63 research outputs found
Measurement of polarization amplitudes and CP asymmetries in B-0 -> phi K*(892)(0)
An angular analysis of the decay B (0) -> phi K (*)(892)(0) is reported based on a pp collision data sample, corresponding to an integrated luminosity of 1.0 fb(-1), collected at a centre-of-mass energy of root S = 7 TeV with the LHCb detector. The P-wave amplitudes and phases are measured with a greater precision than by previous experiments, and confirm about equal amounts of longitudinal and transverse polarization. The S-wave K+ pi(-) and K+ K- contributions are taken into account and found to be significant. A comparison of the B (0) -> phi K (*)(892)(0) and results shows no evidence for direct CP violation in the rate asymmetry, in the triple-product asymmetries or in the polarization amplitudes and phases
Measurement of forward top pair production in the dilepton channel in <i>pp</i> collisions at âs=13 TeV
Forward top quark pair production is studied in collisions in the final state using a data sample corresponding to an integrated luminosity
of 1.93 fb collected with the LHCb experiment at a centre-of-mass energy
of 13 TeV. The cross-section is measured in a fiducial region where both
leptons have a transverse momentum greater than 20 GeV and a pseudorapidity
between 2.0 and 4.5. The quadrature sum of the azimuthal separation and the
difference in pseudorapidities, denoted , between the two leptons
must be larger than 0.1. The -jet axis is required to be separated from both
leptons by a of 0.5, and to have a transverse momentum in excess of
20 GeV and a pseudorapidity between 2.2 and 4.2. The cross-section is measured
to be where the first uncertainty is statistical, the second is systematic, and
the third is due to the luminosity determination. The measurement is compatible
with the Standard Model prediction.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2017-050.htm
Intraperitoneal drain placement and outcomes after elective colorectal surgery: international matched, prospective, cohort study
Despite current guidelines, intraperitoneal drain placement after elective colorectal surgery remains widespread. Drains were not associated with earlier detection of intraperitoneal collections, but were associated with prolonged hospital stay and increased risk of surgical-site infections.Background Many surgeons routinely place intraperitoneal drains after elective colorectal surgery. However, enhanced recovery after surgery guidelines recommend against their routine use owing to a lack of clear clinical benefit. This study aimed to describe international variation in intraperitoneal drain placement and the safety of this practice. Methods COMPASS (COMPlicAted intra-abdominal collectionS after colorectal Surgery) was a prospective, international, cohort study which enrolled consecutive adults undergoing elective colorectal surgery (February to March 2020). The primary outcome was the rate of intraperitoneal drain placement. Secondary outcomes included: rate and time to diagnosis of postoperative intraperitoneal collections; rate of surgical site infections (SSIs); time to discharge; and 30-day major postoperative complications (Clavien-Dindo grade at least III). After propensity score matching, multivariable logistic regression and Cox proportional hazards regression were used to estimate the independent association of the secondary outcomes with drain placement. Results Overall, 1805 patients from 22 countries were included (798 women, 44.2 per cent; median age 67.0 years). The drain insertion rate was 51.9 per cent (937 patients). After matching, drains were not associated with reduced rates (odds ratio (OR) 1.33, 95 per cent c.i. 0.79 to 2.23; P = 0.287) or earlier detection (hazard ratio (HR) 0.87, 0.33 to 2.31; P = 0.780) of collections. Although not associated with worse major postoperative complications (OR 1.09, 0.68 to 1.75; P = 0.709), drains were associated with delayed hospital discharge (HR 0.58, 0.52 to 0.66; P < 0.001) and an increased risk of SSIs (OR 2.47, 1.50 to 4.05; P < 0.001). Conclusion Intraperitoneal drain placement after elective colorectal surgery is not associated with earlier detection of postoperative collections, but prolongs hospital stay and increases SSI risk
Measurement of indirect CP asymmetries in D-0 -> K-K+ and D-0 -> pi(-)pi(+) decays using semileptonic B decays
Time-dependent asymmetries in the decay rates of the singly
Cabibbo-suppressed decays and are measured in collision data corresponding to an integrated
luminosity of 3.0 fb collected by the LHCb experiment. The mesons
are produced in semileptonic -hadron decays, where the charge of the
accompanying muon is used to determine the initial state as or
. The asymmetries in effective lifetimes between and
decays, which are sensitive to indirect violation, are
determined to be \begin{align*}
A_{\Gamma}(K^-K^+) = (-0.134 \pm 0.077 \; {}^{+0.026}_{-0.034})\% \,
A_{\Gamma}(\pi^-\pi^+) = (-0.092\pm 0.145 \; {}^{+0.025}_{-0.033})\% \,
\end{align*} where the first uncertainties are statistical and the second
systematic. This result is in agreement with previous measurements and with the
hypothesis of no indirect violation in decays.Comment: 20 pages, 4 figure
Study of eta-eta ' mixing from measurement of B-(s)(0) -> J/psi eta((')) decay rates
A study of B and Bs meson decays into J/Ï Î· and J/Ï Î·âČ final states is performed using a data set of proton-proton collisions at centre-of-mass energies of 7 and 8 TeV, collected by the LCHb experiment and corresponding to 3.0 fbâ1 of integrated luminosity. The decay B0 â J/Ï Î·âČ is observed for the first time. The following ratios of branching fractions are measured:
B(B0âJ/ÏηâČ)B(B0sâ J/ÏηâČ)=(2.28±0.65 (stat)±0.10 (syst)±0.13 (fs/fd))Ă10â2,B(B0â J/Ïη)B(B0sâ J/Ïη)=(1.85±0.61 (stat)±0.09 (syst)±0.11 (fs/fd))Ă10â2, where the third uncertainty is related to the present knowledge of fs/fd, the ratio between the probabilities for a b quark to form a Bs or a B0 meson. The branching fraction ratios are used to determine the parameters of η â ηâČ meson mixing. In addition, the first evidence for the decay Bs â Ï(2S)ηâČ is reported, and the relative branching fraction is measured,
B(B0sâ Ï(2S)ηâČ)B(B0sâ J/ÏηâČ)=(38.7±9.0 (stat)±1.3 (syst)±0.9(B))Ă10â2, where the third uncertainty is due to the limited knowledge of the branching fractions of J/Ï and Ï(2S) mesons
Search for long-lived particles decaying to jet pairs
A search is presented for long-lived particles with a mass between 25 and 50
GeV and a lifetime between 1 and 200 ps in a sample of proton-proton
collisions at a centre-of-mass energy of TeV, corresponding to an
integrated luminosity of 0.62 fb, collected by the LHCb detector. The
particles are assumed to be pair-produced by the decay of a Standard Model-like
Higgs boson. The experimental signature of the long-lived particle is a
displaced vertex with two associated jets. No excess above the background is
observed and limits are set on the production cross-section as a function of
the long-lived particle mass and lifetime
Search for the lepton flavour violating decay Ï â â ÎŒ â ÎŒ + ÎŒ â
A search for the lepton flavour violating decay
is performed with the LHCb experiment. The data sample corresponds to an
integrated luminosity of of proton-proton collisions at
a centre-of-mass energy of and
at . No evidence is found
for a signal, and a limit is set at confidence level on the branching
fraction, .Comment: 20 pages, 10 figures, published as JHEP 02 (2015) 12
Search for decays of neutral beauty mesons into four muons
A search for the non-resonant decays and is presented. The measurement is performed using
the full Run 1 data set collected in proton-proton collisions by the LHCb
experiment at the LHC. The data correspond to integrated luminosities of
and collected at centre-of-mass energies of and
, respectively. No signal is observed and upper limits on the
branching fractions of the non-resonant decays at confidence level are
determined to be
\mathcal{B}(B^0_s \rightarrow \mu^{+}\mu^{-}\mu^{+}\mu^{-}) & < 2.5 \times
10^{-9}
\mathcal{B}(B^0 \rightarrow \mu^{+}\mu^{-}\mu^{+}\mu^{-}) & < 6.9 \times
10^{-10}.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2016-043.htm
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