119230665
TeV-scale Type-II Seesaw Models and Possible Collider Signatures
A natural extension of the standard model to accommodate massive neutrinos is to introduce one Higgs triplet and three right-handed Majorana neutrinos, leading to a 6×6 neutrino mass matrix. We show that three light Majorana neutrinos (i.e., the mass eigenstates of νe, νμ and ντ) are exactly massless, if and only if $M_{L} = M_{\rm D}M^{-1}_{\rm R}M^{T}_{\rm D}$ exactly holds in this seesaw model. We propose three simple Type-II seesaw scenarios with broken A4 × U(1)x flavor symmetry to interpret the observed neutrino mass spectrum and neutrino mixing pattern. Such a TeV-scale neutrino model can be tested in two complementary ways: (1) searching for possible collider signatures of lepton number violation induced by the right-handed Majorana neutrinos and doubly-charged Higgs particles; and (2) searching for possible consequences of unitarity violation of the 3 × 3 neutrino mixing matrix in the future long-baseline neutrino oscillation experiments.
118662547
Compromise between neutrino masses and collider signatures in the type-II seesaw model
A natural extension of the standard $\mathrm{SU}(2{)}_{\mathrm{L}}\ifmmode\times\else\texttimes\fi{}\mathrm{U}(1{)}_{\mathrm{Y}}$ gauge model to accommodate massive neutrinos is to introduce one Higgs triplet and three right-handed Majorana neutrinos, leading to a $6\ifmmode\times\else\texttimes\fi{}6$ neutrino mass matrix which contains three $3\ifmmode\times\else\texttimes\fi{}3$ submatrices, ${M}_{\mathrm{L}}$, ${M}_{\mathrm{D}}$ and ${M}_{\mathrm{R}}$. We show that three light Majorana neutrinos (i.e., the mass eigenstates of ${\ensuremath{\nu}}_{e}$, ${\ensuremath{\nu}}_{\ensuremath{\mu}}$, and ${\ensuremath{\nu}}_{\ensuremath{\tau}}$) are exactly massless in this model, if and only if ${M}_{\mathrm{L}}={M}_{\mathrm{D}}{M}_{\mathrm{R}}^{\ensuremath{-}1}{M}_{\mathrm{D}}^{T}$ exactly holds. This no-go theorem implies that small but nonvanishing neutrino masses may result from a significant but incomplete cancellation between ${M}_{\mathrm{L}}$ and ${M}_{\mathrm{D}}{M}_{\mathrm{R}}^{\ensuremath{-}1}{M}_{\mathrm{D}}^{T}$ terms in the Type-II seesaw formula, provided three right-handed Majorana neutrinos are of $\mathcal{O}(1)\text{ }\text{ }\mathrm{TeV}$ and experimentally detectable at the LHC. We propose three simple Type-II seesaw scenarios with the ${A}_{4}\ifmmode\times\else\texttimes\fi{}\mathrm{U}(1{)}_{\mathrm{X}}$ flavor symmetry and its explicit breaking to interpret the observed neutrino mass spectrum and neutrino mixing pattern. Such a TeV-scale neutrino model can be tested in two complementary ways: (1) searching for possible collider signatures of lepton number violation induced by the right-handed Majorana neutrinos and doubly-charged Higgs particles; and (2) searching for possible consequences of unitarity violation of the $3\ifmmode\times\else\texttimes\fi{}3$ neutrino mixing matrix in the future long-baseline neutrino oscillation experiments.
119236167
Correlative signatures of heavy Majorana neutrinos and doubly-charged Higgs bosons at the Large Hadron Collider
Abstract We explore an intriguing possibility to test the type-II seesaw mechanism of neutrino mass generation at the Large Hadron Collider (LHC). We show that the lepton-number-violating signatures of heavy Majorana neutrinos N i (for i = 1 , 2 , 3 ) and doubly-charged Higgs bosons H ± ± can be closely correlated with each other in a class of TeV-scale type-II seesaw models. Taking the minimal version of such models for example, we calculate the cross sections of p p → l α ± l β ± X processes mediated separately by N 1 and H ± ± , and illustrate their nontrivial correlation at the LHC.
6575970
Higgs Vacuum Stability, Neutrino Mass, and Dark Matter
Recent results from ATLAS and CMS point to a narrow range for the Higgs mass: M_H∈(124,126)  GeV. Given this range, a case may be made for new physics beyond the Standard Model (SM) because of the resultant vacuum stability problem, i.e., the SM Higgs quartic coupling may run to negative values at a scale below the Planck scale. We study representative minimal extensions of the SM that can keep the SM Higgs vacuum stable to the Planck scale by introducing new scalar or fermion interactions at the TeV scale while solving other phenomenological problems. In particular, we consider the type-II seesaw model, which is introduced to explain the nonzero Majorana masses of the active neutrinos. Similarly, we observe that if the stability of the SM Higgs vacuum is ensured by the running of the gauge sector couplings, then one may require a series of new electroweak multiplets, the neutral component of which can be a cold dark matter candidate. Stability may also point to a new U(1) gauge symmetry, in which the SM Higgs carries a nonzero charge.
2474648
Neutrino masses and lepton-flavor-violating τ decays in the supersymmetric left-right model
In the supersymmetric left-right model, the light neutrino masses are given by the Type-II seesaw mechanism. A duality property of this mechanism indicates that there exist eight possible Higgs triplet Yukawa couplings which result in the same neutrino mass matrix. In this paper, we work out the one-loop renormalization group equations for the effective neutrino mass matrix in the supersymmetric left-right model. The stability of the Type-II seesaw scenario is briefly discussed. We also study the lepton-flavor-violating processes (tau -> mu gamma and tau -> e gamma) by using the reconstructed Higgs triplet Yukawa couplings.
119308558
Vacuum stability and Higgs diphoton decay rate in the Zee-Babu model
A bstractAlthough recent Higgs data from ATLAS and CMS are compatible with a Standard Model (SM) signal at 2σ level, both experiments see indications for an excess in the diphoton decay channel, which points to new physics beyond the SM. Given such a low Higgs mass mH ~ 125 GeV, another sign indicating the existence of new physics beyond the SM is the vacuum stability problem, i.e., the SM Higgs quartic coupling may run to negative values at a scale below the Planck scale. In this paper, we study the vacuum stability and enhanced Higgs diphoton decay rate in the Zee-Babu model, which was used to generate tiny Majorana neutrino masses at two-loop level. We find that it is rather difficult to find overlapping regions allowed by the vacuum stability and diphoton enhancement constraints. As a consequence, it is almost inevitable to introduce new ingredients into the model, in order to resolve these two issues simultaneously.
124347725
THE RELATION BETWEEN K+/PI+ RATIO AND SECONDARY COLLISIONS IN ULTRA-RELATIVISTIC HEAVY-ION COLLISIONS
Based on the concept of the formation time, the contribution of secondary collisions to the change of the K+/π+ ratio in ultra-relativistic heavy ion collisions is calculated. The result shows that the effect of secondary collisions in the target nucleus is not enough to explain the observed change of the K+/π+ ratio.
120282413
Black-hole formation in the new inflationary universe
In the new inflationary universe the fluctuation of the Higgs scalar field in the supercooled expansion stage is the origin of the irregularities observed today. It is supposed that a sufficiently large fluctuation must have caused gravitational collapse. We present a numerical model for black-hole formation in the new inflationary universe.
14601338
The mesonic fluctuations and corrections in the chiral symmetry breaking vacuum
Abstract The mesonic quantum fluctuations and their corrections on the chiral condensate and pion polarization function are investigated in the self-consistent scheme of SU(2) Nambu–Jona-Lasinio model by exactly calculating the next-to-leading order (NLO) Feynman diagrams in 1/ N c expansion. While the fluctuations and corrections depend strongly on the meson's three-momentum cut-off Λ M , no chiral symmetry restoration is found since the cancellation between the NLO and the one-quark-loop diagram with quark mass deviated from the mean-field value.
124770922
DCC Size Effects on Pion Spectrum Distribution
The effects of two kinds of coherent lengths, the wave packet length of the emitter and the radius of the coherent source, on pion spectrum distribution are studied. It is shown that both coherent lengths can cause abundant pions at low momentum. Observing abundant pions at low momentum may be taken as a signal of DCC effects.
6699997
THERMAL RELAXATION TIME IN CHEMICALLY NON-EQUILIBRATED QUARK-GLUON PLASMA
The definition of thermal relaxation time is extended to chemically non-equilibrated quark-gluon plasma and the chemical non-equilibrated thermal relaxation times for partons are calculated using the non-equilibrium Debye mass as the infrared regulator. The dependence of the thermal relaxation time on the fugacity is given and the influence of the chemical non-equilibration is discussed. We find that there are threshold fugacities lambda(g)* and lambda(q)* for gluons and quarks. for lambda(g) lambda(g)*(lambda(q) > lambda(q)*), ratios are almost 1. It is shown that there is also the two-stage equilibration in a chemically non-equilibrated plasma. We also discussed the effect of using the non-equilibrium Debye mass as the infrared cutoff. (C) 1998 Published by Elsevier Science B.V.