arXiv subjects

Natasha Sharma

Publications and source records attributed to Natasha Sharma.

At least 19 recordsLinked to original sources

arXiv2026

Minimizers for the Cahn-Hilliard energy functional with the Flory-Huggins potential under strong anchoring conditions

In this paper, we theoretically and numerically study the minimizers for the Cahn-Hilliard energy with the Flory-Huggins potential under the strong anchoring condition, i.e., the Dirichlet boundary condition. We reveal bifurcation phenomena mediated by the boundary condition, the transition layer thickness, and the temperature of the system. Numerical simulations are also presented to approximate the minimizers of this energy by solving a gradient-flow equation, namely the Allen-Cahn equation constrained with strong anchoring conditions and random initial data. The effects of varying the transition layer thickness and temperature are presented to confirm the theoretical analysis.

math.AP↗

arXiv2026

More uses for Thermal Models

We explore combinations of particle and anti-particle yields which can be used to test thermal models in a parameter free way. We also explore combinations which can be used to extract $\mu_B/T$, $\mu_S/T$ and $\mu_Q/T$. We use experimentally measured particle-antiparticle specific ratios for proton $p$, Lambda $\Lambda$, and cascade $\Xi$, for $\sqrt{s_{NN}}=$ 7.7-39 GeV from RHIC BES phase-1 to extract the $\mu_{B,S,Q}/T$. These compared well with published STAR freeze-out parameters. These combinations are verified to predict a similar combination of $\Omega$ yields. We also extend this idea to predict (anti-)nuclei yields at energies where they are not measured. We also update parametrizations for the $\sqrt{s_{NN}}$ dependence of freeze-out parameters $T$ and $\mu_B$, and present for the first time a similar parametrization of $\mu_S$.

hep-ph↗

arXiv2025

Canonical treatment of strangeness and light nuclei production

The canonical effects on strangeness and light nuclei production in high energy collisions are investigated, with a particular focus on low multiplicity events observed in small collision systems at the Large Hadron Collider (LHC), and also in low energy collisions at the Relativistic Heavy Ion Collider (RHIC). We analyzed the yields of various particles, such as pions, protons, lambdas, multi-strange hadrons and light nuclei, and their dependencies on the produced charged particle multiplicities using the Statistical Hadronization Model (SHM). Our findings indicate that the canonical treatment of strange and baryon quantum numbers are essential for describing the particle production in these collisions, particularly in small collision systems.

hep-ph↗

arXiv2024

Transport coefficients of the heavy quark in the domain of the non-perturbative and non-eikonal gluon radiation

Drag and diffusion coefficients of the Heavy Quarks (HQs), such as charm and bottom, are one of the prime tools for discerning the properties of the deconfined QCD medium created in the Heavy Ion Collisions experiments. The innate non-perturbative nature of the QCD medium renders it imperative to estimate the transport coefficients in that domain. The present work evaluates the drag and diffusion coefficients of the moving HQ interacting with the medium particles via two-body collisional and three-body radiative processes to the first order in opacity by employing Gribov mechanism for the non-perturbative regime. We proffer the latest results of the HQ transport coefficients computed for the non-perturbative and non-eikonal gluon radiation off the HQ. The calculations show significant increment of the transport coefficients with the increasing non-eikonality by juxtaposing the results with those of the pertubative and eikonal regions. We hope to shed fresh light towards explaining the experimental data on the nuclear modification facor, $R_{AA}$, the elliptic flow, $v_2$ of the HQ by advocating the importance of the non-eikonality of the gluon radiation off the HQ.

hep-ph↗

arXiv2024

Emergence of New Systematics for Open Charm Production in High Energy Collisions

We present the production systematics of open charm hadron yields in high-energy collisions and their description based on the Statistical Hadronization Model of charm (SHMc). The rapidity density of $D^0, D^+, D^{*+}, D_s^+$ mesons and $\Lambda_c^+$ baryons in heavy ion and proton-proton collisions is analyzed for different collision energies and centralities. The SHMc is extended to open charm production in minimum-bias and high-multiplicity pp collisions. In this context, we use the link established in [1,2], between the rapidity density of open charm hadron yields, $dN_i/dy$, and the rapidity density of charm-anticharm quark pairs, $dN_{c\bar c}/dy$. We demonstrate that, in pp, pA and AA collisions, $dN_i/dy$ scales in leading order with $dN_{c\bar c}/d\eta$ and for open charm mesons, $D^0,D^+$ and $D^{*+}$ the slope coefficient is quantified by the appropriate thermal density ratio calculated in the SHMc at the chiral crossover temperature, $T_c=156.5$ MeV. The slope coefficient for $dN_{\Lambda_c^+}/dy$ differs at $T_c$ by a factor of $1.97\pm 0.14$ which is attributed to missing charmed-baryon resonances in the PDG. It is also shown that $dN_i/dy$ exhibits power-law scaling with the charged-particle pseudo-rapidity density in high energy collisions and within uncertainties. Furthermore, presently available data on different ratios of open charm rapidity densities in high-energy collisions are independent of collision energy and system size, as expected in the SHMc.

hep-ph↗

arXiv2023

Light nuclei production in pp and pA collisions in the Baryon Canonical Ensemble

The increase in yields of light nuclei with charged particle multiplicity, as reported by the ALICE collaboration at CERN in p-p and p-Pb collisions at the LHC energy is investigated in the thermal hadron resonance gas model. The model is extended to account for exact baryon number conservation. The focus is on the production of protons, deuterons, $^3$He, and $^3_Λ$H. A very good description of proton and deuteron yields is obtained as a function of charged particle multiplicity in the mid-rapidity region using the same fixed temperature as in central Pb-Pb collisions. The yields of light nuclei $^3$He and $^3_Λ$H though qualitatively explained as a function of multiplicity, are lower than the model expectation. One of the possible reasons could be that for $^{3}$He and $^{3}_Λ$H, the chemical equilibrium is not yet reached at small multiplicities.

nucl-th↗

arXiv2022

A C0 Interior Penalty Method for the Phase Field Crystal Equation

We present a C0 interior penalty finite element method for the sixth-order phase field crystal equation. We demonstrate that the numerical scheme is uniquely solvable, unconditionally energy stable, and convergent. We remark that the novelty of this paper lies in the fact that this is the first C0 interior penalty finite element method developed for the phase field crystal equation. Additionally, the error analysis presented develops a detailed methodology for analyzing time dependent problems utilizing the C0 interior penalty method. We furthermore benchmark our method against numerical experiments previously established in the literature.

math.NA↗

arXiv2022

Exact strangeness conservation in heavy ion collisions

We investigate the increase in strangeness production with charged particle multiplicity ($dN_{ch}/dy$) seen by the ALICE collaboration at CERN in p-p, p-Pb and Pb-Pb collisions using the hadron resonance gas model. The strangeness canonical ensemble is used taking into account the interactions among hadrons using S-matrix corrections based on known phase shift analyses. We show the essential role of constraints due to the exact conservation of strangeness which is instrumental to describing observed features of strange particle yields and their scaling with $dN_{ch}/dy$. Furthermore, the results on comparing the hadron resonance gas model with and without S-matrix corrections, are presented. We observe that the interactions introduced by the phase shift analysis via the S-matrix formalism are essential for a better description of the yields data independent of collision system. This work is based on our long-lasting collaboration and most recent publications with Jean Cleymans.

hep-ph↗

arXiv2021

Robust a-posteriori error estimates for weak Galerkin method for the convection-diffusion problem

We present a robust a posteriori error estimator for the weak Galerkin finite element method applied to stationary convection-diffusion equations in the convection-dominated regime. The estimator provides global upper and lower bounds of the error %measured in a suitable norm and is robust in the sense that upper and lower bounds are uniformly bounded with respect to the diffusion coefficient. Results of the numerical experiments are presented to illustrate the performance of the error estimator.

math.NA↗

arXiv2021

Hadronic Resonance Gas Model and Multiplicity Dependence in p-p, p-Pb, Pb-Pb collisions: Strangeness Enhancement

Recently the ALICE collaboration has observed an interesting systematic behaviour of ratios of identified particles to pions yields at the LHC, showing that they depend solely on the charged-particle multiplicity in pp, pPb and PbPb collisions. In particular, the yields of (multi)strange particles relative to pions, increases with multiplicity and the enhancement is mode pronounced with increasing strangeness content. We will argue, that such a pattern of arises naturally in the thermal model taking into account exact strangeness conservation. Furthermore, extending the thermal model by including hadron interactions within the S-matrix approach, the ALICE data can be well quantified by the thermal particle yields at the chiral-crossover temperature, as previously found in central Pb-Pb collisions.

hep-ph↗

arXiv2020

Multiplicity dependence of (multi-)strange baryons in the canonical ensemble with phase shift corrections

The increase in strangeness production with charged particle multiplicity, as seen by the ALICE collaboration at CERN in p-p, p-Pb and Pb-Pb collisions, is investigated in the hadron resonance gas model taking into account interactions among hadrons using S-matrix corrections based on known phase shift analyses. Strangeness conservation is taken into account in the framework of the canonical strangeness ensemble. A very good description is obtained for the variation of the strangeness content in the final state as a function of the number of charged hadrons in the mid-rapidity region using the same fixed temperature value as obtained in the most central Pb-Pb collisions. It is shown that the number of charged hadrons is linearly proportional to the volume of the system. For small multiplicities the canonical ensemble with local strangeness conservation restricted to mid-rapidity leads to a stronger suppression of (multi-)strange baryons than seen in the data. This is compensated by introducing a global conservation of strangeness in the whole phase-space which is parameterized by the canonical correlation volume larger than the fireball volume at the mid-rapidity. The results on comparing the hadron resonance gas model with and without S-matrix corrections, are presented in detail. It is shown that the interactions introduced by the phase shift analysis via the S-matrix formalism are essential for a better description of the yields data.

hep-ph↗

arXiv2020

Constraining the Particle Production Mechanism in Au+Au Collisions at $\sqrt{s_{NN}}=$ 7.7, 27, and 200 GeV Using A Multi Phase Transport Model

We study the production of pions, kaons, and (anti)protons in A Multi Phase Transport (AMPT) Model in Au+Au collisions at $\sqrt{s_{NN}}=$ 7.7, 27, and 200 GeV. We present the centrality and energy dependence of various bulk observables such as invariant yields as a function of transverse momentum $p_T$, particle yields $dN/dy$, average transverse momentum $\langle p_T \rangle$, and various particle ratios, and compare them with experimental data. Both default and string melting (SM) versions of the AMPT model are used with three different sets of initial conditions. We observe that neither the default nor the SM version of the model could consistently describe the centrality dependence of all observables at the above energies with any one set of initial conditions. The energy dependence behavior of the experimental observables for 0--5\% central collisions is in general better described by the default AMPT model using the modified HIJING parameters for Lund string fragmentation and 3mb parton scattering cross-section. In addition, the kaon production as well as the $K/π$ ratio at 7.7 GeV are under predicted by the AMPT model.

hep-ph↗

arXiv2018

A Comparison of p-p, p-Pb, Pb-Pb Collisions in the Thermal Model: Multiplicity Dependence of Thermal Parameters

% An analysis is made of the particle composition (hadrochemistry) of the final state in proton-proton (p-p), proton-lead (p-Pb) and lead-lead (Pb-Pb) collisions as a function of the charged particle multiplicity ($\dNchdeta$). The thermal model is used to determine the chemical freeze-out temperature as well as the radius and strangeness saturation factor $γ_s$. Three different ensembles are used in the analysis namely, the grand canonical ensemble, the canonical ensemble with exact strangeness conservation and the canonical ensemble with exact baryon number, strangeness and electric charge conservation. It is shown that for high multiplicities (at least 20 charged hadrons in the mid-rapidity interval considered) the three ensembles lead to the same results.

hep-ph↗

arXiv2018

A Contraction Property of an Adaptive Divergence-Conforming Discontinuous Galerkin Method for the Stokes Problem

We prove the contraction property for two successive loops of the adaptive algorithm for the Stokes problem reducing the error of the velocity. The problem is discretized by a divergence-conforming discontinuous Galerkin method which separates pressure and velocity approximation due to its cochain property. This allows us to establish the quasi-orthogonality property which is crucial for the proof of the contraction. We also establish the quasi-optimal complexity of the adaptive algorithm in terms of the degrees of freedom.

math.NA↗

arXiv2018

Thermodynamic limit in high-multiplicity $pp$ collisions at $\sqrt{s}$ = 7 TeV

An analysis is made of the particle composition in the final state of $pp$ collisions at 7 TeV as a function of the charged particle multiplicity ($dN_{ch}/dη$). The thermal model is used to determine the chemical freeze-out temperature as well as the radius and strangeness suppression factor $γ_s$. Three different ensembles are used in the analysis. The grand canonical ensemble, the canonical ensemble with exact strangeness conservation and the canonical ensemble with exact baryon number, strangeness and electric charge conservation. It is shown that for the highest multiplicity class the three ensembles lead to the same result. This allows us to conclude that this multiplicity class is close to the thermodynamic limit. It is estimated that the final state in $pp$ collisions could reach the thermodynamic limit when $dN_{ch}/dη$ is larger than twenty per unit of rapidity, corresponding to about 300 particles in the final state when integrated over the full rapidity interval.

hep-ph↗

arXiv2018

Review of (anti-)Nuclei Production from High Energy Experiments

An overview of nuclei and anti-nuclei production with results from different experiments are discussed. The comparison of data with the thermal and coalescence models is also discussed to understand their production mechanisms in high energy collisions.

hep-ex↗

arXiv2018

Methods for separation of deuterons produced in the medium and in jets in high energy collisions

Coalescence has long been used to describe the production of light (anti-)nuclei in heavy ion collisions. The same underlying mechanism may also exist in jets when a proton and a neutron are close enough in phase space to form a deuteron. We model deuteron production in jets by applying an afterburner to protons and neutrons produced in PYTHIA for $p$+$p$ collisions at a center of mass energy $\sqrt{s} =$ 7 TeV. PYTHIA provides a reasonable description of the proton spectra and the shape of the deuteron spectrum predicted by the afterburner is in agreement with the data. We show that the rise in the coalescence parameter $B_2$ with momentum observed in data is consistent with coalescence in jets. We show that di-hadron correlations can be used to separate the contributions from the jet and the underlying event. This model predicts that the conditional coalescence parameter in the jet-like correlation should be independent of the trigger momentum.

hep-ph↗

arXiv2018

Thermal Model Description of p--Pb Collisions at $\sqrt{s_{NN}} $ = 5.02 TeV

The ALICE data on light flavor hadron production obtained in $p-Pb$ collisions at $\sqrt{s_{NN}} $ = 5.02 TeV are studied in the thermal model using the canonical approach with exact strangeness conservation. The chemical freeze-out temperature is independent of centrality except for the lowest multiplicity bin, with values close to 160 MeV but consistent with those obtained in $Pb-Pb$ collisions at $\sqrt{s_{NN}}$ = 2.76 TeV. The value of the strangeness non-equilibrium factor $γ_s$ is slowly increasing with multiplicity from 0.9 to 0.96, i.e. it is always very close to full chemical equilibrium.

hep-ph↗