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Register a new userImplications of Quark-Lepton Symmetry for Neutrino Masses and Oscillations
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T. Goldman
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We identify a plausible scenario based on quark-lepton symmetry which correlates long baseline oscillations with maximal mixing to sterile neutrinos. The implication for the Sudbury Neutrino Observatory (SNO) is that the neutral current signal will be found to suffer the same suppression from the Standard Solar Model prediction as obtains for the charged current signal. Flavor mixing among active neutrinos is expected to occur on shorter baselines with smaller mixing amplitudes.
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We apply the GiBUU model to questions relevant for current and future neutrino long-baseline experiments, we address in particular the relevance of charged-current reactions for neutrino disappearance experiments. A correct identification of charged-current quasielastic (CCQE) events - which is the signal channel in oscillation experiments - is relevant for the neutrino energy reconstruction and thus for the oscillation result. We show that about 20% of the quasielastic cross section is misidentified in present-day experiments and has to be corrected for by means of event generators. Furthermore, we show that also a significant part of 1pi+ (> 40%) events is misidentified as CCQE mainly caused by the pion absorption in the nucleus. We also discuss the dependence of both of these numbers on experimental detection thresholds. We further investigate the influence of final-state interactions on the neutrino energy reconstruction.
We discuss first the flavor mixing of the quarks, using the texture zero mass matrices. Then we study a similar model for the mass matrices of the leptons. We are able to relate the mass eigenvalues of the charged leptons and of the neutrinos to the mixing angles and can predict the masses of the neutrinos. We find a normal hierarchy - the masses are 0.004 eV, 0.01 eV and 0.05 eV. The atmospheric mixing angle is given by the mass ratios of the charged leptons and the neutrinos. we find about 40 degrees, consistent with the experiments. The mixing element, connecting the first neutrino wit the electron, is predicted to be 0.05. This prediction can soon be checked by the Daya Bay experiment.
We discuss the interplay between lepton asymmetry L and neutrino oscillations in the early Universe. Neutrino oscillations may suppress or enhance previously existing L. On the other hand L is capable to suppress or enhance neutrino oscillations. The mechanism of L enhancement in MSW resonant neutrino oscillations in the early Universe is numerically analyzed. L cosmological effects through neutrino oscillations are discussed. We discuss how L may change the cosmological BBN constraints on neutrino and show that BBN model with electron-sterile neutrino oscillations is extremely sensitive to L - it allows to obtain the most stringent constraints on L value. We discuss also the cosmological role of active-sterile neutrino mixing and L in connection with the indications about additional relativistic density in the early Universe, pointed out by BBN, CMB and LSS data and the analysis of global neutrino data.
We propose a framework that addresses the origin of neutrino mass, explains the observed discrepancies in the electron and the muon anomalous magnetic moments (AMMs) data and incorporates the dark matter (DM) relic abundance. Both the neutrino mass and the lepton AMMs are generated at one-loop level mediated by a common set of beyond the Standard Model (SM) states. In this class of models, the SM is extended with vector-like charged fermion and scalar multiplets, all odd under an imposed $mathcal{Z}_2$ symmetry, which stabilizes the fermionic or scalar DM candidate residing in one of them. Two scalar multiplets appear in the AMM loops, thus allowing for different signs of their contributions, in agreement with the observed discrepancies which are of opposite sign for electron and muon. The vector-like fermions give rise to large new physics contributions to the lepton AMMs via chirally enhanced terms that are proportional to their mass. To demonstrate the viability of this framework, we perform a detailed study of a particular model for which a fit to the neutrino masses and mixing together with lepton AMMs are provided. Furthermore, DM phenomenology and collider signatures are explored.
Reliable values of quark and lepton masses are important for model building at a fundamental energy scale, such as the Fermi scale M_Z approx 91.2 GeV and the would-be GUT scale Lambda_GUT sim 2 times 10^16 GeV. Using the latest data given by the Particle Data Group, we update the running quark and charged-lepton masses at a number of interesting energy scales below and above M_Z. In particular, we take into account the possible new physics scale (mu sim 1 TeV) to be explored by the LHC and the typical seesaw scales (mu sim 10^9 GeV and mu sim 10^12 GeV) which might be relevant to the generation of neutrino masses. For illustration, the running masses of three light Majorana neutrinos are also calculated. Our up-to-date table of running fermion masses are expected to be very useful for the study of flavor dynamics at various energy scales.
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