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تسجيل مستخدم جديدResonance $X(5568)$ as an exotic axial-vector state
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The mass and meson-current coupling constant of the resonance $X(5568)$, as well as the width of the decay $X(5568)to B_s^{ast}pi$ are calculated by modeling the exotic $X(5568)$ resonance as a diquark-antidiquark state $% X_b=[su][bd]$ with quantum numbers $J^{P}=1^{+}$. The calculations are made employing QCD two-point sum rule method, where the quark, gluon and mixed vacuum condensates up to dimension eight are taken into account. The sum rule approach on the light-cone in its soft-meson approximation is used to explore the vertex $X_bB_{s}^{ast}pi$ and extract the strong coupling $% g_{X_bB_{s}^{ast}pi}$, which is a necessary ingredient to find the width of the $X_b to B_s^{ast}pi^{+}$ decay process. The obtained predictions are compared with the experimental data of the D0 Collaboration, and results of other theoretical works.
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A search for the exotic meson $X(5568)$ decaying into the $B^0_s pi^{pm}$ final state is performed using data corresponding to $9.6 textrm{fb}^{-1}$ from $p{bar p}$ collisions at $sqrt{s} = 1960$ GeV recorded by the Collider Detector at Fermilab. No
evidence for this state is found and an upper limit of 6.7% at the 95% confidence level is set on the fraction of $B^0_s$ produced through the $X(5568) rightarrow B^0_s , pi^{pm}$ process.
Stimulated by the recent observation of the $X(5568)$, we study the $X(5568)$ and its partners under the tetraquark scenario. In the framework of the color-magnetic interaction, we estimate the masses of the partner states of the $X(5568)$ and discus
s their decay pattern, which provide valuable information on the future experimental search of these states.
Multi-quark states were predicted by Gell-Mann when the quark model was first formulated. Recently, numerous exotic states that are considered to be multi-quark states have been experimentally confirmed (four-quark mesons and five-quark baryons). The
oretical research indicates that the four-quark state might comprise molecular and/or tetraquark structures. We consider that the meson containing four different flavors $subar bbar d$ should exist and decay via the $X(5568)to B_spi$ channel. However, except for the D0 collaboration, all other experimental collaborations have reported negative observations for $X(5568)$ in this golden portal. This contradiction has stimulated the interest of both theorists and experimentalists. To address this discrepancy, we propose that the assumed $X(5568)$ is a mixture of a molecular state and tetraquark, which contributes destructively to $X(5568)to B_spi$. The cancellation may be accidental and it should be incomplete. In this scenario, there should be two physical states with the same flavor ingredients, with spectra of $5344pm307$ and $6318pm315$. $X(5568)$ lies in the error range of the first state. We predict the width of the second state (designated as $S_2$) as $Gamma(X_{S_2}to B_spi)=224pm97$ MeV. We strongly suggest searching for it in future experiments.
The semileptonic decays of the open charm-bottom axial-vector tetraquark $ Z_{s}=[cs][overline{b}overline{s}]$ to $X(4274)overline{l} u_l$, $l=e, mu, tau $ are explored by means of the QCD three-point sum rule method. Both $Z_{s}$ and $X(4274)=[cs][
overline{c}overline{s}]$ are treated as color sextet diquark-antidiquark states. The full width of the decays $Z_s to X(4274)overline{l} u_l$ is found. Obtained predictions for $ Gamma(Z_s to X(4274)overline{l} u_l)$ demonstrate that, as in the case of the conventional hadrons, the semileptonic transitions form a very small part of its full width.
We discuss the phenomenology of the axial-vector mesons within a three-flavour Linear Sigma Model containing scalar, pseudoscalar, vector and axial-vector degrees of freedom.
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