119109759
Q(6) flavor symmetry model for the extension of the minimal standard model by three right-handed sterile neutrinos
The extension of the minimal standard model by three right-handed sterile neutrinos with masses smaller than the electroweak scale (nu MSM) is discussed in a Q(6) flavor symmetry framework. The lightness of the keV sterile neutrino and the near mass degeneracy of two heavier sterile neutrinos are naturally explained by exploiting group properties of Q(6). A normal hierarchical mass spectrum and an approximately mu-tau symmetric mass matrix are predicted for three active neutrinos. Nonzero theta(13) can be obtained together with a deviation of theta(23) from the maximality, where both mixing angles are consistent with the latest global data including T2K and MINOS results. Furthermore, the tiny active-sterile mixing is related to the mass ratio between the lightest active and lightest sterile neutrinos.
122049951
MCMC SAMPLING IN THE GLOBAL ANALYSIS OF SOLAR AND REACTOR NEUTRINO DATA
We present a global analysis of latest solar and reactor neutrino data in the three-neutrino mixing scheme by using both the simple grid scanning and the Markov Chain Monte Carlo (MCMC) sampling methods. Accuracy and efficiency of the two sampling methods are compared and advantages of the latter are discussed. The fitting results of three oscillation parameters theta(12), theta(13) and Delta m(21)(2) are provided with both old and new evaluations of the reactor antineutrino flux. Possible correlation between the fitting parameters is also discussed.
118641290
Direct detection of the cosmic neutrino background including light sterile neutrinos
Current cosmological data drop an interesting hint about the existence of sub-eV sterile neutrinos, which should be a part of the cosmic neutrino background (C nu B). We point out that such light sterile neutrinos may leave a distinct imprint on the electron energy spectrum in the capture of relic electron neutrinos by means of radioactive beta-decaying nuclei. We examine possible signals of sterile neutrinos relative to active neutrinos, characterized by their masses and sensitive to their number densities, in the reaction nu(e) + (3)H -> (3)He + e(-) against the corresponding tritium beta decay. We stress that this kind of direct laboratory detection of the C nu B and its sterile component might not be hopeless in the long term. (C) 2010 Elsevier B.V. All rights reserved.
118606894
Possible capture of keV sterile neutrino dark matter on radioactive beta-decaying nuclei
There exists an observed "desert" spanning six orders of magnitude between O(0.5) eV and O(0.5) MeV in the fermion mass spectrum. We argue that it might accommodate one or more keV sterile neutrinos as a natural candidate for warm dark matter. To illustrate this point of view, we simply assume that there is one key sterile neutrino nu(4) and its flavor eigenstate nu(s) weakly mixes with three active neutrinos. We clarify different active-sterile neutrino mixing factors for the radiative decay of nu(4) and beta decays in a self-consistent parametrization. A direct detection of this keV sterile neutrino dark matter in the laboratory is in principle possible since the nu(4) component of nu(e) can leave a distinct imprint on the electron energy spectrum when it is captured on radioactive beta-decaying nuclei. We carry out an analysis of its signatures in the capture reactions nu(e) + H-3 -> He-3 + e(-) and nu(e) + Ru-106 -> Rh-106 + e(-) against the beta-decay backgrounds, and conclude that this experimental approach might not be hopeless in the long run. (C) 2010 Elsevier B.V. All rights reserved.
117727003
Neutrinos as Hot or Warm Dark Matter
Both active and sterile sub-eV neutrinos can serve for hot dark matter (DM). On the other hand, keV sterile neutrinos could be a good candidate for warm DM. The beta-decaying (e.g., H-3 and Ru-106) and EC-decaying (e.g., Ho-163) nuclei are considered as the most promising targets to capture those extremely low energy neutrinos and antineutrinos, respectively. We calculate the capture rates of relic electron neutrinos and antineutrinos against the corresponding beta-decay or EC-decay backgrounds in different flavor mixing schemes. We stress that such direct laboratory measurements of hot or warm DM might not be hopeless in the long term.
118445342
Shifts of neutrino oscillation parameters in reactor antineutrino experiments with non-standard interactions
We discuss reactor antineutrino oscillations with non-standard interactions (NSIs) at the neutrino production and detection processes. The neutrino oscillation probability is calculated with a parametrization of the NSI parameters by splitting them into the averages and differences of the production and detection processes respectively. The average parts induce constant shifts of the neutrino mixing angles from their true values, and the difference parts can generate the energy (and baseline) dependent corrections to the initial mass-squared differences. We stress that only the shifts of mass-squared differences are measurable in reactor antineutrino experiments. Taking hangmen Underground Neutrino Observatory (JUNO) as an example, we analyze how NSIs influence the standard neutrino measurements and to what extent we can constrain the NSI parameters. (C) 2014 The Authors. Published by Elsevier B.V.
119292019
Combining QCD and electroweak corrections to dilepton production in FEWZ
We combine the next-to-next-to-leading order (NNLO) QCD corrections to lepton-pair production through the Drell-Yan mechanism with the next-to-leading order (NLO) electroweak corrections within the framework of the FEWZ simulation code. Control over both sources of higher-order contributions is necessary for measurements where percent-level theoretical predictions are crucial, and in phase-space regions where the NLO electroweak corrections grow large. The inclusion of both corrections in a single simulation code eliminates the need to separately incorporate such effects as final-state radiation and electroweak Sudakov logarithms when comparing many experimental results to theory. We recalculate the NLO electroweak corrections in the complex-mass scheme for both massless and massive final-state leptons, and modify the QCD corrections in the original FEWZ code to maintain consistency with the complex-mass scheme to the lowest order. We present phenomenological results for LHC studies that include both NNLO QCD and NLO electroweak corrections. In addition, we study several interesting kinematics features induced by experimental cuts in the distribution of photon radiation at the LHC.
119238864
Up sector of minimal flavor violation: top quark properties and direct D meson CP violation
A bstractMinimal Flavor Violation in the up-type quark sector leads to particularly interesting phenomenology due to the interplay of flavor physics in the charm sector and collider physics from flavor changing processes in the top sector. We study the most general operators that can affect top quark properties and D meson decays in this scenario, concentrating on two CP violating operators for detailed studies. The consequences of these effective operators on charm and top flavor changing processes are generically small, but can be enhanced if there exists a light flavor mediator that is a Standard Model gauge singlet scalar and transforms under the flavor symmetry group. This flavor mediator can satisfy the current experimental bounds with a mass as low as tens of GeV and explain observed D-meson direct CP violation. Additionally, the model predicts a non-trivial branching fraction for a top quark decay that would mimic a dijet resonance.
119209195
Generalized Froggatt–Nielsen mechanism
We propose a Generalized Froggatt–Nielsen mechanism in which the GUT gauge symmetry breaking and the generation of hierarchical flavor structure have the same origin. Assuming universality conditions for coefficients corresponding to different contractions, we can get the realistic standard model mass hierarchy and mixings in SU(5) GUT model as well as in SO(10) GUT model in several ways. With very free parameters, the Generalized Froggatt–Nielsen mechanism is very predictive and it can be very useful in GUT model building as well as in solving the flavor puzzle in standard model.
18559665
Topological sigma-models with H-flux and twisted generalized complex manifolds
We study the topological sector of N = 2 sigma-models with HH-flux. It has been known for a long time that the target-space geometry of these theories is not Kahler and can be described in terms of a pair of complex structures, which do not commute, in general, and are parallel with respect to two different connections with torsion. Recently an alternative description of this geometry was found, which involves a pair of commuting twisted generalized complex structures on the target space. In this paper, we define and study the analogs of A and B-models for N = 2 sigma-models with HH-flux and show that the results are naturally expressed in the language of twisted generalized complex geometry. For example, the space of topological observables is given by the cohomology of a Lie algebroid associated to one of the two twisted generalized complex structures. We determine the topological scalar product, which endows the algebra of observables with the structure of a Frobenius algebra. We also discuss mirror symmetry for twisted generalized Calabi-Yau manifolds.
102486763
High precision predictions for exclusive V H production at the LHC
A bstractWe present a resummation-improved prediction for pp → V H + 0 jets at the Large Hadron Collider. We focus on highly-boosted final states in the presence of jet veto to suppress the $ t\overline{t} $ background. In this case, conventional fixed-order calculations are plagued by the existence of large Sudakov logarithms $ \alpha_s^n{\log^m}\left( {{{{p_T^{\mathrm{veto}}}} \left/ {Q} \right.}} \right) $ for Q ~ mV + mH which lead to unreliable predictions as well as large theoretical uncertainties, and thus limit the accuracy when comparing experimental measurements to the Standard Model. In this work, we show that the resummation of Sudakov logarithms beyond the next-to-next-to-leading-log accuracy, combined with the next-to-next-to-leading order calculation, reduces the scale uncertainty and stabilizes the perturbative expansion in the region where the vector bosons carry large transverse momentum. Our result improves the precision with which Higgs properties can be determined from LHC measurements using boosted Higgs techniques.