1. The meson landscape Scalars and Glue in Strong QCD New states beyond Weird baryons: pentaquark problems “Diquarks,Tetraquarks, Pentaquarks and no quarks” Some reflections on Pentaquarks Correlated Colour in Strong QCD Implications for Exotic Mesons? Frank Close IPPP 041027 “Diquarks,Tetraquarks, Pentaquarks and no quarks”

2. Colour Correlations in Chromostatics

3. + + + baryon Chromostatics: Like electrostatics – unlike colours attract + - meson

4. ++ Attraction of two quarks to make a “diquark” If this acts as a quasi-particle……… “Scalar Diquarks” Pauli maximal attraction when net spin=0 and different flavours

5. ++ - - Diquark antidiquark mutually attract ……… ……Making a meson from diquarks = 2 quarks and 2 antiquarks

6. + + -- Fall apart into qq* pairs: Broad width Flavour pattern in nonet differs from qq* Consistent with light scalar mesons Jaffe; Close Tornqvist; Maiani et al

7. + + ++ + + Three diquarks……..

8. + + ++ + + rearrange to make… e.g. a deuteron (lower energy state… … presumably)… …..not obvious in JW model with light [ud]

9. + + ++ - Lets try another way: replace the BLUE YELLOW Diquark by a RED anti quark YELLOW

10. + + ++ -

11. + + ++ - d d uus* n eutron K The forces rearrange them to make e.g. a neutron and a kaon… “fall apart” = broad Or so we thought!!! 2002 discovered a (narrow) pentaquark! maybe

12. + + ++ - d u s* If the data survive; and if this is a pentaquark…. the correlations seem to maintain their identities 100 times more stable than anticipated (expt) = two ideas on how this happens (theory) Jaffe Wilzcek Karliner Lipkin

13. (qq)q(qq) description (Jaffe, Wilczek) J P = ½ + L=0 (ud) s L=1 Colour correlated models of the  + Pentaquark (qqq)(qq) description (Karliner, Lipkin) J P = ½ + L=1 (uds) (ud) distance > color magnetic force

14. u d u du d Q* u d Jaffe Wilczek udud udQ* Karliner Lipkin L=1 Diquark attractions for unlike flavours = basis for pentaquark models ( not demonstrated how low mass scalar diquarks form, stability, effective bosons, consistency with other hadron spectroscopy… etc. = ?) Narrow Pentaquarks (if they exist) = strong QCD correlations

15. Some reflections on Pentaquarks 10

16. Inconsistencies (I) Width of Θ + (1540) –Two “positive” experiments: HERMES: Γ Θ = 17  9  2 MeV ZEUS: Γ Θ = 8  4 MeV –K + N PWA results indicates Γ Θ < 1 MeV Mass of Θ + (1540)

17. (LEPS) Anomalies with Theta Mass? F. Close and Q. Zhao, hep-ph/0404075

18. Arndt Buccella Carlson Dyakanov Ellis Faber Giannini Huang Inoue Jaffe Karliner Lipkin Maltman Nussinov Oh Polyakov Qiang Rosner Stech Trilling U Veneziano Wilczek Xiang Yang Zhu If Theta doesn’t exist, then these (and many other theorists) should be congratulated on their creativity

19. Mass 15

20. Mass Fitted historically. Not calculated Dyakanov Petrov Polyakov DPP assumed N(1710) in 10bar Jaffe Wilzcek JW assumed N(1440) as (ud)(ud)dbar X mass formula bizarre: q_5 10bar mass gap 1/3 m_s X pure 10bar not photoproduced from p X width 300MeV X gamma n:gamma p = radial 56plet qqq X Delta(1670) partner Karliner Lipkin KL assume cs* 200MeV orbital to set scale X spin averaged cs* costs 500MeV, Theta= 1800MeV

21. Mass (L=1) = 200MeV Karliner Lipkin 2.59 2.56 2.32 2.11 1.97 1- 0+ Ds(cs*) spectrum 210 Ask Harry: is this cs* or DK molecule?

22. Mass 400-480 1- 0+ 0- 1+ L=0 L=1 2+ 2.55 - 2.47 2.07 Spin averaged masses in multiplet Theta = 1750-1830

23. u d u du d Q* u d Jaffe Wilczek udud udQ* Karliner Lipkin L=1 3/2 1/2 <100MeV FC+ Dudek 10bar 3/2+ unique to qqqqq* Spin-Orbit splitting

24. Mass Fitted more recently or excused Weise…Wilczek…Close…Maiani…(Kochelev,Vento) m[ud] ~ m(d) ~ 300MeV e.g. L=2: N(1680: [ud] u) = rho_3(1700: d*u) e.g. L=1: Lambda(1405: [ud] s) = K_2(1430: ds* ) 0+ mesons \sigma 600MeV; k 800MeV; f0/a0 980MeV X doesn’t explain Lambda Theta ~ 1100 + orbital; Why (does?) [ud] get protected ….at high L … in S-wave mesons But not in S-wave baryons?

25. udud udQ* uds* compact stabilised by instanton forces. aids narrow width (assertion) (ud)6,1 and (ud)3,0 mix lowers mass Hogaasen Sorba; Kochelev Vento…….. ud*Q ud* leaks into pions = broad er width Theta only narrow 10* Mass “calculated”: Instanton attractions: [ud]~450; (uds*) ~ 750 450 L=1 400 750 Effective mixes [ud]-s* and (uds*) Theta (1600)

26. Width 20

27. Chiral Soliton Theta-N-K Coupling involves three unknowns A; B; C B F/D Set scale with g(10*) = 1-B-C NRCQM: F/D=2/3 B=1/5 no ss* in N: C= 4/5 g(10*)=0 g(10 *) C After Ellis Karliner Prasalowicz Width

28. < 10 MeV experiments <1MeV Cahn Trilling; Nussinov;… Decouples from KN (small width) Strong coupling to something (strong production)  How is Theta produced? ………………enigma

29. Production 25

30. Inconsistencies (II) Production rate (e.g. for Θ + (1540) ) –“Positive” experiments: SAPHIR: R Λ*(1520) ~ 0.3 HERMES: R Λ*(1520) ~ 1.6~3.5 ZEUS: R Λ*(1520) ~ 0.2 ( I estimated from R Λ ~ 0.04 ) SVD-2: R Λ*(1520) > 0.2 ( estimated by SPHINX, hep-ex/0407026) –“Negative” experiments: ALEPH: R Λ*(1520) < 0.1 BaBar: R Λ*(1520) < ~ 0.01 Belle: <0.02 HERA-B: R Λ*(1520) < 0.027~0.16 SPHINX: R Λ*(1520) < 0.02

31. Several experimental limits in hadron production Some not restrictive yet e.g. psi(3095) to Theta Thetabar (=3080) versus LambdaLambdabar (1/100) or can be “explained away” e.g. hard to make 10 q + q* My opinion (this week) Limits in high statistics look impressive. Onus is on supporters to explain them away or find a loophole ……….example of a possible loophole Lipkin Karliner next

32. Why seen in photons but not in high statistics hadrons? CLAS: Theta+K = N*(2.4GeV) (24ev/10bgnd) Suppose N*(uddss*) and gamma provides the ss* Problems CLAS see in gamma pi K Theta pi N N* No memory of gamma(ss*); should apply to hadrons too…..why not CDF? SPring8 and CLAS1 too low E(gamma) to make 2.4GeV N*

33. The Mystery of the Sigma_5 The case of the dog that didn’t bark (Sherlock Holmes) If Theta is real, why isnt Sigma_5 (or Sigma* ½+ 1660) also seen?

34. Note pK s can be  + or  + Decays Dyakanov Petrov Polyakov; Close Dudek; Oh Kim Lee 30

35. Gamma N \to K Theta Assuming s,t,u and contact diagrams

36. Gamma N \to K Sigma5 FC-Q Zhao

37. Sigma5:Theta photoproduction ratio insensitive to ENERGY….. 0.5 …and to the Sigma Pentaquark mixing. Sigma:Theta > 0.4 Could be 0.6 Why not seen in pKs? FC+Q Zhao

38. M(pK s ) HERMES Absence of Sigma_5, or even Sigma(1660) in experiments that claim Theta is a worry. (unless Theta (uds*) exists and Sigma (ud*s) doesn’t Vento ) Or Theta and Sigma_5 degenerate = extra width FC Dudek unpublished on grounds of taste

39. Dzierba Szczepaniak Teige Fake Peaks in gamma N N gamma N a2/rho3 35

40. Dzierba Szczepaniak Teige Fake Peaks in gamma N N a2/rho3 N K K- + D/F wave decay forward back to KKbar a2/rho3 gives charge asymmetry Narrow K+n Broad K-n Same velocity NK mass 1440 “real” kinematics broadens hump….

41. Dzierba Szczepaniak Teige One is real (CLAS) Three are fake Can you tell which?

42. (LEPS) Could this also explain different nK+ and pKs masses? F. Close and Q. Zhao, hep-ph/0404075 Show Dalitz plots!! Different Q values for charged neutral feed into mass of fake Theta?

43. Exotic Mesons inspired by pentaquark correlations 39

44. - - L=1……making exotic 1-+ mesons……et al + + - - + + + - - + +/- Burns Close Dudek based on KL L L L

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

46. Three overheads on 1-+ pi_1(1400) and pi_1(1600) as correlated q*(qqq*) \pm q(q*q*q) Burns Close Dudek

47. Paradoxes; Enigmas; Hints of unreality How is Theta produced? Why seen in low statistics photoproduction but not in high statistics hadroproduction? Decouples from KN (small width) Strong coupling to something (strong production) Why does mass vary? real (dynamic clue); statistics (non existence clue) Cascades (exotics) studied since BQM Beware! K-Theta+ why no K+Sigma- Ks Theta+ why no Ks Sigma+ Why is production Theta/Sigma(1660) = infinity?

48. CONCLUSION Have Weird Multiquark Demons been found? Is there a 1 MeV wide, S=+1 baryon at 1540 MeV? If NO this is testament to the ingenuity of theorists whose models can explain it even if it doesn’t exist. Lattice QCD is almost unique in not having definitively disproved that such a state does not exist.

49. CONCLUSION YES No Keep searching Have Weird Multiquark Demons been found? Democratic voting paper/Florida counting principle

50. This slide sponsored by Oxford University Press A Very Short Introduction to Particle Physics A little red pocket book with no equations for physics undergraduates and your partners by Frank Close 10 dollars at amazon.com now

51.  D K - pK + n 3-body Dalitz plot

52. 10bar and hidden octet: threats and opportunities Also exotic Xi^o Xi^- Because I=3/2 Multiplet ! Exotic corners Theta+ Xi+ Xi - - With non- exotic Octet as well

53. udud udQ* (ud) S=1;col=6 attractive Karliner Lipkin (ud) S=0;col=3* attractive; mix; lowers energy Hogaasen Sorba Quasi Two Body Hadrons e.g. Karliner Lipkin Overlap with color 1 uQ* or dQ* = instability Hogaasen Sorba

54. u d u du d Q* u d Jaffe Wilczek udud udQ* Karliner Lipkin Q* \to (ud) = anomalous deuteron (ud) \to Q* 10bar mesons P-wave 1-+ etc? e.g. Chung Klempt Widths? FC Burns Forces ud very light and L large What mechanism? What if……..? 38

55. ++ - - Scalar diquarks……making Scalar mesons meson Jaffe 77; Maiani et al 04

56. Width < 10 MeV direct experiments <1MeV Cahn Trilling; Nussinov;… 3/2- Lambda(1520) KN width 7 MeV Jaffe Wilzcek; Jennings Maltman; Carlson et al; Close Dudek;Buccella Stora Color flavor spin overlap suppression > 24 X D wave; P-wave Lambda1600 is 100 MeV X needs qq* creation whereas qqqqq* falls apart X color killed by soft gluon exchange X spin flip costs little X flavor killed by rearrangement

57. CLAS -  + (1540) and N* ?   proton  ++ N* K+K+ n K-K-