21 research outputs found
Patterns of New Physics in B Decays
We show that any new physics (NP) which affects B decays with penguin
contributions can be absorbed by redefinitions of the standard-model (SM)
diagrammatic amplitudes. Hence, there are no clean signals of NP in such decays
unless there is an accurate theoretical estimate of parameters or a justifiable
approximation can be made. In all decays with penguin contributions, NP
simultaneously affects pairs of diagrams. The evidence for a large C' from fits
to B-> pi K data is naturally explained if NP contributes to P_EW, since NP
affects the P_EW and C' diagrams as a pair. The weak phase gamma measured in
B-> pi K decays will always agree with its SM value even in the presence of NP,
if the NP contributes in such a way that the amplitudes retain the SM form
after suitable redefinitions.Comment: 4 pages, revtex, no figures; Several changes made to highlight
results obtaine
Direct CP Violation in K_L --> \pi^0 e^+e^- Beyond Leading Logarithms
We analyze the direct CP violation in the rare decay K_L --> Pi^0 e+e- with
QCD effects taken into account consistently in the next-to-leading order. We
calculate the two-loop mixing between the four-quark \Delta S=1 operators and
the operator Q_7V = (sd)_(V-A)(ee)_V in the NDR and HV renormalization schemes.
Using the known two-loop anomalous dimension matrix of the four-quark
operators, we find that the coefficient C_7V(\mu) depends only very weakly on
\mu, renormalization scheme and \Lambda_MSbar. The next-to-leading QCD
corrections enhance the direct CP violating contribution over its leading order
estimate so that it remains dominant in spite of the recent decrease of
|V_ub/V_cb| and |V_cb|. We expect typically BR(K_L --> \pi^0 e^+ e^-)_dir ~
6*10^(-12), although values as high as 10^(-11) are not yet excluded.Comment: 35 pages (with 9 PostScript figures available separately), Munich
Technical University preprint TUM-T31-60/94, Max-Planck Institute preprint
MPI-Ph/94-1
Distinguishing the Littlest Higgs model with T-parity from supersymmetry at the LHC using trileptons
We analyse hadronically quiet trilepton signatures in the T-parity conserving
Littlest Higgs model and in R-parity conserving supersymmetry at the Large
Hadron Collider. We identify the regions of the parameter space where such
signals can reveal the presence of these new physics models above the Standard
Model background and distinguish them from each other, even in a situation when
the mass spectrum of the Littlest Higgs model resembles the supersymmetric
pattern.Comment: 14 pages, 4 figures, Latex; v2: a few comments and references added,
typos corrected, conclusions unchanged, version to be published in Physics
Letters
Decay constants, semi-leptonic and non-leptonic decays in a Bethe-Salpeter Model
We evaluate the decay constants for the B and mesons and the form factors
for the semileptonic decays of the B meson to and mesons in a
Bethe-Salpeter model. From data we extract from and from decays. The form factors are then used to obtain non-leptonic
decay partial widths for and in the
factorization approximation.Comment: 15 Pages, 3 Postscript figures (available also from [email protected]
Weak Decays Beyond Leading Logarithms
We review the present status of QCD corrections to weak decays beyond the
leading logarithmic approximation including particle-antiparticle mixing and
rare and CP violating decays. After presenting the basic formalism for these
calculations we discuss in detail the effective hamiltonians for all decays for
which the next-to-leading corrections are known. Subsequently, we present the
phenomenological implications of these calculations. In particular we update
the values of various parameters and we incorporate new information on m_t in
view of the recent top quark discovery. One of the central issues in our review
are the theoretical uncertainties related to renormalization scale ambiguities
which are substantially reduced by including next-to-leading order corrections.
The impact of this theoretical improvement on the determination of the
Cabibbo-Kobayashi-Maskawa matrix is then illustrated in various cases.Comment: 229 pages, 32 PostScript figures (included); uses RevTeX, epsf.sty,
rotate.sty, rmpbib.sty (included), times.sty (included; requires LaTeX 2e);
complete PostScript version available at
ftp://feynman.t30.physik.tu-muenchen.de/pub/preprints/tum-100-95.ps.gz or
ftp://feynman.t30.physik.tu-muenchen.de/pub/preprints/tum-100-95.ps2.gz
(scaled down and rotated version to print two pages on one sheet of paper
B --> D(D^*) Form Factors in a Bethe-Salpeter model
We calculate the form factors for the semileptonic decays of the meson to
and mesons in a Bethe-Salpeter model. We show that our model is
consistent with the constraints of Heavy Quark Effective Theory (HQET) and we
extract the matrix elements that represent the corrections to the form
factors in HQET. With available data, we obtain =.Comment: 15 pages, 5 figure
Bs-Bs.bar Mixing, CP Violation and Extraction of CKM Phases from Untagged Bs Data Samples
A width difference of the order of 20\% has previously been predicted for the
two mass eigenstates of the meson. The dominant contributor to the width
difference is the transition, with final states common
to both and . All current experimental analyses fit the
time-dependences of flavor-specific -modes to a single exponential, which
essentially determines the average lifetime. We stress that the same data
sample allows even the measurement of the width difference. To see that, this
note reviews the time-dependent formulae for tagged decays, which involve
rapid oscillatory terms depending on . In untagged data samples the
rapid oscillatory terms cancel. Their time-evolutions depend only on the much
more slowly varying exponential falloffs. We discuss in detail the extraction
of the two widths, and identify the large (small) CP-even (-odd) rate with that
of the light (heavy) mass eigenstate. It is demonstrated that decay
length distributions of some \underline{untagged} modes, such as , can be used to extract the notoriously
difficult CKM unitarity triangle angle . Sizable CP violating effects
may be seen with such untagged data samples. Listing as an
observable allows for additional important standard model constraints. Within
the CKM model, the ratio involves no CKM parameters,
only a QCD uncertainty. Thus a measurement of would
predict , up to the QCD uncertainty. A large width
difference would automatically solve the puzzle of the number of charmed
hadrons per decay in favor of theory. We also derive an upper limit of . Further, we must abandon the notion of
branching fractions of , and instead consider , in analogy to the neutral kaons.Comment: 46 pages, revte
Gabapentin for chronic pelvic pain in women (GaPP2):a multicentre, randomised, double-blind, placebo-controlled trial
BackgroundChronic pelvic pain affects 2–24% of women worldwide and evidence for medical treatments is scarce. Gabapentin is effective in treating some chronic pain conditions. We aimed to measure the efficacy and safety of gabapentin in women with chronic pelvic pain and no obvious pelvic pathology.MethodsWe performed a multicentre, randomised, double-blind, placebo-controlled randomised trial in 39 UK hospital centres. Eligible participants were women with chronic pelvic pain (with or without dysmenorrhoea or dyspareunia) of at least 3 months duration. Inclusion criteria were 18–50 years of age, use or willingness to use contraception to avoid pregnancy, and no obvious pelvic pathology at laparoscopy, which must have taken place at least 2 weeks before consent but less than 36 months previously. Participants were randomly assigned in a 1:1 ratio to receive gabapentin (titrated to a maximum dose of 2700 mg daily) or matching placebo for 16 weeks. The online randomisation system minimised allocations by presence or absence of dysmenorrhoea, psychological distress, current use of hormonal contraceptives, and hospital centre. The appearance, route, and administration of the assigned intervention were identical in both groups. Patients, clinicians, and research staff were unaware of the trial group assignments throughout the trial. Participants were unmasked once they had provided all outcome data at week 16–17, or sooner if a serious adverse event requiring knowledge of the study drug occurred. The dual primary outcome measures were worst and average pain scores assessed separately on a numerical rating scale in weeks 13–16 after randomisation, in the intention-to-treat population. Self-reported adverse events were assessed according to intention-to-treat principles. This trial is registered with the ISRCTN registry, ISCRTN77451762.FindingsParticipants were screened between Nov 30, 2015, and March 6, 2019, and 306 were randomly assigned (153 to gabapentin and 153 to placebo). There were no significant between-group differences in both worst and average numerical rating scale (NRS) pain scores at 13–16 weeks after randomisation. The mean worst NRS pain score was 7·1 (standard deviation [SD] 2·6) in the gabapentin group and 7·4 (SD 2·2) in the placebo group. Mean change from baseline was −1·4 (SD 2·3) in the gabapentin group and −1·2 (SD 2·1) in the placebo group (adjusted mean difference −0·20 [97·5% CI −0·81 to 0·42]; p=0·47). The mean average NRS pain score was 4·3 (SD 2·3) in the gabapentin group and 4·5 (SD 2·2) in the placebo group. Mean change from baseline was −1·1 (SD 2·0) in the gabapentin group and −0·9 (SD 1·8) in the placebo group (adjusted mean difference −0·18 [97·5% CI −0·71 to 0·35]; p=0·45). More women had a serious adverse event in the gabapentin group than in the placebo group (10 [7%] of 153 in the gabapentin group compared with 3 [2%] of 153 in the placebo group; p=0·04). Dizziness, drowsiness, and visual disturbances were more common in the gabapentin group.InterpretationThis study was adequately powered, but treatment with gabapentin did not result in significantly lower pain scores in women with chronic pelvic pain, and was associated with higher rates of side-effects than placebo. Given the increasing reports of abuse and evidence of potential harms associated with gabapentin use, it is important that clinicians consider alternative treatment options to off-label gabapentin for the management of chronic pelvic pain and no obvious pelvic pathology.FundingNational Institute for Health Research
Prognostic model to predict postoperative acute kidney injury in patients undergoing major gastrointestinal surgery based on a national prospective observational cohort study.
Background: Acute illness, existing co-morbidities and surgical stress response can all contribute to postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery. The aim of this study was prospectively to develop a pragmatic prognostic model to stratify patients according to risk of developing AKI after major gastrointestinal surgery. Methods: This prospective multicentre cohort study included consecutive adults undergoing elective or emergency gastrointestinal resection, liver resection or stoma reversal in 2-week blocks over a continuous 3-month period. The primary outcome was the rate of AKI within 7 days of surgery. Bootstrap stability was used to select clinically plausible risk factors into the model. Internal model validation was carried out by bootstrap validation. Results: A total of 4544 patients were included across 173 centres in the UK and Ireland. The overall rate of AKI was 14·2 per cent (646 of 4544) and the 30-day mortality rate was 1·8 per cent (84 of 4544). Stage 1 AKI was significantly associated with 30-day mortality (unadjusted odds ratio 7·61, 95 per cent c.i. 4·49 to 12·90; P < 0·001), with increasing odds of death with each AKI stage. Six variables were selected for inclusion in the prognostic model: age, sex, ASA grade, preoperative estimated glomerular filtration rate, planned open surgery and preoperative use of either an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. Internal validation demonstrated good model discrimination (c-statistic 0·65). Discussion: Following major gastrointestinal surgery, AKI occurred in one in seven patients. This preoperative prognostic model identified patients at high risk of postoperative AKI. Validation in an independent data set is required to ensure generalizability