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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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Andreyev, A. N. et al, Algora, A., & Nacher, E. (2025). Electromagnetic moments of 215,217Bi: Probing shell evolution beyond N=126. Phys. Lett. B, 871, 140013–9pp.
Abstract: The nuclear properties of bismuth isotopes (Z = 83), with just one valence proton above the closed spherical shell at Z = 82, are expected to be governed by a single unpaired proton. However, already in semimagic 209Bi (Z = 83, N = 126), the magnetic moment (mu) strongly deviates from the single-particle Schmidt value. A near linear decrease in μwith the increase of N after the N = 126 magic number was observed up to N = 130. In order to test whether this trend is kept at N> 130 and to reveal the underlying mechanisms, an investigation of Bi-215,Bi-217 (N = 132, 134) has been undertaken. The magnetic dipole and electric quadrupole moments of the I-x= 9/2-nuclear ground states in these isotopes have been measured for the first time using the in-source resonance-ionization spectroscopy technique at ISOLDE (CERN). It has been shown that the linearly decreasing trend of mu(Bi-209,211,213(g)) is broken in Bi-215,Bi-217 with a nearly constant value of μobserved. Experimental data have been compared to calculations in the framework of the configuration-interaction shell model with the monopole-based universal VMU+LS interaction. The peculiarities in the behavior of μ(Bi, 9/2-) with increasing neutron number are explained as being due to the shell evolution, change of the neutron orbitals occupancies and strong configuration mixing beyond N = 130. Also, the difference in the μtrends for bismuth (Z = 83) and astatine (Z = 85) isotopes with N> 126 are reproduced by the shell-model calculations. It is shown that monopole interaction plays noticeable role in the description of the peculiarities of the μbehaviour. Additionally, the extension of the application of the V-MU interaction to the μisotopic trends for heavy nuclei is important for further study of the capabilities of this promising version of the shell-model calculations.
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