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Nieves, J., Pavao, R., & Sakai, S. (2019). Lambda(b) decays into Lambda cl(nu)over-barl and Lambda c*pi(-) [ Lambda(c)* = Lambda(c)( 2595) and Lambda(c)(2625)] and heavy quark spin symmetry. Eur. Phys. J. C, 79(5), 417–20pp.
Abstract: We study the implications for bc=c(2595) and c(2625)] decays that can be deduced from heavy quark spin symmetry (HQSS). Identifying the odd parity c(2595) and c(2625) resonances as HQSS partners, with total angular momentum-parity jqP=1- for the light degrees of freedom, we find that the ratios (bc(2595)-)/(bc(2625)-) and (bc(2595)) agree, within errors, with the experimental values given in the Review of Particle Physics. We discuss how future, and more precise, measurements of the above branching fractions could be used to shed light into the inner HQSS structure of the narrow c(2595) odd-parity resonance. Namely, we show that such studies would constrain the existence of a sizable jqP</mml:msubsup>=0- component in its wave-function, and/or of a two-pole pattern, in analogy to the case of the similar (1405) resonance in the strange sector, as suggested by most of the approaches that describe the c(2595) as a hadron molecule. We also investigate the lepton flavor universality ratios R[c]=B( may be affected by a new source of potentially large systematic errors if there are two) poles.
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Liang, W. H., Chen, H. X., Oset, E., & Wang, E. (2019). Triangle singularity in the J/psi -> K+K- f(0)(980)(a(0)(980)) decays. Eur. Phys. J. C, 79(5), 411–11pp.
Abstract: We study the J/psi -> K+K- f(0)(980)(a(0)(980)) reaction and find that the mechanism to produce this decay develops a triangle singularity around M-inv(K- f(0)/K- a(0)) approximate to 1515 MeV. The differential width d Gamma/dM(inv)(K- f(0)/K- a(0)) shows a rapid growth around the invariant mass being 1515 MeV as a consequence of the triangle singularity of this mechanism, which is directly tied to the nature of the f(0)(980) and a(0)(980) as dynamically generated resonances from the interaction of pseudoscalar mesons. The branching ratios obtained for the J/psi -> K+K- f(0)(980)(a(0)(980)) decays are of the order of 10(-5), accessible in present facilities, and we argue that their observation should provide relevant information concerning the nature of the low-lying scalar mesons.
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Barenboim, G., & Park, W. I. (2019). Spontaneous baryogenesis in spiral inflation. Eur. Phys. J. C, 79(6), 456–11pp.
Abstract: We examined the possibility of spontaneous baryogenesis driven by the inflaton in the scenario of spiral inflation, and found the parametric dependence of the late-time baryon number asymmetry. As a result, it is shown that, depending on the effective coupling of baryon/lepton number violating operators, it is possible to obtain the right amount of asymmetry even in the presence of a matter-domination era as long as such era is relatively short. In a part of the parameter space, the required expansion rate during inflation is close to the current upper-bound, and hence can be probed in the near future experiments.
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Baglio, J., Campanario, F., Glaus, S., Muhlleitner, M., Spira, M., & Streicher, J. (2019). Gluon fusion into Higgs pairs at NLO QCD and the top mass scheme. Eur. Phys. J. C, 79(6), 459–9pp.
Abstract: We present the calculation of the full next-to-leading order (NLO) QCD corrections to Higgs boson pair production via gluon fusion at the LHC, including the exact top-mass dependence in the two-loop virtual and one-loop real corrections. This is the first independent cross-check of the NLO QCD corrections presented in the literature before. Our calculation relies on numerical integrations of Feynman integrals, stabilised with integration-by-parts and a Richardson extrapolation to the narrow width approximation. We present results for the total cross section as well as for the invariant Higgs-pair-mass distribution at the LHC, including for the first time a study of the uncertainty due to the scheme and scale choice for the top mass in the loops.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Aparisi Pozo, J. A., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., et al. (2019). Search for long-lived neutral particles in pp collisions at root s=13 TeV that decay into displaced hadronic jets in the ATLAS calorimeter. Eur. Phys. J. C, 79(6), 481–31pp.
Abstract: This paper describes a search for pairs of neutral, long-lived particles decaying in the ATLAS calorimeter. Long-lived particles occur in many extensions to the Standard Model and may elude searches for new promptly decaying particles. The analysis considers neutral, long-lived scalars with masses between 5 and 400 GeV, produced from decays of heavy bosons with masses between 125 and 1000 GeV, where the long-lived scalars decay into Standard Model fermions. The analysis uses either 10.8 fb-1 of data (depending on the trigger) recorded in 2016 at the LHC with the ATLAS detector in proton-proton collisions at a centre-of-mass energy of 13 TeV. No significant excess is observed, and limits are reported on the production cross section times branching ratio as a function of the proper decay length of the long-lived particles.
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