abstract

This paper proposes a new simple memristive chaotic system (MCS) containing an exponential term, a constant term, and a memristor-based nonlinear term. The system has dissipative feature and only one equilibrium. Its parameter-relied complex dynamics are comprehensive studied and the chaos with large parameter regions, multiple bifurcations, and large-scale amplitude modulation are revealed. The proposed system can realize the transition from stability to periodicity via Hopf bifurcation and generate chaos via period-doubling bifurcation with the increase or decrease of multiple parameters. The boundaries of chaotic attractors and the oscillation amplitudes of variables expand over a large-scale range as the parameter values continuously increase, indicating the emergence of large-scale amplitude modulation in the system. Moreover, the fixed-time synchronization (FxTS) problem is studied and the corresponding FxTS conditions are obtained by applying slide mode controller with the designed power reaching law. Both the theoretical derivation and numerical simulation consistently demonstrate the effectiveness of the obtained results.

abstract

The intra-band reduced E2-transition probabilities depending on the effective triaxiality parameter \(\gamma _{\rm eff}\) are studied within the framework of the Davydov–Chaban model. The Davidson potential for \(\beta \) variable has been used. The intra-band reduced E2-transition probabilities ground-state, \(\beta \), and \(\gamma \) bands are presented and expressed in terms of three parameters: \(g\), \(\gamma _{\rm eff}\), and \(Q_0\). Permitted and forbidden intra-\(\gamma \)-band E2 transitions were discussed. The sensitivity of intra-band reduced E2-transition probabilities to the effective triaxiality parameter \(\gamma _{\rm eff}\) was analyzed.

abstract

Within classical electrodynamics, the problem of the existence or non-existence of massless charges is commonly associated with the problem of radiation reaction. Here, the relativistic system of two massless charged particles is considered within the Staruszkiewicz model, in which radiation reaction is neglected. The model is formulated in the Hamiltonian form with constraints. The system is invariant with respect to 15-parameter conformal group. The corresponding conserved canonical generators and the relativistic Laplace–Runge–Lenz vector imply the superintegrability of the system. The trajectory of the unbounded relative motion is hyperbolic, as in the non-relativistic Kepler problem. Surprisingly, particle world lines turn out to be lightlike straight rays, as if charges are switched off.

abstract

A study of a Graph Neural Network-based model for track reconstruction in the context of MUonE experiment is presented, using simulated data corresponding to the test-run MUonE detector setup. The fully three-dimensional model successfully addresses both the reconstruction and particle identification challenges essential for achieving the experiment’s primary physics goal. It provides significantly faster pattern recognition than classical reconstruction algorithms, while maintaining comparable efficiency and resolution.

abstract

In our previous studies, we calculated the cross section for the production of free \(\mu ^{+}\mu ^{-}\) 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 \(\mu ^{+}\mu ^{-}\) with bound-free \(e^{+}e^{-}\) pairs in relativistic Pb+Pb collisions at the LHC using Lorentz factors \(\gamma =1500\) and \(\gamma =3000\) 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 \(\mu ^{+}\mu ^{-}\) 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 \(\mu ^{+}\mu ^{-}\) pair production. Our results obtained here for the free \(\mu ^{+}\mu ^{-}\) 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 test of quantum electrodynamics (QED) in strong electromagnetic fields.

abstract

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.