Observation ofJ/ψϕStructures Consistent with Exotic States from Amplitude Analysis ofB+→J

Abstract

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 Subsequent measurements resulted in the confusing experimental situation summarized in Table I In an unpublished update to their analysis [26], the CDF Collaboration presented 3.1σ evidence for a second relatively narrow J=ψϕ mass peak near 4274 MeV.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

Rare decays and exotic states in quark flavour physics

“…Regarding tetraquark states, a recent analysis of the B → J/Ψφ K decay by LHCb established the existence of four states : the X(4140), already reported by CDF, D0 and CMS, the X(4274), previously seen by CDF and CMS, and two new states, the X(4500) and the X(4700) [28]. These four resonances are observed with significances larger than 5σ and can be clearly seen on Fig.…”

“…These four resonances are observed with significances larger than 5σ and can be clearly seen on Fig. 5 [28]. The last result presented here concerns hadron spectroscopy.…”

Multiquark resonances

“…Very recently, LHCb published the preliminary amplitude analysis of the full 6D Dalitz distributions [139,140]. The results are impressive: they not only confirm both the X(4140) and the second peak, although with much larger widths, but they also find other two heavier states.…”

“…On the left panel we use the X(4140) width as measured by CMS [138]. On the right we use the most recent LHCb value [139,140] -see Sections 6.4 and 8.6.…”

X(4140) , X(4270) , X<

“…Very recently, in the B + → J/ψφK + decay, the LHCb Collaboration confirmed the existence of the X(4140) and X(4274). Their quantum numbers are measured to be J P C = 1 ++ [10]. The mass of the X(4140), M = 4146.5±4.5…”