18 research outputs found
Improved measurement of CP violation parameters in Bs0→J/ψK+K− decays in the vicinity of the ϕ(1020) resonance
The decay-time-dependent
C
P
asymmetry in
B
0
s
→
J
/
ψ
(
→
μ
+
μ
−
)
K
+
K
−
decays is measured using proton-proton collision data, corresponding to an integrated luminosity of
6
fb
−
1
, collected with the LHCb detector at a center-of-mass energy of 13 TeV. Using a sample of approximately 349 000
B
0
s
signal decays with an invariant
K
+
K
−
mass in the vicinity of the
ϕ
(
1020
)
resonance, the
C
P
-violating phase
ϕ
s
is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the
B
0
s
−
¯
B
0
s
system,
Δ
Γ
s
, and the difference of the average
B
0
s
and
B
0
meson decay widths,
Γ
s
−
Γ
d
. The values obtained are
ϕ
s
=
−
0.039
±
0.022
±
0.006
rad
,
Δ
Γ
s
=
0.0845
±
0.0044
±
0.0024
ps
−
1
, and
Γ
s
−
Γ
d
=
−
0.005
6
+
0.0013
−
0.0015
±
0.0014
ps
−
1
, where the first uncertainty is statistical and the second systematic. These are the most precise single measurements to date and are consistent with expectations based on the Standard Model and with the previous LHCb analyses of this decay. These results are combined with previous independent LHCb measurements. The phase
ϕ
s
is also measured independently for each polarization state of the
K
+
K
−
system and shows no evidence for polarization dependence
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Measurement of the branching fraction of B0 → J/ψπ0 decays
Abstract
The ratio of branching fractions between B0 → J/ψπ0 and B+ → J/ψK*+ decays is measured with proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb−1. The measured value is
B
B
0
→
J
/
ψ
π
0
B
B
+
→
J
/
ψ
K
∗
+
=
1.153
±
0.053
±
0.048
×
10
−
2
,
where the first uncertainty is statistical and the second is systematic. The branching fraction for B0 → J/ψπ0 decays is determined using the branching fraction of the normalisation channel, resulting in
B
B
0
→
J
/
ψ
π
0
=
1.670
±
0.077
±
0.069
±
0.095
×
10
−
5
,
where the last uncertainty corresponds to that of the external input. This result is consistent with the current world average value and competitive with the most precise single measurement to date.</jats:p
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Observation of the decay
Abstract
The first observation of the
B
c
+
→
J
/
ψ
π
+
π
0
decay is reported with high significance using proton-proton collision data, corresponding to an integrated luminosity of 9 fb−1, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV. The ratio of its branching fraction relative to the
B
c
+
→
J
/
ψ
π
+
channel is measured to be
B
B
c
+
→
J
/
ψ
π
+
π
0
B
B
c
+
→
J
/
ψ
π
+
=
2.80
±
0.15
±
0.11
±
0.16
,
where the first uncertainty is statistical, the second systematic and the third related to imprecise knowledge of the branching fractions for B+ → J/ψK*+ and
B
c
+
→
J
/
ψ
π
+
decays, which are used to determine the π0 detection efficiency. The π+π0 mass spectrum is found to be consistent with the dominance of an intermediate ρ+ contribution in accordance with a model based on QCD factorisation.</jats:p
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Prompt and nonprompt ψ(2S) production in pPb collisions at = 8.16 TeV
Abstract
The production of ψ(2S) mesons in proton-lead collisions at a centre-of-mass energy per nucleon pair of
s
NN
= 8.16 TeV is studied with the LHCb detector using data corresponding to an integrated luminosity of 34 nb−1. The prompt and nonprompt ψ(2S) production cross-sections and the ratio of the ψ(2S) to J/ψ cross-section are measured as a function of the meson transverse momentum and rapidity in the nucleon-nucleon centre-of-mass frame, together with forward-to-backward ratios and nuclear modification factors. The production of prompt ψ(2S) is observed to be more suppressed compared to pp collisions than the prompt J/ψ production, while the nonprompt productions have similar suppression factors.</jats:p
Measurement of CP Violation in B^{0}→ψ(→ℓ^{+}ℓ^{-})K_{S}^{0}(→π^{+}π^{-}) Decays.
A measurement of time-dependent CP violation in the decays of B^{0} and B[over ¯]^{0} mesons to the final states J/ψ(→μ^{+}μ^{-})K_{S}^{0}, ψ(2S)(→μ^{+}μ^{-})K_{S}^{0} and J/ψ(→e^{+}e^{-})K_{S}^{0} with K_{S}^{0}→π^{+}π^{-} is presented. The data correspond to an integrated luminosity of 6 fb^{-1} collected at a center-of-mass energy of sqrt[s]=13 TeV with the LHCb detector. The CP-violation parameters are measured to be S_{ψK_{S}^{0}}=0.717±0.013(stat)±0.008(syst) and C_{ψK_{S}^{0}}=0.008±0.012(stat)±0.003(syst). This measurement of S_{ψK_{S}^{0}} represents the most precise single measurement of the CKM angle β to date and is more precise than the current world average. In addition, measurements of the CP-violation parameters of the individual channels are reported and a combination with the LHCb Run 1 measurements is performed
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Search for decays and measurement of the branching fraction ratio
AbstractThe 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 {\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
%
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.</jats:p
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A measurement of ∆Γs
Abstract
Using a dataset corresponding to 9 fb−1 of integrated luminosity collected with the LHCb detector between 2011 and 2018 in proton-proton collisions, the decay-time distributions of the decay modes
B
s
0
→
J
/
ψη
′
and
B
s
0
→
J
/
ψ
π
+
π
−
are studied. The decay-width difference between the light and heavy mass eigenstates of the
B
s
0
meson is measured to be ∆Γs = 0.087 ± 0.012 ± 0.009 ps−1, where the first uncertainty is statistical and the second systematic.</jats:p
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A model-independent measurement of the CKM angle γ in partially reconstructed B± → D*h± decays with D → h+h− (h = π, K)
Abstract
A measurement of CP-violating observables in B± → D*K± and B± → D*π± decays is made where the photon or neutral pion from the D*→ Dγ or D*→ Dπ0 decay is not reconstructed. The D meson is reconstructed in the self-conjugate decay modes, D →
K
S
0
π+π− or D →
K
S
0
K+K−. The distribution of signal yields in the D decay phase space is analysed in a model-independent way. The measurement uses a data sample collected in proton-proton collisions at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of approximately 9 fb−1. The B± → D*K± and B± → D*π±CP-violating observables are interpreted in terms of hadronic parameters and the CKM angle γ, resulting in a measurement of γ = (
92
−
17
+
21
)°. The total uncertainty includes the statistical and systematic uncertainties, and the uncertainty due to external strong-phase inputs.</jats:p