A
bstract
A search for the lepton-flavour violating decays
B
0
→
K
*0
μ
±
e
∓
and
B
s
0
→ ϕμ
±
e
∓
is presented, using proton-proton collision data collected by the LHCb detector at the LHC, ...corresponding to an integrated luminosity of 9 fb
−
1
. No significant signals are observed and upper limits of
B
B
0
→
K
∗
0
μ
+
e
−
<
5.7
×
10
−
9
6.9
×
10
−
9
,
B
B
0
→
K
∗
0
μ
−
e
+
<
6.8
×
10
−
9
7.9
×
10
−
9
,
B
B
0
→
K
∗
0
μ
±
e
∓
<
10.1
×
10
−
9
11.7
×
10
−
9
,
B
B
s
0
→
ϕ
μ
±
e
∓
<
16.0
×
10
−
9
19.8
×
10
−
9
are set at 90% (95%) confidence level. These results constitute the world’s most stringent limits to date, with the limit on the decay
B
s
0
→ ϕμ
±
e
∓
the first being set. In addition, limits are reported for scalar and left-handed lepton-flavour violating New Physics scenarios.
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 associated production of prompt
J/ψ
and
Υ
mesons in
pp
collisions at a centre-of-mass energy of
s
= 13 TeV is studied using LHCb data, corresponding to an integrated luminosity of 4 fb
...−
1
. The measurement is performed for
J/ψ
(
Υ
) mesons with a transverse momentum
p
T
<
10 (30) GeV/
c
in the rapidity range 2
.
0
< y <
4
.
5. In this kinematic range, the cross-section of the associated production of prompt
J/ψ
and
Υ
(1
S
) mesons is measured to be 133 ± 22 ± 7 ± 3 pb, with a significance of 7
.
9
σ
, and that of prompt
J/ψ
and
Υ
(2
S
) mesons to be 76 ± 21 ± 4 ± 7 pb, with a significance of 4
.
9
σ
. The first uncertainty is statistical, the second systematic, and the third due to uncertainties on the used branching fractions. This is the first observation of the associated production of
J/ψ
and
Υ
(1
S
) in proton-proton collisions. Differential cross-sections are measured as functions of variables that are sensitive to kinematic correlations between the
J/ψ
and
Υ
(1
S
) mesons. The effective cross-sections of the associated production of prompt
J/ψ
and
Υ
mesons are obtained and found to be compatible with measurements using other particle productions.
The behavior of hydroxyapatite containing zinc and silicate ions during selective laser melting under irradiation at 10.6 µm was studied for the first time. For comparison, the behavior of the ...material heated in a high-temperature furnace was investigated. It was found that, in contrast to the slow heating in the furnace, heating of the mechanochemically synthesized material with the degree of substitution
x
= 0.2 by scanning the laser spot enables its recrystallization with retention of substituent ions in the apatite structure. At high degrees of substitution (
x
= 1, 2), hydroxyapatites are unstable under both heating regimes. Different heating conditions lead to the formation of different impurity phases.
The interpretation of cosmic antiproton flux measurements from space-borne experiments is currently limited by the knowledge of the antiproton production cross-section in collisions between primary ...cosmic rays and the interstellar medium. Using collisions of protons with an energy of 6.5
Te
V
incident on helium nuclei at rest in the proximity of the interaction region of the LHCb experiment, the ratio of antiprotons originating from antihyperon decays to prompt production is measured for antiproton momenta between 12 and
110
Ge
V\!/
c
. The dominant antihyperon contribution, namely
Λ
¯
→
p
¯
π
+
decays from promptly produced
Λ
¯
particles, is also exclusively measured. The results complement the measurement of prompt antiproton production obtained from the same data sample. At the energy scale of this measurement, the antihyperon contributions to antiproton production are observed to be significantly larger than predictions of commonly used hadronic production models.
A
bstract
The first observation of the
Λ
b
0
→
D
s
−
p
decay is presented using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of
s
= 13 TeV, corresponding ...to a total integrated luminosity of 6 fb
−
1
. Using the
Λ
b
0
→
Λ
c
+
π
−
decay as the normalisation mode, the branching fraction of the
Λ
b
0
→
D
s
−
p
decay is measured to be
B
Λ
b
0
→
D
s
−
p
=
12.6
±
0.5
±
0.3
±
1.2
×
10
−
6
, where the first uncertainty is statistical, the second systematic and the third due to uncertainties in the branching fractions of the
Λ
b
0
→
Λ
c
+
π
−
,
D
s
−
→
K
−
K
+
π
−
and
Λ
c
+
→
p
K
−
π
+
decays.
A
bstract
This article presents the first measurement of the differential
Z
-boson production cross-section in the forward region using proton-lead collisions with the LHCb detector. The dataset was ...collected at a nucleon-nucleon centre-of-mass energy of
s
NN
= 8
.
16 TeV in 2016, corresponding to an integrated luminosity of 30
.
8 nb
−
1
. The forward-backward ratio and the nuclear modification factors are measured together with the differential cross-section as functions of the
Z
boson rapidity in the centre-of-mass frame, the transverse momentum of the
Z
boson and a geometric variable
ϕ
*
. The results are in good agreement with the predictions from nuclear parton distribution functions, providing strong constraining power at small Bjorken-
x
.
Observation of the Bs0→ D+D− decay Alessio, F.; Aliouche, Z.; Artamonov, A. ...
The journal of high energy physics,
07/2023, Letnik:
2023, Številka:
7
Journal Article
Recenzirano
Odprti dostop
A
bstract
The first observation of the
B
s
0
→ D
∗+
D
∗
−
decay and the measurement of its branching ratio relative to the
B
0
→ D
∗+
D
∗
−
decay are presented. The data sample used corresponds to an ...integrated luminosity of 9 fb
−
1
of proton-proton collisions recorded by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV between 2011 and 2018. The decay is observed with more than 10 standard deviations and the time-integrated ratio of branching fractions is determined to be
B
B
s
0
→
D
∗
+
D
∗
−
B
B
0
→
D
∗
+
D
∗
−
=
0.269
±
0.032
±
0.011
±
0.008
,
where the first uncertainty is statistical, the second systematic and the third due to the uncertainty of the fragmentation fraction ratio
f
s
/f
d
. The
B
s
0
→ D
*+
D
*
−
branching fraction is calculated to be
B
B
s
0
→
D
∗
+
D
∗
−
=
2.15
±
0.26
±
0.09
±
0.06
±
0.16
×
10
−
4
,
where the fourth uncertainty is due to the
B
0
→ D
*
+
D
*−
branching fraction. These results are calculated using the average
B
s
0
meson lifetime in simulation. Correction factors are reported for scenarios where either a purely heavy or a purely light
B
s
0
eigenstate is considered.
Amplitude analysis of the Ds+→ π−π+π+ decay Amhis, Y.; Andersson, M.; Bachmann, S. ...
The journal of high energy physics,
07/2023, Letnik:
2023, Številka:
7
Journal Article
Recenzirano
Odprti dostop
A
bstract
A Dalitz plot analysis of the
D
s
+
→
π
−
π
+
π
+
decay is presented. The analysis is based on proton-proton collision data recorded by the LHCb experiment at a centre-of-mass energy of 8 ...TeV and corresponding to an integrated luminosity of 1.5 fb
−
1
. The resonant structure of the decay is obtained using a quasi-model-independent partial-wave analysis, in which the
π
+
π
−
S-wave amplitude is parameterised as a generic complex function determined by a fit to the data. The S-wave component is found to be dominant, followed by the contribution from spin-2 resonances and a small contribution from spin-1 resonances. The latter includes the first observation of the
D
s
+
→ ω
(782)
π
+
channel in the
D
s
+
→ π
−
π
+
π
+
decay. The resonant structures of the
D
s
+
→ π
−
π
+
π
+
and
D
+
→ π
−
π
+
π
+
decays are compared, providing information about the mechanisms for the hadron formation in these decays.
The measurement of charmonium states produced in proton-neon (
p
Ne
) collisions by the LHCb experiment in its fixed-target configuration is presented. The production of
J
/
ψ
and
ψ
(
2
S
)
mesons is ...studied with a beam of 2.5
Te
V
protons colliding on gaseous neon targets at rest, corresponding to a nucleon-nucleon centre-of-mass energy
s
NN
=
68.5
Ge
V
. The data sample corresponds to an integrated luminosity of
21.7
±
1.4
nb
-
1
. The
J
/
ψ
and
ψ
(
2
S
)
hadrons are reconstructed in
μ
+
μ
-
final states. The
J
/
ψ
production cross-section per target nucleon in the centre-of-mass rapidity range
y
⋆
∈
-
2.29
,
0
is found to be
506
±
8
±
46
nb/nucleon
. The ratio of
J
/
ψ
and
D
0
cross-sections is evaluated to
(
1.06
±
0.02
±
0.09
)
%
. The
ψ
(
2
S
)
to
J
/
ψ
relative production rate is found to be
(
1.67
±
0.27
±
0.10
)
%
in good agreement with other measurements involving beam and target nuclei of similar sizes.
