Abstract
Discovery of X(5568) brings up a tremendous interest because it is very special, i.e. made of four different flavors. The D0 collaboration claimed that they observed this resonance through portal X(5568)rightarrow B_spi , but unfortunately, later the LHCb, CMS, CDF and ATLAS collaborations’ reports indicate that no such state was found. Almost on the Eve of 2017, the D0 collaboration reconfirmed existence of X(5568) via the semileptonic decay of B_s. To further reveal the discrepancy, supposing X(5568) as a molecular state, we calculate the decay rate of X(5568)rightarrow B_spi ^+ in an extended light front model. Numerically, the theoretically predicted decay width of Gamma (X(5568)rightarrow B_spi ^+) is 20.28 MeV which is consistent with the result of the D0 collaboration (Gamma =18.6^{+7.9}_{-6.1}({textit{stat}})^{+3.5}_{-3.8}({textit{syst}}) MeV). Since the resonance is narrow, signals might be drowned in a messy background. In analog, two open-charm molecular states DK and BD named as X_a and X_b, could be in the same situation. The rates of X_arightarrow D_spi ^0 and X_brightarrow B_cpi ^0 are estimated as about 30 and 20 MeV respectively. We suggest the experimental collaborations round the world to search for these two modes and accurate measurements may provide us with valuable information.
Highlights
The observed exotic X, Y, Z states are composed of hidden charm or bottom flavors
Since for the strong interaction, flavor components do not change and the final state includes Bs whose quark-component is and π + made of ud, so in the final state there are four different flavors which cannot be created from vacuum, one can confirm that X (5568) is a four-quark state which consists of bsudingredients
In order to explore the decay rates of a molecular state, we extend the light front quark model (LFQM) which has been successfully applied for calculating decay rates of regular mesons and baryons [36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56]
Summary
The observed exotic X, Y, Z states are composed of hidden charm or bottom flavors. Even though the SU(2) symmetry between c and s quarks is not a good one, the deviation does not prevent us to make a rough estimate on the binding energy We will study their decays while they are supposed to be molecular states and the results can be a cross check for the mysterious X (5568). We further estimate decay rates of Xa → Dsπ 0 and Xb → Bcπ 0 in terms of the same method where Xa and Xb are the molecular states consisting of D K and B D constituents respectively. We calculate the decay rate of X (5568)+ → Bsπ +, while assuming X (5568) as a B Kmolecular state whose quantum number I (J P ) is 0(0+), in the light-front model.
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