Using decays to
ϕ
-meson pairs, the inclusive production of charmonium states in
b
-hadron decays is studied with
pp
collision data corresponding to an integrated luminosity of
3.0
fb
-
1
, collected ...by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. Denoting by
B
C
≡
B
(
b
→
C
X
)
×
B
(
C
→
ϕ
ϕ
)
the inclusive branching fraction of a
b
hadron to a charmonium state
C
that decays into a pair of
ϕ
mesons, ratios
R
C
2
C
1
≡
B
C
1
/
B
C
2
are determined as
R
η
c
(
1
S
)
χ
c
0
=
0.147
±
0.023
±
0.011
,
R
η
c
(
1
S
)
χ
c
1
=
0.073
±
0.016
±
0.006
,
R
η
c
(
1
S
)
χ
c
2
=
0.081
±
0.013
±
0.005
,
R
χ
c
0
χ
c
1
=
0.50
±
0.11
±
0.01
,
R
χ
c
0
χ
c
2
=
0.56
±
0.10
±
0.01
and
R
η
c
(
1
S
)
η
c
(
2
S
)
=
0.040
±
0.011
±
0.004
. Here and below the first uncertainties are statistical and the second systematic. Upper limits at 90% confidence level for the inclusive production of
X
(3872),
X
(3915) and
χ
c
2
(
2
P
)
states are obtained as
R
χ
c
1
X
(
3872
)
<
0.34
,
R
χ
c
0
X
(
3915
)
<
0.12
and
R
χ
c
2
χ
c
2
(
2
P
)
<
0.16
. Differential cross-sections as a function of transverse momentum are measured for the
η
c
(
1
S
)
and
χ
c
states. The branching fraction of the decay
B
s
0
→
ϕ
ϕ
ϕ
is measured for the first time,
B
(
B
s
0
→
ϕ
ϕ
ϕ
)
=
(
2.15
±
0.54
±
0.28
±
0
.
21
B
)
×
10
-
6
. Here the third uncertainty is due to the branching fraction of the decay
B
s
0
→
ϕ
ϕ
, which is used for normalization. No evidence for intermediate resonances is seen. A preferentially transverse
ϕ
polarization is observed. The measurements allow the determination of the ratio of the branching fractions for the
η
c
(
1
S
)
decays to
ϕ
ϕ
and
p
p
¯
as
B
(
η
c
(
1
S
)
→
ϕ
ϕ
)
/
B
(
η
c
(
1
S
)
→
p
p
¯
)
=
1.79
±
0.14
±
0.32
.
A search for the decay
K
S
0
→
μ
+
μ
-
is performed, based on a data sample of proton-proton collisions corresponding to an integrated luminosity of
3
fb
-
1
, collected by the LHCb experiment at ...centre-of-mass energies of 7 and 8
TeV
. The observed yield is consistent with the background-only hypothesis, yielding a limit on the branching fraction of
B
(
K
S
0
→
μ
+
μ
-
)
<
0.8
(
1.0
)
×
10
-
9
at
90
%
(
95
%
)
confidence level. This result improves the previous upper limit on the branching fraction by an order of magnitude.
Evidence for the decay BS0→K¯∗0μ+μ Albrecht, J.; Andreotti, M.; Archilli, F. ...
The journal of high energy physics,
3/7, Letnik:
2018, Številka:
7
Journal Article
Recenzirano
Odprti dostop
A
bstract
A search for the decay
B
S
0
→
K
¯
∗
0
μ
+
μ
−
is presented using data sets corresponding to 1.0, 2.0 and 1.6 fb
−1
of integrated luminosity collected during
pp
collisions with the LHCb ...experiment at centre-of-mass energies of 7, 8 and 13 TeV, respectively. An excess is found over the background-only hypothesis with a significance of 3.4 standard deviations. The branching fraction of the
B
S
0
→
K
¯
∗
0
μ
+
μ
−
decay is determined to be
ℬ
B
s
0
→
K
¯
∗
0
μ
+
μ
−
=
2.9
±
1.0
stat
±
0.2
syst
±
0.3
norm
×
10
−
8
, where the first and second uncertainties are statistical and systematic, respectively. The third uncertainty is due to limited knowledge of external parameters used to normalise the branching fraction measurement.
A
bstract
The
CP
asymmetry in
B
−
→
D
s
−
D
0
and
B
−
→
D
−
D
0
decays is measured using LHCb data corresponding to an integrated luminosity of 3.0 fb
−1
, collected in
pp
collisions at ...centre-of-mass energies of 7 and 8 TeV. The results are
A
C
P
B
−
→
D
s
−
D
0
=
−
0.4
±
0.5
±
0.5
%
and
A
C
P
B
−
→
D
−
D
0
=
2.3
±
2.7
±
0.4
%
, where the first uncertainties are statistical and the second systematic. This is the first measurement of
A
C
P
B
−
→
D
s
−
D
0
and the most precise determination of
A
C
P
B
−
→
D
−
D
0
. Neither result shows evidence of
CP
violation.
Measurements of CP violation are a core part of the LHCb physics programme and provide sensitivity to angles of the CKM matrix as well as searching for evidence of physics beyond the Standard Model. ...A summary of recent B → DX results from LHCb are presented, including the time-dependent B 0 → D ∓π± analysis which profits from the largest flavour tagged sample analysed by LHCb, the world's first observation of the B + → DsKK and the world's most precise (first) measurements of the CP asymmetry in B − → D ( s ) − D 0 decays.
A
bstract
A test of lepton universality, performed by measuring the ratio of the branching fractions of the
B
0
→
K
*0
μ
+
μ
−
and
B
0
→
K
*0
e
+
e
−
decays,
R
K
*
0
, is presented. The
K
*0
meson is ...reconstructed in the final state
K
+
π
−
, which is required to have an invariant mass within 100 MeV
/c
2
of the known
K
*
(892)
0
mass. The analysis is performed using proton-proton collision data, corresponding to an integrated luminosity of about 3 fb
−1
, collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The ratio is measured in two regions of the dilepton invariant mass squared,
q
2
, to be
R
K
*
0
=
0.66
−
+
0.07
0.11
stat
±
0.03
syst
f
o
r
0.045
<
q
2
<
1.1
GeV
2
/
c
4
,
0.69
−
+
0.07
0.11
stat
±
0.05
syst
f
o
r
1.1
<
q
2
<
6.0
GeV
2
/
c
4
.
The corresponding 95.4% confidence level intervals are 0
.
52
,
0
.
89 and 0
.
53
,
0
.
94. The results, which represent the most precise measurements of
R
K
*
0
to date, are compatible with the Standard Model expectations at the level of 2.1–2.3 and 2.4–2.5 standard deviations in the two
q
2
regions, respectively.
A
bstract
The decays of
B
s
0
and
B
¯
s
0
mesons into the
J/ψK
+
K
−
final state are studied in the
K
+
K
−
mass region above the
ϕ
(1020) meson in order to determine the resonant substructure and ...measure the
CP
-violating phase,
ϕ
s
, the decay width, Γ
s
, and the width difference between light and heavy mass eigenstates, ΔΓ
s
. A decay-time dependent amplitude analysis is employed. The data sample corresponds to an integrated luminosity of 3 fb
−1
produced in 7 and 8 TeV
pp
collisions at the LHC, collected by the LHCb experiment. The measurement determines
ϕ
s
= 119 ± 107 ± 34 mrad. A combination with previous LHCb measurements using similar decays into the
J/ψπ
+
π
−
and
J/ψϕ
(1020) final states gives
ϕ
s
= 1 ± 37 mrad, consistent with the Standard Model prediction.
At the LHC era, the detector systems are operating at the harsh hadronic environment with the unprecedentedly high particle flux. Position-sensitive silicon devices are usually positioned at the ...innermost regions of the experimental setups and must cope with highly non-uniform radiation fields. At the end of LHC Run 2, fluence in silicon trackers reached 10
15
n
eq
/cm
2
. Initial simulation studies predict that the maximal fluence for the HL-LHC may be up to two orders of magnitude higher than the one seen in LHC Run 1 and Run 2. In this paper, two general-purpose physics event generators used for simulation of proton–proton collisions for the radiation damage studies at LHC energies: PYTHIA 8.2 and
Dpmjet
-III are compared. Fluences obtained using these models, with the latest tuning to the LHC data, in detectors situated close to the proton–proton interaction point are determined as well. We also indicate a potential new method for actual fluence estimation using experiment real-time data monitoring system.
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