Branching fraction and effective lifetime measurements of the rare decay B_{s}^{0}→μ^{+}μ^{-} and searches for the decays B^{0}→μ^{+}μ^{-} and B_{s}^{0}→μ^{+}μ^{-}γ are reported using proton-proton ...collision data collected with the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV, corresponding to a luminosity of 9 fb^{-1}. The branching fraction B(B_{s}^{0}→μ^{+}μ^{-})=(3.09_{-0.43-0.11}^{+0.46+0.15})×10^{-9} and the effective lifetime τ(B_{s}^{0}→μ^{+}μ^{-})=2.07±0.29±0.03 ps are measured, where the first uncertainty is statistical and the second systematic. No significant signal for B^{0}→μ^{+}μ^{-} and B_{s}^{0}→μ^{+}μ^{-}γ decays is found and upper limits B(B^{0}→μ^{+}μ^{-})<2.6×10^{-10} and B(B_{s}^{0}→μ^{+}μ^{-}γ)<2.0×10^{-9} at the 95% C.L. are determined, where the latter is limited to the range m_{μμ}>4.9 GeV/c^{2}. The results are in agreement with the standard model expectations.
We present an angular analysis of the B^{+}→K^{*+}(→K_{S}^{0}π^{+})μ^{+}μ^{-} decay using 9 fb^{-1} of pp collision data collected with the LHCb experiment. For the first time, the full set of ...CP-averaged angular observables is measured in intervals of the dimuon invariant mass squared. Local deviations from standard model predictions are observed, similar to those in previous LHCb analyses of the isospin-partner B^{0}→K^{*0}μ^{+}μ^{-} decay. The global tension is dependent on which effective couplings are considered and on the choice of theory nuisance parameters.
Long-lived particles decaying to
e
±
μ
∓
ν
, with masses between 7 and
50
GeV/
c
2
and lifetimes between 2 and
50
ps
, are searched for by looking at displaced vertices containing electrons and muons ...of opposite charges. The search is performed using
5.4
fb
-
1
of
p
p
collisions collected with the LHCb detector at a centre-of-mass energy of
s
=
13
TeV
. Three mechanisms of production of long-lived particles are considered: the direct pair production from quark interactions, the pair production from the decay of a Standard-Model-like Higgs boson with a mass of
125
GeV/
c
2
, and the charged current production from an on-shell
W
boson with an additional lepton. No evidence of these long-lived states is obtained and upper limits on the production cross-section times branching fraction are set on the different production modes.
The first search for nonresonant
B
c
+
→
π
+
μ
+
μ
-
decays is reported. The analysis uses proton–proton collision data collected with the LHCb detector between 2011 and 2018, corresponding to an ...integrated luminosity of 9
fb
-
1
. No evidence for an excess of signal events over background is observed and an upper limit is set on the branching fraction ratio
B
(
B
c
+
→
π
+
μ
+
μ
-
)
/
B
(
B
c
+
→
J
/
ψ
π
+
)
<
2.1
×
10
-
4
at
90
%
confidence level. Additionally, an updated measurement of the ratio of the
B
c
+
→
ψ
(
2
S
)
π
+
and
B
c
+
→
J
/
ψ
π
+
branching fractions is reported. The ratio
B
(
B
c
+
→
ψ
(
2
S
)
π
+
)
/
B
(
B
c
+
→
J
/
ψ
π
+
)
is measured to be
0.254
±
0.018
±
0.003
±
0.005
, where the first uncertainty is statistical, the second systematic, and the third is due to the uncertainties on the branching fractions of the leptonic
J
/
ψ
and
ψ
(
2
S
)
decays. This measurement is the most precise to date and is consistent with previous LHCb results.
Abstract The first search for nonresonant $${{B} _{c} ^+} \!\rightarrow {{\pi } ^+} {\mu ^+\mu ^-} $$ B c + → π + μ + μ - decays is reported. The analysis uses proton–proton collision data collected ...with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 $$\,\text {fb} ^{-1}$$ fb - 1 . No evidence for an excess of signal events over background is observed and an upper limit is set on the branching fraction ratio $${\mathcal {B}} ({{B} _{c} ^+} \!\rightarrow {{\pi } ^+} {\mu ^+\mu ^-} )/{\mathcal {B}} ({{B} _{c} ^+} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\pi } ^+} ) < 2.1\times 10^{-4}$$ B ( B c + → π + μ + μ - ) / B ( B c + → J / ψ π + ) < 2.1 × 10 - 4 at $$90\%$$ 90 % confidence level. Additionally, an updated measurement of the ratio of the $${{B} _{c} ^+} \!\rightarrow {\psi {(2S)}} {{\pi } ^+} $$ B c + → ψ ( 2 S ) π + and $${{B} _{c} ^+} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\pi } ^+} $$ B c + → J / ψ π + branching fractions is reported. The ratio $${\mathcal {B}} ({{B} _{c} ^+} \!\rightarrow {\psi {(2S)}} {{\pi } ^+} )/{\mathcal {B}} ({{B} _{c} ^+} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\pi } ^+} )$$ B ( B c + → ψ ( 2 S ) π + ) / B ( B c + → J / ψ π + ) is measured to be $$0.254\pm 0.018 \pm 0.003 \pm 0.005$$ 0.254 ± 0.018 ± 0.003 ± 0.005 , where the first uncertainty is statistical, the second systematic, and the third is due to the uncertainties on the branching fractions of the leptonic $${J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }$$ J / ψ and $$\psi {(2S)}$$ ψ ( 2 S ) decays. This measurement is the most precise to date and is consistent with previous LHCb results.
A measurement of mixing and C P violation in neutral charm mesons is performed using data reconstructed in proton-proton collisions collected by the LHCb experiment from 2016 to 2018, corresponding ...to an integrated luminosity of 5.4 fb−1. A total of 30.6 million D0 → K0S π+ π− decays are analyzed using a method optimized for the measurement of the mass difference between neutral charm-meson eigenstates. Allowing for CP violation in mixing and in the interference between mixing and decay, the mass and decay-width differences are measured to be xCP = 3.97 ± 0.46 ( stat ) ± 0.29 (syst) × 10−3 and yCP = 4.59 ± 1.20 (stat) ± 0.85 (syst) × 10-3, respectively. The C P -violating parameters are measured as Δx = −0.27 ± 0.18 (stat) ± 0.01 (syst) × 10−3 and Δy = 0.20 ± 0.36 (stat) ± 0.13 (syst ) × 10−3. This is the first observation of a nonzero mass difference in the D0 meson system, with a significance exceeding seven standard deviations. The data are consistent with C P symmetry and improve existing constraints on the associated parameters.
Abstract
Mesons comprising a beauty quark and strange quark can oscillate between particle (
$${B}_{\mathrm{s}}^{0}$$
B
s
0
) and antiparticle (
$${\overline{B}}_{\mathrm{s}}^{0}$$
B
¯
s
0
) flavour ...eigenstates, with a frequency given by the mass difference between heavy and light mass eigenstates, Δ
m
s
. Here we present a measurement of Δ
m
s
using
$${B}_{\mathrm{s}}^{0}\to {D}_{\mathrm{s}}^{-}$$
B
s
0
→
D
s
−
π
+
decays produced in proton–proton collisions collected with the LHCb detector at the Large Hadron Collider. The oscillation frequency is found to be Δ
m
s
= 17.7683 ± 0.0051 ± 0.0032 ps
−1
, where the first uncertainty is statistical and the second is systematic. This measurement improves on the current Δ
m
s
precision by a factor of two. We combine this result with previous LHCb measurements to determine Δ
m
s
= 17.7656 ± 0.0057 ps
−1
, which is the legacy measurement of the original LHCb detector.
A
bstract
The production cross-sections of
J/ψ
mesons in proton-proton collisions at a centre-of-mass energy of
$$ \sqrt{s} $$
s
= 5 TeV are measured using a data sample corresponding to an ...integrated luminosity of 9
.
13 ± 0
.
18 pb
−
1
, collected by the LHCb experiment. The cross-sections are measured differentially as a function of transverse momentum,
p
T
, and rapidity,
y
, and separately for
J/ψ
mesons produced promptly and from beauty hadron decays (nonprompt). With the assumption of unpolarised
J/ψ
mesons, the production cross-sections integrated over the kinematic range 0
< p
T
<
20 GeV/
c
and 2
.
0
< y <
4
.
5 are
$$ {\displaystyle \begin{array}{c}{\sigma}_{\mathrm{prompt}}\ J/\psi =8.154\pm 0.010\pm 0.283\ \upmu \mathrm{b},\\ {}{\sigma}_{\mathrm{nonprompt}}\ J/\psi =0.820\pm 0.003\pm 0.034\ \upmu \mathrm{b},\end{array}} $$
σ
prompt
J
/
ψ
=
8.154
±
0.010
±
0.283
μb
,
σ
nonprompt
J
/
ψ
=
0.820
±
0.003
±
0.034
μb
,
where the first uncertainties are statistical and the second systematic. These cross-sections are compared with those at
$$ \sqrt{s} $$
s
= 8 TeV and 13 TeV, and are used to update the measurement of the nuclear modification factor in proton-lead collisions for
J/ψ
mesons at a centre-of-mass energy per nucleon pair of
$$ \sqrt{s_{\mathrm{NN}}} $$
s
NN
= 5 TeV. The results are compared with theoretical predictions.
Abstract
A flavour-tagged time-dependent angular analysis of
$${{B} ^0_{s}} \!\rightarrow {{J /\psi }} \phi $$
B
s
0
→
J
/
ψ
ϕ
decays is presented where the
$${J /\psi }$$
J
/
ψ
meson is ...reconstructed through its decay to an
$$e ^+e ^-$$
e
+
e
-
pair. The analysis uses a sample of
pp
collision data recorded with the LHCb experiment at centre-of-mass energies of 7 and
$$8\text {\,Te V} $$
8
\,Te V
, corresponding to an integrated luminosity of
$$3 \text {\,fb} ^{-1} $$
3
\,fb
-
1
. The
$$C\!P$$
C
P
-violating phase and lifetime parameters of the
$${B} ^0_{s} $$
B
s
0
system are measured to be
$${\phi _{{s}}} =0.00\pm 0.28\pm 0.07\text {\,rad}$$
ϕ
s
=
0.00
±
0.28
±
0.07
\,rad
,
$${\Delta \Gamma _{{s}}} =0.115\pm 0.045\pm 0.011\text {\,ps} ^{-1} $$
Δ
Γ
s
=
0.115
±
0.045
±
0.011
\,ps
-
1
and
$${\Gamma _{{s}}} =0.608\pm 0.018\pm 0.012\text {\,ps} ^{-1} $$
Γ
s
=
0.608
±
0.018
±
0.012
\,ps
-
1
where the first uncertainty is statistical and the second systematic. This is the first time that
$$C\!P$$
C
P
-violating parameters are measured in the
$${{B} ^0_{s}} \!\rightarrow {{J /\psi }} \phi $$
B
s
0
→
J
/
ψ
ϕ
decay with an
$$e ^+e ^-$$
e
+
e
-
pair in the final state. The results are consistent with previous measurements in other channels and with the Standard Model predictions.
The mass difference between the Omega -b and Xi -b baryons is measured using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb-1, and is ...found to be mo Omega -bthorn - mo Xi -bthorn 1/4 248.54? 0.51ostatthorn ? 0.38osystthorn MeV=c2. The mass of the Omega -b baryon is measured to be mo Omega -bthorn 1/4 6045.9 ? 0.5ostatthorn ? 0.6osystthorn MeV=c2. This is the most precise determination of the Omega -b mass to date. In addition, the production rate of Omega -b baryons relative to that of Xi -b baryons is measured for the first time in pp collisions, using an LHCb dataset collected at a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 6 fb-1. Reconstructing beauty baryons in the kinematic region 2 < <eta> < 6 and pT < 20 GeV=c with their decays to a J=psi meson and a hyperon, the ratio f Omega- b f Xi- b tation fractions of b quarks into Omega -b and Xi -b baryons, respectively, and B represents the branching fractions of their respective decays.
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