200 research outputs found
Calculation of two-loop virtual corrections to b --> s l+ l- in the standard model
We present in detail the calculation of the virtual O(alpha_s) corrections to
the inclusive semi-leptonic rare decay b --> s l+ l-. We also include those
O(alpha_s) bremsstrahlung contributions which cancel the infrared and mass
singularities showing up in the virtual corrections. In order to avoid large
resonant contributions, we restrict the invariant mass squared s of the lepton
pair to the range 0.05 < s/mb^2 < 0.25. The analytic results are represented as
expansions in the small parameters s/mb^2, z = mc^2/mb^2 and s/(4 mc^2). The
new contributions drastically reduce the renormalization scale dependence of
the decay spectrum. For the corresponding branching ratio (restricted to the
above s-range) the renormalization scale uncertainty gets reduced from +/-13%
to +/-6.5%.Comment: 41 pages including 9 postscript figures; in version 2 some typos and
inconsistent notation correcte
Phenomenology of non-standard Z couplings in exclusive semileptonic b -> s transitions
The rare decays , and
are analyzed in a generic scenario where New Physics effects
enter predominantly via penguin contributions. We show that this
possibility is well motivated on theoretical grounds, as the vertex
is particularly susceptible to non-standard dynamics. In addition, such a
framework is also interesting phenomenologically since the coupling
is rather poorly constrained by present data. The characteristic features of
this scenario for the relevant decay rates and distributions are investigated.
We emphasize that both sign and magnitude of the forward-backward asymmetry of
the decay leptons in , , carry sensitive information on New Physics. The observable is proposed as a useful probe of
non-standard CP violation in couplings.Comment: Minor modifications; version to appear in Phys. Rev.
Radiative and Semileptonic B Decays Involving Higher K-Resonances in the Final States
We study the radiative and semileptonic B decays involving a spin-
resonant with parity for and for
in the final state. Using the large energy effective theory (LEET)
techniques, we formulate transition form factors in the large
recoil region in terms of two independent LEET functions
and , the values of
which at zero momentum transfer are estimated in the BSW model. According to
the QCD counting rules, exhibit a dipole
dependence in . We predict the decay rates for ,
and . The
branching fractions for these decays with higher -resonances in the final
state are suppressed due to the smaller phase spaces and the smaller values of
. Furthermore, if the spin of
becomes larger, the branching fractions will be further suppressed due to the
smaller Clebsch-Gordan coefficients defined by the polarization tensors of the
. We also calculate the forward backward asymmetry of the decay, for which the zero is highly insensitive to the
-resonances in the LEET parametrization.Comment: 27 pages, 4 figures, 7 tables;contents and figures corrected, title
and references revise
Standard Model CP violation in Polarised b->d l^+ l^-
In the standard model, we study CP violating rate asymmetries in the decay
b->d l^+ l^- when one of the leptons is polarised. We find an asymmetry of (5
-- 15)% in the polarised decay spectrum which is comparable to known results
for the unpolarised case. In the kinematic region separating the rho-omega and
resonances, which is also theoretically cleanest, the polarised
contribution to the asymmetry is larger than the unpolarised results. In order
to observe a 3 sigma signal for direct CP violation in the polarised spectrum,
assuming 100% efficiency, about 10^10 pairs are required at a B
factory. Our results indicate an asymmetric contribution from the individual
polarisation states to the unpolarised CP asymmetry. Taking advantage of this,
one can attribute any new physics to be most sensitive to a specific
polarisation state.Comment: 23 pages, one reference adde
Research in Medical Education: Balancing Service and Science*
Since the latter part of the 1990’s, the English-speaking medical education community has been engaged in a debate concerning the types of research that should have priority. To shed light on this debate and to better understand its implications for the practice of research, 23 semi-structured interviews were conducted with “influential figures” from the community. The results were analyzed using the concept of “field” developed by the sociologist Pierre Bourdieu. The results reveal that a large majority of these influential figures believe that research in medical education continues to be of insufficient quality despite the progress that has taken place over the past 2 decades. According to this group, studies tend to be both redundant and opportunistic, and researchers tend to have limited understanding of both theory and methodological practice from the social sciences. Three factors were identified by the participants to explain the current problems in research: the working conditions of researchers, budgetary restraints in financing research in medical education, and the conception of research in the medical environment. Two principal means for improving research are presented: intensifying collaboration between PhD’s and clinicians, and encouraging the diversification of perspectives brought to bear on research in medical education
Outcome from balloon induced coronary artery dissection after intracoronary beta radiation
OBJECTIVE: To evaluate the healing of balloon induced coronary artery
dissection in individuals who have received beta radiation treatment and
to propose a new intravascular ultrasound (IVUS) dissection score to
facilitate the comparison of dissection through time. DESIGN:
Retrospective study. SETTING: Tertiary referral centre. PATIENTS: 31
patients with stable angina pectoris, enrolled in the beta energy
restenosis trial (BERT-1.5), were included. After excluding those who
underwent stent implantation, the evaluable population was 22 patients.
INTERVENTIONS: Balloon angioplasty and intracoronary radiation followed by
quantitative coronary angiography (QCA) and IVUS. Repeat QCA and IVUS were
performed at six month follow up. MAIN OUTCOME MEASURES: QCA and IVUS
evidence of healing of dissection. Dissection classification for
angiography was by the National Heart Lung Blood Institute scale. IVUS
proven dissection was defined as partial or complete. The following IVUS
defined characteristics of dissection were described in the affected
coronary segments: length, depth, arc circumference, presence of flap, and
dissection score. Dissection was defined as healed when all features of
dissection had resolved. The calculated dose of radiation received by the
dissected area in those with healed versus non-healed dissection was also
compared. RESULTS: Angiography (type A = 5, B = 7, C = 4) and IVUS proven
(partial = 12, complete = 4) dissections were seen in 16 patients
following intervention. At six month follow up, six and eight unhealed
dissections were seen by angiography (A = 2, B = 4) and IVUS (partial = 7,
complete = 1), respectively. The mean IVUS dissection score was 5.2 (range
3-8) following the procedure, and 4.6 (range 3-7) at follow up. No
correlation was found between the dose prescribed in the treated area and
the presence of unhealed disse
Exclusive semileptonic rare decays K,K^*) \ell^+ \ell^- in supersymmetric theories
The invariant mass spectrum, forward-backward asymmetry, and lepton
polarizations of the exclusive processes are analyzed under supersymmetric context. Special attention is paid to
the effects of neutral Higgs bosons (NHBs). Our analysis shows that the
branching ratio of the process \bkm can be quite largely modified by the
effects of neutral Higgs bosons and the forward-backward asymmetry would not
vanish. For the process \bksm, the lepton transverse polarization is quite
sensitive to the effects of NHBs, while the invariant mass spectrum,
forward-backward asymmetry, and lepton longitudinal polarization are not. For
both \bkt and \bkst, the effects of NHBs are quite significant. The partial
decay widths of these processes are also analyzed, and our analysis manifest
that even taking into account the theoretical uncertainties in calculating weak
form factors, the effects of NHBs could make SUSY shown up.Comment: Several references are added, typo are correcte
Understanding Business Travel Time and Its Place in the Working Day
This article argues that there is a need to understand business travel time in the context of the wider organization of work time. It considers why travel time use is potentially changing with the use of mobile technologies by the increasing number of individuals engaged in ‘knowledge work’, and examines existing evidence that indicates that travel time use is part of a wider work-related ‘taskscape’. However, it not only considers material productive output, but suggests that travel time as ‘time out’ from work-related activities also plays a vital role for employees. It also suggests that business travel time use that is not of benefit to the employer may not be at the employer's expense. This is contrasted with the assumptions used in UK transport appraisal. Data gathered from the autumn 2004 wave of the National Rail Passenger Survey (GB) is used to illustrate some key issues concerning productivity and ‘anti-activity’. A case study of an individual business traveller then points towards the need for a new approach to exploring the role played by travel time in the organization of work practices to be considered. © 2008, Sage Publications. All rights reserved
An Integrated TCGA Pan-Cancer Clinical Data Resource to Drive High-Quality Survival Outcome Analytics
For a decade, The Cancer Genome Atlas (TCGA) program collected clinicopathologic annotation data along with multi-platform molecular profiles of more than 11,000 human tumors across 33 different cancer types. TCGA clinical data contain key features representing the democratized nature of the data collection process. To ensure proper use of this large clinical dataset associated with genomic features, we developed a standardized dataset named the TCGA Pan-Cancer Clinical Data Resource (TCGA-CDR), which includes four major clinical outcome endpoints. In addition to detailing major challenges and statistical limitations encountered during the effort of integrating the acquired clinical data, we present a summary that includes endpoint usage recommendations for each cancer type. These TCGA-CDR findings appear to be consistent with cancer genomics studies independent of the TCGA effort and provide opportunities for investigating cancer biology using clinical correlates at an unprecedented scale. Analysis of clinicopathologic annotations for over 11,000 cancer patients in the TCGA program leads to the generation of TCGA Clinical Data Resource, which provides recommendations of clinical outcome endpoint usage for 33 cancer types
Radiative Decay Modes of the Meson
Using data recorded by the CLEO-II detector at CESR we have searched for four
radiative decay modes of the meson: ,
, , and . We
obtain 90% CL upper limits on the branching ratios of these modes of , , and
respectively.Comment: 15 page postscript file, postscript file also available through
http://w4.lns.cornell.edu/public/CLN
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