In this paper, the properties of Quark–Gluon Plasma (QGP) are investigated by studying the production rate of diphotons as a function of their invariant mass. Since diphotons are non-interactive constituents and carry information from initial phase to final phase, they are treated as a special probe. The current work is an extension of Kumar et al. [Phys. Scr. 96, 124060 (2021)], in which thermal quark mass is utilized. Considering parton’s thermal interactions, we use a phenomenological quasi-particle approach which combines a thermally generated mass, the current mass, and a term connecting the two, which is used as effective quark mass. The effective quark mass replaces the role of the thermal quark mass, and the resulting diphoton production rate spectra are in good agreement with those obtained in previous theoretical studies. The model results serve as a benchmark for evaluating diphoton yields across different quasi-particle treatments. Therefore, the modified quasi-particle model does not invalidate the calculation of the diphoton production rate and helps us better understand the evolution of the QGP through its electromagnetic signals by providing a framework for studying experimental data from heavy-ion collisions at RHIC and the LHC. Abstract Published by the Jagiellonian University 2026 authors
We examine spin-polarized Strange Quark Matter and the complex structure of Strange Quark Stars in the existence of a strong magnetic field. Our framework uses a quasiparticle model, en hanced by a QCD-informed effective quark mass dependent on both chemical potential value and magnetic field strength. The resulting Equation of State yields an energy per baryon below the iron limit, supporting the hypothesis that the actual ground state of matter is strange matter. The Tolman-Oppenheimer-Volkoff expressions are solved and find that the maximum stellar mass decreases with the degree of spin polarization, reaching as high as 2.35 Mo with a related radius 12.33 km. Furthermore, the model predictions for mass, radius, and surface redshift are in excel lent conformance to observational limitations for the massive pulsar PSR J0952-0607. These results highlight the crucial role of quasiparticle medium effects and strong magnetic fields in describing dense matter.
We develop a unified microcanonical formulation for \(N\) noninteracting particles with an arbitrary number \(p\) of equally spaced local energy levels, \(0,\varepsilon ,2\varepsilon ,\dots ,(p-1)\varepsilon \). The exact microcanonical multiplicity is expressed as a coefficient of a local generating function, providing a finite-\(N\) representation that can also be systematically analyzed in the thermodynamic limit. By converting this coefficient extraction into a contour integral and applying saddle-point analysis, we obtain analytical expressions for the entropy per particle \(s(u,p)\) and the inverse temperature \(\beta (u,p)\), where \(u=E/(N\varepsilon )\in \left [ 0,p-1\right ] \). The main result is a single arbitrary-\(p\) solution that contains the two-level and three-level systems as special cases and connects them continuously to the unbounded limit \(p\rightarrow \infty \). For every finite \(p\), the upper spectral bound produces an entropy maximum at \(u_\mathrm {c}=(p-1)/2\), where the inverse temperature vanishes and the positive-temperature branch changes into a negative-temperature branch. As \(p \) increases, this characteristic energy is displaced toward higher values, and in the limit \(p\rightarrow \infty \) the upper bound is removed, the finite-energy entropy maximum disappears, and only positive temperatures remain. The formulation therefore provides an analytically controlled description of the crossover between bounded- and unbounded-spectrum thermodynamics. Beyond the present model, the method supplies an exact microcanonical template for discrete additive systems whose local spectra can be encoded by generating functions, including finite-level quantum and spin systems. Abstract Published by the Jagiellonian University 2026 authors
Precise determination of the \(^{89m}\)Y isomeric half-life is critical for nuclear structure models and activation analysis. However, historical measurements exhibit a long-standing, unresolved scatter. With the present work, we aim to resolve this statistical tension by introducing a high-resolution low-background half-life measurement and evaluating historical dataset. The \(^{89m}\)Y half-life was measured by using the high-energy resolution HPGe detectors of RoSphere. Statistical analysis was performed on the \(909\gamma (t)\) data, obtained in 11 independent measurements. This dataset is highly consistent, displaying a near-ideal reduced chi-squared (\(\chi ^2\)/n.d.f.) of 0.91. Conversely, the statistical analysis, performed on the historical data, reveals some extreme statistical discrepancies. Grouping the measurements by detection methodology confirms a systematic 188 ms bias between the NaI(Tl) and HPGe data. The new measurement and statistical analysis performed in the present study do not disagree with the most precise measurement of 15.663 (5) s for the \(^{89m}\)Y half-life previously measured in 1995. Half-life of 15.61 (4) s was evaluated by applying the Rajeval technique on all available HPGe data. Abstract Published by the Jagiellonian University 2026 authors
In our previous studies, we calculated the cross-section for the production of free μ^+μ^- pairs using a probability function dependent on the impact parameter, and also, we computed bound-free e^+e^- pair production cross section. In this study, unlike the others, we obtained the cross section for the production of bound-free e^+e^- pairs using the probability function dependent on the impact parameter. Here also, we simultaneously calculated the cross sections for producing free μ^+μ^- with bound-free e^+e^- pairs in relativistic Pb+Pb collisions at the LHC with Lorentz factors at γ=1500 and γ=3000 reported in the literature. Our calculation is based on second-order perturbation theory, implemented by using Monte Carlo integration techniques. We present impact parameter dependent pair production probabilities for free μ^+μ^- and bound-free e^+e^- pair production processes. Notably, the bound-free e^+e^- pair production was evaluated by using a formalism adapted from that of free μ^+μ^- pair production. Our results obtained here for the free μ^+μ^- with bound-free e^+e^- pair production cross sections are compared with those from other theoretical methods available in the literature. This study aims to provide predictions that can be tested against future experimental data, thereby offering a valuable check for quantum electrodynamics (QED) in strong electromagnetic fields.
