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.
Using a pp collision data sample corresponding to an integrated luminosity of 3.0 fb–1, collected by the LHCb detector, we present the first search for the strangeness-changing weak decay Ξb– → ...Λ0bπ–. No b hadron decay of this type has been seen before. A signal for this decay, corresponding to a significance of 3.2 standard deviations, is reported.
The prompt production of the charmonium χc1 and χc2 mesons has been studied in proton–proton collisions at the Large Hadron Collider at a centre-of-mass energy of s=7 TeV. The χc mesons are ...identified through their decays χc→J/ψγ with J/ψ→μ+μ− using 36 pb−1 of data collected by the LHCb detector in 2010. The ratio of the prompt production cross-sections for the two χc spin states, σ(χc2)/σ(χc1), has been determined as a function of the J/ψ transverse momentum, pTJ/ψ, in the range from 2 to 15 GeV/c. The results are in agreement with the next-to-leading order non-relativistic QCD model at high pTJ/ψ and lie consistently above the pure leading-order colour-singlet prediction.
A search for the lepton-flavor-violating decays B 0 s → e ± μ ∓ and B 0 → e ± μ ∓ is performed with a data sample, corresponding to an integrated luminosity of 1.0 fb − 1 of p p collisions at √ s ...= 7 TeV , collected by the LHCb experiment. The observed number of B 0 s → e ± μ ∓ and B 0 → e ± μ ∓ candidates is consistent with background expectations. Upper limits on the branching fractions of both decays are determined to be B ( B 0 s → e ± μ ∓ ) < 1.1 ( 1.4 ) × 10 − 8 and B ( B 0 → e ± μ ∓ ) < 2.8 ( 3.7 ) × 10 − 9 at 90% (95%) confidence level (C.L.). These limits are a factor of 20 lower than those set by previous experiments. Lower bounds on the Pati-Salam leptoquark masses are also calculated, M LQ ( B 0 s → e ± μ ∓ ) > 101 TeV / c 2 and M LQ ( B 0 → e ± μ ∓ ) > 126 TeV / c 2 at 95% C.L., and are a factor of 2 higher than the previous bounds.
A
bstract
A measurement of the inclusive
W
→
μν
production cross-section using data from
pp
collisions at a centre-of-mass energy of
s
=
7
TeV is presented. The analysis is based on an integrated ...luminosity of about 1
.
0 fb
−1
recorded with the LHCb detector. Results are reported for muons with a transverse momentum greater than 20 GeV/
c
and pseudorapidity between 2.0 and 4.5. The
W
+
and
W
−
production cross-sections are measured to be
σ
W
+
→
μ
+
ν
=
861.0
±
2.0
±
11.2
±
14.7
p
b
,
σ
W
−
→
μ
−
ν
¯
=
675.8
±
1.9
±
8.8
±
11.6
p
b
,
where the first uncertainty is statistical, the second is systematic and the third is due to the luminosity determination. Cross-section ratios and differential distributions as functions of the muon pseudorapidity are also presented. The ratio of
W
+
to
W
−
cross-sections in the same fiducial kinematic region is determined to be
σ
W
+
→
μ
+
ν
σ
W
−
→
μ
−
ν
¯
=
1.274
±
0.005
±
0.009
,
where the uncertainties are statistical and systematic, respectively. Results are in good agreement with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics.
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.
Decays of Bs and B0 mesons into J/\psi \pi +\pi -\pi +\pi - final states, produced in pp collisions at the LHC, are investigated using data corresponding to an integrated luminosity of 3/fb collected ...with the LHCb detector. B^0_(s) -> J\psi f_1(1285) decays are seen for the first time, and the branching fractions are measured. Using these rates, the f_1(1285) mixing angle between strange and non-strange components of its wave function in the q-qbar structure model is determined to be \pm (24.0^{+3.1+0.6}_{-2.6-0.8}) degrees. Implications on the possible tetraquark nature of the f_1(1285) are discussed.
CP violation in charm and beauty decays at LHCb Pepe Altarelli, M.
Nuclear physics. B, Proceedings supplement/Nuclear physics. B, Proceedings supplements,
08/2013, Letnik:
241-242
Journal Article
Odprti dostop
LHCb is a dedicated heavy flavour physics precision experiment at the LHC searching for New Physics (NP) beyond the Standard Model (SM) through the study of very rare decays of beauty and ...charm-flavoured hadrons and precision measurements of CP-violating observables. In this review I will present a selection of recent precision measurements of CP-violating observables in the decays of beauty and charm-flavoured hadrons. These measurements are based on an integrated luminosity of up to 1.0 fb−1 collected by LHCb in 2011.
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