14087471
Generalized lepton number and dark left-right gauge model
In a left-right gauge model of particle interactions, the left-handed fermion doublet $(\ensuremath{\nu},e{)}_{L}$ is connected to its right-handed counterpart $(n,e{)}_{R}$ through a scalar bidoublet so that ${e}_{L}$ pairs with ${e}_{R}$, and ${\ensuremath{\nu}}_{L}$ with ${n}_{R}$ to form mass terms. Suppose the latter link is severed without affecting the former, then ${n}_{R}$ is not the mass partner of ${\ensuremath{\nu}}_{L}$, and as we show in this paper, becomes a candidate for dark matter which is relevant for the recent PAMELA and ATIC observations. We accomplish this in a specific nonsupersymmetric model, where a generalized lepton number can be defined, so that ${n}_{R}$ and ${W}_{R}^{\ifmmode\pm\else\textpm\fi{}}$ are odd under $R\ensuremath{\equiv}(\ensuremath{-}1{)}^{3B+L+2j}$. Fermionic leptoquarks are also predicted.
119207256
Dileptons and four leptons at Z′ resonance in the early stage of the LHC
Abstract The LHC era just began. The first discovery at the LHC experiment would be arguably a new resonance pole at TeV scale, if it exists. While the discovery of the Z ′ would be exciting by itself, it may also suggest what other new physics signals should be looked for while the LHC experiment is still at its early stage. We argue that the four lepton resonance at the Z ′ pole is a well-motivated and promising signal especially in supersymmetry framework, which can serve as a supersymmetry search scheme even in the early stage of the LHC experiment.
118173341
Lightest U‐parity Particle (LUP): a hidden sector dark matter candidate
We introduce a new dark matter candidate, the lightest U‐parity particle (LUP). We suggest it as a good dark matter candidate especially in the R‐parity violating supersymmetric model.
119542847
Revival of the Thermal Sneutrino Dark Matter
Studies of the rotation curves of galaxies, large scale structures, and recent measurements of the cosmic microwave background radiation, have confirmed that about 23% of the energy in the Universe is in the form of cold dark matter (CDM) [1]. The origin and the nature of CDM is one of the biggest puzzles in both particle physics and cosmology. Since all known particles are ruled out as dark matter candidates, dark matter provides the strongest phenomenological motivation for new physics beyond the Standard Model (SM). The Minimal Supersymmetric Standard Model (MSSM), supplemented with an exact discrete symmetry (R-parity), possesses two natural CDM candidates: the lightest neutralino and the lightest scalar neutrino (sneutrino). The former is a generic mixture of the superpartners of the neutral gauge and Higgs bosons, and its phenomenology has been the subject of extensive studies over the last 20 years [2]. In contrast, the left-handed (LH) sneutrinos of the MSSM have been ruled out as a major component of the dark matter in the Universe, by the combination of cosmological and experimental constraints. More precisely, LH sneutrinos are weakly charged, and typically annihilate too rapidly via Z-mediated s-channel diagrams, resulting in a relic density too small to account for all of the dark matter. To suppress the annihilation rate it was proposed that the sneutrinos should be either very light (O(GeV)) [3] or very heavy (O(TeV)) [4]. However, a very light sneutrino is excluded by the measurement of the invisible width of the Z gauge boson, while a very heavy sneutrino is excluded by direct dark matter searches [4]. Therefore, the LH sneutrinos of the MSSM are now disfavored as dark matter candidates. On the other hand, the recent evidence of neutrino masses provides strong impetus for extending the particle content of the MSSM with right-handed (RH) neutri� ∗
118589345
Phenomenology of the U(1)'-extended minimal supersymmetric standard model
118614634
Dark side of Higgs diphoton decays and muon g − 2
We propose that the LHC hints for a Higgs diphoton excess and the muon g-2 (g_mu-2) discrepancy between theory and experiment may be related by vector-like "leptons" charged under both U(1)_Y hypercharge and a "dark" U(1)_d. Quantum loops of such leptons can enhance the Higgs diphoton rate and also generically lead to U(1)_Y - U(1)_d kinetic mixing. The induced coupling of a light U(1)_d gauge boson Z_d to electric charge can naturally explain the measured g_mu-2. We update Z_d mass and coupling constraints based on comparison of the electron g-2 experiment and theory, and find that explaining g_mu-2 while satisfying other constraints requires Z_d to have a mass ~ 20-100 MeV. We predict new Higgs decay channels gamma Z_d and Z_d Z_d, with rates below the diphoton mode but potentially observable. The boosted Z_d -> e+e- in these decays would mimic a promptly converted photon and could provide a fraction of the apparent diphoton excess. More statistics or a closer inspection of extant data may reveal such events.
119235859
Inflation and dark matter in two Higgs doublet models
A bstractWe consider the Higgs inflation in the extension of the Standard Model with two Higgs doublets coupled to gravity non-minimally. In the presence of an approximate global U(1) symmetry in the Higgs sector, both radial and angular modes of neutral Higgs bosons drive inflation where large non-Gaussianity is possible from appropriate initial conditions on the angular mode. We also discuss the case with single-field inflation for which the U(1) symmetry is broken to a Z2 subgroup. We show that inflationary constraints, perturbativity and stability conditions restrict the parameter space of the Higgs quartic couplings at low energy in both multi- and single-field cases. Focusing on the inert doublet models where Z2 symmetry remains unbroken at low energy, we show that the extra neutral Higgs boson can be a dark matter candidate consistent with the inflationary constraints. The doublet dark matter is always heavy in multi-field inflation while it can be light due to the suppression of the co-annihilation in single-field inflation. The implication of the extra quartic couplings on the vacuum stability bound is also discussed in the light of the recent LHC limits on the Higgs mass.
119248157
Vector Higgs-portal dark matter and the invisible Higgs
The Higgs sector of the Standard Model offers a unique probe of the hidden sector. In this work, we explore the possibility of renormalizable Higgs couplings to the hidden sector vector fields which can constitute dark matter (DM). Abelian gauge sectors with minimal field content, necessary to render the gauge fields massive, have a natural Z2 parity. This symmetry ensures stability of the vector fields making them viable dark matter candidates, while evading the usual electroweak
118400868
Large non-Gaussianity in non-minimal inflation
We consider a simple inflation model with a complex scalar field coupled to gravity non-minimally. Both the modulus and the angular directions of the complex scalar are slowly rolling, leading to two-field inflation. The modulus direction becomes flat due to the non-minimal coupling, and the angular direction becomes a pseudo-Goldstone boson from a small breaking of the global U(1) symmetry. We show that large non-Gaussianity can be produced during slow-roll inflation under a reasonable assumption on the initial condition of the angular direction. This scenario may be realized in particle physics models such as the Standard Model with two Higgs doublets.
118429155
Chaotic inflation in Jordan frame supergravity
We consider the inflationary scenario with non-minimal coupling in 4D Jordan frame supergravity. We find that there occurs a tachyonic instability along the direction of the accompanying non-inflaton field in generic Jordan frame supergravity models. We propose a higher order correction to the Jordan frame function for solving the tachyonic mass problem and show that the necessary correction can be naturally generated by the heavy thresholds without spoiling the slow-roll conditions. We discuss the implication of the result on the Higgs inflation in NMSSM.
1203139
Gauge coupling unification in a 6D SO(10) orbifold GUT
Abstract We consider the gauge coupling running in a six-dimensional SO ( 10 ) orbifold GUT model. The bulk gauge symmetry is broken down to the standard model gauge group with an extra U ( 1 ) X by orbifold boundary conditions and the extra U ( 1 ) X is further broken through the U ( 1 ) B – L breaking with bulk hyper multiplets. We obtain the corrections of Kaluza–Klein massive modes to the running of the gauge couplings and discuss their implication to the successful gauge coupling unification.