104 research outputs found
A comparison of ultraviolet sensitivities in universal, nonuniversal, and split extra dimensional models
We discuss the origin of ultraviolet sensitivity in extra dimensional
theories, and compare and contrast the cutoff dependences in universal,
nonuniversal and split five dimensional models. While the gauge bosons and
scalars are in the five dimensional bulk in all scenarios, the locations of the
fermions are different in different cases. In the universal model all fermions
can travel in the bulk, in the nonuniversal case they are all confined at the
brane, while in the split scenario some are in the bulk and some are in the
brane. A possible cure from such divergences is also discussed.Comment: 9 pages, Latex, no figure, v2: further clarifications and references
added, accepted for publication in Phys. Rev.
Effects of Universal Extra Dimensions on Higgs signals at LHC
A major focus at the Large Hadron Collider (LHC) will be Higgs boson studies
and it would be an interesting prospect to simultaneously probe for physics
beyond the Standard Model (SM) in the Higgs signals. In this work we show as to
what extent, the effects of Universal Extra Dimension (UED) can be isolated at
the LHC through the Higgs signals. By doing a detailed study of the different
uncertainties involved in the measurement of the rates for the process pp --> h
--> gamma gamma we estimate the extent to which these uncertainties can mask
the effects of the contributions coming from UED.Comment: 13 pages, LateX, Title changed, text and figures modified. Version to
appear in IJMP
Identifying the contributions of Universal Extra Dimensions in the Higgs sector at linear e+ e- colliders
We study the dilepton-dijet signal in the dominant Higgs production channel
at a linear e+ e- collider. We estimate the effects of Universal Extra
Dimension (UED) by a simple analysis of the cross-sections. The heavy
Kaluza-Klein excitations of the Standard Model fields in UED can significantly
alter the decay properties of the Higgs boson to loop-driven final states. We
show that by taking a simple ratio between cross-sections of two different
final states this difference can be very easily highlighted.Comment: Some parts of the text modified. 1 figure added. Version to appear in
IJMP
Singlet Fermionic Dark Matter explains DAMA signal
It has been suggested that, considering channeling effect, the order of a few
GeV dark matters which are elastically scattered from detector nuclei might be
plausible candidates reconciling the DAMA annual modulation signal with the
results of other null experiments. We show that Singlet Fermionic Dark Matter
can be such a dark matter candidate, simultaneously providing the correct
thermal relic density which is consistent with the WMAP data.Comment: 9 pages, 3 figure
Precision Measurements and Fermion Geography in the Randall-Sundrum Model Revisited
We re-examine the implications of allowing fermion fields to propagate in the
five-dimensional bulk of the Randall-Sundrum (RS) localized gravity model. We
find that mixing between the Standard Model top quark and its Kaluza Klein
excitations generates large contributions to the rho parameter and consequently
restricts the fundamental RS scale to lie above 100 TeV. To circumvent this
bound we propose a `mixed' scenario which localizes the third generation
fermions on the TeV brane and allows the lighter generations to propagate in
the full five-dimensional bulk. We show that this construction naturally
reproduces the observed m_c / m_t and m_s / m_b hierarchies. We explore the
signatures of this scenario in precision measurements and future high energy
collider experiments. We find that the region of parameter space that addresses
the hierarchies of fermion Yukawa couplings permits a Higgs boson with a mass
of 500 GeV and remains otherwise invisible at the LHC. However, the entire
parameter region consistent with electroweak precision data is testable at
future linear colliders. We briefly discuss possible constraints on this
scenario arising from flavor changing neutral currents.Comment: 44 pages, 20 ps files; VII, typos fixed and refs adde
Radiative Corrections to Fixed Target Moller Scattering Including Hard Bremsstrahlung Effects
We present a calculation of the complete electroweak radiative
corrections to the Moller scattering process e^-e^- -> e^-e^-, including hard
bremsstrahlung contributions. We study the effects of these corrections on both
the total cross section and polarization asymmetry measured in low energy fixed
target experiments. Numerical results are presented for the experimental cuts
relevant for E-158, a fixed target e^-e^- experiment being performed at SLAC;
the effect of hard bremsstrahlung is to shift the measured polarization
asymmetry by approximately +4%. We briefly discuss the remaining theoretical
uncertainty in the prediction for the low energy Moller scattering polarization
asymmetry.Comment: 22 pgs; minor clarifications added and typos fixe
Prospects For Identifying Dark Matter With CoGeNT
It has previously been shown that the excess of events reported by the CoGeNT
collaboration could be generated by elastically scattering dark matter
particles with a mass of approximately 5-15 GeV. This mass range is very
similar to that required to generate the annual modulation observed by
DAMA/LIBRA and the gamma rays from the region surrounding the Galactic Center
identified within the data of the Fermi Gamma Ray Space Telescope. To
confidently conclude that CoGeNT's excess is the result of dark matter,
however, further data will likely be needed. In this paper, we make projections
for the first full year of CoGeNT data, and for its planned upgrade. Not only
will this body of data more accurately constrain the spectrum of nuclear recoil
events, and corresponding dark matter parameter space, but will also make it
possible to identify seasonal variations in the rate. In particular, if the
CoGeNT excess is the product of dark matter, then one year of CoGeNT data will
likely reveal an annual modulation with a significance of 2-3. The
planned CoGeNT upgrade will not only detect such an annual modulation with high
significance, but will be capable of measuring the energy spectrum of the
modulation amplitude. These measurements will be essential to irrefutably
confirming a dark matter origin of these events.Comment: 6 pages, 6 figure
Signals for Non-Commutative Interactions at Linear Colliders
Recent theoretical results have demonstrated that non-commutative geometries
naturally appear within the context of string/M-theory. One consequence of this
possibility is that QED takes on a non-abelian nature due to the introduction
of 3- and 4-point functions. In addition, each QED vertex acquires a momentum
dependent phase factor. We parameterize the effects of non-commutative
space-time co-ordinates and show that they lead to observable signatures in
several QED processes in collisions. In particular, we
examine pair annihilation, Moller and Bhabha scattering, as well as
scattering and show that non-commutative scales
of order a TeV can be probed at high energy linear colliders.Comment: 51 pages, 23 figures, typos corrected, figure and references adde
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