Multiplicity moments using Tsallis statistics in high-energy hadron–nucleus interactions

The study of higher-order moments of a distribution and its cumulants constitute a sensitive tool to investigate the correlations between the particle produced in high-energy interactions. In our previous work, we have used the Tsallis [Formula: see text] statistics, NBD, Gamma and shifted Gamma distributions to describe the multiplicity distributions in [Formula: see text]-nucleus and [Formula: see text]-nucleus fixed target interactions at various energies ranging from [Formula: see text][Formula: see text]GeV to 800[Formula: see text]GeV. In this study, we have extended our analysis by calculating the moments using the Tsallis model at these fixed target experiment data. By using the Tsallis model, we have also calculated the average charged multiplicity and its dependence on energy. It is found that the average charged multiplicity and moments predicted by the Tsallis statistics are in much agreement with the experimental values and indicates the success of the Tsallis model on data from visual detectors. The study of moments also illustrates that KNO scaling hypothesis holds good at these energies.

Constituent quarks and systematic errors in mid-rapidity charged multiplicity dNch/dη distributions

Centrality definition in A + A collisions at colliders such as RHIC and LHC suffers from a correlated systematic uncertainty caused by the efficiency of detecting a p + p collision ([Formula: see text] for PHENIX at RHIC). In A + A collisions where centrality is measured by the number of nucleon collisions, [Formula: see text], or the number of nucleon participants, [Formula: see text], or the number of constituent quark participants, [Formula: see text], the error in the efficiency of the primary interaction trigger (Beam–Beam Counters) for a p + p collision leads to a correlated systematic uncertainty in [Formula: see text], [Formula: see text] or [Formula: see text] which reduces binomially as the A + A collisions become more central. If this is not correctly accounted for in projections of A + A to p + p collisions, then mistaken conclusions can result. A recent example is presented in whether the mid-rapidity charged multiplicity per constituent quark participant [Formula: see text] in Au + Au at RHIC was the same as the value in p + p collisions.

Internal Cumulants for Femtoscopy with Fixed Charged Multiplicity

A detailed understanding of all effects and influences on higher-order correlations is essential. At low charged multiplicity, the effect of a non-Poissonian multiplicity distribution can significantly distort correlations. Evidently, the reference samples with respect to which correlations are measured should yield a null result in the absence of correlations. We show how the careful specification of desired properties necessarily leads to an average-of-multinomials reference sample. The resulting internal cumulants and their averaging over several multiplicities fulfill all requirements of correctly taking into account non-Poissonian multiplicity distributions as well as yielding a null result for uncorrelated fixed-Nsamples. Various correction factors are shown to be approximations at best. Careful rederivation of statistical variances and covariances within the frequentist approach yields errors for cumulants that differ from those used so far. We finally briefly discuss the implementation of the analysis through a multiple event buffer algorithm.

DESCRIPTION OF (PSEUDO-)RAPIDITY DENSITY AND TRANSVERSE MOMENTUM DISTRIBUTIONS IN A WIDE ENERGY RANGE $(\sqrt{s} = 22.4\hbox{--}7000~{\rm GeV})$

The rapidity density and transverse momentum distributions of produced particles in multiple particle production are formulated assuming that the produced particles are emitted isotropically from several emitting centers. The energy distribution of produced particles in the rest frames of respective emitting centers is that of the Tsallis statistics. The distribution of emitting centers is flat with slanting cuts at both shoulders on the rapidity axis in the center of mass system. The formulation includes six adjustable parameters, among which four are energy dependent and more important and are determined so that the transverse momentum and the (pseudo-)rapidity density distributions fit to the data at various energies. The energy dependences of the four parameters, determined empirically, reproduce quite well the energy dependence of the average transverse momentum, that of the pseudo-rapidity density at η* = 0 and that of the charged multiplicity. The energy dependence of the inelasticity is either increasing or decreasing from the assumed value of K = 0.5 at [Formula: see text], due to lack of experimental data at the most-forward rapidity region. The pseudo-rapidity density distribution at LHC energy [Formula: see text] expected by the present formulation is compared with those by the other models.

CHARGED MULTIPLICITY DISTRIBUTION IN RELATIVISTIC HEAVY-ION COLLISIONS

The experimental results of multiplicity distributions of grey and relativistic shower particles emitted in the interactions of 28 Si and 12 C ions at 4.5 A GeV /c with nuclear emulsion are reported. The study of the multiplicity distributions of relativistic shower particles and medium energy target-associated protons produced in heavy-ion collisions seems to observe the semi-inclusive KNO scaling. A simplified universal function has been used to represent the experimental data.

ELLIPTIC FLOW SIMULATION AND ANALYSIS IN ALICE

Based on flow measurements at the SPS and RHIC, the expected values of elliptic flow and charged multiplicity have been extrapolated as a function of the impact parameter to LHC energy. Those predictions have been used as an input for ALICE simulation, to develop and test a flow analysis package for the ALICE environment. The Event Plane analysis has provided an estimate of the event plane resolution at the LHC and it has also been applied to Hijing events generated with no genuine elliptic flow. In this kind of environment it has been possible to study the effects on v2 from pure non-flow effects, and thus get an estimate of the systematics due to non-flow.