275 research outputs found
Are light sneutrinos buried in LEP data?
Supersymmetry may resolve the disagreement between the precision electroweak
data and the direct limit on the higgs mass, if there are light sneutrinos in
the mass range 55 GeV < m_{\snu} < 80 GeV. Such sneutrinos should decay
invisibly with 100% branching ratio and contribute to the + missing
energy signal, investigated by all the LEP groups. It is shown that while the
data accumulated by a single group may not be adequate to reveal such
sneutrinos, a combined analysis of the data collected by all four groups will
be sensitive to m_{\snu} in the above range. If no signal is found a lower
bound on m_{\snu} stronger than that obtained from the -pole data may
emerge.Comment: 12 pages, LaTeX, 1 postscript figure included, uses epsfig.sty Minor
revisions in the discussion of future prospects, 1 ref adde
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
Associated Higgs Production in CP-violating supersymmetry: probing the `open hole' at the Large Hadron Collider
A benchmark CP-violating supersymmetric scenario (known in the literature as
`CPX-scenario') is studied in the context of the Large Hadron Collider (LHC).
It is shown that the LHC, with low to moderate accumulated luminosity, will be
able to probe the existing `hole' in the - plane, which
cannot be ruled out by the Large Electron Positron Collider data. This can be
done through associated production of Higgs bosons with top quark and top
squark pairs leading to the signal \emph{dilepton + jets (including 3
b-jets) + missing }. Efficient discrimination of such a CP-violating
supersymmetric scenario from other contending ones is also possible at the LHC
with a moderate volume of data.Comment: LaTeX, 19 pages, 5 figures, added references for section 2, typos
correcte
Lepton Flavours at the Early LHC Experiments as the Footprints of the Dark Matter Producing Mechanisms
The mSUGRA parameter space corresponding to light sleptons well within the
reach of LHC and relatively light squarks and gluinos (mass 1 TeV) has
three regions consistent with the WMAP data on dark matter relic density and
direct mass bounds from LEP 2. Each region can lead to distinct leptonic
signatures from squark-gluino events during the early LHC experiments
(integrated luminosity or even smaller). In the much studied
stau-LSP coannihilation region with a vanishing common trilinear coupling
() at the GUT scale a large fraction of the final states contain electrons
and / or muons and - - universality holds to a good
approximation. In the not so well studied scenarios with non-vanishing
both LSP pair annihilation and stau-LSP coannihilation could contribute
significantly to the dark matter relic density for even smaller squark-gluino
masses. Our simulations indicate that the corresponding signatures are final
states rich in -leptons while final states with electrons and muons are
suppressed leading to a violation of lepton universality. These features may be
observed to a lesser extent even in the modified parameter space (with non-zero
) where the coannihilation process dominates. We also show that the
generic -leptons + -jets+ signatures without flavour tagging
can also discriminate among the three scenarios. However, the signals become
more informative if the and -jet tagging facilities at the LHC
experiments are utilized.Comment: 28 page
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.
Effects of SO(10) D-Terms on SUSY Signals at the Tevatron
We study signals for the production of superparticles at the Tevatron in
supergravity scenarios based on the Grand Unified group SO(10). The breaking of
this group introduces extra contributions to the masses of all scalars,
described by a single new parameter. We find that varying this parameter can
considerably change the size of various expected signals studied in the
literature, with different numbers of jets and/or charged leptons in the final
state. The ratios of these signal can thus serve as a diagnostic to detect or
constrain deviations from the much--studied scenario where all scalar masses
are universal at the GUT scale. Moreover, under favorable circumstances some of
these signals, and/or new signals involving hard jets, should be observable
at the next run of the Tevatron collider even if the average scalar mass lies
well above the gluino mass.Comment: 17 pages, LaTeX including 3 postscript figures, uses equation.st
New Limits on Heavier Electroweakinos and their LHC Signatures
We investigate the heavier electroweakino sectors in several versions of the
MSSM, which has not been explored so far in the light of the LHC data, and
obtain new bounds using the ATLAS Run I constraints in the channel. We also venture beyond the trilepton events and
predict several novel multilepton + signatures of these
electroweakinos which may show up before the next shutdown of the LHC.Comment: 12 pages;3 tables and some texts are added;numerical results remain
unchange
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