BITS Faculty Publications
Permanent URI for this communityhttp://localhost:4000/handle/123456789/1867
Browse
4 results
Search Results
Item Dynamics of QCD matter — current status(World Scientific, 2021) Das, ArpanIn this article, there are 18 sections discussing various current topics in the field of relativistic heavy-ion collisions and related phenomena, which will serve as a snapshot of the current state of the art. Section 1 reviews experimental results of some recent light-flavored particle production data from ALICE collaboration. Other sections are mostly theoretical in nature. Very strong but transient magnetic field created in relativistic heavy-ion collisions could have important observational consequences. This has generated a lot of theoretical activity in the last decade. Sections 2, 7, 9, 10 and 11 deal with the effects of the magnetic field on the properties of the QCD matter. More specifically, Sec. 2 discusses mass of π0 in the linear sigma model coupled to quarks at zero temperature. In Sec. 7, one-loop calculation of the anisotropic pressure are discussed in the presence of strong magnetic field. In Sec. 9, chiral transition and chiral susceptibility in the NJL model is discussed for a chirally imbalanced plasma in the presence of magnetic field using a Wigner function approach. Sections 10 discusses electrical conductivity and Hall conductivity of hot and dense hadron gas within Boltzmann approach and Sec. 11 deals with electrical resistivity of quark matter in presence of magnetic field. There are several unanswered questions about the QCD phase diagram. Sections 3, 11 and 18 discuss various aspects of the QCD phase diagram and phase transitions. Recent years have witnessed interesting developments in foundational aspects of hydrodynamics and their application to heavy-ion collisions. Sections 12 and 15–17 of this article probe some aspects of this exciting field. In Sec. 12, analytical solutions of viscous Landau hydrodynamics in 1+1D are discussed. Section 15 deals with derivation of hydrodynamics from effective covariant kinetic theory. Sections 16 and 17 discuss hydrodynamics with spin and analytical hydrodynamic attractors, respectively. Transport coefficients together with their temperature- and density-dependence are essential inputs in hydrodynamical calculations. Sections 5, 8 and 14 deal with calculation/estimation of various transport coefficients (shear and bulk viscosity, thermal conductivity, relaxation times, etc.) of quark matter and hadronic matter. Sections 4, 6 and 13 deal with interesting new developments in the field. Section 4 discusses color dipole gluon distribution function at small transverse momentum in the form of a series of Bells polynomials. Section 6 discusses the properties of Higgs boson in the quark–gluon plasma using Higgs–quark interaction and calculate the Higgs decays into quark and anti-quark, which shows a dominant on-shell contribution in the bottom-quark channel. Section 13 discusses modification of coalescence model to incorporate viscous corrections and application of this model to study hadron production from a dissipative quark–gluon plasma.Item Quarkonia suppression in small systems with a nonadiabatic evolution(APS, 2024-07) Das, ArpanIn high multiplicity proton-proton (𝑝−𝑝) collisions, the formation of a deconfined state of quarks and gluons akin to heavy ion collisions (HIC) has been a subject of significant interest. In proton-proton (𝑝 −𝑝) collisions, the transverse size of the system is comparable to the longitudinal (Lorentz contracted) dimension, unlike the case in a nucleus-nucleus (𝐴 −𝐴) collision, leading to a hitherto unexplored effect of rapid decrease of temperature of the medium on quark-antiquark bound states. Starting with a bottom-up thermalization framework for preequilibrium stage, we model the hydrodynamic expansion of the resulting fireball based on the Gubser flow with both inviscid theory and viscous corrections up to the third order. We find that the temperature evolution in small systems is rather fast even with viscous evolution equations for energy density, thereby introducing sudden changes in the time evolution of the Hamiltonian. This scenario prompts the consideration of nonadiabatic evolution, justifying the need in the present case to go beyond the traditional adiabatic framework. We demonstrate that nonadiabatic evolution may suppress the dissociation of 𝐽/Ψ substantially in 𝑝 −𝑝 collisions, even at higher multiplicities, offering new insights into the dynamics of strongly interacting matter produced in smaller collision systems.Item Bottom quark energy loss and hadronization with B^+ and B^0_\mathrm{s} nuclear modification factors using pp and PbPb collisions at \sqrt{s_\mathrm{NN}} = 5.02 TeV(2025) Das, ArpanThe production cross sections of B and B mesons are reported in proton-proton (pp) collisions recorded by the CMS experiment at the CERN LHC with a center-of-mass energy of 5.02 TeV. The data sample corresponds to an integrated luminosity of 302 pb . The cross sections are based on measurements of the B J/ (1020) (K K ) and B J/ K decay channels. Results are presented in the transverse momentum ( ) range 7-50 GeV/ and the rapidity interval 2.4 for the B mesons. The measured -differential cross sections of B and B in pp collisions are well described by fixed-order plus next-to-leading logarithm perturbative quantum chromodynamics calculations. Using previous PbPb collision measurements at the same nucleon-nucleon center-of-mass energy, the nuclear modification factors, , of the B mesons are determined. For 10 GeV/ , both mesons are found to be suppressed in PbPb collisions (with values significantly below unity), with less suppression observed for the B mesons. In this range, the values for the B mesons are consistent with those for inclusive charged hadrons and D mesons. Below 10 GeV/ , both B and B are found to be less suppressed than either inclusive charged hadrons or D mesons, with the B value consistent with unity. The values found for the B and B are compared to theoretical calculations, providing constraints on the mechanism of bottom quark energy loss and hadronization in the quark-gluon plasma, the hot and dense matter created in ultrarelativistic heavy ion collisions.Item Search for jet quenching with dijets from high-multiplicity pPb collisions at = 8.16 TeV(Springer, 2025-07) Das, ArpanThe first measurement of the dijet transverse momentum balance xj in proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass energy of = 8.16 TeV is presented. The xj observable, defined as the ratio of the subleading over leading jet transverse momentum in a dijet pair, is used to search for jet quenching effects. The data, corresponding to an integrated luminosity of 174.6 nb−1, were collected with the CMS detector in 2016. The xj distributions and their average values are studied as functions of the charged-particle multiplicity of the events and for various dijet rapidity selections. The latter enables probing hard scattering of partons carrying distinct nucleon momentum fractions x in the proton- and lead-going directions. The former, aided by the high-multiplicity triggers, allows probing for potential jet quenching effects in high-multiplicity events (with up to 400 charged particles), for which collective phenomena consistent with quark-gluon plasma (QGP) droplet formation were previously observed. The ratios of xj distributions for high- to low-multiplicity events are used to quantify the possible medium effects. These ratios are consistent with simulations of the hard-scattering process that do not include QGP production. These measurements set an upper limit on medium-induced energy loss of the subleading jet of 1.26% of its transverse momentum at the 90% confidence level in high multiplicity pPb events.