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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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  • Reconstructing transition GPDs for Δ(1232) from helicity amplitude A 1/2(Q 2) via dipole fits and impact parameter analysis
    This work presents a modular reconstruction of the transition generalized parton distribution (GPD) HT(x, t) for the Δ(1232) resonance, based on digitized helicity amplitude data and dipole fits to A1/2(Q2). From the fitted amplitude, we extract a Sachs-like form factor F(t) and define a separable GPD model HT(x, t) = h(x) F(t), with h(x) modeled as a normalized Beta-like profile. This factorized ansatz satisfies the GPD sum rule and enables a direct two-dimensional Fourier transform to construct transverse spatial distributions q(x, b). We analyze how longitudinal shaping modulates transverse localization, and quantify spatial features using statistical diagnostics including mean radius, skewness, and kurtosis. The framework is reproducible, data-driven, and applicable to other transition channels, providing a physically interpretable map from amplitude behavior to spatial structure.

  • Nonresonant capture cross section measurement of the 29Si(p,γ)30P reaction
    The isotopic ratios measured in meteoritic presolar grains are a crucial tool for tracing the nucleosynthetic origin of isotopes. In the case of silicon isotopes, two important indicators to establish the origin of presolar grains are the ratios 29Si/28Si and 30Si/28Si. To constrain theoretical predictions, the rates of key nuclear reactions influencing the abundances of 29Si and 30Si must be well known. One such reaction is 29Si(p,γ)30P which plays a role in classical nova explosions. The aim of the present work is to determine the nonresonant cross section of the 29Si(p,γ)30P reaction, which has not been previously measured. The activation method was employed to measure the total cross section at four proton energies between Ep = 1000 and 1430 keV. The measured cross sections were found to be significantly (a factor of 4.3 ± 0.6) higher than those predicted by theoretical direct capture calculations, thereby impacting the reaction rates at low astrophysical temperatures, below about 30 MK. This higher nonresonant cross section—now based on experimental data—can be used in forthcoming nucleosynthesis calculations of classical novae. As a secondary result, the 16O(p,γ)17F cross section was also obtained and found to be in good agreement with existing literature data.

  • Branching fraction, CP asymmetry, and polarization in B → ρρ decays with the modified perturbative QCD approach
    In this work, we examine the observables associated with the B → ρρ decays, including branching fractions, CP asymmetry parameters, and longitudinal polarization fractions in the perturbative QCD (PQCD) approach with a few improvements. The essential distinction between this study and previous works lies in the introduction of an infrared cutoff at the critical scale μc, which is approximately at the scale of 1 GeV. The contributions above the critical scale are calculated using the PQCD approach, consistent with earlier studies, while the contributions below the scale μc are regarded as nonperturbative and represented by some soft form factors. In addition, the distribution amplitude of the B meson, derived from the relativistic potential model, and the contributions from the color-octet quark–antiquark components are also taken into account. With these modifications, we find that the theoretical results agree well with the experimental measurements for most observables, the introduction of the infrared cutoff enhances the reliability of the perturbation calculations, and the color-octet contributions play a key role in explaining the experimental data.

  • Physics with high-luminosity proton-nucleus collisions at the LHC ∗
    The physics case for the operation of high-luminosity proton-nucleus (pA) collisions at the CERN LHC is reviewed. The collection of (1–10 pb−1) of proton-lead (pPb) collisions at the LHC will provide unique physics opportunities in a broad range of topics including proton and nuclear parton distribution functions (PDFs and nPDFs), generalised parton distributions (GPDs), transverse momentum dependent PDFs (TMDs), low-x quantum chromodynamics and parton saturation, hadron spectroscopy, baseline studies for quark-gluon plasma and parton collectivity, double and triple parton scatterings, photon–photon collisions, and physics beyond the Standard Model; which are not otherwise as clearly accessible by exploiting data from any other colliding system at the LHC. This report summarises the accelerator aspects of high-luminosity pA operation at the LHC, as well as each of the physics topics outlined above, including the relevant experimental measurements that motivate much larger pA datasets than collected to date.

  • Investigating the most active pp collisions (top 0.1%) using the tools developed by experiments at the LHC
    The LHC data have unveiled unexpected features in proton–proton (pp) collisions, namely, collective-like behavior and strangeness enhancement. Originally, these new effects were discovered only in high-multiplicity pp collisions. However, recently the ALICE Collaboration has shown that even low-multiplicity pp collisions yield a non-zero elliptic flow (v2). Moreover, analyses as functions of the event structure, such as transverse spherocity, suggest that multiplicity might not be the main driver of the new effects. Therefore, new ways of analyzing the data have to be explored in order to understand the origin of the new phenomena. In this paper, pp collisions simulated with PYTHIA 8 are analyzed using different event estimators (mid-pseudorapidity multiplicity, spherocity, sphericity, RT, forward multiplicity and flattenicity). The features of the selected events for the top 0.1% using the different estimators are discussed. The transverse momentum spectrum of primary particles and the recoil jet distributions are analyzed. The results suggest that flattenicity is the estimator with the least bias on the neutral-to-charged particle ratio, and on the bias towards harder-than-average pp collisions.