EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)

 CERN-EP-2016-133 LHCb-PAPER-2016-013 8 August 2016

Measurement of the $C\\!P$ asymmetry in ${B}^{0}_{s}$–${\kern
3.73305pt\overline{\kern-3.73305ptB}{}}{}^{0}_{s}$ mixing

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

The ${C\\!P}$ asymmetry in the mixing of ${{B}^{0}_{s}}$ and ${{\kern
1.79993pt\overline{\kern-1.79993ptB}{}}{}^{0}_{s}}$ mesons is measured in
proton–proton collision data corresponding to an integrated luminosity of
$3.0\mbox{\,fb}^{-1}$, recorded by the LHCb experiment at centre-of-mass
energies of 7 and 8$\mathrm{\,Te\kern-1.00006ptV}$. Semileptonic
${{B}^{0}_{s}}$ and ${{\kern
1.79993pt\overline{\kern-1.79993ptB}{}}{}^{0}_{s}}$ decays are studied in the
inclusive mode
${{D}^{\mp}_{s}}{\mu^{\pm}}\shortstack{{\scalebox{0.8}{(\rule[2.15277pt]{12.50002pt}{0.51212pt})}}
\\\ [-.7ex] {$\nu$}}_{\kern-1.20552pt\mu}X$ with the ${{D}^{\mp}_{s}}$ mesons
reconstructed in the ${{K}^{+}}{{K}^{-}}{{\pi}^{\mp}}$ final state. Correcting
the observed charge asymmetry for detection and background effects, the
$C\\!P$ asymmetry is found to be $a_{\rm sl}^{s}=(0.39\pm 0.26\pm 0.20)\%$,
where the first uncertainty is statistical and the second systematic. This is
the most precise measurement of $a_{\rm sl}^{s}$ to date. It is consistent
with the prediction from the Standard Model and will constrain new models of
particle physics.

Published in Phys. Rev. Lett. 117 (2016), 061803

© CERN on behalf of the LHCb collaboration, licence CC-BY-4.0.

When neutral $B$ mesons evolve in time they can change into their own
antiparticles. This quantum-mechanical phenomenon is known as mixing and
occurs in both neutral $B$ meson systems, ${B}^{0}$ and ${B}^{0}_{s}$, where
$B$ is used to refer to either system. In this mixing process, the $C\\!P$
(charge-parity) symmetry is broken if the probability for a $B$ meson to
change into a $\kern 1.79993pt\overline{\kern-1.79993ptB}{}$ meson is
different from the probability for the reverse process. This effect can be
measured by studying decays into flavour-specific final states,
${B}\rightarrow f$, such that ${{\kern
1.79993pt\overline{\kern-1.79993ptB}{}}}\rightarrow f$ transitions can only
occur through the mixing process ${{\kern
1.79993pt\overline{\kern-1.79993ptB}{}}}\rightarrow{B}\rightarrow f$. Such
processes include semileptonic $B$ decays, as the charge of the lepton
identifies the flavour of the $B$ meson at the time of its decay. The
magnitude of the $C\\!P$-violating asymmetry in $B$ mixing can be
characterized by the semileptonic asymmetry $a_{\rm sl}$. This is defined in
terms of the partial decay rates, $\Gamma$, to semileptonic final states as

$a_{\rm sl}\equiv\frac{\Gamma({{\kern
1.79993pt\overline{\kern-1.79993ptB}{}}}\rightarrow
f)-\Gamma({B}\rightarrow\bar{f})}{\Gamma({{\kern
1.79993pt\overline{\kern-1.79993ptB}{}}}\rightarrow
f)+\Gamma({B}\rightarrow\bar{f})}\approx\frac{\Delta\Gamma}{{\Delta
m}}\tan\phi_{12}\ ,$ (1)

where $\Delta m$ ($\Delta\Gamma$) is the difference in mass (decay width)
between the mass eigenstates of the ${B}$ system and $\phi_{12}$ is a
$C\\!P$-violating phase [1]. In the Standard Model (SM), the asymmetry is
predicted to be as small as $a_{\rm sl}^{d}=(-4.7\pm 0.6)\times 10^{-4}$ in
the ${B}^{0}$ system and $a_{\rm sl}^{s}=(2.22\pm 0.27)\times 10^{-5}$ in the
${B}^{0}_{s}$ system [1, 2]. However, these values may be enhanced by non-SM
contributions to the mixing process [3].

Measurements of $a_{\rm sl}$ have led to an inconclusive picture. In 2010, the
D0 collaboration reported an anomalous charge asymmetry in the inclusive
production rates of like-sign dimuons [4], which is sensitive to a combination
of $a_{\rm sl}^{d}$ and $a_{\rm sl}^{s}$. Their most recent study shows a
discrepancy with SM predictions of about three standard deviations [5]. The
current experimental world averages, excluding the anomalous D0 result, are
$a_{\rm sl}^{d}=(0.01\pm 0.20)\%$ and $a_{\rm sl}^{s}=(-0.48\pm 0.48)\%$ [6],
compatible with both the SM predictions and the D0 measurement. The
measurement of $a_{\rm sl}^{s}$ presented in this letter is based on data
recorded by LHCb in 2011 and 2012, corresponding to an integrated luminosity
of 3.0$\mbox{\,fb}^{-1}$. It supersedes the previous LHCb measurement [7],
which used the 1.0$\mbox{\,fb}^{-1}$ data sample taken in 2011. Semileptonic
decays ${{B}^{0}_{s}}\rightarrow{{D}^{-}_{s}}{\mu^{+}}{{\nu}_{\mu}}X$, where
$X$ represents any number of particles, are reconstructed inclusively in
${{D}^{-}_{s}}{\mu^{+}}$. Charge-conjugate modes are implied throughout,
except in the definitions of charge asymmetry. The ${D}^{-}_{s}$ meson is
reconstructed in the ${{K}^{+}}{{K}^{-}}{{\pi}^{-}}$ final state. This
analysis extends the previous LHCb measurement, which considered only
${{D}^{-}_{s}}\rightarrow\phi{{\pi}^{-}}$ decays, by including all possible
${D}^{-}_{s}$ decays to the ${{K}^{+}}{{K}^{-}}{{\pi}^{-}}$ final state.

Starting from a sample with equal numbers of ${B}^{0}_{s}$ and ${\kern
1.79993pt\overline{\kern-1.79993ptB}{}}{}^{0}_{s}$ mesons, $a_{\rm sl}^{s}$
can be measured without determining (tagging) the initial flavour. The raw
asymmetry of observed ${D}^{-}_{s}$ $\mu^{+}$ and ${D}^{+}_{s}$ $\mu^{-}$
candidates, integrated over ${B}^{0}_{s}$ decay time, is

$\displaystyle A_{\rm
raw}=\frac{N({{D}^{-}_{s}}{\mu^{+}})-N({{D}^{+}_{s}}{\mu^{-}})}{N({{D}^{-}_{s}}{\mu^{+}})+N({{D}^{+}_{s}}{\mu^{-}})}\
.$ (2)

The high oscillation frequency $\Delta m_{{s}}$ reduces the effect of the
small asymmetry in the production rates between ${B}^{0}_{s}$ and ${\kern
1.79993pt\overline{\kern-1.79993ptB}{}}{}^{0}_{s}$ mesons in $pp$ collisions
by a factor $10^{-3}$ [7, 8]. Neglecting corrections, the untagged, time-
integrated asymmetry is $A_{\rm raw}=a_{\rm sl}^{s}/2$, where the factor two
reduction compared to the tagged asymmetry in Eq. 1 comes from the summation
over mixed and unmixed decays. The tagged asymmetry would actually suffer from
a larger reduction because of the tagging efficiency [9, 10]. The unmixed
decays have zero asymmetry due to $C\\!PT$ symmetry. The raw asymmetry is
still affected by possible differences in detection efficiency for the two
charge-conjugate final states and by backgrounds from other $b$-hadron decays
to ${{D}^{-}_{s}}{\mu^{+}}X$. Hence, $a_{\rm sl}^{s}$ is calculated as

$\displaystyle a_{\rm sl}^{s}=\frac{2}{1-f_{\rm bkg}}(A_{\rm raw}-A_{\rm
det}-f_{\rm bkg}A_{\rm bkg})\ ,$ (3)

where $A_{\rm det}$ is the detection asymmetry, which is assessed from data
using calibration samples, $f_{\rm bkg}$ is the fraction of $b$-hadron
background and $A_{\rm bkg}$ the background asymmetry.

The LHCb detector is a single-arm forward spectrometer designed for the study
of particles containing $b$ or $c$ quarks [11, 12]. A high-precision tracking
system with a dipole magnet measures the momentum ($p$) and impact parameter
(IP) of charged particles. The IP is defined as the distance of closest
approach between the track and any primary proton–proton interaction and is
used to distinguish between ${D}^{-}_{s}$ mesons from $B$ decays and
${D}^{-}_{s}$ mesons promptly produced in the primary interaction. The regular
reversal of the magnet polarity allows a quantitative assessment of detector-
induced charge asymmetries. Different types of charged particles are
distinguished using particle identification (PID) information from two ring-
imaging Cherenkov detectors, an electromagnetic calorimeter, a hadronic
calorimeter and a muon system. Online event selection is performed by a two-
stage trigger. For this analysis, the first (hardware) stage selects muons in
the muon system; the second (software) stage applies a full event
reconstruction. Here the events are first selected by the presence of the muon
or one of the hadrons from the ${D}^{-}_{s}$ decay, after which a combination
of the decay products is required to be consistent with the topological
signature of a $b$-hadron decay. Simulated events are produced using the
software described in Refs. [13, *Sjostrand:2007gs, 15, 16, 17,
*Agostinelli:2002hh, 19].

Different intermediate states, clearly visible in the Dalitz plot shown in
Fig. 1, contribute to the three-body
${{D}^{-}_{s}}\rightarrow{{K}^{+}}{{K}^{-}}{{\pi}^{-}}$ decays. Three disjoint
regions are defined, which have different levels of background. The $\phi\pi$
region is the cleanest and is selected by requiring the reconstructed
${K}^{+}$ ${K}^{-}$ mass to be within $\pm
20{\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$ of the known $\phi$ mass. The
$K^{*}K$ region is selected by requiring the reconstructed ${K}^{+}$
${\pi}^{-}$ mass to be within $\pm 90{\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$
of the known $K^{*}(892)^{0}$ mass. The remaining ${D}^{-}_{s}$ candidates are
included in the non-resonant (NR) region, which also covers other intermediate
states [20].

Figure 1: Dalitz plot of the
${{D}^{\mp}_{s}}\rightarrow{{K}^{\pm}}{{K}^{\mp}}{{\pi}^{\mp}}$ decay for
selected ${{D}^{\mp}_{s}}\mu^{\pm}$ candidates, with the three selection
regions indicated. To suppress combinatorial background, a narrow invariant
mass window, between 1950 and 1990${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$,
is required for the ${D}^{\mp}_{s}$ candidates in this plot.

The ${D}^{-}_{s}$ candidates are reconstructed from three charged tracks, and
then a muon track with opposite charge is added. All four tracks are required
to have a good quality track fit and significant IP. The contribution from
prompt ${D}^{-}_{s}$ background is suppressed to a negligible level by
imposing a lower bound on the IP of the ${D}^{-}_{s}$ candidates. To ensure a
good overlap with the calibration samples, minimum momenta of 2, 5 and
6${\mathrm{\,Ge\kern-1.00006ptV\\!/}c}$ and minimum transverse momenta,
$p_{\mathrm{T}}$, of 300, 400 and 1200${\mathrm{\,Me\kern-1.00006ptV\\!/}c}$
are required for the pions, kaons and muons, respectively. To suppress
background, kaon and pion candidates are required to be positively identified
by the PID system. Candidates are selected by requiring a good quality of the
${D}^{-}_{s}$ and ${B}^{0}_{s}$ decay vertices. A source of background arises
from ${D}^{-}_{s}$ candidates where one of the three decay particles is
misidentified. The main contributions are from ${{\kern
1.00006pt\overline{\kern-1.00006pt\mathchar
28931\relax}}{}^{-}_{c}}\rightarrow{{K}^{+}}{\overline{p}}{{\pi}^{-}}$,
${{D}^{-}}\rightarrow{{K}^{+}}{{\pi}^{-}}{{\pi}^{-}}$,
${{J\mskip-3.0mu/\mskip-2.0mu\psi\mskip 2.0mu}}X$, and misidentified or
partially reconstructed multibody $D$ decays, all originating from
semileptonic $b$-hadron decays. They are suppressed to a negligible level by
specific vetoes, which apply tight PID requirements in a small window of
invariant mass of the corresponding particle combination. These vetoes are
optimized separately for each Dalitz plot region. To check that this does not
introduce additional asymmetries, these selections are applied to control
samples of promptly produced ${D}^{-}_{s}$ mesons. The asymmetries are found
to be consistent between the Dalitz regions.

The ${D}^{-}_{s}$ $\mu^{+}$ signal yields are obtained from fits to the
${{K}^{+}}{{K}^{-}}{{\pi}^{-}}$ invariant mass distributions. These yields
contain contributions from backgrounds that also peak at the ${D}^{-}_{s}$
mass, originating from other $b$-hadron decays into ${D}^{-}_{s}$ mesons and
muons. Simulation studies indicate that these peaking backgrounds are mainly
composed of $b$-hadron decays to ${{D}^{-}_{s}}X_{c}X$, where the
${D}^{-}_{s}$ meson originates from a ${b}\rightarrow{c}{\overline{c}}{s}$
transition, and $X_{c}$ is a charmed hadron decaying semileptonically.

An example of such a background is ${{{B}^{-}}}\rightarrow{{D}^{-}_{s}}{{\kern
1.99997pt\overline{\kern-1.99997ptD}{}}{}^{0}}X$. Other, smaller contributors
are ${{{B}^{+}}}\rightarrow{{D}^{-}_{s}}{{K}^{+}}{\mu^{+}}{{\nu}_{\mu}}X$ and
${{B}^{0}}\rightarrow{{D}^{-}_{s}}{{K}^{0}_{\mathrm{\scriptscriptstyle
S}}}{\mu^{+}}{{\nu}_{\mu}}X$ decays. All of these peaking backgrounds have
more missing particles than the
${{B}^{0}_{s}}\rightarrow{{D}^{-}_{s}}{\mu^{+}}{{\nu}_{\mu}}X$ signal decay.
Their contribution is reduced by requiring the corrected ${B}^{0}_{s}$ mass,
defined as
${m_{\text{corr}}}\equiv\sqrt{m^{2}+\mbox{$p_{\mathrm{T}}$}^{2}}+\mbox{$p_{\mathrm{T}}$}$,
to be larger than $4200{\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$, where $m$ is
the ${{D}^{-}_{s}}{\mu^{+}}$ invariant mass and $p_{\mathrm{T}}$ the
${{D}^{-}_{s}}{\mu^{+}}$ momentum transverse to the line connecting the
primary and ${B}^{0}_{s}$ decay vertices.

The estimates of $f_{\rm bkg}$ and $A_{\rm bkg}$ are based on known branching
fractions [20], selection efficiencies and background asymmetries, using a
similar approach as in the previous measurement [7]. The reconstruction and
selection efficiencies of the backgrounds relative to the signal efficiency
are determined from simulation. The total background asymmetry is given by the
sum of all contributions as $f_{\rm bkg}A_{\rm bkg}\equiv\sum_{i}f_{\rm
bkg}^{i}A_{\rm bkg}^{i}$. The background asymmetries mainly originate from the
production asymmetries of $b$ hadrons. The production asymmetry between
${{B}^{+}}$ and ${{B}^{-}}$ mesons is $A_{\rm bkg}({{B}^{+}})=(-0.6\pm
0.6)\%$, obtained from the observed asymmetry in
${{{B}^{+}}}\rightarrow{{J\mskip-3.0mu/\mskip-2.0mu\psi\mskip
2.0mu}}{{K}^{+}}$ decays [21], after correcting for the kaon detection
asymmetry and the direct $C\\!P$ asymmetry [20]. For the ${B}^{0}$ background,
there are contributions from the production asymmetry and from $a_{\rm
sl}^{d}$ [22]. Both asymmetries are diluted when integrating over the
${B}^{0}$ decay time, resulting in $A_{\rm bkg}({{B}^{0}})=(-0.18\pm 0.13)\%$.
The production asymmetry in the ${\mathchar 28931\relax}^{0}_{b}$ backgrounds
is estimated based on the combined $C\\!P$ and production asymmetry measured
in ${{\mathchar
28931\relax}^{0}_{b}}\rightarrow{{J\mskip-3.0mu/\mskip-2.0mu\psi\mskip
2.0mu}}p^{+}{{K}^{-}}$ decays [23]. The direct $C\\!P$ asymmetry in this decay
mode is estimated to be $(-0.6\pm 0.3)\%$, using the measurements in Ref. [24]
and the method proposed in Ref. [25]. Subtracting this from the combined
asymmetry [23] results in $A_{\rm bkg}({{\mathchar
28931\relax}^{0}_{b}})=(+0.5\pm 0.8)\%$. The overall peaking background
fraction is $f_{\rm bkg}=(18.4\pm 6.0)\%$ and the correction for the
background asymmetry is $f_{\rm bkg}A_{\rm bkg}=(-0.023\pm 0.031)\%$.

The ${{K}^{+}}{{K}^{-}}{{\pi}^{\mp}}$ mass distributions are shown in Fig. 2,
with the fit results superimposed. The ${D}^{\mp}_{s}$ $\mu^{\pm}$ yields are
found to be $899\times 10^{3}$ in the $\phi\pi$ region, $413\times 10^{3}$ in
the $K^{*}K$ region, and $280\times 10^{3}$ in the NR region. Extended maximum
likelihood fits are made separately for the three Dalitz regions, for the two
magnet polarities, and the two data-taking periods (2011 and 2012). To
accurately determine the background shape from random combinations of
${{K}^{+}}{{K}^{-}}{{\pi}^{-}}$ candidates, a wide mass window between 1800
and 2047${\mathrm{\,Me\kern-1.00006ptV\\!/}c^{2}}$ is used, which includes the
Cabibbo-suppressed ${{D}^{-}}\rightarrow{{K}^{+}}{{K}^{-}}{{\pi}^{-}}$ decay.
Both peaks are modelled with a double-sided Hypatia function [26]. The tail
parameters of this function are determined for each Dalitz region by a fit to
the combined data sets for all magnet polarities and data-taking periods, and
subsequently fixed in the twelve individual mass fits. A systematic
uncertainty is assigned to account for fixing these parameters. The
combinatorial background is modelled with a second-order polynomial. A
simultaneous fit to the $m({{K}^{+}}{{K}^{-}}{{\pi}^{-}})$ and
$m({{K}^{+}}{{K}^{-}}{{\pi}^{+}})$ distributions is performed. All signal
parameters except the mean masses and signal yields are shared between the
${D}^{-}_{s}$ and ${D}^{+}_{s}$ candidates. All background parameters vary
independently in the fit to allow for any asymmetry in the combinatorial
background. Possible biases from the fit model are studied by generating
invariant mass distributions with the signal component described by a double
Gaussian function with power-law tails on both sides, and subsequently
applying the fit with the default Hypatia shape. The change in the value of
$A_{\rm raw}$ is assigned as a systematic uncertainty.

Figure 2: Distributions of ${{K}^{+}}{{K}^{-}}{{\pi}^{\mp}}$ mass in the three
Dalitz plot regions, summed over both magnet polarities and data-taking
periods. Overlaid is the result of the fit, with signal and combinatorial
background components as indicated in the legend.

Asymmetries are averaged as follows. For each magnet polarity and data-taking
period, the weighted average of the asymmetries of the three Dalitz regions is
taken. Then the arithmetic average for the two magnet polarities is taken to
minimize possible residual detection asymmetries [7]. Finally, a weighted
average is made over the two data-taking periods. The resulting raw asymmetry
is $A_{\rm raw}=(0.11\pm 0.09)\%$.

The asymmetry $A_{\rm det}$, arising from the difference in detection
efficiencies between the ${D}^{-}_{s}$ $\mu^{+}$ and ${D}^{+}_{s}$ $\mu^{-}$
candidates, is determined using calibration samples. The asymmetry is split up
as

$A_{\rm det}={A_{\text{track}}}+{A_{\text{PID}}}+{A_{\text{trig}}}\ ,$ (4)

where the individual contributions are described below. For each calibration
sample, event weights are applied to match the three-momentum distributions of
the calibration particles to those of the signal decays. The weights are
determined in bins of the distributions of momenta and angles. Alternative
binning schemes are used to assess the systematic uncertainties due to the
weighting procedure.

The track reconstruction asymmetry, $A_{\text{track}}$, is split into a
contribution, $A_{\text{track}}({{{K}^{+}}{{K}^{-}}})$, associated with the
reconstruction of the ${{K}^{+}}{{K}^{-}}$ pair and a contribution,
$A_{\text{track}}({{{\pi}^{-}}{\mu^{+}}})$, associated with the
${{\pi}^{-}}{\mu^{+}}$ pair. The track reconstruction efficiency for single
kaons suffers from a sizeable difference between ${K}^{+}$ and ${K}^{-}$
cross-sections with the detector material, which depends on the kaon momentum.
This asymmetry largely cancels in $A_{\text{track}}({{{K}^{+}}{{K}^{-}}})$,
due to the similar kinematic distributions of the positive and negative kaons.
The kaon asymmetry is calculated using prompt
${{D}^{-}}\rightarrow{{K}^{+}}{{\pi}^{-}}{{\pi}^{-}}$ and
${{D}^{-}}\rightarrow{{K}^{0}_{\mathrm{\scriptscriptstyle S}}}{{\pi}^{-}}$
decays, similarly to Refs. [27, 22]. For pions and muons, the charge asymmetry
due to interactions in the detector material is assumed to be negligible, and
a systematic uncertainty is assigned for this assumption [22]. Effects from
the track reconstruction algorithms and detector acceptance, combined with a
difference in kinematic distributions between pions and muons, can result in a
charge asymmetry. It is assessed here with two methods. The first method
measures the track reconstruction efficiency using samples of partially
reconstructed ${{J\mskip-3.0mu/\mskip-2.0mu\psi\mskip
2.0mu}}\rightarrow{\mu^{+}}{\mu^{-}}$ decays as described in Ref. [28]. The
second method uses fully and partially reconstructed
${{D}^{*-}}\rightarrow{{\kern
1.99997pt\overline{\kern-1.99997ptD}{}}{}^{0}}({{K}^{+}}{{\pi}^{-}}{{\pi}^{+}}{{\pi}^{-}}){{\pi}^{-}}$
decays as described in Ref. [29]. The final value of
$A_{\text{track}}({{{\pi}^{-}}{\mu^{+}}})$ is obtained as the weighted average
from the two methods. The systematic uncertainty on this number includes a
small effect from differences in the detector acceptance for positive and
negative particles.

The asymmetry induced by the PID requirements, $A_{\text{PID}}$, is determined
using large samples of
${{D}^{*+}}\rightarrow{{D}^{0}}({{K}^{-}}{{\pi}^{+}}){{\pi}^{+}}$ and
${{J\mskip-3.0mu/\mskip-2.0mu\psi\mskip 2.0mu}}\rightarrow{\mu^{+}}{\mu^{-}}$
decays. The ${D}^{*+}$ charge identifies the kaon and the pion of the
${D}^{0}$ decay without the use of PID requirements, which is then used to
determine the PID efficiencies and corresponding charge asymmetries.

The asymmetry induced by the trigger, $A_{\text{trig}}$, is split into
contributions from the muon hardware trigger and from the software trigger.
The first, $A_{\text{trig}}({\text{hardware}})$, is assessed using samples of
${{J\mskip-3.0mu/\mskip-2.0mu\psi\mskip 2.0mu}}\rightarrow{\mu^{+}}{\mu^{-}}$
decays in data. The second, $A_{\text{trig}}({\text{software}})$, is mainly
caused by the trigger requirements on the muon or one of the hadrons from the
${D}^{-}_{s}$ decay. The asymmetry from the muon software trigger is
determined in a similar fashion to that from the hardware trigger. The
asymmetry due to the trigger requirement on the hadrons is determined using
samples of prompt ${{D}^{-}_{s}}\rightarrow{{K}^{+}}{{K}^{-}}{{\pi}^{-}}$
decays that have been triggered by other particles in the event. The combined
asymmetry takes into account the overlap between the two triggers.

The measured values of all detection asymmetries with their statistical and
systematic uncertainties are shown in Table 1. The overall corrections are
small and compatible with zero. In contrast, corrections for separate magnet
polarities are more significant (at most 1.1% in 2011 and 0.3% in 2012), as
expected for most of the detector-induced charge asymmetries. The corrections
for the detection asymmetries are almost fully correlated between the Dalitz
regions.

Table 1: Overview of contributions in the determination of $a_{\rm sl}^{s}$, averaged over Dalitz plot regions, magnet polarities and data taking periods, with their statistical and systematic uncertainties. All numbers are in percent. The central value of $a_{\rm sl}^{s}$ is calculated according to Eq. 3. The uncertainties are added in quadrature and multiplied by $2/(1-f_{\rm bkg})$, which is the same for all twelve subsamples, to obtain the uncertainties on $a_{\rm sl}^{s}$. Source | Value | Stat. uncert. | Syst. uncert. |
---|---|---|---|---
$A_{\rm raw}$ |  0.11 | 0.09 | $0.02$ |
$-$$A_{\text{track}}({{{K}^{+}}{{K}^{-}}})$ | $\phantom{-}0.01$ | $0.00$ | $0.03$ |
$-$$A_{\text{track}}({{{\pi}^{-}}{\mu^{+}}})$ | $\phantom{-}0.01$ | $0.05$ | $0.04$ |
$-$$A_{\text{PID}}$ | $-0.01$ | $0.02$ | $0.03$ |
$-$$A_{\text{trig}}({\text{hardware}})$ | $\phantom{-}0.03$ | $0.02$ | $0.02$ |
$-$$A_{\text{trig}}({\text{software}})$ | $\phantom{-}0.00$ | $0.01$ | $0.02$ |
$-$$f_{\rm bkg}$ $A_{\rm bkg}$ | $\phantom{-}0.02$ | $-$ | $0.03$ | $+$
$(1-f_{\rm bkg})a_{\rm sl}^{s}/2$ | $\phantom{-}0.16$ | 0.11 | 0.08 |
$2/(1-f_{\rm bkg})$ | $\phantom{-}2.45$ | $-$ | 0.18 | $\times$
$a_{\rm sl}^{s}$ |  0.39 | 0.26 | 0.20 |

The previous analysis, based on $1.0\mbox{\,fb}^{-1}$, used only candidates in
the $\phi\pi$ region of the Dalitz plot, with different selection criteria,
and used a different fit method to determine the signal yields [7]. A more
stringent selection resulted in a cleaner signal sample, but with roughly 30%
fewer signal candidates in the $\phi\pi$ region. As a cross check, the
approach of the previous analysis is repeated on the full
$3.0\mbox{\,fb}^{-1}$ data sample and the result is compatible within one
standard deviation.

Figure 3: Overview of the most precise measurements of $a_{\rm sl}^{d}$ and
$a_{\rm sl}^{s}$. The horizontal and vertical bands indicate the naive
averages of pure $a_{\rm sl}^{s}$ and $a_{\rm sl}^{d}$ measurements [30, 31,
32, 33, 22, 34]. The yellow ellipse represents the D0 dimuon measurement with
${\Delta\Gamma_{{d}}}/{\Gamma_{{d}}}$ set to its SM expectation value [5]. The
error bands and contours correspond to 68% confidence level.

The twelve values of $a_{\rm sl}^{s}$ for each Dalitz region, polarity and
data-taking period are consistent with each other. The combined result, taking
into account all correlations, is

$a_{\rm sl}^{s}=(0.39\pm 0.26\pm 0.20)\%\ ,$

where the first uncertainty is statistical, originating from the size of the
signal and calibration samples, and the second systematic. There is a small
correlation coefficient of $+0.13$ between this measurement and the LHCb
measurement of $a_{\rm sl}^{d}$ [22]. The correlation mainly originates from
the muon detection asymmetry and from the effect of $a_{\rm sl}^{d}$, due to
${B}^{0}$ background, on the measurement of $a_{\rm sl}^{s}$. Figure 3
displays an overview of the most precise measurements of $a_{\rm sl}^{d}$ and
$a_{\rm sl}^{s}$ [30, 31, 32, 33, 22, 34, 5]. The simple averages of pure
$a_{\rm sl}$ measurements, including the present $a_{\rm sl}^{s}$ result and
accounting for the small correlation from LHCb, are found to be $a_{\rm
sl}^{d}=(0.02\pm 0.20)\%$ and $a_{\rm sl}^{s}=(0.17\pm 0.30)\%$ with a
correlation of $+0.07$. In combination, these two averages are marginally
compatible with the D0 dimuon result ($p=0.5\%$) shown in Fig. 3. In summary,
the determination of $a_{\rm sl}^{s}$ presented in this letter is the most
precise to date. It shows no evidence for new physics effects and will serve
to restrict models beyond the SM.

## 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); NSFC
(China); CNRS/IN2P3 (France); BMBF, DFG and MPG (Germany); INFN (Italy); FOM
and NWO (The Netherlands); MNiSW and NCN (Poland); MEN/IFA (Romania); MinES
and FANO (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), Conseil Général de Haute-
Savoie, Labex ENIGMASS and OCEVU, Région Auvergne (France), RFBR and Yandex
LLC (Russia), GVA, XuntaGal and GENCAT (Spain), Herchel Smith Fund, The Royal
Society, Royal Commission for the Exhibition of 1851 and the Leverhulme Trust
(United Kingdom).

## References

  * [1] A. Lenz and U. Nierste, _Theoretical update of $B_{s}-\overline{B}_{s}$ mixing_, JHEP 06 (2007) 072, arXiv:hep-ph/0612167
  * [2] M. Artuso, G. Borissov, and A. Lenz, _$C\\!P$ violation in the ${B}^{0}_{s}$ system_, arXiv:1511.09466
  * [3] A. Lenz et al., _Constraints on new physics in ${B}-{{\kern 1.79993pt\overline{\kern-1.79993ptB}{}}}$ mixing in the light of recent LHCb data_, Phys. Rev. D86 (2012) 033008, arXiv:1203.0238
  * [4] D0 collaboration, V. M. Abazov et al., _Evidence for an anomalous like-sign dimuon charge asymmetry_ , Phys. Rev. Lett. 105 (2010) 081801, arXiv:1007.0395
  * [5] D0 collaboration, V. M. Abazov et al., _Study of $C\\!P$-violating charge asymmetries of single muons and like-sign dimuons in $p{\overline{p}}$ collisions_, Phys. Rev. D89 (2014) 012002, arXiv:1310.0447
  * [6] Heavy Flavor Averaging Group, Y. Amhis et al., _Averages of $b$-hadron, $c$-hadron, and $\tau$-lepton properties as of summer 2014_, arXiv:1412.7515, updated results and plots available at http://www.slac.stanford.edu/xorg/hfag/
  * [7] LHCb collaboration, R. Aaij et al., _Measurement of the flavour-specific $C\\!P$-violating asymmetry $a_{\mathrm{sl}}^{s}$ in $B_{s}^{0}$ decays_, Phys. Lett. B728 (2014) 607, arXiv:1308.1048
  * [8] LHCb collaboration, R. Aaij et al., _Measurement of the $\overline{B}^{0}$–$B^{0}$ and $\overline{B}^{0}_{s}$–$B^{0}_{s}$ production asymmetries in $pp$ collisions at $\sqrt{s}=7$ TeV_, Phys. Lett. B739 (2014) 218, arXiv:1408.0275
  * [9] LHCb collaboration, R. Aaij et al., _Opposite-side flavour tagging of $B$ mesons at the LHCb experiment_, Eur. Phys. J. C72 (2012) 2022, arXiv:1202.4979
  * [10] LHCb collaboration, R. Aaij et al., _A new algorithm for identifying the flavour of ${B}^{0}_{s}$ mesons at LHCb_, JINST 11 (2016) P05010, arXiv:1602.07252
  * [11] LHCb collaboration, A. A. Alves Jr. et al., _The LHCb detector at the LHC_, JINST 3 (2008) S08005
  * [12] LHCb collaboration, R. Aaij et al., _LHCb detector performance_ , Int. J. Mod. Phys. A30 (2015) 1530022, arXiv:1412.6352
  * [13] T. Sjöstrand, S. Mrenna, and P. Skands, _PYTHIA 6.4 physics and manual_ , JHEP 05 (2006) 026, arXiv:hep-ph/0603175
  * [14] T. Sjöstrand, S. Mrenna, and P. Skands, _A brief introduction to PYTHIA 8.1_ , Comput. Phys. Commun. 178 (2008) 852, arXiv:0710.3820
  * [15] I. Belyaev et al., _Handling of the generation of primary events in Gauss, the LHCb simulation framework_ , J. Phys. Conf. Ser. 331 (2011) 032047
  * [16] D. J. Lange, _The EvtGen particle decay simulation package_ , Nucl. Instrum. Meth. A462 (2001) 152
  * [17] Geant4 collaboration, J. Allison et al., _Geant4 developments and applications_ , IEEE Trans. Nucl. Sci. 53 (2006) 270
  * [18] Geant4 collaboration, S. Agostinelli et al., _Geant4: A simulation toolkit_ , Nucl. Instrum. Meth. A506 (2003) 250
  * [19] M. Clemencic et al., _The LHCb simulation application, Gauss: Design, evolution and experience_, J. Phys. Conf. Ser. 331 (2011) 032023
  * [20] Particle Data Group, K. A. Olive et al., _Review of particle physics_ , Chin. Phys. C38 (2014) 090001, and 2015 update
  * [21] LHCb collaboration, R. Aaij et al., _Measurement of $C\\!P$ asymmetries in the decays $B^{0}\rightarrow K^{*0}\mu^{+}\mu^{-}$ and $B^{+}\rightarrow K^{+}\mu^{+}\mu^{-}$_, JHEP 09 (2014) 177, arXiv:1408.0978
  * [22] LHCb collaboration, R. Aaij et al., _Measurement of the semileptonic $C\\!P$ asymmetry in $B^{0}$–$\overline{B}^{0}$ mixing_, Phys. Rev. Lett. 114 (2015) 041601, arXiv:1409.8586
  * [23] LHCb collaboration, R. Aaij et al., _Study of the productions of $\Lambda_{b}^{0}$ and ${\kern 1.79993pt\overline{\kern-1.79993ptB}{}}{}^{0}$ hadrons in $pp$ collisions and first measurement of the $\Lambda_{b}^{0}\rightarrow{{J\mskip-3.0mu/\mskip-2.0mu\psi\mskip 2.0mu}}pK^{-}$ branching fraction_, Chin. Phys. C40 (2015) 011001, arXiv:1509.00292
  * [24] LHCb collaboration, R. Aaij et al., _Observation of the $\Lambda_{b}^{0}\rightarrow J/\psi p\pi^{-}$ decay_, JHEP 07 (2014) 103, arXiv:1406.0755
  * [25] K. De Bruyn and R. Fleischer, _A roadmap to control penguin effects in ${{B}^{0}}\rightarrow{{J\mskip-3.0mu/\mskip-2.0mu\psi\mskip 2.0mu}}{{K}^{0}_{\mathrm{\scriptscriptstyle S}}}$ and ${{B}^{0}_{s}}\rightarrow{{J\mskip-3.0mu/\mskip-2.0mu\psi\mskip 2.0mu}}\phi$_, JHEP 03 (2015) 145, arXiv:1412.6834
  * [26] D. Martinez Santos and F. Dupertuis, _Mass distributions marginalized over per-event errors_ , Nucl. Instrum. Meth. A764 (2014) 150, arXiv:1312.5000
  * [27] LHCb collaboration, R. Aaij et al., _Measurement of $C\\!P$ asymmetry in $D^{0}\rightarrow K^{-}K^{+}$ and $D^{0}\rightarrow\pi^{-}\pi^{+}$ decays_, JHEP 07 (2014) 041, arXiv:1405.2797
  * [28] LHCb collaboration, R. Aaij et al., _Measurement of the track reconstruction efficiency at LHCb_ , JINST 10 (2015) P02007, arXiv:1408.1251
  * [29] LHCb collaboration, R. Aaij et al., _Measurement of the $D_{s}^{+}$–$D_{s}^{-}$ production asymmetry in 7 TeV $pp$ collisions_, Phys. Lett. B713 (2012) 186, arXiv:1205.0897
  * [30] Belle collaboration, E. Nakano et al., _Charge asymmetry of same-sign dileptons in ${B}^{0}$-${\kern 1.79993pt\overline{\kern-1.79993ptB}{}}{}^{0}$ mixing_, Phys. Rev. D73 (2006) 112002, arXiv:hep-ex/0505017
  * [31] BaBar collaboration, J. P. Lees et al., _Search for $C\\!P$ violation in ${{B}^{0}}-{{\kern 1.79993pt\overline{\kern-1.79993ptB}{}}{}^{0}}$ mixing using partial reconstruction of ${{B}^{0}}\rightarrow D^{*-}X\ell^{+}\nu_{\ell}$ and a kaon tag_, Phys. Rev. Lett. 111 (2013) 101802, arXiv:1305.1575
  * [32] BaBar collaboration, J. P. Lees et al., _Study of $C\\!P$ asymmetry in ${{B}^{0}}-{{\kern 1.79993pt\overline{\kern-1.79993ptB}{}}{}^{0}}$ mixing with inclusive dilepton events_, Phys. Rev. Lett. 114 (2015) 081801, arXiv:1411.1842
  * [33] D0 collaboration, V. M. Abazov et al., _Measurement of the semileptonic charge asymmetry in $B^{0}$ meson mixing with the D0 detector_, Phys. Rev. D86 (2012) 072009, arXiv:1208.5813
  * [34] D0 collaboration, V. M. Abazov et al., _Measurement of the semileptonic charge asymmetry using $B_{s}^{0}\rightarrow D_{s}\mu X$ decays_, Phys. Rev. Lett. 110 (2013) 011801, arXiv:1207.1769

LHCb collaboration

R. Aaij39, B. Adeva38, M. Adinolfi47, Z. Ajaltouni5, S. Akar6, J. Albrecht10,
F. Alessio39, M. Alexander52, S. Ali42, G. Alkhazov31, P. Alvarez Cartelle54,
A.A. Alves Jr58, S. Amato2, S. Amerio23, Y. Amhis7, L. An40, L. Anderlini18,
G. Andreassi40, M. Andreotti17,g, J.E. Andrews59, R.B. Appleby55, O. Aquines
Gutierrez11, F. Archilli1, P. d’Argent12, J. Arnau Romeu6, A. Artamonov36, M.
Artuso60, E. Aslanides6, G. Auriemma26,s, M. Baalouch5, S. Bachmann12, J.J.
Back49, A. Badalov37, C. Baesso61, W. Baldini17, R.J. Barlow55, C. Barschel39,
S. Barsuk7, W. Barter39, V. Batozskaya29, V. Battista40, A. Bay40, L.
Beaucourt4, J. Beddow52, F. Bedeschi24, I. Bediaga1, L.J. Bel42, V. Bellee40,
N. Belloli21,i, K. Belous36, I. Belyaev32, E. Ben-Haim8, G. Bencivenni19, S.
Benson39, J. Benton47, A. Berezhnoy33, R. Bernet41, A. Bertolin23, M.-O.
Bettler39, M. van Beuzekom42, S. Bifani46, P. Billoir8, T. Bird55, A.
Birnkraut10, A. Bitadze55, A. Bizzeti18,u, T. Blake49, F. Blanc40, J. Blouw11,
S. Blusk60, V. Bocci26, T. Boettcher57, A. Bondar35, N. Bondar31,39, W.
Bonivento16, S. Borghi55, M. Borisyak67, M. Borsato38, F. Bossu7, M. Boubdir9,
T.J.V. Bowcock53, E. Bowen41, C. Bozzi17,39, S. Braun12, M. Britsch12, T.
Britton60, J. Brodzicka55, E. Buchanan47, C. Burr55, A. Bursche2, J.
Buytaert39, S. Cadeddu16, R. Calabrese17,g, M. Calvi21,i, M. Calvo Gomez37,m,
P. Campana19, D. Campora Perez39, L. Capriotti55, A. Carbone15,e, G.
Carboni25,j, R. Cardinale20,h, A. Cardini16, P. Carniti21,i, L. Carson51, K.
Carvalho Akiba2, G. Casse53, L. Cassina21,i, L. Castillo Garcia40, M.
Cattaneo39, Ch. Cauet10, G. Cavallero20, R. Cenci24,t, M. Charles8, Ph.
Charpentier39, G. Chatzikonstantinidis46, M. Chefdeville4, S. Chen55, S.-F.
Cheung56, V. Chobanova38, M. Chrzaszcz41,27, X. Cid Vidal38, G. Ciezarek42,
P.E.L. Clarke51, M. Clemencic39, H.V. Cliff48, J. Closier39, V. Coco58, J.
Cogan6, E. Cogneras5, V. Cogoni16,f, L. Cojocariu30, G. Collazuol23,o, P.
Collins39, A. Comerma-Montells12, A. Contu39, A. Cook47, S. Coquereau8, G.
Corti39, M. Corvo17,g, C.M. Costa Sobral49, B. Couturier39, G.A. Cowan51, D.C.
Craik51, A. Crocombe49, M. Cruz Torres61, S. Cunliffe54, R. Currie54, C.
D’Ambrosio39, E. Dall’Occo42, J. Dalseno47, P.N.Y. David42, A. Davis58, O. De
Aguiar Francisco2, K. De Bruyn6, S. De Capua55, M. De Cian12, J.M. De
Miranda1, L. De Paula2, P. De Simone19, C.-T. Dean52, D. Decamp4, M.
Deckenhoff10, L. Del Buono8, M. Demmer10, D. Derkach67, O. Deschamps5, F.
Dettori39, B. Dey22, A. Di Canto39, H. Dijkstra39, F. Dordei39, M. Dorigo40,
A. Dosil Suárez38, A. Dovbnya44, K. Dreimanis53, L. Dufour42, G. Dujany55, K.
Dungs39, P. Durante39, R. Dzhelyadin36, A. Dziurda39, A. Dzyuba31, N.
Déléage4, S. Easo50, U. Egede54, V. Egorychev32, S. Eidelman35, S.
Eisenhardt51, U. Eitschberger10, R. Ekelhof10, L. Eklund52, Ch. Elsasser41, S.
Ely60, S. Esen12, H.M. Evans48, T. Evans56, A. Falabella15, N. Farley46, S.
Farry53, R. Fay53, D. Ferguson51, V. Fernandez Albor38, F. Ferrari15,39, F.
Ferreira Rodrigues1, M. Ferro-Luzzi39, S. Filippov34, M. Fiore17,g, M.
Fiorini17,g, M. Firlej28, C. Fitzpatrick40, T. Fiutowski28, F. Fleuret7,b, K.
Fohl39, M. Fontana16, F. Fontanelli20,h, D.C. Forshaw60, R. Forty39, M.
Frank39, C. Frei39, M. Frosini18, J. Fu22,q, E. Furfaro25,j, C. Färber39, A.
Gallas Torreira38, D. Galli15,e, S. Gallorini23, S. Gambetta51, M. Gandelman2,
P. Gandini56, Y. Gao3, J. García Pardiñas38, J. Garra Tico48, L. Garrido37,
P.J. Garsed48, D. Gascon37, C. Gaspar39, L. Gavardi10, G. Gazzoni5, D.
Gerick12, E. Gersabeck12, M. Gersabeck55, T. Gershon49, Ph. Ghez4, S. Gianì40,
V. Gibson48, O.G. Girard40, L. Giubega30, K. Gizdov51, V.V. Gligorov8, D.
Golubkov32, A. Golutvin54,39, A. Gomes1,a, I.V. Gorelov33, C. Gotti21,i, M.
Grabalosa Gándara5, R. Graciani Diaz37, L.A. Granado Cardoso39, E. Graugés37,
E. Graverini41, G. Graziani18, A. Grecu30, P. Griffith46, L. Grillo12, B.R.
Gruberg Cazon56, O. Grünberg65, E. Gushchin34, Yu. Guz36, T. Gys39, C.
Göbel61, T. Hadavizadeh56, C. Hadjivasiliou60, G. Haefeli40, C. Haen39, S.C.
Haines48, S. Hall54, B. Hamilton59, X. Han12, S. Hansmann-Menzemer12, N.
Harnew56, S.T. Harnew47, J. Harrison55, J. He62, T. Head40, A. Heister9, K.
Hennessy53, P. Henrard5, L. Henry8, J.A. Hernando Morata38, E. van
Herwijnen39, M. Heß65, A. Hicheur2, D. Hill56, C. Hombach55, W. Hulsbergen42,
T. Humair54, M. Hushchyn67, N. Hussain56, D. Hutchcroft53, M. Idzik28, P.
Ilten57, R. Jacobsson39, A. Jaeger12, J. Jalocha56, E. Jans42, A. Jawahery59,
M. John56, D. Johnson39, C.R. Jones48, C. Joram39, B. Jost39, N. Jurik60, S.
Kandybei44, W. Kanso6, M. Karacson39, J.M. Kariuki47, S. Karodia52, M.
Kecke12, M. Kelsey60, I.R. Kenyon46, M. Kenzie39, T. Ketel43, E. Khairullin67,
B. Khanji21,39,i, C. Khurewathanakul40, T. Kirn9, S. Klaver55, K.
Klimaszewski29, S. Koliiev45, M. Kolpin12, I. Komarov40, R.F. Koopman43, P.
Koppenburg42, A. Kozachuk33, M. Kozeiha5, L. Kravchuk34, K. Kreplin12, M.
Kreps49, P. Krokovny35, F. Kruse10, W. Krzemien29, W. Kucewicz27,l, M.
Kucharczyk27, V. Kudryavtsev35, A.K. Kuonen40, K. Kurek29, T.
Kvaratskheliya32,39, D. Lacarrere39, G. Lafferty55,39, A. Lai16, D. Lambert51,
G. Lanfranchi19, C. Langenbruch49, B. Langhans39, T. Latham49, C. Lazzeroni46,
R. Le Gac6, J. van Leerdam42, J.-P. Lees4, A. Leflat33,39, J. Lefrançois7, R.
Lefèvre5, F. Lemaitre39, E. Lemos Cid38, O. Leroy6, T. Lesiak27, B.
Leverington12, Y. Li7, T. Likhomanenko67,66, R. Lindner39, C. Linn39, F.
Lionetto41, B. Liu16, X. Liu3, D. Loh49, I. Longstaff52, J.H. Lopes2, D.
Lucchesi23,o, M. Lucio Martinez38, H. Luo51, A. Lupato23, E. Luppi17,g, O.
Lupton56, A. Lusiani24, X. Lyu62, F. Machefert7, F. Maciuc30, O. Maev31, K.
Maguire55, S. Malde56, A. Malinin66, T. Maltsev35, G. Manca7, G. Mancinelli6,
P. Manning60, J. Maratas5, J.F. Marchand4, U. Marconi15, C. Marin Benito37, P.
Marino24,t, J. Marks12, G. Martellotti26, M. Martin6, M. Martinelli40, D.
Martinez Santos38, F. Martinez Vidal68, D. Martins Tostes2, L.M. Massacrier7,
A. Massafferri1, R. Matev39, A. Mathad49, Z. Mathe39, C. Matteuzzi21, A.
Mauri41, B. Maurin40, A. Mazurov46, M. McCann54, J. McCarthy46, A. McNab55, R.
McNulty13, B. Meadows58, F. Meier10, M. Meissner12, D. Melnychuk29, M. Merk42,
E Michielin23, D.A. Milanes64, M.-N. Minard4, D.S. Mitzel12, J. Molina
Rodriguez61, I.A. Monroy64, S. Monteil5, M. Morandin23, P. Morawski28, A.
Mordà6, M.J. Morello24,t, J. Moron28, A.B. Morris51, R. Mountain60, F.
Muheim51, M. Mulder42, M. Mussini15, D. Müller55, J. Müller10, K. Müller41, V.
Müller10, P. Naik47, T. Nakada40, R. Nandakumar50, A. Nandi56, I. Nasteva2, M.
Needham51, N. Neri22, S. Neubert12, N. Neufeld39, M. Neuner12, A.D. Nguyen40,
C. Nguyen-Mau40,n, V. Niess5, S. Nieswand9, R. Niet10, N. Nikitin33, T.
Nikodem12, A. Novoselov36, D.P. O’Hanlon49, A. Oblakowska-Mucha28, V.
Obraztsov36, S. Ogilvy19, R. Oldeman48, C.J.G. Onderwater69, J.M. Otalora
Goicochea2, A. Otto39, P. Owen41, A. Oyanguren68, A. Palano14,d, F.
Palombo22,q, M. Palutan19, J. Panman39, A. Papanestis50, M. Pappagallo52, L.L.
Pappalardo17,g, C. Pappenheimer58, W. Parker59, C. Parkes55, G. Passaleva18,
G.D. Patel53, M. Patel54, C. Patrignani15,e, A. Pearce55,50, A. Pellegrino42,
G. Penso26,k, M. Pepe Altarelli39, S. Perazzini39, P. Perret5, L. Pescatore46,
K. Petridis47, A. Petrolini20,h, A. Petrov66, M. Petruzzo22,q, E. Picatoste
Olloqui37, B. Pietrzyk4, M. Pikies27, D. Pinci26, A. Pistone20, A. Piucci12,
S. Playfer51, M. Plo Casasus38, T. Poikela39, F. Polci8, A. Poluektov49,35, I.
Polyakov32, E. Polycarpo2, G.J. Pomery47, A. Popov36, D. Popov11,39, B.
Popovici30, C. Potterat2, E. Price47, J.D. Price53, J. Prisciandaro38, A.
Pritchard53, C. Prouve47, V. Pugatch45, A. Puig Navarro40, G. Punzi24,p, W.
Qian56, R. Quagliani7,47, B. Rachwal27, J.H. Rademacker47, M. Rama24, M. Ramos
Pernas38, M.S. Rangel2, I. Raniuk44, G. Raven43, F. Redi54, S. Reichert10,
A.C. dos Reis1, C. Remon Alepuz68, V. Renaudin7, S. Ricciardi50, S.
Richards47, M. Rihl39, K. Rinnert53,39, V. Rives Molina37, P. Robbe7,39, A.B.
Rodrigues1, E. Rodrigues58, J.A. Rodriguez Lopez64, P. Rodriguez Perez55, A.
Rogozhnikov67, S. Roiser39, V. Romanovskiy36, A. Romero Vidal38, J.W.
Ronayne13, M. Rotondo23, T. Ruf39, P. Ruiz Valls68, J.J. Saborido Silva38, N.
Sagidova31, B. Saitta16,f, V. Salustino Guimaraes2, C. Sanchez Mayordomo68, B.
Sanmartin Sedes38, R. Santacesaria26, C. Santamarina Rios38, M. Santimaria19,
E. Santovetti25,j, A. Sarti19,k, C. Satriano26,s, A. Satta25, D.M. Saunders47,
D. Savrina32,33, S. Schael9, M. Schiller39, H. Schindler39, M. Schlupp10, M.
Schmelling11, T. Schmelzer10, B. Schmidt39, O. Schneider40, A. Schopper39, M.
Schubiger40, M.-H. Schune7, R. Schwemmer39, B. Sciascia19, A. Sciubba26,k, A.
Semennikov32, A. Sergi46, N. Serra41, J. Serrano6, L. Sestini23, P. Seyfert21,
M. Shapkin36, I. Shapoval17,44,g, Y. Shcheglov31, T. Shears53, L. Shekhtman35,
V. Shevchenko66, A. Shires10, B.G. Siddi17, R. Silva Coutinho41, L. Silva de
Oliveira2, G. Simi23,o, M. Sirendi48, N. Skidmore47, T. Skwarnicki60, E.
Smith54, I.T. Smith51, J. Smith48, M. Smith55, H. Snoek42, M.D. Sokoloff58,
F.J.P. Soler52, D. Souza47, B. Souza De Paula2, B. Spaan10, P. Spradlin52, S.
Sridharan39, F. Stagni39, M. Stahl12, S. Stahl39, P. Stefko40, S. Stefkova54,
O. Steinkamp41, O. Stenyakin36, S. Stevenson56, S. Stoica30, S. Stone60, B.
Storaci41, S. Stracka24,t, M. Straticiuc30, U. Straumann41, L. Sun58, W.
Sutcliffe54, K. Swientek28, V. Syropoulos43, M. Szczekowski29, T. Szumlak28,
S. T’Jampens4, A. Tayduganov6, T. Tekampe10, G. Tellarini17,g, F. Teubert39,
C. Thomas56, E. Thomas39, J. van Tilburg42, V. Tisserand4, M. Tobin40, S.
Tolk48, L. Tomassetti17,g, D. Tonelli39, S. Topp-Joergensen56, E. Tournefier4,
S. Tourneur40, K. Trabelsi40, M. Traill52, M.T. Tran40, M. Tresch41, A.
Trisovic39, A. Tsaregorodtsev6, P. Tsopelas42, A. Tully48, N. Tuning42, A.
Ukleja29, A. Ustyuzhanin67,66, U. Uwer12, C. Vacca16,39,f, V. Vagnoni15,39, S.
Valat39, G. Valenti15, A. Vallier7, R. Vazquez Gomez19, P. Vazquez Regueiro38,
S. Vecchi17, M. van Veghel42, J.J. Velthuis47, M. Veltri18,r, G. Veneziano40,
A. Venkateswaran60, M. Vesterinen12, B. Viaud7, D. Vieira1, M. Vieites Diaz38,
X. Vilasis-Cardona37,m, V. Volkov33, A. Vollhardt41, B Voneki39, D. Voong47,
A. Vorobyev31, V. Vorobyev35, C. Voß65, J.A. de Vries42, C. Vázquez Sierra38,
R. Waldi65, C. Wallace49, R. Wallace13, J. Walsh24, J. Wang60, D.R. Ward48,
H.M. Wark53, N.K. Watson46, D. Websdale54, A. Weiden41, M. Whitehead39, J.
Wicht49, G. Wilkinson56,39, M. Wilkinson60, M. Williams39, M.P. Williams46, M.
Williams57, T. Williams46, F.F. Wilson50, J. Wimberley59, J. Wishahi10, W.
Wislicki29, M. Witek27, G. Wormser7, S.A. Wotton48, K. Wraight52, S. Wright48,
K. Wyllie39, Y. Xie63, Z. Xing60, Z. Xu40, Z. Yang3, H. Yin63, J. Yu63, X.
Yuan35, O. Yushchenko36, M. Zangoli15, K.A. Zarebski46, M. Zavertyaev11,c, L.
Zhang3, Y. Zhang7, Y. Zhang62, A. Zhelezov12, Y. Zheng62, A. Zhokhov32, V.
Zhukov9, S. Zucchelli15.

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
4LAPP, Université Savoie Mont-Blanc, CNRS/IN2P3, Annecy-Le-Vieux, France
5Clermont Université, Université Blaise Pascal, CNRS/IN2P3, LPC, Clermont-
Ferrand, France
6CPPM, Aix-Marseille Université, CNRS/IN2P3, Marseille, France
7LAL, Université Paris-Sud, CNRS/IN2P3, 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
14Sezione INFN di Bari, Bari, Italy
15Sezione INFN di Bologna, Bologna, Italy
16Sezione INFN di Cagliari, Cagliari, Italy
17Sezione INFN di Ferrara, Ferrara, Italy
18Sezione INFN di Firenze, Firenze, Italy
19Laboratori Nazionali dell’INFN di Frascati, Frascati, Italy
20Sezione INFN di Genova, Genova, Italy
21Sezione INFN di Milano Bicocca, Milano, Italy
22Sezione INFN di Milano, Milano, Italy
23Sezione INFN di Padova, Padova, Italy
24Sezione INFN di Pisa, Pisa, Italy
25Sezione INFN di Roma Tor Vergata, Roma, Italy
26Sezione INFN di Roma La Sapienza, Roma, Italy
27Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of
Sciences, Kraków, Poland
28AGH - University of Science and Technology, Faculty of Physics and Applied
Computer Science, Kraków, Poland
29National Center for Nuclear Research (NCBJ), Warsaw, Poland
30Horia Hulubei National Institute of Physics and Nuclear Engineering,
Bucharest-Magurele, Romania
31Petersburg Nuclear Physics Institute (PNPI), Gatchina, Russia
32Institute of Theoretical and Experimental Physics (ITEP), Moscow, Russia
33Institute of Nuclear Physics, Moscow State University (SINP MSU), Moscow,
Russia
34Institute for Nuclear Research of the Russian Academy of Sciences (INR RAN),
Moscow, Russia
35Budker Institute of Nuclear Physics (SB RAS) and Novosibirsk State
University, Novosibirsk, Russia
36Institute for High Energy Physics (IHEP), Protvino, Russia
37Universitat de Barcelona, Barcelona, Spain
38Universidad de Santiago de Compostela, Santiago de Compostela, Spain
39European Organization for Nuclear Research (CERN), Geneva, Switzerland
40Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
41Physik-Institut, Universität Zürich, Zürich, Switzerland
42Nikhef National Institute for Subatomic Physics, Amsterdam, The Netherlands
43Nikhef National Institute for Subatomic Physics and VU University Amsterdam,
Amsterdam, The Netherlands
44NSC Kharkiv Institute of Physics and Technology (NSC KIPT), Kharkiv, Ukraine
45Institute for Nuclear Research of the National Academy of Sciences (KINR),
Kyiv, Ukraine
46University of Birmingham, Birmingham, United Kingdom
47H.H. Wills Physics Laboratory, University of Bristol, Bristol, United
Kingdom
48Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom
49Department of Physics, University of Warwick, Coventry, United Kingdom
50STFC Rutherford Appleton Laboratory, Didcot, United Kingdom
51School of Physics and Astronomy, University of Edinburgh, Edinburgh, United
Kingdom
52School of Physics and Astronomy, University of Glasgow, Glasgow, United
Kingdom
53Oliver Lodge Laboratory, University of Liverpool, Liverpool, United Kingdom
54Imperial College London, London, United Kingdom
55School of Physics and Astronomy, University of Manchester, Manchester,
United Kingdom
56Department of Physics, University of Oxford, Oxford, United Kingdom
57Massachusetts Institute of Technology, Cambridge, MA, United States
58University of Cincinnati, Cincinnati, OH, United States
59University of Maryland, College Park, MD, United States
60Syracuse University, Syracuse, NY, United States
61Pontifícia Universidade Católica do Rio de Janeiro (PUC-Rio), Rio de
Janeiro, Brazil, associated to 2
62University of Chinese Academy of Sciences, Beijing, China, associated to 3
63Institute of Particle Physics, Central China Normal University, Wuhan,
Hubei, China, associated to 3
64Departamento de Fisica , Universidad Nacional de Colombia, Bogota, Colombia,
associated to 8
65Institut für Physik, Universität Rostock, Rostock, Germany, associated to 12
66National Research Centre Kurchatov Institute, Moscow, Russia, associated to
32
67Yandex School of Data Analysis, Moscow, Russia, associated to 32
68Instituto de Fisica Corpuscular (IFIC), Universitat de Valencia-CSIC,
Valencia, Spain, associated to 37
69Van Swinderen Institute, University of Groningen, Groningen, The
Netherlands, associated to 42

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, Viet Nam
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