyk,B. Budick,H. Bggild,C. Chasman,C. H. Christensen,P. Christiansen,J. Cibor,R. Debbe,E. Enger,J. J. Gaardhje,K. Grotowski,K. Hagel 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.43 No.I
The BRAHMS probes the hot and dense nuclear matter at the RHIC which has reached its design energy of psNN = 200 GeV for Au + Au collisions. The BRAHMS uses magnetic spectrometers for hadrons covering a large phase space 0 < y < 4 with good particle identification and momentum resolution. A comprehensive investigation of multiplicity distributions of emitted charged particles is carried out. Ratios of yields of antiparticles to particles are also measured as a function of rapidity. Rapidity dependent net-proton yield indicates that substantial transparency has been achieved in these collisions. Transverse momentum spectra of charged hadrons are measured up to 5 GeV/c which indicates a significant medium eect when compared to nucleon + nucleon reference spectra.
STAR Collaboration,Agakishiev, G.,Aggarwal, M.M.,Ahammed, Z.,Alakhverdyants, A.V.,Alekseev, I.,Alford, J.,Anderson, B.D.,Anson, C.D.,Arkhipkin, D.,Averichev, G.S.,Balewski, J.,Beavis, D.R.,Behera, N.K North-Holland Pub. Co 2011 Physics letters: B Vol.704 No.5
We present first measurements of the evolution of the differential transverse momentum correlation function, C, with collision centrality in Au+Au interactions at s<SUB>NN</SUB>=200 GeV. This observable exhibits a strong dependence on collision centrality that is qualitatively similar to that of number correlations previously reported. We use the observed longitudinal broadening of the near-side peak of C with increasing centrality to estimate the ratio of the shear viscosity to entropy density, η/s, of the matter formed in central Au+Au interactions. We obtain an upper limit estimate of η/s that suggests that the produced medium has a small viscosity per unit entropy.
Observation of an Antimatter Hypernucleus
Abelev, B. I.,Aggarwal, M. M.,Ahammed, Z.,Alakhverdyants, A. V.,Alekseev, I.,Anderson, B. D.,Arkhipkin, D.,Averichev, G. S.,Balewski, J.,Barnby, L. S.,Baumgart, S.,Beavis, D. R.,Bellwied, R.,Betancour American Association for the Advancement of Scienc 2010 Science Vol.328 No.5974
Charged-to-neutral correlation at forward rapidity in Au + Au collisions at<sub>sNN</sub>=200GeV
Adamczyk, L.,Adkins, J. K.,Agakishiev, G.,Aggarwal, M. M.,Ahammed, Z.,Alekseev, I.,Alford, J.,Anson, C. D.,Aparin, A.,Arkhipkin, D.,Aschenauer, E. C.,Averichev, G. S.,Banerjee, A.,Beavis, D. R.,Bellwi American Physical Society 2015 PHYSICAL REVIEW C - Vol.91 No.3
Scaling properties at freeze-out in relativistic heavy-ion collisions
Aggarwal, M. M.,Ahammed, Z.,Alakhverdyants, A. V.,Alekseev, I.,Alford, J.,Anderson, B. D.,Anson, C. D.,Arkhipkin, D.,Averichev, G. S.,Balewski, J.,Barnby, L. S.,Beavis, D. R.,Bellwied, R.,Betancourt, American Physical Society 2011 PHYSICAL REVIEW C - Vol.83 No.3
Observation of the antimatter helium-4 nucleus
Agakishiev, H.,Aggarwal, M. M.,Ahammed, Z.,Alakhverdyants, A. V.,Alekseev, I.,Alford, J.,Anderson, B. D.,Anson, C. D.,Arkhipkin, D.,Averichev, G. S.,Balewski, J.,Beavis, D. R.,Behera, N. K.,Bellwied, Nature Publishing Group, a division of Macmillan P 2011 Nature Vol.473 No.7347
High-energy nuclear collisions create an energy density similar to that of the Universe microseconds after the Big Bang; in both cases, matter and antimatter are formed with comparable abundance. However, the relatively short-lived expansion in nuclear collisions allows antimatter to decouple quickly from matter, and avoid annihilation. Thus, a high-energy accelerator of heavy nuclei provides an efficient means of producing and studying antimatter. The antimatter helium-4 nucleus (), also known as the anti-慣 (), consists of two antiprotons and two antineutrons (baryon number B = ??4). It has not been observed previously, although the 慣-particle was identified a century ago by Rutherford and is present in cosmic radiation at the ten per cent level. Antimatter nuclei with B??<????1 have been observed only as rare products of interactions at particle accelerators, where the rate of antinucleus production in high-energy collisions decreases by a factor of about 1,000 with each additional antinucleon. Here we report the observation of , the heaviest observed antinucleus to date. In total, 18 counts were detected at the STAR experiment at the Relativistic Heavy Ion Collider (RHIC; ref. 6) in 10<SUP>9</SUP> recorded gold-on-gold (Au+Au) collisions at centre-of-mass energies of 200??GeV and 62??GeV per nucleon??nucleon pair. The yield is consistent with expectations from thermodynamic and coalescent nucleosynthesis models, providing an indication of the production rate of even heavier antimatter nuclei and a benchmark for possible future observations of in cosmic radiation.