Phys. Rev. Lett. 126, 091802 (2021) A measurement of direct CP violation in the decay $B^{+} \rightarrow K^{+}
\pi^{0}$ is reported using a data sample corresponding to an integrated
luminosity of ...5.4 $\textrm{fb}^{-1}$, collected with the LHCb experiment at a
center-of-mass energy of $\sqrt{s}=13$ TeV. The CP asymmetry is measured to be
$0.025 \pm 0.015 \pm 0.006 \pm 0.003$, where the uncertainties are statistical,
systematic, and due to an external input, respectively. This is the most
precise measurement of the CP asymmetry in the decay $B^{+} \rightarrow K^{+}
\pi^{0}$ and exceeds the precision on the current world average. This direct CP
asymmetry is a key input to studies of a long-standing anomaly in $B$ meson
decays, known as the $K\pi$-puzzle. The asymmetry is consistent with the
previous measurements of this quantity, confirming and significantly enhancing
the observed anomalous difference between the direct CP asymmetries of the
$B^{0} \rightarrow K^{+} \pi^{-}$ and $B^{+} \rightarrow K^{+} \pi^{0}$ decays.
Journal of High Energy Physics, 03 (2021) 099 A search for the $B^0_s \!\rightarrow D^{*\pm} D^\mp$ decay is performed
using proton-proton collision data at centre-of-mass energies of $7$, $8$ and
...$13\,\text{TeV}$ collected by the LHCb experiment, corresponding to an
integrated luminosity of $9\,\text{fb}^{-1}$. The decay is observed with a high
significance and its branching fraction relative to the $B^0 \!\rightarrow
D^{*\pm} D^\mp$ decay is measured to be \begin{align*} \frac{\mathcal{B}(B_s^0
\rightarrow D^{\ast \pm} D^{\mp}) }{\mathcal{B}(B^0 \rightarrow D^{\ast \pm}
D^{\mp}) } = 0.137 \pm 0.017 \pm 0.002 \pm 0.006 \,, \end{align*} where the
first uncertainty is statistical, the second systematic and the third is due to
the uncertainty on the ratio of the $B_s^0$ and $B^0$ hadronisation fractions.
Sci.Bull. 66 (2021) 1278-1287 First evidence of a structure in the $J/\psi \varLambda$ invariant mass
distribution is obtained from an amplitude analysis of $\varXi_b^- \to J/\psi
\varLambda K^-$ ...decays. The observed structure is consistent with being due to
a charmonium pentaquark with strangeness. Its mass and width are determined to
be $4458.8\pm2.9\,^{+4.7}_{-1.1}$MeV and $17.3\pm6.5\,^{+8.0}_{-5.7}$MeV, 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 $\varXi^-$ states, $\varXi(1690)^-$ and $\varXi(1820)^-$, are
seen for the first time in a $\varXi_b^-$ 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
$13$TeV.
Journal of High Energy Physics, 04 (2021) 081 Measurements of $C\!P$ observables in $B^\pm \rightarrow D^{(*)} K^\pm$ and
$B^\pm \rightarrow D^{(*)} \pi^\pm$ decays are presented, where $D^{(*)}$
...indicates a neutral $D$ or $D^*$ meson that is an admixture of meson and
anti-meson states. Decays of the $D^*$ meson to the $D\pi^0$ and $D\gamma$
final states are partially reconstructed without inclusion of the neutral pion
or photon. Decays of the $D$ meson are reconstructed in the $K^\pm \pi^\mp$,
$K^+K^-$, and $\pi^+\pi^-$ final states. The analysis uses a sample of charged
$B$ mesons produced in proton-proton collisions and collected with the LHCb
experiment, corresponding to integrated luminosities of 2.0, 1.0, and 5.7
fb$^{-1}$ taken at centre-of-mass energies of 7, 8, and 13 TeV, respectively.
The measurements of partially reconstructed $B^\pm \to D^* K^\pm$ and $B^\pm
\to D^* \pi^\pm$ with $D \to K^\mp \pi^\pm$ decays are the first of their kind,
and a first observation of the $B^\pm \to (D \pi^0)_{D^*} \pi^\pm$ decay is
made with a significance of 6.1 standard deviations. All $C\!P$ observables are
measured with world-best precision, and in combination with other LHCb results
will provide strong constraints on the CKM angle $\gamma$.
Phys. Rev. Lett. 126, 081804 (2021) The first observation of the suppressed semileptonic $B_s^0 \to
K^-\mu^+\nu_\mu$ decay is reported. Using a data sample recorded in {\it pp}
collisions in 2012 ...with the LHCb detector, corresponding to an integrated
luminosity of 2 $\mathrm{fb}^{-1}$, the branching fraction
\mbox{$\mathcal{B}(B_s^0 \to K^-\mu^+\nu_\mu)$} is measured to be
$(1.06\pm0.05~(\mathrm{stat})\pm0.08~(\mathrm{syst}))\times 10^{-4}$, where the
first uncertainty is statistical and the second one represents the combined
systematic uncertainties. The decay $B_s^0 \to D_s^-\mu^+\nu_\mu$, where
$D_s^-$ is reconstructed in the final state $K^+K^-\pi^-$, is used as a
normalization channel to minimize the experimental systematic uncertainty.
Theoretical calculations on the form factors of the $B_s^0 \to K^-$ and $B_s^0
\to D_s^-$ transitions are employed to determine the ratio of the CKM matrix
elements ${|V_{ub}|}/{|V_{cb}|}$ at low and high $B_s^0 \to K^-$ momentum
transfer.
JHEP 03 (2021) 075 The time-dependent $CP$ asymmetries of $B^0\to \pi^+\pi^-$ and
$B^0_\mathrm{s}\!\to K^+K^-$ decays are measured using a data sample of $pp$
collisions corresponding to an ...integrated luminosity of 1.9 fb$^{-1}$,
collected with the LHCb detector at a centre-of-mass energy of 13 TeV. The
results are \begin{eqnarray*} C_{\pi\pi} & = & -0.311 \pm 0.045 \pm 0.015, \\
S_{\pi\pi} & = & -0.706 \pm 0.042 \pm 0.013, \\ C_{KK} & = & \phantom{-}0.164
\pm 0.034 \pm 0.014, \\ S_{KK} & = & \phantom{-}0.123 \pm 0.034 \pm 0.015, \\
\cal {A}^{\mathrm{\Delta\Gamma}}_{\mathit{KK}} & = & -0.83\phantom{0} \pm
0.05\phantom{0} \pm 0.09, \end{eqnarray*} where the first uncertainties are
statistical and the second systematic. The same data sample is used to measure
the time-integrated $CP$ asymmetries of $B^0\to K^+\pi^-$ and
$B^0_\mathrm{s}\to K^-\pi^+$ decays and the results are \begin{eqnarray*}
A_{CP}^{B^0} & = & -0.0824 \pm 0.0033 \pm 0.0033, \\ A_{CP}^{B^0_\mathrm{s}} &
= & \phantom{-}0.236\phantom{0} \pm 0.013\phantom{0} \pm 0.011. \end{eqnarray*}
All results are consistent with earlier measurements. A combination of LHCb
measurements provides the first observation of time-dependent $CP$ violation in
$B^0_\mathrm{s}$ decays.
Eur. Phys. J. C 81, 261 (2021) Long-lived particles decaying to $e^\pm \mu^\mp \nu$, with masses between 7
and $50$ GeV/c$^2$ and lifetimes between 2 and $50$ ps, are searched for by
looking at ...displaced vertices containing electrons and muons of opposite
charges. The search is performed using $5.4$ fb$^{-1}$ of $pp$ collisions
collected with the LHCb detector at a centre-of-mass energy of $\sqrt{s} = 13$
TeV. Three mechanisms of production of long-lived particles are considered: the
direct pair production from quark interactions, the pair production from the
decay of a Standard-Model-like Higgs boson with a mass of $125$ GeV/c$^2$, and
the charged current production from an on-shell $W$ boson with an additional
lepton. No evidence of these long-lived states is obtained and upper limits on
the production cross-section times branching fraction are set on the different
production modes.
Physics Letters B 815 (2021) 136172 The $\varLambda^0_b \to \varLambda^+_c K^+ K^- \pi^-$ decay is observed for
the first time using a data sample of proton-proton collisions at
centre-of-mass ...energies of $\sqrt{s}=7$ and 8 $\rm{TeV}$ collected by the
$\mbox{LHCb}$ detector, corresponding to an integrated luminosity of
$3{\rm{fb}^{-1}}$. The ratio of branching fractions between the $\varLambda^0_b
\to \varLambda^+_c K^+ K^- \pi^-$ and the
$\varLambda^{0}_{b}\to\varLambda^{+}_{c}D^{-}_{s}$ decays is measured to be
\begin{equation*} \frac{\mathcal{B} ( \varLambda^0_b \to \varLambda^+_c K^+ K^-
\pi^-) } {\mathcal{B} ( \varLambda^0_b \to \varLambda^+_c D^-_s)} = (9.26 \pm
0.29 \pm 0.46 \pm 0.26)\times10^{-2}, \end{equation*} where the first
uncertainty is statistical, the second systematic and the third is due to the
knowledge of the $D^-_s \to K^+ K^- \pi^-$ branching fraction. No structure on
the invariant mass distribution of the $\varLambda^+_c K^+$ system is found,
consistent with no open-charm pentaquark signature.
JHEP 03 (2021) 137 The CKM angle $\gamma$ is measured for the first time from mixing-induced
$CP$ violation between $B^0_s \rightarrow D_s^\mp K^\pm \pi^\pm \pi^\mp$ and
$\bar{B}^0_s \rightarrow ...D_s^\pm K^\mp \pi^\mp \pi^\pm$ decays reconstructed in
proton-proton collision data corresponding to an integrated luminosity of 9
${\rm fb}^{-1}$ recorded with the LHCb detector. A time-dependent amplitude
analysis is performed to extract the $CP$-violating weak phase
$\gamma-2\beta_s$ and, subsequently, $\gamma$ by taking the
$B^0_s$-$\bar{B}^0_s$ mixing phase $\beta_{s}$ as an external input. The
measurement yields $\gamma = (44 \pm 12)^\circ$ modulo $180^\circ$, where
statistical and systematic uncertainties are combined. An alternative
model-independent measurement, integrating over the five-dimensional phase
space of the decay, yields $\gamma = (44^{\,+\,20}_{\,-\,13})^\circ$ modulo
$180^\circ$. Moreover, the $B^0_s$-$\bar{B}^0_s$ oscillation frequency is
measured from the flavour-specific control channel $B^0_s \rightarrow D_s^-
\pi^+ \pi^+ \pi^-$ to be $\Delta m_s = (17.757 \pm 0.007 \,({\rm stat.}) \pm
0.008 \,({\rm syst.})) \text{ps}^{-1}$, consistent with and more precise than
the current world-average value.
Phys. Rev. Lett. 126, 122002 (2021) Using $pp$ collision data corresponding to an integrated luminosity of
$5.4\,{\rm fb}^{-1}$ collected with the LHCb detector at a center-of-mass
energy of ...$13\,{\rm TeV}$, the $B^0\to D^-D^+K^+\pi^-$ decay is studied. A new
excited $D_s^+$ meson is observed decaying into the $D^+K^+\pi^-$ final state
with large statistical significance. The pole mass and width, and the
spin-parity of the new state are measured with an amplitude analysis to be
$m_R=2591\pm6\pm7\,{\rm MeV}$, $\Gamma_R=89\pm16\pm12\,{\rm MeV}$ and
$J^P=0^-$, where the first uncertainty is statistical and the second
systematic. Fit fractions for all components in the amplitude analysis are also
reported. The new resonance, denoted as $D_{s0}(2590)^+$, is a strong candidate
to be the $D_s(2^1{S}_0)^+$ state, the radial excitation of the pseudoscalar
ground-state $D_s^+$ meson.
