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Journal of Physics G: Nuclear and Particle Physics - latest papers

Latest articles for Journal of Physics G: Nuclear and Particle Physics

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  • Comparison of deep neural networks and variational quantum circuits for quark-gluon jet classification
    Jets, the hadronization form of quarks and gluons produced in high energy collisions, is one of the significant probes to investigate the quark-gluon plasma, a state of matter that existed shortly after the Big Bang. The origin of these collimated sprays of particles is identified by a jet discriminator providing information about the dynamics of quarks and gluons for a deeper understanding of quantum chromodynamics. Machine learning (ML) techniques, particularly deep neural networks (DNNs), have been widely used in high energy physics analysis to enhance the interpretation of datasets at the large hadron collider (LHC). Recently, the quantum ML (QML) approach with variational quantum circuits (VQC) offers potential advantages in processing high dimensional data with fewer resources. Therefore, in this study DNNs and VQC were implemented for the identification of jet origin if it is from light quarks [up (u), down (d), and strange (s)] or gluons (g) from simulated proton–proton collisions at the compact muon solenoid (CMS) detector with a center-of-mass energy of 13 TeV generated with Pythia 8. The results were compared with the jet likelihood discriminator tool used at the CMS to evaluate the performance of ML and QML for jet origin determination in large datasets produced at the LHC. While DNNs achieve superior performance across precision, recall, and F1 metrics, VQC shows potential despite optimization and data size limitations. This study highlights the strengths and challenges of classical data analysis with classical and quantum computing approaches, offering valuable insights into their applicability to particle physics.

  • Understanding the medium-like effects in the jet-like yield in pp and p–Pb collisions using event generators
    To understand the dynamics of jet–medium interaction in small systems such as proton–proton (pp) and proton–lead (p–Pb) collisions at = 5.02 TeV, particle production is studied in three distinct topological regions defined with respect to the charged particle with the highest transverse momentum in the event ( ). The jet-like yield is defined by the particle density in the toward region (∣Δφ∣ < π/3) after subtracting that in the transverse region (π/3 < ∣Δφ∣ < 2π/3). The activity on the transverse side is used as a proxy for medium-like effects. Three different Monte Carlo event generators—Pythia8, a multiphase transport (AMPT) model, and EPOS4—are employed to investigate particle yields as a function of in the interval 0.5–20 GeV/c. Calculations are performed for the pT threshold of 0.5 GeV/c at mid-rapidity (∣η∣ < 0.8). The jet-like yield in the toward region for pp collisions show interesting dynamics; they are significantly affected by the medium-like effects in the low to intermediate (<8 GeV/c) which is studied through color reconnection and hydrodynamics in Pythia8 and EPOS4, respectively. However, the results from AMPT show that the jet-like yield is medium-like modified throughout the entire range. The jet-like yield in p–Pb collisions using AMPT is also studied. Notably, a dip structure that is observed in the jet-like signal ratio of pp to p–Pb at low in ALICE data, is reproduced by AMPT model with SM on, pointing to possible medium-like behavior in small systems. The results of this article also underscore the importance of high- ( 8 GeV/c) for minimizing underlying event biases in jet-related studies.

  • Ab initio lattice study of neutron–alpha scattering with chiral forces at N3LO
    We present the first ab initio lattice calculation of neutron–alpha (n–α) scattering using nuclear lattice effective field theory with chiral interactions at next-to-next-to-next-to-leading order (N3LO). Building on the high-fidelity chiral Hamiltonian introduced in Elhatisari et al (2024 Nature 630 59), we compute scattering phase shifts in the S- and P-wave channels using the Lüscher finite-volume method. Our results demonstrate excellent agreement with empirical R-matrix phase shifts in the 2S1/2 and 2P3/2 channels, while revealing persistent discrepancies in the 2P1/2 channel for neutron energies above 5 MeV. To systematically investigate these discrepancies, we construct and analyze a simplified neutron–alpha toy model, demonstrating that these discrepancies are not due to the use of the Lüscher finite-volume method. Additionally, we revisit our three-nucleon (3N) force fitting procedure, explicitly incorporating neutron–alpha scattering data through comprehensive Markov Chain Monte Carlo sampling. This analysis confirms the stability of nuclear binding-energy predictions and highlights the need for further refinements in the lattice N3LO three-nucleon forces to fully describe neutron–alpha scattering in the challenging 2P1/2 channel.

  • Model comparisons of transverse energy and charged-particle multiplicity in A + A collisions at midrapidity from ...
    We present a comprehensive comparison of PHENIX measurements of transverse energy production (dET/dη) and charged-particle multiplicity (dN/dη) at midrapidity to simulations from PYTHIA-8, AMPT, HIJING, and SMASH. These comparisons span both small systems (d + Au, 3He + Au) and large systems (Cu + Cu, Cu + Au, Au + Au, and U + U) at ∼ 200 GeV and Au + Au over a range of beam energies –200 GeV. Using the Rivet framework, we assess the performance of these models. While general trends are captured, significant deviations persist, particularly in low-energy and peripheral collisions, underscoring the need for improved modeling of baryon stopping and energy deposition mechanisms.

  • Thermal conductivity of rotating hot and dense hadronic matter under the influence of Coriolis force
    In this study, we explore the impact of the Coriolis force on the thermal conductivity of hadronic matter produced in non-central relativistic heavy ion collisions. The Boltzmann transport equation is solved within the kinetic theory framework using the relaxation-time approximation, incorporating the hadron resonance Gas model along with the hard-sphere scattering approach. This analysis highlights the anisotropic characteristics of heat transport in rotating hadronic matter, revealing a noticeable reduction in magnitude under the influence of rotation. We further analyse its individual components as a function of temperature and baryon chemical potential.