Dual Parton Model Research Articles

Dual parton model for the charged multiplicity in p−p collisions at 13, 13.6 TeV and for a future LHC energy of 27 TeV

Analysis of the charged multiplicity in proton-proton inelastic interactions at the LHC energies in the setting of Dual Parton Model is presented. Data from the CMS experiment and the data simulated at different energies in various pseudo-rapidity windows using the event generator PYTHIA8are analysed and compared with the calculations from the model. Each inelastic scattering is assumed to follow the Poisson distribution. The theoretical Koba-Nielsen-Olesen (KNO) scaling of the multiplicity distributions is studied and compared with previously published experimental results at $\sqrt{s}$ = 0.9, 2.36, 7 TeV. Predictions from the model for the KNO distributions at $\sqrt{s}$ = 13, 13.6 TeV and for the future LHC energy of 27 TeV are computed and compared with the simulated data.

Baryon number in proton-proton and proton-nucleus high energy collisions

New analyses of baryon spectra in proton-proton and proton-carbon collisions at sqrt{s}_mathrm {_{NN}}=17.3 GeV, made in the framework of two phenomenological models are presented. The first model in question is the classic Dual Parton Model by Capella and Tran Thanh Van, the second is the Gluon Exchange Model very recently proposed by the authors. For both studies, the usage of modern experimental data from the CERN SPS eliminates several of the most important limitations inherent to earlier studies of this type. In both studies, the standard mechanism of baryon stopping with preservation of the diquark, proposed by Capella and Tran Thanh Van fails to describe the distribution of non-strange baryons in collisions of the projectile proton with more than one nucleon from the carbon target obtained from experimental data, and the upper limit for the contribution of this mechanism can be established. In both cases, the conclusion is that the projectile diquark must be very often disintegrated. This opens new diagrams not available in proton-proton collisions which lead to the transport of baryon number over long distances in rapidity. The present limitations, and possibility of improvement in both approaches are discussed. The implications of our findings for new measurements are addressed, in particular using antiproton beams.

Growth of Long Range Forward-Backward Multiplicity Correlations with Centrality inAu+AuCollisions atsNN=200 GeV

Forward-backward multiplicity correlation strengths have been measured with the STAR detector for Au + Au and p + p collisions at square root of s(NN) = 200 GeV. Strong short- and long-range correlations (LRC) are seen in central Au + Au collisions. The magnitude of these correlations decrease with decreasing centrality until only short-range correlations are observed in peripheral Au + Au collisions. Both the dual parton model (DPM) and the color glass condensate (CGC) predict the existence of the long-range correlations. In the DPM, the fluctuation in the number of elementary (parton) inelastic collisions produces the LRC. In the CGC, longitudinal color flux tubes generate the LRC. The data are in qualitative agreement with the predictions of the DPM and indicate the presence of multiple parton interactions.

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 .

FORWARD-BACKWARD MULTIPLICITY CORRELATIONS IN Au+Au COLLISIONS AT $\sqrt{s_{NN}} = 200\, {\rm GeV}$

The study of correlations among particles produced in different rapidity regions may provide understanding of the mechanisms of particle production. Correlations that extend over a longer range are observed in hadron-hadron interactions only at higher energies. Results for short and long-range multiplicity correlations (Forward-Backward) are presented for Au + Au collisions at [Formula: see text]. The growth of long range correlations are observed as a function of the pseudorapidity gap in central Au + Au collisions. The Dual Parton model and Color Glass Condensate phenomenology have been explored to understand the origin of long range correlations.

UNDERSTANDING THE PARTICLE PRODUCTION MECHANISM WITH CORRELATION STUDIES USING LONG AND SHORT RANGE CORRELATIONS

Long range forward-backward multiplicity correlations have been measured with the STAR detector for Au + Au collisions at [Formula: see text]. Strong long range correlations are observed in central Au + Au collisions. Based on the Dual Parton model and Color Glass Condensate considerations the data suggests that these long range correlations are due to multiple parton interactions. This suggests that dense partonic matter is created in central Au + Au collisions at [Formula: see text].

$J/\psi$ suppression at $\sqrt{{\bf s}} = 200$ GeVin the comovers’ interaction model

The yield of $J/\psi$ per binary nucleon-nucleon collision in AuAu and CuCu collisions at $\sqrt{s} = 200$ GeV is computed in the framework of the dual parton model, supplemented with final state interaction (comovers’ interaction). For the latter we use the same value of the cross-section, $\sigma_{\mathrm{{co}}} = 0.65$ mb, which describes the anomalous $J/\psi$ suppression observed at CERN-SPS energies. Several possibilities for the value of the absorptive cross-section are considered. Shadowing is introduced in both the comovers’ and the $J/\psi$ yields. A comparison with the results at CERN-SPS, including a prediction for InIn collisions, is also presented.

QGP SIGNALS AND THE DUAL PARTON MODEL: IS THERMAL EQUILIBRIUM REACHED IN HEAVY ION COLLISIONS?

Some of the so-called signals of Quark Gluon Plasma (QGP) formation are examined in the framework of a string model, the Dual Parton Model, supplemented with final state interaction. The aim is to determine the strength and duration time of the final state interaction required to describe the data, in order to gain some insight on whether or not the system reaches thermal equilibrium.

Dpmjet-III, learning from RHIC data for cosmic ray particle production

Dpmjet-III is based on the Dual Parton Model and the QCD parton model. It allows the simulation of hadron-hadron, hadron-nucleus and nucleus-nucleus interactions from a few GeV up to very high energies. We discuss (i) the comparison of DPMJET-III to data from RHIC and (ii) new features of the model needed to describe the data. These new features include percolation and fusion of strings.

An Alternative Way of Plotting the Data and Results of Models of J /ψ Suppression

We propose an alternative way of looking at data on anomalous J/psi suppression. The proposed method is in principle equivalent to the one used by the NA50 Collaboration, but it permits to visualize separate contributions of individual processes responsible for the disintegration of J/psi's produced by a hard process in nuclear collisions. The method can be used provided that the time sequence of contributing mechanisms is known or assumed. It offers an alternative graphical presentation of the onset of anomalous J/psi suppression in Pb-Pb interactions observed by the NA50 Collaboration at the CERN SPS and might contribute to explain why different mechanisms, such as J/psi suppression by the Quark-Gluon Plasma and by co-movers in the Dual Parton Model or in Monte Carlo microscopic approaches, all lead to an approximate description of anomalous J/psi suppression.

Strange particle production at RHIC in the dual parton model

We compute the mid-rapidity densities of pions, kaons, baryons and antibaryons in $Au$-$Au$ collisions at $\sqrt{s} =$ 130 GeV in the Dual Parton Model supplemented with final state interaction (comovers interaction). The ratios $B/n_{part}$ ($\bar{B}/n_{part}$) increase between peripheral ($n_{part} = 18$) and central ($n_{part} = 350)$ collisions by a factor 2.4 (2.0) for $\Lambda$'s, 4.8 (4.1) for $\Xi$'s and 16.5 (13.5) for $\Omega$'s. The ratio $K^-/\pi^-$ increases by a factor 1.3 in the same centrality range. A comparison with available data is presented.

J/ ψ suppression at SPS and RHIC in the comovers approach

The NA50 collaboration data on the $J/\psi$ suppression are compared with the results obtained in a comovers approach based on the Dual Parton Model (DPM). Predictions for the $J/\psi$ suppression versus the charged multiplicity - measured in the rapidity region of the dimuon trigger - are given for SPS and RHIC energies.

Q2-dependence of backward pion multiplicity in neutrino–nucleus interactions

The production of pions emitted backward in inelastic neutrino-nucleus interactions is analyzed within the impulse approximation in the framework of the dual parton model. We focus on the $Q^2$-dependence of the multiplicity of negative pions, normalized to the total cross section of the reaction $\nu + A \to \mu + X$. The inclusion of planar (one-Reggeon exchange) and cylindrical (one-Pomeron exchange) graphs leads to a multiplicity that decreases as $Q^2$ increases, in agreement with recent measurements carried out at CERN by the NOMAD collaboration. A realistic treatment of the high momentum tail of the nucleon distribution in a nucleus also allows for a satisfactory description of the semi-inclusive spectrum of backward pions.

Dual parton model

Abstract I briefly review the theoretical basis of the Dual Parton model and its main applications to multiparticle production in hadronic and nuclear interactions.

Charged particle fluctuation as signal of the dynamics in heavy ion processes

We compare the dispersion of the charges in a central rapidity box according to the Dual Parton Model with the predictions of statistical models. Significant deviations are found in heavy ion collisions at RHIC and LHC energies. Hence the charged particle fluctuations should provide a clear signal of the dynamics of heavy ion processes. They should allow to directly measure the degree of thermalization in a quantitative way.

Centrality dependence of hadron multiplicities in nuclear collisions in the dual parton model

We show that, even in purely soft processes, the hadronic multiplicity in nucleus-nucleus interactions contains a term that scales with the number of binary collisions. In the absence of shadowing corrections, this term dominates at mid rapidities and high energies. Shadowing corrections are calculated as a function of impact parameter and the centrality dependence of mid-rapidity multiplicities is determined. The multiplicity per participant increases with centrality with a rate that increases between SPS and RHIC energies, in agreement with experiment.

Hyperon enhancement in the dual parton model

We review the two sources of hyperon enhancement in the dual parton model: strings originating from diquark-antidiquark pairs in the nucleon sea and net baryons containing two or three sea quarks with a yield controlled by the observed stopping. We show that by adding final state interactions (including strangeness exchange reactions as well as the inverse reactions required by detailed balance) with a single averaged cross section, σ = 0.2 mb, we can explain the observed hyperon enhancement in PbPb collisions at CERN SPS.

MARS Code Developments, Benchmarking and Applications

Recent developments of the MARS Monte Carlo code system for simulation of hadronic and electromagnetic cascades in shielding, accelerator and detector components in the energy range from a fraction of an electronvolt up to 100 TeV are described. The physical model of hadron and lepton interactions with nuclei and atoms has undergone substantial improvements. These include a new nuclear cross section library, a model for soft pion production, a cascade-exciton model, a dual parton model, deuteron-nucleus and neutrino-nucleus interaction models, a detailed description of negative hadron and muon absorption, and a unified treatment of muon and charged hadron electromagnetic interactions with matter. New algorithms have been implemented into the code and benchmarked against experimental data. A new Graphical-User Interface has been developed. The code capabilities to simulate cascades and generate a variety of results in complex systems have been enhanced. The MARS system includes links to the MCNP code for neutron and photon transport below 20 MeV, to the ANSYS code for thermal and stress analyses and to the STRUCT code for multi-turn particle tracking in large synchrotrons and collider rings. Results of recent benchmarking of the MARS code are presented. Examples of non-trivial code applications are given for the Fermilab Booster and Main Injector, for a 1.5 MW target station and a muon storage ring.

Soft and semi-hard components in multiplicity distributions at TeV energies

We present a multiplicity distribution model with two components, soft (S) and semi-hard (SH), in the TeV region. The two components are supposed to have a common physical origin, as they result from the superposition of independent collisions, such that both can be represented by negative binomial distributions with parameters 〈 n〉 and k satisfying k S/〈 n〉 S= k SH/〈 n〉 SH. We discuss the relation of our model to multicollision models (Dual Parton Model, unitarized eikonal models).

Baryon stopping and hyperon enhancement in the improved dual parton model

We present an improved version of the dual parton model which contains a new realization of the diquark breaking mechanism of baryon stopping. We reproduce in this way the net baryon yield in nuclear collisions. The model, which also considers strings originating from diquark-antidiquark pairs in the nucleon sea, reproduces the observed yields of p and Lambda and their antiparticles and underestimates cascades by less than 50 %. However, Omega's are underestimated by a factor five. Agreement with data is restored by final state interaction, with an averaged cross-section as small as 0.14 mb. Hyperon yields increase significantly faster than antihyperons, in agreement with experiment.