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.
The decays
Λ
b
0
→
Λ
c
+
D
¯
(
∗
)
0
K
-
and
Λ
b
0
→
Λ
c
+
D
s
∗
-
are observed for the first time, in proton-proton collision data at
s
=
13
Te
V
, corresponding to an integrated luminosity of 5.4
...fb
-
1
collected with the LHCb detector. Their ratios of branching fractions with respect to the
Λ
b
0
→
Λ
c
+
D
s
-
mode are measured to be
B
Λ
b
0
→
Λ
c
+
D
¯
0
K
-
B
Λ
b
0
→
Λ
c
+
D
s
-
=
0.1908
-
0.0034
+
0.0036
-
0.0018
+
0.0016
±
0.0038
,
B
Λ
b
0
→
Λ
c
+
D
¯
∗
0
K
-
B
Λ
b
0
→
Λ
c
+
D
s
-
=
0.589
-
0.017
+
0.018
-
0.018
+
0.017
±
0.012
,
B
Λ
b
0
→
Λ
c
+
D
s
∗
-
B
Λ
b
0
→
Λ
c
+
D
s
-
=
1.668
±
0.022
-
0.055
+
0.061
,
where the first uncertainties are statistical, the second systematic, and the third, for the
Λ
b
0
→
Λ
c
+
D
¯
(
∗
)
0
K
-
decays, are due to the uncertainties on the branching fractions of the
D
s
-
→
K
-
K
+
π
-
and
D
¯
0
→
K
+
π
-
decay modes. The measured branching fractions probe factorization assumptions in effective theories and provide the normalization for future pentaquark searches in
Λ
b
0
→
Λ
c
+
D
¯
(
∗
)
0
K
-
decay channels.
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.
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.
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.
First observation of the Λb0→ D+D−Λ decay Aidala, C. A.; Albrecht, J.; Aliouche, Z. ...
The journal of high energy physics,
16/7, Letnik:
2024, Številka:
7
Journal Article
Recenzirano
Odprti dostop
A
bstract
The
Λ
b
0
→
D
+
D
−
Λ decay is observed for the first time using proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an ...integrated luminosity of 5
.
3 fb
−
1
. Using the
B
0
→
D
+
D
−
K
S
0
decay as a reference channel, the product of the relative production cross-section and decay branching fractions is measured to be
R
=
σ
Λ
b
0
σ
B
0
=
B
Λ
b
0
→
D
+
D
−
Λ
B
B
0
→
D
+
D
−
K
S
0
=
0.179
±
0.022
±
0.014
,
where the first uncertainty is statistical and the second is systematic. The known branching fraction of the reference channel,
B
B
0
→
D
+
D
−
K
S
0
, and the cross-section ratio,
σ
Λ
b
0
/
σ
B
0
, previously measured by LHCb are used to derive the branching fraction of the
Λ
b
0
→ D
+
D
−
Λ decay
B
Λ
b
0
→
D
+
D
−
Λ
=
1.24
±
0.15
±
0.10
±
0.28
±
0.11
×
10
−
4
,
where the third and fourth contributions are due to uncertainties of
B
B
0
→
D
+
D
−
K
S
0
and
σ
Λ
b
0
/
σ
B
0
, respectively. Inspection of the
D
+
Λ and
D
+
D
−
invariant-mass distributions suggests a rich presence of intermediate resonances in the decay. The
Λ
b
0
→
D
*+
D
−
Λ decay is also observed for the first time as a partially reconstructed component in the
D
+
D
−
Λ invariant mass spectrum.
Search for the Bs0→ μ+μ−γ decay Agapopoulou, C.; Alessio, F.; Amey, J. L. ...
The journal of high energy physics,
11/7, Letnik:
2024, Številka:
7
Journal Article
Recenzirano
Odprti dostop
A
bstract
A search for the fully reconstructed
B
s
0
→ μ
+
μ
−
γ
decay is performed at the LHCb experiment using proton-proton collisions at
s
= 13 TeV corresponding to an integrated luminosity of 5
....
4 fb
−
1
. No significant signal is found and upper limits on the branching fraction in intervals of the dimuon mass are set
B
B
s
0
→
μ
+
μ
−
γ
<
4.2
×
10
−
8
,
m
μ
+
μ
−
∈
2
m
μ
1.70
GeV
/
c
2
,
B
B
s
0
→
μ
+
μ
−
γ
<
7.7
×
10
−
8
,
m
μ
+
μ
−
∈
1.70, 2.88
GeV
/
c
2
,
B
B
s
0
→
μ
+
μ
−
γ
<
4.2
×
10
−
8
,
m
μ
+
μ
−
∈
3.92
m
B
s
0
GeV
/
c
2
,
at 95% confidence level. Additionally, upper limits are set on the branching fraction in the 2
m
μ
,
1
.
70 GeV
/c
2
dimuon mass region excluding the contribution from the intermediate
ϕ
(1020) meson, and in the region combining all dimuon-mass intervals.
Amplitude analysis of the Λb0→pK−γ decay Amhis, Y.; Andersson, M.; Bachmayer, M. ...
The journal of high energy physics,
18/6, Letnik:
2024, Številka:
6
Journal Article
Recenzirano
Odprti dostop
A
bstract
The resonant structure of the radiative decay
Λ
b
0
→
pK
−
γ
in the region of proton-kaon invariant-mass up to 2.5 GeV/
c
2
is studied using proton-proton collision data recorded at ...centre-of-mass energies of 7, 8, and 13 TeV collected with the LHCb detector, corresponding to a total integrated luminosity of 9 fb
−
1
. Results are given in terms of fit and interference fractions between the different components contributing to this final state. Only Λ resonances decaying to
pK
−
are found to be relevant, where the largest contributions stem from the Λ(1520), Λ(1600), Λ(1800), and Λ(1890) states.
