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Overview of BES physics
Yifang Wang
Institute of High Energy Physics
BES experiments• BESI Stared in late 80’s
• BESII Stared in late 90’s
• BESIII is starting now
Data BESII
J/ 58 M
’ 14 M
’’ 33 pb-1
Continuum 6.4 pb-1 (s=3.65 GeV)
Performance
p/p 1.7%/1+p2
E/E 22% /E
PartID dE/dx+TOF
Coverage 80%
~ 150 papers on PRL, PRD, PLB
Rich physics at tau-charm
BESII
R value and excited states
Significantly improved data quality in 2.0-5.0 GeV region,
From PDG
Before BES
After BESAfter BES
Before BES
An enhancement near the ppbar
threshold
J/pp
M(pp)-2mp (GeV/c2)0 0.2
Phys. Rev. Lett., 91 (2003) 022001
Observation of X(1835)
Phys. Rev. Lett. Dec.31, 2005
7.7
2
2
MeV/c 7.73.207.67
MeV/c 7.21.67.1833
54264
M
Nobs
)1580(X
Background
0
)890(*K
)1580(X
)1410(*K
Observation of a broad resonance in J/ K+K- 0
Phys. Rev. Lett. 97 (2006) 142002
PWA analysis and parity conservation considerations yield: 1PCJ
232116712
98499155 / )(409 )1576( cMeVi
47.26.3
0 10)6.05.8()()/(
KKXBrXJBr
X pole position:
Too many 1--, Width is much broader than other mesons; multiquark state ?
Observation of N(2050)
../ ccnpJ
N*(1440)?
N*(1520)
N*(1535)N*(1650)
N*(1675)
N*(1680)
?
Phys. Rev. Lett. 97 ( 2006 ) 062001
N(2050): 1/2+ 或 3/2+ +15 2 2-30M = 2065 3 MeV/c =175 12 40MeV/c
N(1440):
22 MeV/c 5026179 ,MeV/c 1661358 M
Observation of an anomalous enhancement near the threshold of mass spectrump
BES II pKJ /
3-body phase space
For a S-wave BW fit: M = 2075 12 5 MeV Γ = 90 35 9 MeV
Phys. Rev. Lett. 93, 112002 (2004)
BEPC upgrade: BEPCII Unique physics opportunities
• In a regime of transition between pQCD and non-pQCD
• Can provide calibrations and tests of LQCD• Rich spectra of light hadrons for Quark model test
and for searches of new hadrons• Rich gluonic matter production for QCD test • Near the production threshold of tau-charm: good
for quantum correlation constraints• Complementary to LHC experiments
Physics at BEPCII/BESIII• Precision measurement of CKM matrix
elements
• Precision test of Standard Model
• Light hadron spectroscopy
• Charmonium physics
• Search for new physics/new particles
Physics
Channel
Energy
(GeV)
Luminosity
(1033 cm–2s –1)
Events/year
J/ 3.097 0.6 1.0×1010
3.67 1.0 1.2×107
’ 3.686 1.0 3.0 ×109
D* 3.77 1.0 2.5×107
Ds 4.03 0.6 1.0×106
Ds 4.14 0.6 2.0×106
hep-ex/0809.1869
Light hadron spectroscopy• Baryon spectroscopy• Charmonium spectroscopy• Glueball searches• Search for non-qqbar states
1010 J/ events is probably
enough to pin down most
of problems of light hadron
spectroscopy
Spectrum of glueballs from LQCD
Precision measurement of CKM---- Branching rations of charm mesons
• Vcd /Vcs: Leptonic and semi-leptonic decays
• Vcb: Hadronic decays
• Vtd /Vts: fD and fDs from Leptonic decays
• Vub: Form factors of semi-leptonic decays
• Unitarity Test of CKM matrixCurrent BESIII
Vub 25% 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
BEPC II Storage ringBEPC II Storage ring:: Large angle, double-ring
RFRF SR
IP
22 m
rad
2. 5m8ns
1. 5cm
0.1cm
Beam energy: 1-2 GeVLuminosity: 1×1033 cm-2s-1
Optimum energy: 1.89 GeVEnergy spread: 5.16 ×10-4
No. of bunches: 93Bunch length: 1.5 cmTotal current: 0.91 ASR mode: 0.25A @ 2.5 GeV
Commissioning milestones Oct. 25-31, 2007: accumulation of electron/positron beams Nov. 18, 2007: first e+e- collision without BESIII detectorMar. 2008: Collision 500 mA × 500 mA, Lumi.: 1 ×1032 cm-2s-1
April 30,2008: Move BESIII to IPJuly 18, 2008: First event in BESIII
The BESIII Detector
Be beam pipe
SC magnet, 1TMagnet yoke
MDC, 130 m
CsI(Tl) calorimeter, 2.5 %@1 GeV
TOF, 90ps
RPC
Japan (1)Tokyo University
USA (6)
Univ. of Hawaii, Univ. of Washington,Univ. of Minisolta,
Carnegie Mellon Univ., RPI, Rochester Uni.,
China (23)IHEP, CCAST,
Univ. of Sci. and Tech. of ChinaShandong Univ., Zhejiang Univ.
Huazhong Normal Univ., Wuhan Univ.Zhengzhou Univ., Henan Normal Univ.
Peking Univ., Tsinghua Univ. ,Zhongshan Univ.,Nankai Univ.
Shanxi Univ., Sichuan UnivHunan Univ., Liaoning Univ.
Nanjing Univ., Nanjing Normal Univ.Guangxi Normal Univ., Guangxi Univ.Hong Univ., Hong Kong Chinese Univ.
Europe (5)
GSI, Germany
University of Bochum, Germany
University of Giessen, Germany
JINR, Dubna, Russia
Univ. of Torino, Italy
Drift chamber• To measure the momentum of charged particles by its bended
curvature in a magnetic field• 7000 Signal wires: 25 m gold-plated tungsten
• 22000 Field wires: 110 m Al
• Gas: He + C3H8 (60/40)
• Momentum resolution@1GeV:
%37.0%32.0 t
P
Pt
Babar: ~ 110 m
BELLE: ~ 130 m
CLEO: ~ 110 m
BESIII: ~ 130 m
BESIII CsI(Tl) crystal calorimeter• To measure the energy of electromagnetic particles
• Barrel: 5280 crystals , Endcap: 960 crystals
• Crystal: (5.2x 5.2 – 6.4 x 6.4) x 28cm3
• Readout: 13000 Photodiodes, 1cm2cm,
• Energy range : 20MeV – 2 GeV
• position resolution: 6 mm @ 1GeV
• Tiled angle: theta ~ 1-3o, phi ~ 1.5o
Babar: 2.67% @1GeV
BELLE: 2.2% @1GeV
CLEO: 2.2% @1GeV
BESIII: 2.5%@1GeV
PID: TOF system• Barrel: 2*88 BC408, 2.4 m long, 5cm thick
• Endcap : 2* 48 BC 408
• PMT: Hamamatzu R5942探测器 长
(cm)本征分辨
BESIII 240 90 ps
CLEOII 280 139 ps
OBELIX 300 170 ps
BELLE 255 90~100 ps
CDFII 279 100 ps
HARP 180-250 160 ps
system : RPC• 9 layer, 2000 m2
• Special bakelite plate w/o lineseed oil
• 4cm strips, 10000 channels
• Noise less than 0.1 Hz/cm2
First cosmic-ray event
trigger+DAQ + detector(MDC + EMC +TOF+MUON )
Trigger condition : cosmic-rays
First collision event on July 19, 2008
13 M ’ events collected in 2008
MDC calibrationReso. 128 mEff.: ~ 98%
σP=12.0MeV/c=0.64%Reso.
dE/dx resolutiondE/dx reso.: 5.80%
K p
TOF calibration
TOF Barrel: 103 psDesign : 100 ps
Endcap TOF : 125psDesign : 110 ps
EMC calibration Barrel energy resolution energy deposit for e+e-
energy resolution for Bhabha events Position resolution for Bhabha
4.4 mm
Spatial resolution
MUON ChamberEfficiency
Single counting rate
Data Taking in 2009
• March – April: ’ – ~ 100 M events = 4*CLEOc = 7*BESII
• April- June: J/ – ~ 500 M events = 8*BESII
• June : a few days at 3.0 & 3.65 GeV• After summer:
– Possibly ” scan if beam energy is stable and/or beam energy monitor is in place
Integral luminosity accumulated
Corresponding to ~100M ’ events
Peak luminosity in 2009
31
Physics at ’• Spin-singlets
– hc (resonance parameters, production & decays)
c (resonance parameters, …)
c’ (resonance parameters, production & decays)
’ hadronic decays – VP: , K*K, … (Dalitz analysis)
– PP: +-, K+K-, KSKL (benefit from good momentum resolution and part ID)
• c decays
– New states
’ energy scan
Beam energy spread: 1.4 MeV
Some physics signals
33
0 signal
(2S) cJ
signal
signal
2009-04-18 BESIII Software/Physics Workshop 34
’ l+l- : signals of cJ, 0 and
0
c1 c2
Inclusive Spectrum
c2
c1
co
c1,2 J/
c
confirm the X(1860) in J/pp
confirm the X(1835) in J/’+-.
check J/ ’00 ?
confirm X(1810) in J/
confirm X(1580), X(2075), Y(2175) …
study inclusive photon spectrum
study J/, ’, ’’ and 00
provide c sample (Br(J/ c) 1.3%)
more J/ and c decay modes
physics at J/
,' ,'/J
BESII data 58M J/ BESIII MC 58M J/
> 10 6
Confirm X(1835) at BESIII
,' ,'/J
5.1
> 10
2 weeks data taking at BESIII 2 years data taking at BESII
Confirm ppbar threshold enhancement at BESIII ( 58M J/ )
Y(2175) in J/f0(980) at BESIII
BESII data 58M J/ BESIII MC 58M J/12 MeV 5.5
4 MeV > 10
A lineshape scan of (3770)L
pb
-1
PRL101 (2008) 102004
BES-II
“fast energy calibration45 d, ~ 90 pb-1
30 energy points 30 energy points 9 energy points(may be a little bite more)
Summary • physics program at tau-charm is very rich• The BESIII detector is successfully constructed • Computing facility and offline software are ready for
large scale data production and physics analysis• A total of 13 M psi’ events are collected in 2008.
Detector calibration are performed, showing that– All detector components work well and stable
– Detector resolution met design specifications
• A total of 100 M psi’ events are collected this year, and great physics results are expected to come soon