Di Valentino, E., Giusarma, E., Lattanzi, M., Mena, O., Melchiorri, A., & Silk, J. (2016). Cosmological axion and neutrino mass constraints from Planck 2015 temperature and polarization data. Phys. Lett. B, 752, 182–185.
Abstract: Axions currently provide the most compelling solution to the strong CP problem. These particles may be copiously produced in the early universe, including via thermal processes. Therefore, relic axions constitute a hot dark matter component and their masses are strongly degenerate with those of the three active neutrinos, as they leave identical signatures in the different cosmological observables. In addition, thermal axions, while still relativistic states, also contribute to the relativistic degrees of freedom, parameterized via N-eff. We present the cosmological bounds on the relic axion and neutrino masses, exploiting the full Planck mission data, which include polarization measurements. In the mixed hot dark matter scenario explored here, we find the tightest and more robust constraint to date on the sum of the three active neutrino masses, Sigma m nu < 0.136eV at 95% CL, as it is obtained in the very well-known linear perturbation regime. The Planck Sunyaev-Zeldovich cluster number count data further tightens this bound, providing a 95% CL upper limit of Sigma m nu < 0.126 eV in this very same mixed hot dark matter model, a value which is very close to the expectations in the inverted hierarchical neutrino mass scenario. Using this same combination of data sets we find the most stringent bound to date on the thermal axion mass, m(a) < 0.529 eV at 95% CL.
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Rinaldi, M., Scopetta, S., Traini, M., & Vento, V. (2016). Double parton scattering: A study of the effective cross section within a Light-Front quark model. Phys. Lett. B, 752, 40–45.
Abstract: We present a calculation of the effective cross section sigma(eff), an important ingredient in the description of double parton scattering in proton-proton collisions. Our theoretical approach makes use of a Light-Front quark model as a framework to calculate the double parton distribution functions at low-resolution scale. QCD evolution is implemented to reach the experimental scale. The obtained values of sigma(eff) in the valence region are consistent with the present experimental scenario, in particular with the sets of data which include the same kinematical range. However the result of the complete calculation shows a dependence of sigma(eff) on x(i), a feature not easily seen in the available data, probably because of their low accuracy. Measurements of sigma(eff) in restricted x(i) regions are addressed to obtain indications on double parton correlations, a novel and interesting aspect of the three dimensional structure of the nucleon.
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ATLAS Collaboration(Aad, G. et al), Alvarez Piqueras, D., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fernandez Martinez, P., et al. (2016). Constraints on non-Standard Model Higgs boson interactions in an effective Lagrangian using differential cross sections measured in the H ->gamma gamma decay channel at root s=8 TeV with the ATLAS detector. Phys. Lett. B, 753, 69–85.
Abstract: The strength and tensor structure of the Higgs boson's interactions are investigated using an effective Lagrangian, which introduces additional CP-even and CP-odd interactions that lead to changes in the kinematic properties of the Higgs boson and associated jet spectra with respect to the Standard Model. The parameters of the effective Lagrangian are probed using a fit to five differential cross sections previously measured by the ATLAS experiment in the H ->gamma gamma decay channel with an integrated luminosity of 20.3 fb(-1) at root s= 8 TeV. Inorder to perform a simultaneous fit to the five distributions, the statistical correlations between them are determined by re-analysing the H ->gamma gamma candidate events in the proton-proton collision data. No significant deviations from the Standard Model predictions are observed and limits on the effective Lagrangian parameters are derived. The statistical correlations are made publicly available to allow for future analysis of theories with non-Standard Model interactions.
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Cañas, B. C., Miranda, O. G., Parada, A., Tortola, M., & Valle, J. W. F. (2016). Updating neutrino magnetic moment constraints. Phys. Lett. B, 753, 191–198.
Abstract: In this paper we provide an updated analysis of the neutrino magnetic moments (NMMs), discussing both the constraints on the magnitudes of the three transition moments Lambda(i) and the role of the CP violating phases present both in the mixing matrix and in the NMM matrix. The scattering of solar neutrinos off electrons in Borexino provides the most stringent restrictions, due to its robust statistics and the low energies observed, below 1 MeV. Our new limit on the effective neutrino magnetic moment which follows from the most recent Borexino data is 3.1 x 10(-11) mu(B) at 90% C.L. This corresponds to the individual transition magnetic moment constraints: vertical bar Lambda(1)vertical bar <= 5.6 x10(-11)mu(B), vertical bar Lambda(2)vertical bar <= 4.0 x10(-11)mu(B), and vertical bar Lambda(3)vertical bar <= 3.1 x10(-11)mu B(90% C. L.), irrespective of any complex phase. Indeed, the incoherent admixture of neutrino mass eigenstates present in the solar flux makes Borexino insensitive to the Majorana phases present in the NMM matrix. For this reason we also provide a global analysis including the case of reactor and accelerator neutrino sources, presenting the resulting constraints for different values of the relevant CP phases. Improved reactor and accelerator neutrino experiments will be needed in order to underpin the full profile of the neutrino electromagnetic properties.
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Das, D., Dey, U. K., & Pal, P. B. (2016). S-3 symmetry and the quark mixing matrix. Phys. Lett. B, 753, 315–318.
Abstract: We impose an S-3 symmetry on the quark fields under which two of three quarks transform like a doublet and the remaining one as singlet, and use a scalar sector with the same structure of SU(2) doublets. After gauge symmetry breaking, a Z(2) subgroup of the S-3 remains unbroken. We show that this unbroken subgroup can explain the approximate block structure of the CKM matrix. By allowing soft breaking of the S-3 symmetry in the scalar sector, we show that one can generate the small elements, of quadratic or higher order in the Wolfenstein parametrization of the CKM matrix. We also predict the existence of exotic new scalars, with unconventional decay properties, which can be used to test our model experimentally.
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Wang, E., Xie, J. J., & Oset, E. (2016). chi(c0)(1P) decay into (Sigma)over-bar Sigma pi search of an I=1, 1/2(-) baryon state around (K)over-barN threshold. Phys. Lett. B, 753, 526–532.
Abstract: We present the theoretical study of the process chi(c0)(1P) -> (Sigma) over bar Sigma pi decay, by taking into account the pi Sigma and pi(Sigma) over bar final state interactions of the final meson-baryon pair based on the chiral unitary approach. We show that the process filters the isospin I = 1 in the pi Sigma channel and offers a reaction to test the existence of an I = 1 state with strangeness S = -1 and spin-parity J(p) = 1/2(-) around the (K) over barN threshold predicted by some theories and supported by some experiments.
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ATLAS Collaboration(Aad, G. et al), Alvarez Piqueras, D., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fernandez Martinez, P., et al. (2016). Measurements of four-lepton production in pp collisions at root s=8 TeV with the ATLAS detector. Phys. Lett. B, 753, 552–572.
Abstract: The four-lepton (4l, l = e, mu) production cross section is measured in the mass range from 80 to 1000GeV using 20.3 fb(-1)of data in pp collisions at root s = 8 TeV collected with the ATLAS detector at the LHC. The 4l events are produced in the decays of resonant Zand Higgs bosons and the nonresonant ZZcontinuum originating from q (q) over bar, gg, and qg initial states. A total of 476 signal candidate events are observed with a background expectation of 26.2 +/- 3.6 events, enabling the measurement of the integrated cross section and the differential cross section as a function of the invariant mass and transverse momentum of the four-lepton system. In the mass range above 180GeV, assuming the theoretical constraint on the q (q) over bar production cross section calculated with perturbative NNLO QCD and NLO electroweak corrections, the signal strength of the gluon-fusion component relative to its leading-order prediction is determined to be mu(gg) = 2.4 +/- 1.0(stat.) +/- 0.5(syst.) +/- 0.8(theory).
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Xie, J. J., & Oset, E. (2016). Role of the f(1)(1285) state in the J/ psi -> phi(K)over-barK* and J/psi -> phi f(1) (1285) decays. Phys. Lett. B, 753, 591–594.
Abstract: We study the role of the f(1)(1285) resonance in the decays of J/psi -> phi(K) over barK* and J/psi -> f(1) (1285). The theoretical approach is based on the results of chiral unitary theory where the f1(1285) resonance is dynamically generated from the K* (K) over bar -c.c. interaction. In order to further test the dynamical nature of the f(1)(1285) state, we investigate the J/psi -> phi(K) over barK* decay close to the (K) over barK* threshold and make predictions for the ratio of the invariant mass distributions of the J/psi -> phi(K) over barK* decay and the J/psi -> phi f(1)(1285) partial decay width with all the parameters of the mechanism fixed in previous studies. The results can be tested in future experiments and therefore offer new clues on the nature of the f(1) (1285) state.
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Chen, P., Ding, G. J., Gonzalez-Canales, F., & Valle, J. W. F. (2016). Generalized mu-tau reflection symmetry and leptonic CP violation. Phys. Lett. B, 753, 644–652.
Abstract: We propose a generalized mu-tau reflection symmetry to constrain the lepton flavor mixing parameters. We obtain a new correlation between the atmospheric mixing angle theta(23) and the “Dirac” CP violation phase delta(CP). Only in a specific limit our proposed CP transformation reduces to standard mu-tau reflection, for which theta(23) and delta(CP) are both maximal. The “Majorana” phases are predicted to lie at their CP-conserving values with important implications for the neutrinoless double beta decay rates. We also study the phenomenological implications of our scheme for present and future neutrino oscillation experiments including T2K, NO nu A and DUNE.
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Yamagata-Sekihara, J., Garcia-Recio, C., Nieves, J., Salcedo, L. L., & Tolos, L. (2016). Formation spectra of charmed meson-nucleus systems using an antiproton beam. Phys. Lett. B, 754, 26–32.
Abstract: We investigate the structure and formation of charmed meson--nucleus systems, with the aim of understanding the charmed meson-nucleon interactions and the properties of the charmed mesons in the nuclear medium. The (D) over bar mesic nuclei are of special interest, since they have tiny decay widths due to the absence of strong decays for the (D) over barN pair. Employing an effective model for the (D) over barN and DN interactions and solving the Klein-Gordon equation for (D) over bar and D in finite nuclei, we find that the D0-11B system has 1s and 2p mesic nuclear states and that the D0-11B system binds in a 1s state. In view of the forthcoming experiments by the PANDA and CBM Collaborations at the future FAIR facility and the J-PARC upgrade, we calculate the formation spectra of the [(D) over bar B--11] and [D-0-B-11] mesic nuclei for an antiproton beam on a C-12 target. Our results suggest that it is possible to observe the 2p D- mesic nuclear state with an appropriate experimental setup.
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