How the X(5568) challenges our understanding of QCD

Abstract

We discuss the X(5568) particle recently announced by the D0 Collaboration. Several types of models were proposed to explain this structure in the literature. As pointed out by Burns and Swanson (arXiv:1603.04366), none of them provides a satisfactory description of the observation. We provide additional arguments using general properties of QCD, and conclude that the observation of the X(5568), if confirmed, poses serious challenges to our understanding of nonperturbative QCD.

5 pages. Typos removed, a wrong statement corrected, conclusions unchanged; the LHCb preliminary result mentioned at the end

References in corpus (6)

• Dynamically Generated Open and Hidden Charm Meson Systems
• Dynamically generated 0^+ heavy mesons in a heavy chiral unitary approach
• Strong and radiative decays of the Ds0*(2317) meson in the DK-molecule picture
• Radiative and isospin-violating decays of Ds mesons in the hadrogenesis conjecture
• Possible S-wave Bound-States of Two Pseudoscalar Mesons
• Strong and radiative decays of the $D_{s0}^{\ast }(2317)$ and $D_{s1}(2460)$

Cited by in corpus (45)

• Hadronic molecules
• The $XYZ$ states: experimental and theoretical status and perspectives
• Multiquark Resonances
• Non-Standard Heavy Mesons and Baryons, an Experimental Review
• A review of the open charm and open bottom systems
• Threshold cusps and triangle singularities in hadronic reactions
• Exotic Hadrons from Heavy Ion Collisions
• Heavy-flavored tetraquark states with the $QQ\bar{Q}\bar{Q}$ configuration
• Two-pole structure of the $D_0^{\ast }(2400)$
• Towards a theory of hadron resonances
• Open-charm tetraquark $X_c$ and open-bottom tetraquark $X_b$
• Triangle singularity as the origin of $X_0(2900)$ and $X_1(2900)$ observed in $B^{+}\to D^{+}{D}^{-}{K}^{+}$
• Open charm and bottom tetraquarks in an extended relativized quark model
• Search for the X(5568) state decaying into ${\mathrm{B}}_{\mathrm{s}}^0{\pi }^{\pm }$ in proton-proton collisions at $\sqrt{s}=$ 8 TeV
• Spectrum and rearrangement decays of tetraquark states with four different flavors
• Four-quark structure of Zc(3900), Z(4430) and Xb(5568) states
• Kinematical Cusp and Resonance Interpretations of the $X(2900)$
• Discriminating among interpretations for the $X(2900)$ states
• ${\Xi }_c$ and ${\Xi }_b$ excited states within a ${\mathrm{SU}(6)}_{\mathrm{lsf}}\times$HQSS model
• $P$-wave coupled-channel scattering of $B_s\pi ,B_s^{\ast }\pi ,B\overline{K},B^{\ast }\overline{K}$ and the puzzling $X(5568)$
• Open-flavor charmed/bottom $sq\bar{q}\bar{Q}$ and $qq\bar{q}\bar{Q}$ tetraquark states
• Triply heavy tetraquark states with the $QQ\bar{Q}\bar{q}$ configuration
• $B_s{\pi }^{+}$ scattering and search for X(5568) with lattice QCD
• Is the newly reported $X(5568)$ a $B\bar{K}$ molecular state?
• Application of the QCD light cone sum rule to tetraquarks: the strong vertices $X_b{X}_b\rho$ and $X_c{X}_c\rho$
• On the nature of the lowest-lying odd parity charmed baryon ${\Lambda }_c(2595)$ and ${\Lambda }_c(2625)$ resonances
• Where does the X(5568) structure come from?
• The decays of the fully open flavor state $T_{c\bar{s}0}^0$ in a $D^{\ast }{K}^{\ast }$ molecule scenario
• Generating a resonance-like structure in the reaction $B_c\to B_s\pi \pi$
• Triply heavy $QQ\bar{Q}\bar{q}$ tetraquark states
• Production of Charmed Tetraquarks from $B_c$ and $B$ decays
• Testing the doubly charged charm-strange tetraquarks
• Possibility of $T_{c\bar{s}}(2900)$ as the resonance-like structure induced by threshold effects
• searches for ud\bar{s}\bar{b} in the chiral quark model
• Lowest lying even-parity ${\bar{B}}_s$ mesons: heavy quark spin-flavor symmetry, chiral dynamics, and constituent quark model bare masses
• Weak Decays of Stable Open-bottom Tetraquark by SU(3) Symmetry Analysis
• Investigating tetraquarks composed of $us\bar{d}\bar{b}$ and $ud\bar{s}\bar{b}$
• Study of X(5568) in a unitary coupled-channel approximation of $B\bar{K}$ and $B_s\pi$
• Estimating decay rate of $X^{\pm }(5568)\to B_s{\pi }^{\pm }$ while assuming them to be molecular states
• The bottomed strange molecules with isospin 0
• How can $X^{\pm }(5568)$ escape detection?
• Mass Spectrum of Exotic X(5568) State via Artificial Neural Network
• The possible $B\pi$ molecular state and its radiative decay
• A coupled-channel perspective analysis on bottom-strange molecular pentaquarks
• X, Y and Z States