A note on gauge-fixing in the electroweak sector of nmUED

Electroweak observables are highly sensitive to the loop corrections. Therefore, a proper gauge-fixing mechanism is always needed to define the propagators which are involved in Feynman loop amplitude. With this spirit we compute gauge-fixing mechanism in five dimensional (5-D) Universal Extra-Dimensional (UED) model with boundary localised terms (BLTs). These BLTs are not 5-D operators in four-dimensional (4-D) effective theory but some sort of boundary conditions on the respective fields at the fixed points of $S^1/Z_2$ orbifold. Furthermore, these BLTs non-trivially modify the Kaluza-Klein (KK) spectra and some of the interactions among the KK-excitations compared to the minimal UED (mUED), in which, these BLTs are absent. In this note we calculate the gauge-fixing mechanism in the electroweak sector of such non-trivial UED scenario. Moreover, we discuss the composition and masses of Goldstone and any physical scalar that emerge after the symmetry breaking in this set up with different choices of gauge.Comment: 9 pages, title has been changed, matched with the published versio

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.

LHC Signature of the Minimal SUGRA Model with a Large Soft Scalar Mass

Thanks to the focus point phenomenon, it is quite {\it natural} for the minimal SUGRA model to have a large soft scalar mass m_0 > 1 TeV. A distinctive feature of this model is an inverted hierarchy, where the lighter stop has a significantly smaller mass than the other squarks and sleptons. Consequently, the gluino is predicted to decay dominantly via stop exchange into a channel containing 2b and 2W along with the LSP. We exploit this feature to construct a robust signature for this model at the LHC in leptonic channels with 3-4 b-tags and a large missing-E_T.Comment: Small clarifications added. Final version to appear in Phys. Lett.

ZZH coupling : A probe to the origin of EWSB ?

We argue that the $ZZH$ coupling constitutes a simple probe of the nature of the scalar sector responsible for electroweak symmetry breaking. We demonstrate the efficacy of this measure through an analysis of four-dimensional models containing scalars in arbitrary representation of $SU(2) \times U(1)$, as well as extra-dimensional models with a non-factorizable geometry. A possible role for the $t \bar t H$ couplings is also discussed.Comment: Minor modifications in the text. Version to appear in Nucl. Phys.

Singlet-Higgs-Boson Signals at Hadron Colliders

Many extensions of the Standard Model include $SU(2)_L \times U(1)_Y$ singlet higgs bosons, $h^0$, and also vectorlike fermions which couple to it. The production and detection possibilities of such singlet neutral scalars at hadron colliders are considered for different scenarios of vectorlike fermions. We find that for some values of masses and couplings, detection at the CERN Large Hadron Collider (LHC) appears to be a distinct possibility, while at the Fermilab Tevatron upgrade the $h^0$ might be observed only in very favourable circumstances.Comment: 35 pages, latex file, figures 2-7 available upon reques