Phys. Rev. D 102, 112012 (2020) The decay $\Lambda_b^0 \to \eta_c(1S) p K^-$ is observed for the first time
using a data sample of proton-proton collisions, corresponding to an integrated
luminosity ...of 5.5 $fb^{-1}$, collected with the LHCb experiment at a
center-of-mass energy of 13 TeV. The branching fraction of the decay is
measured, using the $\Lambda_b^0 \to J/\psi p K^-$ decay as a normalization
mode, to be $\mathcal{B}(\Lambda_b^0 \to \eta_c(1S) p
K^-)=(1.06\pm0.16\pm0.06^{+0.22}_{-0.19})\times10^{-4}$, where the quoted
uncertainties are statistical, systematic and due to external inputs,
respectively. A study of the $\eta_c(1S) p$ mass spectrum is performed to
search for the $P_c(4312)^+$ pentaquark state. No evidence is observed and an
upper limit of \begin{equation*} \frac{\mathcal{B}(\Lambda_b^0 \to P_c(4312)^+
K^-)\times \mathcal{B}(P_c(4312)^+ \to \eta_c(1S) p)}{\mathcal{B}(\Lambda_b^0
\to \eta_c(1S) p K^-)} < 0.24 \end{equation*} is obtained at the 95% confidence
level.
Phys. Rev. Lett. 125 (2020) 212001 A study of prompt charm-hadron pair production in proton-lead collisions at
$\sqrt{s_\mathrm{NN}}= 8.16$ TeV is performed using data corresponding to an
integrated ...luminosity of about 30 nb^{-1}$, collected with the LHCb
experiment. Production cross-sections for different pairs of charm hadrons are
measured and kinematic correlations between the two charm hadrons are
investigated. This is the first measurement of associated production of two
charm hadrons in proton-lead collisions. The results confirm the predicted
enhancement of double parton scattering production in proton-lead collisions
compared to the single parton scattering production.
Phys. Rev. D 102, 051102 (2020) The first observation of the decay $B^0 \rightarrow D^0 \overline{D}{}^0 K^+
\pi^-$ is reported using proton-proton collision data corresponding to an
integrated ...luminosity of 4.7 $\mathrm{fb}^{-1}$ 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 $D^{*-}$ region. The
ratio of the branching fraction relative to that of the control channel $B^0
\rightarrow D^{*-} D^0 K^+$ is measured to be $\mathcal{R} = (14.2 \pm 1.1 \pm
1.0)\%$, where the first uncertainty is statistical and the second is
systematic. The absolute branching fraction of $B^0 \rightarrow D^0
\overline{D}{}^0 K^+ \pi^-$ decays is thus determined to be $\mathcal{B}(B^0
\rightarrow D^0 \overline{D}{}^0 K^+ \pi^-) = (3.50 \pm 0.27 \pm 0.26 \pm 0.30)
\times 10^{-4}$, 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.
Science Bulletin 65 (2020) 1983 Using proton-proton collision data at centre-of-mass energies of $\sqrt{s} =
7$, $8$ and $13\mathrm{\,TeV}$ recorded by the LHCb experiment at the Large
Hadron ...Collider, corresponding to an integrated luminosity of
$9\mathrm{\,fb}^{-1}$, the invariant mass spectrum of $J/\psi$ pairs is
studied. A narrow structure around $6.9\mathrm{\,GeV/}c^2$ matching the
lineshape of a resonance and a broad structure just above twice the $J/\psi$
mass are observed. The deviation of the data from nonresonant $J/\psi$-pair
production is above five standard deviations in the mass region between $6.2$
and $7.4\mathrm{\,GeV/}c^2$, covering predicted masses of states composed of
four charm quarks. The mass and natural width of the narrow $X(6900)$ structure
are measured assuming a Breit--Wigner lineshape.
JHEP 08 (2020) 123 The decays $B^+\rightarrow J/\psi \pi^+ \pi^- K^+$ are studied using a data
set corresponding to an integrated luminosity of 9fb$^{-1}$ collected with the
LHCb detector in ...proton-proton collisions between 2011 and 2018. Precise
measurements of the ratios of branching fractions with the intermediate
$\psi_2(3823)$, $\chi_{c1}(3872)$ and $\psi(2S)$ states are reported. The decay
of $B^+\rightarrow \psi_2(3823)K^+$ with $\psi_2(3823)\rightarrow
J\psi\pi^+\pi^-$ is observed for the first time with a significance of 5.1
standard deviations. The mass differences between the $\psi_2(3823)$,
$\chi_{c1}(3872)$ and $\psi(2S)$ states are measured to be $$
\begin{array}{rcl} m_{\chi_{c1(3872)}} - m_{\psi_2(3823)} &= & 47.50 \pm 0.53
\pm 0.13\,\mathrm{MeV/}c^2\,, \\ m_{\psi_2(3823)} - m_{\psi(2S)} &= & 137.98
\pm 0.53 \pm 0.14\,\mathrm{MeV/}c^2\,, \\ m_{\chi_{c1}(3872)} - m_{\psi(2S)} &=
& 185.49 \pm 0.06 \pm 0.03\,\mathrm{MeV/}c^2\,, \end{array} $$ resulting in the
most precise determination of the $\chi_{c1}(3782)$ mass. The width of the
$\psi_2(3823)$ state is found to be below 5.2MeV at 90\% confidence level. The
Breit-Wigner width of the $\chi_{c1}(3872)$ state is measured to be $$
\Gamma^{\mathrm{BW}}_{\chi_{c1}(3872)} = 0.96^{+0.19}_{-0.18}\pm0.21
\mathrm{MeV},$$ which is inconsistent with zero by 5.5 standard deviations.
Phys. Rev. D 102, 092005 (2020) A study of the lineshape of the $\chi_{c1}(3872)$ state is made using a data
sample corresponding to an integrated luminosity of $3\,$fb$^{-1}$ collected in
$pp$ ...collisions at centre-of-mass energies of 7 and 8\,TeV with the LHCb
detector. Candidate $\chi_{c1}(3872)$ and $\psi(2S)$ mesons from b-hadron
decays are selected in the $ J/\psi \pi^+ \pi^-$ decay mode. Describing the
{\mbox{lineshape}} with a Breit--Wigner function, the mass splitting between
the $\chi_{c1}(3872)$ and $\psi(2S)$ states, $\Delta m$, and the width of the
$\chi_{c1}(3872)$ state, $\Gamma_{\mathrm{BW}}$, are determined to be
\begin{eqnarray*} \Delta m & = & 185.598 \pm 0.067 \pm 0.068\, \mathrm{MeV} \,,
\\ \Gamma_{\mathrm{BW}} & = & \phantom{00}1.39\phantom{0} \pm 0.24\phantom{0}
\pm 0.10\phantom{0} \mathrm{MeV} \,, \end{eqnarray*} where the first
uncertainty is statistical and the second systematic. Using a Flatt\'e-inspired
model, the mode and full width at half maximum of the lineshape are determined
to be \begin{eqnarray*} \mathrm{mode} & =
3871.69^{\,+\,0.00\,+\,0.05}_{\,-\,0.04\,-\,0.13} &\mathrm{MeV} \\
\mathrm{FWHM} & = 0.22^{\,+\,0.07\,+\,0.11}_{\,-\,0.06\,-\,0.13}& \mathrm{MeV}
. \end{eqnarray*} An investigation of the analytic structure of the Flatt\'e
amplitude reveals a pole structure, which is compatible with a quasi-bound
$D^0\bar{D}^{*0}$ state but a quasi-virtual state is still allowed at the level
of $2$ standard deviations.
JHEP 12 (2020) 139 A measurement of four branching-fraction ratios for three-body decays of $B$
mesons involving two open-charm hadrons in the final state is presented. Run 1
and Run 2 $pp$ collision ...data are used, recorded by the LHCb experiment at
centre-of-mass energies $7$, $8$, and $13$ TeV and corresponding to an
integrated luminosity of $9$ fb$^{-1}$. The measured branching-fraction ratios
are \ \begin{eqnarray} \frac{\mathcal{B} (B^+\to D^{*+}D^-K^+)}{\mathcal{B}
(B^+\to \kern 0.2em\overline{\kern -0.2em D}{}^0 D^0 K^+)} &=& 0.517 \pm 0.015
\pm 0.013 \pm 0.011 , \\ \frac{\mathcal{B} (B^+\to D^{*-}D^+K^+)}{\mathcal{B}
(B^+\to \kern 0.2em\overline{\kern -0.2em D}{}^0 D^0 K^+)} &=& 0.577 \pm 0.016
\pm 0.013 \pm 0.013 , \\ \frac{\mathcal{B} (B^0\to D^{*-}D^0K^+)}{\mathcal{B}
(B^0\to D^- D^0 K^+)} &=& 1.754 \pm 0.028 \pm 0.016 \pm 0.035 , \\
\frac{\mathcal{B} (B^+\to D^{*+}D^-K^+)}{\mathcal{B} (B^+\to D^{*-}D^+K^+)} &=&
0.907 \pm 0.033 \pm 0.014 ,\end{eqnarray} \ where the first of the
uncertainties is statistical, the second systematic, and the third is due to
the uncertainties on the $D$-meson branching fractions. These are the most
accurate measurements of these ratios to date.
https://epjc.epj.org/articles/epjc/abs/2020/10/10052_2020_Article_8365/10052_2020_Article_8365.html A first search for $CP$ violation in the Cabibbo-suppressed
$\Xi_c^+\rightarrow pK^-\pi^+$ decay is ...performed using both a binned and an
unbinned model-independent technique in the Dalitz plot. The studies are based
on a sample of proton-proton collision data, corresponding to an integrated
luminosity of $3.0~{\rm fb^{-1}}$, and collected by the LHCb experiment at
centre-of-mass energies of $7$ and $8~\rm TeV$. The data are consistent with
the hypothesis of no $CP$ violation.
J. High Energ. Phys. 2020, 110 (2020) This paper presents an analysis of the $\Lambda^0_b\rightarrow J/\psi\Lambda$
angular distribution and the transverse production polarisation of
$\Lambda^0_b$ ...baryons in proton-proton collisions at centre-of-mass energies of
7, 8 and 13 TeV. The measurements are performed using data corresponding to an
integrated luminosity of 4.9 fb$^{-1}$, collected with the LHCb experiment. The
polarisation is determined in a fiducial region of $\Lambda^0_b$ transverse
momentum and pseudorapidity of $1 < p_{T} < 20$ GeV$/c$ and $2 < \eta < 5$,
respectively. The data are consistent with $\Lambda^0_b$ baryons being produced
unpolarised in this region. The parity-violating asymmetry parameter of the
$\Lambda\rightarrow p\pi^-$ decay is also determined from the data and its
value is found to be consistent with a recent measurement by the BES\,III
collaboration.
JHEP 07(2020) 123 A precision measurement of the $B_{c}^{+}$ meson mass is performed using
proton-proton collision data collected with the LHCb experiment at
centre-of-mass energies of $7, 8$ and ...$13$ TeV, corresponding to a total
integrated luminosity of $9.0 \,{\rm fb}^{-1}$. The $B_{c}^{+}$ mesons are
reconstructed via the decays $B_{c}^{+} \rightarrow J\mskip -3mu/\mskip
-2mu\psi\mskip 2mu \pi^+$, $B_{c}^{+} \rightarrow J\mskip -3mu/\mskip
-2mu\psi\mskip 2mu \pi^+ \pi^- \pi^+$, $B_{c}^{+} \rightarrow J\mskip
-3mu/\mskip -2mu\psi\mskip 2mu p \bar{p} \pi^+$, $B_{c}^{+} \rightarrow J\mskip
-3mu/\mskip -2mu\psi\mskip 2mu D_{s}^{+}$, $B_{c}^{+} \rightarrow J\mskip
-3mu/\mskip -2mu\psi\mskip 2mu D^{0} K^{+}$ and $B_{c}^{+} \rightarrow
B_{s}^{0} \pi^{+}$. Combining the results of the individual decay channels, the
$B_{c}^{+}$ mass is measured to be $6274.47 \pm 0.27 \,({\rm stat}) \pm 0.17
\,({\rm syst}) \mathrm{\,Me\kern -0.1em V}/c^{2}$. This is the most precise
measurement of the $B_{c}^{+}$ mass to date. The difference between the
$B_{c}^{+}$ and $B_{s}^{0}$ meson masses is measured to be $907.75 \pm 0.37
\,({\rm stat}) \pm 0.27 \,({\rm syst}) \mathrm{\,Me\kern -0.1em V}/c^{2}$.
