Recent Results from BES Weiguo Li IHEP, Beijing Representing BES collaboration ICFP2005 NCU, Chungli, Taiwan Oct. 5, 2005

BESII Detector VC:  xy = 100  m TOF:  T = 180 ps  counter:  r  = 3 cm MDC:  xy = 250  m BSC:  E/  E= 22 %  z = 5.5 cm  dE/dx = 8.4 %   = 7.9 mr B field: 0.4 T  p/p=1.8  (1+p 2 )  z = 2.3 cm Dead time/event: 〈 10 ms

Data from BESI and BESII

Recent J/  Results from BESII Multiquark candidates study at BES * pp threshold enhancement in * observation of X(1835) in * p  threshold enhancement in * K  threshold enhancement in *  enhancement in Light scalar mesons -- , , f0(980), f0(1370), f0(1500) … Excited baryon states Measurements of J/  and  c decays

During the past two years, a lot of surprising experimental evidences, including some BES results showed the existence of hadrons that cannot (easily) be explained in the conventional quark model. J/  decay is a good place to search for the new form of hadrons.

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) body phase spaceacceptance  2 /dof=56/56 acceptance weighted BW  10  25 BES II Phys. Rev. Lett., 91 (2003)

X(1835) 5.1  hep-ex/ Accepted by PRL Observation of X(1835) in X(1835) 6.0 

Statistical Significance 7.7  BESII Preliminary Combine two channels X(1835) 7.7  BESII Preliminary

M =  6.7 MeV  = 0  93 MeV In good agreement with X(1835) Include FSI curve from A.Sirbirtsev et al.(hep-ph/ ) in the fit (I=0) Refit to J/    pp including FSI BES II Preliminary

X(1860) from BES has large BR to pp BES measured: For a 0 -+ meson: So we would have: Considering that decaying into pp is only from the tail of X(1860) and the phase space is very small, such a BR indicates X(1860) has large coupling to pp !

X(1835) could be the same structure as pp mass threshold enhancement. It is likely to be a pp bound state since it dominantly decays to pp when its mass is above pp mass threshold.  ’  mode is expected to be the most favorable decay mode for a pp bound state below pp mass threshold G.J. Ding and M.L. Yan, PRC 72 (2005)

Observation of an anomalous enhancement near the threshold of mass spectrum at BES II BES II 3-body phase space For a S-wave BW fit: M = 2075  12  5 MeV Γ = 90  35  9 MeV Phys. Rev. Lett. 93, (2004)

Similar enhancement also observed in 4  away from phase space.

PS, eff. corrected Observation of a strong enhancement near the threshold of mass spectrum at BES II (Arbitrary normalization) BES II NX*NX* BES II Preliminary

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. BES II Preliminary

Observation of  threshold enhancement in J/    DOZI process M3M3 M KK    BES II Preliminary

A clear threshold enhancement is observed Phase Space Eff. curve Side-band S wave fit: BES II Preliminary

Study of the scalars  There have been hot debates on the existence of  and .  Lattice QCD predicts the 0 ++ scalar glueball mass in the range GeV. f 0 (1500) and f 0 (1710) are good candidates.

 study  in study  in  study f 0 (980), f 0 (1370), f 0 (1500), f 0 (1710) and f 0 (1790) in 0 ++

The study of  evidence for a low mass pole in the early DM2 and BESI data on J/   . huge event concentration in the I=0 S-wave  channel seen in M  ~ 500 – 600 MeV in the pp central production exp. to explain  scattering phase shift data ，  should be introduced in chiral perturbative theory. FNAL E791 exp. D +  +  -  + data

The  pole in at BESII M(  ) M(  +  -  0 ) M(  +  - ) 00   

Fit to J/  →  +   (whole mass region) f 0 contribution preliminary b 1 (1235) Method I: Channels fitted to the data: J/  f 2 (1270)   f 0 (980) b 1 (1235)   ’(1450)  f 2 (1565)  f 2 (2240)  f 2 contribution

Fit to J/  →  +   (M  < 1.5 GeV) Method II: Channels fitted to the data: J/  f 2 (1270)   f 0 (980) b 1 (1235)  phase space f 0 contribution f 2 contribution

Breit-Wigner for  :

Averaged pole position: MeV Phys. Lett. B 598 (2004) 149 BW form Pole position (MeV) Const.   with  Adler zero form BW formMass(MeV)Width(MeV) Pole position(MeV) Const.   with   with  (HQ) I II Fit results:

The study of  A possible  pole is controversial.  Some analyses of LASS K  scattering data need  (800), some don’t.  Scadron et al. favors a nonet made up of ,  (800), f 0 (980) and a 0 (980).  Julich group used t-channel exchanges to explain K  scattering data.  evidence of  in FNAL E791 data on D +  K -  +  +  slightly lower statistics of CLEO D 0  K -  +  0 data find no evidence of   FOCUS data on K +  K -  +  + require K* 0 interfere with either a constant amplitude or a broad 0 + resonance in K 

κ hep-ex/ Submitted to PLB

BES Preliminary K* 0 (1430) 

Pentaquark searches  not forbidden by QCD: definite evidence of pentaquark states would be an important addition to our understanding of QCD.  a baryon with S=+1 is a natural candidate  + (1540)

Need more experimental facts (through different processes) BES: e + e - collision; has relatively clean data samples with less backgrounds investigate the pentaquark state  in the hadronic decays of charmonium

No pentaquark state  (1540) (or  ) is observed. J/  (2S)

Upper 90% C.L. PRD70 (2004)

Lattice QCD: the lightest scalar glueball in the region of GeV Glueball searches should be performed in simultaneously. I will skip the other parts of J/  decay results to save time, please refer to the BES talks at Hadron05. Study of other scalars

BES preliminary  c0 →  +   K + K  Different way for scalar study: 1.Start from J PC =0 ++, 1 ++, Start from gluon+gluon 3.Pair production of scalars, very different information than in J/  decays 1371 evts  c0  c1  c2 Can study different kinds of resonances: (     )( K  K  ) (K    )(K    ) (K   ) K  (2S) and  CJ Decays hep-ex/ Submitted to PRD

f 0 (1710) f 0 (2200) f 0 (980) BES preliminary,  c0 →  +   K + K  (  +   ) ( K + K  ) Q. Zhao, hep-ph/ , try to understand these data and the scalars … f 0 (980) f 0 (1370)  (770)

(K    )(K    ) K* 0/2 (1430) K* 0 (1950) K*(892) 0 With kappa-kappa Without kappa-kappa  S=39. BES preliminary  c0 →  +   K + K 

1371 events M(K  )  [896±60] M(   )  [700,850] K 1 (1270) K 1 (1400) K 1 (1270) BES preliminary,  c0 →  +   K + K  The mixing angle between K 1A and K 1B  >57 degrees, while in  ’ decays to K 1 K, the angle is  <29 degrees. Why? (K   )K

 Violation found by Mark-II, confirmed by BESI at higher sensitivity.  Extensively studied by BESII/CLEOc  VP mode:  , K *+ K - +c.c., K *0 K 0 +c.c.,  0,…  PP mode: K S K L  BB mode: pp, , …  VT mode: K*K* 2,  f 2 ’,  a2,  f 2  3-body: pp  0, pp ,  +  -  0, …  Multi-body: K S K S hh,  +  -  0 K + K -, 3(  +  - ), … “12% rule” and “  puzzle” K*K ρπ MARK-II

 In Potential model, if J/ ,  ’, and  ’’ are pure 1S, 2S, and 1D states, one expects Extension of the “12% rule”  but  ’ and  ’’ are known not pure 2S and 1D states, PRD17, 3090 (1978); 21, 203 (1980); 41, 155(1990); …  Let’s look at data … (and first, the story of  )

BESII CLEOc 229  0 s 196  0 s BES and CLEOc in good agreement! BESII: PLB619, 247 (2005) CLEOc: PRL94, (2005)  ’   +  -  0

Dalitz plots after applying  0 mass cut! Very different from J/  3  ! Similar Dalitz plots, different data handling techniques: PWA vs counting! J/   ’   +  -  0 CLEOc BESII  ’   is observed, it is not completely missing, BR is at level!

J/   +  -  0 Make  mass cut, and count events PWA analysis assuming  interferes with excited  states L. P. Chen and W. Dunwoodie, Hadron’91, MRK3 data Very different! PDG: 1.27  0.09%

phase Continuum contribution is crucial in  ’’ analysis: 1.Total  ’’ charmless decays (<2nb) is much less than total continuum process (~16nb), 2.Interference between amplitudes φ interference  ’’   +  -  0 BESII preliminary Very small in  ’’ decays

BESII preliminary 3.773GeV BES and CLEOc are in good agreement! X-section at  ’’ peak is smaller than at continuum! BESII: hep-ex/ CLEOc: CLEO-CONF  ’’   +  -  GeV 3.773GeV 3.670GeV CLEOc preliminary

BESII preliminary BES and CLEOc are in good agreement! X-section at  ’’ peak is smaller than at continuum!  non-zero  ’’   amplitude. BESII: hep-ex/ CLEOc: CLEO-CONF  ’’   +  -  CLEOc preliminary Subtle difference in handling efficiency and ISR correction.

BESII: hep-ex/ CLEOc: CLEO-CONF  ’’    Wang, Yuan and Mo:PLB574,41(2003) Total cross section  B depends on efficiency and ISR correction, efficiency and ISR correction depends on  B (s) ! Iteration is necessary! Three unknowns with two equations --- One can plot the BR versus phase .

 ’’    BESII: hep-ex/ CLEOc: CLEO-CONF BES data restrict BR and phase in a wide range C.L.): CLEOc data further restrict BR and phase in a ring*. At  =-90  : *Toy MC is used to get BR from CLEOc data (not CLEO official results)!

In S-D mixing model, using mixing angle θ=12°, using Rosner’s assumption (12% rule for 1S and 2S), one predicts Q ’ ρπ =( )% ! J/ ,  ’,  ’’  ρπ Partial width of ψ’’  ρπ is larger than that of ψ’  ρπ! hard to understand if ψ’’ is pure 1D state, also hard if ψ’’ is 2S and 1D mixture.  -90  or imperfect model?

Other  ’ decay modes   ’    is suppressed by a factor of 60!   ’’    is enhanced!  Other modes may supply more information! We list a few new measurements using BESII/CLEOc data …

 ’  VP K * (892)K+c.c. K *0 Br ± =(2.9±1.7 ±0.4)  10 –5 Br 0 =(13.3±2.7 ±1.7)  10 –5 K*  Good agreement! Large Isospin violation! Both modes suppressed! BESII : PLB614, 37 (2005) CLEOc: PRL94, (2005) Br 0 =(9.2±2.7 ±0.9)  10 –5 Br ± =(1.3±1.0 ±0.3)  10 –5 BESII

 ’  VP CLEOc: PRL94, (2005) BESII : PRD70, (2004) PRD70, (2004) Some modes are suppressed, while some others obey the 12% rule!

Multi-body  ’ decays BESII: PRD71, (2005) CLEOc: PRL95, (2005) BESII, preliminary Some modes are suppressed, some are enhanced, while some others obey the 12% rule! CLEOc preliminary: hep-ex/

Search for  ’’ decays to light hadrons CLEOc preliminary: LP Same operation as for  ’’   should done for all the modes to extract the BRs of  ’’ decays. BR(  ’’  final state)   =-90 degrees as in J/  and  ’ decays?  Any way to choose one solution? Some x-sections agree, some very different.

“12%” rule and “0.02%” rule   ’  VP suppressed   ’  PP enhanced   ’  VT suppressed   ’  BB obey/enhan.  Multi-body –obey/sup. The  ’’ decays into light hadrons may be large --- more data and more sophisticated analysis are needed to extract the branching fractions from the observed cross sections. Why D-wave decay width so large? Model to explain J/ ,  ’ and  ’’ decays naturally and simultaneously? S-D mixing in  ’ and  ’’ [J. L. Rosner, PRD64, (2001)] DD-bar reannihilation in  ’’ (J. L. Rosner, hep-ph/ ) Four-quark component in  ’’ [M. Voloshin, PRD71, (2005)] Survival cc-bar in  ’ (P. Artoisenet et al., hep-ph/ ) Other model(s)? Seems no obvious rule to categorize the suppressed, the enhanced, and the normal decay modes of J/  and  ’. The models developed for interpreting specific mode may hard to find solution for other (all) modes.

Measurements of  (e + e -  hadrons) and BF for  (3770)  D 0 D 0, D + D -, DD and  (3770)  non DD

 (3770) BES was the first to report the non DD Decay of  (3770) Before BES-II one knows the decays BES-II established the transition at level ! PLB605(2005)63-71 BF((  (3770)  J/     ) = (0.34  0.14  0.09)%  ((  (3770)  J/     ) = (80  33  23)KeV Now study non-DD decay by R measurement and energy peak scan

Measurement of R R is one of the most fundamental quantities in particle physics, which counts directly the charges, the flavors and the colors of quarks involved. pQCD calculates the R ratioExperimentally, one measures : # of hadronic : Luminosity : Eff. events : radiative correction factor

E CM [GeV] σ obs had σ Born had R Including J/ψ and ψ ’ contribution Including the contribution from high order processes (preliminary !) BES contribution paper to Lepton-photon 2005 see below Obtaining by fitting to the R values measured by BES in the range from 2.0 to 3.0 GeV

(preliminary !)

Taking the R for light hadron production to be a constant, then We obtain obtained based on PDG04  (3770) resonance parameters PLB 603(2004)130 My calculation It is consistent with determined with 

Observed cross sections for DD-bar production at GeV PLB 603(2004) 130  of GeV From Monte Carlo PDG04 Br

Preliminary ! An absolute measurement Contribution paper to LP05 Checked by double tagging method (33pb -1 data)

Assuming that decay exclusively into  (3770) Radiative correction PR D62 (2000) Radiative correction factor Obtained from analysis of R  Determination of branching fractions with and Some systematic uncertainties can be canceled out Radiative correction factor obtained based on new  (3770) resonance parameters measured by BES-II.

These results are preliminary !  Results of branching fractions Uncertainties due to luminosity, trigger, radiative corrections are canceled out.

Measurement of branching fractions for and  (3770) production The data were collected at 49 energy points from 3.66 to 3.89 GeV, which begin from off-resonance, cover  (2S),  (3770) and stop at DD* threshold.  Cross section scan experiment Separated beam collision data at 3 energy points were collected to study beam associated background. Some J/ ,  (2S) data were also taken to calibrate BEPC energy and determine  trg

(Kuraev and Fadin)  Observed cross section Hadron efficiency vs C.M. energy

When scan over GeV Just before the scan experiment Mass [MeV] PDG04 BEPC BEPC energy calibration E BEPC is the energy of BEPC set in the experiment, E true is the true energy

 (3770) Resonance parameters To get right resonance parameters, the two resonance production and decays should be considered simultaneously. In this way the “correct” QED background ( ) can be determined correctly ! BES-II Preliminary !

(preliminary !) Experiment MARK-I DELCO MARK-II PDG04 BES-II Comparison of  (3770) Resonance Parameters

Comparison of  (3686) Resonance Parameters experiment This measurement (preliminary !) BES-II published (PLB550(2002)24) PDG2004 Using a constant for vacuum polarization correction The measured partial width is consistent with PDG04 partial width of  (3686).

Line shape of the cross sections for hadron and DD-bar production Inclusive hadrons

[GeV] Red: inclusive had. Black: D0D0-bar Blue: D+D-

 Branching fractions where the first error is statistical and second systematic, which arises from the un-canceled systematic uncertainties in hadron cross sections (~3.4 %), neutral DD-bar cross sections (~6.2 %) and charged DD-bar cross sections (~8.6 %). These results are preliminary ! Obtained from fitting to the inclusive hadron and the DD-bar production cross sections simultaneously. Considered the correlation between the two branching fractions for the two modes

Summary Lots of new results from J/ ,  (2S),  CJ and  (3770) decays. X(1835) observed in J/    +(  ’  ) decays, could be the same state observed in J/    pp, could be a baryonium. Other threshold enhancements. Parameters of  and  are given. Vector charmonia (J/ ,  ’, and  ’’) hadronic decays are studied extensively and simultaneously to understand charmonium decay dynamics. “  puzzle” remains a puzzle. Inclusive and exclusive  (3770) non DD decay reported.

Status of BEPCII/BESIII  Two ring machine, design luminosity 3  10  cm - 2 s -1.  Detector design: SC magnet 1 tesla field; small cell MDC; CsI crystal calorimeter; Time of flight ~100ps; RPC as muon detector 9 layers.  Schedule: Summer of 2006, machine to be commissioned.  Detector moved to beam line early of 2007, and started to commission detector with machine together.  Expect to have test run in 2007.

Thanks 谢谢

BES, PRL91, (2003) Old fit w/o FSI New fit with FSI

Gounaris-Sakurai’s parametrization C is incoherent background term  ’   +  -  0 PWA

A prediction of  ’’ charmless decays Wang, Mo and Yuan, PRD70, (2004) Prediction on ψ(3770) charmless decay branching fraction:  16% (or 3.8MeV) S- and D-wave mixing Average enhancement factor Non-zero phase btwn matrix elements Phase=0 B(  (2S)  ggg)/B(J/   ggg) = 0.26 ± 0.04

0 ++ states: f 0 (980), f 0 (1370), f 0 (1500), f 0 (1710), f 0 (1790) PDG 2004 values: f 0 (980): M = 980  10 MeV,  = 40 – 100 MeV  , KK f 0 (1370): M = 1200 – 1500 MeV,  = 200 – 500 MeV  2 , 4 , KK … f 0 (1500): M = 1507  5 MeV,  = 109  7 MeV  2 , 4 , ,  ’, KK … f 0 (1710): M = 1714  5 MeV,  = 140  10 MeV  2 , 2K, 4 , ,  ’ …

Important parameters from PWA fit: Large coupling with KK indicates big strange quark component in f 0 (980) f 0 (980) Phys. Lett. B 607 (2005) 243

There has been debate whether f 0 (1370) exists or not. f 0 (1370) clearly seen in J/   , but not seen in J/   . PWA 0 ++ components f 0 (1370) NO f 0 (1370) f 0 (1370) Phys. Lett. B 607 (2005) 243

Clear f 0 (1710) peak in J/    KK. No f 0 (1710) observed in J/    ! f 0 (1710) NO f 0 (1710) Phys. Lett. B 603 (2004) 138

PWA analysis shows one scalar in 1.7 GeV region. Phys. Rev. D 68 (2003)

A clear peak around 1790 MeV is observed in J/   . No evident peak in J/    KK. If f 0 (1790) were the same as f 0 (1710), we would have: Inconsistent with what we observed in J/   ,  KK New f 0 (1790)?? f 0 (1790) ?  f 0 (1790) is a new scalar ??

Scalars in J/    Two scalars in J/    : –One is around 1470 MeV, may be f 0 (1500)? –The other is around 1765 MeV, is it f 0 (1790) or f 0 (1710) or a mixture of f 0 (1710) and f 0 (1790)? BES II Preliminary

Excited baryon states  Probe the internal structure of light quark baryons  Search for missing baryons predicted by quark model

J/  decays processesbranching ratios(10 -3 )N* decays 2.0       0.3 relatively large branching ratios

Pure isospin 1/2 Feynman diagram of the production of For and, and systems are limited to be pure isospin 1/2.

The evidence of 2 new N* peaks Missing mass spectrum (GeV/c 2 ) N*(1440)? N*(1520) N*(1535) N*(1650) N*(1675) N*(1680) ?

Fitting formula : momentum of : proton momentum in M x frame ► Possible new N* resonance ► preliminary PWA shows: this N* favors 3/2+ hep-ex/

Measurements of J/  and  c decays

First observation of J/    f 2 (1270)f 2 (1270)  4  M  (GeV/c 2 ) signal J/  anything MC BG fit with: BW:  0 (770), f 2 (1270) BG: 2nd order polynomial + f 2  P. R. D. 70 (2004)

Measurement of J/  decays to Vector + Pseudoscalar --- channels measured:

The measured branching ratios Phys. Rev. D 71 (2005)

First measurements of J/   2(  +  - )  and 3(  +  - )  J/   2(  +  - )  J/   3(  +  - )  Phys. Lett. B 610 (2005) 192 M(  ) GeV 

Measurement of J/  decays to  + Pseudoscalar ---

preliminary

First observation of  c  K + K - 2(  +  - ) and 3(  +  - ) Ndata= significance: at 90% C.L.

Ndata= significance: Submitted to Phys. Lett. B (hep-ex/ )

In SM, lepton flavor symmetries are conserved. neutrinos having mass and flavor oscillation indicates the existence of LVF J/   e ,  and e  are LVF processes Search for Lepton flavor violation (LFV ) Phys. Lett. B 555 (2003) 174 Phys. Lett. B 598 (2004) 172 Decay modesN signal N background Upper limit J/  →e   J/  →e   J/  →   10 -6

Events Recorded by BESII Cosmic-ray and beam associated background The distributions of the averaged Z of events could be estimated based on cross sections, luminosity and acceptance Radiative correction could remove the effects of high order processes from the cross section, and gives The events observed in the experiment

MC generator & simulation Full energy range ISR Generator Nch KNO φ Thrust Oblateness cosθ Sphericity Aplanarity Jet axis cosθ x η Y PtPt Density [nb/GeV]

ISR corrections Kuraev & Fadin the electron equivalent radiator thickness Effective c.m. energy Moninal c.m. energy

Vacuum polarization change the photon propagator results in Vacuum polarization correction

Integrated luminosities Monte Carlo  Luminosities were measured by using large angle Bhabha scattering About 5.4 pb -1 of data were collected for the experiment (for hadron events) Developed a inclusive hadronic event generator with high order ISR corrections to simulate the hadronic event production (including Lorentz boost due to initial state photon emission) in the full energy region  Using more cross section scan data to reconstruct DD-bar events

Distributions of invariant masses of  Energy dependent cross sections DD-bar production combinations at different c.m. energies

Inclusive hadrons Observed cross section for hadron production [nb] Observed cross sections

Fitting the observed inclusive hadron and DD-bar production cross sections to the theoretical cross sections, one obtains the branching fractions  Fit to the observed cross sections momentum of D at peak momentum of D threshold function  (3770) total width

Independent hadron and DD-bar data sample Branching fraction for the singly tagged D channel These relations remove those hadronic events which also appear in the DD-bar samples, so that the inclusive hadronic and DD-bar samples are independent.

Source Uncertainty in R [%] (around GeV) Uncertainty in R [%] (at GeV) luminosity Had. Evt. Selection MC Generator (Monte Carlo Modeling) ISR & |1-Π(s)| -2 Ψ(3770) parameters Trigger ~2.1 ~2.8 ~2.0 ~1.5 ~0.5 ~2.1 ~2.8 ~2.0 ~1.5 ~2.7 ~0.5 Total ~4.3 ~5.1 Systematic uncertainty in the measured R values The detection efficiency for hadronic events is determined via a Monte Carlo simulation using JETSET74 event generator. Parameters in the generator are tuned using a hadronic event sample collected near 3.55 GeV (it is the same as that used in BES R measurements. PRL 84(2000) 594) and PRL 10(2002)

Source of systematic uncertainties in the measured branching fractions for  (3770)  DD-bar

Estimation of the un-canceled systematic errors MC Modeling ~ 2.0% Hadron selection ~ 2.8% Total~ 3.4% PID ~1.5% Tracking & K.F. ~4% BCK shape ~3% MC statistic ~0.6% BF ~3.2% (neutral mode) ~6.5% [charged mode] Total ~6.2% (neutral) ~8.6% (charge) The uncertainties due to luminosity, trigger and radiative corrections are canceled in measurements of the branching fractions.

SUMMARY BES measured R at GeV and around GeV with average uncertainties of BES measured the energy dependent DD-bar cross sections, and the cross section at GeV . (preliminary !) Singly tagged D analysis Doubly tagged D analysis Obtained from fitting to  (3686) and  (3770)

BES measured the branching fractions for inclusive non-DD-bar decays of  (3770) using two different data sample and two different methods . (preliminary !) SUMMARY These are first measurements. Determined from analysis of R values and DD-bar cross sections Obtained from fitting to the inclusive hadron and the DD-bar production cross sections simultaneously.