12,229 research outputs found
decays revisited: branching ratios and T-odd momenta correlations
We calculate the branching ratios of the decays, and the T-odd triple momenta correlations
, due to the
electromagnetic final state interaction, in these processes. The contributions
on the order of and to the corresponding amplitudes
are treated exactly. For the branching ratios, the corrections on the order of
are estimated and demonstrated to be small. We compare the results
with those of other authors. In some cases our results differ considerably from
the previous ones.Comment: 13 pages, 11 figures; references adde
Searching for Composite Neutrinos in the Cosmic Microwave Background
We analyze signals in the Cosmic Microwave Background (CMB) in theories where
the small Dirac neutrino masses arise as a consequence of the compositeness of
right-handed neutrinos. In such theories, the right-handed neutrinos are
massless ``baryons'' of a new strong gauge interaction. We find that the
results crucially depend on whether or not the new strong sector undergoes
chiral symmetry breaking. In the case with chiral symmetry breaking, we find
that there are indeed signals in the CMB, but none of them is a direct
consequence of neutrino compositeness. In contrast, if the underlying theory
does not undergo chiral symmetry breaking, the large scattering cross-section
among the composites gives rise to a sizable CMB signal over a wide region of
the parameter space, and it can potentially probe whether the neutrino mass
spectrum is hierarchical, inverse hierarchical, or degenerate. We also discuss
collider constraints on the compositeness in the context of the CMB signals.Comment: 26 pages. References and clarifying comments added. Version appearing
to JHE
Experimental Status of Exotic Mesons and the GlueX Experiment
One of the unanswered and most fundamental questions in physics regards the
nature of the confinement mechanism of quarks and gluons in QCD. Exotic hybrid
mesons manifest gluonic degrees of freedom and their spectroscopy will provide
the data necessary to test assumptions in lattice QCD and the specific
phenomenology leading to confinement. Within the past two decades a number of
experiments have put forth tantalizing evidence for the existence of exotic
hybrid mesons in the mass range below 2 GeV. This talk represents an overview
of the available data and what has been learned. In looking toward the future,
the GlueX experiment at Jefferson Laboratory represents a new initiative that
will perform detailed spectroscopy of the light-quark meson spectrum. This
experiment and its capabilities will be reviewed.Comment: 10 pages, 8 figures, 2nd Meeting of the APS Topical Group on Hadron
Physics GHP06, Nashville, TN (10/22-10/24/06
Quantum switch for single-photon transport in a coupled superconducting transmission line resonator array
We propose and study an approach to realize quantum switch for single-photon
transport in a coupled superconducting transmission line resonator (TLR) array
with one controllable hopping interaction. We find that the single-photon with
arbitrary wavevector can transport in a controllable way in this system. We
also study how to realize controllable hopping interaction between two TLRs via
a superconducting quantum interference device (SQUID). When the frequency of
the SQUID is largely detuned from those of the two TLRs, the variables of the
SQUID can be adiabatically eliminated and thus a controllable interaction
between two TLRs can be obtained.Comment: 4 pages,3 figure
Minimal Length Uncertainty Relation and Hydrogen Atom
We propose a new approach to calculate perturbatively the effects of a
particular deformed Heisenberg algebra on energy spectrum. We use this method
to calculate the harmonic oscillator spectrum and find that corrections are in
agreement with a previous calculation. Then, we apply this approach to obtain
the hydrogen atom spectrum and we find that splittings of degenerate energy
levels appear. Comparison with experimental data yields an interesting upper
bound for the deformation parameter of the Heisenberg algebra.Comment: 7 pages, REVTe
Model for Small neutrino masses at the TeV Scale
We propose a model for neutrino mass generation in wich no physics beyond a
TeV is required. We extend the standard model by adding two charged singlet
fields with lepton number two. Dirac neutrino masses are
generated at the one loop level. Small left handed majorana neutrino masses can
be generated via the seesaw mechanism with right handed neutrino masses
are of order TeV scale.Comment: 13 pages, 2 figure
Dark Matter in Gauge Mediation from Emergent Supersymmetry
We investigated the viability of neutralino dark matter in the gauge
mediation from emergent supersymmetry proposal. In this proposal, supersymmetry
is broken at Planck scale and consequently, the gravitino is superheavy and
completely decouples from the low energy theory. Squarks and sleptons obtain
their soft masses dominantly through gauge mediation with other mechanisms
highly suppressed. The lightest supersymmetric partner, in contrast to
traditional gauge mediation, is a neutralino which is also a dark matter
candidate. By explicit calculation of the low energy spectra, the parameter
space was constrained using the WMAP observed relic density of dark matter,
LEP2 Higgs mass bounds, collider bounds on supersymmetric partners and exotic
B-meson decays. We found that the model has intriguing hybrid features such as
a nearly gauge-mediated spectrum (the exception being the superheavy gravitino)
but with a dominant mSUGRA-like bino-stau coannihilation channel and at large
, A-resonance-like annihilation.Comment: 14 pages, 4 figure
Possible Excess in Charged Current Events with High-Q^2 at HERA from Stop and Sbottom Production
We investigate a production process e^+p \to \st X \to \sb W^+ X at HERA,
where we consider a decay mode \sb \to \bar{\nu}_e d of the sbottom in the
framework of an R-parity breaking supersymmetric standard model. Both processes
of the stop production e^+ d \to \st and the sbottom decay \sb \to
\bar{\nu}_e d are originated from an R-parity breaking superpotential
. One of signatures of the
process should be a large missing transverse momentum plus multijet events
corresponding to hadronic decays of the . It is shown that the signal could
appear as an event excess in the charged current (CC) processes with the high at HERA. We compare expected event distributions with
the CC data recently reported by the H1 and ZEUS groups at HERA. Methods for
extracting the signal from the standard CC processes are also discussed.Comment: 13 pages, LaTeX, 3 figure
New calibrations and time stability of the response of the INTERCAST CR-39
We present new calibrations of different production batches (from 1989 to
1999) of the INTERCAST CR-39, using the BNL-AGS 1 A GeV iron beam. The
comparison with previous results, obtained with the 158 A GeV lead beam from
the CERN-SPS shows that, while each production batch has a different
calibration curve (mainly due to minor differences in the production
conditions), the aging effect is negligible. We also tested the dependence of
the CR-39 response from the time elapsed between exposure and analysis (fading
effect). The fading effect, if present, is less than 10%. It may be compatible
with the experimental uncertainties on the bulk etching rate vB.Comment: 9 pages, 4 EPS figures, .pdf file. Talk presented by M. Giorgini at
the 20 Int. Conf. on Nuclear Tracks in Solids, Portoroz (Slovenia), Aug
28-Sep 1, 200
Tracing CP-violation in Lepton Flavor Violating Muon Decays
Although the Lepton Flavor Violating (LFV) decay is
forbidden in the Standard Model (SM), it can take place within various theories
beyond the SM. If the branching ratio of this decay saturates its present bound
[{\it i.e.,} Br], the forthcoming
experiments can measure the branching ratio with high precision and
consequently yield information on the sources of LFV. In this letter, we show
that for polarized , by studying the angular distribution of the
transversely polarized positron and linearly polarized photon we can derive
information on the CP-violating sources beyond those in the SM. We also study
the angular distribution of the final particles in the decay where is defined to be the more energetic positron. We show
that transversely polarized can provide information on a certain
combination of the CP-violating phases of the underlying theory which would be
lost by averaging over the spin of .Comment: 6 pages, 2 figure
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