Interferometry Study in High-Energy Nuclear Collisions

高能核碰撞的干涉测量研究

• 批准号: 08044092
• 负责人: SUMI Yoshio
• 金额: $ 6.91万
• 依托单位: HIROSHIMA UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for international Scientific Research
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1997
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08044092/
• 关键词: High-energy heavy-ion collisions; HBT effect; Multiparticle production; Quark gluon plasma; NA44 Collaboration; CERN-SPS; 高エネルギーハドロン物質; クォークグルオンプラズマ

By means of the NA44 focussing spectrometer at the CERN-SPS,we have carried out a high-precision measurement of one-and two-particie spectra of hadrons emitted from Pb+Pb collisions at 158 GeV per nucleon. AII of singles spectra for pions, kaons, protons and deuterons show a Boltzmann-like distribution in the transverse mass (mT) with hadron-mass dependent temperature parameter. The parameter is linear in hadron mass, thereby implying that the hadron source expands with an average velocity of 0.4 times the velocity of light and the hadron-freezeout temperature is about 140 MeV.From the observed particle ratios it is found that if a chemical equilibrium is attained, the chemical equilibrium temperature is about 170 MeV,being somewhat higher than the freezeout temperature, and the chemical potential for u and d quarks is about 70 MeV,whereas that for strange quark is nearly equal to 30 MeV.HBT interferometry study has been carried out for two-particle spectra, giving three dimentional HBT radius parameters RL,RTO and RTS.Values of these parameters for the Pb+Pb are always larger than the corresponding ones in p+Pb at 450 GeV and S+Pb at 200 GeV per nucleon. These HBT radii show an approximate inverse-square-root scaling in mT, consistently with thermal hydrodynamical model. The multiplicity density dependence of the HBT radii for pions shows that the pion freezeout occurs when the source expands up to a state in which the energy density goes down to a constant value which is close to that of normal nucleus.

利用CERN-SPS的NA-44聚焦谱仪，对158 GeV/核子的Pb+Pb碰撞产生的强子的单粒子谱和双粒子谱进行了高精度测量。π介子、K介子、质子和氘核的单能谱在横质量（mT）上均呈现类玻耳兹曼分布，且温度参数与强子质量有关。该参数与强子质量成线性关系，这意味着强子源以0.4倍光速的平均速度膨胀，强子冻结温度约为140 MeV。从观测到的粒子比可以发现，如果达到化学平衡，化学平衡温度约为170 MeV，略高于冻结温度，u、d夸克的化学势约为70 MeV，而奇异夸克的化学势约为30 MeV。对双粒子谱进行了HBT干涉测量研究，给出了三维HBT半径参数RL，Pb+Pb的这些参数的值总是大于450 GeV的p+Pb和200 GeV的S+Pb的相应值。这些HBT半径显示出近似的反平方根标度在mT，与热流体动力学模型一致。π介子HBT半径与多重数密度的关系表明，当源膨胀到能量密度下降到一个接近正常核的常值时，π介子就会冻结.

项目成果

I.G.Bearden et al.: "Particle rations from central Pb+Pb collisions at the CERN SPS" Journal of Physics G. 23. 1865-1871 (1997)

I.G.Bearden 等人：“CERN SPS 中心 Pb Pb 碰撞的粒子配给”《物理学杂志》G. 23. 1865-1871 (1997)

H.Boggild: "Coulomb effect in single particle distributions" Physics Letter. B372 Nos.3&4. 339-342 (1996)

H.Boggild：“单粒子分布中的库仑效应”《物理快报》。

I.G.Bearden et al.: "Mid-rapidity protons in 158A・GeV Pb+Pb collisions" Physics Letters B. 388. 431-436 (1996)

I.G.Bearden 等人：“158A・GeV Pb+Pb 碰撞中的中快速质子”Physics Letters B. 388. 431-436 (1996)

K.Kaimi et al.: "Multiplicity dependence of the pion source in S+A collisions at the CERN SPS" Zeitschhrift fur Physik C. 75. 619-625 (1997)

K.Kaimi 等人：“CERN SPS SA 碰撞中π介子源的多重依赖性”Zeitschhrift Physik C. 75. 619-625 (1997)

I.G.Bearden et al: "Particle ratios from central Pb+Pb collisions at the CERN SPS" Journal of Physics G. 23. 1865-1871 (1997)

I.G.Bearden 等人：“CERN SPS 中心 Pb Pb 碰撞的粒子比率”《物理学杂志》G. 23. 1865-1871 (1997)