43,729 research outputs found
The puzzles in and decays: possible implications for R-parity violating supersymmetry
Recent experiments suggest that certain data of decays
are inconsistent with the standard model expectations. We try to explain the
discrepancies with R-parity violating suppersymmetry. By employing the QCD
factorization approach, we study these decays in the minimal supersymmetric
standard model with R-parity violation. We show that R-parity violation can
resolve the discrepancies in both and decays, and
find that in some regions of parameter spaces all these requirements, including
the CP averaged branching ratios and the direct CP asymmetries, can be
satisfied. Furthermore, we have derived stringent bounds on relevant R-parity
violating couplings from the latest experimental data, and some of these
constraints are stronger than the existing bounds.Comment: 24 pages, 6 figures and 5 tables. Text revised. Final version to
appear in PR
Framed vertex operator algebras, codes and the moonshine module
For a simple vertex operator algebra whose Virasoro element is a sum of
commutative Virasoro elements of central charge 1/2, two codes are introduced
and studied. It is proved that such vertex operator algebras are rational. For
lattice vertex operator algebras and related ones, decompositions into direct
sums of irreducible modules for the product of the Virasoro algebras of central
charge 1/2 are explicitly described. As an application, the decomposition of
the moonshine vertex operator algebra is obtained for a distinguished system of
48 Virasoro algebras.Comment: Latex, 54 page
Polarizations in decays B_{u,d}\to VV and possible implications for R-parity violating SUSY
Recently BABAR and Belle have measured anomalous large transverse
polarizations in some pure penguin decays, which might be
inconsistent with the Standard Model expectations. We try to explore its
implications for R-parity violating (RPV) supersymmetry. The QCD factorization
approach is employed for the hadronic dynamics of B decays. We find that it is
possible to have parameter spaces solving the anomaly. Furthermore, we have
derived stringent bounds on relevant RPV couplings from the experimental data,
which is useful for further studies of RPV phenomena.Comment: 26 pages, 12 eps figures. Typos corrected and references added. Final
version to appear in PR
A complex environment around Cir X-1
We present the results of an archival 54 ks long Chandra observation of the
peculiar source Cir X--1 during the phase passage 0.223-0.261. A comparative
analysis of X-ray spectra, selected at different flux levels of the source,
allows us to distinguish between a very hard state, at a low countrate, and a
brighter, softer, highly absorbed spectrum during episodes of flaring activity,
when the unabsorbed source luminosity is about three times the value in the
hard state. The spectrum of the hard state clearly shows emission lines of
highly ionized elements, while, during the flaring state, the spectrum also
shows strong resonant absorption lines. The most intense and interesting
feature in this latter state is present in the Fe K alpha region: a very
broadened absorption line at energies ~ 6.5 keV that could result from a
smeared blending of resonant absorption lines of moderately ionized iron ions
(Fe XX - Fe XXIV). We also observe strong resonant absorption lines of Fe XXV
and Fe XXVI, together with a smeared absorption edge above 7 keV. We argue that
the emitting region during the quiescent/hard state is constituted of a purely
photo-ionized medium, possibly present above an accretion disk, or of a
photo-ionized plasma present in a beamed outflow. During the flaring states the
source undergoes enhanced turbulent accretion that modifies both the accretion
geometry and the optical depth of the gas surrounding the primary X-ray source.Comment: Accepted for publication in Ap
Optical spectroscopy study on single crystalline LaFeAsO
Millimeter-sized single crystals of LaFeAsO were grown from NaAs flux and the
in-plane optical properties were studied over a wide frequency range. A sizable
electronic correlation effect was indicated from the analysis of the
free-carrier spectral weight. With decreasing temperature from 300 K, we
observed a continuous suppression of the spectral weight near 0.6 eV. But a
spin-density-wave gap formation at lower energy scale was seen only in the
broken-symmetry state. We elaborate that both the itinerancy and local spin
interactions of Fe\emph{3d} electrons are present for the FeAs-based systems;
however, the establishment of the long-range magnetic order at low temperature
has a dominantly itinerant origin.Comment: 4 figures, 5 page
Levinson's Theorem for Non-local Interactions in Two Dimensions
In the light of the Sturm-Liouville theorem, the Levinson theorem for the
Schr\"{o}dinger equation with both local and non-local cylindrically symmetric
potentials is studied. It is proved that the two-dimensional Levinson theorem
holds for the case with both local and non-local cylindrically symmetric cutoff
potentials, which is not necessarily separable. In addition, the problems
related to the positive-energy bound states and the physically redundant state
are also discussed in this paper.Comment: Latex 11 pages, no figure, submitted to J. Phys. A Email:
[email protected], [email protected]
NMR study of a bimesogenic liquid crystal with two nematic phases
Recent interest in bimesogenic liquid crystals showing two nematic phases has led us to investigate the nematic mean-field interactions in these nematic phases by using rigid solutes as probes. The nematic potential that is modelled by two independent Maier-Saupe terms is successful in fitting the observed dipolar couplings (order parameters) of para-, meta- and ortho-dichlorobenzene solutes in both the nematic phases of 39 wt% of 4-n-pentyl-4âČ-cyanobiphenyl (5CB) in α,Ï-bis(4-4âČ-cyanobiphenyl)nonane (CB_C9_CB) to better than the 5% level. The derived liquid-crystal potential parameters Gâ and Gâ for each solute in the N and Ntb phases will be discussed. The most interesting observation is that G1 (associated with size and shape interactions) is almost constant in the Ntb phase, whereas Gâ (associated with longer-range electrostatic interactions) has large variation, even changing sign
Modular Invariance for Twisted Modules over a Vertex Operator Superalgebra
The purpose of this paper is to generalize Zhu's theorem about characters of
modules over a vertex operator algebra graded by integer conformal weights, to
the setting of a vertex operator superalgebra graded by rational conformal
weights. To recover SL_2(Z)-invariance of the characters it turns out to be
necessary to consider twisted modules alongside ordinary ones. It also turns
out to be necessary, in describing the space of conformal blocks in the
supersymmetric case, to include certain `odd traces' on modules alongside
traces and supertraces. We prove that the set of supertrace functions, thus
supplemented, spans a finite dimensional SL_2(Z)-invariant space. We close the
paper with several examples.Comment: 42 pages. Published versio
Deuteron and proton NMR study of Dâ, p-dichlorobenzene and 1,3,5-trichlorobenzene in bimesogenic liquid crystals with two nematic phases
The solutes dideuterium, 1,3,5-trichlorobenzene and p-dichlorobenzene (pdcb) are co-dissolved in a 61/39 wt% mixture of CBC9CB/5CB, a bimesogenic liquid crystal with two nematic phases. NMR spectra are collected for each solute. The local electric field gradient (FZZ) is obtained from the dideuterium spectrum. A double Maier-Saupe potential (MSMS) is used to rationalize the order parameters of pdcb. The liquid-crystal fields Gâ and Gâ are taken to be due to size and shape interactions and interactions between the solute molecular quadrupole and the mean FZZ of the medium. The FZZâs obtained from Dâ and Gâ (from pdcb) are compared and discussed
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