Violations of $ CPT$ symmetry and Lorentz invariance are searched for by studying interference effects in $ B^0$ mixing and in $ B^0_s$ mixing. Samples of $ B^0\to J/\psi K^0_{\mathrm{S}}$ and $ ...B^0_s\to J/\psi K^+ K^-$ decays are recorded by the LHCb detector in proton--proton collisions at centre-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb$^{-1}$. No periodic variations of the particle-antiparticle mass differences are found, consistent with Lorentz invariance and $ CPT$ symmetry. Results are expressed in terms of the Standard Model Extension parameter $\Delta a_{\mu}$ with precisions of $ \mathcal{O}(10^{-15})$ and $ \mathcal{O}(10^{-14})$ GeV for the $ B^0$ and $ B^0_s$ systems, respectively. With no assumption on Lorentz (non-)invariance, the $ CPT$-violating parameter $z$ in the $ B^0_s$ system is measured for the first time and found to be $ \mathcal{R}e(z) = -0.022 \pm 0.033 \pm 0.005$ and $ \mathcal{I}m(z) = 0.004 \pm 0.011\pm 0.002$, where the first uncertainties are statistical and the second systematic.
A
bstract
The production of
J/ψ
mesons in proton-proton collisions at a centre-of-mass energy of
s
=
13
TeV is studied with the LHCb detector. Cross-section measurements are performed as a function ...of the transverse momentum
p
T
and the rapidity
y
of the
J/ψ
meson in the region
p
T
<
14 GeV/
c
and 2
.
0
< y <
4
.
5, for both prompt
J/ψ
mesons and
J/ψ
mesons from
b
-hadron decays. The production cross-sections integrated over the kinematic coverage are 15
.
30 ± 0
.
03 ± 0
.
86 μb for prompt
J/ψ
and 2
.
34 ± 0
.
01 ± 0
.
13 μb for
J/ψ
from
b
-hadron decays, assuming zero polarization of the
J/
ψ meson. The first uncertainties are statistical and the second systematic. The cross-section reported for
J/ψ
mesons from
b
-hadron decays is used to extrapolate to a total
b
b
¯
cross-section. The ratios of the cross-sections with respect to
s
=
8
TeV are also determined.
The first observation of the rare decay Bs0→ϕπ+π− and evidence for B0→ϕπ+π− are reported, using pp collision data recorded by the LHCb detector at center-of-mass energies s=7 and 8 TeV, corresponding ...to an integrated luminosity of 3 fb−1. The branching fractions in the π+π− invariant mass range 400<m(π+π−)<1600 MeV/c2 are 3.48±0.23±0.17±0.35×10−6 and 1.82±0.25±0.41±0.14×10−7 for Bs0→ϕπ+π− and B0→ϕπ+π− respectively, where the uncertainties are statistical, systematic and from the normalization mode Bs0→ϕϕ. A combined analysis of the π+π− mass spectrum and the decay angles of the final-state particles identifies the exclusive decays Bs0→ϕf0(980), Bs0→ϕf2(1270), and Bs0→ϕρ0 with branching fractions of 1.12±0.16−0.08+0.09±0.11×10−6, 0.61±0.13−0.05+0.12±0.06×10−6 and 2.7±0.7±0.2±0.2×10−7, respectively.
The LHCb measurement of the lifetime ratio of the Λb0 baryon to the B¯0 meson is updated using data corresponding to an integrated luminosity of 3.0 fb−1 collected using 7 and 8 TeV centre-of-mass ...energy pp collisions at the LHC. The decay modes used are Λb0→J/ψpK− and B¯0→J/ψπ+K−, where the π+K− mass is consistent with that of the K¯⁎0(892) meson. The lifetime ratio is determined with unprecedented precision to be 0.974±0.006±0.004, where the first uncertainty is statistical and the second systematic. This result is in agreement with original theoretical predictions based on the heavy quark expansion. Using the current world average of the B¯0 lifetime, the Λb0 lifetime is found to be 1.479±0.009±0.010 ps.
The production of tt‾, W+bb‾ and W+cc‾ is studied in the forward region of proton–proton collisions collected at a centre-of-mass energy of 8 TeV by the LHCb experiment, corresponding to an ...integrated luminosity of 1.98±0.02 fb−1. The W bosons are reconstructed in the decays W→ℓν, where ℓ denotes muon or electron, while the b and c quarks are reconstructed as jets. All measured cross-sections are in agreement with next-to-leading-order Standard Model predictions.
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.
The polarization of photons produced in radiative B0s decays is studied for the first time. The data are recorded by the LHCb experiment in pp collisions corresponding to an integrated luminosity of ...3 fb–1 at center-of-mass energies of 7 and 8 TeV. A time-dependent analysis of the B0s→Φγ decay rate is conducted to determine the parameter AΔ, which is related to the ratio of right- over left-handed photon polarization amplitudes in b→sγ transitions. A value of AΔ = –0.98+0.46–0.52+0.23–0.20 is measured. This result is consistent with the standard model prediction within 2 standard deviations.
A
bstract
Using three- and four-body decays of
D
mesons produced in semileptonic
b
-hadron decays, precision measurements of
D
meson mass differences are made together with a measurement of the
D
0
...mass. The measurements are based on a dataset corresponding to an integrated luminosity of 1
.
0 fb
−1
collected in
pp
collisions at 7 TeV. Using the decay
D
0
→
K
+
K
−
K
−
π
+
, the
D
0
mass is measured to be
The mass differences
are measured using the
D
0
→
K
+
K
−
π
+
π
−
and
modes.
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.
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