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Toth, A., Elekes, Z., Fülöp, Z., Gyürky, G., Halász, Z., Juhász, M. M., et al. (2025). Gas-cell development for nuclear astrophysics motivated studies on noble gas targets and the 3He(α,γ)7Be reaction. Eur. Phys. J. A, 61(12), 274–14pp.
Abstract: In many astrophysical scenarios, alpha induced reactions on noble gas nuclei play a crucial role. Studying these reactions in the laboratory requires the noble gas atoms to be confined in a sufficient amount to allow the reactions. At Atomki thin-windowed gas-cell targets were developed and improved for studying alpha induced reactions on noble gases. Several stages of the gas-cell design used for activation experiments and lately a version to be used for particle scattering experiments will be presented. A new experimental study of the 3He(alpha,gamma)7Be reaction with one of the activation gas-cell targets was performed. This reaction plays an important role both in the solar pp-chains and in big bang nucleosynthesis. The reaction cross section was measured in the past in several works, however, there are still energy regions lacking experimental data, rendering the extrapolations towards the astrophysically relevant energies uncertain. New experimental total cross section of the 3He(alpha,gamma)7Be reaction was thus determined here in the energy range of Ec.m.=2600-3000 keV in about 50 keV energy steps. These results confirm the overall trend, and also the absolute scale set by the only one previous measurement in this energy range. In addition, two pilot experiments with the scattering cell were performed aiming to study the 4He(alpha,alpha)4He and 124Xe(alpha,alpha)124Xe reactions at E alpha=18 MeV. These studies benchmark the performance of the cell and detection system both for light and heavy noble gas targets.
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Encarnacion, P., Albaladejo, M., Feijoo, A., & Nieves, J. (2025). Spectroscopic and femtoscopic insights into vector-baryon interactions in the strangeness-1 sector. Eur. Phys. J. C, 85(11), 1347–19pp.
Abstract: We revisit the strangeness -1 sector of the interaction between vector mesons of the rho-nonet and 1/2+ ground state baryons (VB), within the unitary coupled-channel hidden gauge formalism. We adopt a renormalization scheme that induces a reasonable short-distance behavior of the two-hadron wave functions, which is the major limitation of femtoscopy techniques at this time. We perform an exhaustive spectroscopy study, implementing different improvements and considerations, and find compatibilities between the poles extracted from the present approach, and some of the states listed in the Review of Particle Physics. Finally, we predict several correlation functions (CFs) associated with various meson-baryon pairs in this sector, paying special attention to the distinctive and clear signatures produced by the dynamically generated states. To obtain realistic estimates for the CFs, we have calculated the production weights using the Thermal-FIST package. Such studies will shed light into the odd-parity Lambda* and Sigma* hadron spectra, up to 2 GeV, and will open the strategy to improve effective field theories by using low-energy constants fitted to femtoscopy data.
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Ferreira, M. N., Papavassiliou, J., Pawlowski, J. M., & Wink, N. (2025). Physics of the gluon mass gap. Eur. Phys. J. C, 85(11), 1339–22pp.
Abstract: It has long been known that the gluon propagator in Landau-gauge QCD exhibits a mass gap; and its emergence has been ascribed to the action of the Schwinger mechanism in the gauge sector of QCD. In the present work, we relate this property to the physical mass gap of QCD by considering two observables associated with confinement and chiral symmetry breaking, namely the confinement-deconfinement transition temperature and the pion decay constant, respectively. It turns out that the first observable is linearly proportional to the gluon mass gap, a fact that allows us to assign a direct physical meaning to this scale. Moreover, we identify three distinct momentum regimes in the gluon propagator, ultraviolet, intermediate, and deep infrared, and assess their impact on the aforementioned observables. Both observables are sensitive to the first two regions of momenta, where functional approaches essentially coincide, but are insensitive to the third, deep infrared, regime. The combined information is used for a simple fit for the gluon propagator, all of whose parameters admit a clear physical interpretation. Finally, we discuss how this fit can help us access the intertwined dynamics of confinement and chiral symmetry breaking in QCD-type theories.
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Aguilera, P. et al, Rubio, B., Orrigo, S. E. A., Gelletly, W., Agramunt, J., Algora, A., et al. (2025). β decay of the Tz =-2 nucleus 64Se and its descendants: The T=2 isobaric multiplet. Phys. Rev. C, 112(5), 054319–20pp.
Abstract: In this paper we present our results on the decay of 64Se. It is the heaviest Tz = -2 nucleus that both 9 decays and has a stable mirror partner (Tz = +2), thus allowing comparison with charge exchange reaction studies. The 9 decays of 64Se and its descendants were studied at the RIKEN Nishina Center (Japan) following their production in the fragmentation of 78Kr on a beryllium target. 9-Delayed gamma-ray and particle radiation was identified for each of the nuclei in the decay chain allowing us to obtain decay schemes for 64Se, 64As, and 63Ge. Thus new excited states could be found for the descendant nuclei, including the interesting case of the N = Z nucleus 64Ge. Furthermore, we observed for the first time the 9-delayed proton emission of 64Se and 64As. Based on these results we obtained proton branching ratios of 48.0(9)% in 64Se decay and 4.4(1)% in 64As decay. We obtained a half-life value of 22.5(6) ms for 64Se decay and half-lives slightly more precise than those in the literature for each nucleus involved in the decay chain. Using our results on the excited levels of 64As and the mass excess in the literature for 63Ge we obtained-39588(50) keV for the mass excess of 64As. Then based on the isobaric mass multiplet equation we obtained the mass excess of-27429(88) keV for 64Se by extrapolation. The mirror process of 64Se 3 decay, the charge exchange reaction 64Zn(3He, t)64Ga, has already been measured allowing us to study the mirror symmetry through the comparison of the weak force (3a decay) and strong force (charge exchange reaction). An interpretation of the decay schemes based on the idea of the antisnalogue tate is proposed.
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ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Bouchhar, N., Cabrera Urban, S., Cantero, J., et al. (2025). Measurement of jet track functions in pp collisions at √s=13 TeV with the ATLAS detector. Phys. Lett. B, 868, 139680–24pp.
Abstract: Measurements of jet substructure are key to probing the energy frontier at colliders, and many of them use track-based observables which take advantage of the angular precision of tracking detectors. Theoretical calculations of track-based observables require 'track functions', which characterize the transverse momentum fraction r(q) carried by charged hadrons from a fragmenting quark or gluon. This letter presents a direct measurement of r(q) distributions in dijet events from the 140 fb(-1) of proton-proton collisions at root s = 13 TeV recorded with the ATLAS detector. The data are corrected for detector effects using machine-learning methods. The scale evolution of the moments of the r(q) distribution is sensitive to non-linear renormalization group evolution equations of QCD, and is compared with analytic predictions. When incorporated into future theoretical calculations, these results will enable a precision program of theory-data comparison for track-based jet substructure observables.
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