A New Hadron Spectroscopy

Abstract

Many candidate multiquark mesons, i.e., mesons with substructures that are more complex than the quark-antiquark prescription that is in the textbooks, have recently been observed. Many of the most recently observed candidate states are electrically charged and have the same spin and parity, namely J P = 1 + . In this talk I give an overview of the current experimental situation and identify patterns among the recently discovered J P = 1 + states, compare these patterns with expectations from proposed theoretical models, and the existence of additional, related states that might be accessible at current and future experiments. In addition, models that attribute the observed states to kinematically induced cusps are discussed.

Tritonlike Molecules of Three Identical Baryons

“…We should consider the distortion created by the ℧ c while calculating the BO potential between the ℧ a and ℧ b . After solving the three-body Schrödinger equation as Equation (21), we obtain the distorted wave functions Φð r (11). Therefore, we should use Φð r !…”

“…Numerous exotic states called "XYZ" reported in the last few decades pose great challenges to the traditional quark model [1][2][3][4][5][6][7][8][9][10][11]. Some of them sit in the vicinity of the open charm threshold can be viewed as good candidates of di-hadron molecules [12].…”

Spontaneous symmetry breaking in tensor theories

“…The idea is to introduce a symmetry breaking term (ǫ-term) in the path integral. The theory is invariant under G dd (N ), which is stated as L Φ ′ (x) = L Φ(x) , where Φ ′ and Φ are related by (4). In this letter we are not taking extra assumptions on the Lagrangian of the theory L Φ(x) , as long as its potential allows SSB.…”

“…As anticipated, we make use of the powerful ǫ-term technique, which we now outline, and can be found in detail in [31]. This technique takes advantage of the invariance of the functional integral (11) under the transformations (4). After performing (4), (11) reads as a function of g k = e iθ k a Ta and gk = e iθk a Ta of U k (N ) and Uk(N ), respectively.…”

XYZ studies at BESIII

“…The combination of the three lightest quarks with the respective antiquarks gives rise to the well-known octet of flavor-SU(3). Extending this mechanism [3] two quark triplets can be combined to form a "diquark" antitriplet of antisymmetric qq states. Each diquark has a color, so they must combine with other colored quark states thereby forming multiquark color-singlet states.…”