|
|
Forero, D. V., & Guzzo, M. M. (2011). Constraining nonstandard neutrino interactions with electrons. Phys. Rev. D, 84(1), 013002–7pp.
Abstract: We update the phenomenological constraints of the nonstandard neutrino interactions (NSNI) with electrons including in the analysis, for the first time, data from LAMPF, Krasnoyarsk, and the latest Texono observations. We assume that NSNI modify the cross section of elastic scattering of (anti) neutrinos off electrons, using reactor and accelerator data, and the cross section of the electron-positron annihilation, using the four LEP experiments, in particular, new data from DELPHI. We find more restrictive allowed regions for the NSNI parameters: -0.11< epsilon(eR)(ee) < 0.05 and -0.02 < epsilon(eL)(ee) < 0.09 (90% C.L.). We also recalculate the parameters of tauonic flavor obtaining -0.35 < epsilon(eR)(tau tau) < 0.50 and -0.51 < epsilon(eL)(tau tau) < 0.34 (90% C.L.). Although more severe than the limits already present in the literature, our results indicate that NSNI are allowed by the present data as a subleading effect, and the standard electroweak model continues consistent with the experimental panorama at 90% C.L. Further improvement on this picture will deserve a lot of engagement of upcoming experiments.
|
|
|
|
Fomichev, A. S., Mukha, I., Stepantsov, S. V., Grigorenko, L. V., Litvinova, E. V., Chudoba, V., et al. (2011). Lifetime of (26)S and a limit for its 2p decay energy. Int. J. Mod. Phys. E, 20(6), 1491–1508.
Abstract: The unknown isotope (26)S, expected to decay by two-proton (2p) emission, was studied theoretically and searched experimentally. The structure of this nucleus was examined within the relativistic mean field (RMF) approach. A method for taking into account the many-body structure in the three-body decay calculations was developed. The results of the RMF calculations were used as an input for the three-cluster decay model optimized for the study of a possible 2p decay branch of this nucleus. The experimental search for (26)S was performed by fragmentation of a 50.3 A MeV (32)S beam. No events of a particles table (26)S or (25)P (a presumably proton-unstable subsystem of (26)S) were observed. Based on the obtained production systematics, an upper half-life limit of T(1/2) < 79 ns was established from the time-of-flight through the fragment separator. Together with the theoretical lifetime estimates for two-proton decay, this gives a decay energy limit of Q(2p) > 640 keV for (26)S. Analogous limits for (25)P are found as T(1/2) < 38 ns and Q(p) > 110 keV. In the case that the one-proton emission is the main branch of the (26)S decay, a limit Q(2p) > 230 keV would follow for this nucleus. According to these limits, it is likely that (26)S resides in the picosecond life time range
|
|
|
|
Filipuzzi, A. (2011). Universality Violation In Leptonic W Decays: An Effective Field Theory Approach. Acta Physica Polonica B, 42(11), 2453–2459.
Abstract: We analyse the deviation from universality in leptonic W decays suggested by current PDG data within a general effective field theory approach. Considering the constraints to the New Physics effects coming from Electroweak precision observables we are able to set limits on the amount of universality violation that can be accounted for in a broad class of New Physics models. Our approach starts from a usual Single Operator analysis and extends up to considering the interplay of all the effective operators defined by our EFT.
|
|
|
|
Fidalgo, J., Lopez-Fogliani, D. E., Muñoz, C., & Ruiz de Austri, R. (2011). The Higgs sector of the μnu SSM and collider physics. J. High Energy Phys., 10(10), 020–33pp.
Abstract: The μnu SSM is a supersymmetric standard model that accounts for light neutrino masses and solves the μproblem of the MSSM by simply using right-handed neutrino superfields. Since this mechanism breaks R-parity, a peculiar structure for the mass matrices is generated. The neutral Higgses are mixed with the right- and left-handed sneutrinos producing 8x8 neutral scalar mass matrices. We analyse the Higgs sector of the μnu SSM in detail, with special emphasis in possible signals at colliders. After studying in general the decays of the Higges, we focus on those processes that are genuine of the μnu SSM, and could serve to distinguish it form other supersymmetric models. In particular, we present viable benchmark points for LHC searches. For example, we find decays of a MSSM-like Higgs into two lightest neutralinos, with the latter decaying inside the detector leading to displaced vertices, and producing final states with 4 and 8 b-jets plus missing energy. Final states with leptons and missing energy are also found.
|
|
|
|
Feroz, F., Cranmer, K., Hobson, M., Ruiz de Austri, R., & Trotta, R. (2011). Challenges of profile likelihood evaluation in multi-dimensional SUSY scans. J. High Energy Phys., 06(6), 042–23pp.
Abstract: Statistical inference of the fundamental parameters of supersymmetric theories is a challenging and active endeavor. Several sophisticated algorithms have been employed to this end. While Markov-Chain Monte Carlo (MCMC) and nested sampling techniques are geared towards Bayesian inference, they have also been used to estimate frequentist confidence intervals based on the profile likelihood ratio. We investigate the performance and appropriate configuration of MULTINEST, a nested sampling based algorithm, when used for profile likelihood-based analyses both on toy models and on the parameter space of the Constrained MSSM. We find that while the standard configuration previously used in the literarture is appropriate for an accurate reconstruction of the Bayesian posterior, the profile likelihood is poorly approximated. We identify a more appropriate MULTINEST configuration for profile likelihood analyses, which gives an excellent exploration of the profile likelihood (albeit at a larger computational cost), including the identification of the global maximum likelihood value. We conclude that with the appropriate configuration MULTINEST is a suitable tool for profile likelihood studies, indicating previous claims to the contrary are not well founded.
|
|
