Nucl. Phys. B 930(2018)563 A search for decays of $B_c^+$ mesons to two charm mesons is performed for
the first time using data corresponding to an integrated luminosity of 3.0
fb$^{-1}$, collected ...by the LHCb experiment in $pp$ collisions at
centre-of-mass energies of 7 and 8 TeV. The decays considered are $B_c^+\to
D^{(*)+}_{(s)} \overline{D}^{(*)0}$ and $B_c^+\to D^{(*)+}_{(s)} D^{(*)0}$,
which are normalised to high-yield $B^+\to D^+_{(s)} \overline{D}^0$ decays. No
evidence for a signal is found and limits are set on twelve $B_c^+$ decay
modes.
J. High Energ. Phys. (2018) 2018: 138 A search is performed in the invariant mass spectrum of the
$B_c^{+}\pi^{+}\pi^{-}$ system for the excited $B_c^{+}$ states
$B_c(2^{1}S_{0})^+$ and ...$B_c(2^{3}S_{1})^+$ using a data sample of $pp$
collisions collected by the LHCb experiment at the centre-of-mass energy of
$\sqrt{s} = 8 \,{\mathrm{TeV}}$, corresponding to an integrated luminosity of
$2 \,{\mathrm{fb^{-1}}}$. No evidence is seen for either state. Upper limits on
the ratios of the production cross-sections of the $B_c(2^{1}S_{0})^+$ and
$B_c(2^{3}S_{1})^+$ states times the branching fractions of
${B_c(2^{1}S_{0})^+} \to {B_c^{+}\pi^{+}\pi^{-}}$ and ${B_c(2^{3}S_{1})^+} \to
{B_c^{*+}\pi^{+}\pi^{-}}$ over the production cross-section of the $B_c^{+}$
state are given as a function of their masses. They are found to be between
0.02 and 0.14 at $95\%$ confidence level for $B_c(2^{1}S_{0})^+$ and
$B_c(2^{3}S_{1})^+$ in the mass ranges $6830, 6890 \,{\mathrm{MeV}}/c^{2}$
and $6795,6890 \,{\mathrm{MeV}}/c^{2}$, respectively.
Phys. Rev. D 97, 031101 (2018) We report measurements of charm-mixing parameters based on the
decay-time-dependent ratio of $D^0\to K^+\pi^-$ to $D^0\to K^-\pi^+$ rates. The
analysis uses a data ...sample of proton-proton collisions corresponding to an
integrated luminosity of $5.0$ fb$^{-1}$ recorded by the LHCb experiment from
2011 through 2016. Assuming charge-parity (CP) symmetry, the mixing parameters
are determined to be $x'^2=(3.9 \pm 2.7) \times10^{-5}$, $y'=(5.28 \pm 0.52)
\times 10^{-3}$, and $R_D=(3.454 \pm 0.031)\times10^{-3}$. Without this
assumption, the measurement is performed separately for $D^0$ and
$\overline{D}{}^0$ mesons, yielding a direct CP-violating asymmetry $A_D
=(-0.1\pm9.1)\times10^{-3}$, and magnitude of the ratio of mixing parameters
$1.00< |q/p| <1.35$ at the $68.3\%$ confidence level. All results include
statistical and systematic uncertainties and improve significantly upon
previous single-measurement determinations. No evidence for CP violation in
charm mixing is observed.
Phys. Rev. Lett. 120, 121801 (2018) A measurement is reported of the ratio of branching fractions
$\mathcal{R}(J/\psi)=\mathcal{B}(B_c^+\,\to\,J/\psi\tau^+\nu_\tau)/\mathcal{B}(B_c^+\,\to\,J/\psi
...\mu^+\nu_\mu)$, where the $\tau^+$ lepton is identified in the decay mode
$\tau^+\,\to\,\mu^+\nu_\mu\overline{\nu}_\tau$. This analysis uses a sample of
proton-proton collision data corresponding to 3.0$\mathrm{\,fb}^{-1}$ of
integrated luminosity recorded with the LHCb experiment at center-of-mass
energies $7\,\mathrm{TeV}$ and $8\,\mathrm{TeV}$. A signal is found for the
decay $B_c^+\,\to\,J/\psi \tau^+\nu_\tau$ at a significance of 3 standard
deviations, corrected for systematic uncertainty, and the ratio of the
branching fractions is measured to be $\mathcal{R}(J/\psi) = 0.71 \pm 0.17
\mathrm{\,(stat)} \pm 0.18\mathrm{\,(syst)}$. This result lies within 2
standard deviations above the range of existing predictions in the Standard
Model.
J. High Energ. Phys. (2018) 2018: 098 A search for charmless four-body decays of $\Lambda_{b}^{0}$ and
$\Xi_{b}^{0}$ baryons with a proton and three charged mesons (either kaons or
pions) in the ...final state is performed. The data sample used was recorded in
2011 and 2012 with the LHCb experiment and corresponds to an integrated
luminosity of 3 fb$^{-1}$. Six decay modes are observed, among which
$\Lambda_{b}^{0} \to pK^{-}\pi^{+}\pi^{-}$, $\Lambda_{b}^{0} \to
pK^{-}K^{+}K^{-}$, $\Xi_{b}^{0} \to pK^{-}\pi^{+}\pi^{-}$ and $\Xi_{b}^{0} \to
pK^{-} \pi^{+}K^{-}$ are established for the first time. Their branching
fractions (including the ratio of hadronisation fractions in the case of the
$\Xi_{b}^{0}$ baryon) are determined relative to the $\Lambda_{b}^{0} \to
\Lambda_{c}^{+}\pi^{-}$ decay.
JHEP 01 (2018) 131 A search for $B^{+} \to D_s^{+}K^{+}K^{-}$ decays is performed using $pp$
collision data corresponding to an integrated luminosity of 4.8 fb$^{-1}$,
collected at centre-of-mass ...energies of 7, 8 and 13$\,$TeV with the LHCb
experiment. A significant signal is observed for the first time and the
branching fraction is determined to be \begin{equation*} \mathcal{B}(B^{+} \to
D_s^{+}K^{+}K^{-} ) = (7.1 \pm 0.5 \pm 0.6 \pm 0.7) \times 10^{-6},
\end{equation*} where the first uncertainty is statistical, the second
systematic and the third due to the uncertainty on the branching fraction of
the normalisation mode $B^{+} \to D_s^{+} \overline{\kern -0.2em D}^{0}$. A
search is also performed for the pure annihilation decay $B^{+} \to
D_s^{+}\phi$. No significant signal is observed and a limit of
\begin{equation*} \mathcal{B}(B^{+} \to D_s^{+}\phi) < 4.9 \times 10^{-7}~(4.2
\times 10^{-7}) \end{equation*} is set on the branching fraction at 95$\%$
(90$\%$) confidence level.
Phys. Rev. D 97, 072013 (2018) The ratio of branching fractions ${\cal{R}}(D^{*-})\equiv {\cal{B}}(B^0 \to
D^{*-} \tau^+ \nu_{\tau})/{\cal{B}}(B^0 \to D^{*-} \mu^+\nu_{\mu})$ is measured
using a data ...sample of proton-proton collisions collected with the LHCb
detector at center-of-mass energies of 7 and 8 TeV, corresponding to an
integrated luminosity of 3$~$fb$^{-1}$. The $\tau$ lepton is reconstructed with
three charged pions in the final state. A novel method is used that exploits
the different vertex topologies of signal and backgrounds to isolate samples of
semitauonic decays of $b$ hadrons with high purity. Using the $B^0 \to
D^{*-}\pi^+\pi^-\pi^+$ decay as the normalization channel, the ratio
${\cal{B}}(B^0 \to D^{*-} \tau^+ \nu_{\tau})/{\cal{B}}(B^0 \to
D^{*-}\pi^+\pi^-\pi^+)$ is measured to be $1.97 \pm 0.13 \pm 0.18$, where the
first uncertainty is statistical and the second systematic. An average of
branching fraction measurements for the normalization channel is used to derive
${\cal{B}}(B^0 \to D^{*-} \tau^+ \nu_{\tau}) = (1.42 \pm 0.094 \pm 0.129 \pm
0.054) \%$, where the third uncertainty is due to the limited knowledge of
${\cal{B}}(B^0\to D^{*-}\pi^+\pi^-\pi^+)$. A test of lepton flavor universality
is performed using the well-measured branching fraction ${\cal{B}}(B^0 \to
D^{*-} \mu^+\nu_{\mu})$ to compute ${\cal{R}}(D^{*-}) = 0.291 \pm 0.019 \pm
0.026 \pm 0.013$, where the third uncertainty originates from the uncertainties
on ${\cal{B}}(B^0 \to D^{*-}\pi^+\pi^-\pi^+)$ and ${\cal{B}}(B^0 \to D^{*-}
\mu^+\nu_{\mu})$. This measurement is in agreement with the Standard Model
prediction and with previous measurements.
JHEP 03 (2018) 043 The ratios of the branching fractions of the decays $\Lambda_{c}^{+}
\rightarrow p \pi^{-} \pi^{+}$, $\Lambda_{c}^{+} \rightarrow p K^{-} K^{+}$,
and $\Lambda_{c}^{+} \rightarrow p ...\pi^{-} K^{+}$ with respect to the
Cabibbo-favoured $\Lambda_{c}^{+} \rightarrow p K^{-} \pi^{+}$ decay are
measured using proton-proton collision data collected with the LHCb experiment
at a 7 TeV centre-of-mass energy and corresponding to an integrated luminosity
of 1.0 fb$^{-1}$:
\begin{align*} \frac{\mathcal{B}(\Lambda_{c}^{+} \rightarrow p \pi^{-}
\pi^{+})}{\mathcal{B}(\Lambda_{c}^{+} \rightarrow p K^{-} \pi^{+})} & = (7.44
\pm 0.08 \pm 0.18)\,\%, \frac{\mathcal{B}(\Lambda_{c}^{+} \rightarrow p K^{-}
K^{+})}{\mathcal{B}(\Lambda_{c}^{+} \rightarrow p K^{-} \pi^{+})} &= (1.70 \pm
0.03 \pm 0.03)\,\%, \frac{\mathcal{B}(\Lambda_{c}^{+} \rightarrow p \pi^{-}
K^{+})}{\mathcal{B}(\Lambda_{c}^{+} \rightarrow p K^{-} \pi^{+})} & = (0.165
\pm 0.015 \pm 0.005 )\,\%, \end{align*} where the uncertainties are statistical
and systematic, respectively. These results are the most precise measurements
of these quantities to date. When multiplied by the world-average value for
$\mathcal{B}(\Lambda_{c}^{+} \rightarrow p K^{-} \pi^{+})$, the corresponding
branching fractions are \begin{align*} \mathcal{B}(\Lambda_{c}^{+} \rightarrow
p \pi^{-} \pi^{+}) &= (4.72 \pm 0.05 \pm 0.11 \pm 0.25) \times 10^{-3},
\mathcal{B}(\Lambda_{c}^{+} \rightarrow p K^{-} K^{+}) &= (1.08 \pm 0.02 \pm
0.02 \pm 0.06) \times 10^{-3}, \mathcal{B}(\Lambda_{c}^{+} \rightarrow p
\pi^{-} K^{+}) &= (1.04 \pm 0.09 \pm 0.03 \pm 0.05) \times 10^{-4},
\end{align*} where the final uncertainty is due to $\mathcal{B}(\Lambda_{c}^{+}
\rightarrow p K^{-} \pi^{+})$.
JHEP 12 (2017) 026 The production of $B^{\pm}$ mesons is studied in $pp$ collisions at
centre-of-mass energies of 7 and 13 TeV, using $B^{\pm}\rightarrow J/\psi
K^{\pm}$ decays and data samples ...corresponding to 1.0 fb$^{-1}$ and 0.3
fb$^{-1}$, respectively. The production cross-sections summed over both charges
and integrated over the transverse momentum range $0<p_{\text{T}}< 40$ GeV/$c$
and the rapidity range $2.0<y<4.5$ are measured to be $\sigma(pp \rightarrow
B^{\pm} X, \sqrt{s} = \text{7 TeV}) = 43.0 \pm 0.2 \pm 2.5 \pm 1.7\mu b,$
$\sigma(pp \rightarrow B^{\pm} X, \sqrt{s} = \text{13 TeV}) = 86.6 \pm 0.5 \pm
5.4 \pm 3.4\mu b,$ where the first uncertainties are statistical, the second
are systematic, and the third are due to the limited knowledge of the
$B^{\pm}\rightarrow J/\psi K^{\pm}$ branching fraction. The ratio of the
cross-section at 13 TeV to that at 7 TeV is determined to be
$2.02\pm0.02\text{(stat)}\pm0.12\text{(syst)}$. Differential cross-sections are
also reported as functions of $p_{\text{T}}$ and $y$. All results are in
agreement with theoretical calculations based on the state-of-art fixed
next-to-leading order quantum chromodynamics.
JHEP 1803 (2018) 078 A search for the lepton-flavour violating decays $B^0_s \rightarrow e^\pm
\mu^\mp$ and $B^0 \rightarrow e^\pm \mu^\mp$ is performed based on a sample of
proton-proton collision ...data corresponding to an integrated luminosity of 3
fb$^{-1}$, collected with the LHCb experiment at centre-of-mass energies of 7
and 8 TeV. The observed yields are consistent with the background-only
hypothesis. Upper limits on the branching fractions are determined to be
$\mathcal{B}(B^0_s \rightarrow e^\pm \mu^\mp) < 5.4\,(6.3) \times 10^{-9}$ and
$\mathcal{B}(B^0 \rightarrow e^\pm \mu^\mp) < 1.0\,(1.3) \times 10^{-9}$ at
$90\%\,(95\%)$ confidence level, which are the strongest limits on these decays
to date.
