Angular analysis of the rare decay Bs0→ ϕμ+μ Ackernley, T.; Balagura, V.; Belyaev, I. ...
The journal of high energy physics,
11/2021, Letnik:
2021, Številka:
11
Journal Article
Recenzirano
Odprti dostop
A
bstract
An angular analysis of the rare decay
B
s
0
→ ϕμ
+
μ
−
is presented, using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, ...corresponding to an integrated luminosity of 8.4 fb
−
1
. The observables describing the angular distributions of the decay
B
s
0
→ ϕμ
+
μ
−
are determined in regions of
q
2
, the square of the dimuon invariant mass. The results are consistent with Standard Model predictions.
Precision measurement of the Ξcc++ mass Alexander, M.; Alves, A. A.; Baryshnikov, F. ...
The journal of high energy physics,
02/2020, Letnik:
2020, Številka:
2
Journal Article
Recenzirano
Odprti dostop
A
bstract
A measurement of the
Ξ
cc
+
+
mass is performed using data collected by the LHCb experiment between 2016 and 2018 in
pp
collisions at a centre-of-mass energy of 13 TeV, corresponding to an ...integrated luminosity of 5
.
6 fb
−
1
. The
Ξ
cc
+
+
candidates are reconstructed via the decay modes
Ξ
cc
+
+
→
Λ
c
+
K
−
π
+
π
+
and
Ξ
cc
+
+
→
Ξ
c
+
π
+
. The result, 3621
.
55
±
0
.
23 (stat)
±
0
.
30 (syst) MeV/
c
2
, is the most precise measurement of the
Ξ
cc
+
+
mass to date.
Precision measurement of the Bc+ meson mass Alexander, M.; Alkhazov, G.; Aslanides, E. ...
The journal of high energy physics,
07/2020, Letnik:
2020, Številka:
7
Journal Article
Recenzirano
Odprti dostop
A
bstract
A precision measurement of the
B
c
+
meson mass is performed using proton- proton collision data collected with the LHCb experiment at centre-of-mass energies of 7
,
8 and 13 TeV, ...corresponding to a total integrated luminosity of 9
.
0 fb
−
1
. The
B
c
+
mesons are reconstructed via the decays
B
c
+
→ J/ψπ
+
,
B
c
+
→ J/ψπ
+
π
−
π
+
,
B
c
+
→
J
/
ψp
p
¯
π
+
,
B
c
+
→
J
/
ψ
D
s
+
,
B
c
+
→ J/ψ D
0
K
+
and
B
c
+
→
B
s
0
π
+
. Combining the results of the individual decay channels, the
B
c
+
mass is measured to be 6274
.
47
±
0
.
27 (stat)
±
0
.
17 (syst) MeV
/c
2
. This is the most precise measurement of the
B
c
+
mass to date. The difference between the
B
c
+
and
B
s
0
meson masses is measured to be 907
.
75
±
0
.
37 (stat)
±
0
.
27 (syst) MeV
/c
.
A
bstract
A search is presented for the lepton flavour violating decay
B
+
→
K
+
μ
−
τ
+
using a sample of proton-proton collisions at centre-of-mass energies of 7, 8, and 13 TeV, collected with the ...LHCb detector and corresponding to a total integrated luminosity of 9 fb
−
1
. The
τ
leptons are selected inclusively, primarily via decays with a single charged particle. The four-momentum of the
τ
lepton is determined by using
B
+
mesons from
B
s
2
∗
0
→
B
+
K
−
decays. No significant excess is observed, and an upper limit is set on the branching fraction
ℬ(
B
+
→
K
+
μ
−
τ
+
) < 3.9 × 10
−5
at 90 % confidence level.
The obtained limit is comparable to the world-best limit.
A
bstract
The differential cross-section of prompt inclusive production of long-lived charged particles in proton-proton collisions is measured using a data sample recorded by the LHCb experiment at ...a centre-of-mass energy of
s
= 13 TeV. The data sample, collected with an unbiased trigger, corresponds to an integrated luminosity of 5
.
4 nb
−
1
. The differential cross-section is measured as a function of transverse momentum and pseudorapidity in the ranges
p
T
∈ 80
,
10 000) MeV
/c
and
η
∈ 2
.
0
,
4
.
8) and is determined separately for positively and negatively charged particles. The results are compared with predictions from various hadronic-interaction models.
A
bstract
The production cross-section of the
χ
c
1
(3872) state relative to the
ψ
(2
S
) meson is measured using proton-proton collision data collected with the LHCb experiment at centre-of-mass ...energies of
s
= 8 and 13 TeV, corresponding to integrated luminosities of 2.0 and 5.4 fb
−
1
, respectively. The two mesons are reconstructed in the
J/ψπ
+
π
−
final state. The ratios of the prompt and nonprompt
χ
c
1
(3872) to
ψ
(2
S
) production cross-sections are measured as a function of transverse momentum,
p
T
, and rapidity,
y
, of the
χ
c
1
(3872) and
ψ
(2
S
) states, in the kinematic range 4
< p
T
<
20 GeV/
c
and 2
.
0
< y <
4
.
5. The prompt ratio is found to increase with
p
T
, independently of
y
. For the prompt component, the double ratio of the
χ
c
1
(3872) and
ψ
(2
S
) production cross-sections between 13 and 8 TeV is observed to be consistent with unity, independent of
p
T
and centre-of-mass energy.
A
bstract
The production cross-sections of
J/ψ
mesons in proton-proton collisions at a centre-of-mass energy of
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
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
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
s
NN
= 5 TeV. The results are compared with theoretical predictions.
A
bstract
Using proton-proton collision data, corresponding to an integrated luminosity of 9 fb
−
1
collected with the LHCb detector, seven decay modes of the
B
c
+
meson into a J
/
ψ or ψ(2S) meson ...and three charged hadrons, kaons or pions, are studied. The decays
B
c
+
→ (ψ(2S) → J
/
ψπ
+
π
−
)π
+
,
B
c
+
→ ψ(2S)π
+
π
−
π
+
,
B
c
+
→ J
/
ψK
+
π
−
π
+
and
B
c
+
→ J
/
ψK
+
K
−
K
+
are observed for the first time, and evidence for the
B
c
+
→ ψ(2S)K
+
K
−
π
+
, decay is found, where J
/
ψ and ψ(2S) mesons are reconstructed in their dimuon decay modes. The ratios of branching fractions between the different
B
c
+
decays are reported as well as the fractions of the decays proceeding via intermediate resonances. The results largely support the factorisation approach used for a theoretical description of the studied decays.
A
bstract
This paper presents an analysis of the
Λ
b
0
→ J/ψ
Λ angular distribution and the transverse production polarisation of
Λ
b
0
baryons in proton-proton collisions at centre-of-mass energies ...of 7, 8 and 13 TeV. The measurements are performed using data corresponding to an integrated luminosity of 4.9 fb
−
1
, collected with the LHCb experiment. The polarisation is determined in a fiducial region of
Λ
b
0
transverse momentum and pseudorapidity of 1
< p
T
<
20 GeV/
c
and 2
< η <
5, respectively. The data are consistent with
Λ
b
0
baryons being produced unpolarised in this region. The parity-violating asymmetry parameter of the Λ →
pπ
−
decay is also determined from the data and its value is found to be consistent with a recent measurement by the BES III collaboration.
A
bstract
A search is performed for rare and forbidden charm decays of the form
D
s
+
→
h
±
ℓ
+
ℓ
′
∓
, where
h
±
is a pion or kaon and
ℓ
(′)±
is an electron or muon. The measurements are performed ...using proton-proton collision data, corresponding to an integrated luminosity of 1
.
6 fb
−
1
, collected by the LHCb experiment in 2016. No evidence is observed for the 25 decay modes that are investigated and 90 % confidence level limits on the branching fractions are set between 1
.
4
×
10
−
8
and 6
.
4
×
10
−
6
. In most cases, these results represent an improvement on existing limits by one to two orders of magnitude.
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