352 research outputs found
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
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.
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
Vacuum Stability Constraints and LHC Searches for a Model with a Universal Extra Dimension
If the new boson is lying in the narrow mass range between 122 - 127 GeV is
confirmed to be a Higgs boson, then stability of the electroweak vacuum in a
minimal model with a universal extra dimension (mUED) will require a much lower
cutoff for the theory than has been envisaged earlier. We show that this low
cutoff would lead to important changes in much of the mUED phenomenology
studied till now. In particular, prospects for LHC searches for n = 1 states
are rather limited, while resonant n = 2 states may go completely undetected.
Prospects for detection at the ILC and CLIC are less affected.Comment: Revised and updated version, some typos fixed and references adde
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 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 , as well
as extra-dimensional models with a non-factorizable geometry. A possible role
for the couplings is also discussed.Comment: Minor modifications in the text. Version to appear in Nucl. Phys.
- …