A
bstract
The production of prompt
D
+
and
D
s
+
mesons is studied in proton-lead collisions at a centre-of-mass energy of
s
NN
= 5
.
02 TeV. The data sample corresponding to an integrated luminosity ...of (1
.
58 ± 0
.
02)nb
−
1
is collected by the LHCb experiment at the LHC. The differential production cross-sections are measured using
D
+
and
D
s
+
candidates with transverse momentum in the range of 0
< p
T
<
14 GeV
/c
and rapidities in the ranges of 1
.
5
< y
∗
<
4
.
0 and –5
.
0
< y
∗
<
–2
.
5 in the nucleon-nucleon centre-of-mass system. For both particles, the nuclear modification factor and the forward-backward production ratio are determined. These results are compared with theoretical models that include initial-state nuclear effects. In addition, measurements of the cross-section ratios between
D
+
,
D
s
+
and
D
0
mesons are presented, providing a baseline for studying the charm hadronization in lead-lead collisions at LHC energies.
A
bstract
The ratio of branching fractions between
B
0
→
J/ψπ
0
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
B
0
→
J/ψπ
0
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.
A
bstract
A measurement of
CP
-violating observables associated with the interference of
B
0
→ D
0
K
⋆
(892)
0
and
B
0
→
D
¯
0
K
⋆
892
0
decay amplitudes is performed in the
D
0
→ K
∓
π
±
(
π
+
π
−
...),
D
0
→ π
+
π
−
(
π
+
π
−
), and
D
0
→ K
+
K
−
final states using data collected by the LHCb experiment corresponding to an integrated luminosity of 9 fb
−
1
.
CP
-violating observables related to the interference of
B
s
0
→
D
0
K
¯
⋆
892
0
and
B
s
0
→
D
¯
0
K
¯
⋆
892
0
are also measured, but no evidence for interference is found. The
B
0
observables are used to constrain the parameter space of the CKM angle
γ
and the hadronic parameters
r
B
0
DK
⋆
and
δ
B
0
DK
⋆
with inputs from other measurements. In a combined analysis, these measurements allow for four solutions in the parameter space, only one of which is consistent with the world average.
A
bstract
A search for
CP
violation in
D
0
→
K
S
0
K
+
π
−
and
D
0
→
K
S
0
K
−
π
+
decays is reported. The search is performed using an unbinned model-independent method known as the energy test that ...probes local
CP
violation in the phase space of the decays. The data analysed correspond to an integrated luminosity of 5
.
4 fb
−
1
collected in proton-proton collisions by the LHCb experiment at a centre-of-mass energy of
s
= 13 TeV, amounting to approximately 950 thousand and 620 thousand signal candidates for the
D
0
→
K
S
0
K
−
π
+
and
D
0
→
K
S
0
K
+
π
−
modes, respectively. The method is validated using
D
0
→
K
−
π
+
π
−
π
+
and
D
0
→
K
S
0
π
+
π
−
decays, where
CP
-violating effects are expected to be negligible, and using background-enhanced regions of the signal decays. The results are consistent with
CP
symmetry in both the
D
0
→
K
S
0
K
−
π
+
and the
D
0
→
K
S
0
K
+
π
−
decays, with
p
-values for the hypothesis of no
CP
violation of 70% and 66%, respectively.
A
bstract
The production of
ψ
(2
S
) 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
(2
S
) production cross-sections and the ratio of the
ψ
(2
S
) 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
(2
S
) is observed to be more suppressed compared to
pp
collisions than the prompt
J/ψ
production, while the nonprompt productions have similar suppression factors.
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.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
7.
Observation of Ξb0→Ξc+Ds- and Ξb-→Ξc0Ds- decays Abdelmotteleb, A. S. W; Adlarson, P; Agapopoulou, C ...
The European physical journal. C, Particles and fields,
03/2024, Letnik:
84, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The
Ξ
b
0
→
Ξ
c
+
D
s
-
and
Ξ
b
-
→
Ξ
c
0
D
s
-
decays are observed for the first time using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of
s
=
13
TeV
, ...corresponding to an integrated luminosity of
5.1
fb
-
1
. The branching fractions times the production cross-sections of
Ξ
b
baryons relative to that of
Λ
b
0
baryon are measured to be
R
Ξ
b
0
Λ
b
0
≡
σ
Ξ
b
0
σ
Λ
b
0
×
B
Ξ
b
0
→
Ξ
c
+
D
s
-
B
Λ
b
0
→
Λ
c
0
D
s
-
=
(
15.8
±
1.1
±
0.6
±
7.7
)
%
,
R
Ξ
b
-
Λ
b
0
≡
σ
Ξ
b
-
σ
Λ
b
0
×
B
Ξ
b
-
→
Ξ
c
0
D
s
-
B
Λ
b
0
→
Λ
c
0
D
s
-
=
(
16.9
±
1.3
±
0.9
±
4.3
)
%
,
where the first uncertainties are statistical, the second systematic, and the third due to the uncertainties on the decay branching fractions of relevant charmed baryons. The masses of
Ξ
b
0
and
Ξ
b
-
baryons are measured to be
m
Ξ
b
0
=
5791.12
±
0.60
±
0.45
±
0.24
MeV
/
c
2
and
m
Ξ
b
-
=
5797.02
±
0.63
±
0.49
±
0.29
MeV
/
c
2
, where the uncertainties are statistical, systematic, and those due to charmed-hadron masses, respectively.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A
bstract
A measurement of the CP-violating observables from
B
±
→
D
*
K
±
and
B
±
→
D
*
π
±
decays is presented, where
D
*
(
D
) is an admixture of
D
*0
and
D
¯
∗
0
(
D
0
and
D
¯
0
) states and is ...reconstructed through the decay chains
D
*
→ Dπ
0
/γ
and
D
→
K
S
0
π
+
π
−
/
K
S
0
K
+
K
−
. The measurement is performed by analysing the signal yield variation across the
D
decay phase space and is independent of any amplitude model. The data sample used was collected by the LHCb experiment in proton-proton collisions and corresponds to a total integrated luminosity of 9 fb
−
1
at centre-of-mass energies of 7, 8 and 13 TeV. The CKM angle
γ
is determined to be
69
−
14
+
13
∘
using the measured CP-violating observables. The hadronic parameters
r
B
D
∗
K
±
,
r
B
D
∗
π
±
,
δ
B
D
∗
K
±
,
δ
B
D
∗
π
±
, which are the ratios and strong phase differences between favoured and suppressed
B
±
decays, are also reported.
The decay-time-dependent CP asymmetry in B_{s}^{0}→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_{s}^{0} signal decays with an invariant K^{+}K^{-} mass in the vicinity of the ϕ(1020) resonance, the CP-violating phase ϕ_{s} is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the B_{s}^{0}-Bover ¯_{s}^{0} system, ΔΓ_{s}, and the difference of the average B_{s}^{0} and B^{0} meson decay widths, Γ_{s}-Γ_{d}. The values obtained are ϕ_{s}=-0.039±0.022±0.006 rad, ΔΓ_{s}=0.0845±0.0044±0.0024 ps^{-1}, and Γ_{s}-Γ_{d}=-0.0056_{-0.0015}^{+0.0013}±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.
A measurement of time-dependent CP violation in the decays of B^{0} and Bover ¯^{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 sqrts=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.
