614 research outputs found
Associated Production of a W Boson and One b Jet
We calculate the production of a W boson and a single b jet to
next-to-leading order in QCD at the Fermilab Tevatron and the CERN Large Hadron
Collider. Both exclusive and inclusive cross sections are presented. We
separately consider the cross section for jets containing a single b quark and
jets containing a b-anti b pair. There are a wide variety of processes that
contribute, and it is necessary to include them all in order to have a complete
description at both colliders.Comment: LaTeX, 16 pages, 22 postscript figures; version published in Phys.
Rev.
Global fits to neutrino oscillation data
I summarize the determination of neutrino oscillation parameters within the
three-flavor framework from world neutrino oscillation data with date of May
2006, including the first results from the MINOS long-baseline experiment. It
is illustrated how the determination of the leading "solar" and "atmospheric"
parameters, as well as the bound on emerge from an interplay of
various complementary data sets. Furthermore, I discuss possible implications
of sub-leading three-flavor effects in present atmospheric neutrino data
induced by and for the bound on
and non-maximal values of , emphasizing, however, that these
effects are not statistically significant at present. Finally, in view of the
upcoming MiniBooNE results I briefly comment on the problem to reconcile the
LSND signal.Comment: 5 pages, 5 figures, talk presented at the SNOW2006 workshop,
Stockholm, 2-6 May 200
The Bulk RS KK-gluon at the LHC
We study the possibility of discovering and measuring the properties of the
lightest Kaluza-Klein excitation of the gluon in a Randall-Sundrum scenario
where the Standard Model matter and gauge fields propagate in the bulk. The
KK-gluon decays primarily into top quarks. We discuss how to use the final states to discover and probe the properties of the KK-gluon.
Identification of highly energetic tops is crucial for this analysis. We show
that conventional identification methods relying on well separated decay
products will not work for heavy resonances but suggest alternative methods for
top identification for energetic tops. We find, conservatively, that resonances
with masses less than 5 TeV can be discovered if the algorithm to identify high
tops can reject the QCD background by a factor of 10. We also find that
for similar or lighter masses the spin can be determined and for lighter masses
the chirality of the coupling to can be measured. Since the energetic
top pair final state is a generic signature for a large class of new physics as
the top quark presumably couples most strongly to the electroweak symmetry
breaking sector, the methods we have outlined to study the properties of the
KK-gluon should also be important in other scenarios.Comment: 21 pages, 13 figure
A combined analysis of short-baseline neutrino experiments in the (3+1) and (3+2) sterile neutrino oscillation hypotheses
We investigate adding two sterile neutrinos to resolve the apparent tension
existing between short-baseline neutrino oscillation results and
CPT-conserving, four-neutrino oscillation models. For both (3+1) and (3+2)
models, the level of statistical compatibility between the combined dataset
from the null short-baseline experiments Bugey, CHOOZ, CCFR84, CDHS, KARMEN,
and NOMAD, on the one hand; and the LSND dataset, on the other, is computed. A
combined analysis of all seven short-baseline experiments, including LSND, is
also performed, to obtain the favored regions in neutrino mass and mixing
parameter space for both models. Finally, four statistical tests to compare the
(3+1) and the (3+2) hypotheses are discussed. All tests show that (3+2) models
fit the existing short-baseline data significantly better than (3+1) models.Comment: 16 pages, 15 figures. Added NOMAD data to the analysis, one
statistical test, and two figures. References and text added. Version
submitted to PR
Physics Reach of High-Energy and High-Statistics IceCube Atmospheric Neutrino Data
This paper investigates the physics reach of the IceCube neutrino detector
when it will have collected a data set of order one million atmospheric
neutrinos with energies in the 0.1 \sim 10^4 TeV range. The paper consists of
three parts. We first demonstrate how to simulate the detector performance
using relatively simple analytic methods. Because of the high energies of the
neutrinos, their oscillations, propagation in the Earth and regeneration due to
\tau decay must be treated in a coherent way. We set up the formalism to do
this and discuss the implications. In a final section we apply the methods
developed to evaluate the potential of IceCube to study new physics beyond
neutrino oscillations. Not surprisingly, because of the increased energy and
statistics over present experiments, existing bounds on violations of the
equivalence principle and of Lorentz invariance can be improved by over two
orders of magnitude. The methods developed can be readily applied to other
non-conventional physics associated with neutrinos.Comment: 21 pages, 7 figures, Revtex
Triplet Leptogenesis in Left-Right Symmetric Seesaw Models
We discuss scalar triplet leptogenesis in a specific left-right symmetric
seesaw model. We show that the Majorana phases that are present in the model
can be effectively used to saturate the existing upper limit on the
CP-asymmetry of the triplets. We solve the relevant Boltzmann equations and
analyze the viability of triplet leptogenesis. It is known for this kind of
scenario that the efficiency of leptogenesis is maximal if there exists a
hierarchy between the branching ratios of the triplet decays into leptons and
Higgs particles. We show that triplet leptogenesis typically favors branching
ratios with not too strong hierarchies, since maximal efficiency can only be
obtained at the expense of suppressed CP-asymmetries.Comment: 16 pages, 5 figures, published versio
Extraction of the atmospheric neutrino fluxes from experimental event rate data
The precise knowledge of the atmospheric neutrino fluxes is a key ingredient
in the interpretation of the results from any atmospheric neutrino experiment.
In the standard atmospheric neutrino data analysis, these fluxes are
theoretical inputs obtained from sophisticated numerical calculations. In this
contribution we present an alternative approach to the determination of the
atmospheric neutrino fluxes based on the direct extraction from the
experimental data on neutrino event rates. The extraction is achieved by means
of a combination of artificial neural networks as interpolants and Monte Carlo
methods.Comment: 6 pages, 2 figs, to appear in the proceedings of the 2nd
International Conference on Quantum Theories and Renormalization Group in
Gravity and Cosmology, Barcelona, July 200
Radiography of the Earth's Core and Mantle with Atmospheric Neutrinos
A measurement of the absorption of neutrinos with energies in excess of 10
TeV when traversing the Earth is capable of revealing its density distribution.
Unfortunately, the existence of beams with sufficient luminosity for the task
has been ruled out by the AMANDA South Pole neutrino telescope. In this letter
we point out that, with the advent of second-generation kilometer-scale
neutrino detectors, the idea of studying the internal structure of the Earth
may be revived using atmospheric neutrinos instead.Comment: 4 pages, LaTeX file using RevTEX4, 2 figures and 1 table included.
Matches published versio
Precision Calculations for Future Colliders
I discuss the motivations for, and the status of, precision calculations for
the Large Hadron Collider (LHC) and the planned International Linear Collider
(ILC).Comment: latex, uses ws-ijmpe.cls, 19 pages, 9 figures, 1 table, based on a
talk given at the symposium "50 Years of High Energy Physics at UB", to
appear in International Journal of Modern Physics
Flavour physics of the RS model with KK masses reachable at LHC
The version of the higher-dimensional Randall-Sundrum (RS) model with matter
in the bulk, which addresses the gauge hierarchy problem, has additional
attractive features. In particular, it provides an intrinsic geometrical
mechanism that can explain the origin of the large mass hierarchies among the
Standard Model fermions. Within this context, a good solution for the gauge
hierarchy problem corresponds to low masses for the Kaluza-Klein (KK)
excitations of the gauge bosons. Some scenarios have been proposed in order to
render these low masses (down to a few TeV) consistent with precision
electroweak measurements. Here, we give specific and complete realizations of
this RS version with small KK masses, down to 1 TeV, which are consistent with
the entire structure of the fermions in flavour space: (1) all the last
experimental data on quark/lepton masses and mixing angles (including massive
neutrinos of Dirac type) are reproduced, (2) flavour changing neutral current
constraints are satisfied and (3) the effective suppression scales of
non-renormalizable interactions (in the physical basis) are within the bounds
set by low energy flavour phenomenology. Our result, on the possibility of
having KK gauge boson modes as light as a few TeV, constitutes one of the first
theoretical motivations for experimental searches of direct signatures at the
LHC collider, of this interesting version of the RS model which accommodates
fermion masses.Comment: 27 pages, Latex file. References and comments adde
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