A
bstract
A search for the lepton-flavour violating decays
B
s
0
→
e
±
μ
∓
and
B
0
→
e
±
μ
∓
is performed based on a sample of proton-proton collision data corresponding to an integrated ...luminosity of 3 fb
−1
, collected with the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The observed yields are consistent with the background-only hypothesis. Upper limits on the branching fraction of the
B
s
0
→
e
±
μ
∓
decays are evaluated both in the hypotheses of an amplitude completely dominated by the heavy eigenstate and by the light eigenstate. The results are
$$ \frac{@}{@}\mathrm{\mathcal{B}}\left({B}_s^0\to {e}^{\pm }{\mu}^{\mp}\right)<6.3(5.4)\times 1{0}^{-9} $$
@
@
ℬ
B
s
0
→
e
±
μ
∓
<
6.3
5.4
×
1
0
−
9
and
$$ \frac{@}{@}\mathrm{\mathcal{B}}\left({B}_s^0\to {e}^{\pm }{\mu}^{\mp}\right)<7.2(6.0)\times 1{0}^{-9} $$
@
@
ℬ
B
s
0
→
e
±
μ
∓
<
7.2
6.0
×
1
0
−
9
at 95% (90%) confidence level, respectively. The upper limit on the branching fraction of the
B
0
→
e
±
μ
∓
decay is also evaluated, obtaining
$$ \frac{@}{@}\mathrm{\mathcal{B}}\left({B}^0\to {e}^{\pm }{\mu}^{\mp}\right)<1.3(1.0)\times 1{0}^{-9} $$
@
@
ℬ
B
0
→
e
±
μ
∓
<
1.3
1.0
×
1
0
−
9
at 95% (90%) confidence level. These are the strongest limits on these decays to date.
A flavour-tagged decay-time-dependent amplitude analysis of B s o → (K+π–)(K–π+) decays is presented in the K±π∓ mass range from 750 to 1600MeV/c2. The analysis uses pp collision data collected with ...the LHCb detector at centre-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0 fb–1. Several quasi-two-body decay modes are considered, corresponding to K±π∓ combinations with spin 0, 1 and 2, which are dominated by the K o * (800)0 and K o * (1430)o, the K*(892)o and the K 2 * (1430)o resonances, respectively. The longitudinal polarisation fraction for the B0s → K*(892)°K¯*(892)0 decay is measured as fL = 0.208 ± 0.032 ± 0.046, where the first uncertainty is statistical and the second is systematic. The first measurement of the mixing-induced CP-violating phase, $ {\phi}_s^{d\overline{d}} $, in b → dd¯s transitions is performed, yielding a value of $ {\phi}_s^{d\overline{d}} $ = –0.10 ± 0.13 (stat) ± 0.14 (syst) rad.
We report the measurement of the direct CP asymmetry in the radiative B¯→ Xs+dγ decay using a data sample of (772 ± 11) × 106 BB¯ pairs collected at the Υ(4S) resonance with the Belle detector at the ...KEKB asymmetric-energy e+e– collider. Here, the CP asymmetry is measured as a function of the photon energy threshold. For E$^{*}_{γ}$ ≥ 2.1 GeV, where E$^{*}_{γ}$ is the photon energy in the center-of-mass frame, we obtain ACP(B¯ → Xs+dγ) = (2.2 ± 3.9 ± 0.9)%, consistent with the standard model prediction.
The decay Z → b b ¯ is reconstructed in pp collision data, corresponding to 2 fb-1 of integrated luminosity, collected by the LHCb experiment at a centre-of-mass energy of s = 8 TeV. The product of ...the Z production cross-section and the Z → b b ¯ branching fraction is measured for candidates in the fiducial region defined by two particle-level b-quark jets with pseudorapidities in the range 2.2 < η < 4.2 , with transverse momenta p T > 20 GeV and dijet invariant mass in the range 45 < m j j < 165 GeV. From a signal yield of 5462 ± 763 Z → b b ¯ events, where the uncertainty is statistical, a production cross-section times branching fraction of 332 ± 46 ± 59 pb is obtained, where the first uncertainty is statistical and the second systematic. The measured significance of the signal yield is 6.0 standard deviations. This measurement represents the first observation of the Z → b b ¯ production in the forward region of pp collisions.
A search for charmless four-body decays of Λ o b and Ξ o b baryons with a proton and three charged mesons (either kaons or pions) in the final state is performed. The data sample used was recorded in ...2011 and 2012 with the LHCb experiment and corresponds to an integrated luminosity of 3 fb–1. Six decay modes are observed, among which Λ o b → pK–π+π–, Λ o b → pK–K+K–, Ξ o b → pK–π+π– and Ξ o b → pK–π+K– are established for the first time. Their branching fractions (including the ratio of hadronisation fractions in the case of the Ξ o b baryon) are determined relative to the Λ o b → Λ c+ π– decay.
A
bstract
We report the measurements of the
CP
-violating parameters in
B
s
0
→
D
s
∓
K
±
decays observed in
pp
collisions, using a data set corresponding to an integrated luminosity of 3.0 fb
−1
...recorded with the LHCb detector. We measure
C
f
= 0
.
73 ± 0
.
14 ± 0
.
05,
A
f
ΔΓ
= 0.39 ± 0.28 ± 0.15,
$$ {A}_{\overline{f}}^{\varDelta \varGamma }=0.31\pm 0.28\pm 0.15 $$
A
f
¯
Δ
Γ
=
0.31
±
0.28
±
0.15
,
S
f
= −0
.
52 ± 0
.
20 ± 0
.
07,
$$ {S}_{\overline{f}}=-0.49\pm 0.20\pm 0.07 $$
S
f
¯
=
−
0.49
±
0.20
±
0.07
, where the uncertainties are statistical and systematic, respectively. These parameters are used together with the world-average value of the
B
s
0
mixing phase, −2
β
s
, to obtain a measurement of the CKM angle γ from
B
s
0
→
D
s
∓
K
±
decays, yielding
γ
= (128
− 22
+ 17
)
°
modulo 180°, where the uncertainty contains both statistical and systematic contributions. This corresponds to 3
.
8
σ
evidence for
CP
violation in the interference between decay and decay after mixing.
PDF
