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