1,838 research outputs found
Brane Localized Curvature for Warped Gravitons
We study the effects of including brane localized curvature terms in the
Randall-Sundrum (RS) model of the hierarchy. This leads to the existence of
brane localized kinetic terms for the graviton. Such terms can be induced by
brane and bulk quantum effects as well as Higgs-curvature mixing on the brane.
We derive the modified spectrum of Kaluza-Klein (KK) gravitons and their
couplings to 4-dimensional fields in the presence of these terms. We find that
the masses and couplings of the KK gravitons have considerable dependence on
the size of the brane localized terms; the weak-scale phenomenology of the
model is consequently modified . In particular, the weak-scale spin-2 graviton
resonances which generically appear in the RS model may be significantly
lighter than previously assumed. However, they may avoid detection as their
widths may be too narrow to be observable at colliders. In the contact
interaction limit, for a certain range of parameters, the experimental reach
for the scale of the theory is independent of the size of the boundary terms.Comment: 20 pages, 11 figures, LaTex, minor revision
Indirect Collider Signals for Extra Dimensions
A recent suggestion that quantum gravity may become strong near the weak
scale has several testable consequences. In addition to probing for the new
large (submillimeter) extra dimensions associated with these theories via
gravitational experiments, one could search for the Kaluza Klein towers of
massive gravitons which are predicted in these models and which can interact
with the fields of the Standard Model. Here we examine the indirect effects of
these massive gravitons being exchanged in fermion pair production in \epem
annihilation and Drell-Yan production at hadron colliders. In the latter case,
we examine a novel feature of this theory, which is the contribution of gluon
gluon initiated processes to lepton pair production. We find that these
processes provide strong bounds, up to several TeV, on the string scale which
are essentially independent of the number of extra dimensions. In addition, we
analyze the angular distributions for fermion pair production with spin-2
graviton exchanges and demonstrate that they provide a smoking gun signal for
low-scale quantum gravity which cannot be mimicked by other new physics
scenarios.Comment: Corrected typos, added table and reference
Using to Probe Top Quark Couplings
Possible anomalous couplings of the top-quark to on-shell photons and gluons
are constrained by the recent results of the CLEO Collaboration on both
inclusive and exclusive radiative decays. We find that the process \bsg\
can lead to reasonable bounds on both the anomalous electric and magnetic
dipole moments of the top-quark, while essentially no limits are obtained on
the corresponding chromoelectric and chromomagnetic moments, which enter the
expression for the decay rate only through operator mixing.Comment: 10 pages plus 6 figures (available by request), LaTex,
ANL-HEP-PR-93-3
Leptoquark pair production at the Fermilab Tevatron: Signal and backgrounds
We perform a Monte-Carlo simulation of scalar leptoquark pair production at
the Tevatron (energy =1.8 TeV and luminosity =100 pb^{-1}) with ISAJET. We also
investigate the dominant sources of Standard Model background: Z*jj, ZZ
production and heavy quark top-antitop. We find that the top-antitop background
is the most important except near the Z pole where the Z*jj background is
peaked. We also evaluate the signal-to-background ratio and find a discovery
reach of 130 GeV (170 GeV) for a branching ratio of B(LQ-> eq)=0.5 (B=1).Comment: 8 pages, 6 figures, latex (revtex
Recommended from our members
Nonadiabatic scattering and transport at the spindle cusp
When magnetohydrodynamics is used to describe plasma flow across a separatrix to open field lines, the transport is modeled by a diffusion equation with a sink for particles on the open lines. In that case, it is assumed that plasma is carried to and from the separatrix by diffusive processes. The purpose of this note is to discuss the nonadiabatic processes occurring at a spindle cusp to transfer plasma across a separatrix. After an ion is delivered to the vicinity of the separatrix by diffusion it enters the spindle cusp and will skip back and forth across the separatrix, producing a structured transport not seen with MHD
Leptoquark production in ultrahigh-energy neutrino interactions revisited
The prospects for producing leptoquarks (LQs) in ultrahigh-energy (UHE)
neutrino nucleon collisions are re-examined in the light of recent
interpretations of HERA data in terms of leptoquark production. We update
predictions for cross-sections for the production of first- and
second-generation leptoquarks in UHE nu-N and nubar-N collisions including
(i) recent experimental limits on masses and couplings from the LEP and
TEVATRON colliders as well as rare processes,
(ii) modern parton distributions, and
(iii) radiative corrections to single leptoquark production.
If the HERA events are due to an SU(2) doublet leptoquark which couples
mainly to (e+,q) states, we argue that there are likely other LQ states which
couple to neutrinos which are close in mass, due to constraints from precision
electroweak measurements.Comment: 12 pages, LaTeX, 3 separate postscript figures. Added 1 reference
plus discussion, updated another referenc
Production of Pairs of Sleptoquarks in Hadron Colliders
We calculate the cross section for the production of pairs of scalar
leptoquarks (sleptoquarks) in a supersymmetric model, at hadron
colliders. We estimate higher order corrections by including terms
induced by soft-gluon corrections. Discovery bounds on the sleptoquark mass are
estimated at collider energies of 1.8, 2, and 4 TeV (Tevatron), and 16 TeV
(LHC).Comment: 8 pages, REVTEX, (1 fig. available on request),
LAVAL-PHY-94-13/McGILL-94-26/SPhT-94-07
ULAS J141623.94134836.3 - a faint common proper motion companion of a nearby L dwarf. Serendipitous discovery of a cool brown dwarf in UKIDSS DR6
New near-infrared large-area sky surveys (e.g. UKIDSS, CFBDS, WISE) go deeper
than 2MASS and aim at detecting brown dwarfs lurking in the Solar neighbourhood
which are even fainter than the latest known T-type objects, so-called Y
dwarfs. Using UKIDSS data, we have found a faint brown dwarf candidate with
very red optical-to-near-infrared but extremely blue near-infrared colours next
to the recently discovered nearby L dwarf SDSS J141624.08134826.7. We
check if the two objects are co-moving by studying their parallactic and proper
motion and compare the new object with known T dwarfs. The astrometric
measurements are consistent with a physical pair (75 AU) at a
distance 8 pc. The extreme colour (1.7) and
absolute magnitude (=17.780.46 and =19.450.52) make the new
object appear as one of the coolest (T600 K) and nearest brown
dwarfs, probably of late-T spectral type and possibly with a high surface
gravity (log 5.0).Comment: accepted for publication as a Letter in Astronomy and Astrophysics, 4
pages, 7 figures, changed subtitle and discussion, former Fig. 4 removed, new
Figs. 2, 6, and
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