A
bstract
Time-integrated
CP
asymmetries in
D
0
decays to the final states
K
−
K
+
and
π
−
π
+
are measured using proton-proton collisions corresponding to 3fb
−1
of integrated luminosity collected ...at centre-of-mass energies of 7 TeV and 8 TeV. The
D
0
mesons are produced in semileptonic
b
-hadron decays, where the charge of the accompanying muon is used to determine the initial flavour of the charm meson. The difference in
CP
asymmetries between the two final states is measured to be
Δ
A
CP
=
A
CP
K
−
K
+
−
A
CP
π
−
π
+
=
+
0.14
±
0.16
stat
±
0.08
syst
%
.
A measurement of
A
CP
(
K
−
K
+
) is obtained assuming negligible
CP
violation in charm mixing and in Cabibbo-favoured
D
decays. It is found to be
A
CP
K
−
K
+
=
−
0.06
±
0.15
stat
±
0.10
syst
%
,
where the correlation coefficient between Δ
A
CP
and
A
CP
(
K
−
K
+
) is
ρ
= 0
.
28. By combining these results, the
CP
asymmetry in the
D
0
→
π
−
π
+
channel is
A
CP
(
π
−
π
+
) = (−0
.
20 ± 0
.
19 (stat) ± 0
.
10 (syst))%.
A
bstract
The kinematic dependences of the relative production rates,
f
Λ
b
0
/
f
d
, of
Λ
b
0
baryons and
B
0
mesons are measured using
Λ
b
0
→
Λ
c
+
π
−
and
B
¯
0
→
D
+
π
−
decays. The ...measurements use proton-proton collision data, corresponding to an integrated luminosity of 1 fb
−1
at a centre-of-mass energy of 7 TeV, recorded in the forward region with the LHCb experiment. The relative production rates are observed to depend on the transverse momentum,
p
T
, and pseudorapidity,
η
, of the beauty hadron, in the studied kinematic region 1
.
5
< p
T
<
40 GeV
/c
and 2
< η <
5. Using a previous LHCb measurement of
f
Λ
b
0
/
f
d
in semileptonic decays, the branching fraction ℬ(
Λ
b
0
→
Λ
c
+
π
−
) = (4.30 ± 0.03
− 0.11
+ 0.12
± 0.26 ± 0.21) × 10
− 3
is obtained, where the first uncertainty is statistical, the second is systematic, the third is from the previous LHCb measurement of
f
Λ
b
0
/
f
d
and the fourth is due to the b
B
¯
0
→
D
+
π
−
branching fraction. This is the most precise measurement of a
Λ
b
0
branching fraction to date.
The asymmetry in the production cross-section σ of D± mesons,AP=σ(D+)−σ(D−)σ(D+)+σ(D−), is measured in bins of pseudorapidity η and transverse momentum pT within the acceptance of the LHCb detector. ...The result is obtained with a sample of D+→KS0π+ decays corresponding to an integrated luminosity of 1.0 fb−1, collected in pp collisions at a centre of mass energy of 7 TeV at the Large Hadron Collider. When integrated over the kinematic range 2.0<pT<18.0 GeV/c and 2.20<η<4.75, the production asymmetry is AP=(−0.96±0.26±0.18)%. The uncertainties quoted are statistical and systematic, respectively. The result assumes that any direct CP violation in the D+→KS0π+ decay is negligible. No significant dependence on η or pT is observed.
A search for non-resonant D(s)+→π+μ+μ− and D(s)+→π−μ+μ+ decays is performed using proton–proton collision data, corresponding to an integrated luminosity of 1.0 fb−1, at s=7TeV recorded by the LHCb ...experiment in 2011. No signals are observed and the 90% (95%) confidence level (CL) limits on the branching fractions are found to beB(D+→π+μ+μ−)<7.3(8.3)×10−8,B(Ds+→π+μ+μ−)<4.1(4.8)×10−7,B(D+→π−μ+μ+)<2.2(2.5)×10−8,B(Ds+→π−μ+μ+)<1.2(1.4)×10−7. These limits are the most stringent to date.
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