Multiplicity Distributions Of Particles Research Articles

Controlling volume fluctuations for studies of critical phenomena in nuclear collisions

We generalize and extend the recently proposed method [1] to account for contributions of system size (or volume/participant) fluctuations to the experimentally measured moments of particle multiplicity distributions. We find that in the general case there are additional biases which are not directly accessible to experiment. These biases are, however, parametrically suppressed if the multiplicity of the particles of interest is small compared to the total charged-particle multiplicity, e.g., in the case of proton number fluctuations at top RHIC and LHC energies. They are also small if the multiplicity distribution of charged particles per wounded nucleon is close to the Poissonian limit, which is the case at low energy nuclear collisions, e.g., at GSI/SIS18. We further find that mixed events are not necessarily needed to extract the correction for volume fluctuations. We provide the formulas to correct pure and mixed cumulants of particle multiplicity distributions up to any order together with their associated biases.

Study of negative binomial distribution in neutrino and anti-neutrino–nucleus interactions of CHORUS experiment

In this study, the charged particle multiplicity distribution produced in anti-neutrino and neutrino-nuclear emulsion interactions is studied in terms of negative binomial distribution in varying invariant mass of the hadronic system intervals for the first time. Many articles have shown that the negative binomial distribution is very useful in describing and interpreting the multiplicity of experimental data in the literature. For this reason, a similar study is conducted on neutrino and anti-neutrino interactions to better understand the particle production mechanism. Experimental data for the analysis are obtained from the CHORUS Collaboration paper on the production of charged particles in anti-neutrino and neutrino-nuclear emulsion interactions at high energy. For multiplicity distributions of both interactions, the invariant mass of the hadronic system intervals is defined as given in the CHORUS Collaboration article. Then the negative binomial fit is applied to the experimental data for each energy range. In terms of chi-square values for both interactions, a good agreement has been observed between the experimental data and their fit in each energy range. The results of applied fits are shown through figures and tables, presenting the obtained chi-square values, free parameters, and their energy dependence.

Multiplicity Distributions and Modified Combinants in the Multipomeron Model of pp Interaction at High Energies

The multiplicity distributions of charged particles and their combinants for pp collisions at LHC energies are studied within the Multipomeron Exchange Model (MEM) that takes into account the phenomenon of string fusion. It is shown that the use of Gaussian-type distributions for multiplicity distributions at a fixed number of pomerons allows, within the MEM framework, the reproduction of the resulting multiplicity distributions and the oscillatory behavior of combinants, found in the ALICE and CMS pp collision data at LHC energies. It is important that in the proposed approach, the parameters of these Gaussian-type distributions are not considered free, but are calculated from the two-particle correlation function of a single string.

Pseudorapidity, transverse momentum and multiplicity distributions of charged particles in pp collisions at 13 TeV

Pseudorapidity, transverse momentum and multiplicity distributions of charged particles in pp collisions at 13 TeV

Imprints of clustering in multiplicity fluctuations

In this paper, we investigate the multiplicity fluctuations of charged particles observed in high-energy nuclear collisions and relate them to the size of hadronizing systems which happen during such processes. We use the average multiplicities langle Nrangle and variances Varleft( Nright) of multiplicity distributions of charged particles produced in centrality selected collisions of relativistic heavy-ion nuclei to evaluate the dynamic variance varOmega and study its dependence on the size of colliding systems. We connect the observed system-size dependence of multiplicity fluctuations with the clustering phenomena and the finiteness of the hadronizing sources and the thermal bath.

A model-free procedure to correct for volume fluctuations in E-by-E analyses of particle multiplicities

We develop an innovative and unbiased procedure, based on event mixing, to account for unavoidable contributions from volume (or system size) fluctuations to experimentally measured moments of particle multiplicity distributions produced in relativistic nuclear collisions. Within the wounded-nucleon model they are characterized by fluctuations of the number of wounded nucleons, the latter usually referred to as participants. For the first time we extract participant fluctuations directly from the data used for the fluctuation analysis, i.e., without involving model calculations. To achieve this we constructed a dedicated event-mixing algorithm that eliminates all possible correlations between produced particles while preserving the volume fluctuations. The procedure provides direct access to the cumulants of wounded-nucleon distributions, which can be used to account for non-critical contributions to the experimentally measured cumulants of multiplicity distributions.

Scaling approach to nuclear structure in high-energy heavy-ion collisions

In high-energy heavy-ion collisions, the initial condition of the produced quark-gluon plasma (QGP) and its evolution are sensitive to collective nuclear structure parameters describing the shape and radial profiles of the nuclei. We find a general scaling relation between these parameters and many experimental observables such as elliptic flow, triangular flow, and particle multiplicity distribution. In particular, the ratios of observables between two isobar systems depend only on the differences of these parameters, but not on the details of the final state interactions, hence offering a new way to constrain the QGP initial condition. Using this scaling relation, we show how the structure parameters of ${}_{44}^{96}\mathrm{Ru}$ and ${}_{40}^{96}\mathrm{Zr}$ conspire to produce the rich centrality dependences of these ratios, as measured by the STAR Collaboration. Our scaling approach demonstrates that isobar collisions are a precision tool to probe the initial condition of heavy-ion collisions, as well as the collective nuclear structures, including the neutron skin, of the atomic nuclei across energy scales.

QGP generation and evolution simulation of pp collision on LHC

In this paper, the generation of Quark-Gluon Plasma(QGP) in proton–proton collisions is discussed based on the thermal equilibrium theory. A partons list at the initial stage of collisions are obtained by digital sampling method, which provides a reasonable initial state for the subsequent evolution simulation. The calculation shows that the multiplicity distribution of the final charged particles obtained by this method is very similar to that of experiment or PYTHIA event generator. Thus, a new mechanism for hadron production in LHC is proposed.

Nuclei in the toy world: beyond the Pomeron in zero transverse dimensions

We explore possible extensions of the t-channel and s-channel unitary model of high energy evolution in zero transverse dimensions appropriate to very high energy/atomic number where the dipole density in a toy hadron is parametrically high. We suggest that the appropriate generalization is to allow emission of more than one dipole in a single step of energy evolution. We construct explicitly such a model that preserves the t-channel and s-channel unitarity and have the correct low density limit, and study the particle multiplicity distribution resulting from this evolution. We consider initial conditions of a single dipole and many dipoles at initial rapidity. We observe that the saturation regime in this model is preceded by a parametric range of rapidities frac{1}{alpha_s}ln frac{1}{alpha_s}<Y<frac{1}{alpha_s}ln frac{1}{alpha_s^2} , where the saturation effects are still unimportant, but multiple emissions determine the properties of the evolution. We also discuss the influence of the saturation on the parton cascade and, in particular, find that in the saturation regime the entropy of partons becomes S ≈ frac{1}{2} ln N where N is the mean multiplicity.

Multiplicity Distribution and KNO Scaling of Charged Particles Production from pp Collisions at Different Energies

The multiplicity distribution of charged particles produced from proton–proton collisions at energies s = 2.36, 2.76, 5, 7, 8, 10, 13 and 14 TeV were studied in the present work. Furthermore, multiplicity distribution was studied in different pseudorapidity regions ∣η∣ &lt; 0.5, 1, 1.5, 2, and 2.5. KNO scaling was studied at the same pseudorapidity regions. This is valid in the pseudorapidity region ∣η∣ &lt; 0.5, but with increasing pseudorapidity, the violation increases. The influence of MPI and color reconnection in violation of KNO scaling were studied. The relation between mean multiplicity and collisions energy was explored, noted that it increases with the increasing energy of collisions.

Sub-Poissonian multiplicity distributions in jets produced in hadron collisions

In this work we show that the proper analysis and interpretation of the experimental data on the multiplicity distributions of charged particles produced in jets measured in the ATLAS experiment at the LHC indicates their sub-Poissonian nature. We also show how, by using the recurrence relations and combinants of these distributions, one can obtain new and otherwise unavailable information contained in them, which may broaden our knowledge of the particle production mechanism.

Properties of charged particle multiplicities in anti-neutrino interactions of the CHORUS experiment

In this study, the charged particle multiplicity distribution produced in anti-neutrino interactions in nuclear emulsion is investigated in terms of the log-normal parametric model and KNO-G scaling for the first time. The results are based on the data collected by the CHORUS experiment in the nu _{mu } beam from CERN SPS. The analysis of 369 bar{nu }_{mu }CC events showed that anti-neutrino charged-particle multiplicity data shape is well described by a log-normal distribution. Furthermore, KNO-G scaling has been successfully applied to the data and results confirm the validity of KNO-G scaling for the anti-neutrino interactions. Finally, results are presented in detail in the form of figures and tables.

Statistical Scrutiny of Particle Spectra in ep Collisions

Charged particle multiplicity distributions in positron–proton deep inelastic scattering at a centre-of-mass energy s = 300 GeV, measured in the hadronic centre-of-mass frames and in different pseudorapidity windows are studied in the framework of two statistical distributions, the shifted Gompertz distribution and the Weibull distribution. Normalised moments, normalised factorial moments and the H-moments of the multiplicity distributions are determined. The phenomenon of oscillatory behaviour of the counting statistics and the Koba-Nielsen-Olesen (KNO) scaling behaviour are investigated. This is the first such analysis using these data. In addition, projections of the two distributions for the expected average charged multiplicities obtainable at the proposed future ep colliders.

Scaling of factorial moments in cumulative variables

A search for power-law fluctuations within the framework of the intermittency method is ongoing to locate the critical point of the strongly interacting matter. In particular, experimental data on proton and pion production in heavy-ion collisions are analyzed in transverse-momentum, pT, space.In this regard, we have studied the dependence of the second scaled factorial moment F2 of particle multiplicity distribution on the number of subdivisions of transverse momentum-interval used in the analysis. The study is performed using a simple model with a power-law two-particle correlation function in pT. We observe that F2 values depend on the size and position of the pT interval. However, when we convert the non-uniform transverse-momentum distribution to uniform one using cumulative transformation, F2 calculated in subdivisions of the cumulative pT becomes independent of the cumulative-pT interval. The scaling behaviour of F2 for the cumulative variable is observed. Moreover, F2 follows a power law with the number of subdivisions of the cumulative-pT interval with the intermittency index close to the correlation function's exponent.

Log-normal and Negative Binomial Distributions of DONUT Data

There are several parametric models to describe the charged particle multiplicity distributions in literature. Among them, log-normal distribution and negative binomial distribution are the most well-known parametric models. In this study, negative binomial and log-normal distributions are compared and tested in neutrino interactions produced in DONUT experiment. This analysis was carried out using the real experimental results of the DONUT Collaboration. The results of the analysis show that the neutrino data, reported by DONUT collaboration, is well described by negative binomial and log-normal distribution. In terms of fit parameters, the χ/ndf value of the both distribution NBD and LND are close to unity but log-normal distribution data slightly better than negative binomial distribution.

Emission characteristics of target black fragments in 16O-Emulsion collisions at 3.7AGeV

As a function of collision centrality, the multiplicity and angular distributions for the slowest target fragments (black particles) emitted in interactions of 16O ions with emulsion nuclei at 3.7[Formula: see text]A[Formula: see text]GeV were investigated. The multiplicity distribution is unaffected by the projectile’s energy or mass. At different impact parameters, the higher moments of multiplicity distributions of black particles were measured. The calculated values of the scaled variance (variance divided by the mean) show that the emission of slower target fragments at high energies is not a statistically independent process in all cases. At various projectile spectators, the angular distributions of the emitted black particles were investigated. The obtained data were compared to the statistical model’s predictions to describe the process responsible for producing secondary particles.

Multiplicity characteristics of the produced shower particles in backward direction-target and projectile dependence

In the present paper a detailed investigation of the multiplicity distribution of the produced shower particles in the backward hemisphere ( $$\theta _{\mathrm {Lab}} \ge 90^{\circ }$$ ) in nuclear emulsion track detector has been carried out. The present study involves interactions of $$^{\mathrm {16}}\hbox {O}$$ and $$^{\mathrm {32}}\hbox {S}$$ projectiles with CNO, AgBr and composite emulsion target at 4.5 AGeV/c. We have compared our results with the results obtained from the analysis of modified Fritiof model. Present study reveals that the production of single shower particle is the most dominant production mode of shower particles in the backward direction. This probability increases with the increase of target mass. The percentage of events having backward shower particles remains almost independent of the projectile beam. But it increases with the increase of target size. Average multiplicity of the shower particles in the backward direction reflects a weaker dependence on the mass number of the projectile beam. Multiplicity distribution of backward shower particles for both experimental and modified Fritiof model can be described by an expression $$\mathrm {P}_{\mathrm {N}} = {\mathrm {P}_{\mathrm {s}}\mathrm {N}_{\mathrm {B}}}^{-{\uplambda }_{\mathrm {B}}}$$ . The fitting parameter $${\uplambda }_{\mathrm {B}}$$ decreases as the target size increases. The decay constant has lower value for the heavier projectile. Higher order multiplicity moments and scaled variance of multiplicity distribution for the backward shower particles showed strong target dependence. Multiplicity distributions of the backward shower particles violate KNO scaling law. Modified Fritiof model failed to reproduce the various features of the multiplicity distribution.

Backward shower particle production in high energy nucleus–nucleus collisions — an outlook to centrality dependence

A detailed study on the centrality dependence of the different aspects multiplicity distribution of the shower particles produced in the backward direction ([Formula: see text] in nuclear emulsion track detector has been carried out for [Formula: see text]Ne-emulsion interactions at 4.1 AGeV/c. Depending on the values of the total charges or sum of the charges of noninteracting projectile fragments, event samples were classified into four centrality classes. From the analysis presented in this paper, qualitative information about the assembly of shower particles in the backward direction has been extracted.

Measurement of charged particle multiplicity distributions in DIS at HERA and its implication to entanglement entropy of partons

Charged particle multiplicity distributions in positron-proton deep inelastic scattering at a centre-of-mass energy sqrt{s}=319 GeV are measured. The data are collected with the H1 detector at HERA corresponding to an integrated luminosity of 136 pb^{-1}. Charged particle multiplicities are measured as a function of photon virtuality Q^2, inelasticity y and pseudorapidity eta in the laboratory and the hadronic centre-of-mass frames. Predictions from different Monte Carlo models are compared to the data. The first and second moments of the multiplicity distributions are determined and the KNO scaling behaviour is investigated. The multiplicity distributions as a function of Q^2 and the Bjorken variable x_{mathrm{bj}} are converted to the hadron entropy S_{mathrm{hadron}}, and predictions from a quantum entanglement model are tested.

The nuclear effect analysis in relativistic heavy ion collisions at BNL energies

In this article, an attempt has been made to understand the behavior of the secondary charged particles multiplicity distributions produced during the heavy ion collisions at ultra-relativistic energies by using the Hurst exponent of the two dimensional (2D) factorial moments, Fq. For this purpose the experimental data have been analyzed by using the “Hurst exponent” in the original intermittency formula by considering different values of Hurst exponent (H = 1.0, 1.5, 2.0, 2.5). The investigations reveal the power-law behavior, exhibited in self-affine or nuclear effect analysis, better than that in the self-similar analysis. Finally, the described works were found very much significant and also it was within good agreement with some other works.