1,721,614 research outputs found
Bottomonium spectroscopy at BaBar and Belle
No full textWe present the results of the BABAR and Belle experiments on bottomonium spectroscopy and
decay. We discuss the observation of the bottomonium ground state ηb, the observation of the
inclusive Υ(1S) decay to open charm and the search for exotic bb ̄ resonances above the Υ(4S)
{Search for CP violation in the phase space of decays with the energy test}
No full textA search for CP violation in D0→KS0K+π− and D0→KS0K−π+ decays is reported. The search is performed using an unbinned model-independent method known as the energy test that probes local CP violation in the phase space of the decays. The data analysed correspond to an integrated luminosity of 5.4 fb−1 collected in proton-proton collisions by the LHCb experiment at a centre-of-mass energy of s = 13 TeV, amounting to approximately 950 thousand and 620 thousand signal candidates for the D0→KS0K−π+ and D0→KS0K+π− modes, respectively. The method is validated using D0 → K−π+π−π+ and D0→KS0π+π− decays, where CP-violating effects are expected to be negligible, and using background-enhanced regions of the signal decays. The results are consistent with CP symmetry in both the D0→KS0K−π+ and the D0→KS0K+π− decays, with p-values for the hypothesis of no CP violation of 70% and 66%, respectively
Measurement of J/ψ-pair production in pp collisions at √s = 13 TeV and study of gluon transverse-momentum dependent PDFs
Full text linkThe production cross-section of J/ψ pairs in proton-proton collisions at a centre-of-mass energy of s = 13 TeV is measured using a data sample corresponding to an integrated luminosity of 4.2 fb−1 collected by the LHCb experiment. The measurement is performed with both J/ψ mesons in the transverse momentum range 0 < pT< 14 GeV/c and rapidity range 2.0 < y < 4.5. The cross-section of this process is measured to be 16.36 ± 0.28 (stat) ± 0.88 (syst) nb. The contributions from single-parton scattering and double-parton scattering are separated based on the dependence of the cross-section on the absolute rapidity difference ∆y between the two J/ψ mesons. The effective cross-section of double-parton scattering is measured to be σeff = 13.1 ± 1.8 (stat) ± 2.3 (syst) mb. The distribution of the azimuthal angle φCS of one of the J/ψ mesons in the Collins-Soper frame and the pT-spectrum of the J/ψ pairs are also measured for the study of the gluon transverse-momentum dependent distributions inside protons. The extracted values of ⟨cos 2φCS⟩ and ⟨cos 4φCS⟩ are consistent with zero, but the presence of azimuthal asymmetry at a few percent level is allowed
A measurement of ∆Γs
Full text linkUsing a dataset corresponding to 9 fb−1 of integrated luminosity collected with the LHCb detector between 2011 and 2018 in proton-proton collisions, the decay-time distributions of the decay modes Bs0→J/ψη′ and Bs0→J/ψπ+π− are studied. The decay-width difference between the light and heavy mass eigenstates of the Bs0 meson is measured to be ∆Γs = 0.087 ± 0.012 ± 0.009 ps−1, where the first uncertainty is statistical and the second systematic
Measurement of the Z boson production cross-section in pp collisions at s = 5.02 TeV
Full text linkThe first measurement of the Z boson production cross-section at centre-of-mass energy s = 5.02 TeV in the forward region is reported, using pp collision data collected by the LHCb experiment in year 2017, corresponding to an integrated luminosity of 100 ± 2 pb−1. The production cross-section is measured for final-state muons in the pseudorapidity range 2.0 20 GeV/c. The integrated cross-section is determined to be (Formula presented.) for the di-muon invariant mass in the range 60 < Mμμ< 120 GeV/c2. This result and the differential cross-section results are in good agreement with theoretical predictions at next-to-next-to-leading order in the strong coupling constant. Based on a previous LHCb measurement of the Z boson production cross-section in pPb collisions at sNN = 5.02 TeV, the nuclear modification factor RpPb is measured for the first time at this energy. The measured values are 1.2−0.3+0.5 (stat) ± 0.1(syst) in the forward region (1.53 < 4.03) and 3.6−0.9+1.6 (stat) ± 0.2(syst) in the backward region (−4.97 < −2.47), where yμ∗ represents the muon rapidity in the centre-of-mass frame. (Figure presented.
A search for rare B → Dμ+μ− decays
Full text linkA search for rare B → Dμ+μ− decays is performed using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb−1. No significant signals are observed in the non-resonant μ+μ− modes, and upper limits of BB0→D ̄0μ+μ−<5.1×10−8, BB+→Ds+μ+μ−<3.2×10−8, BBs0→D ̄0μ+μ−<1.6×10−7 and fc/fu·BBc+→Ds+μ+μ−<9.6×10−8 are set at the 95 % confidence level, where fc and fu are the fragmentation fractions of a B meson with a c and u quark respectively in proton-proton collisions. Each result is either the first such measurement or an improvement by three orders of magnitude on an existing limit. Separate upper limits are calculated when the muon pair originates from a J/ψ → μ+μ− decay. The branching fraction of Bc+→Ds+J/ψ multiplied by the fragmentation-fraction ratio is measured to be (Formula presented.) where the first uncertainty is statistical and the second systematic
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