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M. Ajaz

Publications and source records attributed to M. Ajaz.

At least 19 recordsLinked to original sources

Analyses of the collective properties of hadronic matter in Au-Au collisions at 54.4 GeV

We investigated the strange hadrons transverse momentum ($p_T$) spectra in Au-Au collision at $\sqrt {s_{NN}}$ = 54.4 GeV in the framework of modified Hagedorn function with embedded flow. We extracted the kinetic freeze-out temperature $T_0$, transverse flow velocity $β_T$, kinetic freeze-out volume $V$, mean transverse momentum $ $, the entropy parameter $n$ and the multiplicity parameter $N_0$. We reported that all these parameters increase towards the central collisions. The larger kinetic freeze-out temperature , transverse flow velocity, kinetic freeze-out volume and the entropy parameter (n) in central collisions compared to peripheral collisions show the early decoupling of the particles in central collisions. In addition, all the above parameters are mass dependent. The kinetic freeze-out temperature ($T_0$), the entropy parameter $n$ and mean transverse momentum ($ $) are larger for massive particles, while the transverse flow velocity ($β_T$), kinetic freeze-out volume ($V$) and the multiplicity parameter ($N_0$) show the opposite behavior. Larger $T_0$, $n$ and smaller $β_T$ as well as $V$ of the heavier particles indicates the early freeze-out of the heavier particles, while larger $ $ for the heavier particles evince that the effect of radial flow is stronger in heavier particles. The separate set of parameters for each particle shows the multiple kinetic freeze-out scenario, where the mass dependent kinetic freeze-out volume shows the volume differential freeze-out scenario. We also checked the correlation among different parameters, which include the correlation of $T_0$ and $β_T$, $T_0$ and $V$, $β_T$ and $V$, $ $ and $T_0$, $ $ and $β_T$, $ $ and $V$, $n$ and $T_0$, $n$ and $β_T$, and $n$ and $V$, and they all are observed to have positive correlations with each other which validates our results.

hep-ph

Model studies of V0 production ratios in $pp$ collisions at $\sqrt{\mathrm{s}}$ = 0.2, 0.9, and 7 TeV

A comparative study of $V^0$ ratios has been performed between HIJING, Sibyll and QGSJET model-based event generators in this paper. The ratios under study are {\alam}/{\lam}, {\alam}/{\ks} and {\xim}/{\lam} as a function of rapidity $y$, rapidity loss ($Δy$) and {\ppt} from $pp$ collisions at \sqrts~= 0.2, 0.9, and 7 TeV and these simulations are then compared with the STAR and LHCb fiducial phase spaces in different {\ppt} regions. Although the models could produce some of the ratios in a limited {\ppt} and/or $y$ region, none of them completely predicts the experimental results. The QGSJET has good predictions with the data in most of the cases but since the model does not include the $Ξ$ particle definition, therefore it does not give any predictions for $Ξ$/{\lam} ratios. The extrapolation to the highest possible energies can be studied by re-tune some of the basic parameters based on current and previous measurements. These kinds of systematic comparison studies are also useful to apply certain constraints on the pQCD and non-pQCD-based hadronic event generators to significantly improve the predictions of Standard Model physics at the RHIC and LHC experimental data for the understanding of underlying physics mechanisms in high energy collisions.

hep-ph

Extraction of different temperatures and kinetic freeze-out volume in high energy collisions

We analyze the transverse momentum ($p_T$) spectra, $1/N_{ev}$[(1/2$π$$p_T$) $d^2$$N$/$dyd$$p_T$], of kaon, proton, deuteron and triton in different centrality events in gold-gold (Au-Au) collisions at Relativistic Heavy Ion Collisions (RHIC) by Hagedorn thermal model and extracted the excitation function of effective temperature, kinetic freeze-out volume, initial temperature and kinetic freeze-out temperature. We perceived that the effective temperature, initial temperature and kinetic freeze-out temperature sharply increases from 7.7 GeV to 14.5 GeV and then remain static from 14.5-39 GeV, and this consistency may disclose that the onset energy of the phase transition of partial deconfinement and the whole deconfinement are 14.5 and 39 GeV respectively. The kinetic freeze-out volume and mean transverse momentum grows with the rise of collision energy. Furthermore, the different extracted temperatures are observed in the order of time evolution of the interacting system, and they (as well as kinetic freeze-out volume) have an increasing trend from peripheral to central collisions. We also observed the mass dependence of the effective temperature and kinetic freeze-out volume where former increases while the later decreases for heavier particles, which indicates the early freeze-out of the heavier particles.

nucl-th

Measurements of $π^{\pm}$ differential yields from the surface of the T2K replica target for incoming 31 GeV/c protons with the NA61/SHINE spectrometer at the CERN SPS

Measurements of particle emission from a replica of the T2K 90 cm-long carbon target were performed in the NA61/SHINE experiment at CERN SPS, using data collected during a high-statistics run in 2009. An efficient use of the long-target measurements for neutrino flux predictions in T2K requires dedicated reconstruction and analysis techniques. Fully-corrected differential yields of $π^\pm$-mesons from the surface of the T2K replica target for incoming 31 GeV/c protons are presented. A possible strategy to implement these results into the T2K neutrino beam predictions is discussed and the propagation of the uncertainties of these results to the final neutrino flux is performed.

hep-ex

The study of light nuclei production in different interactions at 4.2 AGeV/c

Average multiplicity of light nuclei produced in different interactions at 4.2A GeVc is studied as a function of centrality. A change in multiplicity is observed with increase in the mass of projectile. In 12CC-interactions an unexpected increase in the multiplicity is seen for the most central events. These measurements are compared with the predictions of Cascade and Fritiof Models which fail to account for the experimentally observed effects. In case of 12CC it is suggested that the inclusion of nuclear coalescence effect can be an explanatory reason for the differences between the experimental measurements and the models predictions.

nucl-ex

Study of some characteristics of protons using interactions of light nuclei

Behavior of some average characteristics of protons are studied in protons and deuterons induced interactions with carbon nuclei at 4.2 A GeV/c. The emitted particles are divided in two groups depending on their polar angle in the lab. frame using half angle technique. Results of the experimental data are compared with Dubna version of cascade model. Analysis of the results show that the incone protons are leading particles.

nucl-ex

Study of the behavior of nuclear modification factor in freeze-out state

One of the latest trends in the advancement of experimental high-energy physics is to identify the quark gluon plasma (QGP) predicted qualitatively by quantum chromodynamics (QCD). We discuss whether nuclear transparency effect which is considered an important phenomenon, connected with dynamics of hadron-nuclear and nuclear-nuclear interactions could reflect some particular properties of the medium. FASTMC is used for Au-Au collision at RHIC energies. Critical change in the transparency is considered a signal on the appearance of new phases of strongly interacting matter and the QGP.

nucl-ex

Observation of light nuclei formation as nuclear coalescence in CC-interactions at 4.2 AGeV/c

The average multiplicity of light nuclei and pi-mesons, emitted in HeC and CC interactions at 4.2 A GeV/c were studied as a function of number of identified protons. In both interactions, the behavior of average multiplicity of pi- mesons are in agreement with results coming from the Cascade model. The model could not describe the behavior of average multiplicity of light nuclei produced in HeC interactions. In case of CC interactions the model could describe qualitatively the behavior of the average multiplicity of light nuclei. An essential deviation was observed in some of the most central events. We believe that nuclear coalescence effect may be a reason of this deviation.

nucl-ex

Searching for the properties of nuclear matter using proton-carbon and deuteron-carbon collisions at 4.2 a gev/c

The present work reports the use of nuclear transparency effect of protons in proton and deuteron carbon interactions at 4.2 A GeV/c to get information about the states of nuclear matter. The half angle technique is used to extract the information on nuclear transparency. The results are compared with Dubna version of Cascade model. The average values of multiplicity, momentum and transverse momentum of protons are analyzed as a function of the number of identified protons in an event. We observed some evidence and trends in the data which could be considered as transparency effect. Analysis of the results shows that the leading effect is the basis of the observed transparency. Some contribution to the observed effect could be the existing short range correlations and the scaling power law s^-N, for exclusive two body hard scattering.

nucl-ex

Nuclear Transparency Effect in the Strongly Interacting Matter

We discuss that the results of study of the nuclear transparency effect in nuclear-nuclear collisions at relativistic and ultrarelativistic energies could help to extract the information on new phases of the strongly interacting matter as well as the QCD critical point. The results could provide further confirmation of the existence of the "horn" effect which had initially been obtained for the ratio of average values of K+ to pi+ -mesons' multiplicity as a function of the initial energies in the NA49 SPS CERN experiment. To observe the "horn" as a function of centrality, the new more enriched experimental data are required. The data which are expected from NICA/MPD JINR and CBM GSI setups could fulfill the requirement.

nucl-ex

Nuclear Transparency in the lightest nuclear interactions

Some experimental results on nuclear transparency effect in pC- and dC-interaction at 4.2 A GeV/c (JINR Dubna) are presented. The "half angle" (θ1/2) technique was used and the particles with emission angle greater and less than θ1/2 are considered separately. The results of the experimental study have been compared with the simulation data coming from the Dubna Cascade model. The values of average multiplicity, average momentum, and average transverse momentum of charged pions and protons are analyzed as a function of the number of identified protons in an event. We observed some behaviors for the data which could be considered as some nuclear transparency effects. The lasts have been divided into three main groups depending on their probable behavior: leading effect; cascade effect; medium effect.

nucl-ex

Pseudorapidity spectra of relativistic particles emitted in the Au and Pb induced reactions at high energies

The structure of the pseudorapidity spectra of charged relativistic particles with beta > 0.7 measured in Au+Em and Pb+Em collisions at AGS and SPS energies are analyzed using Fourier transformation method and maximum entropy one. The dependences of these spectra on the number of fast target protons (g-particles) are studied. They show visually some plateau and "shoulder" which are at least three selected points on the distributions. The plateau seems wider in Pb+Em reactions. The existing of plateau is expected for the parton models. The maximum entropy method confirms the existence of the plateau and the shoulder of the distributions.

nucl-ex

Search for a Signal on Phase Transitions of Strongly Interacting Matter using the Nuclear Transparency Effect

We discuss that the results coming from the central experiments confirm the results which had been obtained for the behavior of the K+-meson's temperature behavior as a function of the energy in SPS energy range. To see the "horn" for the behavior of the ratio for average values of K+- to pi+- mesons as a function of centrality the new more rich experimental data are required. The data can be obtained with NICA/MPD setup. The existing of the QCD critical point could be identified by using the nuclear transparency effect as a function of the centrality.

nucl-ex

Comparison of experimental and theoretical results to define centrality of heavy ion collisions

Using the simulation data coming from the cascade model, we have studied the behavior of event number as a function of impact parameter-b and a number of all charged particles- Nch for light and heavy nuclei at different energies. We have seen that for light nuclei, a number of all charged particles-Nch could be used to fix the centrality. But for heavy nuclei we have got strong initial energy and mass dependences and the results for impact parameter factor dependences and ones for a number of all charged particles differ. So for heavy nuclei, a number of charged particles-Nch could not be use to fix the centrality. Key words: cascade model; centrality, light nuclei, heavy nuclei

nucl-ex

Some properties of the central heavy ion collisions

Some experimental results are discussed in connection with the properties of the central heavy ion collisions. These experiments indicate the regime changes and saturation at some values of the centrality. This phenomenon is considered to be a signal of the percolation cluster formation in heavy ion collisions at high energies. Keywords: heavy ion collisions, theoretical models, centrality, phase transition.

nucl-ex

Light nuclei production in heavy ion collisions

Light nuclei production as a result of nuclear coalescence effect can give some signals on final state of Quark Gluon Plasma formation. We are studying the behavior of nuclear modification factor as a function of different variables using the simulated data coming from the FASTMC generator. This data is necessary to extract information on coalescence mechanism from experimental data on high energy nuclear-nuclear interactions.

nucl-ex

Study of the behavior of the nuclear modification factor in freeze-out state

We have studied the behaviour of the nuclear modification factor as a function of centrality, chemical baryon potential and thermal freeze out temperature using the data coming from the Fast Hadron Freezeout Generator. Considering two ways of NMF definition, namely the ratio of meson yields and ratio of baryons yield, we considered two associates effects (for percolation cluster formation) to identify it; appearance of the anomalous nuclear transparency and light nuclei production. In this paper we have used the behaviour of nuclear modification factor as a function of different physical parameters to get the information of the behavior of nuclear transparency effect and the nuclear coalescence in freezeout state. We have chosen different generators for this purpose. Here we have used the simulated data for Au-Au collisions at RHIC energies coming from the FASTMC Model. This model is very good in freezeout state.

nucl-ex

Quality assurance for the ALICE Monte Carlo procedure

We implement the already existing macro,$ALICE_ROOT/STEER /CheckESD.C that is ran after reconstruction to compute the physics efficiency, as a task that will run on proof framework like CAF. The task was implemented in a C++ class called AliAnalysisTaskCheckESD and it inherits from AliAnalysisTaskSE base class. The function of AliAnalysisTaskCheckESD is to compute the ratio of the number of reconstructed particles to the number of particle generated by the Monte Carlo generator.The class AliAnalysisTaskCheckESD was successfully implemented. It was used during the production for first physics and permitted to discover several problems (missing track in the MUON arm reconstruction, low efficiency in the PHOS detector etc.). The code is committed to the SVN repository and will become standard tool for quality assurance.

hep-ex