(1760) f 0 (1710) f 0 (1790) f 0 (1810) PWA analysis M( ) Total f2(1910) f2(160) BG Using observed mass and width for f 0 (1810) in J/ f 0 (1710) f 2 (1910) f 2 (1640) BG (1760) > 10 f 0 M( ) (GeV/c 2 )
The existence of (1760) is confirmed Its mass and width were first correctly measured with PWA. Phys. Rev. D 73 (2006) 112007
Observation of X(1835) in at BESII The + - mass spectrum for decaying into + - and Statistical Significance 7.7 Phys. Rev. Lett. 95, 262001 (2005)
Observation of an anomalous enhancement near the threshold of mass spectrum at BES II M=1859 MeV/c 2 < 30 MeV/c 2 (90% CL) J/ pp M(pp)-2m p (GeV) 00.10.20.3 3-body phase space acceptance 2 /dof=56/56 acceptance weighted BW +3 +5 10 25 BES II Phys. Rev. Lett. 91, 022001 (2003)
Re-fit to J/ p pbar including FSI Include FSI curve from A.Sirbirtsev et al. ( Phys.Rev.D71:054010, 2005 ) in the fit (I=0) M = 1830.6 6.7 MeV < 153 MeV @90%C.L. In good agreement with X(1835)
Candidate of 0 -+ ppbar Bound State X(1835) could be the same structure as ppbar mass threshold enhancement X(1860)/X(1830). It could be a ppbar bound state since it dominantly decays to ppbar when its mass is above ppbar mass threshold. Its spin-parity should be 0 -+ : this would be an important test. There is already an (1760) nearby, so that X(1835) is very likely to be an unconventional 0 -+ meson.
This result cannot be explained by pure FSI effect, since FSI is a universal effect. FSI interpretation of the narrow and strong ppbar threshold enhancement is disfavored. This indicates that X(1860) has a production property similar to ’ meson. c.f. : This strong threshold enhancement is NOT observed in at CLEO No enhancement near threshold Phys.Rev.D73, 032001(2006)
FSI interpretation of the narrow and strong ppbar threshold enhancement is disfavored. This again indicates that X(1860) has a production property similar to ’ meson. c.f. : No strong threshold enhancement is observed in at BESII No significant narrow strong enhancement near threshold (2.0 if fitted with X(1860)) Phys.Rev.Lett.99, 011802 (2007)
This again disfavors FSI and indicates that X(1860) has a production property similar to ’ meson. c.f. : This also indicates X(1860) may have strong coupling to gluons as ’ meson. This strong threshold enhancement is NOT observed in at BESII No narrow strong enhancement near threshold BESII Preliminary
Summary of new studies on ppbar mass threshold structure X(1860) Pure FSI effect cannot explain X(1860) structure. X(1860) has production properties similar to ’ meson Why a baryonium (candidate) has a production properties similar to ’ meson? ’ excitation? Why an ’ excitation dominantly decays into ppbar above ppbar mass threshold?
Observation of mass threshold enhancement at BESII Phys. Rev. Lett. 96,162002 (2006)
We studied DOZI process: J/ + + + - 0 K + K - recoiling against
A clear mass threshold enhancement is observed Acceptance Side-bands
The radiative decay of J/ has been observed in the 58M J/ data. A significant structure of has been found near the mass threshold. PWA shows the structure favors 0 ++, with a mass, width 105 20 28 MeV, and the corresponding branch ration is (2.61 0.27 0.65)x10 -4. It could be a multiquark/hybrid/glueball state. Its relation with f 0 (1710),f 0 (1790)?
PWA of J/ + - and 0 0 at BESII Phys. Lett. B 642 (2006) 441
PWA of J/ + - and 0 0 M( + - ) M( 0 0 ) The channels fitted in PWA:
About f0(1500) It is first clearly observed in J/psi radiative decays. Its production rate in J/psi radiative decays: The production rate of f0(1500) in J/psi radiative decays is lower than f0(1710): It indicates f0(1710) has stronger coupling to gluons than f0(1500) which one contains more glueball content?
New observation of a broad 1 -- resonance in J/ K + K - 0 at BESII Phys. Rev. Lett. 97 (2006) 142002
J/ K + K - 0 00 background 0 sideband ? K*(892) K * (1410) X(1580) PID and kinematic fit can significantly reduce the dominant background from J/ + - 0.
Four decay modes are included : Amplitudes are defined by Covariant tensor formalism B.S. Zhou and D.V. Bugg, Eur. Phys. J. A16, 537(2003) BW with energy-dependent width J.H. Kuhn, A. Satamaria, Z. Phys. C48, 445 (1990). Partial Wave Analysis of J/ K + K - 0 events
Parity conservations in J/ K + K - 0 requires that spin-parity of K + K - should be 1 --,3 --,… PWA fit with and phase space (PS) gives: ( can be ruled out by much worse likelihood ) X pole position big destructive interference among and PS Partial Wave Analysis of J/ K + K - 0 events
Broad X cannot be fit with known mesons or their interference It is unlikely to be (1450), because: The parameters of the X is incompatible with (1450). (1450) has very small fraction to KK. From PDG: It cannot be fit with the interference of (770), (1900) and (2150): The log-likelihood value worsens by 85 ( 2 =170).
How to understand broad X(1580)? Search of a similar structure in J/ K S K will help to determine its isospin. X(1580) could have different nature from conventional mesons: There are already many 1- - mesons nearby. Width is much broader than other mesons. Broad width is expected for a multiquark state.
A structure at 2175MeV was observed in e + e - f 0 (980), via initial- state radiation at BABAR. Evidence of a new 1 -- resonance Y(2175) at BaBar Phys. Rev. D 74 (2006) 091103(R)
What is Y(2175)? A conventional state? An analog of Y(4260) ( )? An 4-quark state? More experimental information needed, especially we can search for it in J/psi decays at BESII and BESIII.
PS, eff. corrected Observation of a strong enhancement near the threshold of mass spectrum at BES II (Arbitrary normalization) BES II NX*NX*
A strong enhancement is observed near the mass threshold of M K at BES II. Preliminary PWA with various combinations of possible N* and Λ* in the fits —— The structure N x *has: Mass 1500~1650MeV Width 70~110MeV J P favors 1/2 - The most important is: It has large BR(J/ψ pN X *) BR(N X * KΛ) 2 X 10 -4, suggesting N X * has strong coupling to KΛ.
N x * is N(1535)? From: If N x * is N(1535), we would have Then N(1535) would have very large ssbar component (a 5-quark system).
Such a big coupling to K of N(1535) is NOT observed in process at SAPHIR Phase Space shape
A ΛK resonance predicted by chiral SU(3) quark model Based on a coupled- channel study of ΛK and ΣK states in the chiral SU(3) quark model, the phase shift shows the existence of a ΛK resonance between ΛK and ΣK mass threshold. ( F. Huang, Z.Y. Zhang et al. Phys. Rev. C71: 064001, 2005 ) E cm – ( M Λ +M K ) (MeV)
The KΛ mass threshold enhancement N X (1610) could be a KΛ bound/resonant state. Whether N X (1610) is N(1535) needs further study.
No obvious N* in Dalitz plot. We measured: Study of at BESII
J/ decays are an ideal factory to search for and study light exotic hadrons: The production cross section of J/ is high. The production BR of hadrons in J/ decays are one order higher than ’ decays (“12% rule”). The phase space to 1-3 GeV hadrons in J/ decays are larger than decays. Exotic hadrons are naively expected to have larger or similar production BR to conventional hadrons in J/ decays. Clean background environment compared with hadron collision experiments, e.g., “J P, I” filter.
One Important Physics Goal of BESIII With 10 10 J/psi events, we hope to answer: Whether glueballs exist or not? Naively, we estimate in each exclusive decay mode: If the eff. is about 20%, we would have 20000 events for each decay mode we should observe a relative narrow (width: 50~200MeV) glueball if it exists.
About scalar glueball Many scalar mesons in the mass range 1.4~1.8 GeV, where a scalar glueball is predicted to be. More studies will be performed at BESIII. More theoretical studies are also needed: Not only glueball mass, but also width Decay patterns Production rate in J/psi radiative decays Mixing mechanism
2 ++ glueball candidates Lattice QCD predicts the 2 ++ glueball mass in the range of 2.2~2.4 GeV (2230) was a candidate of 2 ++ glueball: It was first observed at MARKIII in J/ KK It was observed at BES I in J/ KK, , ppbar It was not observed at DM2.
The situation at BESII The mass plots shows no evident (2230) peaks in J/ KK, , ppbar, which is different from BESI. However, it is difficult to exclude its existence since we may still need a small signal at the 4.5 level in the PWA based on our preliminary study. Its mass, width and BR are consistent with BESI and MARKIII results Difficult to draw firm conclusion at present. We hope to give a final answer at BESIII on (2230)
Other 2 ++ glueball candidates No other obvious good candidates have been observed in J/psi radiative decays in the mass range predicted by LQCD. What does it mean: LQCD prediction might not be very reliable, or BR(J/ G)xBR(G hh) is small ( <10 -4 ) so that we don’t have the sensitivity to observe it ( quite possible ), or, The width of a glueball is very large ( ~1GeV, E.Klepmt ).
Where to search for the 0 -+ glueball? Lattice QCD predicts the 0 -+ glueball mass in the range of 2.3~2.6 GeV. (1440) and X(1835) were suggested being possible candidates, but their masses are much lower than LQCD predictions.
No 0 -+ glueball candidate observed in the mass range 2.3~2.6 GeV No evidence for a relatively narrow state ( 100 ~ 200 MeV width ) above 2GeV in Again: LQCD reliable? Production rate could be very low. Glueball width could be very large.
Summary New results on light 0 -+,0 ++ and 1 -- mesons as well as excited baryons were briefly reviewed. We would expect more new observations on light hadron spectroscopy at BESIII and we hope to answer whether glueballs exist or not at that time.
Discussion on KΛ mass threshold enhancement N X (1610) N X (1610) has strong coupling to KΛ: From (S&D-wave decay) and is a P-wave decay, we can estimate From BESII, The phase space of N X to KΛ is very small, so such a big BR shows N X has very strong coupling to KΛ, indicating it has a big hidden ssbar component. (5-quark system)
Non-observation of N X in suggests an evidence of new baryon : It is unlikely to be N*(1535). If N X were N*(1535), it should be observed in process, since: From PDG, for the N* in the mass range 1535~1750 MeV, N*(1535) has the largest, and from previous estimation, N X would also have almost the largest BR to KΛ. Also, the EM transition rate of N X to proton is very low.