arXiv subjects

Subhash Singha

Publications and source records attributed to Subhash Singha.

25 records · Page 2Linked to original sources

arXiv2016

The first moment of azimuthal anisotropy in nuclear collisions from AGS to LHC energies

We review topics related to the first moment of azimuthal anisotropy ($v_1$), commonly known as directed flow, focusing on both charged particles and identified particles from heavy-ion collisions. Beam energies from the highest available, at the CERN LHC, down to projectile kinetic energies per nucleon of a few GeV per nucleon, as studied in experiments at the Brookhaven AGS, fall within our scope. We focus on experimental measurements and on theoretical work where direct comparisons with experiment have been emphasized. The physics addressed or potentially addressed by this review topic includes the study of Quark Gluon Plasma, and more generally, investigation of the Quantum Chromodynamics phase diagram and the equation of state describing the accessible phases.

nucl-ex↗

arXiv2016

Scaling of elliptic flow in heavy-ion collisions with the number of constituent quarks in a transport model

We studied the number of constituent quark scaling (NCQ) behaviour of elliptic flow ($v_{2}$) under the framework of A Multi-Phase Transport model (AMPT) at both top-RHIC and LHC energies. The NCQ-scaling in $v_{2}$ holds at top-RHIC energy with AMPT string melting version, while it breaks in Pb+Pb collisions at LHC energy using the same framework. The breaking of NCQ-scaling at LHC energy has been studied by varying the magnitude of parton-parton scattering cross-section and lifetime of hadronic cascade as implemented in AMPT. We find that the breaking of NCQ scaling in Pb+Pb collisions at $\sqrt{s_{NN}}$ =2.76 TeV is independent of the magnitude of parton-parton cross-section and the later stage hadronic interactions. Further we observed that scaling holds in a small collision system like Si+Si at $\sqrt{s_{NN}}$ = 2.76 TeV. We discussed that the breaking of NCQ scaling is possibly due to high phase-space density of constituents quarks in Pb+Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV.

nucl-ex↗

arXiv2016

Uniting Superhydrophobic, Superoleophobic and Lubricating Fluid Infused Slippery Behavior on Copper Oxide Nano-structured Substrates

Copper oxide nanostructures with spherical (0D), needle (1D) and hierarchical cauliflower (3D) morphologies are used to demonstrate superhydrophobic, superoleophobic and slippery behavior. These nanostructures are synthesized on galvanized steel substrates using a simple chemical bath deposition method by tuning precursor concentration. Subsequent coating of low surface energy polymer, polydimethylsiloxane, results in superhydrophobicity with water contact angle ~160(2)° and critical sliding angle ~2°. When functionalized with low-surface energy perfluoroalkyl silane, these surfaces display high repellency for low surface tension oils and hydrocarbons. Among them, the hierarchical cauliflower morphology exhibits better re-entrant structure thus show the best superoleophobicity with 149° contact angle for dodecane having surface tension 25.3 mNm-1. If these nanostructured substrates are infused with lubricant Silicone oil, they show excellent slippery behavior for water drops. Due to the lubricating nature of Silicone oil, the Silicone oil infused slippery surfaces (SOIS) show low contact angle hysteresis (~2°) and critical tilt angle (~2°). The hierarchical cauliflower nanostrcuture exhibit better slippery characteristics and stability compared to the other nanostructured surfaces.

cond-mat.soft↗

arXiv2015

Studying re-scattering effect in heavy-ion collision through $K^*$ Production

We have studied the $K^*$ production within A Multi-Phase Transport model (AMPT) for Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV to understand the hadronic re-scattering effect on the measured yields of the resonance. The hadronic re-scattering of the $K^*$ decay daughter particles ($π$ and K) will alter their momentum distribution thereby making it difficult to reconstruct the $K^*$ signal through the invariant mass method. An increased hadronic re-scattering effect thus leads to a decrease in the reconstructed yield of $K^*$ in heavy-ion collisions. Through this simulation study we argue that a decrease in $K^*$/K ratio with increase in collision centrality necessarily reflects the hadronic re-scattering effect. Since the re-scattering occurs in the hadronic phase and $K^*$ has a lifetime of 4 fm/c, we present a toy model based discussion on using measured $K^*$/K to put a lower limit on the hadronic phase lifetime in high energy nuclear collisions.

nucl-ex↗

arXiv2013

Hadronic Resonance Production with ALICE Experiment at LHC

The production of resonances in heavy-ion collisions is expected to be sensitive to the properties of strongly interacting matter created in such collisions. We report on the measurements of $ϕ$ and $K^{*0}$ resonances in Pb-Pb collisions at $\sqrt{s_{NN}} $ = 2.76 TeV. The masses, widths and yields in Pb-Pb collisions as a function of centrality are compared to that in pp collisions to understand the role of re-scattering and regeneration. The resonance to non-resonance particle ratios are shown as a function of collision centrality and compared with the results at lower energies.

hep-ex↗

arXiv2012

Strange hadron and resonance production in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV with ALICE experiment at LHC

The ALICE experiment at the LHC has measured the production of strange hadrons and resonances in Pb-Pb and pp collisions at unprecedented high beam energies. The study of strange hadrons and resonances helps us to understand the properties of the medium created in the heavy-ion collisions and its evolution. We present the yields ($dN/dy$) at mid-rapidity for strange hadrons ($Λ$, $Ξ^{-}$, $Ω^{-}$, their anti-particles and $K_{S}^{0}$) and resonances ($ϕ$ and $K^{*0}$) for several collision centrality intervals. The results from Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV are presented and compared to corresponding results from pp collisions and lower energy measurements. Baryon to meson ratios and resonance to non-resonance particle ratios relative to pp collisions are shown as a function of collision centrality and compared with the results at lower energies.

hep-ex↗

arXiv2010

Energy dependence of pbar/p ratio in p+p collisions

We have compiled the experimentally measured pbar/p ratio at midrapidity in p+p collisions from \sqrt{s} = 23 to 7000 GeV and compared it to various mechanisms of baryon production as implemented in PYTHIA, PHOJET and HIJING/B-Bbar models. For the models studied with default settings, PHOJET has the best agreement with the measurements, PYTHIA gives a higher value for \sqrt{s} < 200 GeV and the ratios from HIJING/B-Bbar are consistently lower for all the \sqrt{s} studied. Comparison of the data to different mechanisms of baryon production as implemented in PYTHIA shows that through a suitable tuning of the suppression of diquark-antidiquark pair production in the color field relative to quark-antiquark production and allowing the diquarks to split according to the popcorn scheme gives a fairly reasonable description of the measured pbar/p ratio for \sqrt{s} < 200 GeV. Comparison of the beam energy dependence of the pbar/p ratio in p+p and nucleus-nucleus (A+A) collisions at midrapidity shows that the baryon production is significantly more for A+A collisions relative to p+p collisions for \sqrt{s} < 200 GeV. We also carry out a phenomenological fit to the y_beam dependence of the pbar/p ratio.

nucl-ex↗