An angular analysis of the B 0 → K *0(→ K + π −)μ + μ − decay is presented. The dataset corresponds to an integrated luminosity of 3.0 fb−1 of pp collision data collected at the LHCb experiment. The complete angular information from the decay is used to determine CP-averaged observables and CP asymmetries, taking account of possible contamination from decays with the K + π − system in an S-wave configuration. The angular observables and their correlations are reported in bins of q 2, the invariant mass squared of the dimuon system. The observables are determined both from an unbinned maximum likelihood fit and by using the principal moments of the angular distribution. In addition, by fitting for q 2-dependent decay amplitudes in the region 1.1 < q 2 < 6.0 GeV2/c 4, the zero-crossing points of several angular observables are computed. A global fit is performed to the complete set of CP-averaged observables obtained from the maximum likelihood fit. This fit indicates differences with predictions based on the Standard Model at the level of 3.4 standard deviations. These differences could be explained by contributions from physics beyond the Standard Model, or by an unexpectedly large hadronic effect that is not accounted for in the Standard Model predictions

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^{+}.

The first full amplitude analysis of B þ → J=ψϕK þ with J=ψ → μ þ μ − , ϕ → K þ K − decays is performed with a data sample of 3 fb −1 of pp collision data collected at ffiffi ffi s p ¼ 7 and 8 TeV with the LHCb detector. The data cannot be described by a model that contains only excited kaon states decaying into ϕK þ , and four J=ψϕ structures are observed, each with significance over 5 standard deviations. The quantum numbers of these structures are determined with significance of at least 4 standard deviations. The lightest has mass consistent with, but width much larger than, previous measurements of the claimed Xð4140Þ state. DOI: 10.1103/PhysRevLett.118.022003 There has been a great deal of experimental and theoretical interest in J=ψϕ mass structures in B þ → J=ψϕK þ decays 1 since the CDF Collaboration presented 3.8σ evidence for a near-threshold Xð4140Þ mass peak, with width Γ¼11.7MeV [1].2 Much larger widths are expected for charmonium states at this mass because of open flavor decay channels [2], which should also make the kinematically suppressed X → J=ψϕ decays undetectable. Therefore, it has been suggested that the Xð4140Þ peak could be a molecular state [3][4][5][6][7][8][9], a tetraquark state [10][11][12][13][14], a hybrid state [15,16] or a rescattering effect [17,18]. Subsequent measurements resulted in the confusing experimental situation summarized in Table I In an unpublished update to their analysis [26], the CDF Collaboration presented 3.1σ evidence for a second relatively narrow J=ψϕ mass peak near 4274 MeV. A second peak was also observed by the CMS Collaboration at a mass which is higher by 3.2 standard deviations, but its statistical significance was not determined [23]. The Belle Collaboration obtained 3.2σ evidence for a narrow (Γ ¼ 13 þ18 −9 AE 4 MeV) J=ψϕ peak at 4350.6 þ4.6 −5.1 AE 0.7 MeV in two-photon collisions, which implies J PC ¼ 0 þþ or 2 þþ , and found no signal for Xð4140Þ [27].The Xð4140Þ and Xð4274Þ states are the only known candidates for four-quark systems that contain neither of the light u and d quarks. Their confirmation, and determination of their quantum numbers, would allow new insights into the binding mechanisms present in multiquark systems, and help improve understanding of QCD in the nonperturbative regime.The data sample used in this work corresponds to an integrated luminosity of 3 fb −1 collected with the LHCb detector in pp collisions at center-of-mass energies 7 and 8 TeV. The LHCb detector is a single-arm forward spectrometer covering the pseudorapidity range 2 < η < 5, described in detail in Refs. [28,29]. Thanks to the larger signal yield, corresponding to 4289 AE 151 reconstructed B þ → J=ψϕK þ decays, the roughly uniform efficiency and the relatively low background across the entire J=ψϕ mass range, this data sample offers the best sensitivity to date, not only to probe for the previously claimed J=ψϕ structures, but also to inspect the high mass region for the first time. All previous analyses were based on naive J=ψϕ mass (m J=ψϕ ) fits, with...

The first full amplitude analysis of B þ → J=ψϕK þ with J=ψ → μ þ μ − , ϕ → K þ K − decays is performed with a data sample of 3 fb −1 of pp collision data collected at ffiffi ffi s p ¼ 7 and 8 TeV with the LHCb detector. The data cannot be described by a model that contains only excited kaon states decaying into ϕK þ , and four J=ψϕ structures are observed, each with significance over 5 standard deviations. The quantum numbers of these structures are determined with significance of at least 4 standard deviations. The lightest has mass consistent with, but width much larger than, previous measurements of the claimed Xð4140Þ state. The model includes significant contributions from a number of expected kaon excitations, including the first observation of the K Ã ð1680Þ þ → ϕK þ transition.

The differential cross-section as a function of rapidity has been measured for the exclusive production of J/ψ and ψ(2S) mesons in proton–proton collisions at TeV, using data collected by the LHCb experiment, corresponding to an integrated luminosity of 930 pb−1. The cross-sections times branching fractions to two muons having pseudorapidities between 2.0 and 4.5 are measured to be where the first uncertainty is statistical and the second is systematic. The measurements agree with next-to-leading order QCD predictions as well as with models that include saturation effects.