1

BEPCII/BESIII Frederick A. HarrisUniversity of Hawaii

QWG MeetingSept. 20-22, 2003Fermilab

Representing:

2

The Beijing Electron Positron ColliderL ~ ~51030 /cm2s at J/ peak Ecm~2-5 GeV

A unique e+e- machine in the -charm energy region since 1989.

3

On Feb. 10, 2003, the Chinese government, the state council, approved officially the BEPCII/BESIII upgrade project

4

BEPC II Storage ringBEPC II Storage ring:: Large angle, double-ring

e

RFRF SR

e

IP

22 m

rad2. 5m8ns

1. 5cm

0.1cm

5

BEPCII Design goalBEPCII Design goal

Energy range 1 – 2 GeV

Optimum energy 1.89 GeV

Luminosity 1 x 10 33 cm-2s-1 @ 1.89 GeV

Injection Full energy injection: 1.55 1.89 GeV Positron injection speed > 50 mA/min

Synchrotron mode 250 mA @ 2.5 GeV

6Passed SLAC review in May 2002.

BEPCII BEPCII main parametersmain parametersEnergy E(GeV) 1.89 Energy spread(10-4) σe 5.16

Circumference C(m) 237.53 Emittance εx/εy(nm) 144/2.2

Harmonic number h 396 Momentum compact αp 0.0235

RF frequency frf(MHz) 499.8 β*x /β*

y(m) 1/0.015

RF Voltage Vrf(MV) 1.5 Tunes νx/νy/νz 6.57/7.6/0.034

Energy loss/turn U0(keV) 121 Chromaticities ν’x/ν’

y -11.9/-25.4

Damping time τx/τy/τz(ms) 25/25/12.5 Natural bunch length σz0(cm) 1.3

Total current/beam I(A) 0.91 Crossing angle (mrad) ±11SR Power P(kW) 110 Piwinski angle Φ(rad) 0.435Bunch number Nb 93 Bunch spacing Sb(m) 2.4

Bunch current Ib(mA) 9.8 Beam-beam parameter x/ y 0.04/0.04

Particle number Nt 4.5×1012 Luminosity(1033cm-2s-1) L0 1.0

7The BESIII The BESIII DetectorDetector

工

8

Main drift chamber• Inner diameter: 63mm; Outer diameter: 810mm; length: 2400 mm• Inner cylinder: 1 mm Carbon fiber, outer cylinder: 10 mm CF wit

h 8 windows• End flange: 18 mm thick Al 7075 ( 6 steps) • 7000 Signal wires : 25(3% Rhenium) m gold-plated tungsten • 22000 Field wires: 110 m gold-plated Aluminum • Small cell: inner---6*6 mm2, outer--- 8.2 *8.2 mm2,• Gas: He + C3H8 (60/40)• Momentum resolution (@ 1 GeV/c):

• dE/dX resolution: 6-7%.

%37.0%32.0 t

P

Pt

9

85μm

10

EMC: CsI(Tl) crystals• 6300 crystals, (5.2x 5.2 – 6.4 x 6.4) x 28cm3 (15 X0) • PD readout, noise ~1100 ENC• Energy resolution: 2.5%@1GeV • Position resolution: 5mm@1GeV• Tiled angle: theta ~ 1-3o, phi ~ 1.5o

• Minimum materials between crystals

11

no partition wall Mechanical support structure

12

Super-conducting magnet• Al stabilized NbTi/Cu conductor from Hitachi• 1.0 T, <5% non-uniformity• 921 turns, 3150A @4.5K• R = 1.475 m, L=3.52m, cold mass 3.6t• Thickness: 1.92 X0

• Inner-winding methodEsti mati on of the vol tage by quench

0. 050. 0

100. 0150. 0200. 0250. 0300. 0350. 0

1 2 4 8 10 20 30Quench Length (m)

Coil V

olta

ge (m

V)

13

Particle ID: TOF system• 392 pieces BC408, 2.4 m long, 5cm thick • Time resolution 100-110 ps/layer• PMT: Hamamatzu R5942

图 3.8.20 桶部光电倍增管的支撑环，内外两层共 176 个孔。

14

system : RPC• 9 layers, 2000 m2

• Bakelite, no linseed oil • 4cm strips, 10000 channels• Tens of prototypes (up to 1*0.6 m2 )• Noise less than 0.2 Hz/cm2

15

Other systems• Electronics design have been almost finished, several

prototypes have been successfully tested• Trigger system largely based on FPGA technology have been

designed, prototypes underway• DAQ system based on VME/PowerPC and PC farm have

been designed, mini-version setup, software underway• Offline computing environment based on a large scale PC

farm is under study• MC based on GEANT4, first reconstruction framework

released, sub-detector reconstruction code underway

16

Schedule• 5/2004: BESII detector shutdown • 11/2004: supporting structure/york installation• 3/2005: muon chamber installation• 5/2005: magnet installation• 10/2005: magnetic field mapping• 2/2006: EMC installation• 3/2006: MDC/TOF installation• 6/2006: Cosmic-ray run• 9/2006: BESIII detector in place• 12/2006: tuning of detector/machine

Physics at BEPCII/BESIII

• Rich source of resonances, charmonium, and charmed mesons• Transition between perturbative and non-perturbative QCD• Charmonium radiative decays are the best lab to search for glueb

alls, hybrids, and exotic states

Physics to be studied in -charm region

Search for glueballs, quark-gluon hybrids and exotic states Charmonium Spectroscopy and decay properties Precision measurement of R Tau physics: tau mass, tau-neutrino mass, decay properties, Lorenz structure of charged current, CP violation in tau decays …

Charm physics: including decay properties of D and Ds, f

D and fDs;; charmed baryons.

Light quark spectroscopy, mc

Testing QCD, QCD technologies, CKM parameters New Physics: rare decays, oscillations, CP violations in c- hadrons …..

To answer these physics questions, need precision measurements with

• High statistics data samples • Small systematic errors

20

Event statistics at BESIII 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

*CLEO took 10 nb D production cross section while we took 5 nb

21

Semi-leptonic decays – one year running

Decay Mode

Input

Br(%)

DetectionEfficiency

Statistics Errors

CKM Elements

D0 K-e+e3.4%

54.6%0.6 % Vcs

D0 K-+ 30.5%

D0 -e+e0.4%

62.2%1.6% Vcd

D0 -+ 44.3%

8.5%6.7%

1.6% Vcs3.7%

0KDe

0eKD

Vcs /Vcs = 1.6%,

Vcd /Vcd = 1.8% Emissing-Pmissing

22

Pure Leptonic decaysDecay Modes

Decay Constant

Branching ratios

Life time

CKM Elements

Precision of decay constants

D+→ fD 2.4% 1.2% 1.8% 3.0%

D+s→

fDs 1.7% 1.8% 0.1% 2.5%

One year of running

23

Absolute Br measurement: clear D tagging

beam energy spread important

One year of running

24

Non-leptonic decaysDecay Mode

Input Br(%)

Detection efficiency

Statistics Error (B/B)

3.7 72.2%~ 0.4%~7.8 34.0%

~12.0 32.0%~7.7 52.0%

~ 0.6%

2.8 12.5%~5.6 9.2%~8.6 7.9%~5.0 22.5%

D+s→ ~3.0 60.0% ~ 1.2%

KD0

KD0

00 KD

KD 0KD

0KD

0KD00KD

One year of running

25

B-Factories CLEO-C BEPCII 400 fb-1 3fb-1 5fb-1

Br(D0→K-+) < 1% <1%Br(D+ →K-+ +) 3-5% <1% <1%Br(D+

s →-+) 5-10% <2% ~ 2%

fD >10 % ~2% ~3%

fDs 6-9% ~2% ~2.5%

Vcs 16% ~1% ~1.5%

Vcd 7% ~1.5% ~2%

Comparison with other facilities

*CLEO took 10 nb D production cross section while we took 5 nb

One year of running

26

DDbar Mixing at BESIII

• DDbar mixing in SM ~ 10 –3 - 10 –10

• DDbar mixing sensitive to “new physics”• Our sensitivity : ~ 10-4

• D0 D0 (K- Acceptance: ~ 40% Background: ~ 10-4

27

QCD and hadron production

• R-value measurement• pQCD and non-pQCD boundary• Measurement of s at low energies• Hadron production at J/’, and continuum • Multiplicity and other topology of hadron event • BEC, correlations, form factors, resonance, etc.

28

R-value measurement

Error on R (5)had (MZ

2)

5.9% 0.02761 ±0.00036 3% 0.02761 ±0.00030 2% 0.02761 ±0.00029

R-value below 2GeV

is important,

via radiative return

29

Errors on R at BESIII Error sources BESII (%) BESIII (%)

Luminosity 2 - 3 1

Detection efficiency 3 - 4 1 - 2

Trigger efficiency 0.5 0.5

Radiative corrections 1 - 2 1Hadron decay model 2 - 3 1 – 2

Statistics 2.5 --

Total 6 – 7 2 - 3

30

Light hadron spectroscopy

• Baryon spectroscopy• Charmonium spectroscopy• Glueball searches• Search for non-qqbar states• Search for 1P1

31

Tau-charm physics after CLEOc?Tau-charm physics after CLEOc?• CLEOc begins running now!• What important physics issues will remain in 2007?• Is the BESIII detector design adequate to address these?• There will be a workshop on these issues in January

2004 in balmy Beijing. Workshop will be a CLEOc/BES joint effort.

• More studies needed before the workshop. • Stay tuned. Will post announcement on the QWG web

page. • Please come.

1.0 T 1.0 T

magnet

----9 layers counter

RichT(ps) = 100-110/layer Double layer TOF

2.0%0.3 cm /E

E/E(0/0) = 2.5 %(1 GeV)z(cm) = 0.5cm/E

EMC6%dE/dx (0/0) = 6 - 7 %

0.5 %P/P (0/0) = 0.5 %(1 GeV) MDC90 mXY (m) = 130CLEOcBES III SubdetectorThe detector of BESIII and CLEOc

33

International collaboration IHEP, Beijing Beijing University , Beijing Tsinghua University , Beijing USTC, Hefei National Central University, Taipei KEK, Tokyo University, Tokyo

Hawaii University, Honolulu

Washington University, Seattle

More collaborators welcomed

34

Summary• The BEPCII/BESIII has been approved officially

by the chinese government• The initial BESIII detector design is finished, prot

otyping is underway, mass production is about to start.

• Rich physics after CLEO-c (upgrade of BEPCII to 3*1033 cm-2s-1 is possible)

• Collaborators are welcomed!