Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userDeconfinement and degrees of freedom in $pp$ and $A-A$ collisions at LHC energies
161
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We present the extraction of the temperature by analyzing the charged particle transverse momentum spectra in lead-lead (Pb-Pb) and proton-proton (${bf pp}$) collisions at LHC energies from the ALICE Collaboration using the Color String Percolation Model (CSPM). From the measured energy density ${bm varepsilon}$ and the temperature T the dimensionless quantity ${bm varepsilon/}T^{4}$ is obtained to get the degrees of freedom (DOF), ${bm varepsilon}/T^{4}$ = DOF ${ pi^{2}}$/30. We observe for the first time a two-step behavior in the increase of DOF, characteristic of deconfinement, above the hadronization temperature at temperature $sim$ 210 MeV for both Pb-Pb and ${bf pp}$ collisions and a sudden increase to the ideal gas value of $sim $ 47 corresponding to three quark flavors in the case of Pb-Pb collisions.
rate research
Read More
We have performed a systematic study of $J/psi$ and $psi(2S)$ production in $p-p$ collisions at different LHC energies and at different rapidities using the leading order (LO) non-relativistic QCD (NRQCD) model of heavy quarkonium production. We have included the contributions from $chi_{cJ}$ ($J$ = 0, 1, 2) and $psi(2S)$ decays to $J/psi$. The calculated values have been compared with the available data from the four experiments at LHC namely, ALICE, ATLAS, CMS and LHCb. In case of ALICE, inclusive $J/psi$ and $psi(2S)$ cross-sections have been calculated by including the feed-down from $B$ meson using Fixed-Order Next-to-Leading Logarithm (FONLL) formalism. It is found that all the experimental cross-sections are well reproduced for $p_T >$ 4 GeV within the theoretical uncertainties arising due to the choice of the factorization scale. We also predict the transverse momentum distributions of $J/psi$ and $psi(2S)$ both for the direct and feed-down processes at the upcoming LHC energies of $sqrt{s} =$ 5.1 TeV and 13 TeV for the year 2015.
The Quark Gluon String Model (QGSM) reproduces well the global characteristics of the $pp$ collisions at RHIC and LHC, e.g., the pseudorapidity and transverse momenta distributions at different centralities. The main goal of this work is to employ the Monte Carlo QGSM for description of femtoscopic characteristics in $pp$ collisions at RHIC and LHC. The study is concentrated on the low multiplicity and multiplicity averaged events, where no collective effects are expected. The different procedures for fitting the one-dimensional correlation functions of pions are studied and compared with the space-time distributions extracted directly from the model. Particularly, it is shown that the double Gaussian fit reveals the contributions coming separately from resonances and from directly produced particles. The comparison of model results with the experimental data favors decrease of particle formation time with rising collision energy.
A phenomenological model for the description of the single and double diffractive excitation in $pp$ collisions at high energies is presented. Considering the Good -- Walker approach, we propose a model for the eigenstates of the scattering operator and for the treatment of the interaction between them, with the high energy behavior of the cross section driven by perturbative QCD. The behavior of the total, elastic, single and double diffractive cross sections are analyzed and predictions for the energies of Run 3 of the LHC and those of the Cosmic Rays experiments are derived. We demonstrate that the model describes the current data for the energy dependence of the cross sections. A comparison with the recent data for the $rho$ parameter and the differential elastic cross section are also presented and shortcomings of the current model are discussed.
In this work we analyze the reliability of several techniques for computing jet and hadron spectra at different collision energies. This is of particular relevance for discovering energy loss in the upcoming oxygen-oxygen (OO) run at the LHC, for which a reference $pp$ run at the same energy is currently not planned. For hadrons and jets we compute the ratio of spectra between different $pp$ collision energies in perturbative QCD, which can be used to construct a $pp$ reference spectrum. Alternatively, a $pp$ reference can be interpolated from measured spectra at nearby energies. We estimate the precision and accuracy of both strategies for the spectra ratio relevant to the oxygen run, and conclude that the central values agree to 4% accuracy for hadrons and 2% accuracy for jets. As an alternative, we propose taking the ratio of OO and $pp$ spectra at different collision energies, which cleanly separates the experimental measurement from the theoretical computation.
We study multiplicity correlations of hadrons in forward and backward hemispheres in $pp$ inelastic interactions at energies 200GeV $leq sqrt{s} leq$ 13TeV 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 center-of-mass frame; (ii) the increase of the slope parameter $b_{corr}$ 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 $sqrt{s} = 13$TeV.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
