Identification of charm jets at LHCb

The identification of charm jets is achieved at LHCb for data collected in 2015-2018 using a method based on the properties of displaced vertices reconstructed and matched with jets. The performance of this method is determined using a dijet calibration dataset recorded by the LHCb detector and selected such that the jets are unbiased in quantities used in the tagging algorithm. The charm-tagging efficiency is reported as a function of the transverse momentum of the jet. The measured efficiencies are compared to those obtained from simulation and found to be in good agreement

Study of Bc+ decays to charmonia and three light hadrons

Using proton-proton collision data, corresponding to an integrated luminosity of $9fb^{-1}$ collected with the LHCb detector, seven decay modes of the $B_c^+$ meson into a $J/\psi$ or $\psi(2S)$ meson and three charged hadrons, kaons or pions, are studied. The decays $B_c^+\rightarrow ( \psi(2S) \rightarrow J/\psi \pi^+ \pi^-)\pi^+$, $B_c^+\rightarrow \psi(2S)\pi^+\pi^+\pi^-$, $B_c^+\rightarrow J/\psi K^+\pi^+\pi^-$ and $B_c^+\rightarrow K^+K^+K^-$ are observed for the first time, and evidence for the $B_c^+\rightarrow \psi(2S)K^+K^-\pi^+$ decay is found, where $J/\psi$ and $\psi(2S)$ mesons are reconstructed in their dimuon decay modes. The ratios of branching fractions between the different $B_c^+$ decays are reported as well as the fractions of the decays proceeding via intermediate resonances. The results largely support the factorisation approach used for a theoretical description of the studied decays

Study of Bc+ decays to charmonia and three light hadrons

Using proton-proton collision data, corresponding to an integrated luminosity of $9fb^{-1}$ collected with the LHCb detector, seven decay modes of the $B_c^+$ meson into a $J/\psi$ or $\psi(2S)$ meson and three charged hadrons, kaons or pions, are studied. The decays $B_c^+\rightarrow ( \psi(2S) \rightarrow J/\psi \pi^+ \pi^-)\pi^+$, $B_c^+\rightarrow \psi(2S)\pi^+\pi^+\pi^-$, $B_c^+\rightarrow J/\psi K^+\pi^+\pi^-$ and $B_c^+\rightarrow K^+K^+K^-$ are observed for the first time, and evidence for the $B_c^+\rightarrow \psi(2S)K^+K^-\pi^+$ decay is found, where $J/\psi$ and $\psi(2S)$ mesons are reconstructed in their dimuon decay modes. The ratios of branching fractions between the different $B_c^+$ decays are reported as well as the fractions of the decays proceeding via intermediate resonances. The results largely support the factorisation approach used for a theoretical description of the studied decays

Constraints on the CKM angle γ from B ^± → Dh ^± decays using D → h ^± h′^∓ π ⁰ final states

Abstract A data sample collected with the LHCb detector corresponding to an integrated luminosity of 9 fb−1 is used to measure eleven CP violation observables in B±→ Dh± decays, where h is either a kaon or a pion. The neutral D meson decay is reconstructed in the three-body final states: K±π∓π0; π+π−π0; K+K−π0 and the suppressed π±K∓π0 combination. The mode where a large CP asymmetry is expected, B±→ [π±K∓π0]DK±, is observed with a significance greater than seven standard deviations. The ratio of the partial width of this mode relative to that of the favoured mode, B±→ [K±π∓π0]DK±, is RADS(K) = (1.27 ± 0.16 ± 0.02) × 10−2. Evidence for a large CP asymmetry is also seen: AADS(K) = −0.38 ± 0.12 ± 0.02. Constraints on the CKM angle γ are calculated from the eleven reported observables.</jats:p

Measurement of χ<inf>c1</inf>(3872) production in proton-proton collisions at √s = 8 and 13 TeV

The production cross-section of the $\chi_{c1}(3872)$ state relative to the $\psi(2S)$ meson is measured using proton-proton collision data collected with the LHCb experiment at centre-of-mass energies of $\sqrt{s}=8$ and 13 TeV, corresponding to integrated luminosities of 2.0 and 5.4 fb$^{-1}$, respectively. The two mesons are reconstructed in the $J/\psi\pi^{+}\pi^{-}$ final state. The ratios of the prompt and nonprompt $\chi_{c1}(3872)$ to $\psi(2S)$ production cross-sections are measured as a function of transverse momentum, $p_{\rm T}$, and rapidity, $y$, in the kinematic range $4 < p_{\rm T} < 20$ GeV/$c$ and $2.0 < y < 4.5$. The prompt ratio is found to increase with $p_{\rm T}$ independently of $y$. The double-differential cross-section ratio of $\chi_{c1}(3872)$ relative to $\psi(2S)$ mesons between 13 and 8 TeV is also measured for the prompt component and observed to be consistent with unity, independent of $p_{\rm T}$ and centre-of-mass energy

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