The production of prompt D0 mesons in proton-lead collisions in both the forward and backward rapidity regions at a center-of-mass energy per nucleon pair of √sNN=8.16 TeV is measured by the LHCb experiment. The nuclear modification factor of prompt D0 mesons is determined as a function of the transverse momentum pT, and the rapidity in the nucleon-nucleon center-of-mass frame y∗. In the forward rapidity region, significantly suppressed production with respect to pp collisions is measured, which provides significant constraints on models of nuclear parton distributions and hadron production down to the very low Bjorken-x region of ∼10−5. In the backward rapidity region, a suppression with a significance of 2.0–3.8 standard deviations compared to parton distribution functions in a nuclear environment expectations is found in the kinematic region of pT>6 GeV/c and −3.25

Tests of lepton universality in B^{0}→K_{S}^{0}ℓ^{+}ℓ^{-} and B^{+}→K^{*+}ℓ^{+}ℓ^{-} decays where ℓ is either an electron or a muon are presented. The differential branching fractions of B^{0}→K_{S}^{0}e^{+}e^{-} and B^{+}→K^{*+}e^{+}e^{-} decays are measured in intervals of the dilepton invariant mass squared. The measurements are performed using proton-proton collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 fb^{-1} . The results are consistent with the standard model and previous tests of lepton universality in related decay modes. The first observation of B^{0}→K_{S}^{0}e^{+}e^{-} and B^{+}→K^{*+}e^{+}e^{-} decays is reported.

An improved measurement of the decay B0s→μ+μ− and searches for the decays B0→μ+μ− and B0s→μ+μ−γ are performed at the LHCb experiment using data collected in proton-proton collisions at √s=7, 8 and 13 TeV, corresponding to integrated luminosities of 1, 2 and 6 fb−1, respectively. The B0s→μ+μ− branching fraction and effective lifetime are measured to be B(B0s→μ+μ−)=(3.09+0.46+0.15−0.43−0.11)×10−9 and τ(B0s→μ+μ−)=(2.07±0.29±0.03) ps, respectively, where the uncertainties include both statistical and systematic contributions. No significant signal for B0→μ+μ− and B0s→μ+μ−γ decays is found and the upper limits B(B0→μ+μ−)<2.6×10−10 and B(B0s→μ+μ−γ)<2.0×10−9 at 95% confidence level are determined, where the latter is limited to the range mμμ>4.9 GeV/c2. Additionally, the ratio between the B0→μ+μ− and B0s→μ+μ− branching fractions is measured to be Rμ+μ−<0.095 at 95% confidence level. The results are in agreement with the Standard Model predictions.10 MoreReceived 23 August 2021Accepted 8 December 2021DOI:https://doi.org/10.1103/PhysRevD.105.012010Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.© 2022 CERN, for the LHCb CollaborationPhysics Subject Headings (PhySH)Research AreasBranching fractionFlavor changing neutral currentsRare decaysPhysical SystemsBottom mesonsParticles & Fields

The first full angular analysis and an updated measurement of the decay-rate CP asymmetry of the D^{0}→π^{+}π^{-}μ^{+}μ^{-} and D^{0}→K^{+}K^{-}μ^{+}μ^{-} decays are reported. The analysis uses proton-proton collision data collected with the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV. The dataset corresponds to an integrated luminosity of 9 fb^{-1}. The full set of CP -averaged angular observables and their CP asymmetries are measured as a function of the dimuon invariant mass. The results are consistent with expectations from the standard model and with CP symmetry.

An amplitude analysis of flavor-untagged B_{s}^{0}→J/ψpp[over ¯] decays is performed using a sample of 797±31 decays reconstructed with the LHCb detector. The data, collected in proton-proton collisions between 2011 and 2018, correspond to an integrated luminosity of 9 fb^{-1}. Evidence for a new structure in the J/ψp and J/ψp[over ¯] systems with a mass of 4337_{-4}^{+7} _{-2}^{+2} MeV and a width of 29_{-12}^{+26} _{-14}^{+14} MeV is found, where the first uncertainty is statistical and the second systematic, with a significance in the range of 3.1 to 3.7σ, depending on the assigned J^{P} hypothesis.

The first observations of $B^0\rightarrow\overline{D}^{*}(2007)^{0}K^{+}\pi^{-}$ and $B_s^0\rightarrow\overline{D}^{*}(2007)^{0}K^{-}\pi^{+}$ decays are presented, and their branching fractions relative to that of the $B^0\rightarrow\overline{D}^{*}(2007)^{0}\pi^{+}\pi^{-}$ decay are reported. These modes can potentially be used to investigate the spectroscopy of charm and charm-strange resonances and to determine the angle $\gamma$ of the CKM unitarity triangle. It is also important to understand them as a source of potential background in determinations of $\gamma$ from $B^{+}\rightarrow DK^{+}$ and $B^{0}\rightarrow DK^{+}\pi^{-}$ decays. The analysis is based on a sample corresponding to an integrated luminosity of $5.4 ~\rm{fb}^{-1}$ of proton--proton collision data at $13 ~\rm{TeV}$ centre-of-mass energy recorded with the LHCb detector. The $\overline{D}^{*}(2007)^{0}$ mesons are fully reconstructed in the $\overline{D}^{0}\pi^{0}$ and $\overline{D}^{0}\gamma$ channels, with the $\overline{D}^{0} \rightarrow K^{+}\pi^{-}$ decay. A novel weighting method is used to subtract background while simultaneously applying an event-by-event efficiency correction to account for resonant structures in the decays.

A search for the $$ {B}_{\mathrm{s}}^0 $$ → D*±D∓ decay is performed using proton-proton collision data at centre-of-mass energies of 7, 8 and 13 TeV collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb−1. The decay is observed with a high significance and its branching fraction relative to the B0 → D*±D∓ decay is measured to be $$ \frac{\mathrm{\mathcal{B}}\left({B}_s^0\to {D}^{\ast \pm }{D}^{\mp}\right)}{\left({B}^0\to {D}^{\ast \pm }{D}^{\mp}\right)}=0.137\pm 0.017\pm 0.002\pm 0.006, $$ where the first uncertainty is statistical, the second systematic and the third is due to the uncertainty on the ratio of the $$ {B}_{\mathrm{s}}^0 $$ and B0 hadronisation fractions.

The Cabibbo-suppressed decay $\Lambda_b^0\rightarrow\chi_{c1}p\pi^-$ is observed for the first time using data from proton-proton collisions corresponding to an integrated luminosity of 6fb$^{-1}$, collected with the LHCb detector at a centre-of-mass energy of 13TeV. Evidence for the $\Lambda_b^0\rightarrow\chi_{c2}p\pi^-$ decay is also found. Using the $\Lambda_b^0\rightarrow\chi_{c1}pK^-$ decay as normalisation channel, the ratios of branching fractions are measured to be $$\begin{array}{rcl} \frac{ \mathcal{B} (\Lambda_b^0\rightarrow\chi_{c1}p\pi^-)}{\mathcal{B} (\Lambda_b^0\rightarrow\chi_{c1}pK^-)}&=&(6.59 \pm 1.01 \pm 0.22 ) \times 10^{-2} \,, \frac{\mathcal{B} (\Lambda_b^0\rightarrow\chi_{c2}p\pi^-)}{\mathcal{B} (\Lambda_b^0\rightarrow\chi_{c1}p\pi^-)}&=&0.95 \pm 0.30 \pm 0.04 \pm 0.04 \,, \frac{\mathcal{B} (\Lambda_b^0\rightarrow\chi_{c2}pK^-)}{\mathcal{B} (\Lambda_b^0\rightarrow\chi_{c1}pK^-)}&=&1.06 \pm 0.05 \pm 0.04 \pm 0.04 \,,\end{array}$$ where the first uncertainty is statistical, the second is systematic and the third is due to the uncertainties in the branching fractions of $\chi_{c1,2}\rightarrow J/\psi\gamma$ decays.

The first observation of the Ω−b→Ξ+cK−π− decay is reported using p p collision data at center of mass energies of 7, 8, and 13 TeV collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb−1. Four excited Ω0c baryons are observed in the Ξ+c K− mass projection of the Ω−b→Ξ+cK−π− decays with the significance of each exceeding five standard deviations. They coincide with the states previously observed in prompt pp and e+e− production. Relative production rates, masses, and natural widths of the states are measured, and a test of spin hypotheses is performed. Moreover, the branching ratio of Ω−b→Ξ+cK−π− is measured relative to the Ω−b→Ω0cπ− decay mode and a precise measurement of the Ω−b mass of 6044.3±1.2±1.1+0.19−0.22 MeV is obtained.Received 8 July 2021Accepted 14 September 2021DOI:https://doi.org/10.1103/PhysRevD.104.L091102Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.© 2021 CERN, for the LHCb CollaborationPhysics Subject Headings (PhySH)Hadron collidersTechniquesExperimental TechniquesParticle acceleratorsHadron collidersResearch AreasBranching fractionHadronic decaysPhysical SystemsBottom baryonsCharmed baryonsPropertiesMassParitySpinTechniquesHadron collidersParticles & Fields

The multihadron decays $\Lambda_b^0\rightarrow D^+ p \pi^-\pi^-$ and $\Lambda_b^0\rightarrow D^{*+} p \pi^-\pi^-$ are observed in data corresponding to an integrated luminosity of 3fb$^{-1}$, collected in proton-proton collisions at centre-of-mass energies of 7 and 8TeV by the LHCb detector. Using the~decay $\Lambda_b^0\rightarrow \Lambda_c^+ \pi^+ \pi^-\pi^-$ as a normalisation channel, the ratio of branching fractions is measured to be $$ \frac { {\mathcal{B}} ( \Lambda_b^0\rightarrow D^+ p \pi^-\pi^- ) } { {\mathcal{B}} ( \Lambda_b^0\rightarrow \Lambda_c^+ \pi^+ \pi^-\pi^- ) } \times \frac { {\mathcal{B}} ( D^+ \rightarrow K^-\pi^+\pi^+) } { {\mathcal{B}} ( \Lambda_c^+ \rightarrow p K^-\pi^+ ) } = ( 5.35 \pm 0.21 \pm 0.16 ) \% \,, $$ where the first uncertainty is statistical and the second systematic. The ratio of branching fractions for $\Lambda_b^0\rightarrow D^{*+} p \pi^-\pi^-$ and $\Lambda_b^0\rightarrow D^+ p \pi^-\pi^-$ decays is found to be $$ \frac{ {\mathcal{B}} ( \Lambda_b^0\rightarrow D^{*+} p \pi^-\pi^- )} { {\mathcal{B}} ( \Lambda_b^0\rightarrow D^{+} p \pi^-\pi^- )} \times ( {\mathcal{B}}( D^{*+} \rightarrow \pi^0 ) + {\mathcal{B}}( D^{*+} \rightarrow \gamma )) = ( 61.3 \pm 4.3 \pm 4.0 ) \% \,. $$

An amplitude analysis of flavour-untagged $B_s^0 \to J/\psi p \bar{p}$ decays is performed using a sample of $797\pm31$ decays reconstructed with the LHCb detector. The data, collected in proton-proton collisions between 2011 and 2018, correspond to an integrated luminosity of 9 $\text{fb}^{-1}$. Evidence for a new structure in the $J/\psi p$ and $J/\psi \bar{p}$ systems with a mass of $4337 ^{+7}_{-4} ^{+2}_{-2}~\text{MeV}$ and a width of $29 ^{+26}_{-12} ^{+14}_{-14}~\text{MeV}$ is found, where the first uncertainty is statistical and the second systematic, with a significance in the range of 3.1 to 3.7 $\sigma$, depending on the assigned $J^P$ hypothesis.

A search for $C\!P$ violation in the $\Lambda_b^0 \to p \pi^- \pi^+ \pi^-$ decay is performed using LHCb data corresponding to an integrated luminosity of 6.6$\,fb^{-1}$ collected in $pp$ collisions at centre-of-mass energies of 7, 8 and 13$\,Te\kern -0.1em V$. The analysis uses both triple product asymmetries and the unbinned energy test method. The highest significances of $C\!P$ asymmetry are 2.9 standard deviations from triple product asymmetries and 3.0 standard deviations for the energy test method. Once the global $p$-value is considered, all results are consistent with no $C\!P$ violation. Parity violation is observed at a significance of $5.5$ standard deviations for the triple product asymmetry method and $5.3$ standard deviations for the energy test method.

Measurements of CP observables in B^±→ D K^± and B^±→ D π^± decays are presented, where D represents a superposition of D^0 and D̅^0 states. The D meson is reconstructed in the three-body final state K_S^0K^±π^∓. The analysis uses samples of B mesons produced in proton-proton collisions, corresponding to an integrated luminosity of 1.0, 2.0, and 6.0 fb^-1 collected with the LHCb detector at centre-of-mass energies of √(s) = 7, 8, and 13 TeV, respectively. These measurements are the most precise to date, and provide important input for the determination of the CKM angle γ.

First evidence of a structure in the J/ψ invariant mass distribution is obtained from an amplitude analysis of _b^- → J/ψ K^- decays. The observed structure is consistent with being due to a charmonium pentaquark with strangeness. Its mass and width are determined to be 4458.8±2.9 ^+4.7_-1.1MeV and 17.3±6.5 ^+8.0_-5.7MeV, where the quoted uncertainties are statistical and systematic, respectively. The structure is also consistent with being due to two resonances. In addition, the narrow excited ^- states, (1690)^- and (1820)^-, are seen for the first time in a _b^- decay, and their masses and widths are measured with improved precision. The analysis is performed using pp collision data corresponding to a total integrated luminosity of 9fb^-1, collected with the LHCb experiment at centre-of-mass energies of 7, 8 and 13TeV.

The first observation of the decay ${B}^{0}\ensuremath{\rightarrow}{D}^{0}{\overline{D}}^{0}{K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ is reported using proton-proton collision data corresponding to an integrated luminosity of $4.7\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ collected by the LHCb experiment in 2011, 2012 and 2016. The measurement is performed in the full kinematically allowed range of the decay outside of the ${D}^{*\ensuremath{-}}$ region. The ratio of the branching fraction relative to that of the control channel ${B}^{0}\ensuremath{\rightarrow}{D}^{*\ensuremath{-}}{D}^{0}{K}^{+}$ is measured to be $\mathcal{R}=(14.2\ifmmode\pm\else\textpm\fi{}1.1\ifmmode\pm\else\textpm\fi{}1.0)%$, where the first uncertainty is statistical and the second is systematic. The absolute branching fraction of ${B}^{0}\ensuremath{\rightarrow}{D}^{0}{\overline{D}}^{0}{K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ decays is thus determined to be $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{D}^{0}{\overline{D}}^{0}{K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})=(3.50\ifmmode\pm\else\textpm\fi{}0.27\ifmmode\pm\else\textpm\fi{}0.26\ifmmode\pm\else\textpm\fi{}0.30)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$, where the third uncertainty is due to the branching fraction of the control channel. This decay mode is expected to provide insights to spectroscopy and the charm-loop contributions in rare semileptonic decays.