The B0→K∗0K¯∗0\ {B}^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0} \ and Bs0→K∗0K¯∗0\ {B}_s^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0} \ decays are studied using proton-proton collision data corresponding to ...an integrated luminosity of 3 fb−1. An untagged and timeintegrated amplitude analysis of B(s)0 → (K+π−)(K−π+) decays in two-body invariant mass regions of 150 MeV/c2 around the K∗0 mass is performed. A stronger longitudinal polarisation fraction in the B0→K∗0K¯∗0\ {B}^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0} \ decay, fL = 0.724 ± 0.051 (stat) ± 0.016 (syst), is observed as compared to fL = 0.240 ± 0.031 (stat) ± 0.025 (syst) in the Bs0→K∗0K¯∗0\ {B}_s^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0} \ decay. The ratio of branching fractions of the two decays is measured and used to determine ℬB0→K∗0K¯∗0=8.0±0.9stat±0.4syst×10−7\ \mathrm{\mathcal{B}}\left({B}^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0}\right)=\left(8.0\pm 0.9\left(\mathrm{stat}\right)\pm 0.4\left(\mathrm{syst}\right)\right)\times {10}^{-7} \.
Using proton-proton collision data, corresponding to an integrated luminosity of 9 fb−1, collected with the LHCb detector between 2011 and 2018, a new narrow charmonium state, the X(3842) resonance, ...is observed in the decay modes X3842→D0D¯0\ \mathrm{X}(3842)\to {D}^0{\overline{D}}^0 \ and X(3842) → D+D−. The mass and the natural width of this state are measured to bemX3842=3842.71±0.16±0.12MeV/c2,ΓX3842=2.79±0.51±0.35MeV,\ \begin{array}{l}{m}_{X(3842)}=3842.71\pm 0.16\pm 0.12\ MeV/{c}^2,\hfill \\ {}{\varGamma}_{X(3842)}=2.79\pm 0.51\pm 0.35\ MeV,\hfill \end{array} \where the first uncertainty is statistical and the second is systematic. The observed mass and narrow natural width suggest the interpretation of the new state as the unobserved (spin-3 ψ3 13D3) charmonium state.In addition, prompt hadroproduction of the ψ(3770) and χ2(3930) states is observed for the first time, and the parameters of these states are measured to bemψ3770=3778.1±0.7±0.6MeV/c2,mχ23930=3921.9±0.6±0.2MeV/c2,Γχ23930=36.6±1.9±0.9MeV,\ \begin{array}{l}{m}_{\psi (3770)}=3778.1\pm 0.7\pm 0.6\ MeV/{c}^2,\hfill \\ {}{m}_{\chi_2(3930)}=3921.9\pm 0.6\pm 0.2\ MeV/{c}^2,\hfill \\ {}{\varGamma}_{\chi_2(3930)}=36.6 \pm 1.9 \pm 0.9\ MeV,\hfill \end{array} \where the first uncertainty is statistical and the second is systematic.
A measurement of the CP asymmetry in B(0)→K(*0)μ(+)μ(-) decays is presented, based on 1.0 fb(-1) of pp collision data recorded by the LHCb experiment during 2011. The measurement is performed in six ...bins of invariant mass squared of the μ(+)μ(-) pair, excluding the J/ψ and ψ(2S) resonance regions. Production and detection asymmetries are removed using the B(0)→J/ψK(*0) decay as a control mode. The integrated CP asymmetry is found to be -0.072±0.040(stat)±0.005(syst), consistent with the standard model.
A search for CP violation in the Cabibbo-suppressed D0 → K+K−π+π− decay mode is performed using an amplitude analysis. The measurement uses a sample of pp collisions recorded by the LHCb experiment ...during 2011 and 2012, corresponding to an integrated luminosity of 3.0 fb−1. The D0 mesons are reconstructed from semileptonic b-hadron decays into D0μ−X final states. The selected sample contains more than 160 000 signal decays, allowing the most precise amplitude modelling of this D0 decay to date. The obtained amplitude model is used to perform the search for CP violation. The result is compatible with CP symmetry, with a sensitivity ranging from 1% to 15% depending on the amplitude considered.
Charm production at the LHC in pp collisions at sqrt(s)=7 TeV is studied with the LHCb detector. The decays D0 -> K- pi+, D+ -> K- pi+ pi+, D*+ -> D0(K- pi+) pi+, D_s+ -> phi(K- K+) pi+, Lambda_c+ -> ...p K- pi+, and their charge conjugates are analysed in a data set corresponding to an integrated luminosity of 15 nb^{-1}. Differential cross-sections dsigma/dp_T are measured for prompt production of the five charmed hadron species in bins of transverse momentum and rapidity in the region 0 < p_T < 8 GeV/c and 2.0 < y < 4.5. Theoretical predictions are compared to the measured differential cross-sections. The integrated cross-sections of the charm hadrons are computed in the above p_T-y range, and their ratios are reported. A combination of the five integrated cross-section measurements gives sigma(c\bar{c})_{p_T < 8 GeV/c, 2.0 < y < 4.5} = 1419 +/- 12 (stat) +/- 116 (syst) +/- 65 (frag) microbarn, where the uncertainties are statistical, systematic, and due to the fragmentation functions.
Using proton-proton collision data, collected with the LHCb detector and corresponding to 1.0, 2.0 and 1.9 fb−1 of integrated luminosity at the centre-of-mass energies of 7, 8, and 13 TeV, ...respectively, the decay Λb0→χc1\ {\Lambda}_{\mathrm{b}}^0\to {\upchi}_{\mathrm{c}1} \(3872)pK− with χc1(3872) → J/ψ π+π− is observed for the first time. The significance of the observed signal is in excess of seven standard deviations. It is found that (58 ± 15)% of the decays proceed via the two-body intermediate state χc1(3872)Λ(1520). The branching fraction with respect to that of the Λb0\ {\Lambda}_{\mathrm{b}}^0 \ → ψ(2S)pK− decay mode, where the ψ(2S) meson is reconstructed in the J/ψ π+π− final state, is measured to be:βΛb0→χc13872pK−βΛb0→ψ2SpK−×βχc13872→J/ψπ+π−βψ2S→J/ψπ+π−=5.4±1.1±0.2×10−2,\ \frac{\beta \left({\Lambda}_{\mathrm{b}}^0\to {\upchi}_{\mathrm{c}1}(3872){\mathrm{pK}}^{-}\right)}{\beta \left({\Lambda}_{\mathrm{b}}^0\to \uppsi \left(2\mathrm{S}\right){\mathrm{pK}}^{-}\right)}\times \frac{\beta \left({\upchi}_{\mathrm{c}1}(3872)\to \mathrm{J}/\uppsi {\uppi}^{+}{\uppi}^{-}\right)}{\beta \left(\uppsi \left(2\mathrm{S}\right)\to \mathrm{J}/\uppsi {\uppi}^{+}{\uppi}^{-}\right)}=\left(5.4\pm 1.1\pm 0.2\right)\times {10}^{-2}, \where the first uncertainty is statistical and the second is systematic.
The $B^0_s$ and $B^0$ mixing frequencies, $\Delta m_s$ and $\Delta m_d$, are measured using a data sample corresponding to an integrated luminosity of 1.0 fb^{-1} collected by the LHCb experiment in ...$pp$ collisions at a centre of mass energy of 7 TeV during 2011. Around 1.8x10^6 candidate events are selected of the type $B^0_{(s)} \to D^-_{(s)} \mu^+$ (+ anything), where about half are from peaking and combinatorial backgrounds. To determine the B decay times, a correction is required for the momentum carried by missing particles, which is performed using a simulation-based statistical method. Associated production of muons or mesons allows us to tag the initial-state flavour and so to resolve oscillations due to mixing. We obtain \Delta m_s = (17.93 \pm 0.22 (stat) \pm 0.15 (syst)) ps^{-1}, \Delta m_d = (0.503 \pm 0.011 (stat) \pm 0.013 (syst)) ps^{-1}. The hypothesis of no oscillations is rejected by the equivalent of 5.8 standard deviations for $B^0_s$ and 13.0 standard deviations for $B^0$. This is the first observation of $B^0_s$ mixing to be made using only semileptonic decays.
Bottom baryons decaying to a J/\psi\ meson and a hyperon are reconstructed using 1.0 fb^{-1} of data collected in 2011 with the LHCb detector. Significant \Lambda_b^0 \rightarrow J/\psi \Lambda, ...\Xi_b^-\rightarrow J/\psi \Xi^- and \Omega_b^- \rightarrow J/\psi \Omega^- signals are observed and the corresponding masses are measured to be M(\Lambda_b^0) = 5619.53 \pm 0.13 (stat) \pm 0.45 (syst) MeV/c^2, M(\Xi_b^-) = 5795.8 \pm 0.9 (stat) \pm 0.4 (syst) MeV/c^2, M(\Omega_b^-) = 6046.0 \pm 2.2 (stat) \pm 0.5 (syst) MeV/c^2, while the differences with respect to the \Lambda_b^0 mass are M(\Xi_b^-)-M(\Lambda_b^0) = 176.2 \pm 0.9 (stat) \pm 0.1 (syst) MeV/c^2, M(\Omega_b^-)-M(\Lambda_b^0) = 426.4 \pm 2.2 (stat) \pm 0.4 (syst) MeV/c^2. These are the most precise mass measurements of the \Lambda_b^0, \Xi_b^- and \Omega_b^- baryons to date. Averaging the above \Lambda_b^0 mass measurement with that published by LHCb using 35 pb^{-1} of data collected in 2010 yields M(\Lambda_b^0) = 5619.44 \pm 0.13 (stat) \pm 0.38 (syst) MeV/c^2.
The $B^0$--$\bar B^0$ oscillation frequency $\Delta m_d$ is measured by the LHCb experiment using a dataset corresponding to an integrated luminosity of $1.0\,$fb$^{-1}$ of proton-proton collisions ...at $\sqrt{s} = 7\,$TeV, and is found to be $\Delta m_d = 0.5156 \pm 0.0051\,($stat.$) \pm 0.0033\,($syst.$)\,$ps$^{-1}$. The measurement is based on results from analyses of the decays $B^0 \to D^- \pi^+$ ($D^- \to K^+ \pi^- \pi^-$) and $B^0 \to J\ \psi K^{*0}$ ($J\ \psi \to \mu^+ \mu^-$, $K^{*0} \to K^+ \pi^-$) and their charge conjugated modes.
First evidence of the $B^0\to J/\psi\omega$ decay is found and the $B_{s}^0\to J/\psi\eta$ and $B_{s}^0\to J/\psi\eta^{\prime}$ decays are studied using a dataset corresponding to an integrated ...luminosity of 1.0 $\mathrm{fb}^{-1}$ collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of $\sqrt{s} = 7$ TeV. The branching fractions of these decays are measured relative to that of the $\mathrm{B}^0\to J/\psi\rho^0$ decay: $$\frac{Br(B^0\to J/\psi\omega)}{Br(B^0\to J/\psi\rho^0)} = 0.89 \pm0.19(stat)^{+0.07}_{-0.13}(syst)$$ $$\frac{Br(B^0_s\to J/\psi\eta)}{Br(B^0\to J/\psi\rho^0)} = 14.0 \pm 1.2(stat)^{+1.1}_{-1.5}(syst)^{+1.1}_{-1.0}(\frac{f_d}{f_s}),$$ $$\frac{Br(B^0_s\to J/\psi\eta^{\prime})}{Br(B^0\to J/\psi\rho^0)} = 12.7\pm1.1(stat)^{+0.5}_{-1.3}(syst)^{+1.0}_{-0.9}(\frac{f_d}{f_s}),$$ where the last uncertainty is due to the knowledge of $f_d/f_s$, the ratio of b-quark hadronization factors that accounts for the different production rate of $B^0$ and $B^0_s$ mesons. The ratio of the branching fractions of $B^0_s\to J/\psi\eta^{\prime}$ and $B^0_s\to J/\psi\eta$ decays is measured to be $$ \frac{Br(B^0_s\to J/\psi\eta^{\prime})}{Br(B^0_s\to J/\psi\eta)} = 0.90\pm0.09(stat)^{+0.06}_{-0.02}(syst).$$
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