9 research outputs found
Measurement of the B0→K∗0e+e− branching fraction at low dilepton mass
No full textThe branching fraction of the rare decay B 0 → K ∗0 e + e − in the dilepton mass region from 30 to 1000 MeV/c 2 has been measured by the LHCb experiment, using pp collision data, corresponding to an integrated luminosity of 1.0 fb−1, at a centre-of-mass energy of 7 TeV. The decay mode B 0 → J/ψ (e + e −)K ∗0 is utilized as a normalization channel. The branching fraction B(B0→K∗0e+e−) is measured to be B(B0→K∗0e+e−)30−1000MeV/c2 =(3.1+0.9−0.8+0.2−0.3±0.2)×10−7, where the first error is statistical, the second is systematic, and the third comes from the uncertainties on the B 0 → J/ψ K ∗0 and J/ψ → e + e − branching fractions
Measurement of the cross-section for Z → e<sup>+</sup>e<sup>-</sup> production in pp collisions at √<span style="text-decoration:overline">s</span>=7 TeV
No full textA measurement of the cross-section for pp → Z → e+e− is presented using data at s√=7 TeV corresponding to an integrated luminosity of 0.94 fb−1. The process is measured within the kinematic acceptance p T > 20 GeV/c and 2 < η < 4.5 for the daughter electrons and dielectron invariant mass in the range 60–120 GeV/c 2. The cross-section is determined to be σ(pp→Z→e+e−)=76.0±0.8±2.0±2.6pb where the first uncertainty is statistical, the second is systematic and the third is the uncertainty in the luminosity. The measurement is performed as a function of Z rapidity and as a function of an angular variable which is closely related to the Z transverse momentum. The results are compared with previous LHCb measurements and with theoretical predictions from QCD
Evidence for the two-body charmless baryonic decay
No full textSee paper for full list of authors - 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-2016-048.html - Submitted to JHEPInternational audienceA search for the rare two-body charmless baryonic decay is performed with collision data, corresponding to an integrated luminosity of 3\mbox{\,fb}^{-1}, collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. An excess of candidates with respect to background expectations is seen with a statistical significance of 4.1 standard deviations, and constitutes the first evidence for this decay. The branching fraction, measured using the decay for normalisation, is \begin{eqnarray} \mathcal{B}(B^+ \to p \bar\Lambda) & = & ( 2.4 \,^{+1.0}_{-0.8} \pm 0.3 ) \times 10^{-7} \,, \nonumber \end{eqnarray} where the first uncertainty is statistical and the second systematic
Observation of the decay Bc+→ψ(2S)π+
No full textThe decay Bc+→ψ(2S)π+ with ψ(2S)→μ+μ- is observed with a significance of 5.2σ using pp collision data corresponding to an integrated luminosity of 1.0 fb-1 collected by the LHCb experiment. The branching fraction of Bc+→ψ(2S)π+ decays relative to that of the Bc+→J/ψπ+ mode is measured to be B(Bc+→ψ(2S)π+)/B(Bc+→J/ψπ+)=0.250±0.068(stat)±0.014(syst)±0.006(B). The last term is the uncertainty on the ratio B(ψ(2S)→μ+μ-)/B(J/ψ→μ+μ-)
Measurement of the J/ψ pair production cross-section in pp collisions at √=13 TeV
No full textThe production cross-section of J/ψ pairs is measured using a data sample of pp collisions collected by the LHCb experiment at a centre-of-mass energy of s√=13 TeV, corresponding to an integrated luminosity of 279 ±11 pb−1. The measurement is performed for J/ψ mesons with a transverse momentum of less than 10 GeV/c in the rapidity range 2.0 < y <4.5. The production cross-section is measured to be 15.2 ± 1.0 ± 0.9 nb. The first uncertainty is statistical, and the second is systematic. The differential cross-sections as functions of several kinematic variables of the J/ψ pair are measured and compared to theoretical predictions
Measurement of the B ± production cross-section in pp collisions at √s=7 and 13 TeV
No full textThe production of B± mesons is studied in pp collisions at centre-of-mass energies of 7 and 13 TeV, using B± → J/ψ K± decays and data samples corresponding to 1.0 fb−1 and 0.3 fb−1, respectively. The production cross-sections summed over both charges and integrated over the transverse momentum range 0 < pT < 40 GeV/c and the rapidity range 2.0 < y < 4.5 are measured to beσ(pp→B±X,s=7TeV)=43.0±0.2±2.5±1.7μb,σ(pp→B±X,s=13TeV)=86.6±0.5±5.4±3.4μb,where the first uncertainties are statistical, the second are systematic, and the third are due to the limited knowledge of the B± → J/ψ K± branching fraction. The ratio of the cross-section at 13 TeV to that at 7 TeV is determined to be 2.02 ± 0.02 (stat) ± 0.12 (syst). Differential cross-sections are also reported as functions of pT and y. All results are in agreement with theoretical calculations based on the state-of-art fixed next-to-leading order quantum chromodynamics.[Figure not available: see fulltext.]
First measurement of the differential branching fraction and asymmetry of the decay
No full textThe differential branching fraction with respect to the dimuon invariant mass squared, and the asymmetry of the decay are measured for the first time. The CKM matrix elements and , and the ratio are determined. The analysis is performed using proton-proton collision data corresponding to an integrated luminosity of 3.0 fb, collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The total branching fraction and asymmetry of decays are measured to be \begin{eqnarray} \mathcal{B}(B^\pm\to\pi^\pm\mu^+\mu^-) = (1.83 \pm 0.24 \pm 0.05) \times 10^{-8}\,\,\,\mathrm{and} \nonumber\\ \mathcal{A}_{C\!P}(B^\pm\to\pi^\pm\mu^+\mu^-) = -0.11 \pm 0.12 \pm 0.01\,, \nonumber \end{eqnarray} where the first uncertainties are statistical and the second are systematic. These are the most precise measurements of these observables to date, and they are compatible with the predictions of the Standard Model
Observation of the decay B-s(0) -> (D)over-bar(0)phi
No full textFirst observation of the decay Bs0→D-0φ is reported using pp collision data, corresponding to an integrated luminosity of 1.0 fb-1, collected by the LHCb experiment at a centre-of-mass energy of 7TeV. The significance of the signal is 6.5 standard deviations. The branching fraction is measured relative to that of the decay Bs0→D-0K-*0 to beB(Bs0→D-0φ)B(Bs0→D-0K-*0)=0.069±0.013(stat)±0.007(syst). The first measurement of the ratio of branching fractions for the decays Bs0→D-0K-*0 and B0→D-0K*0 is found to beB(Bs0→D-0K-*0)B(B0→D-0K*0)=7.8±0.7(stat)±0.3(syst)±0.6(fs/fd), where the last uncertainty is due to the ratio of the Bs0 and B0 fragmentation fractions. © 2013 CERN
Observation of the decay B-s(0) -> (D)over-bar(0)phi
No full textFirst observation of the decay B-s(0) -> (D) over bar (0)phi is reported using pp collision data, corresponding to an integrated luminosity of 1.0 fb(-1), collected by the LHCb experiment at a centre-of-mass energy of 7 TeV. The significance of the signal is 6.5 standard deviations. The branching fraction is measured relative to that of the decay B-S(0) -> (D) over bar (0)phi to be beta B-S(0) -> (D) over bar (0)phi/beta B-S(0) -> (D) over bar (0)(K) over bar*(0) = 0.069 +/- 0.013 (stat) +/- 0.007 (syst). The first measurement of the ratio of branching fractions for the decays beta B-S(0) -> (D) over bar (0)(K) over bar*(0) and beta B-S(0) -> (D) over bar (0)(K) over bar*(0) is found to be beta B-S(0) -> (D) over bar (0)(K) over bar*(0/)beta B-S(0) -> (D) over bar (0)(K) over bar*(0=7.8) +/- 0.7(stat) +/- 0.3 (syst) +/- 0.6 (f(s)/f(d)) where the last uncertainty is due to the ratio of the B(s)(0)and B-0 fragmentation fractions
