We present a measurement of form-factor-independent angular observables in the decay B(0)→K*(892)(0)μ(+)μ(-). The analysis is based on a data sample corresponding to an integrated luminosity of 1.0 fb(-1), collected by the LHCb experiment in pp collisions at a center-of-mass energy of 7 TeV. Four observables are measured in six bins of the dimuon invariant mass squared q² in the range 0.1

The isospin asymmetries of B → Kµ + µ − and B → K * µ + µ − decays and the partial branching fractions of the B 0 → K 0 µ + µ − , B + → K + µ + µ − and B + → K * + µ + µ − decays are measured as functions of the dimuon mass squared, q 2 . The data used correspond to an integrated luminosity of 3 fb −1 from proton-proton collisions collected with the LHCb detector at centre-of-mass energies of 7 TeV and 8 TeV in 2011 and 2012, respectively. The isospin asymmetries are both consistent with the Standard Model expectations. The three measured branching fractions favour lower values than their respective theoretical predictions, however they are all individually consistent with the Standard Model.

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...

A search is presented for hidden-sector bosons, χ, produced in the decay B(0)→K*(892)(0)χ, with K*(892)(0)→K(+)π(-) and χ→μ(+)μ(-). The search is performed using pp-collision data corresponding to 3.0  fb(-1) collected with the LHCb detector. No significant signal is observed in the accessible mass range 214≤m(χ)≤4350  MeV, and upper limits are placed on the branching fraction product B(B(0)→K*(892)(0)χ)×B(χ→μ(+)μ(-)) as a function of the mass and lifetime of the χ boson. These limits are of the order of 10(-9) for χ lifetimes less than 100 ps over most of the m(χ) range, and place the most stringent constraints to date on many theories that predict the existence of additional low-mass bosons.