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Comments on the XYZ mesons

Comments on the XYZ mesons. Stephen L. Olsen, Univ of Hawai’i Charm 2006 June 5-8, Beijing. charmonium states. All sub-open-charm threshold states have been identified. All sub-open-charm threshold states have been identified. Properties are pretty well understood.

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Comments on the XYZ mesons

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  1. Comments on the XYZ mesons Stephen L. Olsen, Univ of Hawai’i Charm 2006 June 5-8, Beijing

  2. charmonium states All sub-open-charm threshold states have been identified All sub-open-charm threshold states have been identified Properties are pretty well understood

  3. Radiative transitions Gamma energy spectrum from y’g X decays accessible via E1 transitions from y’ Gaiser et al (Crystal Ball) PRD 34 711 Transition Partial width 23S1 (y’)13P2 (cc2) 17 keV Calculable from”1st principles” Good agreement with measurements 23S1 (y’)13P1 (cc1) 24 keV 23S1 (y’)13P0 (cc0) 24 keV 13P2 (cc2) 13S1(J/y) 420 keV 13P1 (cc1) 13S1(J/y) 290 keV 13P0 (cc0) 13S1(J/y) 120 keV

  4. Hadronic transitions G(y’p+p-J/y) 70 keV “allowed” “reasonable” agreement between measurement & theory c.f. Kuang & Yan PRD 41 155 G(y”p+p-J/y) 50 keV “allowed” G(y’hJ/y)  5 keV SUF(3) violating G(y’p0J/y)  0.3 keV isospin violating p0 h p+p- p+p-

  5. Recent results 21S0 found by Belle S.K.Choi et al PRL 89 102001 properties as expected 23P2 found by Belle hep-ex/0507033 properties as expected 11P1 found by CLEO hep-ex/0508037 properties as expected 13D1 g 13P1seen by CLEO hep-ex/0509030 G(meas) = 75  18 keV G(theor)  59~77 keV

  6. The potential model for cc charmonium mesons is robust and reliable

  7. Charmonium production in B decays J = 0 or 1 j=½ j=½ Spectator model says Jcc= 0 or 1 should dominate exclusive BK(cc) decays.

  8. Allowed decays all have Bf~10-3 hcK 0.9 x10-3 J/yK 1.0 x10-3 J/yK* 1.4 x10-3 J/yK12701.8 x10-3 y’K 0.7 x10-3 y’K* 0.9 x10-3 cc0K 0.6 x10-3 cc1K 0.7 x10-3 BK cc(J=2) still not seen

  9. XYZ particles • X(3872) • p+p- J/y in BKp+p-J/y • Z(3930) • DD in gg DD • Y(3940) • wJ/y in BK wJ/y • Z(3940) • DD* in e+e- J/y DD* • Y(4260) • p+p-J/y in e+e-g p+p- J/y

  10. gg Z(3931) DD sin4q (J=2) 4111 evts (5.5) M=3931 4  2 MeV =208 3 MeV Matches well to cc2’ expectations

  11. Z(3931) is most likely the cc2’ 3931

  12. X(3940) e+e-J/y + DD* e+e-J/y + X Seen in DD* but not DD; this impliescc1’ or hc” but e+e-J/y +cc0 not seen

  13. Is the X(3940) the hc”? 3940 Mass is about 150 MeV too low

  14. X(3872) BK p+p-J/y y’p+p-J/y X(3872)p+p-J/y C=+1 well established JPC = 1++ seems likely (see Pahklov’s talk) S.K. Choi et al PRL 91, 262001 M(ppJ/y)

  15. Expectations forc’c1 G(c’c1 g J/y)  11 keVBarnes Godfrey PRD 69 054008 G(c’c1 p+p- J/y) = ? • G(y’  p0J/y)  0.3 keV(“educated” guess?) Bf(XgJ/y) Bf(XppJ/y)  30 ~ 40 Expect: >200x discrepancy Bf(XgJ/y) Bf(XppJ/y) can our “education” really be this bad? Meas: =0.14 ± 0.05 cc1’ component of X(3872) is few% (at most?)

  16. X(3872) has no obvious cc assignment hc” Mass & width way too small Angular dist. wrong 3872 cc1’ Mass & G(gJ/y) way too small Mass & width too small Angular dist wrong cc0’ h2 pp hc is allowed ppJ/y is isospin forbidden

  17. Intriguing fact lowest mass charmed meson lowest mass spin=1 charmed meson MX3872 =3872 ± 0.6 ± 0.5 MeV mD0 + m D0* = 3871.2 ± 1.0 MeV Deuson? deuteron-like DD* bound state? 2 loosely bound qq color singlets with M= mD + mD* - d c c D p D* u u one p exchange attractive for 1++ Tornqvist PLB 590, 209 (2004)

  18. Threshold peak in BKD0D0p0 Within 2.3s of MX(3872) M=3875.4  0.7  0.4  1.0 MeV M-(mD0 + mD0*) = +4.2  0.7  0.4 MeV ~5s above D0D0* threshold)

  19. X(3872) = D0D*0 bound state? • JPC = 1++ is favored • M ≈ mD0 + mD0* • Large isospin violation is natural (& was predicted):  |D0D*0> = 1/2(|10> - |00>) • G(XgJ/y) < G(XppJ/y) was predicted • G(XD0D0p0) too large? • XDDp peak is seen (mass > mD0 + mD0*) Tornqvist PLB 590, 209 (2004) Equal mixture of I=1 & I =0 Swanson PLB 588, 189 (2004) Swanson PLB 598, 197 (2004)

  20. diquark-antidiquark? u c Maiani etalpredict a doublet of states PRD 71,014028 (2005) d c Xu= Xd= u c d c B+K+Xu B0K0Xd BaBar BaBar Maiani et alpredict: DM = M(Xu) – M(Xd) = 8  3 MeV BaBar (hep-ex/0507090) reports: DM = 2.71.3 0.2 MeV

  21. Y(3940) in BK wJ/y M≈3940 ± 11 MeV G≈ 92 ± 24 MeV G(Y3940 wJ/y)> ~7 MeV (an SUF(3)-violating decay) M(wJ/y) MeV S.K. Choi et al. (Belle) PRL94, 182002 (2005)

  22. Is the Y(3940) the cc1’ ? Y(3940)  w J/y enhanced by FSI ? w D Y FSI D* J/y It seems strange (to me) that an SU(3)-violating process can “short out” an SU(3)-allowed process If the Z(3930) is the cc2’ (which seems likely) the Y(3940) mass is too high for the cc1’

  23. Is the Y(3940) a ccg hybrid? c c g Mass too small Lightest hybrid M>~4.3 GeV

  24. Y(3940): What is it? eg.Brambilla et al (QWG) hep-ph/0412158 • Charmonium? • Conventional wisdom: (SU(3)-violating) wJ/y decayshould not be a discovery mode for a cc state with mass above DD & DD* threshold! • cc-gluon hybrid? • predicted by QCD, • decays to DD and DD* are suppressed (“open-charm” thresh = mD + m D** = 4.3 GeV) • large hadron+J/y widths can occur • masses expected to be 4.3 ~ 4.4 GeV (higher than what we see) Horn & Mandula PRD 17 898 others

  25. Y(4260) 10.58 GeV M=4259  8 MeV G = 88  23 MeV 4.26 GeV not seen in s(e+e-hadrons) at Ecm =4.26 GeV Y(4260) BES s(e+e-hadrons) scc~5nb J/ sideband B. Aubert et al. (BaBar) hep-ph/0506081 J.Z. Bai et al. (BESII) PRL 88 101802 Well above DD & DD* threshold but wide & found in a suppressed mode??

  26. CLEO-c results on the Y(4260) PRL 96 162003 (2006) 58  12 pb G(Y4260)ppJ/y > ~1MeV >10x higher than what we are used to

  27. Is the Y(4260) a hybrid? “open-charm” threshold for hybrids = MD+MD** 4285 MeV 4285MeV No sign of a YDD** “turn-on”

  28. summary • X(3872): • Existence well established • JPC = 1++ • Br(Xp+p- J/y) too high for charmonium • Br(XD0D0p0) too high for molecule • Br(B0 KSX3872) also too high for molecule(?) • DM too small for diquarks? • Mass too low for hybrid still under study (M(Xu) (from B+K+Xu) - M(Xd) (from B0KSXd) The more we learn more about it the more puzzling it becomes.

  29. other misfits • X(3940) Belle • Mass too low to be the hc” • Y(3940) Belle • G( Y3940 wJ/y) too high for charmonium • Mass too low for a hybrid • Y(4260) BaBar • G(y4260p+p-J/y) also way too high • 1--, but not seen in e+e- hadrons • no sign of a YDD** threshold cut-off by factor of ~103 by factor of >10

  30. “Homeless” mesons Y4260 Y3940 X3940 X3872 “conventional” wisdom X3872 = 4-quark state [(DD*) or (Cu)(Cu)] Y4260 = cc-gluon hybrid X3940 = hc” Y3940 = cc1’ with drastic revisions to charmonium model

  31. Conclusion • There is strong evidence for a new hadron spectroscopy in the 3.5~4.5 GeV mass region • Maybe more than one • This bodes well for BEPC2/BESIII

  32. 謝 謝 Thank you

  33. CDF If r-w interference is included L=0 & L=1 Cannot be distinguished.

  34. Back-up slides

  35. Xu – Xd Mass difference?: Belle: MXu – My’ = 185.7  0.6 MeV Preliminary MXd – My’ = 184.0  1.3 MeV M(Xu) – M(Xd) = 0.8  1.4 MeV

  36. Another one? • e+e- J/y + X • >4s)peak at M=394011 MeV • N=14833 evts • Width consistent w/ resolution (= 32 MeV) hc ‘ ‘ hc cc0 hc What is it? cc0 ? hc ?? ‘ “

  37. Look at e+e-J/y D(D(*)) • Reconstruct a J/y & a D • use D0K-p+ & D+K-p+p+ • Determine recoil mass

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