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Xiao, C. W., Dias, J. M., Dai, L. R., Liang, W. H., & Oset, E. (2024). Triangle singularity in the J/ψ → ϕ π+ a−0(π−η) ,ϕ π− a+0(π+η) decays. Phys. Rev. D, 109(7), 074033–11pp.
Abstract: We study the J= psi -> phi pi + a 0 ( 980 ) – ( a – 0 -> pi – eta ) decay, evaluating the double mass distribution in terms of the pi – eta and pi + a – 0 invariant masses. We show that the pi – eta mass distribution exhibits the typical cusp structure of the a 0 ( 980 ) seen in recent high statistics experiments, and the pi + a – 0 spectrum shows clearly a peak around M inv ( pi + a – 0 ) = 1420 MeV, corresponding to a triangle singularity. When integrating over the two invariant masses we find a branching ratio for this decay of the order of 10 – 5 , which is easily accessible in present laboratories. We also call attention to the fact that the signal obtained is compatible with a bump experimentally observed in the eta pi + pi – mass distribution in the J= psi -> phi eta pi + pi – decay and encourage further analysis to extract from there the phi pi + a – 0 and phi pi – a + 0 decay modes.
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Rinaldi, M., & Vento, V. (2024). Hybrid spectroscopy within the graviton soft-wall model. Phys. Rev. D, 109(11), 114030–13pp.
Abstract: In this analysis, the so-called holographic graviton soft-wall (GSW) model, first developed to investigate the glueball spectrum, has been adopted to predict the masses of hybrids with different quantum numbers. Results have been compared with other models and lattice calculations. We have extended the GSW model by introducing two modifications based on anomalous dimensions in order to improve our agreement with other calculations and to remove the initial degeneracy not accounted for by lattice predictions. These modifications do not involve new parameters. The next step has been to identify which of our calculated states agree with the PDG data, leading to experimental hybrids. The procedure has been extended to include hybrids made of heavy quarks by incorporating the quark masses into the model.
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Yaneva, A. et al, & Algora, A. (2024). The shape of the Tz =+1 nucleus 94Pd and the role of proton-neutron interactions on the structure of its excited states. Phys. Lett. B, 855, 138805–7pp.
Abstract: Reduced transition probabilities have been extracted between excited, yrast states in the N = Z + 2 nucleus Pd-94. The transitions of interest were observed following decays of the I-pi = 14(+), E-x = 2129-keV isomeric state, which was populated following the projectile fragmentation of a Xe-124 primary beam at the GSI Helmholtzzentrum fur Schwerionenforschung accelerator facility as part of FAIR Phase-0. Experimental information regarding the reduced E2 transition strengths for the decays of the yrast 8(+) and 6(+) states was determined following isomer-delayed E-gamma 1 – E-gamma 2 – Delta T-2,T-1 coincidence method, using the LaBr3(Ce)-based FATIMA fast-timing coincidence gamma-ray array, which allowed direct determination of lifetimes of states in Pd-94 using the Generalized Centroid Difference (GCD) method. The experimental value for the half-life of the yrast 8(+) state of 755(106) ps results in a reduced transition probability of B(E2:8(+)-> 6(+)) = 205(-25)(+34) e(2) fm(4), which enables a precise verification of shell-model calculations for this unique system, lying directly between the N = Z line and the N = 50 neutron shell closure. The determined B(E2) value provides an insight into the purity of (g(9/2))(n) configurations in competition with admixtures from excitations between the (lower) N = 3pf and (higher) N = 4gds orbitals for the first time. The results indicate weak collectivity expected for near-zero quadrupole deformation and an increasing importance of the T = 0 proton-neutron interaction at N = 48.
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Cepedello, R., Esser, F., Hirsch, M., & Sanz, V. (2024). Fermionic UV models for neutral triple gauge boson vertices. J. High Energy Phys., 07(7), 275–28pp.
Abstract: Searches for anomalous neutral triple gauge boson couplings (NTGCs) provide important tests for the gauge structure of the standard model. In SMEFT (“standard model effective field theory”) NTGCs appear only at the level of dimension-8 operators. While the phenomenology of these operators has been discussed extensively in the literature, renormalizable UV models that can generate these operators are scarce. In this work, we study a variety of extensions of the SM with heavy fermions and calculate their matching to d = 8 NTGC operators. We point out that the complete matching of UV models requires four different CP-conserving d = 8 operators and that the single CPC d = 8 operator, most commonly used by the experimental collaborations, does not describe all possible NTGC form factors. Despite stringent experimental constraints on NTGCs, limits on the scale of UV models are relatively weak, because their contributions are doubly suppressed (being d = 8 and 1-loop). We suggest a series of benchmark UV scenarios suitable for interpreting searches for NTGCs in the upcoming LHC runs, obtain their current limits and provide estimates for the expected sensitivity of the high-luminosity LHC.
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Molina, R., Liang, W. H., Xiao, C. W., Sun, Z. F., & Oset, E. (2024). Two states for the Ξ(1820) resonance. Phys. Lett. B, 856, 138872–4pp.
Abstract: We recall that the chiral unitary approach for the interaction of pseudoscalar mesons with the baryons of the decuplet predicts two states for the Xi(1820) resonance, one with a narrow width and the other one with a large width. We contrast this fact with the recent BESIII measurement of the K- Lambda mass distribution in the psi(3686) decay to K- Lambda Xi(+), which demands a width much larger than the average of the PDG, and show how the consideration of the two Xi(1820) states provides a natural explanation to the experimental data.
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