Backward Multiplicity Correlations Research Articles

System scan of the multiplicity correlation between forward and backward rapidities in relativistic heavy-ion collisions using a multi-phase transport model * *Supported in part the National Natural Science Foundation of China (11890710, 11890714, 11875066, 11925502, 11961141003), the Strategic Priority Research Program of CAS (XDB34000000), National Key R&D Program of China (2018YFE0104600, 2016YFE0100900), and Guangdong Major Project of Basic and Applied

A systematic study on forward–backward (FB) multiplicity correlations from large systems to small ones through a multi-phase transport model (AMPT) has been performed and the phenomenon that correlation strength increases with centrality can be explained by taking the distribution of events as the superposition of a series of Gaussian distributions. It is also found that correlations in the plane can imply the shape of the event. Furthermore, long-range correlations originate from the fluctuations associated with the source information. FB correlations allow us to decouple long-range correlations from short-range correlations, and may provide a chance to investigate the α-clustering structure in initial colliding light nuclei as well. It seems the tetrahedron 16O + 16O collision gives a more uniform and symmetrical fireball, that emits the final particles more isotropically or independently in the longitudinal direction, indicating that the forward–backward multiplicity correlation could be used to identify the pattern of α-clustered 16O in future experiments.

Extraction of multiple parton interactions and color reconnection from forward\u2013backward multiplicity correlations

Forward–backward multiplicity correlations have been studied in electron-positron, proton–proton and more recently in lead-lead collisions. For the proton–proton case, comparison of experimental results to different models reveals an incomplete understanding of the physical phenomenon associated with these correlations. In this work, we present a study of forward–backward multiplicity correlations in proton–proton collisions using the PYTHIA event generator, at LHC energies. A detailed analysis is presented with and without weak decays, splitting data samples into soft and hard QCD processes, and comparing the computed correlations for short and long range pseudorapidity regions. Each of these regions is analyzed accounting for the effects of color reconnection and independent multiple parton interactions. We show that a combination of these effects is required to explain the latest measurements on proton–proton data. Furthermore, is shown that from measurements of multiplicity correlations is possible to extract the average number of multiple parton interactions in the event producing these correlations, and albeit model depending, to predict the strength of these correlations, not yet measured, for higher energy collisions.

On the origin of forward–backward multiplicity correlations in pp collisions at ultrarelativistic energies

We study multiplicity correlations of hadrons in forward and backward hemispheres in pp inelastic interactions at energies 200 GeV≤s≤13 TeV within the microscopic quark–gluon string model. The model correctly describes (i) the almost linear dependence of average multiplicity in one hemisphere on the particle multiplicity in other hemisphere in the centre-of-mass frame; (ii) the increase of the slope parameter bcorr with rising collision energy; (iii) the quick falloff of the correlation strength with increase of the midrapidity gap; (iv) saturation of the forward–backward correlations at very high multiplicities. Investigation of the sub-processes on partonic level reveals that these features can be attributed to short-range partonic correlations within a single string and superposition of several sub-processes containing different numbers of soft and hard Pomerons with different mean multiplicities. If the number of Pomerons in the event is fixed, no forward–backward correlations are observed. Predictions are made for the top LHC energy s=13 TeV.

Forward backward multiplicity correlations: a tool to study properties of the proton-proton collisions

Forward-backward multiplicity correlations have been used to study hadron production mechanisms in electron-positron, proton-proton and more recently in leadlead collisions. The experimental results on this correlations and its comparison to different models reveals an incomplete agreement. In this work, we present an study of forward backward multiplicity correlations in proton-proton collisions using PYTHIA event generator, at LHC energies. Detailed analysis is presented in the case of soft and hard QCD processes, incorporating color reconnection model as part of hadronization mechanism and multiple parton interactions effects in the correlations. Our results and its comparison to available experimental data suggest that this kind of correlations are great tools to characterize the events and gives the possibility to disentangle phenomena in hard and soft QCD processes.

Forward–backward multiplicity correlations in ring like and jet like events in 16O–AgBr interactions at 60 AGeV

We have studied the forward–backward correlations of charged-particle multiplicities in symmetric bins in pseudorapidity space in order to gain insight into the underlying correlations structure of particle production in case of ring-like and jet-like events of 16O–AgBr interactions at 60 AGeV. The variance σc2 of a suitably defined the forward-backward asymmetry variable C has been determined. The experimental results confirm correlations of the produced particles in the forward and the backward pseudorapidity region for both ring-like and jet-like events.

Forward--Backward Multiplicity Correlations at the LHC from Independent Sources

It is argued that the superposition approach, where partons are independently emitted from longitudinally extended sources in the early stage, is fully compatible with the experimental results for the forward-backward multiplicity correlations in Pb+Pb collisions at $\sqrt{s_{NN}}=2.76 \textrm{ TeV}$. The pertinent correlation analysis is based on the PhD Thesis of Ref. [1], which includes an unpublished analysis of data taken by the ALICE Collaboration. Our calculations show that in the experimentally covered pseudorapidity range $\Delta \eta=1.2$, the initial sources in the backward and forward bins are maximally correlated, which complies to the string-like interpretation of the underlying early-stage production mechanism.

Forward–backward multiplicity correlations at STAR

Forward–backward multiplicity correlations measured at STAR are discussed. A strong long-range correlation for inclusive charged hadrons was measured as a function of pseudorapidity separation (Δ η) in Au+Au collisions at s NN = 200 GeV , and were shown to decrease with decreasing centrality. STAR preliminary results show the correlation strength for pions, kaons, (anti)protons as a function of rapidity separation (Δ y) in 0–10% and 10–20% Au+Au collisions at s NN = 200 GeV . The Color Glass Condensate picture, which describes particle sources as longitudinal flux tubes, predicts that the correlation will grow with centrality. Fluctuations in the number of gluons at early times will produce a long-range correlation strength larger for pions than for baryons. A strong, long-range correlation is measured for pions in central collisions, which decreases for 10–20% collisions.

STAR's measurement of long-range forward–backward multiplicity correlations as the signature of ‘dense partonic matter’ in heavy-ion collisions at

Forward–backward multiplicity correlations have been measured with the STAR detector for Au + Au, Cu + Cu and p + p collisions at . A strong, long-range correlation is observed for central heavy-ion collisions that vanishes in semi-peripheral events and p + p collisions. Both the dual parton model and the color glass condensate indicate that long-range correlations are due to multiple parton interactions. This suggests that dense partonic matter might have been created in mid-central and central Au + Au collisions at .

Theoretical analysis for the apparent discrepancy between [formula omitted] and pp data in charged particle forward–backward multiplicity correlations

The strength of charged particle forward–backward multiplicity correlation in p¯+p and p+p collisions at s=200GeV is studied by PYTHIA 6.4 and compared to the UA5 and STAR data correspondingly. It is turned out that a factor of 3–4 apparent discrepancy between UA5 and STAR data can be attributed to the differences in detector acceptances and observing bin interval in both experiments. A mixed event method is introduced and used to calculate the statistical correlation strength and the dynamical correlation strengths stemming from the charge conservation, four-momentum conservation, and decay, respectively. It seems that the statistical correlation is much larger than dynamical one and the charge conservation, four-momentum conservation and decay may account for most part of the dynamical correlation. In addition, we have also calculated the correlation strength by fitting the charged particle multiplicity distribution from PYTHIA to the Negative Binomial Distribution and found that the result agrees well with the correlation strength calculated by mixed events.

Forward–backward multiplicity correlations in 4.5 A GeV/c16O–emulsion interactions

A detailed study of the mechanisms of the emissions of pions and protons in the forward and backward hemispheres in 4.5 A GeV/c oxygen-emulsion interactions has been carried out. The correlations between the multiplicities of secondary charged particles in the backward and forward hemispheres are investigated.

One-parameter cascade model of multiple hadrons production in inelastic hh-processes at high energies

The inhomogeneous cascade-stochastic model of multiple hadrons production in inelastic p ¯ p - and pp-interactions at high energies is proposed. In this model inclusive rapidity distributions of secondary hadrons are used as input data. One-parameter cascade-stochastic multiplicity distribution, where adjustable parameter has sense of the height of Feynman plateau of inclusive rapidity distribution of secondary hadrons in one hadron shower, is obtained. It is shown that all known now experimental data concerning both multiplicity and rapidity distributions of secondary particles in inelastic hh-processes in energy range s = 30 – 1800 GeV , and also the ratio of cumulant moments to factorial moments of the multiplicity distributions in energy range s = 200 – 900 GeV are described with high accuracy by one-parameter cascade-stochastic model of multiple hadrons production. The explicit form of asymptotic of distributions as well-known Polyakov–Dokshitzer's scaling function for quark and gluon jets is obtained by fitting of prognosis multiplicity distributions at energies s = 14 – 30 TeV . A simplified quantitative analysis is presented and the qualitative explanation of behavior features of forward–backward multiplicity correlations is given within the framework of proposed model.

Open problems in forward–backward multiplicity correlations in hadron–hadron collisions in the TeV region

Continuing previous work on forward–backward multiplicity correlation properties in proton–proton collisions in the framework of the weighted superposition model of two components (each one described by a negative binomial multiplicity distribution) with the addition of the leakage parameter which controls clan spreading from one hemisphere to the opposite one, we examine E735 data on the c.m. energy dependence of the total correlation strength and of the forward variance at fixed total multiplicity. A comparison with the Chou–Yang approach to the problem is presented and extrapolations of the mentioned variables at LHC c.m. energy in possible scenarios in the new energy domain are discussed.

Forward-backward multiplicity correlations and leakage parameter behaviour in asymmetric high-energy collisions

Forward–backward multiplicity correlations are studied in asymmetric collisions in the framework of the weighted superposition mechanism of different classes of events. New parameters for the asymmetric clan distribution and for the particle leakage from clans in one hemisphere to the opposite one are introduced to effectively classify different classes of collisions. This tool should be used to explore forward–backward multiplicity correlations in AB and pA collisions in present and future experiments at RHIC and LHC.

Features of forward-backward multiplicity correlations in hadronic collisions

The forward–backward multiplicity correlations among the charged particles produced in the interactions of 24 and 400 GeV protons and 50 and 340 GeV pions with emulsion nuclei are being investigated. The results of hadron–nucleus interactions have been compared with those of hadron–hadron interactions. The variations of average values in the forward–backward hemisphere with the multiplicity in the opposite hemisphere have been studied by dividing the data into different ηc-intervals also.

Forward-backward multiplicity correlations in 4.5A GeV/c silicon-nucleus interactions.

A detailed study of the mechanism of emission of pions and protons in the forward and backward hemispheres in 4.5A GeV/c silicon-emulsion interactions has been carried out. For this purpose, a random sample comprising 1024 interactions caused by silicon nuclei is analyzed to examine the behavior of the emission characteristics of pions and protons emitted in the forward and backward hemispheres. The values of the forward-backward ratio and the asymmetry parameter as a function of the number of heavily ionizing particles are determined. The behavior of the angular distributions of pions and protons in the backward hemisphere and multiplicity correlations is also investigated. The results yield quite interesting information regarding the mechanism of production of pions and protons in the backward hemisphere.

Differences between charge—charge forward—backward multiplicity correlations in multiparticle production

We analyze new data from hadron—hadron collisions on forward—backward correlations. The difference between these correlations for unlike and like charges implies different dynamical correlations at fixed impact parameter. These different correlations should be observable in e + e − annihilations.

Pion and proton production in forward and backward hemisphere in 12C-emulsion interaction at 4.5 GeV/c per nucleon

Abstract The paper presents an in-depth study on the forward and backward multiplicity correlations in case of pions and protons (from the target) based on the experimental data on 12C-emulsion interaction at 4.5 GeV/c per nucleon. The cumulative distribution of their emission angles in the backward hemisphere is presented. The asymmetry parameter (A) and the forward-backward ratio ( F B ) as a function of the number of heavy particles (nh) is also shown. The results reveal many interesting characteristics regarding the backward particle production.