First Evidence for cos2ß>0 and Resolution of the Cabibbo-Kobayashi-Maskawa Quark-Mixing Unitarity Triangle Ambiguity.

We present first evidence that the cosine of the CP-violating weak phase 2ß is positive, and hence exclude trigonometric multifold solutions of the Cabibbo-Kobayashi-Maskawa (CKM) Unitarity Triangle using a time-dependent Dalitz plot analysis of B^{0}→D^{(*)}h^{0} with D→K_{S}^{0}π^{+}π^{-} decays, where h^{0}∈{π^{0},η,ω} denotes a light unflavored and neutral hadron. The measurement is performed combining the final data sets of the BABAR and Belle experiments collected at the ϒ(4S) resonance at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain (471±3)×10^{6}BB[over ¯] pairs recorded by the BABAR detector and (772±11)×10^{6}BB[over ¯] pairs recorded by the Belle detector. The results of the measurement are sin2ß=0.80±0.14(stat)±0.06(syst)±0.03(model) and cos2ß=0.91±0.22(stat)±0.09(syst)±0.07(model). The result for the direct measurement of the angle ß of the CKM Unitarity Triangle is ß=[22.5±4.4(stat)±1.2(syst)±0.6(model)]°. The measurement assumes no direct CP violation in B^{0}→D^{(*)}h^{0} decays. The quoted model uncertainties are due to the composition of the D^{0}→K_{S}^{0}π^{+}π^{-} decay amplitude model, which is newly established by performing a Dalitz plot amplitude analysis using a high-statistics e^{+}e^{-}→cc[over ¯] data sample. CP violation is observed in B^{0}→D^{(*)}h^{0} decays at the level of 5.1 standard deviations. The significance for cos2ß>0 is 3.7 standard deviations. The trigonometric multifold solution π/2-ß=(68.1±0.7)° is excluded at the level of 7.3 standard deviations. The measurement resolves an ambiguity in the determination of the apex of the CKM Unitarity Triangle.

First Observation of CP Violation in B[over ¯]

We report a measurement of the time-dependent CP asymmetry of B[over ¯]^{0}→D_{CP}^{(*)}h^{0} decays, where the light neutral hadron h^{0} is a π^{0}, η, or ω meson, and the neutral D meson is reconstructed in the CP eigenstates K^{+}K^{-}, K_{S}^{0}π^{0}, or K_{S}^{0}ω. The measurement is performed combining the final data samples collected at the ϒ(4S) resonance by the BABAR and Belle experiments at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain (471±3)×10^{6} BB[over ¯] pairs recorded by the BABAR detector and (772±11)×10^{6} BB[over ¯] pairs recorded by the Belle detector. We measure the CP asymmetry parameters -η_{f}S=+0.66±0.10(stat)±0.06(syst) and C=-0.02±0.07(stat)±0.03(syst). These results correspond to the first observation of CP violation in B[over ¯]^{0}→D_{CP}^{(*)}h^{0} decays. The hypothesis of no mixing-induced CP violation is excluded in these decays at the level of 5.4 standard deviations.

First observation of top quark production in the forward region.

Top quark production in the forward region in proton-proton collisions is observed for the first time. The W+b final state with W→µν is reconstructed using muons with a transverse momentum, p_{T}, larger than 25 GeV in the pseudorapidity range 2.0<η<4.5. The b jets are required to have 5020 GeV. The results are based on data corresponding to integrated luminosities of 1.0 and 2.0 fb^{-1} collected at center-of-mass energies of 7 and 8 TeV by LHCb. The inclusive top quark production cross sections in the fiducial region are σ(top)[7 TeV]=239±53(stat)±33(syst)±24(theory) fb,σ(top)[8 TeV]=289±43(stat)±40(syst)±29(theory) fb.These results, along with the observed differential yields and charge asymmetries, are in agreement with next-to-leading order standard model predictions.

Measurement of CP Violation in B0→J/ψK{S}

Measurements are presented of the CP violation observables S and C in the decays of B(0) and Bover ¯]0 mesons to the J/ψK(S)(0) final state. The data sample corresponds to an integrated luminosity of 3.0 fb(-1) collected with the LHCb experiment in proton-proton collisions at center-of-mass energies of 7 and 8 TeV, and contains a total of 41 560 selected B^{0} and B[over ¯]^{0} decays. The analysis of the time evolution of these decays yields S=0.731±0.035(stat)±0.020(syst) and C=-0.038±0.032(stat)±0.005(syst). In the standard model, S equals sin(2ß) to a good level of precision. The values are consistent with the current world averages and with the standard model expectations.

Measurement of Bc+ Production in Proton-Proton Collisions at √[s]=8 TeV.

Production of Bc+ mesons in proton-proton collisions at a center-of-mass energy of 8 TeV is studied with data corresponding to an integrated luminosity of 2.0 fb-1 recorded by the LHCb experiment. The ratio of production cross sections times branching fractions between the Bc+→J/ψπ+ and B+→J/ψK+ decays is measured as a function of transverse momentum and rapidity in the regions 0

Observation of two new Ξ(b)(-) baryon resonances.

Two structures are observed close to the kinematic threshold in the Ξ(b)(0)π(-) mass spectrum in a sample of proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb(-1), recorded by the LHCb experiment. In the quark model, two baryonic resonances with quark content bds are expected in this mass region: the spin-parity J(P)=(1/2)(+) and J(P)=(3/2)(+) states, denoted Ξ(b)('-) and Ξ(b)(*-). Interpreting the structures as these resonances, we measure the mass differences and the width of the heavier state to be m(Ξ(b)('-))-m(Ξ(b)(0))-m(π(-))=3.653±0.018±0.006 MeV/c(2), m(Ξ(b)(*-))-m(Ξ(b)(0))-m(π(-))=23.96±0.12±0.06 MeV/c(2), Γ(Ξ(b)(*-))=1.65±0.31±0.10 MeV, where the first and second uncertainties are statistical and systematic, respectively. The width of the lighter state is consistent with zero, and we place an upper limit of Γ(Ξ(b)('-))<0.08 MeV at 95% confidence level. Relative production rates of these states are also reported.

Measurement of the semileptonic CP asymmetry in B0-B[over ¯]0 mixing.

The semileptonic CP asymmetry in B0-B[over ¯]0 mixing, a(sl)(d), is measured in proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb-1, recorded by the LHCb experiment. Semileptonic B0 decays are reconstructed in the inclusive final states D-µ+ and D*-µ+, where the D- meson decays into the K+π-π- final state and the D*- meson into the D[over ¯]0(→K+π-)π- final state. The asymmetry between the numbers of D(*)-µ+ and D(*)+µ- decays is measured as a function of the decay time of the B0 mesons. The CP asymmetry is measured to be a(sl)(d)=(-0.02±0.19±0.30)%, where the first uncertainty is statistical and the second systematic. This is the most precise measurement of a(sl)(d) to date and is consistent with the prediction from the standard model.

Precision measurement of CP violation in B(S)(0)→J/ΨK+K- decays.

The time-dependent CP asymmetry in B(s)(0)→J/ψK+K- decays is measured using pp collision data, corresponding to an integrated luminosity of 3.0 fb-1, collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. In a sample of 96,000 B(s)(0)→J/ψK+K- decays, the CP-violating phase ϕs is measured, as well as the decay widths ΓL and ΓH of the light and heavy mass eigenstates of the B(s)(0)-B[over ¯]s0 system. The values obtained are ϕs=-0.058±0.049±0.006 rad, Γs≡(ΓL+ΓH)/2=0.6603±0.0027±0.0015 ps-1, and ΔΓs≡ΓL-ΓH=0.0805±0.0091±0.0032 ps-1, where the first uncertainty is statistical and the second, systematic. These are the most precise single measurements of those quantities to date. A combined analysis with Bs0→J/ψπ+π- decays gives ϕs=-0.010±0.039 rad. All measurements are in agreement with the standard model predictions. For the first time, the phase ϕs is measured independently for each polarization state of the K+K- system and shows no evidence for polarization dependence.

Test of lepton universality using b+ → K+ℓ+ℓ- decays.

A measurement of the ratio of the branching fractions of the B(+) → K(+)µ(+)µ(-) and B(+) → K(+)e(+)e(-) decays is presented using proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb(-1), recorded with the LHCb experiment at center-of-mass energies of 7 and 8 TeV. The value of the ratio of branching fractions for the dilepton invariant mass squared range 1 < q(2) < 6 GeV(2)/c(4) is measured to be 0.745(-0.074)(+0.090)(stat) ± 0.036(syst). This value is the most precise measurement of the ratio of branching fractions to date and is compatible with the standard model prediction within 2.6 standard deviations.

First observation of a baryonic Bc+ decay.

A baryonic decay of the B(c)(+) meson, B(c)(+) → J/ψppπ(+), is observed for the first time, with a significance of 7.3 standard deviations, in pp collision data collected with the LHCb detector and corresponding to an integrated luminosity of 3.0 fb(-1) taken at center-of-mass energies of 7 and 8 TeV. With the B(c)(+) → J/ψπ(+) decay as the normalization channel, the ratio of branching fractions is measured to be B(B(c)(+) → J/ψppπ(+))/B(B(c)(+) → J/ψπ(+)) = 0.143(-0.034)(+0.039)(stat) ± 0.013(syst). The mass of the B(c)(+) meson is determined as M(B(c)(+) = 6274.0 ± 1.8(stat) ± 0.4(syst) MeV/c(2), using the B(c)(+) → J/ψppπ(+) channel.

Observation of overlapping spin-1 and spin-3 D0K- resonances at mass 2.86 GeV/c2.

The resonant substructure of B(s)(0) → D(0)K(-)π(+) decays is studied using a data sample corresponding to an integrated luminosity of 3.0 fb(-1) of pp collision data recorded by the LHCb detector. An excess at m(D(0)K(-))≈ 2.86 GeV/c(2) is found to be an admixture of spin-1 and spin-3 resonances. Therefore, the D(sJ)*(2860)(-) state previously observed in inclusive e(+)e(-) → D(0)K(-)X and pp → D(0)K(-)X processes consists of at least two particles. This is the first observation of a heavy flavored spin-3 resonance, and the first time that any spin-3 particle has been seen to be produced in B decays. The masses and widths of the new states and of the D(s2)*(2573)(-) meson are measured, giving the most precise determinations to date.

Evidence for CP violation in B+ → ppK+ decays.

Three-body B+ → ppK+ and B(+) → ppπ(+) decays are studied using a data sample corresponding to an integrated luminosity of 3.0 fb(-1) collected by the LHCb experiment in proton-proton collisions at center-of-mass energies of 7 and 8 TeV. Evidence of CP violation in the B(+) → ppK(+) decay is found in regions of the phase space, representing the first measurement of this kind for a final state containing baryons. Measurements of the forward-backward asymmetry of the light meson in the pp rest frame yield A(FB)(ppK(+),m(pp)<2.85 GeV/c(2)) = 0.495 ± 0.012 (stat) ± 0.007 (syst) and A(FB)(ppπ(+),m(pp) <2.85 GeV/c(2)) = -0.409 ± 0.033 (stat) ± 0.006 (syst). In addition, the branching fraction of the decay B(+) → Λ(1520)p is measured to be B(B(+) → Λ(1520)p) = (3.15 ± 0.48 (stat) ± 0.07 (syst) ± 0.26 (BF)) × 10(-7), where BF denotes the uncertainty on secondary branching fractions.

Measurement of the B¯s° meson lifetime in Ds⁺π⁻ decays.

We present a measurement of the ratio of the B¯s° meson lifetime, in the flavor-specific decay to Ds⁺π⁻, to that of the B¯° meson. The pp collision data used correspond to an integrated luminosity of 1 fb(-1), collected with the LHCb detector, at a center-of-mass energy of 7 TeV. Combining our measured value of 1.010±0.010±0.008 for this ratio with the known B¯° lifetime, we determine the flavor-specific B¯s° lifetime to be τ(B¯s° )=1.535±0.015±0.014 ps, where the uncertainties are statistical and systematic, respectively. This is the most precise measurement to date, and is consistent with previous measurements and theoretical predictions.

Observation of B(s)(0) → J/ψ f1(1285) decays and measurement of the f1(1285) mixing angle.

Decays of B(s)(0) and B(0) mesons into J/ψ π+π-π+π- final states, produced in pp collisions at the LHC, are investigated using data corresponding to an integrated luminosity of 3 fb-1 collected with the LHCb detector. B(s)(0) → J/ψ f1(1285) decays are seen for the first time, and the branching fractions are measured. Using these rates, the f1(1285) mixing angle between strange and nonstrange components of its wave function in the qq structure model is determined to be ±(24.0-2.6-0.8+3.1+0.6)°. Implications on the possible tetraquark nature of the f1(1285) are discussed.

Measurements of indirect CP asymmetries in D0 → K- K+ and D0 → π- π+ decays.

A study of indirect CP violation in D0 mesons through the determination of the parameter AΓ is presented using a data sample of pp collisions, corresponding to an integrated luminosity of 1.0 fb(-1), collected with the LHCb detector and recorded at the center-of-mass energy of 7 TeV at the LHC. The parameter AΓ is the asymmetry of the effective lifetimes measured in decays of D0 and D0 mesons to the CP eigenstates K- K+ and π- π+. Fits to the data sample yield AΓ(KK)=(-0.35±0.62±0.12)×10(-3) and AΓ(ππ)=(0.33±1.06±0.14)×10(-3), where the first uncertainties are statistical and the second systematic. The results represent the world's best measurements of these quantities. They show no difference in AΓ between the two final states and no indication of CP violation.

First measurement of the charge asymmetry in beauty-quark pair production.

The difference in the angular distributions between beauty quarks and antiquarks, referred to as the charge asymmetry, is measured for the first time in bb pair production at a hadron collider. The data used correspond to an integrated luminosity of 1.0 fb(-1) collected at 7 TeV center-of-mass energy in proton-proton collisions with the LHCb detector. The measurement is performed in three regions of the invariant mass of the bb system. The results obtained are A(C)(bb))(40 105 GeV/c(2)) = 1.6 ± 1.7 ± 0.6%, where A(C)(bb)) is defined as the asymmetry in the difference in rapidity between jets formed from the beauty quark and antiquark, where in each case the first uncertainty is statistical and the second systematic. The beauty jets are required to satisfy 2 < η < 4, E(T) >20 GeV, and have an opening angle in the transverse plane Δ Ï• > 2.6 rad. These measurements are consistent with the predictions of the standard model.

Observation of the resonant character of the Z(4430)(-) state.

Resonant structures in B^{0}→ψ^{'}π^{-}K^{+} decays are analyzed by performing a four-dimensional fit of the decay amplitude, using pp collision data corresponding to 3 fb^{-1} collected with the LHCb detector. The data cannot be described with K^{+}π^{-} resonances alone, which is confirmed with a model-independent approach. A highly significant Z(4430)^{-}→ψ^{'}π^{-} component is required, thus confirming the existence of this state. The observed evolution of the Z(4430)^{-} amplitude with the ψ^{'}π^{-} mass establishes the resonant nature of this particle. The mass and width measurements are substantially improved. The spin parity is determined unambiguously to be 1^{+}.

Precision measurement of the mass and lifetime of the Ξ(b)(0) baryon.

Using a proton-proton collision data sample corresponding to an integrated luminosity of 3 fb(-1) collected by LHCb at center-of-mass energies of 7 and 8 TeV, about 3800 Ξ(b)(0) → Ξ(c)(+)π(-), Ξ(c)(+)) → pK(-)π(+) signal decays are reconstructed. From this sample, the first measurement of the Ξ(b)(0) baryon lifetime is made, relative to that of the Λ(b)(0) baryon. The mass differences M(Ξ(b)(0))-M(Λ(b)(0)) and M(Ξ(c)(+))-M(Λ(c)(+)) are also measured with precision more than 4 times better than the current world averages. The resulting values are τ(Ξ(b)(0))/τ(Λ)(b)(0)) = 1.006 ± 0.018 ± 0.010,M(Ξ(b)(0))-M(Λ(b)(0)) = 172.44 ± 0.39 ± 0.17 MeV/c(2),M(Ξ(c)(+))-M(Λ(c)(+)) = 181.51 ± 0.14 ± 0.10 MeV/c(2),where the first uncertainty is statistical and the second is systematic. The relative rate of Ξ(b)(0) to Λ(b)(0) baryon production is measured to be f(Ξ)(b)(0))/f(Λ)(b)(0))B(Ξ(b)(0) → Ξ(c)(+)π(-))/B(Λ(b)(0) → Λ(c)(+)π(-))B(Ξ(c)(+) → pK(-)π(+))/B(Λ(c)(+) → pK(-)}π(+)) = (1.88 ± 0.04 ± 0.03) × 10(-2),where the first factor is the ratio of fragmentation fractions, b → Ξ(b)(0) relative to b → Λ(b)(0). Relative production rates as functions of transverse momentum and pseudorapidity are also presented.

Precision measurement of the mass and lifetime of the Ξb⁻ baryon.

We report on measurements of the mass and lifetime of the Ξ(b)⁻ baryon using about 1800 Ξ(b)⁻ decays reconstructed in a proton-proton collision data set corresponding to an integrated luminosity of 3.0 fb⁻¹ collected by the LHCb experiment. The decays are reconstructed in the Ξ(b)⁻→Ξ(c)°π⁻, Ξ(c)°â†’pK⁻K⁻π⁺ channel and the mass and lifetime are measured using the Λ(b)°â†’Λ(c)⁺π⁻ mode as a reference. We measure M(Ξ(b)⁻)-M(Λ(b)°)=178.36±0.46±0.16 MeV/c², (τ(Ξ(b)⁻)/τ(Λ(b)°)=1.089±0.026±0.011, where the uncertainties are statistical and systematic, respectively. These results lead to a factor of 2 better precision on the Ξ(b)⁻ mass and lifetime compared to previous best measurements, and are consistent with theoretical expectations.

Search for Majorana neutrinos in B- → π+ µ- µ- decays.

A search for heavy Majorana neutrinos produced in the B- → π+ µ- µ- decay mode is performed using 3 fb(-1) of integrated luminosity collected with the LHCb detector in pp collisions at center-of-mass energies of 7 and 8 TeV at the LHC. Neutrinos with masses in the range 250 to 5000 MeV and lifetimes from zero to 1000 ps are probed. In the absence of a signal, upper limits are set on the branching fraction B(B- → π+ µ- µ-) as functions of neutrino mass and lifetime. These limits are on the order of 10(-9) for short neutrino lifetimes of 1 ps or less. Limits are also set on the coupling between the muon and a possible fourth-generation neutrino.