The European Physical Journal A最新文献

The São Paulo potential version 2 and the Brazilian nuclear potential are bare nuclear interactions obtained via a systematic procedure that derives nuclear matter densities from Dirac–Hartree–Bogoliubov calculations. In the present work, we introduce two distinct systematics based on these potentials to describe the elastic scattering of heavy nuclei, derived from the analysis of more than 300 elastic angular distributions reported in the literature. Our results demonstrate that adopting the optical potentials on the forms (V_{opt}^{SPP2}(R) = left[ 1 + i cdot 0.80(4) right] times V_{SPP2}(R)) and/or (V_{opt}^{BNP}(R) = left[ 1 + i cdot 0.77(4) right] times V_{BNP}(R)) successfully describes the experimental data for several systems for which the elastic channel in not strongly coupled to non elastic channels. It is shown that these systematics do not depend on the nuclear mass of the systems. However, a correction that depends on the projectile’s bombarding energy is required to better describe the low-energy scattering data. A brief study is also conducted comparing the three systematics for nuclei with excess neutrons relative to their most abundant form, as well as for weakly bound nuclei. The systematics obtained with the SPP2 potential appear to be slightly better than those obtained with the Brazilian nuclear potential and the former version of the São Paulo potential.

The electromagnetic decay of the (approx )40 (mu )s isomer of (^{250})No has been investigated using the Geant4 toolkit for the simulations of the interaction of particles through matter. It is concluded that the decay does not follow the pattern established in the lighter isotones, where the isomer decays directly to members of the ground state rotational band. An alternative scenario is proposed. The implications on the location of the isotopic border for neutron deficient Rf isotopes are discussed.

Dependence of forward–backward multiplicity correlations on the centrality bin width and methods of centrality selection is looked into by analysing the HYDJET++ model simulated data corresponding to Au–Au collisions at RHIC and Pb–Pb collisions at LHC energies, and the findings are compared with those reported earlier. It is observed that forward–backward multiplicity correlation strength from the soft thermal component, which arise essentially due to short-range correlations caused by the resonance decays and long-range correlations arising due to hydrodynamical particle flow, is observed to increase gradually with beam energy for all centrality classes, whereas due to the jet part, the correlation strength remains minimal at (sqrt{s_{NN}} sim ) 19 GeV for 10% central collisions which increases quickly with increasing beam energy. Such an increasing strength of the correlation with beam energy is due to growing contributions from the hard jets, particularly in the central collisions. However, for predicting the correct dependence of correlation strength on the collision centrality, contributions from both soft and hard components should be taken into account simultaneously. Furthermore, the study of (p_T) dependence of forward–backward multiplicity correlations reveals that the contribution to the correlation strength from the particles with low (p_T) ((le ) 2.0 GeV/c), resulting from the soft–hydro part of the model is essentially energy independent from (sim ) (sqrt{s_{NN}}) = 19.6 GeV to 5.02 TeV. The strong correlations observed at LHC energies are due to the large multiplicities resulting from the hard–jet part of the model, where the particles with transverse momenta up to (sim ) 4.0 GeV/c are produced in correlation.

In this paper, we perform a thermostatistical analysis of the charged particles produced in minimum bias pp collisions across different energies available at the LHC-CERN reported by the ALICE Collaboration. To this end, we adopted the normalized (p_text {T}) spectrum as the probability density function governing the (p_text {T}) microstates of the produced hadrons, from which we can compute the entropy following the Shannon definition or the average (p_text {T}) as the Bjorken-type energy estimator. Additionally, we estimate the temperature from the slope of the (p_text {T}) spectrum at low (p_text {T}) values. We use the Hagedorn and Tricomi functions to describe the (p_text {T}) spectrum within a nonextensive approach and determine consistent thermodynamic frameworks by solving the fundamental relation (dE/dT=C), where (C=TdS/dT) is the heat capacity. We found that the internal energy behaves nonlinearly at LHC energies, indicating that the count of degrees of freedom is more complex than simply adding the number of flavors present in the hadron production. The main implication of our results is that the systems produced in pp collisions depart from the ideal gas picture and explain why the production of high (p_text {T}) hadrons has always been observed, even in earlier experiments, which may also encompass other experiments colliding e(^-)p or e(^+)e(^-).

We introduce a multi-parameter rating methodology for objective comparison of theoretical models with experimental data in heavy-ion collisions, addressing fundamental limitations of the traditional global (chi ^2)/ndf criterion. Phase space is divided into seven physically motivated kinematic zones, each reflecting a distinct production mechanism from thermal freeze-out to asymptotic perturbative QCD. Each zone receives a quality score (Q_i in [10, 1000]) via logarithmic transformation of local (rho _i = chi ^2_i/nu _i) statistics. A composite rating R aggregates weighted average, geometric mean, and minimum scores with a bounded dispersion penalty, preventing artificial compensation between zones. The seven-zone boundaries are validated through significance tests on CMS Pb–Pb data at (sqrt{s_{NN}}=5.02) TeV: four of the five statistically testable boundaries are confirmed ((p < 0.05)). Sensitivity analysis confirms ranking stability: (pm 20%) coefficient variations produce (Delta R < 2%) with zero rank changes. As a proof-of-concept, the methodology is applied to digitized predictions against ALICE p–Pb data at (sqrt{s_{NN}}=5.02) TeV for (K^0_S) mesons and (Lambda ) hyperons, and to a synthetic CMS-acceptance benchmark for the (Lambda /K^0_S) ratio. The results reveal a clear model hierarchy: PHSD, incorporating microscopic QGP transport with coalescence, achieves near-universal performance ((R = 911) for (K^0_S), (R = 893) for (Lambda )), while PYTHIA8 ((R = 878)) leads in the hard-fragmentation regime. The baryon anomaly peak is the critical discriminator: coalescence models score (Q_i sim 950)–1000 in zones 3–4 versus (Q_i sim 400)–600 for pure fragmentation generators. The methodology is transparent, reproducible, algorithmic, and ready for integration into analysis frameworks.

It has been conjectured that, at sufficiently high baryon densities, the equation of state (EoS) of bulk nuclear matter can be identified with that of the nucleon core. In this work, we illustrate how the energy density and pressure distributions inside individual nucleons can be utilized to construct the EoS of supra-dense matter. In our framework, nucleons arise as topological solitons stabilized by vector mesons, which are dynamically generated through the path integral bosonization of an underlying Nambu–Jona-Lasinio (NJL) model. The restoration of chiral symmetry is implemented dynamically via a self-consistent, density dependent scalar field, which modifies the (isovector) and (isoscalar) channels of the soliton. We analyze the resulting changes in soliton properties for different NJL parameter sets and demonstrate that the progressive restoration of chiral symmetry leads to a stiffening of the soliton-based EoS, making it compatible with existing neutron star EoSs. An EoS constructed from the solutions of the energy-density and pressure profiles at the center of the nucleon is also explored.

We employ the QCD sum rule method to study the semileptonic weak decay of the single bottom baryon (Omega _{b}^{*}) with spin (frac{3}{2}) into the single charmed baryon (Omega _{c}^{*}) with spin (frac{3}{2}), corresponding to a (frac{3}{2}rightarrow frac{3}{2}) weak transition. A three-point correlation function is calculated in both the physical and theoretical sides to derive the sum rules for the form factors of the transition. The analysis incorporates both the perturbative and non-perturbative contributions up to mass dimension six. After determining the working regions of the auxiliary parameters and performing numerical calculations of the sum rules of the form factors, we extract the (q^2)-dependent fit functions for the form factors. The obtained fit functions are then applied to compute the decay widths of the (Omega _{b}^{*}rightarrow Omega _{c}^{*} ell bar{nu }_{ell }) transition in all lepton channels. Our results may serve as useful theoretical benchmarks for future experimental investigations of the semileptonic (Omega _{b}^{*}rightarrow Omega _{c}^{*} ell bar{nu }_{ell }) weak decays and the weak dynamics of excited heavy baryons.

Elastic scattering of fast neutrons at an incident energy of 30.8 MeV on a natural cerium target was measured during an experiment conducted at the Neutrons For Science facility at GANIL-SPIRAL2. This is the first measurement on cerium using incident neutron energy above 20 MeV. The differential cross-section up to 40(^circ ) in the centre-of-mass frame was extracted using the MONSTER liquid scintillator array for the scattered neutron detection. The experimental results are compared to global optical-model calculations, providing an overall very good agreement and a useful benchmark at intermediate energy.

We present the design, developments, and test results of the new scintillating fiber based tracking detectors which are part of the R(^3)B experimental setup at GSI and FAIR, Darmstadt, Germany. Those tracking detectors are capable to track heavy ions of all charges at relativistic energies. Together with an elaborate particle-tracking system, the full identification of relativistic ions from hydrogen up to uranium in mass and nuclear charge is possible.