251 research outputs found
Measurement of ϒ production in pp collisions at √s = 2.76 TeV
The production of ϒ(1S), ϒ(2S) and ϒ(3S)
mesons decaying into the dimuon final state is studied with
the LHCb detector using a data sample corresponding to an
integrated luminosity of 3.3 pb−1 collected in proton–proton
collisions at a centre-of-mass energy of √s = 2.76 TeV. The
differential production cross-sections times dimuon branching
fractions are measured as functions of the ϒ transverse
momentum and rapidity, over the ranges pT < 15 GeV/c
and 2.0 < y < 4.5. The total cross-sections in this kinematic
region, assuming unpolarised production, are measured to be
σ (pp → ϒ(1S)X) × B
ϒ(1S)→μ+μ−
= 1.111 ± 0.043 ± 0.044 nb,
σ (pp → ϒ(2S)X) × B
ϒ(2S)→μ+μ−
= 0.264 ± 0.023 ± 0.011 nb,
σ (pp → ϒ(3S)X) × B
ϒ(3S)→μ+μ−
= 0.159 ± 0.020 ± 0.007 nb,
where the first uncertainty is statistical and the second systematic
Study of D-(*())(+)(sJ) mesons decaying to D*K-+(S)0 and D*K-0(+) final states
A search is performed for mesons in the reactions and using data collected at
centre-of-mass energies of 7 and 8 TeV with the LHCb detector. For the final state, the decays with and are used. For , the
decay with is used. A prominent
signal is observed in both and final states. The resonances and are
also observed, yielding information on their properties, including spin-parity
assignments. The decay is observed
for the first time, at a significance of 6.9 , and its branching
fraction relative to the decay mode is
measured
Search for Violations of Lorentz Invariance and CPT Symmetry in B-(s)(0) Mixing
Violations of CPT symmetry and Lorentz invariance are searched for by studying interference effects in B^{0} mixing and in B_{s}^{0} mixing. Samples of B^{0}→J/ψK_{S}^{0} and B_{s}^{0}→J/ψK^{+}K^{-} decays are recorded by the LHCb detector in proton-proton collisions at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb^{-1}. No periodic variations of the particle-antiparticle mass differences are found, consistent with Lorentz invariance and CPT symmetry. Results are expressed in terms of the standard model extension parameter Δa_{μ} with precisions of O(10^{-15}) and O(10^{-14}) GeV for the B^{0} and B_{s}^{0} systems, respectively. With no assumption on Lorentz (non)invariance, the CPT-violating parameter z in the B_{s}^{0} system is measured for the first time and found to be Re(z)=-0.022±0.033±0.005 and Im(z)=0.004±0.011±0.002, where the first uncertainties are statistical and the second systematic
Study of the doubly charmed tetraquark T+cc
Quantum chromodynamics, the theory of the strong force, describes interactions of coloured quarks and gluons and the formation of hadronic matter. Conventional hadronic matter consists of baryons and mesons made of three quarks and quark-antiquark pairs, respectively. Particles with an alternative quark content are known as exotic states. Here a study is reported of an exotic narrow state in the D0D0π+ mass spectrum just below the D*+D0 mass threshold produced in proton-proton collisions collected with the LHCb detector at the Large Hadron Collider. The state is consistent with the ground isoscalar T+cc tetraquark with a quark content of ccu⎯⎯⎯d⎯⎯⎯ and spin-parity quantum numbers JP = 1+. Study of the DD mass spectra disfavours interpretation of the resonance as the isovector state. The decay structure via intermediate off-shell D*+ mesons is consistent with the observed D0π+ mass distribution. To analyse the mass of the resonance and its coupling to the D*D system, a dedicated model is developed under the assumption of an isoscalar axial-vector T+cc state decaying to the D*D channel. Using this model, resonance parameters including the pole position, scattering length, effective range and compositeness are determined to reveal important information about the nature of the T+cc state. In addition, an unexpected dependence of the production rate on track multiplicity is observed
Effect of metformin on clinical-pathological variables in women with endometrial cancer. A multicenter study
Objective: Endometrial cancer (EC) is the most common gynecological
malignancy in economically developed countries. Documented risk factors
include diabetes mellitus and obesity. Metformin, a derivative of
biguanide, applied in treatment of type 2 diabetes, also has
anti-neoplastic effects. The analysis presented below represents an
attempt to determine the effects of metformin on clinical-pathological
variables of EC, linked to the morbidity and course of EC. Material and
Methods: 1,305 patients with EC were included in this retrospective
study, the control group consisted of 1,016 EC patients who were
diabetes-free. 144 patients with EC and type 2 diabetes treated with
metformin, and 145 patients with EC and type 2 diabetes treated with
other antidiabetic agents. The analyzed variables included age upon
diagnosis of EC, BMI, parity, clinical stage according to FIGO,
histological type of cancer (type I or type II EC), grading, type of
surgery, adjuvant treatment (radio- or chemotherapy), and comorbidities.
Results: EC in females with type 2 diabetes treated with metformin or
other antidiabetic agents were diagnosed at a more advanced age than
those in the control group. Both groups of patients with type 2 diabetes
manifested morbid obesity significantly more frequently than the control
group. Advanced stages of cancer were detected less frequently among
metformin users compared to the control group and among patients with
diabetes treated with other antidiabetic agents. Moreover, in the
metformin group, total abdominal hysterectomy and adnexectomy were less
common than in the remaining groups. Adjuvant radiotherapy was applied
more frequently in the metformin-treated group. Both groups of type 2
diabetes patients were also more likely to suffer from hypertension.
Conclusion: Compared to the control group, women with EC and diabetes
mellitus were diagnosed at a more advanced age. A lower percentage of
women with EC using metformin were diagnosed at advanced stages of EC
according to FIGO in contrast to the control group and the group with
diabetes treated with other antidiabetic agents. Patients treated with
metformin underwent TAHBSO less frequently, but radiotherapy was applied
more often. The present results show that type 2 diabetes patients also
suffer from hypertension more frequently regardless of the diabetes
treatment applied
First study of the CP-violating phase and decay-width difference in Bs 0→ψ(2S)ϕ decays
A time-dependent angular analysis of Bs 0→ψ(2S)ϕ decays is performed using data recorded by the LHCb experiment. The data set corresponds to an integrated luminosity of 3.0fb−1 collected during Run 1 of the LHC. The CP-violating phase and decay-width difference of the Bs 0 system are measured to be ϕs=0.23−0.28 +0.29±0.02rad and ΔΓs=0.066−0.044 +0.041±0.007ps−1, respectively, where the first uncertainty is statistical and the second systematic. This is the first time that ϕs and ΔΓs have been measured in a decay containing the ψ(2S) resonance. © 2016 The Author(s
Observation of Lambda(0)(b) -> psi (2S)pK(-) and Lambda(0)(b) -> J/psi pi(+)pi(-)pK(-) decays and a measurement of the A(b)(0) baryon mass
The decays Lambda(0)(b) -> psi(2S)pK(-) and Lambda(0)(b) -> J/psi
pi(+)pi(-)pK(-) are observed in a data sample corresponding to an
integrated luminosity of 3 fb(-1), collected in proton-proton collisions
at 7 and 8 TeV centre-of-mass energies by the LHCb detector. The psi(2S)
mesons are reconstructed through the decay modes psi(2S) -> mu(+)mu(-)
and psi(2S) -> J/psi pi(+)pi(-) The branching fractions relative to that
of Lambda(0)(b) -> J/psi pk(-) are measured to be
[GRAPHICS]
where the first uncertainties are statistical, the second are systematic
and the third is related to the knowledge of J/psi and psi(2S) branching
fractions. The mass of the Ai baryon is measured to be
M(Lambda(0)(b)) = 5619.65 +/- 0.17 0.17 MeV/c(2),
where the uncertainties are statistical and systematic
Measurement of the B-s(0) -> D-s(()*D-)+(s)(*()-) branching fractions
The branching fraction of the decay B-s(0) -> D-s(()*D-)+(s)(*()-)
is measured using pp collision data corresponding to an integrated
luminosity of 1.0 fb(-1), collected using the LHCb detector at a
center-of-mass energy of 7 TeV. It is found to be B(B-s(0) ->
D-s(()*D-)(s)(*()-)) = (3.05 +/- 0.10 +/- 0.20 +/- 0.34) where
the uncertainties are statistical, systematic, and due to the
normalization channel, respectively. The branching fractions of the
individual decays corresponding to the presence of one or two
D-s(*+/-) are also measured. The individual branching fractions are
found to be B(B-s(0) -> D-s*D-+/-(s)-/+) = (1.35 +/- 0.06 +/- 0.09 +/-
0.15) B(B-s(0) -> D-s*D-+(s)*(-)) = (1.27 +/- 0.08 +/- 0.10 +/-
0.14)%. All three results are the most precise determinations to date
First observation of the rare B+ -> D+K+pi(-) decay
The B+ -> D+K+pi(-) decay is observed in a data sample corresponding to
3.0 fb(-1) of pp collision data recorded by the LHCb experiment during
2011 and 2012. The signal significance is 8 sigma and the branching
fraction is measured to be B(B+ -> D+K+pi(-)) = (5.31 +/- 0.90 +/- 0.48
+/- 0.35) x 10(-6), where the uncertainties are statistical, systematic
and due to the normalization mode B+ -> D-K+pi(+), respectively. The
Dalitz plot appears to be dominated by broad structures. Angular
distributions are exploited to search for quasi-two-body contributions
from B+ -> D*(2)(2460)K-0(+) and B+ -> (D+K*)(892)(0) decays. No
significant signals are observed and upper limits are set on their
branching fractions
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