Search results for "partícules"
showing 10 items of 522 documents
Astrophysical bound on the majoron-Higgs-boson coupling
1989
Abstract We show that the coupling of the “standard” Higgs boson to majorons, that could lead to a very fast decay of the neutral Higgs scalar to invisible modes, can be bounded using astrophysical arguments. We discuss the relevance of this bound for low-energy phenomenology related to majoron production. The bound so obtained may also jeopardize the stability of the VEV hierarchy in the doublet and triplet majoron models if the mass of the top quark is less than the W mass. A similar analysis may be applied to other models which exhibit Goldstone-or pseudo-Goldstone-bosons in the spectrum.
Neutrino masses and their ordering: global data, priors and models
2018
We present a Bayesian analysis of the combination of current neutrino oscillation, neutrinoless double beta decay and CMB observations. Our major goal is to carefully investigate the possibility to single out one neutrino mass ordering, Normal Ordering or Inverted Ordering, with current data. Two possible parametrizations (three neutrino masses versus the lightest neutrino mass plus the two oscillation mass splittings) and priors (linear versus logarithmic) are examined. We find that the preference for NO is only driven by neutrino oscillation data. Moreover, the values of the Bayes factor indicate that the evidence for NO is strong only when the scan is performed over the three neutrino ma…
Dark radiation sterile neutrino candidates after Planck data
2013
Recent Cosmic Microwave Background (CMB) results from the Planck satellite, combined with previous CMB data and Hubble constant measurements from the Hubble Space Telescope, provide a constraint on the effective number of relativistic degrees of freedom 3.62(-0.48)(+0.50) at 95% CL. New Planck data provide a unique opportunity to place limits on models containing relativistic species at the decoupling epoch. We present here the bounds on sterile neutrino models combining Planck data with galaxy clustering information. Assuming N-eff active plus sterile massive neutrino species, in the case of a Planck+WP+HighL+HST analysis we find m(nu,sterile)(eff) < 0.36 eV and 3.14 < N-eff < 4.15 at 95% …
A search for neutrino emission from the Fermi bubbles with the ANTARES telescope
2014
Adrián-Martínez, S. et al.
Cosmological lepton asymmetry with a nonzero mixing angle \theta13
2012
While the baryon asymmetry of the Universe is nowadays well measured by cosmological observations, the bounds on the lepton asymmetry in the form of neutrinos are still significantly weaker. We place limits on the relic neutrino asymmetries using some of the latest cosmological data, taking into account the effect of flavor oscillations. We present our results for two different values of the neutrino mixing angle \theta_{13}, and show that for large \theta_{13} the limits on the total neutrino asymmetry become more stringent, diluting even large initial flavor asymmetries. In particular, we find that the present bounds are still dominated by the limits coming from Big Bang Nucleosynthesis, …
Search for the Standard Model Higgs Boson in the Diphoton Decay Channel with 4.9 fb−1 of pp Collision Data at s√=7 TeV with ATLAS
2012
A search for the standard model Higgs boson is performed in the diphoton decay channel. The data used correspond to an integrated luminosity of 4.9 fb(-1) collected with the ATLAS detector at the Large Hadron Collider in proton-proton collisions at a center-of-mass energy of root s = 7 TeV. In the diphoton mass range 110-150 GeV, the largest excess with respect to the background-only hypothesis is observed at 126.5 GeV, with a local significance of 2.8 standard deviations. Taking the look-elsewhere effect into account in the range 110-150 GeV, this significance becomes 1.5 standard deviations. The standard model Higgs boson is excluded at 95% confidence level in the mass ranges of 113-115 G…
Combined search for the Standard Model Higgs boson using up to 4.9 fb-1 of pp collision data at √(s)=7 TeV with the ATLAS detector at the LHC
2012
A combined search for the Standard Model Higgs boson with the ATLAS experiment at the LHC using datasets corresponding to integrated luminosities from 1.04 fb(-1) to 4.9 fb(-1) of pp collisions collected at root s = 7 TeV is presented. The Higgs boson mass ranges 112.9-115.5 GeV, 131-238 GeV and 251-466 GeV are excluded at the 95% confidence level (CL), while the range 124-519 GeV is expected to be excluded in the absence of a signal. An excess of events is observed around m(H) similar to 126 GeV with a local significance of 3.5 standard deviations (sigma). The local significances of H -> gamma, H -> ZZ(()*()) -> l(+)l(-)l'(+)l'(-) and H -> WW(*()) l(+)nu l'(-)(nu) over bar, the three most …
Combined search for the Standard Model Higgs boson in pp collisions at root s=7 TeV with the ATLAS detector
2012
A combined search for the Standard Model Higgs boson with the ATLAS detector at the LHC is presented. The data sets used correspond to integrated luminosities from 4.6 fb(-1) to 4.9 fb(-1) of proton-proton collisions collected at root s = 7 TeV in 2011. The Higgs boson mass ranges of 111.4 GeV to 116.6 GeV, 119.4 GeV to 122.1 GeV, and 129.2 GeV to 541 GeV are excluded at the 95% confidence level, while the range 120 GeV to 560 GeV is expected to be excluded in the absence of a signal. An excess of events is observed at Higgs boson mass hypotheses around 126 GeV with a local significance of 2.9 standard deviations (sigma). The global probability for the background to produce an excess at lea…
Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC
2012
A search for the Standard Model Higgs boson in proton-proton collisions with the ATLAS detector at the LHC is presented. The datasets used correspond to integrated luminosities of approximately 4.8 fb(-1) collected at, root s = 7 TeV in 2011 and 5.8 fb(-1) at root s = 8 TeV in 2012. Individual searches in the channels H -> ZZ(()*()) -> 4l, H -> gamma gamma and H -> WW (()*()) -> ev μv in the 8 TeV data are combined with previously published results of searches for H -> ZZ(()*()), WW(*()), b (b) over bar and tau(+)tau(-) in the 7 TeV data and results from improved analyses of the H -> ZZ(()*()) -> 4l and H -> gamma gamma channels in the 7 TeV data. Clear evidence for the production of a neut…
Search for new physics in the dijet mass distribution using 1 fb-1 of pp collision data at √(s)=7 TeV collected by the ATLAS detector
2012
Invariant mass distributions of jet pairs (dijets) produced in LHC proton-proton collisions at a centre-of-mass energy root s = 7 TeV have been studied using a data set corresponding to an integrated luminosity of 1.0 fb(-1) recorded in 2011 by ATLAS. Dijet masses up to similar to 4 TeV are observed in the data, and no evidence of resonance production over background is found. Limits are set at 95% C.L. for several new physics hypotheses: excited quarks are excluded for masses below 299 TeV, axigluons are excluded for masses below 3.32 TeV. and colour octet scalar resonances are excluded for masses below 1.92 TeV.