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Das, D., & Santamaria, A. (2016). Updated scalar sector constraints in the Higgs triplet model. Phys. Rev. D, 94(1), 015015–10pp.
Abstract: We show that in the Higgs triplet model, after the Higgs discovery, the mixing angle in the CP-even sector can be strongly constrained from unitarity. We also discuss how large quantum effects in h -> gamma gamma may arise in a Standard-Model-like scenario and a certain part of the parameter space can be ruled out from the diphoton signal strength. Using T-parameter and diphoton signal strength measurements, we update the bounds on the nonstandard scalar masses.
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Hiller Blin, A. N., Fernandez-Ramirez, C., Jackura, A., Mathieu, V., Mokeev, V. I., Pilloni, A., et al. (2016). Studying the P-c(4450) resonance in J/psi photoproduction off protons. Phys. Rev. D, 94(3), 034002–8pp.
Abstract: A resonancelike structure, the P-c(4450), has recently been observed in the J/psi p spectrum by the LHCb Collaboration. We discuss the feasibility of detecting this structure in J/psi photoproduction in the CLAS12 experiment at JLab. We present a first estimate of the upper limit for the branching ratio of the P-c (4450) to J/psi p. Our estimates, which take into account the experimental resolution effects, predict that it will be possible to observe a sizable cross section close to the J/psi production threshold and shed light on the P-c(4450) resonance in the future photoproduction measurements.
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n_TOF Collaboration(Barbagallo, M. et al), Domingo-Pardo, C., Tain, J. L., & Tarifeño-Saldivia, A. (2016). Be-7(n,alpha)He-4 Reaction and the Cosmological Lithium Problem: Measurement of the Cross Section in a Wide Energy Range at n_TOF at CERN. Phys. Rev. Lett., 117(15), 152701–7pp.
Abstract: The energy-dependent cross section of the (7)Bed(n,alpha)He-4 reaction, of interest for the so-called cosmological lithium problem in big bang nucleosynthesis, has been measured for the first time from 10 meV to 10 keV neutron energy. The challenges posed by the short half-life of Be-7 and by the low reaction cross section have been overcome at nTOF thanks to an unprecedented combination of the extremely high luminosity and good resolution of the neutron beam in the new experimental area (EAR2) of the nTOF facility at CERN, the availability of a sufficient amount of chemically pure Be-7, and a specifically designed experimental setup. Coincidences between the two alpha particles have been recorded in two Si-Be-7-Si arrays placed directly in the neutron beam. The present results are consistent, at thermal neutron energy, with the only previous measurement performed in the 1960s at a nuclear reactor. The energy dependence reported here clearly indicates the inadequacy of the cross section estimates currently used in BBN calculations. Although new measurements at higher neutron energy may still be needed, the n_TOF results hint at a minor role of this reaction in BBN, leaving the long-standing cosmological lithium problem unsolved.
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n_TOF Collaboration(Gunsing, F. et al), Domingo-Pardo, C., Tain, J. L., & Tarifeño-Saldivia, A. (2016). Nuclear data activities at the n_TOF facility at CERN. Eur. Phys. J. Plus, 131(10), 371–13pp.
Abstract: Nuclear data in general, and neutron-induced reaction cross sections in particular, are important for a wide variety of research fields. They play a key role in the safety and criticality assessment of nuclear technology, not only for existing power reactors but also for radiation dosimetry, medical applications, the transmutation of nuclear waste, accelerator-driven systems, fuel cycle investigations and future reactor systems as in Generation IV. Applications of nuclear data are also related to research fields as the study of nuclear level densities and stellar nucleosynthesis. Simulations and calculations of nuclear technology applications largely rely on evaluated nuclear data libraries. The evaluations in these libraries are based both on experimental data and theoretical models. Experimental nuclear reaction data are compiled on a worldwide basis by the international network of Nuclear Reaction Data Centres (NRDC) in the EXFOR database. The EXFOR database forms an important link between nuclear data measurements and the evaluated data libraries. CERN's neutron time-of-flight facility nTOF has produced a considerable amount of experimental data since it has become fully operational with the start of the scientific measurement programme in 2001. While for a long period a single measurement station (EAR1) located at 185 m from the neutron production target was available, the construction of a second beam line at 20 m (EAR2) in 2014 has substantially increased the measurement capabilities of the facility. An outline of the experimental nuclear data activities at CERN's neutron time-of-flight facility nTOF will be presented.
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Tostado, S. L., & Lopez Castro, G. (2016). Radiative corrections of O(alpha) to B- -> V(0)l(-)(nu)over-bar(l) decays. Eur. Phys. J. C, 76(9), 495–15pp.
Abstract: The O(alpha) electromagnetic radiative corrections to the B- -> V(0)l(-)(nu) over bar (l) (V is a vector meson and l a charged lepton) decay rates are evaluated using the cutoff method to regularize virtual corrections and incorporating intermediate resonance states in the real-photon amplitude to extend the region of validity of the soft-photon approximation. The electromagnetic and weak form factors of hadrons are assumed to vary smoothly over the energies of virtual and real photons under consideration. The cutoff dependence of radiative corrections upon the scale Lambda that separates the long-and short-distance regimes is found to be mild and is considered as an uncertainty of the calculation. Owing to partial cancellations of electromagnetic corrections evaluated over the three-and four-body regions of phase space, the photoninclusive corrected rates are found to be dominated by the short-distance contribution. These corrections will be relevant for a precise determination of the b quark mixing angles by testing isospin symmetrywhen measurements of semileptonic rates of charged and neutral B mesons at the fewpercent level become available. For completeness, we also provide numerical values of radiative corrections in the three-body region of the Dalitz plot distributions of these decays.
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Cañas, B. C., Garces, E. A., Miranda, O. G., Tortola, M., & Valle, J. W. F. (2016). The weak mixing angle from low energy neutrino measurements: A global update. Phys. Lett. B, 761, 450–455.
Abstract: Taking into account recent theoretical and experimental inputs on reactor fluxes we reconsider the determination of the weak mixing angle from low energy experiments. We perform a global analysis to all available neutrino-electron scattering data from reactor antineutrino experiments, obtaining sin(2) theta(W) = 0.252 +/- 0.030. We discuss the impact of the new theoretical prediction for the neutrino spectrum, the new measurement of the reactor antineutrino spectrum by the Daya Bay collaboration, as well as the effect of radiative corrections. We also reanalyze the measurements of the nu(e) – e cross section at accelerator experiments including radiative corrections. By combining reactor and accelerator data we obtain an improved determination for the weak mixing angle, sin(2) theta(W) = 0.254 +/- 0.024.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2017). Search for B+ -> K+tau(+)tau(-) at the BABAR Experiment. Phys. Rev. Lett., 118(3), 031802–8pp.
Abstract: We search for the rare flavor-changing neutral current process B+ -> K+tau(+)tau(-) using data from the BABAR experiment. The data sample, collected at the center-of-mass energy of the Upsilon(4S) resonance, corresponds to a total integrated luminosity of 424 fb(-1) and to 471 x 10(6) B (B) over bar pairs. We reconstruct one B meson, produced in the Upsilon(4S) -> B+B- decay, in one of many hadronic decay modes and search for activity compatible with a B+ -> K+tau(+)tau(-) decay in the rest of the event. Each tau lepton is required to decay leptonically into an electron or muon and neutrinos. Comparing the expected number of background events with the data sample after applying the selection criteria, we do not find evidence for a signal. The resulting upper limit, at the 90% confidence level, is B(B+ -> K+tau(+)tau(-)) < 2.25 x 10(-3).
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., & Sanchez Mayordomo, C. (2017). Observation of J/psi phi Structures Consistent with Exotic States from Amplitude Analysis of B+ -> J/psi phi K+ Decays. Phys. Rev. Lett., 118(2), 022003–10pp.
Abstract: The first full amplitude analysis of B+ -> J/psi phi K+ with J/psi -> mu(+)mu(-), phi -> K+K- decays is performed with a data sample of 3 fb(-1) of pp collision data collected at root s = 7 and 8 TeV with the LHCb detector. The data cannot be described by a model that contains only excited kaon states decaying into phi K+ , and four J/psi phi structures are observed, each with significance over 5 standard deviations. The quantum numbers of these structures are determined with significance of at least 4 standard deviations. The lightest has mass consistent with, but width much larger than, previous measurements of the claimed X(4140) state.
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Barenboim, G., Kinney, W. H., & Park, W. I. (2017). Resurrection of large lepton number asymmetries from neutrino flavor oscillations. Phys. Rev. D, 95(4), 043506–6pp.
Abstract: We numerically solve the evolution equations of neutrino three-flavor density matrices, and show that, even if neutrino oscillations mix neutrino flavors, large lepton number asymmetries are still allowed in certain limits by big bang nucleosynthesis.
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Binosi, D., Chang, L., Papavassiliou, J., Qin, S. X., & Roberts, C. D. (2017). Natural constraints on the gluon-quark vertex. Phys. Rev. D, 95(3), 031501–7pp.
Abstract: In principle, the strong-interaction sector of the standard model is characterized by a unique renormalization-group-invariant (RGI) running interaction and a unique form for the dressed-gluonquark vertex, Gamma mu; but, whilst much has been learnt about the former, the latter is still obscure. In order to improve this situation, we use a RGI running-interaction that reconciles top-down and bottom-up analyses of the gauge sector in quantum chromodynamics (QCD) to compute dressed-quark gap equation solutions with 1,660,000 distinct Ansatze for Gamma mu. Each one of the solutions is then tested for compatibility with three physical criteria and, remarkably, we find that merely 0.55% of the solutions survive the test. Evidently, even a small selection of observables places extremely tight bounds on the domain of realistic vertex Ansatze. This analysis and its results should prove useful in constraining insightful contemporary studies of QCD and hadronic phenomena.
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