Model Predictions of a

1. Model Predictions of a Jo Dudek, Jefferson Lab

2. this is much lower than the naïve constituent quark model estimate: challenge for models to accommodate such a low mass not to mention the width i’ll consider some models that seem to be able to do it (to within 50 MeV) chiral solition model Karliner-Lipkin hyperfine model Kochelev, Lee & Vento “instantons” an alternative view of the Jaffe-Wilczek model Has any model explained 1540 MeV? experiments that do see a signal all do so near 1540 MeV Jo Dudek, Jefferson Lab

3. Has any model explained 1540 MeV? problem often seems to be that observations elsewhere in the hadron spectrum are not consistent within the models with a at 1540 MeV Jo Dudek, Jefferson Lab

4. set the mass scale of the assuming the experimental N(1710) is a member set using ‘experimental’ values N(1710) actually a mixture required to allow U-spin Chiral Soliton Model formulation due to Diakonov, Petrov and Polyakov predicted a baryon containing a at 1530 MeV ZPhys A359, 305 (1997) Jo Dudek, Jefferson Lab

5. effects include: increases the admixture into the too small compared to expt. changes the mass prediction; EKP estimate 1430 – 1660 MeV, describing the DPP prediction as ‘somewhat fortuitous’ recently other possibilities considered e.g. mixing in another , or a ; might solve phenom. problems but becomes rather model dependent chiral soliton model can accommodate, but does not definitively predict, a at 1540 MeV Chiral Soliton Model more recent study by Ellis, Karliner and Praszalowicz suggests that used by DPP not accurate; they use Jo Dudek, Jefferson Lab

6.  looks OK for baryons so proposed a diquark-triquark structure for the as lowest hyperfine energy P-wave inserted to keep clusters apart (prevents repulsive interactions) predict a mass of 1592 MeV Karliner & Lipkin used the venerable colour-spin hyperfine interaction assumed then Jo Dudek, Jefferson Lab

7. they express the diquark + triquark mass as having eliminated using in this model ; setting from the splitting gives model not complete for mesons lost around 100 MeV from the mass more serious problem is their estimation of the P-wave excitation energy they note that and use the splitting as an estimate of obtain while usual quark model estimate would be nearer to 400 MeV Karliner & Lipkin – 1592 MeV? Jo Dudek, Jefferson Lab

8. proposal that these states are S-wave meson-meson molecules e.g. Barnes, Close, Lipkin Phys.Rev.D68:054006,2003 the doubt over the nature of the should make us wary of using it as a simple L=1 excitation Karliner & Lipkin – P-wave KL Jo Dudek, Jefferson Lab

9. L=1 states split by spin-orbit forces in general potential model: colour-spin interaction splits should use spin-averaged mass Karliner & Lipkin – P-wave Let’s assume the is a conventional L=1 meson KL’s estimate of is still inconsistent KL Jo Dudek, Jefferson Lab

10. Kochelev, Lee & Vento also have a triquark-diquark model, with instanton motivated interactions. Use the splitting to estimate P-wave Karliner & Lipkin – P-wave consistent estimate 350-450 MeV KL 207 MeV Jo Dudek, Jefferson Lab

11. S=+2 meson = Kochelev, Lee & Vento suppresses decay width apply same logic to narrow, strangeness +2 meson near 1600 MeV Exotic Pentaquarks Exotic Mesons general problem with clustered quark models, for example triquark - diquark: Jo Dudek, Jefferson Lab

12. no KK decay actually several different spin-parity states - 1969! Exotic Pentaquarks Exotic Mesons narrow strangeness +2 meson near 1600 MeV Jo Dudek, Jefferson Lab

13. Wishful thinking - pentaquark in 1969 Jo Dudek, Jefferson Lab

14. flavour sym colour antisym spin sym space diquarks are identical bosons Jaffe & Wilczek degree-of-freedom SCALAR DIQUARK Jo Dudek, Jefferson Lab

15. Jaffe-Wilczek propose ideal mixing by Hamiltonian mass as an input, sets * Roper as input sets initially degenerate non-exotic states will mix Jo Dudek, Jefferson Lab

16. N(1440)/N(1710) as ? alternatively, consider N(1440)/N(1710) as input, then 1540 MeV ‘predicted’ for but do these assignments really work? consider decays of states in a ‘fall-apart’ model, i.e. assuming flavour structure of meson-baryon end state has trivial overlap with pentaquark Jo Dudek, Jefferson Lab

17. PLB 586 75 antisymmetric diquark contains symmetric “diquark” N(1710) PDG N(1440)/N(1710) as ? pentaquark assignment looks unlikely Jo Dudek, Jefferson Lab

18. Summary Including a as light as 1540 MeV and as narrow as 1 MeV has implications for the non-exotic hadron spectrum in both the baryon and meson sectors Jo Dudek, Jefferson Lab