Dibaryons with heavy quarks Hongxia Huang & Jialun Ping Nanjing Normal University Fan Wang Nanjing University Strangeness Nuclear Physics December 12nd – 14th, 2014, ChangSha, China
Outline Introduction Quark models and calculation methods Possible H-like dibaryon states: cc and bb Nc and Nb systems Summary
Dibaryons: H, d*, di-Ω, NΩ, …… Introduction exotic states Dibaryons: H, d*, di-Ω, NΩ, …… Pentaquarks: Θ+ , Ξ-- , …… Charmonium-like states: X(3872), Y(3940), Z(3900), Z(4430),…… Plausible molecular baryons: cD, cD, DN, DsN, …… Dibaryons with heavy quarks: cc, cc, c c, Nc, Nc, Ncc, NΩc, ……
Phenomenological models of two approaches: On the hadron level: Theoretical methods Lattice QCD QCD sum rule Phenomenological models of two approaches: On the hadron level: One-boson-exchange (OBE) model, One-pion-exchange (OPE) model ...... On the quark level: Isgur quark model , Chiral quark model, Quark delocalization color screening model
Is the H dibaryon a bound state? First proposed by R. L. Jaffe PRL 38, 195, 1977 Revived by Lattice QCD calculations of different collaborations: NPLQCD, PRL 106, 162001, 2011 HALQCD, PRL 106, 162002, 2011 Reexamined in a chiral constituent quark model PRC 85, 045202, 2012 Is the H-like dibaryon cc a bound state? Answers of two hadron level models No in One-boson-exchange model PRD 84, 014031, 2011 Yes in One-pion-exchange model PLB 704, 547, 2011 What about the quark level study of the cc system?
Quark Models and calculation method Quark delocalization color screening model (QDCSM) QDCSM was developed by Nanjing-Los Alamos collaboration in1990s aimed to multi-quark study. (PRL 69, 2901, 1992) Two new ingredients (based on quark cluster model configuration): quark delocalization (orbital excitation) color screening (color structure) Apply to baryon-baryon interaction and dibaryons NN, N , NΩ, … deuteron success！ d*
NΩ is a very narrow dibaryon resonance in D-wave scattering. PRC 83 (2011) 015202 HALQCD Collaboration, arXiv:1403.7284 RHIC-STAR Collaboration In QDCSM, d* is a dibaryon resonance in NN scattering. PRC 79 (2009) 024001 PRL 102 (2009) 052301 PRL 106 (2011) 242302 PRL 112 (2014) 202301 WASA-at-COSY Collaboration
CERN Courier http://cerncourier.com/cws/article/cern/
(1) Resonating group method (RGM) Calculation method (1) Resonating group method (RGM) In RGM, the multi-quark wave function is approximated by the cluster wave function, The internal motions of clusters are frozen and the relative motion wave function satisfies the following RGM equation
RGM equation where
(2) Kohn-Hulthen-Kato(KHK) variational method
Possible H-like dibaryon states: cc , b b PRC 89 ,035201,2014 The individual S-wave cc is unbound. A bound state is obtained for the cc system by channel-coupling.
The effects of tensor force are much smaller compared with that of the central force.
Compare with the hadron level calculation (PLB 704, 547,2011) Channel coupling (tensor force) is important.
Similar to H dibaryon: system (PRC 69, 065207,2004)
bb system
Nc and Nb systems PRC 87 ,034002,2013
The effective potentials S-wave channels: attractive D-wave channels: repulsive
Bound states The individual Nc is unbound. There is no any Nc bound state in the present channel-coupling calculation. The tensor force is not important as the one on the hadron level calculation. (PRD85,014015,2012)
Resonance states
Nb system
Summary 1. It is possible to form an H-like dibaryon state in the cc system. 2. There exists a Nc resonance state in the Nc D-wave scattering phase shifts. 3. The results of the bb and Nb systems are similar to those of the cc and Nc systems,respectively. 4. The role of the central force is much more important than the tensor force in our quark level calculation, while in the calculation on the hadron level, the tensor force is shown to be important. Further investigation should be done to understand the difference between these two approaches. It will help us to understand whether the quark-hadron is equivalent or not.
Thank you!