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Exotic Hadrons ( 奇特强子态 )

Exotic Hadrons ( 奇特强子态 ). Changzheng YUAN ( 苑长征 ) (BES & Belle Collaborations) 中国科技大学 2009 年 10 月 23 日. Hadrons ： normal & exotic. Hadrons are composed from 2 (meson) or 3 (baryon) quarks Quark model QCD allows hadrons with N quarks 2, 3

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Exotic Hadrons ( 奇特强子态 )

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  1. Exotic Hadrons(奇特强子态) Changzheng YUAN (苑长征) (BES & Belle Collaborations) 中国科技大学 2009年10月23日

  2. Hadrons：normal & exotic • Hadrons are composed from 2 (meson) or 3 (baryon) quarks Quark model • QCD allows hadrons with Nquarks2, 3 • glueball： Nquarks = 0 (gg, ggg, …) • hybrid： Nquarks = 2 + excited gluon • Multiquark state： Nquarks > 3 • molecule： bound state of more than 2 hadrons

  3. A bit of history on exotics hunting • “The absence of exotics is one of the most obvious features of QCD” – R. L. Jaffe, 2005 • Deuteron H state, d’, d*, -- bound state • No solid signature of glueballs • Pentaquark state appeared and disappeared (“The story of pentaquark shows how poorly we understand QCD” – F. Wilczek, 2005) • Do we still have hope? Yes!

  4. Outline The XYZ states at B-factories + other experiments XYZ  charmonium + light meson • X(3872) – molecular state? • XYZ(3940) & X(3915) –charmonia? • Y(4140) & X(4350) –tetraquark states? • Y states in ISR – hybrids? • Z+(4430)/Z+(4050)/Z+(4250) – cannot be charmonia! • (1S)+X/Y – new results from Belle! • Opportunity at BESIII and other experiments.

  5. Most of the XYZ from B-factories + BES, CDF, D0

  6. Charmonium spectroscopy We were very pride: Potential models worked well for charmonium. (2S+1)LJ y(4415) y(4160) y(4040) Mass (MeV) Open charm threshold. y(3770) h’c y’ cc2 cc1 hc hc cc0 J/y hc (potential Models) JPC No big progress in last century!

  7. Then we found lots of XYZ states What are they ? Charmonium? Hybrid? Tetraquark? Molecule? … (2S+1)LJ Z(4430) Z(4250) Z(4050) M(MeV) Y y(4415) ? y(4160) X(3872) Y(4140) y(4040) XYZ(3940) X Z Y Open charm threshold y(3770) X(3915) X(4160) Y(4008) Y(4140) Y(4260) Y(4360) X(4350) Y(4660) h’c y’ cc2 cc1 hc cc0 J/y (potential Models) hc JPC Not all XYZ states are charmonia!

  8. X(3872)first and most puzzling state(observed in 2003 at Belle)

  9. X(3872)p+p-J/y recent results PRD77,111101 (2008) 413 fb-1 arXiv:0809.1224 605 fb-1 Ns=93±17 8.6 B±XK± B0XK0 Ns=9±5 2.3 = (2.7±1.6±0.4) MeV

  10. X(3872)p+p-J/y in CDF recent results Fits for 2 nearby states ~6000 events! arXiv:0906.5218 dMX < 3.6 MeV @ 95% CL MX = 3871.61 ± 0.16 ± 0.19 MeV

  11. M(X(3872)) p+p-J/y mode only <MX>= 3871.46 ± 0.19 MeV No sign of a mass doublet a la Maiani et al new Belle meas. new CDF meas. PRL103, 152001 PRL103, 152001 (2009) MD0 + MD*0. BES III can improve on this Dm(deuteron) = -2.2 MeV m = -0.35 ± 0.41 MeV

  12. Mass in X3872D*0D0 Belle 2006, 414/fb X3872D0D0p0 BaBar 2006, 347/fb X3872D0D*0(p0D0,gD0) 414fb-1 D0D0p0 Fit with truncated BW in both exps. Is this the higher mass partner state predicted by Maiani et al?

  13. Belle update 605fb-1 D0D*0(D0g) Nsignal= 48±11 evts Signif.=8.8s 605fb-1 D0D*0(D0p0) Agree with J/ mode. Fit with a phase-space modulated BW Can also use other parameterizations to do the fit

  14. X(3872)gJ/y & gy’ from BaBar PRL 102, 132001 (2009) 3.5s X(3872) J/y g X(3872)y(2S) g 3.0s BABAR BABAR Bf(B+X3872K+)×(X3872J/yg) =(2.8 ± 0.8 ± 0.2) × 10-6 Bf(B+X3872K+)×(X3872y’g) =(9.5 ± 2.7 ± 0.9) × 10-6 • C-parity = +1 (Belle also measured J/: 0505037) • JPC = 2 -+ disfavored  multipole suppression • Bf(X3872gy’) > Bf(X3872gJ/y) bad for molecules Swanson PLB 598, 197 (2004)

  15. BKp X(3872) from Belle arXiv:0809.1224 605 fb-1 Very weak K*(890) ~90 events Backgrounds from J/ sidebands M(ppJ/y) in GeV M(Kp) in GeV Bf(BJ/y K*0)/Bf(BJ/y KpNR) ~ 4. Similar ratios for c1, (2S)! X is very different from other charmonia. Pure 3-body B decays? Check Dalitz plot!

  16. Production of X(3872) in B decays

  17. Decay of X(3872)

  18. Decay of X(3872)

  19. X(3872) summary • Mass: Very close to D0D*0 threshold • Width: Very narrow, < 3 MeV • JPC=1++ favoured • Production • in pp collison – similar to charmonia • In B decays – KX similar to cc, K*X smaller than cc • Decay BR: open charm ~ 50%, charmonium~O(%) • Nature (very likely exotic) • Loosely D0D*0 bound state (like deuteron?)? • Mixture of excited c1 and D0D*0 bound state? • Many other possibilities (if it is not c1, where is c1?)

  20. The states near 3940 MeV-circa 2005- probably different not seen in wJ/y not seen in DD* Probably the cc2’ X(3940) Y(3940) Z(3930) gg DD e+e- J/y DD* BKwJ/y PRL94, 182002 M(wJ/y) M(DD) M(DD*) M≈3940 ± 11 MeV G≈ 92 ± 24 MeV M = 3929±5±2 MeV Gtot = 29±10±2 MeV Nsig = 64 ± 18 evts M = 3942 +7± 6 MeV Gtot = 37 +26 ±12 MeV Nsig = 52 +24 ± 11 evts -6 BaBar: PRL 101, 082001 -15 M≈3914± 5 MeV G≈ 33± 10 MeV -16 PRL 96, 082003 PRL 100, 202001

  21. New peak inggwJ/y X preliminary M: 3914  3  2MeV, G: 23  10 +2-8 MeV, Nres = 55  14 +2-14 events Signif. = 7.7s, Background only fit

  22. Could it be the Z(3930)? M = 3929±5±2 MeV Gtot = 29±10±2 MeV Nsig = 64 ± 18 evts gg DD M: 3914  3  2MeV, G: 23  10 +2-8 MeV, Nres = 55  14 +2-14 evts gg J/

  23. Gggpartial width GggB(wJ/y) = 69  16 +7eV (JP=0+) -18 GggB(wJ/y) = 21  4 +2 eV (JP=2+) -5 For comparison: Z(3930): GggB(DD) = 180  50±30 eV B(cc2’wJ/y) B(cc2’DD) If X(3915) = Z(3930) = cc2’  0.08 Huge for above-open-charm-threshold charmonium

  24. The 4 states near 3940 Mass(GeV) Range: (s(stat.)s(sys.)) Y(3940) Belle X(3940) Z(3930) Good overlap with BaBar “Y(3940)” values This X(3915) Width(GeV)

  25. cc assignments forX(3915), X(3940) & Y(3940)? hc’’’ hc” cc0’ 3940MeV 3915MeV • Y(3940) = X(3915) = cco’ ?  G(wJ/y) too large? • X(3940) = hc”?  mass too low? (3S)=4040 MeV • Z(3940) = cc2’ ?  (M(J=2,0)=15±7 MeV?)

  26. States decaying into J/Evidence for Y(4140) and a New Resonance at 4.35 GeV

  27. The CDF Y(4140)J/ • B+Y(4140)K+ • 14±5 events, >3.8 • Mass: 4143.0 ± 2.9 ± 1.2 MeV • Width: 11.7+8.3-5.0 ± 3.7 MeV (It is narrow!) PRL102, 242002 (2009) D*sD*s molecule? [cscs] tetraquark?

  28. Preliminary Y(4140) not significant at Belle • Belle: B→J/ψK with 772M BB M(J/ψ) fit with Y(4140) parameters fixed [but low effciency at J/ threshold]

  29. 825 /fb Searched for in J/ preliminary • No Y(4140) • A few events accumulate at 4.35 GeV in both J/ee and  modes JP=0+: ΓγγBr(Y(4140)) →J/) < 39 eV @ 90% C.L. JP=2+: ΓγγBr(Y(4140)) →J/) < 5.7 eV @ 90% C.L.

  30. Y(4140)= Ds*+Ds*- molecule? T. Branz et al., PRD80, 054019 (2009): if Y is Ds*+Ds*- molecule • Molecule state disfavored. JP=0+: ΓγγBr(Y(4140)) →J/) = 176+137-93 eV JP=2+: ΓγγBr(Y(4140)) →J/) = 189+147-100 eV

  31. 825 /fb Fit to J/ invariant mass • unbinned maximum likelihood method • BW convoluted with Double Gaussian resolution function • mass resolution is 5.5 MeV at 4.35 GeV S.S.=3.9, const. bkg S.S.=3.2, linear bkg preliminary JP=0+: ΓγγBr(X(4350)) →J/) =6.4+3.1-2.3 ± 1.1 eV JP=2+: ΓγγBr(X(4350)) →J/) =1.5+0.7-0.5 ± 0.3 eV

  32. 825 /fb Preliminary results • M(X(4350))=4350.6+4.6-5.1± 0.7 MeV/c2 • Γ=13.3+17.9-9.1 ± 4.1MeV/c2 • N (X(4350))=8.8+4.2-3.2 • Statistical significance: 3.2-3.9 • Excited P-wave charmonium? • Tetraquark? • Fl. Stancu, arXiv: 0906.2485 • D*sD*s0 molecule at • 4.34±0.09 GeV? • J.R.Zhang et al., arXiv:0905.4672

  33. R values/ states/Y states From PDG } The Y states should also appear in this plot (between 4.0 and 4.7 GeV!) JPC = 1-- ’, ’’, Y…

  34. PRL 99, 182004 (2007) PRL 99, 142002 (2007) Y(4660) 6 Y(4360) Y(4260) Y(4008) 7σ 550 fb-1 670 fb-1 arXiv:0808.1543 PRL 98, 212001 (2007) Y(4360) Y(4260) 298 fb-1 Y(4660) ? 454 fb-1 Y(4008) ? M(J/ψππ) M(ψ(2S)ππ) Y family (vector states) e+e-→J/ψπ+π- γISR e+e-→ψ(2S)π+π- γISR Above DD threshold, decay to open charm?

  35. PRD77,011103(2008) DD ? DD* (4160) Y(4350) PRL98, 092001 (2007) Y(4008) D*D* Y(4260) (4415) (4040) 0908.0231[hep-ex] PRL100,062001(2008) DD*π Y(4660) Y(4260) ψ(4415) DDπ PRL101, 172001(2008) Λc+Λc– e+e-→open charm γISR Y family • Y(4008), Y(4260), Y(4360), Y(4660) don’t match peaks in D(*)D(*) Xsection • Widths for ψππ transition too large for conventional charmonia • Y(4260) is DD1 molecule/ccg hybrid? DD1[→DD*π] decay should dominate but no signal found M=4630 Y(4660) ? M(DD*)

  36. What are the Y states? • Between 4 and 4.7 GeV, at most 5 states expected (3S, 2D, 4S, 3D, 5S), 7 observed • Hybrids are expected in this mass region • Molecular states? • Cannot rule out threshold effect/FSI/… • Y(4260), Y(4360), Y(4660) are all narrow and similar

  37. Charged state with hidden charmZ+(4430) and moreUnambiguous tetraquark state?

  38. Z+(4430) 657M BB M2(ψ(2S)π+) K2*(1430) K*(890) M2(ψ(2S)π+) afterK* veto M2(Kπ+) PRL100, 142001 (2008) Z(4430)±→ψ(2S)π± • Found in ψ(2S)π+ from B→ψ(2S)π+K. Z parameters from fit to M(ψ(2S)π+) • Confirmed through Dalitz-plot analysis of B→ψ(2S)π+K • B→ψ(2S)π+K amplitude: coherent sumof Breit-Wigner contributions • Models: all known K*→Kπ+ resonances only all known K*→Kπ+ and Z+→ψ(2S)π+ favored by data • [cu][cd] tetraquark? neutral partner in ψ’π0 expected • D*D1(2420)molecule?should decay to D*D*π Significance: 6.4σ –̶̶̶̶̶̶ –̶̶̶̶̶̶fit for model with K*’s only –̶̶̶̶̶̶ –̶̶̶̶̶̶fit for model with K*’s and Z PRD80, 031104 (2009)

  39. Belle peak position M((2S)+) Z±(4430) in BaBar data? PRD79, 112001 (2009) • Fits to M(ψ(2S)π+): no significant Z(4430) signal • M(ψ(2S)π+) is statistically consistent between BaBar & Belle • Better to have one more experiment to examine it (χ2/ndf=54.7/58)

  40. ??? M2(χc1π+) K2*(1430) K*(1680) K*(892) K0*(1430) K3*(1780) M2(K-π+ ) Two Z±→χc1π± • Dalitz-plot analysis of B0→χc1π+K-χc1 →J/ψγwith 657M BB • Dalitz plot models: known K*→Kπ only K*’s + one Z →χc1π± K*’s + two Z± states  favored by data PRD 78, 072004 (2008) Significance: 5.7 –̶̶̶̶̶̶ –̶̶̶̶̶̶fit for model with K*’s –̶̶̶̶̶̶ –̶̶̶̶̶̶fit for double Z model –̶̶̶̶̶̶ –̶̶̶̶̶̶Z1 contribution –̶̶̶̶̶̶ –̶̶̶̶̶̶Z2 contribution M(χc1π+) for 1<M2(K-π+)<1.75GeV2 Waiting for experiments to confirm them!

  41. Search for X/Y states in Y(1S) radiative decays

  42. Y(1S)γX/Y NEW! ●σ(e+e-  ψ(2S))=20.2 ±1.1(stat.) pb ● Except for the ISR produced ψ(2S), there are only a few events scattered above the ψ(2S) peak ● No events from J/ ψ sidebands. But one candidate around X(3872) mass region ● B(Y(1S)γX(3872))B(X(3872)π+π-J/ψ)<2.2x10-6 5.8 fb-1 @ Y(1S) res. 1.8 fb-1@ 9.43 GeV preliminary ● There are two events scattered above 3.6 GeV. One is at 3.67 GeV, the other is at 4.23 GeV. The orresponding 3π masses are at 0.54 GeV and 1.04 GeV ●B(Y(1S)γX(3872))B(X(3872) π+π-π0J/ψ)<3.4x10-6 ●B(Y(1S)γX(3915))B(X(3915) ω J/ψ)<3.4x10-6 preliminary B(Y(1S)γY(4140))B(Y(4140)  J/ψ)<2.6x10-6

  43. Y(1S)γXCJ /ηc NEW! For comparison, we also studied: 1.8 fb-1@ 9.43 GeV 5.8 fb-1 @ Y(1S) res. 5.8 fb-1 @ Y(1S) res. ●No clear XcJ or η signal is observed ● B(Y(1S)γXc0)<5.0x10-4 ● B(Y(1S)γXc1)<1.5x10-5 ●B(Y(1S)γXc2)<1.2x10-5 ●B(Y(1S)γ ηc)<6.4x10-5 ● The above upper limits do not contradict with the calculation in K.T.Chao et al.,hep-ph/0701009 ηcKSKπ, K+K- π+ π-, 2(π +π-), 2(K+K-) and 3(π +π-)

  44. Possible BESIII contribution From PDG • BESII fine scan 10 years ago (one of the best cited BES papers) • BESIII will do it (USTC/IHEP group will submit proposal) • The Y states should also appear in this plot • The X states via decays of excited s; is the Z+ iso-vector?

  45. Summary of the talk Many XYZ states were observed in B-factories and other experiments in XYZ  charmonium + light meson They could be exotic hadrons such as molecular state, tetraquark state, or hybrids or just charmonium states, threshold effect, FSI effect or some other unknown QCD effect. Both theorists and experimentalists should continue work hard and patiently for possibly very rare (even non-existing) exotic hadrons! (Is exotic hadron another ether?) Thanks a lot.

  46. backup

  47. XYZ states neutral X and Y charged Z

  48. Shows up in all data subsamplesZ(4430)

  49. Belle-BABAR comparison (Z(4430)) Uncorrected data in the K* veto region BABAR preliminary Both Belle and BABAR data are re-binned (to calculate χ2) and side-band subtracted The BABAR data are normalized (*1.18) to the Belle sample; Luminosity ratio is 1.46 The data distributions are statistically consistent (χ2=54.7/58) From J. Brodzicka, LP09

  50. BaBar doesn’t see a significant Z(4430)+ “For the fit … equivalent to the Belle analysis…we obtain mass & width values that are consistent with theirs,… but only ~1.9s from zero; fixing mass and width increases this to only ~3.1s.” Belle PRL: (4.1±1.0±1.4)x10-5

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