Nieves, J., & Sobczyk, J. E. (2017). In medium dispersion relation effects in nuclear inclusive reactions at intermediate and low energies. Ann. Phys., 383, 455–496.
Abstract: In a well-established many-body framework, successful in modeling a great variety of nuclear processes, we analyze the role of the spectral functions (SFs) accounting for the modifications of the dispersion relation of nucleons embedded in a nuclear medium. We concentrate in processes mostly governed by one-body mechanisms, and study possible approximations to evaluate the particle hole propagator using SFs. We also investigate how to include together SFs and long-range RPA-correlation corrections in the evaluation of nuclear response functions, discussing the existing interplay between both type of nuclear effects. At low energy transfers (<= 50 MeV), we compare our predictions for inclusive muon and radiative pion captures in nuclei, and charge-current (CC) neutrino-nucleus cross sections with experimental results. We also present an analysis of intermediate energy quasi-elastic neutrino scattering for various targets and both neutrino and antineutrino CC driven processes. In all cases, we pay special attention to estimate the uncertainties affecting the theoretical predictions. In particular, we show that errors on the a,,sigma(mu)/sigma(e) ratio are much smaller than 5%, and also much smaller than the size of the SF+RPA nuclear corrections, which produce significant effects, not only in the individual cross sections, but also in their ratio for neutrino energies below 400 MeV. These latter nuclear corrections, beyond Pauli blocking, turn out to be thus essential to achieve a correct theoretical understanding of this ratio of cross sections of interest for appearance neutrino oscillation experiments. We also briefly compare our SF and RPA results to predictions obtained within other representative approaches.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2017). Measurement of multi-particle azimuthal correlations in pp, p plus Pb and low-multiplicity Pb plus Pb collisions with the ATLAS detector. Eur. Phys. J. C, 77(6), 428–40pp.
Abstract: Multi-particle cumulants and corresponding Fourier harmonics are measured for azimuthal angle distributions of charged particles in pp collisions at root S = 5.02 and 13 TeV and in p + Pb collisions at root S-NN = 5.02 TeV, and compared to the results obtained for low-multiplicity Pb + Pb collisions at root S-NN = 2.76 TeV. These measurements aim to assess the collective nature of particle production. The measurements of multi-particle cumulants confirm the evidence for collective phenomena in p + Pb and low-multiplicity Pb + Pb collisions. On the other hand, the pp results for four-particle cumulants do not demonstrate collective behaviour, indicating that they may be biased by contributions from non-flow correlations. A comparison of multi-particle cumulants and derived Fourier harmonics across different collision systems is presented as a function of the charged-particle multiplicity. For a given multiplicity, the measured Fourier harmonics are largest in Pb + Pb, smaller in p + Pb and smallest in pp collisions. The pp results show no dependence on the collision energy, nor on the multiplicity.
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ANTARES Collaboration(Albert, A. et al), Barrios-Marti, J., Coleiro, A., Hernandez-Rey, J. J., Illuminati, G., Lotze, M., et al. (2017). An algorithm for the reconstruction of high-energy neutrino-induced particle showers and its application to the ANTARES neutrino telescope. Eur. Phys. J. C, 77(6), 419–11pp.
Abstract: A novel algorithm to reconstruct neutrino-induced particle showers within the ANTARES neutrino telescope is presented. The method achieves a median angular resolution of 6. for shower energies below 100TeV. Applying this algorithm to 6 years of data taken with theANTARES detector, 8 events with reconstructed shower energies above 10TeV are observed. This is consistent with the expectation of about 5 events from atmospheric backgrounds, but also compatible with diffuse astrophysical flux measurements by the IceCube collaboration, from which 2-4 additional events are expected. A 90% C.L. upper limit on the diffuse astrophysical neutrino flux with a value per neutrino flavour of E-2.Phi(90%) = 4.9 . 10(-8) GeV.cm(-2).s(-1).sr(-1) is set, applicable to the energy range from 23TeV to 7.8PeV, assuming an unbroken E-2 spectrum and neutrino flavour equipartition at Earth.
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Garcilazo, H., Valcarce, A., & Vijande, J. (2017). Stable bound states of N's, Lambda's and Xi's. Rev. Mex. Fis., 63(5), 411–422.
Abstract: We review our recent work about the stability of strange few-body systems containing N's, Lambda's, and Xi's. We make use of local central Yukawa-type Malfliet-Tjon interactions reproducing the low-energy parameters and phase shifts of the nucleon-nucleon system and the latest updates of the hyperon-nucleon and hyperon-hyperon ESCO8c Nijmegen potentials. We solve the three-and four-body bound-state problems by means of Faddeev equations and a generalized Gaussian variational method, respectively. The hypertriton, Lambda np(I)J(P) = (1/2)1/2(+), is bound by 144 keV; the recently discussed Lambda nn (I)J(P) = (1/2)1/2(+) system is unbound, as well as the Lambda Lambda nn (I)J(P) = (1)0(+) system, being just above threshold. Our results indicate that the Xi NN, Xi Xi N and Xi Xi NN systems with maximal isospin might be bound.
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Botella, F. J., Branco, G. C., Nebot, M., Rebelo, M. N., & Silva-Marcos, J. I. (2017). Vector-like quarks at the origin of light quark masses and mixing. Eur. Phys. J. C, 77(6), 408–14pp.
Abstract: We show how a novel fine-tuning problem present in the Standard Model can be solved through the introduction of a Z(6) flavour symmetry, together with three Q = -1/3 quarks, three Q = 2/3 quarks, as well as a complex singlet scalar. The Z(6) symmetry is extended to the additional fields and it is an exact symmetry of the Lagrangian, only softly broken in the scalar potential, in order to avoid the domain-wall problem. Specific examples are given and a phenomenological analysis of the main features of the model is presented. It is shown that even for vector-like quarks with masses accessible at the LHC, one can have realistic quark masses and mixing, while respecting the strict constraints on processes arising from flavour changing neutral currents. The vector-like quark decay channels are also described.
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