The production of J/ψ mesons accompanied by open charm, and of pairs of open charm hadrons are observed in pp collisions at a centre-of-mass energy of 7 TeV using an integrated luminosity of 355 pb−1 ...collected with the LHCb detector. Model independent measurements of absolute cross-sections are given together with ratios to the measured J/ψ and open charm cross-sections. The properties of these events are studied and compared to theoretical predictions.
The cross-sections of
ψ
(
2
S
)
meson production in proton-proton collisions at
s
=
13
TeV
are measured with a data sample collected by the LHCb detector corresponding to an integrated luminosity of
...275
pb
-
1
. The production cross-sections for prompt
ψ
(
2
S
)
mesons and those for
ψ
(
2
S
)
mesons from
b
-hadron decays (
ψ
(
2
S
)
-from-
b
) are determined as functions of the transverse momentum,
p
T
, and the rapidity,
y
, of the
ψ
(
2
S
)
meson in the kinematic range
2
<
p
T
<
20
GeV/
c
and
2.0
<
y
<
4.5
. The production cross-sections integrated over this kinematic region are
σ
(
prompt
ψ
(
2
S
)
,
13
TeV
)
=
1.430
±
0.005
(stat)
±
0.099
(syst)
μ
b
,
σ
(
ψ
(
2
S
)
-from-
b
,
13
TeV
)
=
0.426
±
0.002
(stat)
±
0.030
(syst)
μ
b
.
A new measurement of
ψ
(
2
S
)
production cross-sections in
pp
collisions at
s
=
7
TeV
is also performed using data collected in 2011, corresponding to an integrated luminosity of
614
pb
-
1
. The integrated production cross-sections in the kinematic range
3.5
<
p
T
<
14
GeV/
c
and
2.0
<
y
<
4.5
are
σ
(
prompt
ψ
(
2
S
)
,
7
TeV
)
=
0.471
±
0.001
(stat)
±
0.025
(syst)
μ
b
,
σ
(
ψ
(
2
S
)
-from-
b
,
7
TeV
)
=
0.126
±
0.001
(stat)
±
0.008
(syst)
μ
b
.
All results show reasonable agreement with theoretical calculations.
The first study of
C
P
violation in the decay mode
B
±
→
K
+
K
-
π
+
π
-
D
h
±
, with
h
=
K
,
π
, is presented, exploiting a data sample of proton–proton collisions collected by the LHCb experiment ...that corresponds to an integrated luminosity of
9
\,fb
-
1
. The analysis is performed in bins of phase space, which are optimised for sensitivity to local
C
P
asymmetries.
C
P
-violating observables that are sensitive to the angle
γ
of the Unitarity Triangle are determined. The analysis requires external information on charm-decay parameters, which are currently taken from an amplitude analysis of LHCb data, but can be updated in the future when direct measurements become available. Measurements are also performed of phase-space integrated observables for
B
±
→
K
+
K
-
π
+
π
-
D
h
±
and
B
±
→
π
+
π
-
π
+
π
-
D
h
±
decays.
A search for
C
P
violation in charmless four-body decays of
Λ
b
0
and
Ξ
b
0
baryons with a proton and three charged mesons in the final state is performed. To cancel out production and detection ...charge-asymmetry effects, the search is carried out by measuring the difference between the
C
P
asymmetries in a charmless decay and in a decay with an intermediate charmed baryon with the same particles in the final state. The data sample used was recorded in 2011 and 2012 with the LHCb detector and corresponds to an integrated luminosity of
3
fb
-
1
. A total of 18
C
P
asymmetries are considered, either accounting for the full phase space of the decays or exploring specific regions of the decay kinematics. No significant
C
P
-violation effect is observed in any of the measurements.
Abstract
The very rare
$${{D} ^*} (2007)^0\!\rightarrow {\mu ^+\mu ^-} $$
D
∗
(
2007
)
0
→
μ
+
μ
-
decay is searched for by analysing
$${{{B} ^-}} \!\rightarrow {{\pi } ^-} {\mu ^+\mu ^-} $$
B
-
→
π
...-
μ
+
μ
-
decays. The analysis uses a sample of beauty mesons produced in proton–proton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9
$$\text {\,fb} ^{-1}$$
\,fb
-
1
. The signal signature corresponds to simultaneous peaks in the
$${\mu ^+\mu ^-} $$
μ
+
μ
-
and
$${{\pi } ^-} {\mu ^+\mu ^-} $$
π
-
μ
+
μ
-
invariant masses. No evidence for an excess of events over background is observed and an upper limit is set on the branching fraction of the decay at
$$\mathcal{B}({{D} ^*} (2007)^0\!\rightarrow {\mu ^+\mu ^-} ) < 2.6\times 10^{-8}$$
B
(
D
∗
(
2007
)
0
→
μ
+
μ
-
)
<
2.6
×
10
-
8
at
$$90\%$$
90
%
confidence level. This is the first limit on the branching fraction of
$${{D} ^*} (2007)^0\!\rightarrow {\mu ^+\mu ^-} $$
D
∗
(
2007
)
0
→
μ
+
μ
-
decays and the most stringent limit on
$${{D} ^*} (2007)^0$$
D
∗
(
2007
)
0
decays to leptonic final states. The analysis is the first search for a rare charm-meson decay exploiting production via beauty decays.
The production of Upsilon(1S), Upsilon(2S) and Upsilon(3S) mesons in proton-proton collisions at the centre-of-mass energy of sqrt(s)=7 TeV is studied with the LHCb detector. The analysis is based on ...a data sample of 25 pb-1 collected at the Large Hadron Collider. The Upsilon mesons are reconstructed in the decay mode Upsilon -> mu+ mu- and the signal yields are extracted from a fit to the mu+ mu- invariant mass distributions. The differential production cross-sections times dimuon branching fractions are measured as a function of the Upsilon transverse momentum pT and rapidity y, over the range pT < 15 GeV/c and 2.0 < y < 4.5. The cross-sections times branching fractions, integrated over these kinematic ranges, are measured to be sigma(pp -> Upsilon(1S) X) x B(Upsilon(1S)->mu+ mu-) = 2.29 {\pm} 0.01 {\pm} 0.10 -0.37 +0.19 nb, sigma(pp -> Upsilon(2S) X) x B(Upsilon(2S)->mu+ mu-) = 0.562 {\pm} 0.007 {\pm} 0.023 -0.092 +0.048 nb, sigma(pp -> Upsilon(3S) X) x B(Upsilon(3S)->mu+ mu-) = 0.283 {\pm} 0.005 {\pm} 0.012 -0.048 +0.025 nb, where the first uncertainty is statistical, the second systematic and the third is due to the unknown polarisation of the three Upsilon states.
Abstract
The first measurement of
$${{J}/\psi }$$
J
/
ψ
and
$${{D}} ^0$$
D
0
production in PbNe collisions by the LHCb experiment in its fixed-target configuration is reported. The production of
...$${{J}/\psi }$$
J
/
ψ
and
$${{D}} ^0$$
D
0
mesons is studied with a beam of lead ions with an energy of 2.5
$$\,\text {TeV}$$
TeV
per nucleon colliding on gaseous neon targets at rest, corresponding to a nucleon-nucleon centre-of-mass energy of
$$\sqrt{s_{\scriptscriptstyle \text {NN}}} =68.5\,\text {GeV} $$
s
NN
=
68.5
GeV
. The
$${{J}/\psi }$$
J
/
ψ
/
$${{D}} ^0$$
D
0
production cross-section ratio is studied as a function of rapidity, transverse momentum and collision centrality. These data are compared with measurements from
$$p\text {Ne}$$
p
Ne
collisions at the same energy and show no difference in the observed
$${{J}/\psi }$$
J
/
ψ
suppression trend when comparing
$$p\text {Ne}$$
p
Ne
and PbNe peripheral collisions with PbNe central collisions.
The differential cross-section for the inclusive production of ψ(2S) mesons in pp collisions at s√=7 TeVs=7 TeV has been measured with the LHCb detector. The data sample corresponds to an integrated ...luminosity of 36 pb−1. The ψ(2S) mesons are reconstructed in the decay channels ψ(2S)→μ + μ − and ψ(2S)→J/ψπ + π −, with the J/ψ meson decaying into two muons. Results are presented both for promptly produced ψ(2S) mesons and for those originating from b-hadron decays. In the kinematic range p T(ψ(2S))≤16 GeV/c and 2<y(ψ(2S))≤4.5 we measure
https://static-content.springer.com/image/art%3A10.1140%2Fepjc%2Fs10052-012-2100-4/MediaObjects/10052_2012_2100_Equa_HTML.gif
where the last uncertainty on the prompt cross-section is due to the unknown ψ(2S) polarization. Recent QCD calculations are found to be in good agreement with our measurements. Combining the present result with the LHCb J/ψ measurements we determine the inclusive branching fraction
https://static-content.springer.com/image/art%3A10.1140%2Fepjc%2Fs10052-012-2100-4/MediaObjects/10052_2012_2100_Equb_HTML.gif
where the last uncertainty is due to the (b→J/ψX)B(b→J/ψX) , (J/ψ→μ+μ−)B(J/ψ→μ+μ−) and (ψ(2S)→e+e−)B(ψ(2S)→e+e−) branching fraction uncertainties.
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