Production In Nuclear Collisions Research Articles

Linear scaling of lepton charge asymmetry in W± production in ultra-relativistic nuclear collisions from PACIAE model

The lepton charge asymmetry in [Formula: see text] production in the nuclear collisions at [Formula: see text][Formula: see text]TeV is investigated with a parton and hadron cascade model PACIAE. Recently published ALICE and the ATLAS data of lepton charge asymmetry are well reproduced. An interesting linear scaling behavior is observed in the lepton charge asymmetry as a function of the collision system valence quark number asymmetry among different sizes of nuclear collision systems at [Formula: see text][Formula: see text]TeV. This linear scaling behavior may serve as an additional constraint on the PDF (nPDF) extractions.

Analysis of the Charged-particle Multiplicity Density in Centrality from Track Lets

This paper shows the relationship between charged hadron diversity and centrality in hadron Pb-Pb collisions at a certain collision energy(2.76 TeV) per nucleon pair. It is found that the centrality from 70–80% to 0–5%, each normalized charged particle density of participating nucleon pair increases by about twice. The collision of particles in the experiment was simulated by ALICE, a detector dedicating heavy-ion physics at the Large Hadron Collider. This work compares the data sample with models based on different mechanisms for particle production in nuclear collisions. And the error analysis of data in the end of this passage ensures the correctness of the experiment.

A study on the isolated photon production in nuclear collisions at the CERN-LHC energies

An analysis of prompt photon production in high energy nuclear collisions at the Large Hadron Collider is performed within the parton saturation picture taking into account the updated phenomenological color dipole models. Comparison between ⟨N coll⟩ scaling for hard scattering in heavy-ion collisions and the N part-scaling based on geometric scaling arguments has been done. The predictions are parameter free in the first case whereas a dependence on the constant of proportionality κ between the number of participants and the nuclear saturation scale appears in the second case. This parameter has been analyzed in the prompt photon spectrum at small transverse momentum even though no fitting procedure was performed. Results are confronted with the measurements made by the ALICE, ATLAS, and CMS experiments in terms of photon transverse momentum at different rapidity bins. We show that the prompt photon production exhibits distinct scalings in AA events associated to geometrical properties of the collision and can be properly addressed in the color dipole formalism. Based on the N part-scaling, an analytical parametrization for the invariant cross section is provided and employed to predict the x T-scaling in measurements. For κ of order of unit the theoretical scaling curve correctly describes data in the range x T ⩽ 5 × 10−2.

Strange mesons in nuclei and neutron stars

The present status in the field of strange mesons in nuclei and neutron stars is reviewed. In particular, the K̅N interaction, that is governed by the presence of the Λ(1405), is analyzed and the formation of the K̅NN bound state is discussed. Moreover, the properties of K̅ in dense nuclear matter are studied, in connection with strangeness production in nuclear collisions and kaon condensation in neutron stars.

Measurement of the prompt-production cross-section ratio σ(χc2)/σ(χc1) in pPb collisions at sNN=8.16 TeV

This Letter reports the first measurement of prompt $\chi_{c1}$ and $\chi_{c2}$ charmonium production in nuclear collisions at Large Hadron Collider energies. The cross-section ratio $\sigma(\chi_{c2}) / \sigma(\chi_{c1})$ is measured in $p$Pb collisions at $\sqrt{s_{NN}}$ = 8.16 TeV, collected with the LHCb experiment. The $\chi_{c1,2}$ states are reconstructed via their decay to a $\rm{J}/\psi$ meson, subsequently decaying into a pair of oppositely charged muons, and a photon, which is reconstructed in the calorimeter or via its conversion in the detector material. The cross-section ratio is consistent with unity in the two considered rapidity regions. Comparison with a corresponding cross-section ratio previously measured by the LHCb collaboration in $pp$ collisions suggests that $\chi_{c1}$ and $\chi_{c2}$ states are similarly affected by nuclear effects occurring in $p$Pb collisions.

Reconstruction of D0 meson in d+Au collisions at = 200 GeV by the STAR experiment

Owing to their large masses, charm quarks are predominantly produced through initial hard scatterings in heavy-ion collisions. Therefore, they can serve as penetrating probes to study the intrinsic properties of the hot medium created in heavy-ion collisions. However, Cold Nuclear Matter effects can also affect the charm quark production in nuclear collisions with respect to p + p collisions. These effects can be measured in small collision systems such as d/p+Au. In these proceedings, D0 meson reconstruction in d+Au collisions at at the STAR experiment is described. Thanks to the excellent impact parameter resolution provided by the Heavy Flavor Tracker detector, D0() mesons are topologically reconstructed from their hadronic decay channel D0 () (). The Boosted Decision Trees machine learning algorithm from the TMVA package is applied in order to improve signal/background separation.

Perspectives of Multistrange Hyperon Study at NICA/MPD from Realistic Monte Carlo Simulation

One of the main tasks of the NICA/MPD physics program is a study of strangeness production in nuclear collisions. In this paper the MPD detector performance for measurements of multistrange hyperons in Au + Au collisions at NICA energies is presented based on the analysis of realistically simulated data samples. Perspectives of the studies on the strangeness production at the experiment start-up are evaluated.

Overview of Hypernuclei Reconstruction at NICA/MPD

The study of the formation of a dense and hot baryonic matter is the main goal of exploration for the NICA/MPD project. Strangeness production in nuclear collisions is a key part of the MPD project physics program and is an important tool for studying the QCD phase diagram. An overview of the relevant characteristics for hypernuclei reconstruction in the NICA energy range with the simulated MPD detector are presented. Focus is put on invariant mass distributions, reconstruction efficiency and expected yields.

Strangeness and nuclei production in nuclear collisions

A critical review of the most recent results obtained on the study of strangeness and (anti–)nuclei production in nuclear collision at ultra–relativistic energies will be presented. Recent measurements of strangeness production at the LHC in high-multiplicity proton-proton (pp) and proton-lead (p–Pb) collisions have shown features that are reminiscent of those observed in lead-lead (Pb–Pb) collisions. These observations warrant a comprehensive measurement of the production of identified particles and are not described satisfactorily by the available Monte Carlo predictions. Another intriguing but not fully understood mechanism, in the high energy physics sector, is the one responsible for the production of light nuclei and anti–nuclei. A detailed description of the available experimental data about (anti–)matter production will be reported and compared with the available models, namely the coalescence approach and the thermal model predictions.

Open heavy-flavour production in nuclear collisions

In these proceedings I will give an overview of the latest experimental results on charm and beauty production at RHIC and the LHC presented at the Quark Matter 2018 conference. The new measurements in p(d)-A collisions have a key impact in the understanding of possible collective effects of heavy quarks in small collision systems. In A-A collisions, new high-precision data and differential observables offer more quantitative ways to investigate different aspects of the interactions of heavy quarks in the Quark Gluon Plasma, like transport properties, energy loss distributions, hadronisation mechanisms, and magnetic effects.

Evaluation study of hypernuclei production at NICA/MPD

The main goal of the NICA/MPD facility is a study of the properties of hot and dense baryonic matter. One of the possible ways of doing this is to study strangeness production in nuclear collisions. The enhanced production of strange particles in heavy-ion collisions is considered to be a signal for the quark-gluon plasma formation. In this paper the MPD detector abilities to measure different hypernuclei species in Au+Au collisions at NICA energy region are presented.

Centrality and pseudorapidity dependence of the charged-particle multiplicity density in Xe–Xe collisions at [formula omitted

In this Letter, the ALICE Collaboration presents the first measurements of the charged-particle multiplicity density, dNch/dη, and total charged-particle multiplicity, Nchtot, in Xe–Xe collisions at a centre-of-mass energy per nucleon–nucleon pair of sNN=5.44TeV. The measurements are performed as a function of collision centrality over a wide pseudorapidity range of −3.5<η<5. The values of dNch/dη at mid-rapidity and Nchtot for central collisions, normalised to the number of nucleons participating in the collision (Npart) as a function of sNN follow the trends established in previous heavy-ion measurements. The same quantities are also found to increase as a function of Npart, and up to the 5% most central collisions the trends are the same as the ones observed in Pb–Pb at a similar energy. For more central collisions, the Xe–Xe scaled multiplicities exceed those in Pb–Pb for a similar Npart. The results are compared to phenomenological models and theoretical calculations based on different mechanisms for particle production in nuclear collisions. All considered models describe the data reasonably well within 15%.

Multicharmed Baryon Production in High Energy Nuclear Collisions

We study nuclear medium effect on multicharmed baryon production in relativistic heavy ion collisions. By solving the three-quark Schroedinger equation at finite temperature, we calculate the wave functions and Wigner functions for doubly and triply charmed baryons \(\varXi _{cc}\) and \(\varOmega _{ccc}\). Their production in nuclear collisions is largely enhanced due to the combination of uncorrelated charm quarks in the quark-gluon plasma. It is most probable to discover these new particles in heavy ion collisions at the RHIC and LHC energies.

Sub-threshold charm production in nuclear collisions

We present the first predictions for sub-threshold open charm and charmonium production in nuclear collisions. The production mechanism is driven by multistep scatterings of nucleons and their resonance states, accumulating sufficient energy for the production of $J/\mathrm{\ensuremath{\Psi}}$, ${\mathrm{\ensuremath{\Lambda}}}_{c}+\overline{D}$, and $D+\overline{D}$. Our results are of particular importance for the CBM experiment at FAIR, as they indicate that already at the SIS100 accelerator one can expect a significant number of charmed hadrons to be produced. This opens new possibilities to explore charm dynamics and the formation of charmed nuclei.

Heavy baryonic resonances, multistrange hadrons, and equilibration at energies available at the GSI Schwerionensynchrotron, SIS18

We study the details and time dependence of particle production in nuclear collisions at a fixed target beam energy of $E_{\mathrm{lab}}= 1.76$ A GeV with the UrQMD transport model. We find that the previously proposed production mechanism for multi strange hadrons, $\phi$ and $\Xi$, are possible due to secondary interactions of incoming nuclei of the projectile and target with already created nuclear resonances, while the Fermi momenta of the nuclei play only a minor role. We also show how the centrality dependence of these particle multiplicities can be used to confirm the proposed mechanism, as it strongly depends on the number of participants in the reaction. Furthermore we investigate the time dependence of particle production in collisions of Ca+Ca at this beam energy, in order to understand the origins of the apparent chemical equilibration of the measured particle yields. We find that indeed the light hadron yields appear to be in equilibrium already from the very early stage of the collision while in fact no local equilibration, through multi collision processes, takes place. The apparent equilibrium is reached only through the decay of the resonances according to available phase space.

Centrality Dependence of the Charged-Particle Multiplicity Density at Midrapidity in Pb-Pb Collisions at sqrt[s_{NN}]=5.02 TeV.

The pseudorapidity density of charged particles, dN_{ch}/dη, at midrapidity in Pb-Pb collisions has been measured at a center-of-mass energy per nucleon pair of sqrt[s_{NN}]=5.02 TeV. For the 5% most central collisions, we measure a value of 1943±54. The rise in dN_{ch}/dη as a function of sqrt[s_{NN}] is steeper than that observed in proton-proton collisions and follows the trend established by measurements at lower energy. The increase of dN_{ch}/dη as a function of the average number of participant nucleons, ⟨N_{part}⟩, calculated in a Glauber model, is compared with the previous measurement at sqrt[s_{NN}]=2.76 TeV. A constant factor of about 1.2 describes the increase in dN_{ch}/dη from sqrt[s_{NN}]=2.76 to 5.02TeV for all centrality classes, within the measured range of 0%-80% centrality. The results are also compared to models based on different mechanisms for particle production in nuclear collisions.

Recent results from strangeness in transport models

In these proceedings we discuss recent developments in the microscopic description of strange particle production in nuclear collisions. We put a special emphasis on the production of hypernuclei at the upcoming FAIR and NICA facilities as well as the deep sub threshold, ϕ and Ξ- production yields measured with the HADES experiment. Employing new resonance decay channels we obtain a satisfactory description of ϕ and Ξ- production in deep sub threshold Ar+KCl reactions. Our results implicate that no new medium effects are required to describe the rare strange particle production data from low energy nuclear collisions.

A feasibility study of hypernuclei reconstruction at NICA/MPD

One of the main tasks of the NICA/MPD physics program is a study of the strangeness production in nuclear collisions. Heavy strange objects (including hypernuclei) could provide essential signatures of the excited and compressed baryonic matter.Study of hypernuclei is important for: understanding the strangeness degrees of freedom in hadronic systems; study of all populated regions in the three-dimensional chart of the nuclides; study of hyperon-nucleus and hyperon-hyperon interactions.The Monte Carlo simulation results presented show that the start version of the MPD detector will provide good conditions for hypernuclei reconstruction in Au+Au collisions at NICA.

Reconstruction of multistrange hyperons with the MPD detector at the NICA collider: a Monte Carlo feasibility study

One of the main tasks of the NICA/MPD physics program is a study of strangeness production in nuclear collisions. In this paper the MPD detector performance for measurements of Λ, Ξ− and Ω− hyperons and their antiparticles \(\bar \Lambda\), \(\bar \Xi ^ +\) and \(\bar \Omega ^ +\) in central Au+Au collisions at NICA energies is presented.

ηcproduction in photon-induced interactions at a fixed target experiment at LHC as a probe of the odderon

One of the open questions of the strong interaction theory is the existence of the Odderon, which is an unambiguous prediction of Quantum Chromodynamics, but still not confirmed experimentally. An alternative to probe the Odderon is the exclusive $\eta_c$ photoproduction in hadronic collisions. As the Pomeron exchange cannot contribute to this process, its observation would indicate the existence of the Odderon. In this paper we estimate the $\eta_c$ production in photon - induced interactions in hadronic collisions at the AFTER@LHC experiment. We demonstrate that the experimental analysis of this process is feasible in the AFTER@LHC experiment and that the observation of the $\eta_c$ production in nuclear collisions is a unambiguous signature of the Odderon.