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M. Shahid

Publications and source records attributed to M. Shahid.

4 recordsLinked to original sources

Impact of nuclear deformation on particle production in $Ne+Ne$ collisions at \texorpdfstring{\five}{sqrt(sNN)=5.36 TeV} from AMPT-SM

We present a systematic study of particle production in $Ne+Ne$ collisions at $\sqrt{s_{\mathrm{NN}}} = 5.36$ TeV using the A Multi-Phase Transport (AMPT) model with string melting (SM) configuration. The analysis compares spherical and deformed configurations of ${}^{20}\mathrm{Ne}$ to investigate the influence of initial-state nuclear deformation on bulk observables. Charged-particle pseudorapidity ($\langle dN_{\mathrm{ch}}/d\eta \rangle$) densities, identified particle yields ($dN/dy$), transverse momentum ($p_T$) spectra, mean transverse momentum ($\langle p_{\mathrm{T}} \rangle$), and $p_{\mathrm{T}}$-differential particle ratios ($K/\pi$ and $p/\pi$) are studied as functions of multiplicity and centrality. The results show that all observables exhibit the expected dependence on event activity, including smooth multiplicity scaling, mass ordering in $\langle p_{\mathrm{T}} \rangle$, and characteristic features associated with radial flow and quark coalescence. Differences between the two configurations on bulk observables remain small across all observables, typically at the level of a 2\%--6\% percent, with slightly enhanced sensitivity observed in peripheral collisions. These findings suggest that, within the AMPT-SM framework, the collective dynamics and hadrochemical composition are primarily governed by the overall system density and interaction dynamics, while the influence of initial-state deformation is subleading. This study provides a baseline for understanding deformation effects in light-ion collision systems and highlights the limited sensitivity of bulk observables to initial nuclear geometry in transport-based approaches.

hep-ph

Methane and oxygen from energy-efficient, low temperature in situ resource utilization enables missions to Mars

NASA mandate is a human mission to Mars in the 2030s and sustained exploration of Mars requires in-situ resource utilization (ISRU). Exploiting the Martian water cycle (alongside perchlorate salts that depress the freezing point of water to less than 213K) and the available 95 volume percent atmospheric CO2, we detail an ultra-low temperature (255K) CO2-H2O electrolyzer to produce methane fuel and life-supporting oxygen on Mars. Methane production is thermodynamically favored across a range of operational pressures and temperatures and our electrolyzer polarization model concurred with reported experimental performance. A hypothetical 10-cell, 100 square cm electrode-area-per-cell electrolyzer produced 0.31g per W per day of CH4 and 3.54g per W per day of O2 at 2V per cell (operating voltage) versus 0.8g per W per day of O2 produced by the Mars Oxygen in-situ Resource Utilization Experiment (MOXIE) from the Mars 2020 mission (MOXIE produces no fuel). Material performance requirements are presented to show that this technology is an energy-efficient complement to the MOXIE high temperature approach.

physics.chem-ph

Multigrid preconditioning of singularly perturbed convection-diffusion equations

Boundary value problems based on the convection-diffusion equation arise naturally in models of fluid flow across a variety of engineering applications and design feasibility studies. Naturally, their efficient numerical solution has continued to be an interesting and active topic of research for decades. In the context of finite-element discretization of these boundary value problems, the Streamline Upwind Petrov-Galerkin (SUPG) technique yields accurate discretization in the singularly perturbed regime. In this paper, we propose efficient multigrid iterative solution methods for the resulting linear systems. In particular, we show that techniques from standard multigrid for anisotropic problems can be adapted to these discretizations on both tensor-product as well as semi-structured meshes. The resulting methods are demonstrated to be robust preconditioners for several standard flow benchmarks.

math.NA

Effects of quantum statistical pressure and exchange correlation on the low frequency electromagnetic waves in degenerate Fermi-Dirac pair-ion plasma

The low frequency, long wavelength electromagnetic waves, viz, shear Alfven wave in quantum electron-positron-ion magneto plasmas, have been examined using quantum magneto hydrodynamic model. In this model, we have considered electrons and positrons are to be magnetized as well as degenerate whereas ions are magnetized but classical. We have also included the effects of exchange correlation terms which appear entirely the dynamic equations of electrons and positrons. The whole treatment is done using multi-fluid model. Our object is to study the shear Alfvén waves propagating in above said system of plasma. For that we have derived the modified dispersion relation of the shear Alfvén waves. Results are relevant to the terrestrial laboratory astrophysics.

physics.plasm-ph