Search Results (7)

In this work, we performed a comparative study between HIJING, Sibyll, and QGSJET model-based event generators. Such Monte Carlo (MC) models are used to simulate the interaction and propagation of high-energy cosmic radiation (e.g., coming from the sun) with the Earth’s atmosphere. The global event observables selected for the study were the transverse momentum ($p_{\mathrm{T}}$) spectra and rapidity density distributions of strange particles (${\mathrm{K}}_{\mathrm{S}}^0$, $\Lambda$, and ${\Xi }^{-}$). This study was performed in the STAR and CMS fiducial phase spaces by simulating the strange particles in $pp$ collisions at $\sqrt{\mathrm{s}}$ = 200 GeV, 900 GeV, and 7 TeV, and the simulations were then compared to the experimental measurements. It was observed that none of the discussed model-based event generators ultimately predicted the experimental results, except QGSJET, which generally agrees reasonably with the data. However, QGSJET does not produce $\Xi$ particles; therefore, it does not provide any predictions for $\Xi$. The other two models reproduced the data only in a limited rapidity or transverse momentum region while mainly underpredicting the data in the rest of the areas. These cosmic radiation simulation models are capable of covering the mid-rapidity regions of density distributions. Utilizing model-based observations, some fundamental parameters can be re-tuned and extrapolations to the highest energies can be investigated. Furthermore, these observations can provide valuable insights that could potentially constrain and improve perturbative- and non-perturbative-based QCD event generators, thereby facilitating a better understanding of the underlying physics. Full article

The non-extensive statistical description of the identified final state particles measured in high energy collisions is well-known by its wide range of applicability. However, there are many open questions that need to be answered, including but not limited to, the question of the observed mass scaling of massive hadrons or the size and multiplicity dependence of the model parameters. This latter is especially relevant, since currently the amount of available experimental data with high multiplicity at small systems is very limited. This contribution has two main goals: On the one hand we provide a status report of the ongoing tuning of the soon-to-be-released HIJING++ Monte Carlo event generator. On the other hand, the role of multiplicity dependence of the parameters in the non-extensive hadronization model is investigated with HIJING++ calculations. We present cross-check comparisons of HIJING++ with existing experimental data to verify its validity in our range of interest as well as calculations at high-multiplicity regions where we have insufficient experimental data. Full article

A study investigating a possible jet shape dependence on the charged event multiplicity was performed on collision samples generated by Monte–Carlo (MC) event generators Pythia and Hijing++. We calculated the integral jet shape and found a significant modification caused by multiple-parton interactions. By interchanging and enabling different model ingredients in the simulations and analyzing the results in several $p_{\mathrm{T}}$ bins and event multiplicity classes, we found a characteristic jet size measure that was independent of the chosen tunes, settings, and jet reconstruction algorithms. Full article

The first measurements of isospin fluctuations in the kaon sector is presented in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV. A robust statistical observable was used to extract the isospin fluctuations of neutral and charged kaons as a function of collision centrality. The results show a significant variation in the behaviour of ${\nu }_{dyn}$ in data when compared to Monte-Carlo models such as HIJING and AMPT. The deviation from 1/n scaling in data indicates possible isospin fluctuation in the kaon sector in heavy ion collisions. Full article

This paper presents a comparative study of forward-backward correlations and multiplicity fluctuations in experimental data and in HIJING Monte Carlo simulations of Pb–Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV. The analysis focuses on two observables: the forward-backward correlation coefficient $b_{corr}^{n-n}$ and the strongly intensive quantity $\Sigma$ . Results are discussed in the context of the dependence on centrality estimator and influence of event-by-event fluctuations of the geometry of the Pb–Pb collisions on the measured quantities. Full article

HIJING++ (Heavy Ion Jet INteraction Generator) is the successor of the widely used original HIJING, developed almost three decades ago. While the old versions (1.x and 2.x) were written in FORTRAN, HIJING++ was completely rewritten in C++. During the development we keep in mind the requirements of the high-energy heavy-ion community: the new Monte Carlo software have a well designed modular framework, therefore any future modifications are much easier to implement. It contains all the physical models that were also present in it’s predecessor, but utilizing modern C++ features it also includes native thread based parallelism, an easy-to-use analysis interface and a modular plugin system, which makes room for possible future improvements. In this paper we summarize the results of our performance tests measured on 2 widely used architectures. Full article

We study the charged event multiplicity dependence of the jet structure in pp collisions. We present evidence for jet shape modification due to multi-parton interactions using PYTHIA and HIJING++ Monte Carlo (MC) event generators as an input to our analysis. We introduce a characteristic jet size measure which is independent of the choice of simulation parameters, parton distribution functions, jet reconstruction algorithms and even of the presence or absence of multi-parton interactions. We also investigate heavy-flavor jets and show the sensitivity of the multiplicity-differential jet structure to flavor-dependent fragmentation. Full article