423 research outputs found
Observing Doubly Charged Higgs Bosons in Photon-Photon Collisions
We discuss the possibility of observing doubly charged Higgs bosons in
collisions. We find that one can increase the range of
observability close to the kinematic limit by a judicious choice of the
polarisations of the initial beams as well as the initial laser beam
photons which are made to back-scatter from the former. We also note that, in a
large region of parameter space, the generally used lepton number violating
decay mode is dominated by the decay into a singly charged Higgs and a real or
virtual -boson, giving rise to a large number of fermions in the final
state. This can qualitatively alter the strategy for discovering doubly-charged
scalars.Comment: 10 pages, 2 embedded figure
Unusual Charged Higgs Signals at LEP-2
We have made a detailed study of the signals produced at LEP-2 from charged
scalar bosons whose dominant decay channels are into four fermions. The event
rates as well as kinematics of the final states are discussed when such scalars
are either pair-produced or are generated through a tree-level interaction
involving a charged scalar, the W and the Z. The backgrounds in both cases are
discussed. We also suggest the possibility of reconstructing the mass of such a
scalar at LEP-2.Comment: 12 pages, LateX, 9 Postscript figures, uses eps
Radiative production of invisible charginos in photon photon collision
If in a supersymmetric model, the lightest chargino is nearly degenerate with
the lightest neutralino, the former can decay into the latter alongwith a soft
pion (or a lepton-neutrino pair). Near degeneracy of the chargino and
neutralino masses can cause the other decay products (the pion or the lepton)
to be almost invisible. Photon-photon colliders offer a possibility of clean
detection of such an event through a hard photon tag.Comment: 12 pages, 5 postscript figure
LAR inhibitory peptide promotes recovery of diaphragm function and multiple forms of respiratory neural circuit plasticity after cervical spinal cord injury.
Chondroitin sulfate proteoglycans (CSPGs), up-regulated in and around the lesion after traumatic spinal cord injury (SCI), are key extracellular matrix inhibitory molecules that limit axon growth and consequent recovery of function. CSPG-mediated inhibition occurs via interactions with axonal receptors, including leukocyte common antigen- related (LAR) phosphatase. We tested the effects of a novel LAR inhibitory peptide in rats after hemisection at cervical level 2, a SCI model in which bulbospinal inspiratory neural circuitry originating in the medullary rostral ventral respiratory group (rVRG) becomes disconnected from phrenic motor neuron (PhMN) targets in cervical spinal cord, resulting in persistent partial-to-complete diaphragm paralysis. LAR peptide was delivered by a soaked gelfoam, which was placed directly over the injury site immediately after C2 hemisection and replaced at 1 week post-injury. Axotomized rVRG axons originating in ipsilateral medulla or spared rVRG fibers originating in contralateral medulla were separately assessed by anterograde tracing via AAV2-mCherry injection into rVRG. At 8 weeks post-hemisection, LAR peptide significantly improved ipsilateral hemidiaphragm function, as assessed in vivo with electromyography recordings. LAR peptide promoted robust regeneration of ipsilateral-originating rVRG axons into and through the lesion site and into intact caudal spinal cord to reach PhMNs located at C3-C5 levels. Furthermore, regenerating rVRG axons re-established putative monosynaptic connections with their PhMNs targets. In addition, LAR peptide stimulated robust sprouting of both modulatory serotonergic axons and contralateral-originating rVRG fibers within the PhMN pool ipsilateral/caudal to the hemisection. Our study demonstrates that targeting LAR-based axon growth inhibition promotes multiple forms of respiratory neural circuit plasticity and provides a new peptide-based therapeutic strategy to ameliorate the devastating respiratory consequences of SCI
Are Messages of R-parity Violating Supersymmetry Hidden within Top Quark Signals ?
In an R-parity nonconserving supersymmetric theory, the lighter stop can
dominantly decay into and if R-parity breaking has to explain
the neutrino mass and mixing pattern suggested by the data on atmospheric muon
neutrinos. This should give rise to and ,
signals resembling those of the top quark at the Fermilab Tevatron. One can
thus constrain the stop parameter space using the current top search data, and
similarly look for the first signals of supersymmetry at the upgraded runs of
the Tevatron.Comment: 13 pages, RevTeX, 2 PS figures, uses epsfig.sty, few comments and
references added, version to appear in Phys. Rev. Let
Summary of the Activities of the Working Group I on High Energy and Collider Physics
This is a summary of the projects undertaken by the Working Group I on High
Energy Collider Physics at the Eighth Workshop on High Energy Physics
Phenomenology (WHEPP8) held at the Indian Institute of Technology, Mumbai,
January 5-16, 2004. The topics covered are (i) Higgs searches (ii)
supersymmetry searches (iii) extra dimensions and (iv) linear collider.Comment: summary of Working Group I at the Eighth Workshop on High Energy
Physics Phenomenology (WHEPP8), I.I.T., Mumbai, January 5-16, 200
Radiative contribution to neutrino masses and mixing in SSM
In an extension of the minimal supersymmetric standard model (popularly known
as the SSM), three right handed neutrino superfields are introduced to
solve the -problem and to accommodate the non-vanishing neutrino masses
and mixing. Neutrino masses at the tree level are generated through parity
violation and seesaw mechanism. We have analyzed the full effect of one-loop
contributions to the neutrino mass matrix. We show that the current three
flavour global neutrino data can be accommodated in the SSM, for both
the tree level and one-loop corrected analyses. We find that it is relatively
easier to accommodate the normal hierarchical mass pattern compared to the
inverted hierarchical or quasi-degenerate case, when one-loop corrections are
included.Comment: 51 pages, 14 figures (58 .eps files), expanded introduction, other
minor changes, references adde
Discrimination of low missing energy look-alikes at the LHC
The problem of discriminating possible scenarios of TeV scale new physics
with large missing energy signature at the Large Hadron Collider (LHC) has
received some attention in the recent past. We consider the complementary, and
yet unexplored, case of theories predicting much softer missing energy spectra.
As there is enough scope for such models to fake each other by having similar
final states at the LHC, we have outlined a systematic method based on a
combination of different kinematic features which can be used to distinguish
among different possibilities. These features often trace back to the
underlying mass spectrum and the spins of the new particles present in these
models. As examples of "low missing energy look-alikes", we consider
Supersymmetry with R-parity violation, Universal Extra Dimensions with both
KK-parity conserved and KK-parity violated and the Littlest Higgs model with
T-parity violated by the Wess-Zumino-Witten anomaly term. Through detailed
Monte Carlo analysis of the four and higher lepton final states predicted by
these models, we show that the models in their minimal forms may be
distinguished at the LHC, while non-minimal variations can always leave scope
for further confusion. We find that, for strongly interacting new particle
mass-scale ~600 GeV (1 TeV), the simplest versions of the different theories
can be discriminated at the LHC running at sqrt{s}=14 TeV within an integrated
luminosity of 5 (30) fb^{-1}.Comment: 40 pages, 10 figures; v2: Further discussions, analysis and one
figure added, ordering of certain sections changed, minor modifications in
the abstract, version as published in JHE
Phenomenology of Light Sneutrino Dark Matter in cMSSM/mSUGRA with Inverse Seesaw
We study the possibility of a light Dark Matter (DM) within a constrained
Minimal Supersymmetric Standard Model (cMSSM) framework augmented by a SM
singlet-pair sector to account for the non-zero neutrino masses by inverse
seesaw mechanism. Working within a 'hybrid' scenario with the MSSM sector fixed
at high scale and the singlet neutrino sector at low scale, we find that,
contrary to the case of the usual cMSSM where the neutralino DM cannot be very
light, we can have a light sneutrino DM with mass below 100 GeV satisfying all
the current experimental constraints from cosmology, collider as well as
low-energy experiments. We also note that the supersymmetric inverse seesaw
mechanism with sneutrino as the lightest supersymmetric partner can have
enhanced same-sign dilepton final states with large missing transverse energy
(mET) coming from the gluino- and squark-pair as well as the squark-gluino
associated productions and their cascade decay through charginos. We present a
collider study for the same-sign dilepton+jets+mET signal in this scenario and
propose some distinctions with the usual cMSSM. We also comment on the
implications of such a light DM scenario on the invisible decay width of an 125
GeV Higgs boson.Comment: 24 pages, 4 figures, 7 tables; matches published versio
Combination of a Gellan Gum-Based Hydrogel With Cell Therapy for the Treatment of Cervical Spinal Cord Injury
Cervical spinal cord trauma represents more than half of the spinal cord injury (SCI) cases worldwide. Respiratory compromise, as well as severe limb motor deficits, are among the main consequences of cervical lesions. In the present work, a Gellan Gum (GG)-based hydrogel modified with GRGDS peptide, together with adipose tissue-derived stem/stromal cells (ASCs) and olfactory ensheathing cells (OECs), was used as a therapeutic strategy after a C2 hemisection SCI in rats. Hydrogel or cells alone, and a group without treatment, were also tested. Four weeks after injury, compound muscle action potentials (CMAPs) were performed to assess functional phrenic motor neuron (PhMN) innervation of the diaphragm; no differences were observed amongst groups, confirming that the PhMN pool located between C3 and C5 was not affected by the C2 injury or by the treatments. In the same line, the vast majority of diaphragmatic neuromuscular junctions remained intact. Five weeks post-injury, inspiratory bursting of the affected ipsilateral hemidiaphragm was evaluated through EMG recordings of dorsal, medial and ventral subregions of the muscle. All treatments significantly increased EMG amplitude at the ventral portion in comparison to untreated animals, but only the combinatorial group presented increased EMG amplitude at the medial portion of the hemidiaphragm. No differences were observed in forelimb motor function, neither in markers for axonal regrowth (neuronal tracers), astrogliosis (GFAP) and inflammatory cells (CD68). Moreover, using Von Frey testing of mechanical allodynia, it was possible to find a significant effect of the group combining hydrogel and cells on hypersensitivity; rats with a SCI displayed an increased response of the contralateral forelimb to a normally innocuous mechanical stimulus, but after treatment with the combinatorial therapy this behavior was reverted almost to the levels of uninjured controls. These results suggest that our therapeutic approach may have beneficial effects on both diaphragmatic recovery and sensory function
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