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Reig, M., & Srivastava, R. (2019). Spontaneous proton decay and the origin of Peccei-Quinn symmetry. Phys. Lett. B, 790, 134–139.
Abstract: We propose a new interpretation of Peccei-Quinn symmetry within the Standard Model, identifying it with the axial B+L symmetry i.e. U (1)(PQ) equivalent to U (1)(gamma 5)(B+L). This new interpretation retains all the attractive features of Peccei-Quinn solution to strong CP problem but in addition also leads to several other new and interesting consequences. Owing to the identification U (1)(PQ) equivalent to U (1)(gamma 5)(B+L) the axion also behaves like Majoron inducing small seesaw masses for neutrinos after spontaneous symmetry breaking. Another novel feature of this identification is the phenomenon of spontaneous (and also chiral) proton decay with its decay rate associated with the axion decay constant. Low energy processes which can be used to test this interpretation are pointed out.
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Binosi, D., Chang, L., Ding, M. H., Gao, F., Papavassiliou, J., & Roberts, C. D. (2019). Distribution amplitudes of heavy-light mesons. Phys. Lett. B, 790, 257–262.
Abstract: A symmetry-preserving approach to the continuum bound-state problem in quantum field theory is used to calculate the masses, leptonic decay constants and light-front distribution amplitudes of empirically accessible heavy-light mesons. The inverse moment of the B-meson distribution is particularly important in treatments of exclusive B-decays using effective field theory and the factorisation formalism; and its value is therefore computed: lambda(B) = (zeta = 2GeV) = 0.54(3) GeV. As an example and in anticipation of precision measurements at new-generation B-factories, the branching fraction for the rare B -> gamma (E-gamma)l nu(l) radiative decay is also calculated, retaining 1/m(B)(2), and 1/E-gamma(2) corrections to the differential decay width, with the result Gamma(B -> gamma l nu l) /Gamma(B) = 0.47 (15) on E-gamma > 1.5 GeV.
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Reig, M., Restrepo, D., Valle, J. W. F., & Zapata, O. (2019). Bound-state dark matter with Majorana neutrinos. Phys. Lett. B, 790, 303–307.
Abstract: We propose a simple scenario in which dark matter (DM) emerges as a stable neutral hadronic thermal relic, its stability following from an exact U(1)(D) symmetry. Neutrinos pick up radiatively induced Majorana masses from the exchange of colored DM constituents. There is a common origin for both dark matter and neutrino mass, with a lower bound for neutrinoless double beta decay. Direct DM searches at nuclear recoil experiments will test the proposal, which may also lead to other phenomenological signals at future hadron collider and lepton flavor violation experiments.
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n_TOF Collaboration(Lederer-Woods, C. et al), Domingo-Pardo, C., Tain, J. L., & Tarifeño-Saldivia, A. (2019). Measurement of Ge-73(n, gamma) cross sections and implications for stellar nucleosynthesis. Phys. Lett. B, 790, 458–465.
Abstract: Ge-73(n, gamma) cross sections were measured at the neutron time-of-flight facility n_TOF at CERN up to neutron energies of 300 keV, providing for the first time experimental data above 8 keV. Results indicate that the stellar cross section at kT = 30 keV is 1.5 to 1.7 times higher than most theoretical predictions. The new cross sections result in a substantial decrease of Ge-73 produced in stars, which would explain the low isotopic abundance of Ge-73 in the solar system.
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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). Study of the hard double-parton scattering contribution to inclusive four-lepton production in pp collisions at root s=8 TeV with the ATLAS detector. Phys. Lett. B, 790, 595–614.
Abstract: The inclusive production of four isolated charged leptons in pp collisions is analysed for the presence of hard double-parton scattering, using 20.2 fb(-1) of data recorded in the ATLAS detector at the LHC at centre-of-mass energy root s = 8 TeV. In the four-lepton invariant-mass range of 80 < m(4l) < 1000 GeV, an artificial neural network is used to enhance the separation between single- and double-parton scattering based on the kinematics of the four leptons in the final state. An upper limit on the fraction of events originating from double-parton scattering is determined at 95% confidence level to be f(DPS) = 0.042, which results in an estimated lower limit on the effective cross section at 95% confidence level of 1.0 mb.
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Richard, J. M., Valcarce, A., & Vijande, J. (2019). Pentaquarks with anticharm or beauty revisited. Phys. Lett. B, 790, 248–250.
Abstract: We use a constituent model to analyze the stability of pentaquark (Q) over bar qqqq configurations with a heavy antiquark (c) over bar or (b) over bar, and four light quarks uuds, ddsu or ssud. The interplay between chromoelectric and chromomagnetic effects is not favorable, and, as a consequence, no bound state is found below the lowest dissociation threshold.
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NA62 Collaboration(Cortina Gil, E. et al), & Husek, T. (2019). First search for K+ -> pi(+) nu(nu)over-bar using the decay-in-flight technique. Phys. Lett. B, 791, 156–166.
Abstract: The NA62 experiment at the CERN SPS reports the first search for K+ -> pi(+) nu(nu) over bar using the decay-in-flight technique, based on a sample of 1.21 x10(11) K+ decays collected in 2016. The single event sensitivity is 3.15 x10(-10), corresponding to 0.267 Standard Model events. One signal candidate is observed while the expected background is 0.152 events. This leads to an upper limit of 14 x10(-10) on the K+ -> pi(+) nu(nu) over bar branching ratio at 95% CL.
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Barenboim, G., Denton, P. B., Parke, S. J., & Ternes, C. A. (2019). Neutrino oscillation probabilities through the looking glass. Phys. Lett. B, 791, 351–360.
Abstract: In this paper we review different expansions for neutrino oscillation probabilities in matter in the context of long-baseline neutrino experiments. We examine the accuracy and computational efficiency of different exact and approximate expressions. We find that many of the expressions used in the literature are not precise enough for the next generation of long-baseline experiments, but several of them are while maintaining comparable simplicity. The results of this paper can be used as guidance to both phenomenologists and experimentalists when implementing the various oscillation expressions into their analysis tools.
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Bruschini, R., & Gonzalez, R. (2019). A plausible explanation of Upsilon(10860). Phys. Lett. B, 791, 409–413.
Abstract: We show that a good description of the Upsilon(10860) properties, in particular the mass, the e(+) e(-) leptonic widths and the pi(+) pi(-) Upsilon(ns) (n = 1, 2, 3) production rates, can be obtained under the assumption that Upsilon(10860) is a mixing of the conventional Upsilon(5s) quark model state with the lowest P-wave hybrid state.
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Ferreiro, A., & Navarro-Salas, J. (2019). Running couplings from adiabatic regularization. Phys. Lett. B, 792, 81–85.
Abstract: We extend the adiabatic regularization method by introducing an arbitrary mass scale μin the construction of the subtraction terms. This allows us to obtain, in a very robust way, the running of the coupling constants by demanding mu-invariance of the effective semiclassical (Maxwell-Einstein) equations. In particular, we get the running of the electric charge of perturbative quantum electrodynamics. Furthermore, the method brings about a renormalization of the cosmological constant and the Newtonian gravitational constant. The running obtained for these dimensionful coupling constants has new relevant (non-logarithmic) contributions, not predicted by dimensional regularization.
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