Physics at BES Shan JIN (for the BESIII Collaboration) Institute of High Energy Physics (IHEP) [email protected] USTRON09, Poland September 12-16, 2009 Outline Introduction of BES experiments and Physics at BES Highlights at BESII Status of BESIII and preliminary results Future prospects at BESIII Conclusion Beijing Electron Positron Collider (BEPC) at IHEP BESI: 1989-1998 BESII: 1999-2004 L ~ 51030 /cmcm2s at J/cm Ebeam~ 1 2.5 GeV
Linac Storage Ring BSRF BES BESIII: 2008Physics run started in March, 2009. 100M (2S) and 200M J/ events collected 3 BEPCII: L reached 31032/cm2s at (3770) designed L: 1033/cm2s BEPC 240.4 2-5GeVGeV
202 Why tau-charm physics in the past in the era of LHC is interesting in the future Abundant resonances(J/ family, huge Xsections) Tau-charm threshold production(in pairs tagging backg round free, no fragmentation, kinematic constrains, quantu m coherence,) Charm quark: A bridge between pQCD and non-pQCD A ruler for LQCD J/decayGluon rich environment Flavor physics Complementary to LHC: virtual vs real A broad spectrum & efficient machine: e e
u d c s t b What (highlight) physics interested us Light hadron spectroscopy Full spectra: normal & exotic hadrons QCD How quarks form a hadron ? non-pQCD
Charm physics CKM matrix elements SM and beyond D D mixing and CPV SM and beyond Charmonium physics hep-ex/0809.1869 Spectroscopy and transition pQCD & non-pQCD New states above open charm thresholds exotic hadro ns ? pQCD: puzzle a probe to non-pQCD or ? Tau physics and QCD Precision measurement of the tau mass and R value Search for rare and forbidden decays Precision test of SM and search for new physics Light hadron spectroscopy Motivation:
Establish spectrum of light hadrons Search for non-conventional hadron s Understand how hadrons are forme d Study chiral symmetry in QCD Why at a tau-charm collider ? Gluon rich Larger phase space than at higher e nergies Clean environment, JPC filter Many results in BESII: ~ 50 publications Much more from BESIII: 100 statistics, 10 resolution Glueball spectrum from LQCD Y. Chen et al., PRD 73 (2006) 014516 Multi-quark State, Glueball and Hybrid
Hadrons consist of 2 or 3 quarks Naive Quark Model Meson q q Baryon q q q New forms of hadrons: Multi-quark states Number of quarks > 4 Hybrids Glueballs
qqg qqqg gg ggg ow quarks/gluons form a hadron is far from being well understo Multi-quark states, glueballs and hybrids have bee n searched for experimentally for a very long time, but none is established. However, the effort has never been stopped, espec ially, during the past three years, a lot of surprisin g experimental evidences showed the existence of hadrons that cannot (easily) be explained in the co nventional quark model. Searches for new forms of hadrons are of special importance at BES since J/psi deca ys are believed as an ideal factory to sear ch and to study exotic hadrons. Charmonium physics What to study ? Production, decays, tr
ansition, spectrum For what ? A lab for pQCD and n on-pQCD Calibrate LQCD How quarks form a ha dron ? Why at a tau-charm c ollider ? A clean environment Tagging possible Abundantly produced Examples of interesting/long standing issues: puzzle Missing states ? Mixing states ? New states above open charm thre.(X,Y,Z,) Highlights at BESII
BESII VC: xy = 100 m TOF: MDC: xy = 220 m BSC: dE/dx= 8.5 % p/p=1.7%(1+pp2) T = 180 ps E/E= 22 % = 7.9 mr z = 2.3 cm counter: r= 3 cm z = 5.5 cm B field: 0.4 T World J/ and (2S) Samples (10S) Samples (106) J/
(2S) Samples (10S) 60 14 50 12 10 40 8 30 6 20 4
10 2 0 0 M arkIII DM 2 BESI B E S II MKI MKII MKIII
CBAL BESI BESII Observation of an anomalous enhancement near the threshold of pp mass spectrum at BES II BES II J/pp acceptance weighted BW M=1859 +3 +5 MeV/c2 10 25 < 30 MeV/c2 (90% CL) 2/dof=56/56 0
Phys. Rev. Lett. 91, 022001 (2003) 3-body phase space 0.1 0.2 M(pp)-2mp (GeV) acceptance 0.3 At BESII: Observation of X(1835) in J Statistical Significance 7.7 BES II BESII J m 1833.7 6.1 2.7 MeV 67.7 20.3 7.7 MeV
The same origin as ppbar mass threshold? a ppbar bound state? Phys. Rev. Lett. 95, 262001 (2005) The +- mass spectrum for decaying into +- and Observation of an anomalous enhancement near the threshold of p mass spectrum at BES II BES II J / pK 3-body phase space Phys. Rev. Lett. 93, 112002 (2004) For a S-wave BW fit: M = 2075 12 5 MeV = 90 35 9 MeV Observation of mass threshold structure X(1810) in J/cm at BESII
BES II M2() X(1810) M2() 2 M 1812 19 18 MeV/c 26 105 20 28 MeV/c 2 Background M()
Jpc favors 0++ Phys. Rev. Lett., 96 (2006) 162002 Possible theoretical interpretations: glueball, hybrid, multiquark? Very broad 1- - resonance X(1580) observed in K+K- mass spectrum in J/cm K+K-0 at BESII BES II X (1580 ) 0 X (1580) Background M
i i 49 98 22 64 2 (1576 55 ) ( 818 ) MeV/c 91 23 133 2 2 J PC 1 Phys. Rev. Lett. 97 (2006) 142002 So far the only reasonable interpretation is a multiquark state due to its very broad width
at BES BES II observed in J/cm +-. BES II M Pole position from PWA: (541 39) i ( 252 42) MeV at BESII BES II BESII firmly established neutral in J/cm K*0K KK in 2006: PWA result Pole position: 48 2 (841 30 81 73 ) i (309 45 72 ) MeV/c
Observation of charged at BESII New result: Charged observed at BESII in J / K * K s K 0 Different parameterizations are tried in PWA. BESII Preliminary The pole position: 64 2 (841 5114 28 ) i ( 288 101 30 ) MeV/c K*(1410), K*(1430) consistent with neutral M(K0) GeV/c2
QCD studies at low energies Understand where exactly pQCD becomes invalid Precision measurement of s running Precision measurement of R input to ? Related to QED (s), prediction of higgs mass and g-2S) Samples (10 A new measurement at BESII on R Precision at ~ 3.5% BESIII: < 2% A new determination of s(s): s(M2Z) = 0.1170.012 Ecm(Ge V) L(pb-1) R 2.60
1.222 2.180.020.08 3.07 2.291 2.130.020.07 3.65 6.485 2.140.010.07 s(S) In good agreement with previous results Phys.Lett.B677,(2009)239
Resonance parameter fit Heavy charmonia parameters were fitted with the data betwee n 3.75.0GeV, taking into accounts the phase angles, interfere nce, energy-dependent width, etc. Probability =31.8% Phys. Lett. B660, (2008)315 Anomalous (3770) lineshape Black dots: data Red dots: data subtracting J/and continuum contribution Green line: fit with one (3770) hypothesis; Red line: fit with two cross section Check all lines
!!! Blue line: fit with two amplitude PRL101 (2008) 102004 quantity Two AM Two AM One AM Y(3770)+G(3900) 2 125/cm103 112/cm102
3718.104.22.168 3781.01.30.5 3943.0(Fixed) Status of BESIII and preliminary results BEPC II Storage ring: Large angle, double-ring RF SR RF Beam energy: 1.0-2 .3GeV Luminosity: 11033 cm-2s-1 Optimum energy:
1.89 GeV Energy spread: 5.16 10-4 No. of bunches: 93 Bunch length: 1.5 cm Total current: 0.91 A BESIII detector IP BESIII Commissioning and data taking milestones Mar. 2008: first full cosmic-ray event April 30, 2008: Move the BESIII to IP July 18, 2008: First e+e- collision event in BESIII Nov. 2008: ~ 14M (2S) events collected April 14, 2009 ~100M (2S) events collected May 30, 2009 42 pb-1 at continuum collected July 28, 2009 ~200M J/ events collected
2/cmd.o.f = 39.5/cm41.0 Select E1-photon to tag hc A fit of D-Gaussian signal+ sideband bkg. yield: M(hc)Inc = 3522.214.171.124 MeV Systematic errors under study (hc)Inc = 0.890.570.23 MeV (First measurement) Br(hc )Br(hcc )Inc =(4.690.48(stat)) 10-4 ((hc) floated) =(4.690.29(stat)) 10-4 ((hc) fixed at (c1)) CLEOs results (arXiv 0805.4599v1) : M(hc)Inc= 3525.350.230.15 MeV Br(hc )Br(hchc )Inc =(4.220.440.52) 10-4 ((hc) fixed at (c1) ~0.9MeV CLEOc: Combined E1-photon-tagged spectrum and exclusive analysis M(hc)avg= 3525.280.190.12 MeV (arXiv 0805.4599v1)
Br(hc )Br(hchc )avg =(4.190.320.45) 10-4 Observation of hc : Inclusive (2S)0hc background subtracted BESIII preliminary Inclusive recoil mass spectrum BESIII preliminary Select inclusive 0 Systematic errors A fit of D-Gaussian signal + 4th Poly. bkg yield under study N(hc) = 9233935, 2/cmd.o.f = 38.8/cm38.0 Combined inclusive and E1-photon-tagged spectrum Br(hc ) =(8.421.29(stat)) 10-4 (First measurement) Br(hcc) =(55.76.3(stat))% (First measurement) 31
Study of (2S) 00 , , 0 Interesting channels for glueball searches Based on 110M (2S) BK study from 100M inclusive MC sample and 42pb-1 continuum sample Unbinned Maximum Likelihood fit: Signal: PDF from MC signal Background: 2nd order Poly. Nc0 16645175 Nc2 414982 c0 c2 2S) BESIII
Confirmation of the BESII observation: pp threshold enhancement in J/cmdecays BES II J / pp BES III preliminary (2S) J/ J / pp 0.3 M(pp)-2S) Samples (10mp (GeV) M=1859+3 +5 MeV/c2 10 25 < 30 MeV/c2 (90% CL) PRL 91 (2003) 022001
M=1864.6 5.3MeV/c2 < 33 MeV/c2 (90% CL) Confirmation of BESII observation: threshold enhancement in decays No pp BES II pp BES III preliminary pp Mpp (GeV) No significant narrow enhancement near threshold (~2 if fitted with X(1860)) PRL 99 (2007) 011802 No enhancement in decays In fact, no enhancement in ,(1S) decays and
in the process of J/ ppbar show that FSI u nlikely . Study of cJ VV, V= Test QCD-based theory at cJ decays Puzzles for c0 VV: no helicity suppress BESII results: c1 highly suppressed owing to sy mmetry of identical particles c1 OZI doubly suppressed BR(103 ) c0 c2
0.930.20 1.50.3 2.30.7 2.00.7 Backgrounds from sideband & 100M MC events c0 c1 c2 Clear c1 signal to be understood
c2 BESIII preliminary c0 m KK f or c0 K K m KK f or c1 K K m KK f or c2 K K c1 First observation of c1 m K K (GeV) c0 BESIII preliminary c1
c2 0 m (GeV) Background from sideband & 100M MC events Clear signal from c1 (K+K-) Future prospects at BESIII Event statistics at BESIII Physics Channel Energy (GeV) Luminosity (1033 cm2S) Samples (10s 1) Events/year
0.6 2S) Samples (10.0106 *CLEO took 10 nb D production cross section while we took 5 nb Precision measurement of CKM: Branching rations of charm mesons Vcd /cmVcs: Leptonic and semi-leptonic decays Vcb: Hadronic decays Vtd /cmVts: fD and fDs from Leptonic decays Vub: Form factors of semi-leptonic decays Unitarity Test of CKM matrix
CKM matrix elements measurement Current BESIII Vub 2S) Samples (105% 5% Vcd 7% 1% Vcs 16% 1%
Vcb 5% 3% Vtd 36% 5% Vts 39% 5% Precision test of SM and Search for new Physics DDbar mixing
DDbar mixing in SM ~ 10 3 - 10 10 DDbar mixing sensitive to new physics Our sensitivity : ~ 10-4 Lepton universality CP violation Rare decays FCNC, Lepton no. violation QCD and hadron production R-value measurement pQCD and non-pQCD boundary Measurement of s at low energies Hadron production at J/, and continium Multiplicity and other topology of hadron eve nt BEC, correlations, form factors, resonance, etc.
R-value measurement Error on R (5)had (MZ2) 5.9% 0.02761 0.00036 3% 0.02761 0.00030 2% 0.02761 0.00029 Errors on R will be reduced to 2% from current 6% Prospects of glueball searches
at BESIII J/cm decays are an ideal factory to search for and study light exotic hadrons: The production cross section of J/cm is high. The production BR of hadrons in J/cm decays are o ne order higher than decays (12% rule). The phase space to 1-3 GeV hadrons in J/cm decay s are larger than decays. Exotic hadrons are naively expected to have large r or similar production BR to conventional hadron s in J/cm decays. Clean background environment compared with ha dron collision experiments, e.g., JP, I filter. One Important Physics Goal of BESIII With 1010 J/cmpsi events, we hope to answer: Whether glueballs exist or not? Naively, we estimate in each exclusive decay mode: BR( J / G ) BR(G hh) ~ 10 5
10 3 10 2 If the eff. is about 20%, we would have 20000 events for each decay mode we should observe a relative narrow (width: 50~200 MeV) glueball if it exists. Difficulties (I) Theoretically: Predictions on glueball masses from LQCD may be unreliable due to quench approximation. No predictions on the widths so far (even the order). No prediction on the production rate (J/cm G). Mix with qqbar mesons or even with 4q, qqg meson s? (dirty?) What is the mixing mechanism from the fi rst principle? Difficulties (II) Experimentally: Data sample is not big enough (it is not a problem fo
r BESIII) No good way modeling background at low energy, i n many cases we have to study bck via data. Interferences among mesons make the mass/cmDalitz plots very complicated PWA is crucial for hadron spectroscopy at BESIII But PWA may face many uncertainties. 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/cmpsi radiative decays
Mixing mechanism 2++ glueball candidates Lattice QCD predicts the 2++ glueball mass in th e range of 2.2~2.4 GeV (2230) was a candidate of 2++ glueball: It was first observed at MARKIII in J/cmKK It was observed at BES I in J/cmKK, , ppbar It was not observed at DM2. BES-I (2230) Result (2230) The situation at BESII J / K K J / K s0 K s0 The mass plots shows no evi dent (2230) peaks in J/cmK K, , ppbar, which is clearl
y different from BESI. Careful PWA is needed to dra w firm conclusion on its exist ence since it may be still need ed in the PWA although no cle ar mass peak observed. Difficult to draw firm conclusi on at present. We hope to giv e a final answer at BESIII on (2230) . Other 2++ glueball candidates No other obvious good candidates have been o bserved in J/cmpsi radiative decays in the mass r ange predicted by LQCD. What does it mean: LQCD prediction might not be very reliable, or BR(J/cm G)xBR(Ghh) is small ( <10-4 ) so that we dont have the sensitivity to observe it ( quite possi ble ), or, The width of a glueball is very large ( ~1GeV, E.Klep mt ).
Where to search for the 0-+ glueball? Lattice QCD predicts the 0-+ glueball mass in th e range of 2.3~2.6 GeV. (1440) and X(1835) were suggested being pos sible candidates, but their masses are much lo wer than LQCD predictions. No 0-+ glueball candidate observed in the m ass range 2.3~2.6 GeV X (1835) No evidence for a relativ ely narrow state ( 100 ~ 2 00 MeV width ) above 2G eV in J / KK , , K * K *, , ' ... Again:
M ' LQCD reliable? Production rate could be v ery low. Glueball width could be ve ry large. Summary Physics at BES (tau-charm threshold) are very rich. There are many exciting discoveries at BESII. BESIII is operational since 2S) Samples (10008: Detector performance excellent, ready for physics High quality data samples in hand Analysis in progress, papers in a few months With much more statistics of data sample and much improv ed detectors at BESIII, more exciting discoveries can be ex pected. Some fundamental questions, such as the existence of glu eballs, might be answered at BESIII with close collaboratio n with theorists.
Thanks! Prospects: a bright future BESIII will resume data taking after summer shutdo wn, ~5 months until next summer Possible plans: 500-1000 M J/events (2S) Samples (10-4 months) 500-1000 M (2S) Samples (10s) (2S) Samples (10-4 months) To be decided in Nov. -1 2S) Samples (10fb (3770) (4 months) Lineshape scan of (3770) (2S) Samples (10 weeks) Future charm programs LHCb at CERN soon
BELLE II at SuperB factory ~ 2S) Samples (10014 PANDA at GSI ~ 2S) Samples (10015 New programs under discussion: Frascati(super flavor factory) L ~ 1035-36 cm-2S) Samples (10s-1 Novosibirsk(super tau-charm factory) Expand the life time of Fermilab tau-charm colliders to TeV fixed target exp. ? Ppbar exp. ? > 50 years !
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