1,242 research outputs found

    Next-to-leading order corrections to gauge-mediated gaugino masses

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    We compute the next-to-leading order corrections to the gaugino masses MiM_i in gauge-mediated models for generic values of the messenger masses M and discuss the predictions of unified messenger models. If M<100 TeV there can be up to 10% corrections to the leading order relations Mi∝αiM_i\propto \alpha_i. If the messengers are heavier there are only few % corrections. We also study the messenger corrections to gauge coupling unification: as a result of cancellations dictated by supersymmetry, the predicted value of the strong coupling constant is typically only negligibly increased

    The golden ratio prediction for the solar neutrino mixing

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    We present a simple texture that predicts the cotangent of the solar neutrino mixing angle to be equal to the golden ratio. This prediction is 1.4 standard deviations below the present best-fit value and final SNO and KamLAND data could discriminate it from tri-bi-maximal mixing. The neutrino mass matrix is invariant under a Z_2 x Z'_2 symmetry: that geometrically is a reflection along the diagonal of the golden rectangle. Assuming an analogous structure in the quark sector suggests a golden prediction for the Cabibbo angle, theta_C = pi/4- theta_12 = 13.3 degree, up to uncertainties comparable to V_{ub}.Comment: 5 pages. Final version, to appear on PR

    Multi-muon events at the Tevatron: a hidden sector from hadronic collisions

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    Intrigued by some features of a small but significant fraction of the multi-muon events recently published by the CDF collaboration, we show an explicit attempt to describe them in terms of a light scalar singlet ϕ\phi which communicates with the standard quarks either through a heavy scalar or a heavy fermion exchange. As suggested in arXiv:0810.7530, the singlet ϕ\phi has a chain decay into a final state made of four ττˉ\tau\bar{\tau} pairs. We can simulate most of the muon properties of the selected sample of events. Some of these properties adhere rather well to the already published data; others should allow a decisive test of the proposed interpretation. Assuming that the test is positively passed, we show how the PAMELA excess can be fitted by the annihilation of a TeV Dark Matter particle that communicates with the Standard Model via the new light singlet(s).Comment: 19 pp, v2: small changes, agrees with the published versio

    Massive and Massless Neutrinos on Unbalanced Seesaws

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    The observation of neutrino oscillations requires new physics beyond the standard model (SM). A SM-like gauge theory with p lepton families can be extended by introducing q heavy right-handed Majorana neutrinos but preserving its SU(2)_L x U(1)_Y gauge symmetry. The overall neutrino mass matrix M turns out to be a symmetric (p+q) x (p+q) matrix. Given p>q, the rank of M is in general equal to 2q, corresponding to 2q non-zero mass eigenvalues. The existence of (p-q) massless left-handed Majorana neutrinos is an exact consequence of the model, independent of the usual approximation made in deriving the Type-I seesaw relation between the effective p x p light Majorana neutrino mass matrix M_\nu and the q x q heavy Majorana neutrino mass matrix M_R. In other words, the numbers of massive left- and right-handed neutrinos are fairly matched. A good example to illustrate this seesaw fair play rule is the minimal seesaw model with p=3 and q=2, in which one massless neutrino sits on the unbalanced seesaw.Comment: RevTex 8 pages, 1 PS figure. Two crucial references adde

    Anthropic solution to the magnetic muon anomaly: the charged see-saw

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    We present models of new physics that can explain the muon g-2 anomaly in accord with with the assumption that the only scalar existing at the weak scale is the Higgs, as suggested by anthropic selection. Such models are dubbed "charged see-saw" because the muon mass term is mediated by heavy leptons. The electroweak contribution to the g-2 gets modified by order one factors, giving an anomaly of the same order as the observed hint, which is strongly correlated with a modification of the Higgs coupling to the muon.Comment: 21 pages, many equations despite the first word in the title. v3: loop function G_WN corrected, conclusions unchange

    Parameters' domain in three flavour neutrino oscillations

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    We consider analytically the domain of the three mixing angles Θij\Theta_{ij} and the CP phase ÎŽ\delta for three flavour neutrino oscillations both in vacuum and matter. Similarly to the quark sector, it is necessary and sufficient to let all the mixing angles Θ12,Θ13,Θ23\Theta_{12},\Theta_{13},\Theta_{23} and ÎŽ\delta be in the range and 0≀Ύ<2π0 \leq \delta < 2 \pi, respectively. To exploit the full range of ÎŽ\delta will be important in future when more precise fits are possible, even without CP violation measurements. With the above assumption on the angles we can restrict ourselves to the natural order of masses m1<m2<m3m_1<m_2<m_3. Considerations of the mass schemes with some negative ÎŽm2\delta m^2's, though for some reasons useful, are not necessary from the point of view of neutrino oscillation parametrization and cause double counting only. These conclusions are independent of matter effects.Comment: references added, to appear in PL

    Muon and Tau Neutrinos Spectra from Solar Flares

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    Solar neutrino flares and mixing are considered. Most power-full solar flare as the ones occurred on 23th February 1956, September 29th 1989, 28th October and on 2nd-4th November 2003 are sources of cosmic rays, X, gamma and neutrino bursts. These flares took place both on front or in the edge and in the hidden solar disk. The observed and estimated total flare energy should be a source of a prompt secondary neutrino burst originated, by proton-proton-pion production on the sun itself; a more delayed and spread neutrino flux signal arise by the solar charged flare particles reaching the terrestrial atmosphere. Our first estimates of neutrino signals in largest underground detectors hint for few events in correlation with, gamma,radio onser. Our approximated spectra for muons and taus from these rare solar eruption are shown over the most common background. The muon and tau signature is very peculiar and characteristic over electron and anti-electron neutrino fluxes. The rise of muon neutrinos will be detectable above the minimal muon threshold of 113 MeV. The rarest tau appearence will be possible only for hardest solar neutrino energies above 3.471 GeVComment: 14 pages, 4 figures, Vulcano Conference 200
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