1,721,204 research outputs found
Searches for sterile neutrinos (and other light particles)
No full textFuture neutrino and cosmological experiments will perform powerful searches for new light particles. After a general introduction we discuss how a new light fermion ('sterile neutrino') could manifest
Sommerfeld corrections to type-II and type-III leptogenesis
No full textWe study thermal leptogenesis from decays of the electroweak triplets that mediate neutrino masses in type-II and type-III see-saw. We find that Sommerfeld corrections reduce the baryon asymmetry by similar to 30%, and that successful leptogenesis needs triplets heavier than 1.6 TeV, beyond the discovery reach of LHC. (C) 2008 Elsevier B.V. All rights reserved
Naturalness of supersymmetric models
No full textAfter presenting a simple procedure for testing naturalness (similar to Bayesian inference and not more subjective than it) we show that LEP2 experiments pose a naturalness problem for `conventional' supersymmetric models. About 95% of the parameter space of minimal supergravity MSSM is excluded by LEP2 experiments. Moreover in this model electroweak baryogenesis, or detectable supersymmetric corrections to mixing of K and B mesons, are possible only in very small corners of the parameter space. The naturalness problem is stronger in gauge mediation models, expecially with light messengers. We recall some possible explanations (different from an improbable numerical accident) of why supersymmetry has not (yet?) been found
Dark Matter Interpretations of the Cosmic-Ray e(+/-) Excesses
No full textThe cosmic-ray excess observed by PAMELA in the positron fraction and by FERMI and HESS in e(-) + e(+) can be interpreted in terms of DM annihilations or decays. We summarize the main possibilities and their possible tests
Oscillations of three neutrinos with all Delta m(2) similar to 10(-3) eV(2)
No full textOscillations of three neutrinos with all squared mass splittings around 10(-3) eV(2) are not firmly excluded by solar neutrino experiments. We carefully verify that they are also perfectly compatible with atmospheric neutrino experiments: due to accidental reasons the SuperKamiokande experiment is rather insensitive to 'solar' nu(e)/nu(mu) oscillations, even if some characteristic small effects could become visible with more statistics. This pattern of oscillations can be excluded by new solar experiments, or cleanly discovered at KAMLAND. We also perform a fit of the most recent atmospheric SK data within the usual assumption that 'solar' effects are negligible
Charge and colour breaking minima and constraints on the MSSM parameters
No full textThe MSSM potential can have unphysical minima deeper than the physically acceptable one. We point out that their presence is quite generic in SO(10) unification with supergravity mediated soft terms. However, at least for moderate values of tan beta, the physically acceptable vacuum has a lifetime longer than the universe age. Furthermore, by discussing the evolution of the universe in an inflationary scenario, we show that the correct vacuum is the natural expectation, This is not the tendency in different cases of unphysical minima. Even in the SO(10) case, the weak assumptions necessary for this may prevent to use the direction for baryogenesis a la Affleck-Dine
Interpreting the LSND anomaly: sterile neutrinos or CPT-violation or...?
No full textWe first study how sterile neutrinos can fit the 5sigma bar-nu_mu --> bar-nu_e LSND anomaly: 3+1 solutions give a poor fit, but better than than 2+2 solutions (the best fit regions are somewhat different, so that MiniBoone could discriminate). If instead MiniBoone will find no nu_mu --> nu_e signal, we will have a hint for CPT violation. Already now, unlike sterile neutrinos, CPT-violating neutrino masses can nicely accomodate all safe and unsafe data. We study how much CPT must be conserved according to atmospheric and K2K data and list which CPT-violating signals could be discovered by forthcoming solar and long-baseline experiments.We first study how sterile neutrinos can fit the 5 σ ν ̄ μ → ν ̄ e LSND anomaly: 2+2 solutions are strongly disfavoured by solar and atmospheric data, while 3+1 solutions can still give a poor fit (for a specific range of oscillation parameters, to be tested by MiniBooNE). If MiniBooNE will see no ν μ → ν e transitions, we will have a hint for CPT violation. Already now, unlike sterile neutrinos, CPT-violating neutrino masses can accommodate all safe and unsafe data. We study how much CPT must be conserved according to atmospheric and K2K data and list which CPT-violating signals could be discovered by forthcoming solar and long-baseline experiments.We first study how sterile neutrinos can fit the 5sigma bar-nu_mu --> bar-nu_e LSND anomaly: 2+2 solutions are strongly disfavoured by solar and atmospheric data, while 3+1 solutions can still give a poor fit (for a specific range of oscillation parameters, to be tested by MiniBooNE). If instead MiniBoone will find no nu_mu --> nu_e signal, we will have a hint for CPT violation. Already now, unlike sterile neutrinos, CPT-violating neutrino masses can nicely accomodate all safe and unsafe data. We study how much CPT must be conserved according to atmospheric and K2K data and list which CPT-violating signals could be discovered by forthcoming solar and long-baseline experiments
Two-loop heavy top corrections to the b -> s gamma decay
No full textWe compute the two-loop corrections to the coefficient of the b --> s gamma magnetic penguin present in the limits of heavy top and/or heavy Higgs. These kinds of corrections affect in a significant way the observables measured at LEP. On the contrary we find that, due to a numerical accident, the correction to BR(B --> X(s)gamma) is negligible (below the 1% level far any possible value of the Higgs mass) when the leading order result is expressed in the usual way in terms of the semileptonic BR(B --> X-c). (C) 1998 Elsevier Science B.V
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