1,117 research outputs found
Nonleptonic two-body charmless B decays involving a tensor meson in ISGW2 model
Nonleptonic charmless B decays into a pseudoscalar (P) or a vector (V) meson
accompanying a tensor (T) meson are re-analyzed. We scrutinize the hadronic
uncertainties and ambiguities of the form factors which appear in the
literature. The Isgur-Scora-Grinstein-Wise updated model (ISGW2) is adopted to
evaluate the relevant hadronic matrix elements. We calculate the branching
ratios and CP asymmetries for various decay processes. With the
ISGW2 model, the branching ratios are enhanced by about an order of magnitude
compared to the previous estimates. We show that the ratios \calB(B\to
VT)/\calB(B\to PT) for some strangeness-changing processes are very sensitive
to the CKM angle ().Comment: 23 pages, REVTEX; minor clarifications included; to appear in Phys.
Rev.
Decays in R-parity violating supersymmetry
In light of the recent experimental data from factories, We try to
explain the large branching ratio (compared to the Standard Model prediction)
of the decay in the context of R-parity violating
(\rpv) supersymmetry. We investigate other observed modes
and find that only two pairs of \rpv coupling can satisfy the requirements
without affecting the other and decay modes except the
mode . We also calculate the CP asymmetry for the observed decay
modes affected by the new couplings.Comment: 3 pages, 1 figure, Proceedings of the Fifth KEK Topical Conferenc
A study of semi-inclusive charmless decays
We study semi-inclusive charmless decays in detail, such as
, , , where does not contain a charm (anti)quark. We find that
the process () can be particularly
useful for determination of the CKM matrix element . We calculate and
present the branching ratio (BR) of as a function of
, with an estimate of possible uncertainties. It is expected that the
BR is an order of . Our estimation indicates that one can
phenomenologically determine with reasonable accuracy by measuring
the BR of ().Comment: 18 pages, 7 figures; Revtex; version accepted for publication in Eur.
Phys. J.
Heavy Baryonic Decays of \Lambda_b \to \Lambda \eta^{(\prime)} and Nonspectator Contribution
We calculate the branching ratios of the hadronic \Lambda_b decays to \eta
and \eta^\prime in the factorization approximation where the form factors are
estimated via QCD sum rules and the pole model. Our results indicate that,
contrary to B\to K\eta^{(\prime)} decays, the branching ratios for
\Lambda_b\to\Lambda\eta and \Lambda_b\to\Lambda\eta^\prime are more or less the
same in the hadronic \Lambda_b transitions. We estimate the branching ratio of
\Lambda_b\to\Lambda\eta^{(\prime)} to be 10.80 (10.32)\times 10^{-6} in QCD sum
rules, and 2.78 (2.96)\times 10^{-6} in the pole model. We also estimate the
nonfactorizable gluon fusion contribution to \Lambda_b\to\Lambda\eta^\prime
decay by dividing this process into strong and weak vertices. Our results point
to an enhancement of more than an order of magnitude due to this mechanism.Comment: 16 pages, ReVTeX, 5 eps figure
The Dark Matter Density in the Solar Neighborhood reconsidered
Both the gas flaring and the dip in the rotation curve, which was recently
reconfirmed with precise measurements using the VERA VLBI array in Japan,
suggest doughnut-like substructure in the dark matter (DM) halo. A global fit
to all available data shows that the data are indeed best described by an NFW
DM profile complemented by two doughnut-like DM substructures with radii of 4.2
and 12.4 kpc, which coincide with the local dust ring and the Monocerus ring of
stars, respectively. Both regions have been suggested as regions with tidal
streams from "shredded" satellites. If real, the radial extensions of these
nearby ringlike structures enhance the local dark matter density by a factor of
four to about 1.3 GeV/cm.
It is shown that i) this higher DM density is perfectly consistent with the
local gravitational potential determining the surface density and the local
matter density (Oort limit), ii) previous determinations of the surface density
were biased by the assumption of a smoothly varying DM halo and iii) the
s-shaped gas flaring is explained. Such a possible enhancement of the local DM
density is of great interest for direct DM searches and would change the
directional dependence for indirect DM searches.Comment: 14 pages, 4 figures, extended version, accepted for publication in
JCA
Cost-benefit analysis of introducing next-generation sequencing (metagenomic) pathogen testing in the setting of pyrexia of unknown origin
Pyrexia of unknown origin (PUO) is defined as a temperature of >38.3°C that lasts for >3 weeks, where no cause can be found despite appropriate investigation. Existing protocols for the work-up of PUO can be extensive and costly, motivating the application of recent advances in molecular diagnostics to pathogen testing. There have been many reports describing various analytical methods and performance of metagenomic pathogen testing in clinical samples but the economics of it has been less well studied. This study pragmatically evaluates the feasibility of introducing metagenomic testing in this setting by assessing the relative cost of clinically-relevant strategies employing this investigative tool under various cost and performance scenarios using Singapore as a demonstration case, and assessing the price and performance benchmarks, which would need to be achieved for metagenomic testing to be potentially considered financially viable relative to the current diagnostic standard. This study has some important limitations: we examined only impact of introducing the metagenomic test to the overall diagnostic cost and excluded costs associated with hospitalization and makes assumptions about the performance of the routine diagnostic tests, limiting the cost of metagenomic test, and the lack of further work-up after positive pathogen detection by the metagenomic test. However, these assumptions were necessary to keep the model within reasonable limits. In spite of these, the simplified presentation lends itself to the illustration of the key insights of our paper. In general, we find the use of metagenomic testing as second-line investigation is effectively dominated, and that use of metagenomic testing at first-line would typically require higher rates of detection or lower cost than currently available in order to be justifiable purely as a cost-saving measure. We conclude that current conditions do not warrant a widespread rush to deploy metagenomic testing to resolve any and all uncertainty, but rather as a front-line technology that should be used in specific contexts, as a supplement to rather than a replacement for careful clinical judgement
Total hip replacement. Results of a postal survey of current practice on the cement fixation of the acetabular cup in the UK
Previous finite element studies and laboratory investigations on reconstructed acetabulum joints show that long-term fixation of the acetabular cup in total hip replacements (THRs) is influenced by surgical fixation techniques. The aim of this study is to determine and understand the reasons of current practice in the cement fixation of the acetabular cup in THRs in the UK. Following a pilot study, a postal survey was carried out among 1350 orthopaedic consultants. Response rate was 40% and data obtained from the returned questionnaires provided information about the current practice of 431 consultants with an average of 16.5 years of experience and who perform an average of 55 cemented THR operations annually. The survey showed wide variations in the fixation methods of the acetabular component. 95% of the respondents use cement to fix the acetabular cup, 46% maintain the subchondral bone and 63 % use a flanged acetabular cup. The numbers of anchorage holes drilled vary from zero to thirty-six and drill diameters vary from 2 to 15 mm. Anchorage hole depths vary from 3 to 20 mm. Given the variability of surgical fixation methods, further studies need to be carried out to determine how fixation techniques could be improved to increase the longevity of the acetabular component in THRs. Further investigations could lead to a better understanding of the factors that contribute to the stability of THRs
Penta-quark states with hidden charm and beauty
More and more hadron states are found to be difficult to be accommodated by
the quenched quark models which describe baryons as 3-quark states and mesons
as antiquark-quark states. Dragging out an antiquark-quark pair from the gluon
field in hadrons should be an important excitation mechanism for hadron
spectroscopy. Our recent progress on the penta-quark states with hidden charm
and beauty is reviewed.Comment: Plenary talk at the 5th Asia-Pacific Conference on Few-Body Problems
in Physics 2011 (APFB2011), 22-26 Aug., 2011, Seoul, Kore
CP Asymmetries of and Decays Using a Global Fit in QCD Factorization
We analyze the CP asymmetries of and
modes in the QCD improved factorization framework. For our calculation we use
the phenomenological parameters predetermined from the global fit for the
available and modes (without the quark-level subprocess ). We show that the large negative and
the large branching ratio for can be simultaneously
explained in the context of supersymmetry (SUSY). The R-parity conserving SUGRA
models are used and their parameter space is constrained with the observed dark
matter relic density along with other experimental constraints. The R-parity
violating SUSY models are also used to show that they can provide solutions. We
calculate the CP asymmetries for different
and modes and show that the SUSY model
predictions are consistent with the available experimental data.Comment: 13 pages, No figure; Some references adde
Toward closing rice telomere gaps: mapping and sequence characterization of rice subtelomere regions.
Despite the collective efforts of the international community to sequence the complete rice genome, telomeric regions of most chromosome arms remain uncharacterized. In this report we present sequence data from subtelomere regions obtained by analyzing telomeric clones from two 8.8 × genome equivalent 10-kb libraries derived from partial restriction digestion with HaeIII or Sau3AI (OSJNPb HaeIII and OSJNPc Sau3AI). Seven telomere clones were identified and contain 25¿100 copies of the telomere repeat (CCCTAAA)n on one end and unique sequences on the opposite end. Polymorphic sequence-tagged site markers from five clones and one additional PCR product were genetically mapped on the ends of chromosome arms 2S, 5L, 10S, 10L, 7L, and 7S. We found distinct chromosome-specific telomere-associated tandem repeats (TATR) on chromosome 7 (TATR7) and on the short arm of chromosome 10 (TATR10s) that showed no significant homology to any International Rice Genome Sequencing Project (IRGSP) genomic sequence. The TATR7, a degenerate tandem repeat which is interrupted by transposable elements, appeared on both ends of chromosome 7. The TATR10s was found to contain an inverted array of three tandem repeats displaying an interesting secondary folding pattern that resembles a telomere loop (t-loop) and which may be involved in a protective function against chromosomal end degradatio
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