Using pp collision data corresponding to 1.0 fb-1 integrated luminosity collected by the LHCb detector, two narrow states are observed in the Lambda_b0pi+pi- spectrum with masses 5911.95 +- ...0.12(stat) +- 0.03(syst) +- 0.66(Lambda_b0 mass) MeV/c^2 and 5919.76 +- 0.07(stat) +- 0.02(syst) +- 0.66(Lambda_b0 mass) MeV/c^2. The significances of the observations are 4.9 and 10.1 standard deviations, respectively. These states are interpreted as the orbitally-excited Lambda_b0 baryons, Lambda_b*0(5912) and Lambda_b*0(5920).
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 the B0→K+K- decay is performed using p p -collision data collected by LHCb. The data set corresponds to integrated luminosities of 1.0 and 2.0 fb-1 at center-of-mass energies of 7 and 8 ...TeV, respectively. This decay is observed for the first time, with a significance of more than 5 standard deviations. The analysis also results in an improved measurement of the branching fraction for the Bs0→π+π- decay. The measured branching fractions are B (B0→K+K- )=(7.80 ±1.27 ±0.81 ±0.21 )×10-8 and B (Bs0→π+π- )=(6.91 ±0.54 ±0.63 ±0.19 ±0.40 )×10-7 . The first uncertainty is statistical, the second is systematic, the third is due to the uncertainty on the B0→K+π- branching fraction used as a normalization. For the Bs0 mode, the fourth accounts for the uncertainty on the ratio of the probabilities for b quarks to hadronize into Bs0 and B0 mesons.
We report the results of a search for the bottomonium ground state η b ( 1 S ) in the photon energy spectrum with a sample of ( 109 ± 1 ) million of Υ ( 3 S ) recorded at the Υ ( 3 S ) energy with ...the BABAR detector at the PEP-II B factory at SLAC. We observe a peak in the photon energy spectrum at E γ = 921.2 + 2.1 − 2.8 ( stat ) ± 2.4 ( syst ) MeV with a significance of 10 standard deviations. We interpret the observed peak as being due to monochromatic photons from the radiative transition Υ ( 3 S ) → γ η b ( 1 S ) . This photon energy corresponds to an η b ( 1 S ) mass of 9388.9 + 3.1 − 2.3 ( stat ) ± 2.7 ( syst ) MeV / c 2 . The hyperfine Υ ( 1 S ) - η b ( 1 S ) mass splitting is 71.4 + 2.3 − 3.1 ( stat ) ± 2.7 ( syst ) MeV / c 2 . The branching fraction for this radiative Υ ( 3 S ) decay is estimated to be 4.8 ± 0.5 ( stat ) ± 1.2 ( syst ) × 10 − 4 .
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.
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