184 research outputs found
Status of neutrino oscillations I: the three-neutrino scenario
We present a global analysis of neutrino oscillation data within the
three-neutrino oscillation scheme, including in our fit all the current solar
neutrino data, the reactor neutrino data from KamLAND and CHOOZ, the
atmospheric neutrino data from Super-Kamiokande and MACRO, and the first data
from the K2K long-baseline accelerator experiment. We determine the current
best fit values and allowed ranges for the three-flavor oscillation parameters,
discussing the relevance of each individual data set as well as the
complementarity of different data sets. Furthermore, we analyze in detail the
status of the small parameters theta_13 and Delta_m21^2 / Delta_m31^2, which
fix the possible strength of CP violating effects in neutrino oscillations.Comment: 13 pages, LaTeX file using JHEP3, 5 figures included. Talk given at
the International Workshop on Astroparticle and High Energy Physics
(AHEP-2003), Valencia, Spain, 14-18 October 200
Sterile neutrino oscillations after first MiniBooNE results
In view of the recent results from the MiniBooNE experiment we revisit the
global neutrino oscillation fit to short-baseline neutrino data by adding one
or two sterile neutrinos with eV-scale masses to the three Standard Model
neutrinos, and for the first time we consider also the global fit with three
sterile neutrinos. Four-neutrino oscillations of the (3+1) type have been only
marginally allowed before the recent MiniBooNE results, and become even more
disfavored with the new data (at the level of ). In the framework of
so-called (3+2) five-neutrino mass schemes we find severe tension between
appearance and disappearance experiments at the level of more than ,
and hence no satistfactory fit to the global data is possible in (3+2) schemes.
This tension remains also when a third sterile neutrino is added, and the
quality of the global fit does not improve significantly in a (3+3) scheme. It
should be noted, however, that in models with more than one sterile neutrino
the MiniBooNE results are in perfect agreement with the LSND appearance
evidence, thanks to the possibility of CP violation available in such
oscillation schemes. Furthermore, if disappearance data are not taken into
account (3+2) oscillations provide an excellent fit to the full MiniBooNE
spectrum including the event excess at low energies.Comment: 30 pages, 12 figures, minor improvements of text and abstract,
summary table added, matches version to be published in Phys. Rev.
Resurrecting the Dead Cone
The dead cone is a well-known effect in gauge theories, where radiation from
a charged particle of mass m and energy E is suppressed within an angular size
of m/E. This effect is universal as it does not depend on the spin of the
particle nor on the nature of the gauge interaction. It is challenging to
directly measure the dead cone at colliders, however, since the region of
suppressed radiation either is too small to be resolved or is filled by the
decay products of the massive particle. In this paper, we propose to use jet
substructure techniques to expose the dead cone effect in the strong-force
radiation pattern around boosted top quarks at the Large Hadron Collider. Our
study shows that with 300/fb of 13-14 TeV collision data, ATLAS and CMS could
obtain the first direct evidence of the dead cone effect and test its basic
features.Comment: 12 pages, 12 figures; v2: references added; v3: approximate version
to appear in PR
Status of Global Analysis of Neutrino Oscillation Data
In this talk we discuss some details of the analysis of neutrino data and our
present understanding of neutrino masses and mixing. This talk is based on
hep-ph/0306001, hep-ph/0306226 and hep-ph/0404085.Comment: 10 pages, LaTeX file using ws-procs9x6, 6 figures included. Talk
given by MCGG at the 5th Workshop on "Neutrino Oscillations and their Origin"
(NOON2004), Tokyo, Japan, February 11-15, 200
From ray to spray: augmenting amplitudes and taming fast oscillations in fully numerical neutrino codes
In this note we describe how to complement the neutrino evolution matrix
calculated at a given energy and trajectory with additional information which
allows to reliably extrapolate it to nearby energies or trajectories without
repeating the full computation. Our method works for arbitrary matter density
profiles, can be applied to any propagation model described by an Hamiltonian,
and exactly guarantees the unitarity of the evolution matrix. As a
straightforward application, we show how to enhance the calculation of the
theoretical predictions for experimentally measured quantities, so that they
remain accurate even in the presence of fast neutrino oscillations.
Furthermore, the ability to "move around" a given energy and trajectory opens
the door to precise interpolation of the oscillation amplitudes within a grid
of tabulated values, with potential benefits for the computation speed of
Monte-Carlo codes. We also provide a set of examples to illustrate the most
prominent features of our approach.Comment: 31 pages, 4 figure
Tracking down hyper-boosted top quarks
The identification of hadronically decaying heavy states, such as vector
bosons, the Higgs, or the top quark, produced with large transverse boosts has
been and will continue to be a central focus of the jet physics program at the
Large Hadron Collider (LHC). At a future hadron collider working at an
order-of-magnitude larger energy than the LHC, these heavy states would be
easily produced with transverse boosts of several TeV. At these energies, their
decay products will be separated by angular scales comparable to individual
calorimeter cells, making the current jet substructure identification
techniques for hadronic decay modes not directly employable. In addition, at
the high energy and luminosity projected at a future hadron collider, there
will be numerous sources for contamination including initial- and final-state
radiation, underlying event, or pile-up which must be mitigated. We propose a
simple strategy to tag such "hyper-boosted" objects that defines jets with
radii that scale inversely proportional to their transverse boost and combines
the standard calorimetric information with charged track-based observables. By
means of a fast detector simulation, we apply it to top quark identification
and demonstrate that our method efficiently discriminates hadronically decaying
top quarks from light QCD jets up to transverse boosts of 20 TeV. Our results
open the way to tagging heavy objects with energies in the multi-TeV range at
present and future hadron colliders.Comment: 19 pages + appendices, 17 figures; v2: added references, updated
cross section tabl
Robust Cosmological Bounds on Neutrinos and their Combination with Oscillation Results
We perform a global analysis of cosmological observables in generalized
cosmologies which depart from CDM models by allowing non-vanishing
curvature , dark energy with equation of state with , the presence of additional relativistic degrees of freedom , and neutrino masses . By combining the data from
cosmic microwave background (CMB) experiments (in particular the latest results
from WMAP-7), the present day Hubble constant (H0) measurement, the
high-redshift Type-I supernovae (SN) results and the information from large
scale structure (LSS) surveys, we determine the parameters in the
10-dimensional parameter space for such models. We present the results from the
analysis when the full shape information from the LSS matter power spectrum
(LSSPS) is included versus when only the corresponding distance measurement
from the baryon acoustic oscillations (BAO) is accounted for. We compare the
bounds on the neutrino mass scale in these generalized scenarios with those
obtained for the 6+1 parameter analysis in models and
we also study the dependence of those on the set of observables included in the
analysis. Finally we combine these results with the information on neutrino
mass differences and mixing from the global analysis of neutrino oscillation
experiments and derive the presently allowed ranges for the two laboratory
probes of the absolute scale of neutrino mass: the effective electron neutrino
mass in single beta decay and the effective Majorana neutrino mass in
neutrinoless decay.Comment: 19 pages, 4 figures. Acknowledgments correcte
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