Observation of a narrow charm-strange meson D(+)(sJ)(2632)-->D(+)(s)eta and D(0)K(+)

An updated review of the new hadron states

The past decades witnessed the golden era of hadron physics. Many excited open heavy flavor mesons and baryons have been observed since 2017. We shall provide an updated review of the recent experimental and theoretical progresses in this active field. Besides the conventional heavy hadrons, we shall also review the recently observed open heavy flavor tetraquark statesX(2900) andTcc+(3875)as well as the hidden heavy flavor multiquark statesX(6900),Pcs(4459)0,Zcs(3985)-,Zcs(4000)+, andZcs(4220)+. We will also cover the recent progresses on the glueballs and light hybrid mesons, which are the direct manifestations of the non-AbelianSU(3) gauge interaction of the Quantum Chromodynamics in the low-energy region.

A review of the open charm and open bottom systems

Since the discovery of the first charmed meson in 1976, many open-charm and open-bottom hadrons were observed. In 2003 two narrow charm-strange states [Formula: see text] and D _s1(2460) were discovered by the BaBar and CLEO Collaborations, respectively. After that, more excited heavy hadrons were reported. In this work, we review the experimental and theoretical progress in this field.

Decoding the X(5568) as a Fully Open-Flavor sub[over ¯]d[over ¯] Tetraquark State

We investigate the recent evidence for a charged X(5568) meson as an exotic open-flavor tetraquark state sub[over ¯]d[over ¯] with J^{P}=0^{+}/1^{+} in the framework of QCD sum rules. We use the color antisymmetric [3[over ¯]_{c}]_{su}⊗[3_{c}]_{b[over ¯]d[over ¯]} tetraquark currents in both scalar and axial-vector channels to perform evaluations and numerical analyses. Our results imply that the X(5568) can be interpreted as both the scalar sub[over ¯]d[over ¯] tetraquark state and the axial-vector one, which are in good agreement with the experimental measurement. We also discuss the possible decay patterns of the X(5568) and suggest to search for its neutral partner in the radiative decay into B_{s}^{0}γ and B_{s}^{*}γ, which can be used to determine its spin-parity quantum numbers. Moreover, we predict its charmed partner state around 2.55 GeV with the quark content suc[over ¯]d[over ¯] and J^{P}=0^{+}/1^{+}.

Measurement of the semileptonic branching ratio of B_{s};{0} to an orbitally excited D_{s};{**} state: Br(B_{s};{0}-->D_{s1};{-}(2536)mu;{+}nuX)

In a data sample of approximately 1.3 fb;{-1} collected with the D0 detector between 2002 and 2006, the orbitally excited charm state D_{s1};{+/-}(2536) has been observed with a measured mass of 2535.7+/-0.6(stat)+/-0.5(syst) MeV/c;{2} via the decay mode B_{s};{0}-->D_{s1};{-}(2536)mu;{+}nu_{mu}X. A first measurement is made of the branching ratio product Br(b[over ]-->D_{s1};{-}(2536)mu;{+}nu_{mu}X)xBr(D_{s1};{-}-->D;{*-}K_{S};{0}). Assuming that D_{s1};{-}(2536) production in semileptonic decay is entirely from B_{s};{0}, an extraction of the semileptonic branching ratio Br(B_{s};{0}-->D_{s1};{-}(2536)mu;{+}nu_{mu}X) is made.

D(s0)+ (2317)-D0(2308) mass difference as evidence for tetraquarks

We argue that the anomalously small mass difference between the D(s0)+ (2317) and the recently observed D0(2308) (Belle) state is the first "smoking gun" experimental evidence of their tetraquark [cq(q q)] structure. The recently reported D(sJ)+ (2632) (SELEX) state completes the low-lying nonexotic tetraquark spectrum, as predicted by 't Hooft's instanton-induced effective quark interaction.