Searches for rare B-s(0) and B-0 decays into four muons

Searches for rare $B_s^0$ and $B^0$ decays into four muons are performed using proton-proton collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 $\text{fb}^{-1}$. Direct decays and decays via light scalar and $J/\psi$ resonances are considered. No evidence for the six decays searched for is found and upper limits at the 95% confidence level on their branching fractions ranging between $1.8\times10^{-10}$ and $2.6\times10^{-9}$ are set

Searches for rare B-s(0) and B-0 decays into four muons

Searches for rare $B_s^0$ and $B^0$ decays into four muons are performed using proton-proton collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 $\text{fb}^{-1}$. Direct decays and decays via light scalar and $J/\psi$ resonances are considered. No evidence for the six decays searched for is found and upper limits at the 95% confidence level on their branching fractions ranging between $1.8\times10^{-10}$ and $2.6\times10^{-9}$ are set.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2021-039.html (LHCb public pages

Measurement of chi(c1) (3872) production in proton-proton collisions at root s=8 and 13 TeV

Abstract The production cross-section of the χc1(3872) state relative to the ψ(2S) meson is measured using proton-proton collision data collected with the LHCb experiment at centre-of-mass energies of $$\sqrt{s}$$ s = 8 and 13 TeV, corresponding to integrated luminosities of 2.0 and 5.4 fb−1, respectively. The two mesons are reconstructed in the J/ψπ+π− final state. The ratios of the prompt and nonprompt χc1(3872) to ψ(2S) production cross-sections are measured as a function of transverse momentum, pT, and rapidity, y, of the χc1(3872) and ψ(2S) states, in the kinematic range 4 &lt; pT&lt; 20 GeV/c and 2.0 &lt; y &lt; 4.5. The prompt ratio is found to increase with pT, independently of y. For the prompt component, the double ratio of the χc1(3872) and ψ(2S) production cross-sections between 13 and 8 TeV is observed to be consistent with unity, independent of pT and centre-of-mass energy.</jats:p

Observation of the Decay Λb0 → Λc+τ−ν¯τ

The first observation of the semileptonic b -baryon decay Λ 0 b → Λ + c τ − ¯ ν τ , with a significance of 6.1 σ , is reported using a data sample corresponding to 3     fb − 1 of integrated luminosity, collected by the LHCb experiment at center-of-mass energies of 7 and 8 TeV at the LHC. The τ − lepton is reconstructed in the hadronic decay to three charged pions. The ratio K = B ( Λ 0 b → Λ + c τ − ¯ ν τ ) / B ( Λ 0 b → Λ + c π − π + π − ) is measured to be 2.46 ± 0.27 ± 0.40 , where the first uncertainty is statistical and the second systematic. The branching fraction B ( Λ 0 b → Λ + c τ − ¯ ν τ ) = ( 1.50 ± 0.16 ± 0.25 ± 0.23 ) % is obtained, where the third uncertainty is from the external branching fraction of the normalization channel Λ 0 b → Λ + c π − π + π − . The ratio of semileptonic branching fractions R ( Λ + c ) ≡ B ( Λ 0 b → Λ + c τ − ¯ ν τ ) / B ( Λ 0 b → Λ + c μ − ¯ ν μ ) is derived to be 0.242 ± 0.026 ± 0.040 ± 0.059 , where the external branching fraction uncertainty from the channel Λ 0 b → Λ + c μ − ¯ ν μ contributes to the last term. This result is in agreement with the standard model prediction