Four quark interpretation ofY(4260)

Abstract

We propose that the Y (4260) particle recently announced by BaBar is the first orbital excitation of a diquark-antidiquark state ([cs][cs]). Using parameters recently determined to describe the X(3872) and X(3940) we show that the Y mass is compatible with the orbital excitation picture. A crucial prediction is that Y (4260) should decay predominantly in DsDs. The Y (4260) should also be seen in B non-leptonic decays in association with one kaon. We consider the full nonet of related four-quark states and their predicted properties. Finally, we comment on a possible narrow resonance in the same channel.ROMA1 In a series of exciting experiments, BELLE and BaBar have discovered several states that, although decaying in charmonium plus pions, do not seem to fit the cc picture, in particular the X(3872) and X(3940) states.In a recent paper [1] we have pointed out that the properties of the new states can be well explained if they are S-wave diquark-antidiquark bound states with the composition (q = u, d): [(cq)(cq)] S−wave . An alternative scenario is the molecular picture where the X(3872) would be a D 0 D * 0 bound state. A crucial difference between the two alternatives is that colored objects in a rising confining potential, such as diquarks, should exhibit a series of orbital angular momentum excitations. This is clearly at variance with the molecular picture. Colorless objects bound by a short range potential should have a very limited spectrum, possibly restricted to S-wave states only.In this note we would like to propose that the first orbital excitation of a diquark-antidiquark state may have indeed been found in the state Y (4260) recently announced by the BaBar collaboration [2]. We discuss the properties of the new state in this framework and spell out a few distinctive predictions. The most revealing among them is that the dominant decay mode of Y (4260) should be in D sDs pairs. We shall also briefly discuss other states implied by the scheme and their properties. We comment on the possibility of an additional narrow state.The Y (4260) is observed by BaBar in e + e − annihilation, in association with an Initial-State-Radiation pho- * Electronic address: luciano.maiani@roma1.infn.it † Electronic address: veronica.riquer@cern.ch ‡ Electronic address: fulvio.piccinini@pv.infn.it § Electronic address: antonio.polosa@cern.ch ton, which implies J P C = 1 −− . The particle has a width of about 90 MeV and it is seen to decay in J/ψ π + π − . The π + π − mass distribution peaks around 1 GeV, consistently with a decay into J/ψ f 0 (980). BaBar reports the value [2]:(1) The diquark-antidiquark assumption together with the negative parity call for at least one unit of orbital angular momentum. In addition, the decay into f 0 (980), which fits the (

$$D^*_{s0}(2317)$$ D s 0 ∗ ( 2317 ) and $$\textit{DK}$$ DK scattering in B decays from BaBar and LHCb data

“…Because of its low mass, the structure of this meson has been extensively discussed. The suggested interpretations cover a wide range: cs state [11][12][13][14][15][16], two-meson molecular state [17][18][19][20][21][22][23][24][25][26][27], K -D mixing [28], four-quark states [29][30][31][32][33] or a mixture between two-meson and four-quark states [34].…”

Observation of a narrow mass state decaying intoΥ(1S)+γinpp¯collisions atAbazov1, Abbott2, Acharya3 et al. 2012Phys. Rev. D

“…One explanation for this state is a DD * molecule [2], but the subsequent discoveries of several other unexpected particles containing a cc pair have suggested otherwise. The Y (4260) [3] is most naturally explained as a hybrid ccgluon state [4], but it could also be a four-quark state [5]. The Z(4430) [6] is likely a four-quark charmonium-like particle by virtue of its non-zero electric charge, and the recently observed charged structures decaying into πΥ might be similar states containing b quarks [7].…”

Diquark and light four-quark states

“…Among the exotic hadrons, four-quark state scenarios are of both theoretical and experimental interest. A four-quark state was predicted to exist early in a consistent description of the hadron scattering amplitudes [1], and their properties have been studied in many models [2,3,4,5,6,7,8,9,10,11,12].…”