The first observation of the D0→π+π-μ+μ- and D0→K+K-μ+μ- decays is reported using a sample of proton-proton collisions collected by LHCb at a center-of-mass energy of 8 TeV, and corresponding to 2 ...fb-1 of integrated luminosity. The corresponding branching fractions are measured using as normalization the decay D0→K-π+μ+μ-ρ0/ω, where the two muons are consistent with coming from the decay of a ρ0 or ω meson. The results are B (D0→π+π-μ+μ- )=(9.64 ±0.48 ±0.51 ±0.97 )×10-7 and B (D0→K+K-μ+μ- )=(1.54 ±0.27 ±0.09 ±0.16 )×10-7 , where the uncertainties are statistical, systematic, and due to the limited knowledge of the normalization branching fraction. The dependence of the branching fraction on the dimuon mass is also investigated.
Bottom baryons decaying to a J/ψ meson and a hyperon are reconstructed using 1.0 fb(-1) of data collected in 2011 with the LHCb detector. Significant Λ(b)(0) → J/ψΛ, Ξ(b((-) → J/ψΞ(-) and Ω(b)(-) → ...J/ψΩ(-) signals are observed and the corresponding masses are measured to be M(Λ(b)(0))=5619.53 ± 0.13(stat.) ± 0.45(syst.) MeV/c(2), M(Ξ(b)(-)) = 5795.8 ± 0.9(stat.) ± 0.4(syst.) MeV/c(2), M(Ω(b)(-)) = 6046.0 ± 2.2(stat.) ± 0.5(syst.) MeV/c(2) , while the differences with respect to the Λ(b)(0) mass are M(Ξ(b)(-))-M(Λ(b)(0))=176.2 ± 0.9(stat.) ± 0.1(syst.) MeV/c(2), M(Ω(b)(-))-M(Λ(b)(0))=426.4 ± 2.2(stat.) ± 0.4(syst.) MeV/c(2). These are the most precise mass measurements of the Λ(b)(0), Ξ(b)(-) and Ω(b)(-) baryons to date. Averaging the above Λ(b)(0) mass measurement with that published by LHCb using 35 pb(-1) of data collected in 2010 yields M(Λ(b)(0)) = 5619.44 ± 0.13(stat.)± 0.38(syst.) MeV/c(2).
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.
Observation of D0-D0 oscillations Abellan Beteta, C; Adametz, A; Alves, Jr, A A ...
Physical review letters,
2013-Mar-08, Letnik:
110, Številka:
10
Journal Article
Recenzirano
Odprti dostop
We report a measurement of the time-dependent ratio of D(0) → K(+) π- to D(0) → K(-) π(+) decay rates in D(*+)-tagged events using 1.0 fb(-1) of integrated luminosity recorded by the LHCb experiment. ...We measure the mixing parameters x('2) = (-0.9 ± 1.3) × 10(-4), y' = (7.2 ± 2.4) × 10(-3), and the ratio of doubly-Cabibbo-suppressed to Cabibbo-favored decay rates R(D) = (3.52 ± 0.15) × 10^{-3}, where the uncertainties include statistical and systematic sources. The result excludes the no-mixing hypothesis with a probability corresponding to 9.1 standard deviations and represents the first observation of D0-D0 oscillations from a single measurement.
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.
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.
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.
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.
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