Search for: All records

A<sc>bstract</sc> This paper presents a study of the charmless three-body decays$$ {B}_{(s)}^0\to {K}_{\mathrm{S}}^0{h}^{+}h{\prime}^{-} $$ $B_{\left(s\right)}^0\to K_S^0{h}^{+}h{\prime }^{-}$ (whereh⁽′⁾=π, K), using a sample ofppcollision data collected by the LHCb experiment during Runs 1 and 2 of the LHC, corresponding to an integrated luminosity of 9 fb⁻¹. The decay$$ {B}_s^0\to {K}_{\mathrm{S}}^0{K}^{+}{K}^{-} $$ $B_s^0\to K_S^0{K}^{+}{K}^{-}$ is observed for the first time, and the following ratios of branching fractions are measured:$$ {\displaystyle \begin{array}{l}\frac{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{K}^{+}{K}^{-}\right)}{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{\pi}^{+}{\pi}^{-}\right)}=0.578\pm 0.007\pm 0.017,\\ {}\frac{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{K}^{\pm }{K}^{\mp}\right)}{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{\pi}^{+}{\pi}^{-}\right)}=0.1363\pm 0.0035\pm 0.051,\\ {}\begin{array}{l}\frac{\mathcal{B}\left({B}_s^0\to {K}_{\mathrm{S}}^0{\pi}^{+}{\pi}^{-}\right)}{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{\pi}^{+}{\pi}^{-}\right)}=0.269\pm 0.011\pm 0.015\pm 0.008,\\ {}\frac{\mathcal{B}\left({B}_s^0\to {K}_{\mathrm{S}}^0{K}^{+}{K}^{-}\right)}{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{\pi}^{+}{\pi}^{-}\right)}=0.0303\pm 0.0041\pm 0.0025\pm 0.0009,\\ {}\frac{\mathcal{B}\left({B}_s^0\to {K}_{\mathrm{S}}^0{K}^{\pm }{\pi}^{\mp}\right)}{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{\pi}^{+}{\pi}^{-}\right)}=1.818\pm 0.021\pm 0.031\pm 0.056,\end{array}\end{array}} $$ $\begin{array}{c}\frac{B\left(B^0\to K_S^0{K}^{+}{K}^{-}\right)}{B\left(B^0\to K_S^0{\pi }^{+}{\pi }^{-}\right)}=0.578\pm 0.007\pm 0.017,\\ \frac{B\left(B^0\to K_S^0{K}^{\pm }{K}^{\mp }\right)}{B\left(B^0\to K_S^0{\pi }^{+}{\pi }^{-}\right)}=0.1363\pm 0.0035\pm 0.051,\\ \begin{array}{c}\frac{B\left(B_s^0\to K_S^0{\pi }^{+}{\pi }^{-}\right)}{B\left(B^0\to K_S^0{\pi }^{+}{\pi }^{-}\right)}=0.269\pm 0.011\pm 0.015\pm 0.008,\\ \frac{B\left(B_s^0\to K_S^0{K}^{+}{K}^{-}\right)}{B\left(B^0\to K_S^0{\pi }^{+}{\pi }^{-}\right)}=0.0303\pm 0.0041\pm 0.0025\pm 0.0009,\\ \frac{B\left(B_s^0\to K_S^0{K}^{\pm }{\pi }^{\mp }\right)}{B\left(B^0\to K_S^0{\pi }^{+}{\pi }^{-}\right)}=1.818\pm 0.021\pm 0.031\pm 0.056,\end{array}\end{array}$ where the uncertainties are statistical, systematic, and due to knowledge of the ratio of hadronisation fractions of the$$ {B}_s^0 $$ $B_s^0$ andB⁰mesons, respectively. 

The time-dependent $CP$ asymmetry in $B^0\to J/\psi \rho (770{)}^0$ decays is measured using proton-proton collision data corresponding to an integrated luminosity of $6{\mathrm{fb}}^{-1}$ , collected with the LHCb detector at a center-of-mass energy of 13 TeV during the years 2015–2018. The $CP$ -violation parameters for this process are determined to be $2{\beta }_{c\overline{c}d}^{\mathrm{eff}}=0.710\pm 0.084\pm 0.051\mathrm{rad}$ and $\left|\lambda \right|=1.019\pm 0.034\pm 0.024$ , where the first uncertainty is statistical and the second systematic. This constitutes the first observation of time-dependent $CP$ violation in $B^0\to J/\psi \rho (770{)}^0$ decays. Assuming approximate SU(3) flavor symmetry, these results are combined with the previous consistent LHCb measurement to set the most stringent constraint on the penguin contribution, $\mathrm{\Delta }{\varphi }_s$ , to the $CP$ -violating phase ${\varphi }_s$ in $B_s^0\to J/\psi \varphi \left(1020\right)$ decays, yielding $\mathrm{\Delta }{\varphi }_s=5.0\pm 4.6\mathrm{mrad}$ . 

A search for the rare decay $B^{+}\to \overline{\mathrm{\Lambda }}p{\mu }^{+}{\mu }^{-}$ is performed using proton-proton collision data recorded by the LHCb experiment at a center-of-mass energy of $\sqrt{s}=13\mathrm{TeV}$ , corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$ . An excess of events is found with respect to the background-only expectation, with a signal significance of 3.5 standard deviations, in the low invariant-mass region of $m\left(\overline{\mathrm{\Lambda }}p\right)<2.8\mathrm{GeV}/c^2$ . The branching fraction is measured to be ${\mathcal{B}}_{\mathrm{low}}(B^{+}\to \overline{\mathrm{\Lambda }}p{\mu }^{+}{\mu }^{-})=\left(1.70_{-0.56}^{+0.65}\right(\mathrm{stat})\pm 0.17(\mathrm{syst})\pm 0.14(\mathrm{ext}\left)\right)\times {10}^{-8}$ , where the last uncertainty is due to external inputs on $\mathcal{B}(B^{+}\to J/\psi \overline{\mathrm{\Lambda }}p)\times \mathcal{B}(J/\psi \to {\mu }^{+}{\mu }^{-})$ . With no significant signal observed in the high $m\left(\overline{\mathrm{\Lambda }}p\right)$ region above $2.8\mathrm{GeV}/c^2$ , an upper limit is set to be ${\mathcal{B}}_{\mathrm{high}}(B^{+}\to \overline{\mathrm{\Lambda }}p{\mu }^{+}{\mu }^{-})<2.8\left(3.7\right)\times {10}^{-9}$ at the 90% (95%) confidence level. 

An analysis of the $B^0\to K^{*0}(\to K^{+}{\pi }^{-}){\mu }^{+}{\mu }^{-}$ decay is presented using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of $8.4{\mathrm{fb}}^{-1}$ . The full set of $CP$ -averaged and $CP$ -asymmetric angular observables is determined in bins of the invariant mass squared of the dimuon system, as well as the branching fraction relative to the $B^0\to J/\psi (\to {\mu }^{+}{\mu }^{-})K^{+}{\pi }^{-}$ decay. For the first time, the full set of observables pertaining to the $K^{+}{\pi }^{-}$ S-wave contribution to the final state are presented and consideration is given to effects arising from the mass of the muons. The extracted $CP$ -asymmetry observables show no significant deviations from zero. The measurements of the $CP$ -averaged observables and the branching fractions continue to exhibit the pattern of tensions with the standard model predictions that have been seen in previous analyses that use part of the dataset considered in this Letter. 

The collinear and transverse-momentum-dependent jet fragmentation function and the radial profile for $B^{\pm }$ mesons in jets are measured. The $B^{\pm }$ mesons are reconstructed through the $J/\psi (\to {\mu }^{+}{\mu }^{-})K^{\pm }$ decay channel using proton-proton collision data collected during 2016–2018 with the LHCb detector at a center-of-mass (c.m.) energy of $\sqrt{s}=13\mathrm{TeV}$ , corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$ . The results complement recent measurements of jet fragmentation functions for heavy-flavor hadrons and suggest a growing contribution of gluon fragmentation to $B^{\pm }$ mesons as the jet transverse momentum increases. 

A flavor-tagged time-dependent analysis of $B^0\to K_{\mathrm{S}}^0{\mu }^{+}{\mu }^{-}$ decays is performed across the full dimuon mass range excluding the $J/\psi$ and $\psi \left(2S\right)$ resonance regions. The analysis uses proton-proton collision data collected by the LHCb experiment in 2011–2018 at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of $9{\mathrm{fb}}^{-1}$ . The $CP$ violation parameters are determined to be $C=-0.13\pm 0.32\pm 0.04$ , $S=+0.82\pm 0.29\pm 0.05$ , where the first uncertainties are statistical and the second are systematic. The results are consistent with the standard model prediction. This is the first experimental study of time-dependent $CP$ violation in $b\to s{\ell }^{+}{\ell }^{-}$ processes. 

The first measurements of the top- and antitop-quark differential production cross sections and the top-quark charge asymmetry in the forward region are presented, using proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$ . The total production cross sections of top and antitop quarks are also determined. Measurements are performed using the $\mu +b\text{-jet}$ final state within a fiducial region defined by $b$ -jet $p_{\mathrm{T},\text{jet}}>50\mathrm{GeV}$ and pseudorapidity $2.2<{\eta }_{\text{jet}}<4.0$ , with the muon from the $W$ -boson decay required to have $p_{\mathrm{T},\mu }>25\mathrm{GeV}$ and $2.0<{\eta }_{\mu }<4.5$ . The muon and $b$ -jet system must satisfy $p_{\mathrm{T}}(\mu +\text{jet})>20\mathrm{GeV}$ . The measured integrated production cross sections for the top and antitop quarks are ${\sigma }_t=0.95\pm 0.04\pm 0.08\pm 0.02\mathrm{pb}$ , ${\sigma }_{\overline{t}}=0.81\pm 0.03\pm 0.07\pm 0.02\mathrm{pb}$ , where the first uncertainty is statistical, the second systematic, and the third accounts for the luminosity uncertainty. The top-quark charge asymmetry is measured to be $A_C^t=0.08\pm 0.03\pm 0.01$ , where the first uncertainty is statistical and the second is systematic. These results are consistent with next-to-leading order Standard Model predictions. 

Abstract An amplitude analysis of the$${{{B} ^0} \!\rightarrow {\eta _{c}} (1S) {{K} ^+} {{\pi } ^-}} $$ $B^0\to {\eta }_c\left(1S\right)K^{+}{\pi }^{-}$ decays with$${\eta _{c}} (1S) \rightarrow {p} {\overline{{p}}} $$ ${\eta }_c\left(1S\right)\to p\overline{p}$ is performed using a sample corresponding to an integrated luminosity of 9$$\,\text {fb} ^{-1}$$ ${\text{fb}}^{-1}$ of$$p $$ $p$ $$p $$ $p$ collision data collected by the LHCb detector at centre-of-mass energies of$$\sqrt{s}$$ $\sqrt{s}$ = 7, 8 and 13$$\,\text {Te\hspace{-1.00006pt}V}$$ $\text{Te}\text{V}$ . The data are described with a model including only intermediate contributions from known$${K} ^{*0}$$ $K_{}^{\ast 0}$ resonances. Evidence for an exotic resonance in the$${\eta _{c}} (1S) {{\pi } ^-} $$ ${\eta }_c\left(1S\right){\pi }^{-}$ system, reported in a previous analysis of this decay channel, is not confirmed. The inclusive branching fraction of the$${{B} ^0} \rightarrow {\eta _{c}} (1S) {{K} ^+} {{\pi } ^-} $$ $B^0\to {\eta }_c\left(1S\right)K^{+}{\pi }^{-}$ decays is measured to be$$\begin{aligned}&\mathcal {B}({{B} ^0} \rightarrow {\eta _{c}} (1S) {{K} ^+} {{\pi } ^-}) \\&\quad = (5.82 \pm 0.20 \pm 0.23 \pm 0.55) \times 10^{-4}, \end{aligned}$$ $\begin{array}{cc}& B(B^0\to {\eta }_c\left(1S\right)K^{+}{\pi }^{-})\\ & =(5.82\pm 0.20\pm 0.23\pm 0.55)\times {10}^{-4},\end{array}$ where the first uncertainty is statistical, the second systematic, and the third arises from the limited knowledge of external branching fractions. 

A search is performed for lepton-number-violating $B^{-}\to D^{(*)+}{\mu }^{-}{\mu }^{-}$ decays, using data collected by the LHCb experiment in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$ . No significant signal is observed, and upper limits are set on the branching fractions, $\mathcal{B}(B^{-}\to D^{+}{\mu }^{-}{\mu }^{-})<4.6\times {10}^{-8}$ and $\mathcal{B}(B^{-}\to D^{*+}{\mu }^{-}{\mu }^{-})<5.9\times {10}^{-8}$ , at the 95% confidence level. 

A time- and flavor-integrated amplitude analysis of $B^0$ and $B_s^0$ decays to the $\left(K^{+}{\pi }^{-}\right)\left(K^{-}{\pi }^{+}\right)$ final state in the $K^{*}\left(892{)}^0{\overline{K}}^{*}\right(892{)}^0$ region is presented, using $pp$ collision data recorded with the LHCb detector in 2011–2018, corresponding to an integrated luminosity of $9{\mathrm{fb}}^{-1}$ . The branching fractions of the $B^0$ and $B_s^0$ decays are measured relative to the $B^0\to D^{-}{\pi }^{+}$ and $B_s^0\to D_s^{-}{\pi }^{+}$ modes, respectively. The corresponding longitudinal polarization fractions are found to be $f_L^d=0.600\pm 0.022\pm 0.017$ and $f_L^s=0.159\pm 0.010\pm 0.007$ , where the uncertainties are statistical and systematic, respectively. The theory-motivated ratio of the squared $B_s^0$ to $B^0$ longitudinally polarized decay amplitudes is found to be $L_{K^{*0}{\overline{K}}^{*0}}=4.92\pm 0.55\pm 0.48\pm 0.02\pm 0.10$ , where the uncertainties are statistical, systematic, due to uncertainty of external mass and lifetime measurements, and due to knowledge of the fragmentation fraction ratio, respectively. This confirms the previously reported tension between experimental determinations and theoretical predictions of longitudinal polarization in $B\to VV$ decays at the level of 4.4 standard deviations.