EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)

 CERN-EP-2018-108 LHCb-PAPER-2018-013 May 23, 2018

Observation of a new ${{\mathchar 28932\relax}^{-}_{b}}$ resonance

LHCb collaboration†††Authors are listed at the end of this paper.

From samples of $pp$ collision data collected by the LHCb experiment at
$\sqrt{s}=7$, $8$ and $13$$\mathrm{\,Te\kern-1.00006ptV}$, corresponding to
integrated luminosities of 1.0, 2.0 and 1.5$\mbox{\,fb}^{-1}$, respectively, a
peak in both the ${{\mathchar 28931\relax}^{0}_{b}}{{K}^{-}}$ and ${{\mathchar
28932\relax}^{0}_{b}}{{\pi}^{-}}$ invariant mass spectra is observed. In the
quark model, radially and orbitally excited ${{\mathchar
28932\relax}^{-}_{b}}$ resonances with quark content $bds$ are expected.
Referring to this peak as ${{\mathchar 28932\relax}_{b}(6227)^{-}}$, the mass
and natural width are measured to be $m_{{{\mathchar
28932\relax}_{b}(6227)^{-}}}=6226.9\pm 2.0\pm 0.3\pm
0.2$${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$ and $\Gamma_{{{\mathchar
28932\relax}_{b}(6227)^{-}}}=18.1\pm 5.4\pm
1.8$${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$, where the first uncertainty is
statistical, the second is systematic, and the third, on $m_{{{\mathchar
28932\relax}_{b}(6227)^{-}}}$, is due to the knowledge of the ${{\mathchar
28931\relax}^{0}_{b}}$ baryon mass. Relative production rates of the
${{{\mathchar 28932\relax}_{b}(6227)^{-}}\rightarrow{{\mathchar
28931\relax}^{0}_{b}}{{K}^{-}}}$ and ${{{\mathchar
28932\relax}_{b}(6227)^{-}}\rightarrow{{\mathchar
28932\relax}^{0}_{b}}{{\pi}^{-}}}$ decays are also reported.

Published in Phys. Rev. Lett. 121 (2018) 072002

© 2024 CERN for the benefit of the LHCb collaboration, licence CC-BY-4.0.

In the constituent quark model [1, 2], baryonic states form multiplets
according to the symmetry of their flavor, spin, and spatial wave functions.
The masses, widths and decay modes of these states give insight into their
internal structure [3]. The ${{\mathchar 28932\relax}^{0}_{b}}$ and
${{\mathchar 28932\relax}^{-}_{b}}$ states form an isodoublet of $bsq$ bound
states, where $q$ is a $u$ or $d$ quark, respectively. Three such isodoublets,
which are neither radially nor orbitally excited, should exist [4], and
include one with spin $j_{qs}=0$ and $J^{P}=(1/2)^{+}$ (${{\mathchar
28932\relax}_{b}}$), a second with $j_{qs}=1$ and $J^{P}=(1/2)^{+}$
(${{\mathchar 28932\relax}_{b}}^{\prime}$), and a third with $j_{qs}=1$ and
$J^{P}=(3/2)^{+}$ (${{\mathchar 28932\relax}_{b}}^{*}$). Here, $j_{qs}$ is the
spin of the light diquark system $qs$, and $J^{P}$ represents the spin and
parity of the state. Three of the four $j_{qs}=1$ states have been recently
observed through their decays to ${{\mathchar
28932\relax}^{0}_{b}}{{\pi}^{-}}$ and ${{\mathchar
28932\relax}^{-}_{b}}{{\pi}^{+}}$ [5, 6, 7].

Beyond these lowest-lying states, a spectrum of heavier states is expected [8,
9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23], where there are
either radial or orbital excitations amongst the constituent quarks. The only
such states discovered thus far in the $b$-baryon sector are the ${\mathchar
28931\relax}_{b}(5912)^{0}$ and ${\mathchar 28931\relax}_{b}(5920)^{0}$
resonances [24], which are consistent with being orbital excitations of the
${{\mathchar 28931\relax}^{0}_{b}}$ baryon.

In this Letter, we report the first observation of a new state, decaying into
both ${{\mathchar 28931\relax}^{0}_{b}}{{K}^{-}}$ and ${{\mathchar
28932\relax}^{0}_{b}}{{\pi}^{-}}$, using samples of $pp$ collision data
collected with the LHCb experiment at 7, 8 and
13$\mathrm{\,Te\kern-1.00006ptV}$, corresponding to integrated luminosities of
1.0, 2.0 and 1.5$\mbox{\,fb}^{-1}$, respectively. The observation of these
decays is consistent with the strong decay of a radially or orbitally excited
${{\mathchar 28932\relax}^{-}_{b}}$ baryon, hereafter referred to as
${{\mathchar 28932\relax}_{b}(6227)^{-}}$. Charge-conjugate processes are
implicitly included throughout this Letter.

The mass and width of the ${{\mathchar 28932\relax}_{b}(6227)^{-}}$ baryon are
measured using the ${{\mathchar 28931\relax}^{0}_{b}}{{K}^{-}}$ mode, where
the ${{\mathchar 28931\relax}^{0}_{b}}$ baryon is detected through its fully
reconstructed hadronic (HAD) decay to ${{\mathchar
28931\relax}^{+}_{c}}{{\pi}^{-}}$. Larger samples of semileptonic (SL)
${{\mathchar 28931\relax}^{0}_{b}}$ and ${{\mathchar 28932\relax}^{0}_{b}}$
decays are used to measure the production ratios

$\displaystyle R({{\mathchar 28931\relax}^{0}_{b}}{{K}^{-}})$
$\displaystyle\equiv\frac{f_{{{\mathchar
28932\relax}_{b}(6227)^{-}}}}{f_{{{\mathchar
28931\relax}^{0}_{b}}}}{\mathcal{B}}({{\mathchar
28932\relax}_{b}(6227)^{-}}\rightarrow{{\mathchar
28931\relax}^{0}_{b}}{{K}^{-}}),$ (1) $\displaystyle R({{\mathchar
28932\relax}^{0}_{b}}{{\pi}^{-}})$ $\displaystyle\equiv\frac{f_{{{\mathchar
28932\relax}_{b}(6227)^{-}}}}{f_{{{\mathchar
28932\relax}^{0}_{b}}}}{\mathcal{B}}({{\mathchar
28932\relax}_{b}(6227)^{-}}\rightarrow{{\mathchar
28932\relax}^{0}_{b}}{{\pi}^{-}}),$ (2)

where $f_{{{\mathchar 28932\relax}_{b}(6227)^{-}}}$, $f_{{{\mathchar
28932\relax}^{0}_{b}}}$ and $f_{{{\mathchar 28931\relax}^{0}_{b}}}$ are the
fragmentation fractions of a $b$ quark into each baryon and ${\mathcal{B}}$
represents a branching fraction. Here, the ${{\mathchar 28931\relax}^{0}_{b}}$
and ${{\mathchar 28932\relax}^{0}_{b}}$ baryons are detected using
${{\mathchar 28931\relax}^{0}_{b}}\rightarrow{{\mathchar
28931\relax}^{+}_{c}}{\mu^{-}}X$ and ${{\mathchar
28932\relax}^{0}_{b}}\rightarrow{{\mathchar 28932\relax}^{+}_{c}}{\mu^{-}}X$
decays, where $X$ represents undetected particles. Throughout the text,
$H_{b}^{0}$ ($H_{c}^{+}$) is used to designate either a ${{\mathchar
28931\relax}^{0}_{b}}$ or ${{\mathchar 28932\relax}^{0}_{b}}$ (${{\mathchar
28931\relax}^{+}_{c}}$ or ${{\mathchar 28932\relax}^{+}_{c}}$) baryon. Owing
to much larger branching fractions, the SL signal yields are about an order of
magnitude larger than that of any fully hadronic final state, which enables
the observation of the ${{\mathchar
28932\relax}_{b}(6227)^{-}}\rightarrow{{\mathchar
28932\relax}^{0}_{b}}{{\pi}^{-}}$ mode. The SL decays are not used in the
${{\mathchar 28932\relax}_{b}(6227)^{-}}$ mass or width determination, as they
have larger systematic uncertainties due to modeling of the mass resolution.

The LHCb detector [25, 26] is a single-arm forward spectrometer covering the
pseudorapidity range $2<\eta<5$, designed for the study of particles
containing $b$ or $c$ quarks [25, 26].

The tracking system provides a measurement of the momentum, $p$, of charged
particles with a relative uncertainty that varies from 0.5% at low momentum to
1.0% at 200${\mathrm{\,Ge\kern-1.00006ptV\\!/}c}$. Events are selected online
by a trigger, which consists of a hardware stage, based on information from
the calorimeter and muon systems, followed by a software stage, which applies
a full event reconstruction [27, 28]. Simulated data samples are produced
using the software packages described in Refs. [29, 30, 31, 32, 33, 34,
*Agostinelli:2002hh, 36].

Samples of ${{\mathchar 28931\relax}^{0}_{b}}$ (${{\mathchar
28932\relax}^{0}_{b}}$) are formed from ${{\mathchar
28931\relax}^{+}_{c}}{{\pi}^{-}}$ and ${{\mathchar
28931\relax}^{+}_{c}}{\mu^{-}}$ (${{\mathchar 28932\relax}^{+}_{c}}{\mu^{-}}$)
combinations, where ${{\mathchar 28931\relax}^{+}_{c}}$ and ${{\mathchar
28932\relax}^{+}_{c}}$ decays are reconstructed in the $p{{K}^{-}}{{\pi}^{+}}$
final state. The $H_{c}^{+}$ decay products must have particle identification
(PID) information consistent with the given particle hypothesis, and be
inconsistent with originating from a primary vertex (PV) by requiring each to
have large $\chi^{2}_{\text{IP}}$ with respect to all PVs in the event. Here
$\chi^{2}_{\text{IP}}$ is the difference in $\chi^{2}$ of the vertex fit of a
given PV when the particle (here $p$, ${{K}^{-}}$ or ${{\pi}^{+}}$) is
included or excluded from the fit. The $H_{c}^{+}$ candidate must have a
fitted vertex significantly displaced from all PVs in the event and have an
invariant mass within 60${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$ of the
known $H_{c}^{+}$ mass.

The $H_{c}^{+}$ background is dominated by random combinations of tracks from
nonsignal $b$-hadron decays. In the ${{\mathchar 28932\relax}^{+}_{c}}$
sample, about 15% of this background is due to misidentified
${{D}^{+}}\rightarrow{{K}^{-}}{{\pi}^{+}}{{\pi}^{+}},~{}{{D}^{+}}\rightarrow{{K}^{+}}{{K}^{-}}{{\pi}^{+}}$,
${{D}^{+}_{s}}\rightarrow{{K}^{+}}{{K}^{-}}{{\pi}^{+}}$ and
${{D}^{*+}}\rightarrow({{D}^{0}}\rightarrow{{K}^{-}}{{\pi}^{+}}){{\pi}^{+}}$
decays. These cross-feed contributions are suppressed by employing tighter PID
requirements on candidates that are consistent with being one of these charm
mesons, with only a 1% loss of signal efficiency. These tighter requirements
are not applied to the ${{\mathchar 28931\relax}^{+}_{c}}$ sample, as the
cross-feed contributions are negligible.

Muon (pion) candidates with transverse momentum
$\mbox{$p_{\mathrm{T}}$}>1{\mathrm{\,Ge\kern-1.00006ptV\\!/}c}$
($0.5$${\mathrm{\,Ge\kern-1.00006ptV\\!/}c}$) and large $\chi^{2}_{\text{IP}}$
are combined with $H_{c}^{+}$ candidates to form the $H_{b}^{0}$ samples. Each
$H_{b}^{0}$ decay vertex is required to be significantly displaced from all
PVs in the event. For the ${{\mathchar
28931\relax}^{0}_{b}}\rightarrow{{\mathchar 28931\relax}^{+}_{c}}{{\pi}^{-}}$
decay, the reconstructed ${{\mathchar 28931\relax}^{0}_{b}}$ trajectory must
point back to one of the PVs in the event; only a very loose pointing
requirement is imposed on the SL decay due to the momentum carried by the
undetected particles. To reduce background in the SL decay samples, the $z$
coordinates of the $H_{c}^{+}$ and $H_{b}^{0}$ decay vertices are required to
satisfy $z(H_{c}^{+})-z(H_{b}^{0})>-0.05$ mm, where $z$ is measured along the
beam direction. Candidates that satisfy the invariant mass requirements,
$5.2<M({{\mathchar
28931\relax}^{+}_{c}}{{\pi}^{-}})<6.0$${\mathrm{\,Ge\kern-1.00006ptV\\!/}c^{2}}$
or $M(H_{c}^{+}{\mu^{-}})<8$${\mathrm{\,Ge\kern-1.00006ptV\\!/}c^{2}}$, are
retained, where $M$ designates the invariant mass of the system of indicated
particle(s).

To further suppress background in the ${{\mathchar
28932\relax}^{0}_{b}}\rightarrow{{\mathchar 28932\relax}^{+}_{c}}{\mu^{-}}X$
sample, a boosted decision tree (BDT) discriminant [37, 38] is used. The BDT
exploits fourteen input variables: the $\chi^{2}$ values of the fitted
${{\mathchar 28932\relax}^{+}_{c}}$ and ${{\mathchar 28932\relax}^{0}_{b}}$
decay vertices, and the momentum, $p_{\mathrm{T}}$, $\chi^{2}_{\text{IP}}$ and
a PID variable for each ${{\mathchar 28932\relax}^{+}_{c}}$ final-state
particle. Simulated signal decays and background from the ${{\mathchar
28932\relax}^{+}_{c}}$ mass sidebands,
$30<|M(p{{K}^{-}}{{\pi}^{+}})-m_{{{\mathchar
28932\relax}^{+}_{c}}}|<60$${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$, in data
are used to train the BDT, where $m$ refers to the known mass of the indicated
particle [39]. The PID response for final-state hadrons in the signal decay is
obtained from large ${\mathchar 28931\relax}\rightarrow p{{\pi}^{-}}$ and
${{D}^{*+}}\rightarrow({{D}^{0}}\rightarrow{{K}^{-}}{{\pi}^{+}}){{\pi}^{+}}$
calibration samples in data, which is weighted to reproduce the kinematics of
the signal. The chosen requirement on the BDT response provides an efficiency
of about 90% (40%) on the signal (background).

Figure 1 shows the mass spectra for ${{\mathchar
28931\relax}^{0}_{b}}\rightarrow{{\mathchar 28931\relax}^{+}_{c}}{{\pi}^{-}}$,
${{\mathchar 28931\relax}^{+}_{c}}\rightarrow p{{K}^{-}}{{\pi}^{+}}$ (from
${{\mathchar 28931\relax}^{0}_{b}}\rightarrow{{\mathchar
28931\relax}^{+}_{c}}{\mu^{-}}X$) and ${{\mathchar
28932\relax}^{+}_{c}}\rightarrow p{{K}^{-}}{{\pi}^{+}}$ (from ${{\mathchar
28932\relax}^{0}_{b}}\rightarrow{{\mathchar 28932\relax}^{+}_{c}}{\mu^{-}}X$)
candidates. For the ${{\mathchar 28931\relax}^{0}_{b}}\rightarrow{{\mathchar
28931\relax}^{+}_{c}}{{\pi}^{-}}$ mode, a peak at the known ${{\mathchar
28931\relax}^{0}_{b}}$ mass is seen. For the SL modes, the ${{\mathchar
28931\relax}^{+}_{c}}$ and ${{\mathchar 28932\relax}^{+}_{c}}$ mass peaks are
used to determine the number of ${{\mathchar 28931\relax}^{0}_{b}}$ and
${{\mathchar 28932\relax}^{0}_{b}}$ baryon decays, as the combinatorial
background from random $H_{c}^{+}{\mu^{-}}$ combinations is at the 1% level.
The mass spectra are fit with the sum of two Gaussian functions with a common
mean to represent the signal component and an exponential background function.
The yields are given in Table 1.

Figure 1: Invariant mass spectra for (top) ${{\mathchar 28931\relax}^{0}_{b}}\rightarrow{{\mathchar 28931\relax}^{+}_{c}}{{\pi}^{-}}$, (middle) ${{\mathchar 28931\relax}^{+}_{c}}$ from ${{\mathchar 28931\relax}^{0}_{b}}\rightarrow{{\mathchar 28931\relax}^{+}_{c}}{\mu^{-}}X$, and (bottom) ${{\mathchar 28932\relax}^{+}_{c}}$ from ${{\mathchar 28932\relax}^{0}_{b}}\rightarrow{{\mathchar 28932\relax}^{+}_{c}}{\mu^{-}}X$ candidate decays. The left column is for $7,\,8$ TeV and the right is for 13 TeV data. Fits are overlaid, as described in the text. Here, the ${{\mathchar 28931\relax}^{0}_{b}}\rightarrow{{\mathchar 28931\relax}^{+}_{c}}{\mu^{-}}X$ mode has been prescaled by a factor of ten. Table 1: Uncorrected ${{\mathchar 28932\relax}_{b}(6227)^{-}}$ and $H_{b}^{0}$ signal yields for $7,\,8$ and 13 TeV data. The $H_{b}^{0}$ yields are limited to the signal regions used to form ${{\mathchar 28932\relax}_{b}(6227)^{-}}$ candidates (see text). ${{\mathchar 28932\relax}_{b}(6227)^{-}}$ |  $7,\,8$$\mathrm{\,Te\kern-1.00006ptV}$ | 13$\mathrm{\,Te\kern-1.00006ptV}$
---|---|---
final state | $N({{\mathchar 28932\relax}_{b}(6227)^{-}})$ |  $~{}~{}N(H_{b}^{0})$ [$10^{3}$] | $N({{\mathchar 28932\relax}_{b}(6227)^{-}})$ |  $~{}~{}N(H_{b}^{0})$ [$10^{3}$]
$({{\mathchar 28931\relax}^{0}_{b}})_{\rm HAD}{{K}^{-}}$ | $170\pm 53$ | $~{}\,204.6\pm 0.5$ | $215\pm 63$ | $~{}\,252.7\pm 0.6$
$({{\mathchar 28931\relax}^{0}_{b}})_{\rm SL}{{K}^{-}}$ | $2772\pm 325$ | $3133\pm 6$ | $3701\pm 432$ | $3226\pm 6$
$({{\mathchar 28932\relax}^{0}_{b}})_{\rm SL}{{\pi}^{-}}$ | $351\pm 68$ | $~{}~{}~{}36.6\pm 0.3$ | $274\pm 73$ | $~{}~{}~{}46.5\pm 0.3$

To form ${{\mathchar 28932\relax}_{b}(6227)^{-}}$ candidates, a ${{\mathchar
28931\relax}^{0}_{b}}$ (${{\mathchar 28932\relax}^{0}_{b}}$) candidate is
combined with a ${{K}^{-}}$ (${{\pi}^{-}}$) meson that has small
$\chi^{2}_{\text{IP}}$, consistent with being produced in the strong decay of
the ${{\mathchar 28932\relax}_{b}(6227)^{-}}$ resonance. Only $H_{b}^{0}$
candidates satisfying $|M({{\mathchar 28931\relax}^{+}_{c}}{{\pi}^{-}})_{\rm
HAD}-m_{{{\mathchar
28931\relax}^{0}_{b}}}|<60$${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$,
$|M(p{{K}^{-}}{{\pi}^{+}})_{\rm SL}-m_{{{\mathchar
28931\relax}^{+}_{c}}}|<15$${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$, and
$|M(p{{K}^{-}}{{\pi}^{+}})_{\rm SL}-m_{{{\mathchar
28932\relax}^{+}_{c}}}|<18$${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$ are
considered, where HAD and SL indicate the sample from which the mass is
determined. We require $p_{\rm
T}^{{{K}^{-}}}>800$${\mathrm{\,Me\kern-1.00006ptV\\!/}c}$ and $p_{\rm
T}^{{{\pi}^{-}}}>900$${\mathrm{\,Me\kern-1.00006ptV\\!/}c}$, based on an
optimization of the expected statistical uncertainty on the ${{\mathchar
28932\relax}_{b}(6227)^{-}}$ signal yield, using simulation to model the
signal and either wrong-sign (${{\mathchar
28931\relax}^{0}_{b}}{{K}^{+}},~{}{{\mathchar
28932\relax}^{0}_{b}}{{\pi}^{+}}$) or ${{\mathchar
28932\relax}_{b}(6227)^{-}}$ mass sideband samples in data to model the
background. After all selections the dominant source of background is due to
combinations of real ${{\mathchar 28931\relax}^{0}_{b}}$ (${{\mathchar
28932\relax}^{0}_{b}}$) decays with a random ${{K}^{-}}$ (${{\pi}^{-}}$)
meson. All candidates satisfying these selections are retained.

To improve the resolution on the ${{\mathchar 28932\relax}_{b}(6227)^{-}}$
mass, we use the mass differences ${\delta m_{K}\equiv M({{\mathchar
28931\relax}^{0}_{b}}{{K}^{-}})-M({{\mathchar 28931\relax}^{0}_{b}})}$ and
${\delta m_{\pi}\equiv M({{\mathchar
28932\relax}^{0}_{b}}{{\pi}^{-}})-M({{\mathchar 28932\relax}^{0}_{b}})}$, for
the ${{\mathchar 28931\relax}^{0}_{b}}{{K}^{-}}$ and ${{\mathchar
28932\relax}^{0}_{b}}{{\pi}^{-}}$ final states, respectively. The $\delta
m_{K(\pi)}$ resolution is obtained from simulated ${{\mathchar
28932\relax}_{b}(6227)^{-}}$ decays, where the decay width is set to a
negligible value. For the ${{\mathchar
28931\relax}^{0}_{b}}\rightarrow{{\mathchar 28931\relax}^{+}_{c}}{{\pi}^{-}}$
mode, the $\delta m_{K}$ resolution model is approximately Gaussian with a
width of 2.4${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$. For the SL decays, the
missing momentum, $p_{\rm miss}$, is estimated by assuming it is carried by a
zero-mass particle that balances the momentum transverse to the $H_{b}^{0}$
direction (formed from its decay vertex and PV), and satisfies the mass
constraint $(p_{H_{c}^{+}}+p_{{\mu^{-}}}+p_{\rm miss})^{2}=m_{H_{b}^{0}}^{2}$.
Mass resolution shape parameters are obtained by fitting the $\delta
m_{K(\pi)}$ spectra from simulated decays, which include contributions from
excited charm baryons and final states with ${\tau^{-}}$ leptons. The core of
the resolution function has a half-width at half-maximum of about
20${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$, and has a tail toward larger
mass (see Appendix). The obtained shape parameters are fixed in the fits to
data.

The $\delta m_{K}$ and $\delta m_{\pi}$ spectra in data are shown in Fig. 2.
The ${{\mathchar 28932\relax}_{b}(6227)^{-}}$ mass and width are obtained from
a simultaneous unbinned maximum-likelihood fit to the $\delta m_{K}$ spectra
in 7, 8 and 13$\mathrm{\,Te\kern-1.00006ptV}$ data, using the ${{\mathchar
28931\relax}^{0}_{b}}\rightarrow{{\mathchar 28931\relax}^{+}_{c}}{{\pi}^{-}}$
mode. The signal shape is described by a $P$-wave relativistic Breit-Wigner
function [40] with a Blatt-Weisskopf barrier factor [41], convoluted with a
Gaussian resolution function of width
2.4${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$. The mass and width are common
parameters in the fit. The background shape is described by a smooth threshold
function [42] with shape parameters that are freely and independently varied
in the fits to the two data sets. A peak is observed in both data sets, with a
mean $\delta m_{K}^{\rm peak}=607.3\pm
2.0$${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$ and width $\Gamma_{{{\mathchar
28932\relax}_{b}(6227)^{-}}}=18.1\pm
5.4$${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$. The peak has a local
statistical significance of about 7.9$\sigma$ for the combined fit, based on
the difference in log-likelihoods between a fit with zero signal and the best
fit. The signal yields are given in Table 1.

The ${{\mathchar 28932\relax}_{b}(6227)^{-}}\rightarrow{{\mathchar
28931\relax}^{0}_{b}}{{K}^{-}}$ decay with ${{\mathchar
28931\relax}^{0}_{b}}\rightarrow{{\mathchar 28931\relax}^{+}_{c}}{\mu^{-}}X$
is fit in a similar way, except for the different resolution function (see
Appendix). A Gaussian constraint on the width of $\Gamma_{{{\mathchar
28932\relax}_{b}(6227)^{-}}}=18.1\pm
5.4$${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$ is applied, as obtained from
the fit to the hadronic mode, and the mean is freely varied. A peak is
observed at a mass difference of $610.8\pm
1.0\mathrm{\,(stat)}$${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$, which is
consistent with that of the hadronic mode, and it contains a yield about 15
times larger, as expected. The statistical significance of this peak is about
25$\sigma$, thus clearly establishing this peaking structure.

The ${{\mathchar 28932\relax}^{0}_{b}}{{\pi}^{-}}$ final state is investigated
by examining the $\delta m_{\pi}$ spectra in ${{{\mathchar
28932\relax}_{b}(6227)^{-}}\rightarrow{{\mathchar
28932\relax}^{0}_{b}}{{\pi}^{-}}}$ candidate decays, as shown in the bottom
row of Fig. 2. The fit is performed in an analogous way to the $\delta m_{K}$
spectra, except for a different resolution function (see Appendix for $\delta
m_{\pi}$ resolution). The fitted mean of $440\pm
5{\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$ is consistent with the value
expected from the hadronic mode of $\delta m_{K}^{\rm peak}+m_{{{\mathchar
28931\relax}^{0}_{b}}}-m_{{{\mathchar 28932\relax}^{0}_{b}}}=435\pm
2{\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$. The statistical significance of
the peak is 9.2$\sigma$.

Figure 2: Spectra of mass differences for ${{\mathchar
28932\relax}_{b}(6227)^{-}}$ candidates, reconstructed in the final states
(top) ${{\mathchar 28931\relax}^{0}_{b}}{{K}^{-}}$, with ${{\mathchar
28931\relax}^{0}_{b}}\rightarrow{{\mathchar 28931\relax}^{+}_{c}}{{\pi}^{-}}$,
(middle) ${{\mathchar 28931\relax}^{0}_{b}}{{K}^{-}}$, with ${{\mathchar
28931\relax}^{0}_{b}}\rightarrow{{\mathchar 28931\relax}^{+}_{c}}{\mu^{-}}X$,
and (bottom) ${{\mathchar 28932\relax}^{0}_{b}}{{\pi}^{-}}$, with ${{\mathchar
28932\relax}^{0}_{b}}\rightarrow{{\mathchar 28932\relax}^{+}_{c}}{\mu^{-}}X$,
along with the results of the fits. The left column is for 7, 8 TeV and the
right is for 13 TeV data. The symbol $M^{*}$ represents the mass after the
constraint $(p_{H_{c}^{+}}+p_{{\mu^{-}}}+p_{\rm miss})^{2}=m_{H_{b}^{0}}^{2}$
is applied, as described in the text.

The production ratios are computed using

$\displaystyle R({{\mathchar
28931\relax}^{0}_{b}}{{K}^{-}})=\frac{N({{\mathchar
28932\relax}_{b}(6227)^{-}}\rightarrow{{\mathchar
28931\relax}^{0}_{b}}{{K}^{-}})}{\epsilon_{\rm rel}N({{\mathchar
28931\relax}^{0}_{b}})}\kappa\,,$ (3) $\displaystyle R({{\mathchar
28932\relax}^{0}_{b}}{{\pi}^{-}})=\frac{N({{\mathchar
28932\relax}_{b}(6227)^{-}}\rightarrow{{\mathchar
28932\relax}^{0}_{b}}{{\pi}^{-}})}{\epsilon_{\rm rel}^{\prime}N({{\mathchar
28932\relax}^{0}_{b}})}\kappa^{\prime}\,,$ (4)

where $N$ represents the yields in Table 1, and $\epsilon_{\rm
rel}^{(\prime)}$ is the relative efficiency between the ${{\mathchar
28932\relax}_{b}(6227)^{-}}$ and $H_{b}^{0}$ selections, reported in Table 2.

Table 2: Relative efficiencies ($\epsilon_{\rm rel}^{(\prime)}$) for the SL modes. Uncertainties are due only to the finite size of the simulated samples. Final state |  $7,\,8$$\mathrm{\,Te\kern-1.00006ptV}$ | 13$\mathrm{\,Te\kern-1.00006ptV}$
---|---|---
${{\mathchar 28931\relax}^{0}_{b}}{{K}^{-}}$ | $0.295\pm 0.006$ | $0.305\pm 0.005$
${{\mathchar 28932\relax}^{0}_{b}}{{\pi}^{-}}$ | $0.236\pm 0.007$ | $0.277\pm 0.006$

The quantity $\kappa^{(\prime)}$ represents corrections to the $N(H_{b}^{0})$
SL signal yields to account for (i) random $H_{c}^{+}{\mu^{-}}$ combinations,
(ii) cross-feed from ${{\mathchar 28932\relax}^{-}_{b}}\rightarrow{{\mathchar
28932\relax}^{+}_{c}}{\mu^{-}}X$ decays into the ${{\mathchar
28932\relax}^{0}_{b}}\rightarrow{{\mathchar 28932\relax}^{+}_{c}}{\mu^{-}}$
sample, and (iii) slightly different integrated luminosities used for the
${{\mathchar 28932\relax}_{b}(6227)^{-}}$ and $H_{b}^{0}$ samples. The
contribution from random $H_{c}^{+}{\mu^{-}}$ combinations is estimated from a
study of the wrong-sign ($H_{c}^{+}{\mu^{+}}$) and right-sign
($H_{c}^{+}{\mu^{-}}$) yields, from which a correction of $1.010\pm 0.002$ to
both $R({{\mathchar 28932\relax}^{0}_{b}}{{\pi}^{-}})$ and $R({{\mathchar
28931\relax}^{0}_{b}}{{K}^{-}})$ is found. Cross-feeds from SL ${{\mathchar
28932\relax}^{-}_{b}}$ decays, which must be subtracted from $N({{\mathchar
28932\relax}^{0}_{b}})$, are inferred by adding a ${{\pi}^{-}}$ meson to the
${{\mathchar 28932\relax}^{+}_{c}}{\mu^{-}}$ candidate and searching for
excited ${{\mathchar 28932\relax}^{0}_{c}}$ states. Mass peaks associated with
the ${{\mathchar 28932\relax}_{c}}(2645)^{0}$ and ${{\mathchar
28932\relax}_{c}}(2790)^{0}$ resonances are observed, although for the former
about half is due to ${{\mathchar
28932\relax}_{c}}(2815)^{+}\rightarrow{{\mathchar
28932\relax}_{c}}(2645)^{0}{{\pi}^{+}}$ decays, as determined through a study
of the ${{\mathchar 28932\relax}^{+}_{c}}{{\pi}^{+}}$ mass spectrum. Since the
${{\mathchar 28932\relax}_{c}}(2815)^{+}{\mu^{-}}$ final state is
predominantly from ${{\mathchar 28932\relax}^{0}_{b}}$ decays, this
contribution is not subtracted. After correcting for the pion detection
efficiency, we estimate that $R({{\mathchar 28932\relax}^{0}_{b}}{{\pi}^{-}})$
must be corrected by $1.11\pm 0.03$. Slightly different-size data samples are
used for the ${{\mathchar 28932\relax}_{b}(6227)^{-}}$ and inclusive
$H_{b}^{0}$ yield determinations, which amounts to corrections of less than
3%.

A number of sources of systematic uncertainty have been considered. For the
mass and width, the momentum scale uncertainty of 0.03% [43] leads to a
0.1${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$ uncertainty on $\delta m_{K}$. A
fit bias on the mass of 0.1${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$ is
observed in simulation, and is corrected for and a systematic uncertainty of
equal size is assigned. Uncertainty due to the signal shape model is estimated
by using a nonrelativistic Breit-Wigner signal shape and varying the Gaussian
resolution by $\pm$10% about its nominal value. With these variations,
systematic uncertainties of 0.2${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$ on
$\delta m_{K}$, and 0.9${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$ on
$\Gamma_{{{\mathchar 28932\relax}_{b}(6227)^{-}}}$ are obtained. Sensitivity
to the background function is assessed by varying the fit range by
100${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$ on both ends, from which maximum
shifts of 0.2${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$ in the mass and
1.6${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$ in the width are observed; these
values are assigned as systematic uncertainties. Adding these systematic
uncertainties in quadrature, leads to a total systematic uncertainty of
0.3${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$ on the mass and
1.8${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$ on the width.

The systematic uncertainties affecting the production ratio measurements are
listed in Table 3. The background shape affects the yield determination, and
the associated systematic uncertainty is estimated by varying the fit range as
described above. (Different background models give smaller deviations.) For
the signal shape, the uncertainty is dominated by the resolution function. In
an alternative fit, the resolution parameters are allowed to vary within twice
the expected uncertainty and we take the difference with respect to the
nominal result as the uncertainty. To assess the dependence on the kinematical
properties of the ${{\mathchar 28932\relax}_{b}(6227)^{-}}$ resonance, the
$p_{\mathrm{T}}$ spectrum in simulation is weighted by $1\pm 0.01\times p_{\rm
T}^{{{\mathchar
28932\relax}_{b}(6227)^{-}}}\\!/({\mathrm{\,Ge\kern-1.00006ptV\\!/}c})$, based
on previous studies of the ${{\mathchar 28932\relax}^{0}_{b}}$ and
${{\mathchar 28931\relax}^{0}_{b}}$ production spectra [44]; the relative
change in efficiency is assigned as a systematic uncertainty. The charged-
particle tracking efficiency, obtained using large samples of
${{J\mskip-3.0mu/\mskip-2.0mu\psi\mskip 2.0mu}}\rightarrow{\mu^{+}}{\mu^{-}}$
decays [45], contributes an uncertainty of 1% to $\epsilon_{\rm
rel}^{(\prime)}$. The systematic uncertainty of the PID requirement on the
${{K}^{-}}$ or ${{\pi}^{-}}$ from the ${{\mathchar
28932\relax}_{b}(6227)^{-}}$ baryon is determined by comparing the PID
response of kaons and pions in the ${{\mathchar
28931\relax}^{+}_{c}}\rightarrow p{{K}^{-}}{{\pi}^{+}}$ decay between data and
simulation, where the latter are obtained from calibration data, as described
previously. The uncertainty on $N(H_{b}^{0})$ is taken as the quadratic sum of
the uncertainties on the fitted yields and the uncertainties on the
$\kappa^{(\prime)}$ corrections. Lastly, the finite size of the simulated
samples is taken into account.

Table 3: Summary of systematic uncertainties on $R({{\mathchar 28931\relax}^{0}_{b}}{{K}^{-}})$ and $R({{\mathchar 28932\relax}^{0}_{b}}{{\pi}^{-}})$, in units of $10^{-3}$. |  $R({{\mathchar 28931\relax}^{0}_{b}}{{K}^{-}})~{}[10^{-3}]$ | $R({{\mathchar 28932\relax}^{0}_{b}}{{\pi}^{-}})~{}[10^{-3}]$
---|---|---
Source |  $7,\,8$$\mathrm{\,Te\kern-1.00006ptV}$ | 13$\mathrm{\,Te\kern-1.00006ptV}$ |  $7\,,8$$\mathrm{\,Te\kern-1.00006ptV}$ | 13$\mathrm{\,Te\kern-1.00006ptV}$
Background shape | 0.3 | 0.3 | 6.0 | 3.0
Signal shape | 0.1 | 0.1 | 1.0 | 0.2
${{\mathchar 28932\relax}_{b}(6227)^{-}}$ $p_{\mathrm{T}}$ | ${}^{+0.16}_{-0.27}$ | ${}^{+0.14}_{-0.33}$ | ${}^{+2.5}_{-3.2}$ | ${}^{+0.9}_{-1.5}$
Tracking efficiency | 0.03 | 0.03 | 0.5 | 0.2
PID requirement | 0.05 | 0.06 | 0.5 | 0.2
$N(H_{b}^{0})$ | 0.01 | 0.01 | 1.4 | 0.7
Simulated sample size | 0.07 | 0.05 | 1.4 | 0.6
Total | 0.4 | 0.4 | 7.0 | 3.3

In summary, we report the first observation of a new state, assumed to be an
excited ${{\mathchar 28932\relax}^{-}_{b}}$ state, using $pp$ collision data
samples collected by LHCb at $\sqrt{s}=7\,,8$ and
13$\mathrm{\,Te\kern-1.00006ptV}$. The mass and width are measured to be

$\displaystyle m_{{{\mathchar 28932\relax}_{b}(6227)^{-}}}-m_{{{\mathchar
28931\relax}^{0}_{b}}}$ $\displaystyle=607.3\pm 2.0\mathrm{\,(stat)}\pm
0.3\mathrm{\,(syst)}{\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}},$
$\displaystyle\Gamma_{{{\mathchar 28932\relax}_{b}(6227)^{-}}}$
$\displaystyle=18.1\pm 5.4\mathrm{\,(stat)}\pm
1.8\mathrm{\,(syst)}{\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}},$ $\displaystyle
m_{{{\mathchar 28932\relax}_{b}(6227)^{-}}}$ $\displaystyle=6226.9\pm
2.0\mathrm{\,(stat)}\pm 0.3\mathrm{\,(syst)}\pm 0.2({{\mathchar
28931\relax}^{0}_{b}}){\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}},$

where for the last result we have used $m_{{{\mathchar
28931\relax}^{0}_{b}}}=5619.58\pm
0.17{\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$ [39].

We have also measured the relative production rates to two final states,
${{\mathchar 28931\relax}^{0}_{b}}{{K}^{-}}$ and ${{\mathchar
28932\relax}^{0}_{b}}{{\pi}^{-}}$, as summarized in Table 4. The
$R({{\mathchar 28931\relax}^{0}_{b}}{{K}^{-}})$ values from the hadronic mode
are consistent with those obtained in the SL mode, and are about an order of
magnitude smaller than $R({{\mathchar 28932\relax}^{0}_{b}}{{\pi}^{-}})$.
Assuming $f_{{{\mathchar 28932\relax}^{0}_{b}}}\simeq 0.1f_{{{\mathchar
28931\relax}^{0}_{b}}}$ [46, 47, 48], we find that the ratio of branching
fractions ${\mathcal{B}}({{\mathchar
28932\relax}_{b}(6227)^{-}}\rightarrow{{\mathchar
28931\relax}^{0}_{b}}{{K}^{-}})/{\mathcal{B}}({{\mathchar
28932\relax}_{b}(6227)^{-}}\rightarrow{{\mathchar
28932\relax}^{0}_{b}}{{\pi}^{-}})\simeq 1$, albeit with sizable uncertainty
($\approx\pm 0.5$) due to theoretical assumptions and the values of
experimental inputs.

Table 4: Measured ratios $R({{\mathchar 28931\relax}^{0}_{b}}{{K}^{-}})$ and $R({{\mathchar 28932\relax}^{0}_{b}}{{\pi}^{-}})$ for $7\,,8$ and 13 TeV data, in units of $10^{-3}$. The uncertainties are statistical (first) and systematic (second). Quantity $[10^{-3}]$ |  $7\,,8$$\mathrm{\,Te\kern-1.00006ptV}$ | 13$\mathrm{\,Te\kern-1.00006ptV}$
---|---|---
$R({{\mathchar 28931\relax}^{0}_{b}}{{K}^{-}})$ | $3.0\pm 0.3\pm 0.4$ | $3.4\pm 0.3\pm 0.4$
$R({{\mathchar 28932\relax}_{b}}{{\pi}^{-}})$ | $47\pm 10\pm 7$ | $22\pm 6\pm 3$

The mass of this structure and the observed decay modes are consistent with
expectations of either a ${{\mathchar 28932\relax}_{b}}(1P)^{-}$ or
${{\mathchar 28932\relax}_{b}}(2S)^{-}$ state [8, 9, 10, 11, 12, 13, 14, 15,
16, 17, 18, 19, 20, 21, 22, 23]. As there are several excited ${{\mathchar
28932\relax}^{-}_{b}}$ states expected in this mass region, the presence of
more than one of these states contributing to this peak cannot be excluded.
More precise measurements of the width and the relative branching fractions to
${{\mathchar 28931\relax}^{0}_{b}}{{K}^{-}}$ and ${{\mathchar
28932\relax}^{0}_{b}}{{\pi}^{-}}$, as well as ${{\mathchar
28932\relax}_{b}}^{\prime}{{\pi}^{-}}$ and ${{\mathchar
28932\relax}_{b}}^{*}{{\pi}^{-}}$, could help to determine the $J^{P}$ quantum
numbers of this state [20].

## Acknowledgements

We express our gratitude to our colleagues in the CERN accelerator departments
for the excellent performance of the LHC. We thank the technical and
administrative staff at the LHCb institutes. We acknowledge support from CERN
and from the national agencies: CAPES, CNPq, FAPERJ and FINEP (Brazil); MOST
and NSFC (China); CNRS/IN2P3 (France); BMBF, DFG and MPG (Germany); INFN
(Italy); NWO (The Netherlands); MNiSW and NCN (Poland); MEN/IFA (Romania);
MinES and FASO (Russia); MinECo (Spain); SNSF and SER (Switzerland); NASU
(Ukraine); STFC (United Kingdom); NSF (USA). We acknowledge the computing
resources that are provided by CERN, IN2P3 (France), KIT and DESY (Germany),
INFN (Italy), SURF (The Netherlands), PIC (Spain), GridPP (United Kingdom),
RRCKI and Yandex LLC (Russia), CSCS (Switzerland), IFIN-HH (Romania), CBPF
(Brazil), PL-GRID (Poland) and OSC (USA). We are indebted to the communities
behind the multiple open-source software packages on which we depend.
Individual groups or members have received support from AvH Foundation
(Germany), EPLANET, Marie Skłodowska-Curie Actions and ERC (European Union),
ANR, Labex P2IO and OCEVU, and Région Auvergne-Rhône-Alpes (France), Key
Research Program of Frontier Sciences of CAS, CAS PIFI, and the Thousand
Talents Program (China), RFBR, RSF and Yandex LLC (Russia), GVA, XuntaGal and
GENCAT (Spain), Herchel Smith Fund, the Royal Society, the English-Speaking
Union and the Leverhulme Trust (United Kingdom).

Appendix

The mass resolution functions for the ${{{\mathchar
28932\relax}_{b}(6227)^{-}}\rightarrow{{\mathchar
28931\relax}^{0}_{b}}{{K}^{-}}}$ and ${{{\mathchar
28932\relax}_{b}(6227)^{-}}\rightarrow{{\mathchar
28932\relax}^{0}_{b}}{{\pi}^{-}}}$ semileptonic decays are provided below.

Figure 3: Distribution of (left) $M^{*}({{\mathchar
28931\relax}^{0}_{b}}{{K}^{-}})-M^{*}({{\mathchar 28931\relax}^{0}_{b}})$ for
simulated ${{\mathchar 28932\relax}_{b}(6227)^{-}}\rightarrow{{\mathchar
28931\relax}^{0}_{b}}{{K}^{-}}$ decays, where ${{\mathchar
28931\relax}^{0}_{b}}\rightarrow{{\mathchar 28931\relax}^{+}_{c}}{\mu^{-}}X$,
and (right) $M^{*}({{\mathchar
28932\relax}^{0}_{b}}{{\pi}^{-}})-M^{*}({{\mathchar 28932\relax}^{0}_{b}})$
for simulated ${{\mathchar 28932\relax}_{b}(6227)^{-}}\rightarrow{{\mathchar
28932\relax}^{0}_{b}}{{\pi}^{-}}$ decays, where ${{\mathchar
28932\relax}^{0}_{b}}\rightarrow{{\mathchar 28932\relax}^{+}_{c}}{\mu^{-}}X$.
The symbol $M^{*}$ represents the mass after the constraint
$(p_{H_{c}^{+}}+p_{{\mu^{-}}}+p_{\rm miss})^{2}=m_{H_{b}^{0}}^{2}$ is applied,
as described in the text. The natural width used in the simulation is set to a
negligible value, so that these spectra are due entirely to the mass
resolution. Fits to the sum of a nonrelativistic Breit-Wigner function and a
Crystal Ball function [Skwarnicki:1986xj] with a common mean value are
overlaid.

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LHCb collaboration

R. Aaij27, B. Adeva41, M. Adinolfi48, C.A. Aidala73, Z. Ajaltouni5, S. Akar59,
P. Albicocco18, J. Albrecht10, F. Alessio42, M. Alexander53, A. Alfonso
Albero40, S. Ali27, G. Alkhazov33, P. Alvarez Cartelle55, A.A. Alves Jr59, S.
Amato2, S. Amerio23, Y. Amhis7, L. An3, L. Anderlini17, G. Andreassi43, M.
Andreotti16,g, J.E. Andrews60, R.B. Appleby56, F. Archilli27, P. d’Argent12,
J. Arnau Romeu6, A. Artamonov39, M. Artuso61, K. Arzymatov37, E. Aslanides6,
M. Atzeni44, S. Bachmann12, J.J. Back50, S. Baker55, V. Balagura7,b, W.
Baldini16, A. Baranov37, R.J. Barlow56, S. Barsuk7, W. Barter56, F.
Baryshnikov34, V. Batozskaya31, B. Batsukh61, V. Battista43, A. Bay43, J.
Beddow53, F. Bedeschi24, I. Bediaga1, A. Beiter61, L.J. Bel27, N. Beliy63, V.
Bellee43, N. Belloli20,i, K. Belous39, I. Belyaev34,42, E. Ben-Haim8, G.
Bencivenni18, S. Benson27, S. Beranek9, A. Berezhnoy35, R. Bernet44, D.
Berninghoff12, E. Bertholet8, A. Bertolin23, C. Betancourt44, F. Betti15,42,
M.O. Bettler49, M. van Beuzekom27, Ia. Bezshyiko44, L. Bian64, S. Bifani47, P.
Billoir8, A. Birnkraut10, A. Bizzeti17,u, M. Bjørn57, T. Blake50, F. Blanc43,
S. Blusk61, D. Bobulska53, V. Bocci26, O. Boente Garcia41, T. Boettcher58, A.
Bondar38,w, N. Bondar33, S. Borghi56,42, M. Borisyak37, M. Borsato41,42, F.
Bossu7, M. Boubdir9, T.J.V. Bowcock54, C. Bozzi16,42, S. Braun12, M.
Brodski42, J. Brodzicka29, D. Brundu22, E. Buchanan48, A. Buonaura44, C.
Burr56, A. Bursche22, J. Buytaert42, W. Byczynski42, S. Cadeddu22, H. Cai64,
R. Calabrese16,g, R. Calladine47, M. Calvi20,i, M. Calvo Gomez40,m, A.
Camboni40,m, P. Campana18, D.H. Campora Perez42, L. Capriotti56, A.
Carbone15,e, G. Carboni25, R. Cardinale19,h, A. Cardini22, P. Carniti20,i, L.
Carson52, K. Carvalho Akiba2, G. Casse54, L. Cassina20, M. Cattaneo42, G.
Cavallero19,h, R. Cenci24,p, D. Chamont7, M.G. Chapman48, M. Charles8, Ph.
Charpentier42, G. Chatzikonstantinidis47, M. Chefdeville4, V. Chekalina37, C.
Chen3, S. Chen22, S.-G. Chitic42, V. Chobanova41, M. Chrzaszcz42, A.
Chubykin33, P. Ciambrone18, X. Cid Vidal41, G. Ciezarek42, P.E.L. Clarke52, M.
Clemencic42, H.V. Cliff49, J. Closier42, V. Coco42, J. Cogan6, E. Cogneras5,
L. Cojocariu32, P. Collins42, T. Colombo42, A. Comerma-Montells12, A. Contu22,
G. Coombs42, S. Coquereau40, G. Corti42, M. Corvo16,g, C.M. Costa Sobral50, B.
Couturier42, G.A. Cowan52, D.C. Craik58, A. Crocombe50, M. Cruz Torres1, R.
Currie52, C. D’Ambrosio42, F. Da Cunha Marinho2, C.L. Da Silva74, E.
Dall’Occo27, J. Dalseno48, A. Danilina34, A. Davis3, O. De Aguiar Francisco42,
K. De Bruyn42, S. De Capua56, M. De Cian43, J.M. De Miranda1, L. De Paula2, M.
De Serio14,d, P. De Simone18, C.T. Dean53, D. Decamp4, L. Del Buono8, B.
Delaney49, H.-P. Dembinski11, M. Demmer10, A. Dendek30, D. Derkach37, O.
Deschamps5, F. Dettori54, B. Dey65, A. Di Canto42, P. Di Nezza18, S.
Didenko70, H. Dijkstra42, F. Dordei42, M. Dorigo42,y, A. Dosil Suárez41, L.
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Durante42, J.M. Durham74, D. Dutta56, R. Dzhelyadin39, M. Dziewiecki12, A.
Dziurda42, A. Dzyuba33, S. Easo51, U. Egede55, V. Egorychev34, S.
Eidelman38,w, S. Eisenhardt52, U. Eitschberger10, R. Ekelhof10, L. Eklund53,
S. Ely61, A. Ene32, S. Escher9, S. Esen27, H.M. Evans49, T. Evans57, A.
Falabella15, N. Farley47, S. Farry54, D. Fazzini20,42,i, L. Federici25, G.
Fernandez40, P. Fernandez Declara42, A. Fernandez Prieto41, F. Ferrari15, L.
Ferreira Lopes43, F. Ferreira Rodrigues2, M. Ferro-Luzzi42, S. Filippov36,
R.A. Fini14, M. Fiorini16,g, M. Firlej30, C. Fitzpatrick43, T. Fiutowski30, F.
Fleuret7,b, M. Fontana22,42, F. Fontanelli19,h, R. Forty42, V. Franco Lima54,
M. Frank42, C. Frei42, J. Fu21,q, W. Funk42, C. Färber42, M. Féo Pereira
Rivello Carvalho27, E. Gabriel52, A. Gallas Torreira41, D. Galli15,e, S.
Gallorini23, S. Gambetta52, M. Gandelman2, P. Gandini21, Y. Gao3, L.M. Garcia
Martin72, B. Garcia Plana41, J. García Pardiñas44, J. Garra Tico49, L.
Garrido40, D. Gascon40, C. Gaspar42, L. Gavardi10, G. Gazzoni5, D. Gerick12,
E. Gersabeck56, M. Gersabeck56, T. Gershon50, Ph. Ghez4, S. Gianì43, V.
Gibson49, O.G. Girard43, L. Giubega32, K. Gizdov52, V.V. Gligorov8, D.
Golubkov34, A. Golutvin55,70, A. Gomes1,a, I.V. Gorelov35, C. Gotti20,i, E.
Govorkova27, J.P. Grabowski12, R. Graciani Diaz40, L.A. Granado Cardoso42, E.
Graugés40, E. Graverini44, G. Graziani17, A. Grecu32, R. Greim27, P.
Griffith22, L. Grillo56, L. Gruber42, B.R. Gruberg Cazon57, O. Grünberg67, C.
Gu3, E. Gushchin36, Yu. Guz39,42, T. Gys42, C. Göbel62, T. Hadavizadeh57, C.
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Hennessy54, L. Henry72, E. van Herwijnen42, M. Heß67, A. Hicheur2, D. Hill57,
M. Hilton56, P.H. Hopchev43, W. Hu65, W. Huang63, Z.C. Huard59, W.
Hulsbergen27, T. Humair55, M. Hushchyn37, D. Hutchcroft54, P. Ibis10, M.
Idzik30, P. Ilten47, K. Ivshin33, R. Jacobsson42, J. Jalocha57, E. Jans27, A.
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Kirn9, S. Klaver18, K. Klimaszewski31, T. Klimkovich11, S. Koliiev46, M.
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Krzemien31, W. Kucewicz29,l, M. Kucharczyk29, V. Kudryavtsev38,w, A.K.
Kuonen43, T. Kvaratskheliya34,42, D. Lacarrere42, G. Lafferty56, A. Lai22, D.
Lancierini44, G. Lanfranchi18, C. Langenbruch9, T. Latham50, C. Lazzeroni47,
R. Le Gac6, A. Leflat35, J. Lefrançois7, R. Lefèvre5, F. Lemaitre42, O.
Leroy6, T. Lesiak29, B. Leverington12, P.-R. Li63, T. Li3, Z. Li61, X.
Liang61, T. Likhomanenko69, R. Lindner42, F. Lionetto44, V. Lisovskyi7, X.
Liu3, D. Loh50, A. Loi22, I. Longstaff53, J.H. Lopes2, D. Lucchesi23,o, M.
Lucio Martinez41, A. Lupato23, E. Luppi16,g, O. Lupton42, A. Lusiani24, X.
Lyu63, F. Machefert7, F. Maciuc32, V. Macko43, P. Mackowiak10, S. Maddrell-
Mander48, O. Maev33,42, K. Maguire56, D. Maisuzenko33, M.W. Majewski30, S.
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Mancinelli6, D. Marangotto21,q, J. Maratas5,v, J.F. Marchand4, U. Marconi15,
C. Marin Benito40, M. Marinangeli43, P. Marino43, J. Marks12, G.
Martellotti26, M. Martin6, M. Martinelli43, D. Martinez Santos41, F. Martinez
Vidal72, A. Massafferri1, R. Matev42, A. Mathad50, Z. Mathe42, C. Matteuzzi20,
A. Mauri44, E. Maurice7,b, B. Maurin43, A. Mazurov47, M. McCann55,42, A.
McNab56, R. McNulty13, J.V. Mead54, B. Meadows59, C. Meaux6, F. Meier10, N.
Meinert67, D. Melnychuk31, M. Merk27, A. Merli21,q, E. Michielin23, D.A.
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Mogini8, J. Molina Rodriguez1,z, T. Mombächer10, I.A. Monroy66, S. Monteil5,
M. Morandin23, G. Morello18, M.J. Morello24,t, O. Morgunova69, J. Moron30,
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Müller10, K. Müller44, V. Müller10, P. Naik48, T. Nakada43, R. Nandakumar51,
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J.M. Otalora Goicochea2, P. Owen44, A. Oyanguren72, P.R. Pais43, A. Palano14,
M. Palutan18,42, G. Panshin71, A. Papanestis51, M. Pappagallo52, L.L.
Pappalardo16,g, W. Parker60, C. Parkes56, G. Passaleva17,42, A. Pastore14, M.
Patel55, C. Patrignani15,e, A. Pearce42, A. Pellegrino27, G. Penso26, M. Pepe
Altarelli42, S. Perazzini42, D. Pereima34, P. Perret5, L. Pescatore43, K.
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Casasus41, F. Polci8, M. Poli Lener18, A. Poluektov50, N. Polukhina70,c, I.
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Popov47,11, S. Poslavskii39, C. Potterat2, E. Price48, J. Prisciandaro41, C.
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Rademacker48, M. Rama24, M. Ramos Pernas41, M.S. Rangel2, F. Ratnikov37,x, G.
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Rodrigues43, E. Rodrigues59, J.A. Rodriguez Lopez66, A. Rogozhnikov37, S.
Roiser42, A. Rollings57, V. Romanovskiy39, A. Romero Vidal41, M. Rotondo18,
M.S. Rudolph61, T. Ruf42, J. Ruiz Vidal72, J.J. Saborido Silva41, N.
Sagidova33, B. Saitta22,f, V. Salustino Guimaraes62, C. Sanchez Gras27, C.
Sanchez Mayordomo72, B. Sanmartin Sedes41, R. Santacesaria26, C. Santamarina
Rios41, M. Santimaria18, E. Santovetti25,j, G. Sarpis56, A. Sarti18,k, C.
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Schmelzer10, B. Schmidt42, O. Schneider43, A. Schopper42, H.F. Schreiner59, M.
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Coutinho44, L. Silva de Oliveira2, G. Simi23,o, S. Simone14,d, N. Skidmore12,
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1Centro Brasileiro de Pesquisas Físicas (CBPF), Rio de Janeiro, Brazil
2Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil
3Center for High Energy Physics, Tsinghua University, Beijing, China
4Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IN2P3-LAPP, Annecy,
France
5Clermont Université, Université Blaise Pascal, CNRS/IN2P3, LPC, Clermont-
Ferrand, France
6Aix Marseille Univ, CNRS/IN2P3, CPPM, Marseille, France
7LAL, Univ. Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, Orsay, France
8LPNHE, Université Pierre et Marie Curie, Université Paris Diderot,
CNRS/IN2P3, Paris, France
9I. Physikalisches Institut, RWTH Aachen University, Aachen, Germany
10Fakultät Physik, Technische Universität Dortmund, Dortmund, Germany
11Max-Planck-Institut für Kernphysik (MPIK), Heidelberg, Germany
12Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg,
Germany
13School of Physics, University College Dublin, Dublin, Ireland
14INFN Sezione di Bari, Bari, Italy
15INFN Sezione di Bologna, Bologna, Italy
16INFN Sezione di Ferrara, Ferrara, Italy
17INFN Sezione di Firenze, Firenze, Italy
18INFN Laboratori Nazionali di Frascati, Frascati, Italy
19INFN Sezione di Genova, Genova, Italy
20INFN Sezione di Milano-Bicocca, Milano, Italy
21INFN Sezione di Milano, Milano, Italy
22INFN Sezione di Cagliari, Monserrato, Italy
23INFN Sezione di Padova, Padova, Italy
24INFN Sezione di Pisa, Pisa, Italy
25INFN Sezione di Roma Tor Vergata, Roma, Italy
26INFN Sezione di Roma La Sapienza, Roma, Italy
27Nikhef National Institute for Subatomic Physics, Amsterdam, Netherlands
28Nikhef National Institute for Subatomic Physics and VU University Amsterdam,
Amsterdam, Netherlands
29Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of
Sciences, Kraków, Poland
30AGH - University of Science and Technology, Faculty of Physics and Applied
Computer Science, Kraków, Poland
31National Center for Nuclear Research (NCBJ), Warsaw, Poland
32Horia Hulubei National Institute of Physics and Nuclear Engineering,
Bucharest-Magurele, Romania
33Petersburg Nuclear Physics Institute (PNPI), Gatchina, Russia
34Institute of Theoretical and Experimental Physics (ITEP), Moscow, Russia
35Institute of Nuclear Physics, Moscow State University (SINP MSU), Moscow,
Russia
36Institute for Nuclear Research of the Russian Academy of Sciences (INR RAS),
Moscow, Russia
37Yandex School of Data Analysis, Moscow, Russia
38Budker Institute of Nuclear Physics (SB RAS), Novosibirsk, Russia
39Institute for High Energy Physics (IHEP), Protvino, Russia
40ICCUB, Universitat de Barcelona, Barcelona, Spain
41Instituto Galego de Física de Altas Enerxías (IGFAE), Universidade de
Santiago de Compostela, Santiago de Compostela, Spain
42European Organization for Nuclear Research (CERN), Geneva, Switzerland
43Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL),
Lausanne, Switzerland
44Physik-Institut, Universität Zürich, Zürich, Switzerland
45NSC Kharkiv Institute of Physics and Technology (NSC KIPT), Kharkiv, Ukraine
46Institute for Nuclear Research of the National Academy of Sciences (KINR),
Kyiv, Ukraine
47University of Birmingham, Birmingham, United Kingdom
48H.H. Wills Physics Laboratory, University of Bristol, Bristol, United
Kingdom
49Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom
50Department of Physics, University of Warwick, Coventry, United Kingdom
51STFC Rutherford Appleton Laboratory, Didcot, United Kingdom
52School of Physics and Astronomy, University of Edinburgh, Edinburgh, United
Kingdom
53School of Physics and Astronomy, University of Glasgow, Glasgow, United
Kingdom
54Oliver Lodge Laboratory, University of Liverpool, Liverpool, United Kingdom
55Imperial College London, London, United Kingdom
56School of Physics and Astronomy, University of Manchester, Manchester,
United Kingdom
57Department of Physics, University of Oxford, Oxford, United Kingdom
58Massachusetts Institute of Technology, Cambridge, MA, United States
59University of Cincinnati, Cincinnati, OH, United States
60University of Maryland, College Park, MD, United States
61Syracuse University, Syracuse, NY, United States
62Pontifícia Universidade Católica do Rio de Janeiro (PUC-Rio), Rio de
Janeiro, Brazil, associated to 2
63University of Chinese Academy of Sciences, Beijing, China, associated to 3
64School of Physics and Technology, Wuhan University, Wuhan, China, associated
to 3
65Institute of Particle Physics, Central China Normal University, Wuhan,
Hubei, China, associated to 3
66Departamento de Fisica , Universidad Nacional de Colombia, Bogota, Colombia,
associated to 8
67Institut für Physik, Universität Rostock, Rostock, Germany, associated to 12
68Van Swinderen Institute, University of Groningen, Groningen, Netherlands,
associated to 27
69National Research Centre Kurchatov Institute, Moscow, Russia, associated to
34
70National University of Science and Technology ”MISIS”, Moscow, Russia,
associated to 34
71National Research Tomsk Polytechnic University, Tomsk, Russia, associated to
34
72Instituto de Fisica Corpuscular, Centro Mixto Universidad de Valencia -
CSIC, Valencia, Spain, associated to 40
73University of Michigan, Ann Arbor, United States, associated to 61
74Los Alamos National Laboratory (LANL), Los Alamos, United States, associated
to 61

aUniversidade Federal do Triângulo Mineiro (UFTM), Uberaba-MG, Brazil
bLaboratoire Leprince-Ringuet, Palaiseau, France
cP.N. Lebedev Physical Institute, Russian Academy of Science (LPI RAS),
Moscow, Russia
dUniversità di Bari, Bari, Italy
eUniversità di Bologna, Bologna, Italy
fUniversità di Cagliari, Cagliari, Italy
gUniversità di Ferrara, Ferrara, Italy
hUniversità di Genova, Genova, Italy
iUniversità di Milano Bicocca, Milano, Italy
jUniversità di Roma Tor Vergata, Roma, Italy
kUniversità di Roma La Sapienza, Roma, Italy
lAGH - University of Science and Technology, Faculty of Computer Science,
Electronics and Telecommunications, Kraków, Poland
mLIFAELS, La Salle, Universitat Ramon Llull, Barcelona, Spain
nHanoi University of Science, Hanoi, Vietnam
oUniversità di Padova, Padova, Italy
pUniversità di Pisa, Pisa, Italy
qUniversità degli Studi di Milano, Milano, Italy
rUniversità di Urbino, Urbino, Italy
sUniversità della Basilicata, Potenza, Italy
tScuola Normale Superiore, Pisa, Italy
uUniversità di Modena e Reggio Emilia, Modena, Italy
vMSU - Iligan Institute of Technology (MSU-IIT), Iligan, Philippines
wNovosibirsk State University, Novosibirsk, Russia
xNational Research University Higher School of Economics, Moscow, Russia
ySezione INFN di Trieste, Trieste, Italy
zEscuela Agrícola Panamericana, San Antonio de Oriente, Honduras
aaSchool of Physics and Information Technology, Shaanxi Normal University
(SNNU), Xi’an, China
abPhysics and Micro Electronic College, Hunan University, Changsha City, China
†Deceased