Measurements of CP observables in B±→DK± and B±→Dπ± decays are presented where the D meson is reconstructed in the final states K±π∓, π±K∓, K+K−, π+π−, K±π∓π+π−, π±K∓π+π− and π+π−π+π−. This analysis ...uses a sample of charged B mesons from pp collisions collected by the LHCb experiment in 2011 and 2012, corresponding to an integrated luminosity of 3.0 fb−1. Various CP-violating effects are reported and together these measurements provide important input for the determination of the unitarity triangle angle γ. The analysis of the four-pion D decay mode is the first of its kind.
Observation of Bc+ → D0K+ Decays Adinolfi, M.; Alessio, F.; Aslanides, E. ...
Physical review letters,
03/2017, Letnik:
118, Številka:
11
Journal Article
Recenzirano
Odprti dostop
Using proton-proton collision data corresponding to an integrated luminosity of 3.0 fb-1, recorded by the LHCb detector at center-of-mass energies of 7 and 8 TeV, the $B_c^+$ → $D^0K^+$ decay is ...observed with a statistical significance of 5.1 standard deviations. By normalizing to $B^+$ → $\bar{D}^0π^+$ decays, a measurement of the branching fraction multiplied by the production rates for $B_c^+$ relative to B+ mesons in the LHCb acceptance is obtained, $R_{D^0K}$ = ($f_c / f_u$) x $B$($B^+_c$ → $D^0K^+$) = ($9.3_{-2.5}^{+2.8}$ ± 0.6) × 10-7, where the first uncertainty is statistical and the second is systematic. This decay is expected to proceed predominantly through weak annihilation and penguin amplitudes, and is the first $B^+_c$ decay of this nature to be observed.
A
bstract
The CKM angle
γ
is determined from
CP
-violating observables measured in
B
±
→
D
K
∓
π
±
π
±
π
∓
h
±
, (
h
=
K, π
) decays, where the measurements are performed in bins of the decay ...phase-space of the
D
meson. Using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7
,
8 and 13 TeV, corresponding to a total integrated luminosity of 9 fb
−
1
,
γ
is determined to be
γ
=
54.8
+
6.0
−
5.8
+
0.6
−
0.6
+
6.7
−
4.3
∘
,
where the first uncertainty is statistical, the second systematic and the third from the external inputs on the coherence factors and strong phases of the
D
-meson decays.
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
Forward top quark pair production is studied in
pp
collisions in the
μeb
final state using a data sample corresponding to an integrated luminosity of 1.93 fb
−1
collected with the LHCb ...experiment at a centre-of-mass energy of 13 TeV. The cross-section is measured in a fiducial region where both leptons have a transverse momentum greater than 20 GeV and a pseudorapidity between 2.0 and 4.5. The quadrature sum of the azimuthal separation and the difference in pseudorapidities, denoted Δ
R
, between the two leptons must be larger than 0.1. The
b
-jet axis is required to be separated from both leptons by a Δ
R
of 0.5, and to have a transverse momentum in excess of 20 GeV and a pseudorapidity between 2.2 and 4.2. The cross-section is measured to be
σ
t
t
¯
=
126
±
19
stat
±
16
syst
±
5
lumi
f
b
where the first uncertainty is statistical, the second is systematic, and the third is due to the luminosity determination. The measurement is compatible with the Standard Model prediction.
The first observation of the decay ηc(2S)→pp¯ is reported using proton–proton collision data corresponding to an integrated luminosity of 3.0 fb−1 recorded by the LHCb experiment at centre-of-mass ...energies of 7 and 8 TeV. The ηc(2S) resonance is produced in the decay B+→cc¯K+. The product of branching fractions normalised to that for the J/ψ intermediate state, Rηc(2S), is measured to beRηc(2S)≡B(B+→ηc(2S)K+)×B(ηc(2S)→pp¯)B(B+→J/ψK+)×B(J/ψ→pp¯)=(1.58±0.33±0.09)×10−2, where the first uncertainty is statistical and the second systematic. No signals for the decays B+→X(3872)(→pp¯)K+ and B+→ψ(3770)(→pp¯)K+ are seen, and the 95% confidence level upper limits on their relative branching ratios are found to be RX(3872)<0.25×10−2 and Rψ(3770)<0.10. In addition, the mass differences between the ηc(1S) and the J/ψ states, between the ηc(2S) and the ψ(2S) states, and the natural width of the ηc(1S) are measured asMJ/ψ−Mηc(1S)=110.2±0.5±0.9 MeV,Mψ(2S)−Mηc(2S)=52.5±1.7±0.6 MeV,Γηc(1S)=34.0±1.9±1.3 MeV.
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.
We report a measurement of the lifetime of the Ω_{c}^{0} baryon using proton-proton collision data at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0 fb^{-1} ...collected by the LHCb experiment. The sample consists of about 1000 Ω_{b}^{-}→Ω_{c}^{0}μ^{-}νover ¯_{μ}X signal decays, where the Ω_{c}^{0} baryon is detected in the pK^{-}K^{-}π^{+} final state and X represents possible additional undetected particles in the decay. The Ω_{c}^{0} lifetime is measured to be τ_{Ω_{c}^{0}}=268±24±10±2 fs, where the uncertainties are statistical, systematic, and from the uncertainty in the D^{+} lifetime, respectively. This value is nearly four times larger than, and inconsistent with, the current world-average value.
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