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 Subsequent measurements resulted in the confusing experimental situation summarized in Table I In an unpublished update to their analysis [26], the CDF Collaboration presented 3.1σ evidence for a second relatively narrow J=ψϕ mass peak near 4274 MeV.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.

An angular analysis of the B 0 → K Ã0 ð→ K þ π − Þμ þ μ − decay is presented using a dataset corresponding to an integrated luminosity of 4.7 fb −1 of pp collision data collected with the LHCb experiment. The full set of CP-averaged observables are determined in bins of the invariant mass squared of the dimuon system. Contamination from decays with the K þ π − system in an S-wave configuration is taken into account. The tension seen between the previous LHCb results and the standard model predictions persists with the new data. The precise value of the significance of this tension depends on the choice of theory nuisance parameters.

Direct and mixing-induced CP -violating asymmetries in B 0 s → K + K − decays are measured for the first time using a data sample of pp collisions, corresponding to an integrated luminosity of 1.0 fb −1 , collected with the LHCb detector at a centre-of-mass energy of 7 TeV. The results are C KK = 0.14 ± 0.11 ± 0.03 and S KK = 0.30 ± 0.12 ± 0.04, where the first uncertainties are statistical and the second systematic. The corresponding quantities are also determined for B 0 → π + π − decays to be C ππ = −0.38 ± 0.15 ± 0.02 and S ππ = −0.71 ± 0.13 ± 0.02, in good agreement with existing measurements.

The Λ þ c K − mass spectrum is studied with a data sample of pp collisions at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 5.6 fb −1 collected by the LHCb experiment. Three Ξ 0 c states are observed with a large significance and their masses and natural widths are measured to be m½Ξ c ð2923Þ 0 ¼ 2923.04 AE 0.25 AE 0.20 AE 0.14 MeV, Γ½Ξ c ð2923Þ 0 ¼ 7.1 AE 0.8 AE 1.8 MeV, m½Ξ c ð2939Þ 0 ¼ 2938.55 AE 0.21 AE 0.17 AE 0.14 MeV, Γ½Ξ c ð2939Þ 0 ¼ 10.2 AE 0.8 AE 1.1 MeV, m½Ξ c ð2965Þ 0 ¼ 2964.88 AE 0.26 AE 0.14 AE 0.14 MeV, Γ½Ξ c ð2965Þ 0 ¼ 14.1 AE 0.9 AE 1.3 MeV, where the uncertainties are statistical, systematic, and due to the limited knowledge of the Λ þ c mass. The Ξ c ð2923Þ 0 and Ξ c ð2939Þ 0 baryons are new states. The Ξ c ð2965Þ 0 state is in the vicinity of the known Ξ c ð2970Þ 0 baryon; however, their masses and natural widths differ significantly.