Behavior of the hadron potential at large distances and properties of the hadron spin-flip amplitude

The impact of the form of the hadron potential at large distances on the behavior of the hadron spin-flip amplitude at small angles is examined. The t-dependence of the spin-flip amplitude of high-energy hadron elastic scattering is analyzed under different assumptions on the hadron interaction. It is shown that the long tail of the nonGaussian form of the hadron potential of the hadron interaction in the impact parameter representation leads to a large value of the slope of the spin-flip amplitude (without the kinematical factor ) as compared with the slope of the spin-nonflip amplitude. This effect can explain the form of the differential cross-section and the analyzing power at small transfer momenta. The methods for the definition of the spin-dependent part of the hadron scattering amplitude are presented. A possibility to investigate the structure of the hadron spin-flip amplitude from the accurate measure of the differential cross-section and the spin correlation parameters is shown. Received: 14 December 2001 / Accepted: 17 January 2002     

相对论重离子碰撞的温度涨落与热容

使用LUCIAE3.0模型模拟了SPS能区Pb+Pb和C+C在不同能量(E_lab=20—200A GeV)和不同中心度下的重离子碰撞.并通过逐个事件的粒子温度涨落提取出了相应粒子的热容,发现对于同一碰撞系统,单位发射粒子的热容随碰撞能量的升高而下降直至饱和,随着碰撞参数b的增大而减小,而且发现单位发射粒子的热容具有随粒子质量的变大而变大的关系.同时还发现不同碰撞系统中同一种粒子具有相同的单位发射粒子热容,并给出了相应的解释.     

Pion showers in highly granular calorimeters

New results on properties of hadron showers created by pion beam at 8?C80 GeV in high granular electromagnetic and hadron calorimeters are presented. Data were used for the first time to investigate the separation of the neutral and charged hadron showers. The result is important to verify the prediction of the PFA algorithm based up to now on the simulated data only. Next, the properties of hadron showers were compared to different physics lists of GEANT4 version 9.3.     

Suppression of back-to-back hadron pairs at forward rapidity in d+Au collisions at √s(NN)=200 GeV

Back-to-back hadron pair yields in d+Au and p+p collisions at √s(NN)=200 GeV were measured with the PHENIX detector at the Relativistic Heavy Ion Collider. Rapidity separated hadron pairs were detected with the trigger hadron at pseudorapidity |η|<0.35 and the associated hadron at forward rapidity (deuteron direction, 3.0<η<3.8). Pairs were also detected with both hadrons measured at forward rapidity; in this case, the yield of back-to-back hadron pairs in d+Au collisions with small impact parameters is observed to be suppressed by a factor of 10 relative to p+p collisions. The kinematics of these pairs is expected to probe partons in the Au nucleus with a low fraction x of the nucleon momenta, where the gluon densities rise sharply. The observed suppression as a function of nuclear thickness, p(T), and η points to cold nuclear matter effects arising at high parton densities.     

High energy hadron spin flip amplitude

The high energy part of the hadron spin flip amplitude is examined in the framework of the new high energy general structure (HEGS) model of the elastic hadron scattering at high energies. The different forms of the hadron spin flip amplitude are compared in the impact parameters representation. It is shown that the existing experimental data of the proton-proton and proton-antiproton elastic scattering at high energy in the region of the diffraction minimum and at large momentum transfer give support in the presence of the energy-independent part of the hadron spin flip amplitude with the momentum dependence proposed in the works by Galynskii–Kuraev.     

核子(强子)结构和性质的QCD研究

核子 (强子 )是夸克、胶子的束缚态 ,由量子色动力学 QCD描述。由于 QCD的基本特性(高能标度下的渐近自由、低能标度下色禁闭及动力学手征对称性破缺 ) ,对核子 (强子 )结构和性质的 QCD图象是标度相关的 .在高能标度下描述强子的是与探测强子结构的硬过程相联系的QCD部分子模型 .强子的夸克、胶子结构信息通过 QCD部分子求和规则得到 .QCD微扰论是适用的理论 .在低能标度时 ,必须发展 QCD非微扰途径来描述核子 (强子 )物理 .这里简要地讨论各种非微扰途径 (格点 QCD、Dyson- Schwinger方程、有效场论、QCD求和规则 )的某些结果和进展 ,并指出 QCD真空结构在描述低能标度下强子物理中担任重要角色 . The nucleon (hadron) is the bound state of guarks and gluons, which is described by the quantum chromodynamics (QCD). Due to the basic properties of QCD (the asymptotic freedom at the high energy scale, the color confinement and the dynamical chiral symmetry breaking at the low energy scale), the QCD picture for the nucleon’s (hadron’s) structure and property is scale dependent. At high energy scale, the QCD parton model, which is relative to the hard process for testing the...     

Parton-cluster model of hadrons and impact parameter structure of non-diffractive collisions

A model of hadron structure and hadron collisions is proposed for interpreting experimental data. It starts from the assumption that a hadron consists of a number of partons with very large masses which are grouped inside hadrons into clusters with quantum numbers of the known hadrons. In hadron collisions the most peripheral clusters behave as spectators and represent leading particles; non-diffractive hadron collisions can then be interpreted mostly as stripping-like reactions. It is shown on a sample of annihilation and non-annihilation pp collisions at 5·7 GeV/c that experimental data for several different leading particles are in good qualitative agreement with the basic requirement of the model which concerns the strong impact parameter angular dependence of the leading particles.Dedicated to Academician Václav Votruba on the occasion of his seventieth birthday.     

A Non-Zero Hadronic Elliptic Flow with a Vanished Partonic Elliptic Flow in a Coalescence Scenario

The elliptic flow of a hadron is calculated using a quark coalescence model based on the quark phase space distribution produced by a free streaming locally thermalized quark in a two-dimensional transverse plane at initial time. Without assuming the quark＇s elliptic flow, it is shown that the hadron obtains a non-zero elliptic flow in this model. The elliptic flow of the hadron is shown to be sensitive to both space momentum correlation and the hadron＇s internal structure. Quark number scaling is obtained only for some special cases.     

A thermodynamical approach to hadron production ine + e − collisions

The hadron production ine ⁺ e ^? collisions is studied assuming that particles originate in a hadron gas at thermal and chemical equilibrium. The parameters of the hadron gas are determined with a fit to the average multiplicities of various hadron species measured at LEP and PEP-PETRA. A strikingly good agreement is found between the predictions of this model and data for almost all particles over a range of production rate of four orders of magnitude. The methods and assumptions of the fit are described and discussed in detail. The temperature of the hadron gas estimated from the fit is around 166 MeV at √s=91.2 GeV and 181 MeV at √s=29÷35 GeV.     

Photon + hadron production in high energy deuteron (proton)–nucleus collisions

We apply the color glass condensate formalism to photon + hadron production cross section in high energy deuteron (proton)–gold collisions at RHIC. We investigate the dependence of the production cross section on the angle between the produced hadron and photon for various rapidities and transverse momenta. It is shown that the angular correlation between the produced hadron and photon is a sensitive probe of the saturation dynamics.     

Hadron Experimental Facility at J-PARC

We introduce the hadron experimental facility at J-PARC. High-intensity secondary beam lines are in operation, where kaons, pions, and antiprotons are delivered for experiments in hadron, nuclear, and particle physics. We present overview of some experimental programs in this facility. A high-momentum beam line is under construction, where a new research project is proposed by RCNP of Osaka University under the MoU on collaborative research among RCNP, IPNS/KEK, and the J-PARC center. A future plan to extend the hadron experimental facility is also described.     

Hadron production in relativistic nuclear collisions: thermal hadron source or hadronizing quark-gluon plasma?

Measured hadron yields from relativistic nuclear collisions can be equally well understood in two physically distinct models, namely a static thermal hadronic source vs. a time-dependent, nonequilibrium hadronization off a quark-gluon plasma droplet. Due to the time-dependent particle evaporation off the hadronic surface in the latter approach the hadron ratios change (by factors of ) in time. Final particle yields reflect time averages over the actual thermodynamic properties of the system at a certain stage of the evolution. Calculated hadron, strangelet and (anti-)cluster yields as well as freeze-out times are presented for different systems. Due to strangeness distillation the system moves rapidly out of the , plane into the -sector. Strangeness to baryon ratios prevail during a considerable fraction (50%) of the time evolution (i.e. -droplets or even -droplets form the system at the late stage: The possibility of observing this time evolution via two-particle correlations is discussed). The observed hadron ratios require MeV and MeV. If the present model is fit to the extrapolated hadron yields, metastable hypermatter can only be produced with a probability for . Received: 15 April 1997 / Revised version: 5 June 1997     

Baryon yields, isospin effects and strangeness production in elementary hadronic interactions

New NA49 data from hadron+proton and hadron+Pb interactions are used to extract detailed information on projectile isospin effects and baryon, baryon pair and strangeness production. Consequences for the interpretation of hadron production and strangeness enhancement in nuclear collisions are discussed.     

Detector Effects on the Response of a Highly Granular Hadron Calorimeter to Single Hadrons

In the detectors currently being developed for experiments on the next-generation lepton colliders, highly granular calorimeters are to be used. In particular, the hadron calorimeter is planned to be assembled from scintillation cells with direct readout of light by silicon photomultipliers. According to the results of experimental measurements of the light collection in a cell developed for the CALICE prototype hadron calorimeter, when detecting minimum ionizing particles, an estimate of the detector effects was obtained. The detector effect on the resolution of the ILD hadron calorimeter was studied by modeling the response of the detector to single neutral kaons. It was shown that the contribution of experimentally measured detector effects to the resolution for single particles is on the order of 0.5–1% in the range of hadron energy of 5–60 GeV.     

Identical particle effect in azimuthal correlations at small rapidity separation

The difference of the short range effect observed in azimuthal correlations of like and unlike particle pairs is interpreted as due to an identical and unidentical boson effect, resp., in the decay of clusters produced in the central region of hadron hadron collisions.     

Thermodynamics of hadronic matter at high density

We calculate thermodynamics observables for an interacting relativistic hadron gas. Hadronic states are taken into account by the use of a sizeable portion of the experimental hadron spectrum, supplemented in some cases by an exponentially rising continuum. Calculations with non-zero baryon number densities, subject to the additional requirement of zero net strangeness, show structure in the heat capacity per unit volume of the baryon sector at a temperature of approximately 140 MeV. This structure also becomes visible in the total heat capacity per unit volume at large baryon number densities, and provides a signature for the change of the thermal response of the hadron gas from baryon- to meson-dominated, even though the meson number density is lower than the baryon number density. Furthermore, this structure is not seen in calculations with a massless hadron gas. Its origin is therefore associated with information contained in the hadronic mass spectrum, and thus with the sub-hadronic degrees of freedom of the hadrons.