387 research outputs found
Observation of an Excited Bc+ State
Using pp collision data corresponding to an integrated luminosity of 8.5 fb-1 recorded by the LHCb experiment at center-of-mass energies of s=7, 8, and 13 TeV, the observation of an excited Bc+ state in the Bc+π+π- invariant-mass spectrum is reported. The observed peak has a mass of 6841.2±0.6(stat)±0.1(syst)±0.8(Bc+) MeV/c2, where the last uncertainty is due to the limited knowledge of the Bc+ mass. It is consistent with expectations of the Bc∗(2S31)+ state reconstructed without the low-energy photon from the Bc∗(1S31)+→Bc+γ decay following Bc∗(2S31)+→Bc∗(1S31)+π+π-. A second state is seen with a global (local) statistical significance of 2.2σ (3.2σ) and a mass of 6872.1±1.3(stat)±0.1(syst)±0.8(Bc+) MeV/c2, and is consistent with the Bc(2S10)+ state. These mass measurements are the most precise to date
Updated Determination of D⁰–D¯⁰Mixing and CP Violation Parameters with D⁰→K⁺π⁻ Decays
We report measurements of charm-mixing parameters based on the decay-time-dependent ratio of D⁰→K⁺π⁻ to D⁰→K⁻π⁺ rates. The analysis uses a data sample of proton-proton collisions corresponding to an integrated luminosity of 5.0 fb⁻¹ recorded by the LHCb experiment from 2011 through 2016. Assuming charge-parity (CP) symmetry, the mixing parameters are determined to be x′²=(3.9±2.7)×10⁻⁵, y′=(5.28±0.52)×10⁻³, and R[subscript D]=(3.454±0.031)×10⁻³. Without this assumption, the measurement is performed separately for D⁰ and D[over ¯]⁰ mesons, yielding a direct CP-violating asymmetry A[subscript D]=(-0.1±9.1)×10⁻³, and magnitude of the ratio of mixing parameters 1.00<|q/p|<1.35 at the 68.3% confidence level. All results include statistical and systematic uncertainties and improve significantly upon previous single-measurement determinations. No evidence for CP violation in charm mixing is observed
Updated determination of D 0 - D 0 mixing and C P violation parameters with D 0 → K + π -
We report measurements of charm-mixing parameters based on the decay-time-dependent ratio of D0→K+π- to D0→K-π+ rates. The analysis uses a data sample of proton-proton collisions corresponding to an integrated luminosity of 5.0 fb-1 recorded by the LHCb experiment from 2011 through 2016. Assuming charge-parity (CP) symmetry, the mixing parameters are determined to be x′2=(3.9±2.7)×10-5, y′=(5.28±0.52)×10-3, and RD=(3.454±0.031)×10-3. Without this assumption, the measurement is performed separately for D0 and D0 mesons, yielding a direct CP-violating asymmetry AD=(-0.1±9.1)×10-3, and magnitude of the ratio of mixing parameters 1.00<|q/p|<1.35 at the 68.3% confidence level. All results include statistical and systematic uncertainties and improve significantly upon previous single-measurement determinations. No evidence for CP violation in charm mixing is observed
Measurement of the branching fraction and CP asymmetry in B plus . J/.. plus decays
The branching fraction and direct asymmetry of the decay
are measured using proton-proton collision
data collected with the LHCb detector at centre-of-mass energies of 7 and 8
TeV, corresponding to a total integrated luminosity of 3\mbox{fb}^{-1}. The
following results are obtained: \begin{align} \mathcal{B}(B^{+}\rightarrow
J/\psi \rho^{+}) &= (3.81 ^{+0.25}_{-0.24} \pm 0.35) \times 10^{-5}, \nonumber
\\ \mathcal{A}^{C\!P} (B^{+}\rightarrow J/\psi \rho^{+}) &=
-0.045^{+0.056}_{-0.057} \pm 0.008, \nonumber \end{align} where the first
uncertainties are statistical and the second systematic. Both measurements are
the most precise to date.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2018-036.htm
Search for violation through an amplitude analysis of decays
International audienceA search for CP violation in the Cabibbo-suppressed D → KKππ decay mode is performed using an amplitude analysis. The measurement uses a sample of pp collisions recorded by the LHCb experiment during 2011 and 2012, corresponding to an integrated luminosity of 3.0 fb. The D mesons are reconstructed from semileptonic b-hadron decays into DμX final states. The selected sample contains more than 160 000 signal decays, allowing the most precise amplitude modelling of this D decay to date. The obtained amplitude model is used to perform the search for CP violation. The result is compatible with CP symmetry, with a sensitivity ranging from 1% to 15% depending on the amplitude considered
Observation of CP Violation in Charm Decays
A search for charge-parity (CP) violation in D-0 -> K-K+ and D-0 -> pi(-)pi(+) decays is reported, using pp collision data corresponding to an integrated luminosity of 5.9 fb(-1) collected at a center-of-mass energy of 13 TeV with the LHCb detector. The flavor of the charm meson is inferred from the charge of the pion in D* (2010)(+) -> D-0 pi(+) decays or from the charge of the muon in (B) over bar -> D-0 mu(-)(nu) over bar X-mu decays. The difference between the CP asymmetries in D-0 -> K-K+ and D-0 -> pi(-)pi(+) decays is measured to be Delta A(CP) = [-18.2 +/- 3.2(stat) +/- 0.9(syst)] x 10(-4) for pi-tagged and Delta A(CP) = [-9 +/- 8(stat) +/- 5(syst)] x 10(-4) for mu-tagged D-0 mesons. Combining these with previous LHCb results leads to Delta A(CP) = (-15.4 +/- 2.9) x 10(-4), where the uncertainty includes both statistical and systematic contributions. The measured value differs from zero by more than 5 standard deviations. This is the first observation of CP violation in the decay of charm hadrons
Search for beautiful tetraquarks in the <i>ϒ</i>(1<i>S</i>)μ<sup>+</sup>μ<sup>−</sup> invariant-mass spectrum
International audienceThe ϒ(1S)μμ invariant-mass distribution is investigated for a possible exotic meson state composed of two b quarks and two quarks, . The analysis is based on a data sample of pp collisions recorded with the LHCb detector at centre-of-mass energies , 8 and 13 TeV, corresponding to an integrated luminosity of 6.3 fb. No significant excess is found, and upper limits are set on the product of the production cross-section and the branching fraction as functions of the mass of the state. The limits are set in the fiducial volume where all muons have pseudorapidity in the range [2.0, 5.0], and the state has rapidity in the range [2.0, 4.5] and transverse momentum less than 15 GeV/c
Measurement of CP -violating and mixing-induced observables in Bs0→ϕγ decays
A time-dependent analysis of the
B
0
s
→
ϕ
γ
decay rate is performed to determine the
C
P
-violating observables
S
ϕ
γ
and
C
ϕ
γ
and the mixing-induced observable
A
Δ
ϕ
γ
. The measurement is based on a sample of
p
p
collision data recorded with the LHCb detector, corresponding to an integrated luminosity of
3
fb
−
1
at center-of-mass energies of 7 and 8 TeV. The measured values are
S
ϕ
γ
=
0.43
±
0.30
±
0.11
,
C
ϕ
γ
=
0.11
±
0.29
±
0.11
, and
A
Δ
ϕ
γ
=
−
0.67
+
0.37
−
0.41
±
0.17
, where the first uncertainty is statistical and the second systematic. This is the first measurement of the observables
S
and
C
in radiative
B
0
s
decays. The results are consistent with the standard model predictions
Measurement of angular and CP asymmetries in D0→π+π-μ+μ- and D0→K+K-μ+μ- decays
The first measurements of the forward-backward asymmetry of the dimuon pair (A_{FB}), the triple-product asymmetry (A_{2ϕ}), and the charge-parity-conjugation asymmetry (A_{CP}), 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 A_{FB}(D^{0}→π^{+}π^{-}μ^{+}μ^{-})=(3.3±3.7±0.6)%, A_{2ϕ}(D^{0}→π^{+}π^{-}μ^{+}μ^{-})=(-0.6±3.7±0.6)%, A_{CP}(D^{0}→π^{+}π^{-}μ^{+}μ^{-})=(4.9±3.8±0.7)%, A_{FB}(D^{0}→K^{+}K^{-}μ^{+}μ^{-})=(0±11±2)%, A_{2ϕ}(D^{0}→K^{+}K^{-}μ^{+}μ^{-})=(9±11±1)%, A_{CP}(D^{0}→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
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