Mass bounds for Triplet Scalars of the Left-Right symmetric model and their future detection prospects

The standard formulation of the Left-Right symmetric model involves scalars transforming as a triplet under SU(2)L. This multiplet contains particles which are uncharged, singly-charged, and doubly-charged. We derive a bound on the uncharged scalar mass of 55.4 GeV using results from LEP-II and find that a range upto 110 GeV may be explored at the NLC at the 5sigma level. We also discuss search strategies for the singly- and doubly-charged scalars at the Tevatron and the LHC. Possible Standard Model backgrounds for the relevant modes are estimated and compared with the signal. At the LHC, the prospects of detecting the doubly-charged scalar are bright up to a mass of 850 GeV while the 5sigma discovery limit of the singly-charged mode extends to 240 GeV for an integrated luminosity of 100 inverse fb. At the Tevatron, with an integrated luminosity of 25 inverse fb, the doubly-charged state can be detected if its mass is less than 275 GeV while the reach for the singly charged scalar is 140 GeV.Comment: Latex, References added, some postscript figures modified, to appear in Phys. Rev.

A note on the neutrino mass implications of the K2K experiment

The K2K experiment has presented the first results on the observation of nu_mu. They show a depletion compared to the expectations and are consistent with neutrino oscillations with a mass-splitting in the range favoured by the Super-Kamiokande atmospheric neutrino measurements. Here we examine the extent by which the range of Delta m^2 obtained from the K2K measurements can vary due to the uncertainties in the flux, cross-section, and detector efficiency.Comment: 8 pages LaTeX, 2 postscript figures, J. Phys. G. (to appear

Kinetic mixing and symmetry breaking dependent interactions of the dark photon

We examine spontaneous symmetry breaking of a renormalisable U(1) x U(1) gauge theory coupled to fermions when kinetic mixing is present. We do not assume that the kinetic mixing parameter is small. A rotation plus scaling is used to remove the mixing and put the gauge kinetic terms in the canonical form. Fermion currents are also rotated in a non-orthogonal way by this basis transformation. Through suitable redefinitions the interaction is cast into a diagonal form. This framework, where mixing is absent, is used for subsequent analysis. The symmetry breaking determines the fermionic current which couples to the massless gauge boson. The strength of this coupling as well as the couplings of the massive gauge boson are extracted. This formulation is used to consider a gauged model for dark matter by identifying the massless gauge boson with the photon and the massive state to its dark counterpart. Matching the coupling of the residual symmetry with that of the photon sets a lower bound on the kinetic mixing parameter. We present analytical formulae of the couplings of the dark photon in this model and indicate some physics consequences.Comment: Latex, Nuclear Physics B (to appear

New constraints on R-parity violation from K and B systems

We have derived new upper limits on several products (two at a time) of lepton number violating $\lambda'$-type couplings from the consideration of $\Delta S = 2$ and $\Delta B = 2$ box graphs. Each box contains one scalar lepton and one W-boson or one charged-Higgs-boson as internal lines. Most of these bounds are more stringent than previously obtained. Some of these product couplings drive $K_L$ (and some other $B_d$) decays to two charged leptons at enhanced rates. Some of them can explain the rare $K^+ \to \pi^+ \nu\bar{\nu}$ event recently observed at BNL.Comment: Latex, 6 pages, no figures; revised and published version with minor changes in the Table caption and a few cosmetic changes in the tex

Are the small neutrino oscillation parameters all related?

Neutrino oscillations reveal several small parameters, namely, $\theta_{13}$, the solar mass splitting {\em vis-\`{a}-vis} the atmospheric one, and the deviation of $\theta_{23}$ from maximal mixing. Can these small quantities all be traced to a single source and, if so, how could that be tested? Here a see-saw model for neutrino masses is presented wherein a dominant term generates the atmospheric mass splitting with maximal mixing in this sector, keeping $\theta_{13} = 0$ and zero solar splitting. A Type-I see-saw perturbative contribution results in non-zero values of $\theta_{13}$, $\Delta m^2_{solar}$, $\theta_{12}$, as well as allows $\theta_{23}$ to deviate from $\pi/4$ in consistency with the data while interrelating them all. CP-violation is a natural consequence and is large ($\delta \sim \pi/2, 3\pi/2$) for inverted mass ordering. The model will be tested as precision on the neutrino parameters is sharpened.Comment: v1: 8 pages, 2 Figures, v2: Published version, Journal title different, minor typographical changes, presentation improved, references added and updated. 9 pages, 3 Figures, Fig. 2 split into Fig. 2 and Fig. 3 for clarit

Next to Minimal Higgs : Mass Bounds and Search Prospects

The Standard Model of electroweak interactions has one scalar doublet. The minimal extension of this sector is effected by adding a neutral, singlet scalar field. Depending on whether the singlet field has a non-zero vacuum expectation value, x, or not, the scenario has quite distinctive predictions. In particular, x unequal to 0 produces a mixing between the usual SU(2) doublet and the singlet, giving rise to two physical states and a goldstone boson with non-vanishing coupling to these. Presence of this coupling modifies the 2 jets + missing energy signal of the Bjorken process at LEP. We update the bounds on the Higgs mass using the LEP-1 data. We then explore, using parton-level Monte Carlo event generators, the production of these scalars at the LHC via gluon-gluon fusion and subsequent detection. We compare the signals with the expected backgrounds.Comment: 16 pages and 7 Postscript figures, Late