Jimenez, R., Pena-Garay, C., & Verde, L. (2011). Is it possible to explore Peccei-Quinn axions from frequency-dependence radiation dimming? Phys. Lett. B, 703(3), 232–236.
Abstract: We explore how the Peccei-Quinn (PQ) axion parameter space can be constrained by the frequency-dependence dimming of radiation from astrophysical objects. To do so we perform accurate calculations of photon-axion conversion in the presence of a variable magnetic field. We propose several tests where the PQ axion parameter space can be explored with current and future astronomical surveys: the observed spectra of isolated neutron stars, occultations of background objects by white dwarfs and neutron stars, the light-curves of eclipsing binaries containing a white dwarf. We find that the lack of dimming of the light-curve of a detached eclipsing white dwarf binary recently observed, leads to relevant constraints on the photon-axion conversion. Current surveys designed for Earth-like planet searches are well matched to strengthen and improve the constraints on the PQ axion using astrophysical objects radiation dimming.
|
ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Escobar, C., et al. (2011). Search for squarks and gluinos using final states with jets and missing transverse momentum with the ATLAS detector in root s=7 TeV proton-proton collisions. Phys. Lett. B, 701(2), 186–203.
Abstract: A search for squarks and gluinos in final states containing jets, missing transverse momentum and no electrons or muons is presented. The data were recorded by the ATLAS experiment in root s = 7 TeV proton-proton collisions at the Large Hadron Collider. No excess above the Standard Model background expectation was observed in 35 pb(-1) of analysed data. Gluino masses below 500 GeV are excluded at the 95% confidence level in simplified models containing only squarks of the first two generations, a gluino octet and a massless neutralino. The exclusion increases to 870 GeV for equal mass squarks and gluinos. In MSUGRA/CMSSM models with tan beta = 3, A(0) = 0 and μ> 0, squarks and gluinos of equal mass are excluded below 775 GeV. These are the most stringent limits to date.
|
ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Escobar, C., et al. (2011). Search for high mass dilepton resonances in pp collisions at root s=7 TeV with the ATLAS experiment. Phys. Lett. B, 700(3-4), 163–180.
Abstract: This Letter presents a search for high mass e(+)e(-) or mu(+)mu(-) resonances in pp collisions at root s = 7 TeV at the LHC. The data were recorded by the ATLAS experiment during 2010 and correspond to a total integrated luminosity of similar to 40 pb(-1). No statistically significant excess above the Standard Model expectation is observed in the search region of dilepton invariant mass above 110 GeV. Upper limits at the 95% confidence level are set on the cross section times branching ratio of Z' resonances decaying to dielectrons and dimuons as a function of the resonance mass. A lower mass limit of 1.048 TeV on the Sequential Standard Model Z' boson is derived, as well as mass limits on Z* and E(6)-motivated Z' models.
|
Meloni, D., Morisi, S., & Peinado, E. (2011). Stability of dark matter from the D(4) x Z(2)(f) flavor group. Phys. Lett. B, 703(3), 281–287.
Abstract: We study a model based on the dihedral group D(4) in which the dark matter is stabilized by the interplay between a remnant Z(2) symmetry, of the same spontaneously broken non-abelian group, and an auxiliary Z(2)(f) introduced to eliminate unwanted couplings in the scalar potential. In the lepton sector the model is compatible with normal hierarchy only and predicts a vanishing reactor mixing angle, theta(13) = 0. Since m(nu 1) = 0, we also have a simple prediction for the effective mass in terms of the solar angle: vertical bar m(beta beta)vertical bar = vertical bar m(nu 2)vertical bar sin(2)theta circle dot similar to 10(-3) eV. There also exists a large portion of the model parameter space where the upper bounds on lepton flavor violating processes are not violated. We incorporate quarks in the same scheme finding that a description of the CKM mixing matrix is possible and that semileptonic K and D decays mediated by flavor changing neutral currents are under control.
|
Borexino Collaboration(Bellini, G. et al), & Pena-Garay, C. (2012). Absence of a day-night asymmetry in the Be-7 solar neutrino rate in Borexino. Phys. Lett. B, 707(1), 22–26.
Abstract: We report the result of a search for a day-night asymmetry in the Be-7 solar neutrino interaction rate in the Borexino detector at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy. The measured asymmetry is A(dn) = 0.001 +/- 0.012 (stat) +/- 0.007 (syst), in agreement with the prediction of MSW-LMA solution for neutrino oscillations. This result disfavors MSW oscillations with mixing parameters in the LOW region at more than 8.5 sigma. This region is, for the first time, strongly disfavored without the use of reactor anti-neutrino data and therefore the assumption of CPT symmetry. The result can also be used to constrain some neutrino oscillation scenarios involving new physics.
|