共查询到18条相似文献,搜索用时 156 毫秒
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用相对论输运模型模拟了束流动能为520MeV/u的238U+238U碰撞实验. 研究了在两种极端对撞方位的UU碰撞中, 末态核子和π介子椭圆流v2与碰撞参数、快度以及横动量的依赖关系. 研究表明, 由于挤压(squeeze-out)效应, 末态核子和π具有负的椭圆流; 体-体UU中心碰撞事件具有最大初始坐标空间形变, 因而具有最大的负的椭圆流, 约12%; 在最小无偏事件样本下, 体-体和头-头碰撞, 中央快度平台上的核子椭圆流大小相当, 而前者π椭圆流略大于后者; 在中央快度平台, 低横动量核子和π主要由反应后期Δ衰变得到, 而高横动量主要是参与核子再散射生成, 因而在低横动量区它们具有相似的流, 而在较高横动量区(>0.3GeV/c)由于旁观核子的再散射和吸收效应, 它们的椭圆流有明显压低. 相似文献
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按照夸克随机组合的简单组合模型, 本文通过分析得出重子反重子比率与夸克反夸克平均产生几率的关系. 进一步计算了相对论重离子碰撞过程中各种反粒子与粒子的比率, 不需要任何额外假定, 预言的比率与RHIC加速器√SNN=130GeV时Au+Au碰撞STAR实验的结果基本一致. 表明夸克组合模型能够解释相对论重离子碰撞过程的反粒子与粒子比率. 相似文献
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Ackermann KH Adams N Adler C Ahammed Z Ahmad S Allgower C Amsbaugh J Anderson M Anderssen E Arnesen H Arnold L Averichev GS Baldwin A Balewski J Barannikova O Barnby LS Baudot J Beddo M Bekele S Belaga VV Bellwied R Bennett S Bercovitz J Berger J Betts W Bichsel H Bieser F Bland LC Bloomer M Blyth CO Boehm J Bonner BE Bonnet D Bossingham R Botlo M Boucham A Bouillo N Bouvier S Bradley K Brady FP Braithwaite ES Braithwaite W Brandin A Brown RL Brugalette G Byrd C Caines H 《Physical review letters》2001,86(3):402-407
Elliptic flow from nuclear collisions is a hadronic observable sensitive to the early stages of system evolution. We report first results on elliptic flow of charged particles at midrapidity in Au+Au collisions at square root(S)NN = 130 GeV using the STAR Time Projection Chamber at the Relativistic Heavy Ion Collider. The elliptic flow signal, v2, averaged over transverse momentum, reaches values of about 6% for relatively peripheral collisions and decreases for the more central collisions. This can be interpreted as the observation of a higher degree of thermalization than at lower collision energies. Pseudorapidity and transverse momentum dependence of elliptic flow are also presented. 相似文献
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Adcox K Adler SS Ajitanand NN Akiba Y Alexander J Aphecetche L Arai Y Aronson SH Averbeck R Awes TC Barish KN Barnes PD Barrette J Bassalleck B Bathe S Baublis V Bazilevsky A Belikov S Bellaiche FG Belyaev ST Bennett MJ Berdnikov Y Botelho S Brooks ML Brown DS Bruner N Bucher D Buesching H Bumazhnov V Bunce G Burward-Hoy J Butsyk S Carey TA Chand P Chang J Chang WC Chavez LL Chernichenko S Chi CY Chiba J Chiu M Choudhury RK Christ T Chujo T Chung MS Chung P Cianciolo V Cole BA D'Enterria DG 《Physical review letters》2002,89(21):212301
Two-particle azimuthal correlation functions are presented for charged hadrons produced in Au+Au collisions at the Relativistic Heavy Ion Collider (sqrt [s(NN)]=130 GeV). The measurements permit determination of elliptic flow without event-by-event estimation of the reaction plane. The extracted elliptic flow values (v2) show significant sensitivity to both the collision centrality and the transverse momenta of emitted hadrons, suggesting rapid thermalization and relatively strong velocity fields. When scaled by the eccentricity of the collision zone epsilon, the scaled elliptic flow shows little or no dependence on centrality for charged hadrons with relatively low p(T). A breakdown of this epsilon scaling is observed for charged hadrons with pT >1.0 GeV/c. 相似文献
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Based on a hydro-inspired azimuthally symmetric emission function, we analyze the HBT radius Rs and the single-particle transverse momentum spectra in Au+Au collisions measured by the STAR Collaboration at SNN = 200 GeV. The results show that consistent assumptions about transverse density (and/or flow profile) in the calculation of the HBT radius Rs and single-particle spectral analyses play an important role for understanding the size of the freeze-out source. 相似文献
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A new robust method to extract the specific shear viscosity (η/s)(QGP) of a quark-gluon plasma (QGP) at temperatures T(c) < T ? 2T(c) from the centrality dependence of the eccentricity-scaled elliptic flow v2/ε measured in ultrarelativistic heavy-ion collisions is presented. Coupling viscous fluid dynamics for the QGP with a microscopic transport model for hadronic freeze-out we find for 200 A GeV Au + Au collisions that v2/ε is a universal function of multiplicity density (1/S)(dN(ch)/dy) that depends only on the viscosity but not on the model used for computing the initial fireball eccentricity ε. Comparing with measurements we find 1<4π(η/s)(QGP) < 2.5 where the uncertainty range is dominated by model uncertainties for the values of ε used to normalize the measured v2. 相似文献
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Using QMD model the time evolution of Au+Au system at 100MeV/u is studied.For very central collisions the conditions for freeze-out and how the different physical quantities approaching equlibrium are investigated.The calculated results show that for 100MeV/u Au+Au at b=0fm,the maximum density can reach 1.6ρ0 and after that the system expands to a low density region.A position correlated central flow is developed during the expansion stage.By studying the two pamicle reladve momentum spectrum it is able to separate central flow from random thenmal motion.The dependence of this central flow on E.O.S.is also discussed. 相似文献
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We perform a systematic study of elliptic flow(v_2) in Au+Au collisions at(~SNN)~(1/2) = 5 GeV by using a microscopic transport model, JAM. The centrality, pseudorapidity, transverse momentum and beam energy dependence of v_2 for charged as well as identified hadrons are studied. We investigate the effects of both the hadronic mean-field and the softening of equation of state(EoS) on elliptic flow. The softening of the EoS is realized by imposing attractive orbits in two body scattering, which can reduce the pressure of the system. We found that the softening of the EoS leads to the enhancement of v_2, while the hadronic mean-field suppresses v_2 relative to the cascade mode. It indicates that elliptic flow at high baryon density regions is highly sensitive to the EoS and the enhancement of v_2 may probe the signature of a first-order phase transition in heavy-ion collisions at beam energies of a strong baryon stopping region. 相似文献
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A. Ster M. Csanád T. Csörgő B. Lörstad B. Tomášik 《The European Physical Journal A - Hadrons and Nuclei》2011,47(4):58
We present calculations of elliptic flow and azimuthal dependence of correlation radii in the ellipsoidally symmetric generalization
of the Buda-Lund hydrodynamic model of hadron production in high-energy nuclear collisions. We compare them to data from RHIC
by simultaneous fits to azimuthally integrated invariant spectra of pions, kaons and protons-antiprotons measured by PHENIX
in Au + Au reactions at center-of-mass energy of 200 AGeV. STAR data were used for azimuthally sensitive two-particle correlation
function radii and for the transverse momentum dependence of the elliptic flow parameter v
2. We have found that the transverse flow is faster in the reaction plane than out of plane, which results in a reaction zone
that gets slightly more elongated in-plane than out of plane. The model parameters extracted from the fits are shown and discussed. 相似文献