A search for the doubly charmed baryon Xi_cc^+ in the decay mode Xi_cc^+ -> Lambda_c^+ K^- pi^+ is performed with a data sample, corresponding to an integrated luminosity of 0.65/fb, of pp collisions ...recorded at a centre-of-mass energy of 7 TeV. No significant signal is found in the mass range 3300-3800 MeV/c^2. Upper limits at the 95% confidence level on the ratio of the Xi_cc^+ production cross-section times branching fraction to that of the Lambda_c^+, R, are given as a function of the Xi_cc^+ mass and lifetime. The largest upper limits range from R < 1.4 x 10^-2 for a lifetime of 100 fs to R < 3.4 x 10^-4 for a lifetime of 400 fs.
An analysis of B±→DK± and B±→Dπ± decays is presented where the D meson is reconstructed in the two-body final states: K±π∓, K+K− and π+π−. Using 1.0 fb−1 of s=7TeVpp collisions, measurements of ...several observables are made including the first observation of the suppressed mode B±→π±K∓DK±. CP violation in B±→DK± decays is observed with 5.8σ significance.
Amplitude models are applied to studies of resonance structure in D 0 → K 0 S K − π + and D 0 → K 0 S K + π − decays using p p collision data corresponding to an integrated luminosity of 3.0 fb − ...1 collected by the LHCb experiment. Relative magnitude and phase information is determined, and coherence factors and related observables are computed for both the whole phase space and a restricted region of 100 MeV / c 2 around the K ∗ ( 892 ) ± resonance. Two formulations for the K π S -wave are used, both of which give a good description of the data. The ratio of branching fractions B ( D 0 → K 0 S K + π − ) / B ( D 0 → K 0 S K − π + ) is measured to be 0.655 ± 0.004 ( stat ) ± 0.006 ( syst ) over the full phase space and 0.370 ± 0.003 ( stat ) ± 0.012 ( syst ) in the restricted region. A search for C P violation is performed using the amplitude models and no significant effect is found. Predictions from SU(3) flavor symmetry for K ∗ ( 892 ) K amplitudes of different charges are compared with the amplitude model results.
A
bstract
The production of
ψ
(2
S
) mesons is studied in dimuon final states using proton-lead (
p
Pb) collision data collected by the LHCb detector. The data sample corresponds to an integrated ...luminosity of 1
.
6 nb
−1
. The nucleon-nucleon centre-of-mass energy of the
p
Pb collisions is
s
N
N
=
5
TeV. The measurement is performed using
ψ
(2
S
) mesons with transverse momentum less than 14 GeV/
c
and rapidity
y
in the ranges 1
.
5
< y <
4
.
0 and −5
.
0
< y <
−2
.
5 in the nucleon-nucleon centre-of-mass system. The forward-backward production ratio and the nuclear modification factor are determined for
ψ
(2
S
) mesons. Using the production cross-section results of
ψ
(2
S
) and
J/ψ
mesons from
b
-hadron decays, the
b
b
¯
cross-section in
p
Pb collisions at
s
N
N
=
5
TeV is obtained.
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.
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.
A search for the decays Bc+→J/ψD(*)0K+ and Bc+→J/ψD(*)+K*0 is performed with data collected at the LHCb experiment corresponding to an integrated luminosity of 3 fb−1. The decays Bc+→J/ψD0K+ and ...Bc+→J/ψD*0K+ are observed for the first time, while first evidence is reported for the Bc+→J/ψD*+K*0 and Bc+→J/ψD+K*0 decays. The branching fractions of these decays are determined relative to the Bc+→J/ψπ+ decay. The Bc+ mass is measured, using the J/ψD0K+ final state, to be 6274.28±1.40(stat)±0.32(syst) MeV/c2. This is the most precise single measurement of the Bc+ mass to date.
A
bstract
The production of Υ mesons in pp collisions at
s
=
7
and 8 TeV is studied with the LHCb detector using data samples corresponding to an integrated luminosity of 1 fb
−1
and 2 fb
−1
...respectively. The production cross-sections and ratios of cross-sections are measured as functions of the meson transverse momentum
p
and rapidity
y
, for
p <
30 GeV
/c
and 2
.
0
< y <
4
.
5.
The polarisation of prompt
ψ
(
2
S
)
mesons is measured by performing an angular analysis of
ψ
(
2
S
)
→
μ
+
μ
-
decays using proton-proton collision data, corresponding to an integrated luminosity ...of 1.0
fb
-
1
, collected by the LHCb detector at a centre-of-mass energy of 7 TeV. The polarisation is measured in bins of transverse momentum
p
T
and rapidity
y
in the kinematic region
3.5
<
p
T
<
15
GeV
/
c
and
2.0
<
y
<
4.5
, and is compared to theoretical models. No significant polarisation is observed.
The first study is presented of CP violation with an amplitude analysis of the Dalitz plot of B0 → DK+π– decays, with D → K+π–, K+K–, and π+π–. The analysis is based on a data sample corresponding to ...3.0 fb–1 of pp collisions collected with the LHCb detector. No significant CP violation effect is seen, and constraints are placed on the angle γ of the unitarity triangle formed from elements of the Cabibbo-Kobayashi-Maskawa quark mixing matrix. Hadronic parameters associated with the B0 → DK*(892)0 decay are determined for the first time. These measurements can be used to improve the sensitivity to γ of existing and future studies of the B0 → DK*(892)0 decay.
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