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 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.
Production cross-sections of prompt charm mesons are measured using data from pp collisions at the LHC at a centre-of-mass energy of 5TeV. The data sample corresponds to an integrated luminosity of ...8.60±0.33pb−1 collected by the LHCb experiment. The production cross-sections of D0, D+, D+s, and D∗+ mesons are measured in bins of charm meson transverse momentum, pT, and rapidity, y. They cover the rapidity range 2.0<y<4.5 and transverse momentum ranges 0<pT<10GeV/c for D0 and D+ and 1<pT<10GeV/c for D+s and D∗+ mesons. The inclusive cross-sections for the four mesons, including charge-conjugate states, within the range of 1<pT<8GeV/c are determined to beσ(pp→D0X)=1190±3±64μbσ(pp→D+X)=456±3±34μbσ(pp→D+sX)=195±4±19μbσ(pp→D∗+X)=467±6±40μbwhere the uncertainties are statistical and systematic, respectively.
The first measurements of the forward-backward asymmetry of the dimuon pair (AFB), the triple-product asymmetry (A2ϕ), and the charge-parity-conjugation asymmetry (ACP), in D0→π+π−μ+μ− and ...D0→K+K−μ+μ− decays are reported. They are performed using data from proton-proton collisions collected with the LHCb experiment from 2011 to 2016, corresponding to a total integrated luminosity of 5 fb−1. The asymmetries are measured to be AFB(D0→π+π−μ+μ−)=(3.3±3.7±0.6)%, A2ϕ(D0→π+π−μ+μ−)=(−0.6±3.7±0.6)%, ACP(D0→π+π−μ+μ−)=(4.9±3.8±0.7)%, AFB(D0→K+K−μ+μ−)=(0±11±2)%, A2ϕ(D0→K+K−μ+μ−)=(9±11±1)%, ACP(D0→K+K−μ+μ−)=(0±11±2)%, where the first uncertainty is statistical and the second systematic. The asymmetries are also measured as a function of the dimuon invariant mass. The results are consistent with the standard model predictions.
A
bstract
Production of prompt
D
0
mesons is studied in proton-lead and lead-proton collisions recorded at the LHCb detector at the LHC. The data sample corresponds to an integrated luminosity of 1
.
...58±0
.
02 nb
−1
recorded at a nucleon-nucleon centre-of-mass energy of
s
N
N
=
5
TeV. Measurements of the differential cross-section, the forward-backward production ratio and the nuclear modification factor are reported using
D
0
candidates with transverse momenta less than 10 GeV/c and rapidities in the ranges 1
.
5
< y
∗
<
4
.
0 and −5
.
0
< y
∗
<
−2
.
5 in the nucleon-nucleon centre-of-mass system.
A study of Bc+→K+K−π+ decays is performed for the first time using data corresponding to an integrated luminosity of 3.0 fb−1 collected by the LHCb experiment in pp collisions at center-of-mass ...energies of 7 and 8 TeV. Evidence for the decay Bc+→χc0(→K+K−)π+ is reported with a significance of 4.0 standard deviations, giving σ(Bc+)σ(B+)×B(Bc+→χc0π+)=(9.8−3.0+3.4(stat)±0.8(syst))×10−6. Here B denotes a branching fraction while σ(Bc+) and σ(B+) are the production cross sections for Bc+ and B+ mesons. An indication of b¯c weak annihilation is found for the region m(K−π+)<1.834 GeV/c2, with a significance of 2.4 standard deviations.
The time-integrated untagged Dalitz plot of the three-body hadronic charmless decay ¯ B 0 → K 0 S π + π − is studied using a p p collision data sample recorded with the LHCb detector, corresponding ...to an integrated luminosity of 3.0 fb − 1 . The decay amplitude is described with an isobar model. Relative contributions of the isobar amplitudes to the ¯ B 0 → K 0 S π + π − decay branching fraction and C P asymmetries of the flavor-specific amplitudes are measured. The C P asymmetry between the conjugate ¯ B 0 → K ∗ ( 892 ) − π + and B 0 → K ∗ ( 892 ) + π − decay rates is determined to be − 0.308 ± 0.062.
A
bstract
The forward-backward charge asymmetry for the process
q
q
¯
→
Z
/
γ
∗
→
μ
+
μ
−
is measured as a function of the invariant mass of the dimuon system. Measurements are performed using proton ...proton collision data collected with the LHCb detector at
s
=
7
and 8 TeV, corresponding to integrated luminosities of 1 fb
−1
and 2 fb
−1
respectively. Within the Standard Model the results constrain the effective electroweak mixing angle to be
sin
2
θ
W
eff
=
0.23142
±
0.00073
±
0.00052
±
0.00056
,
where the first uncertainty is statistical, the second systematic and the third theoretical. This result is in agreement with the current world average, and is one of the most precise determinations at hadron colliders to date.
The decays χc 1→J /ψ μ+μ- and χc 2→J /ψ μ+μ- are observed and used to study the resonance parameters of the χc 1 and χc 2 mesons. The masses of these states are measured to be m (χc 1)=3510.71 ±0.04 ...(stat ) ±0.09 (syst ) MeV and m (χc 2)=3556.10 ±0.06 (stat ) ±0.11 (syst ) MeV , where the knowledge of the momentum scale for charged particles dominates the systematic uncertainty. The momentum-scale uncertainties largely cancel in the mass difference m (χc 2)-m (χc 1)=45.39 ±0.07 (stat ) ±0.03 (syst ) MeV . The natural width of the χc 2 meson is measured to be Γ (χc 2)=2.10 ±0.20 (stat ) ±0.02 (syst ) MeV . These results are in good agreement with and have comparable precision to the current world averages.