On neutrinoless double beta decay in the minimal left–right symmetric model

We analyze the general phenomenology of neutrinoless double beta decay in the minimal left–right symmetric model. We study under which conditions a New Physics dominated neutrinoless double beta decay signal can be expected in the future experiments. We show that the correlation among the different contributions to the process, which arises from the neutrino mass generation mechanism, can play a crucial role. We have found that, if no fine tuned cancelation is involved in the light–active neutrino contribution, a New Physics signal can be expected mainly from the $W_R$ – $W_R$ channel. An interesting exception is the $W_L$ – $W_R$ channel which can give a dominant contribution to the process if the right-handed neutrino spectrum is hierarchical with $M_1\lesssim $  MeV and $M_2,M_3\gtrsim $  GeV. We also discuss if a New Physics signal in neutrinoless double beta decay experiments is compatible with the existence of a successful Dark Matter candidate in the left–right symmetric models. It turns out that, although it is not a generic feature of the theory, it is still possible to accommodate such a signal with a KeV sterile neutrino as dark matter.     

Pair production of neutral Higgs bosons from the left-right twin Higgs model via γγ collisions

The left-right twin Higgs (LRTH) model predicts the existence of the neutral Higgs bosons (h, Φ⁰), which can be produced in pairs (Φ⁰Φ⁰, hh, Φ⁰h) via γγ collisions at the next generation e⁺e^- International Linear Collider (ILC). Our numerical results show that the production cross section of the neutral Higgs boson pair Φ⁰Φ⁰ can reach 8.8 fb. The subprocess γγ→Φ⁰Φ⁰ might be used to test the LRTH model in future ILC experiments.     

Pair production of neutral Higgs bosons from the left-right twin Higgs model via γγ collisions

The left-right twin Higgs (LRTH) model predicts the existence of the neutral Higgs bosons (h, φ<'0>), which can be produced in pairs (φ<'0>φ<'0>, hh, φ<'0>h) via γγ collisions at the next generation e<'+>e<'-> International Linear Collider (ILC). Our numerical results show that the production cross section of the neutral Higgs boson pair φ<'0>φ<'0> can reach 8.8 fb. The subprocess γγ→φ<'0>φ<'0> might be used to test the LRTH model in future ILC experiments.     

Vortex condensation in the dual Chern–Simons–Higgs model

The contribution of nontrivial vacuum (topological) excitations, more specifically vortex configurations of the self-dual Chern–Simons–Higgs model, to the functional partition function is considered. By using a duality transformation, we arrive at a representation of the partition function in terms of which explicit vortex degrees of freedom are coupled to a dual gauge field. By matching the obtained action to a field theory for the vortices, the physical properties of the model in the presence of vortex excitations are then studied. In terms of this field theory for vortices in the self-dual Chern–Simons–Higgs model, we determine the location of the critical value for the Chern–Simons parameter below which vortex condensation can happen in the system. The effects of self-energy quantum corrections to the vortex field are also considered.     

Lepton-number-violating decays of singly-charged Higgs bosons in the type-(Ⅰ+Ⅱ) seesaw model

The lepton-number-violating decays of singly-charged Higgs bosons H± are investigated in the minimal type-(Ⅰ+Ⅱ) seesaw model with one SU(2)L Higgs triplet Δ and one heavy Majorana neutrino N1 at the TeV scale.We find that the branching ratios B(H+ → lα+ ν)(for α = e,μ,τ) depend not only on the mass and mixing parameters of three light neutrinos νi(for i=1,2,3) but also on those of N1.Assuming that the mass of N1 lies in the range of 200 GeV to 1 TeV,we figure out the generous interference bands for the contributions of νi and N1 to B(H+ →lα+ ν).We illustrate some salient features of such interference effects by considering three typical mass patterns of νi,and show that the relevant Majorana CP-violating phases can affect the magnitudes of B(H+ →l+αν) in this parameter region.     

Lepton-number-violating decays of singly-charged Higgs bosons in the type-（Ⅰ＋Ⅱ ） seesaw model

The lepton-number-violating decays of singly-charged Higgs bosons H^± are investigated in the minimal type-（ Ⅰ＋Ⅱ ） seesaw model with one SU（2）L Higgs triplet △ and one heavy Majorana neutrino N1 at the TeV scale. We find that the branching ratios B（H^＋ → 1α^＋υ^-） （for α = e,μ,τ） depend not only on the mass and mixing parameters of three light neutrinos υi （for i = 1, 2, 3） but also on those of N1. Assuming that the mass of N1 lies in the range of 200 GeV to 1 TeV, we figure out the generous interference bands for the contributions of υi and N1 to B（H^＋→ 1α^＋υ^-）. We illustrate some salient features of such interference effects by considering three typical mass patterns of υi, and show that the relevant Majorana CP-violating phases can affect the magnitudes of B（H^＋→ 1α^＋υ^-）） in this parameter region.     

Neutrino mixing and masses in a left–right model with mirror fermions

In the framework of a left–right model containing mirror fermions with gauge group SU(3) _C ⊗SU(2) _L ⊗SU(2) _R ⊗U(1) _Y′, we estimate the neutrino masses, which are found to be consistent with their experimental bounds and hierarchy. We evaluate the decay rates of the Lepton Flavor Violation (LFV) processes μ→eγ, τ→μγ and τ→eγ. We obtain upper limits for the flavor-changing branching ratios in agreement with their present experimental bounds. We also estimate the decay rates of heavy Majorana neutrinos in the channels N→W ^± l ^∓, N→Zν _l and N→Hν _l , which are roughly equal for large values of the heavy neutrino mass. Starting from the most general Majorana neutrino mass matrix, the smallness of active neutrino masses turns out from the interplay of the hierarchy of the involved scales and the double application of seesaw mechanism. An appropriate parameterization on the structure of the neutrino mass matrix imposing a symmetric mixing of electron neutrino with muon and tau neutrinos leads to tri-bimaximal mixing matrix for light neutrinos.     

Minimal supersymmetric left–right model with automatic R-parity

We revisit the minimal supersymmetric left–right model with B−L=2$B-L=2$ triplet Higgs fields and show that a self-consistent picture emerges with automatic R-parity conservation even in the absence of higher-dimensional operators. By computing the effective potential for the Higgs system including heavy Majorana neutrino Yukawa couplings we show that the global minimum of the model can lie in the charge and R-parity conserving domain. The model provides natural solutions to the SUSY phase problem and the strong CP problem and makes several interesting predictions. Quark mixing angles arise only after radiative corrections from the lepton sector are taken into account. A pair of doubly charged Higgs fields remain light below TeV with one field acquiring its mass entirely via renormalization group corrections. We find this mass to be not much above the Bino mass. In the supergravity framework for SUSY breaking, we also find similar upper limits on the stau masses. Natural solutions to the μ   problem and the SUSY CP problem entails light SUL₍₂₎$\mathit{SU}{(2)}_L$ triplet Higgs fields, leading to rich collider phenomenology.     

Spin vortices in the Abelian–Higgs model with cholesteric vacuum structure

We continue the study of U(1)$U\left(1\right)$ vortices with cholesteric vacuum structure. A new class of solutions is found which represent global vortices of the internal spin field. These spin vortices are characterized by a non-vanishing angular dependence at spatial infinity, or winding. We show that despite the topological Z₂${\mathbb{Z}}_2$ behavior of SO(3)$SO\left(3\right)$ windings, the topological charge of the spin vortices is of the Z$\mathbb{Z}$ type in the cholesteric. We find these solutions numerically and discuss the properties derived from their low energy effective field theory in 1+1$1+1$ dimensions.     

Signatures of MSSM charged Higgs bosons via chargino–neutralino decay channels at the LHC

We assess the potential of detecting a charged Higgs boson of the MSSM at the LHC via its decays into a chargino and a neutralino. We focus our attention on the region of parameter space with and , where identification of the via other decay modes has proven to be ineffective. Searching for means to plug this hole, we simulate the decays and – the former can yield a single hard lepton (from the chargino decay) while the latter can yield three leptons (from the chargino and neutralino decays). Coupled with the dominant top quark + charged Higgs boson production mode, the resulting signature is one or three hard, isolated leptons, substantial missing transverse momentum and a reconstructed (via a 3-jet invariant mass) top quark. The single lepton channel is swamped by background processes; however, with suitable cuts, a trilepton signal emerges. While such a signal suffers from a low number of surviving events (after cuts) and is dependent on several MSSM input parameters (notably , and slepton masses), it does fill at least some of the void left by previous investigations. Received: 21 October 2000 / Published online: 23 February 2001     

Precise correction to parameter ρ in the littlest Higgs model

In this paper tree-level violation of weak isospin parameter, ρ in the frame of the littlest Higgs model is studied. The potentially large deviation from the standard model prediction for the ρ in terms of the littlest Higgs model parameters is calculated. The maximum value for ρ for f=1TeV, c=0.05,c′= 0.05 and υ′= 1.5GeV is ρ=1.2973 which means a large enhancement than the SM.     

Tricritical point in quantum phase transitions of the Coleman–Weinberg model at Higgs mass

The tricritical point, which separates first and second order phase transitions in three-dimensional superconductors, is studied in the four-dimensional Coleman–Weinberg model, and the similarities as well as the differences with respect to the three-dimensional result are exhibited. The position of the tricritical point in the Coleman–Weinberg model is derived and found to be in agreement with the Thomas–Fermi approximation in the three-dimensional Ginzburg–Landau theory. From this we deduce a special role of the tricritical point for the Standard Model Higgs sector in the scope of the latest experimental results, which suggests the unexpected relevance of tricritical behavior in the electroweak interactions.     

Z′ bosons, the NuTeV anomaly, and the Higgs boson mass

Fits to the precision electroweak data that include the NuTeV measurement are considered in family universal, anomaly free U(1) extensions of the Standard Model. In data sets from which the hadronic asymmetries are excluded, some of the Z′ models can double the predicted value of the Higgs boson mass, from ～60 to ～120 GeV, removing the tension with the LEP II lower bound, while also modestly improving the χ ² confidence level. The effect of the Z′ models on both m _H and the χ ² confidence level is increased when the NuTeV measurement is included in the fit. Both the original NuTeV data and a revised estimate by the PDG are considered.     

Direct CP violation in charm decays due to left–right mixing

Motivated by the 3.8σ   deviation from no CP violation hypothesis for the CP asymmetry (CPA) difference between D⁰→K⁺K⁻$D^0\to K^{+}{K}^{-}$ and D⁰→π⁺π⁻$D^0\to {\pi }^{+}{\pi }^{-}$, reported recently by LHCb and CDF, we investigate the CP violating effect due to the left–right (LR) mixing in the general LR symmetric model. In particular, we show that the large CPA difference could be explained in the non-manifest LR model.     

Pseudoscalar Higgs bosons at the LHC: production and decays into electroweak gauge bosons revisited

We analyse and compute, within a number of standard model (SM) extensions, the cross sections σ _A→VV′ for the production of a heavy neutral pseudoscalar Higgs-boson/spin-zero resonance at the LHC and its subsequent decays into electroweak gauge bosons. For comparison we calculate also the corresponding cross sections for a heavy scalar. The SM extensions we consider include a type-II two-Higgs doublet model (2HDM), a 2HDM with four chiral fermion generations, the minimal supersymmetric extension of the SM (MSSM), and top-colour assisted technicolour models. Presently available phenomenological constraints on the parameters of these models are taken into account. We find that, with the exception of the MSSM, these models permit the LHC cross sections σ _A→VV′ to be of observable size. That is, a pseudoscalar resonance may be observable, if it exists, at the LHC in its decays into electroweak gauge bosons, in particular in WW and γ γ final states.