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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 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
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
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-
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
The potential model for cc charmonium mesons is robust and reliable
Charmonium production in B decays J = 0 or 1 j=½ j=½ Spectator model says Jcc= 0 or 1 should dominate exclusive BK(cc) decays.
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 BK cc(J=2) still not seen
XYZ particles • X(3872) • p+p- J/y in BKp+p-J/y • Z(3930) • DD in gg DD • Y(3940) • wJ/y in BK 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
gg Z(3931) DD sin4q (J=2) 4111 evts (5.5) M=3931 4 2 MeV =208 3 MeV Matches well to cc2’ expectations
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
Is the X(3940) the hc”? 3940 Mass is about 150 MeV too low
X(3872) BK 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)
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(XgJ/y) Bf(XppJ/y) 30 ~ 40 Expect: >200x discrepancy Bf(XgJ/y) Bf(XppJ/y) can our “education” really be this bad? Meas: =0.14 ± 0.05 cc1’ component of X(3872) is few% (at most?)
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
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)
Threshold peak in BKD0D0p0 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)
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(XgJ/y) < G(XppJ/y) was predicted • G(XD0D0p0) too large? • XDDp 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)
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 B0K0Xd BaBar BaBar Maiani et alpredict: DM = M(Xu) – M(Xd) = 8 3 MeV BaBar (hep-ex/0507090) reports: DM = 2.71.3 0.2 MeV
Y(3940) in BK 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)
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’
Is the Y(3940) a ccg hybrid? c c g Mass too small Lightest hybrid M>~4.3 GeV
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
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??
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
Is the Y(4260) a hybrid? “open-charm” threshold for hybrids = MD+MD** 4285 MeV 4285MeV No sign of a YDD** “turn-on”
summary • X(3872): • Existence well established • JPC = 1++ • Br(Xp+p- J/y) too high for charmonium • Br(XD0D0p0) 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 B0KSXd) The more we learn more about it the more puzzling it becomes.
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(y4260p+p-J/y) also way too high • 1--, but not seen in e+e- hadrons • no sign of a YDD** threshold cut-off by factor of ~103 by factor of >10
“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
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
謝 謝 Thank you
CDF If r-w interference is included L=0 & L=1 Cannot be distinguished.
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
Another one? • e+e- J/y + X • >4s)peak at M=394011 MeV • N=14833 evts • Width consistent w/ resolution (= 32 MeV) hc ‘ ‘ hc cc0 hc What is it? cc0 ? hc ?? ‘ “
Look at e+e-J/y D(D(*)) • Reconstruct a J/y & a D • use D0K-p+ & D+K-p+p+ • Determine recoil mass