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Yi-Fang Wang

Institute of High Energy Physics

A high luminosity experiment at tau-charm region

--- BEPCII/BESIII upgrade program

Beijing e+e- collider(BEPC) consists of Linac, Storage Ring, Spectrometer(BES) and Synchrotron Radiation Facility（BSRF)It started construction in 1984 and completed in 1988

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Beam Energy: 1 Beam Energy: 1 –– 2.8 2.8 GeVGeV LuminosityLuminosity：： 10103131cmcm--22ss--11 @ 1.89 @ 1.89 GeVGeV

ColliderCollider physicsphysics：：5 months5 months；；SRSR：：3 months3 months；；machine studymachine study：：2 months2 months

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Korea (3)Korea University

Seoul National University Chonbuk National University

Japan (4)

Nikow UniversityTokyo Institute of Technology

Miyazaki UniversityKEK

USA (4)University of Hawaii

University of Texas at DallasColorado State University

Stanford Linear Accelerator Center

UK (1)Queen Mary University

China (15)IHEP of CAS

Univ. of Sci. and Tech. of ChinaShandong Univ., Zhejiang Univ.

Huazhong Normal Univ.Shanghai Jiaotong Univ. Peking Univ., CCAST

Wuhan Univ., Nankai Univ.Henan Normal Univ.

Hunan Univ., Liaoning Univ. Tsinghua Univ., Sichuan Univ.

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BESII Detector BESII Detector ((19951995--1997 upgrade1997 upgrade))

VC: σxy = 100 µm TOF: σT = 180 ps µ counter: σrφ= 3 cm MDC: σxy = 200 µm BSC: ∆E/√E= 22 % σz = 5.5 cm

σdE/dx= 8.4 % σφ = 7.9 mr B field: 0.4 T∆p/p=1.8√(1+p2) σz = 2.3 cm Dead time/event: 10 ms

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Main results: R value measurement

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2 3 4 5

(a)

Ecm (GeV)

R V

alu

e

Gamma2MarkIpluto

BESII (1998)BESII (1999)

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3

4

5

3.8 4 4.2 4.4 4.6

(b)

Ecm (GeV)

R V

alu

e

)ee()hadronsee(R −+−+

−+

→→

=µµσ

σ

Before BES, the most probable

mass of Higgs is about 60 GeV

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Tau mass measurement

mτ = 1776.9 ±0.2 MeV+0.4

-0.5

BES results reduced the error

by a factor 8, and shifted the

central value by 3σ, improved

lepton universality(2.4σ 1.5σ)

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An enhancement near pp threshold

M=1859 MeV/c2

Γ < 30 MeV/c2 (90% CL)

J/ψ γpp

M(pp)-2mp (GeV)0 0.1 0.2 0.3

3-body phase spaceacceptance

χ2/dof=56/56

fitted peak location

acceptance weighted BW +3 +5

−10 −25

BESII

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The need for upgrade• Interesting physics limited by statistics:

glueball/hybrid searches, CKM matrix elements DDbar mixing, ρπ puzzle, non-pQCD…

• Systematic error is also large due to poor resolution

• Detector is aging• Multi-bunch mode

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On Feb. 10, 2003, the chinese government, the state council, approved officially the BEPCII/BESIII u p g r a d e p r o j e c t

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

e

RFRF SR

e

IP

22 m

rad

2. 5m8ns

1.5cm

0 . 1 c m

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Double ring installation Double ring installation –– Wood modelWood model

No spacing problems No spacing problems

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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

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BEPCII BEPCII main parametersmain parameters

1.0Luminosity(1033cm-2s-1) L04.5×1012Particle number Nt

0.04/0.04Beam-beam parameter ξx/ ξy9.8Bunch current Ib(mA)

2.4Bunch spacing Sb(m) 93Bunch number Nb

0.435Piwinski angle Φ(rad)110SR Power P(kW)

±11Crossing angle φ(mrad) 0.91Total current/beam I(A)

1.3Natural bunch length σz0(cm) 25/25/12.5Damping time τx/τy/τz(ms) -11.9/-25.4Chromaticitiesν’x/ν’y121Energy loss/turn U0(keV)

6.57/7.6/0.034Tunes νx/νy/νz1.5RF Voltage Vrf(MV)

1/0.015β*x /β*y(m) 499.8RF frequency frf(MHz)

0.0235Momentum compact αp396Harmonic number h

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

5.16Energy spread(10-4) σe1.89Energy E(GeV)

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15The BESIII The BESIII DetectorDetector

工工

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

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

• dE/dX resolution: 6-7%.

%37.0%32.0 ⊕=t

P

Pt

σ

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85μm

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EMC: CsI(Tl) crystals• 6300 crystals, (5.2x 5.2 – 6.4 x 6.4) x 28cm3

• 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

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no partition wall Mechanical support structure

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Super-conducting magnet• Al stabilized NbTi/Cu conductor from Hitachi• 1.0 T,

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Test beam resultsEff. Atten. Length(cm)：

East WestBC404-5cm 333.3 333.3BC408-5cm 243.9 227.2BC408-4cm 196.1 178.5BC408-6cm 250 227.3

BC408 5cm

y = 5225.5e0.0041x

y = 3937.3e-0.0044x

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

-100 -50 0 50 100 150

Z in cm

A

A1

A2

指数 (A1)

指数 (A2)

BC404 5cm

y = 4302.6e-0.003x

y = 5987.1e0.003x

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

-100 -50 0 50 100 150

Z in cm

A

A1

A2

指数 (A2)

指数 (A1)

BC408 4cm

y = 4951.8e0.0051x

y = 3363.2e-0.0056x

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

-100 -50 0 50 100 150

Z in cm

A

A1

A2

指数 (A1)

指数 (A2)

BC408 6

y = 4396.8e-0.0044x

y = 4856.8e0.004x

0

1000

2000

3000

4000

5000

6000

7000

8000

-100 -50 0 50 100 150

A1

A2

指数 (A2)

指数 (A1)

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0

50

100

150

200

250

300

350

50 100 150 200 250 300

resolution(ps)

80

100

120

140

160

180

200

60 100 140 180 220 260 300Z

resolution(ps)

BC408 5*6 BC404 5*6 BC408 4*6 BC408 6*6

BC404-5cm

Errors from T0

and electronics

not subtracted

BC408

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µ system : RPC• 9 layer, 2000 m2

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

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

RPC Det ect i on Ef f i ci ency

0. 00%

10. 00%

20. 00%

30. 00%

40. 00%

50. 00%

60. 00%

70. 00%

80. 00%

90. 00%

100. 00%

5500 6000 6500 7000 7500 8000 8500 9000

Hi gh Vol t age ( V )

Det

ectio

n Ef

ficie

ncy

0r ad

5000r ad

10000r ad

20000r ad

50000r ad

100000r ad

RPC Count i ng Rat e

0

0. 02

0. 04

0. 06

0. 08

0. 1

0. 12

0. 14

0. 16

0. 18

0. 2

0. 22

0. 24

5500 6000 6500 7000 7500 8000 8500 9000

Hi gh Vol t age ( V )

Coun

ting

Rat

e (H

z/cm

2 )

0r ad

5000r ad

10000r ad20000r ad

50000r ad

100000r ad

RPC Count i ng Rat e Rever si on

0

0. 02

0. 04

0. 06

0. 08

0. 1

0. 12

0. 14

0. 16

0. 18

0. 2

0. 22

0. 24

5500 6000 6500 7000 7500 8000 8500 9000Hi gh Vol t age ( V )

Coun

ting

Rate

(µA

/m2 )

0 hour 20 hour s 30 hour s 50 hour s80 hour s 190 hour s 320 hour s 0r ad

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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

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Beam background: a serious issue1.89 GeV @ 1 Amp

All Cu surfaces

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Direct SR photons on Be pipe/LUMI/MDC elec.

• Normal case on Be pipe: 1.6 W, worst case 20 W• All have Ec < 1 KeV, No masks possible• Dose < 100 rad/year@MDC electronics• Rate < 20 KHz/wire

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Bremsstrahlung

Coulomb

A total of 6 pairs of masks

1.89GeV@0.9A, 5nT vacuum

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Beam-Gas background

• Total dose near the interaction region ~ 150 MeV/µs• < 20 rad/year @ CsI crystals• < 20 rad/year @ MDC electronics• < 1 rad/year @ TOF • OK for safety

MDC < 20 KHz/wire TOF < 5 KHz/ch @E>500 KeVEMC < 2 KHz/ch @E>100 KeV

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Schedule• 7/2004: 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

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Physics at BEPCII/BESIII

• Precision measurement of CKM matrix• Precision test of Standard Model• QCD and hadron production• Light hadron spectroscopy• Charmonium physics• Search for new physics

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We are unique

• In a regime of transition between pQCD and non-pQCD

• Provide calibrations and tests for LQCD• Rich spectra of light hadrons for Quark model

test• Threshold production of tau-charm

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Event statistics at BESIII

1.2×1071.03.67τ

2.0×1060.64.14Ds

1.0×1060.64.03Ds

2.5×1071.03.77D

3.0 ×1091.03.686ψ’

1.0×10100.63.097J/ψ

Events/yearLuminosity(1033 cm–2s –1)

Energy (GeV)

Physics Channel

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

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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 matrix

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Semi-leptonic decays

Vcs

Vcd

Vcs

CKM Elements

3.7%1.6%

6.7%8.5%

44.3%D0 π-µ+νµ1.6%

62.2%0.4%

D0 π-e+νe

30.5%D0 K-µ+νµ0.6 %

54.6%3.4%

D0 K-e+νe

Statistics Errors

DetectionEfficiency

Input

Br(%)

Decay Mode

µ++ νµ→ 0KD

e0eKD ν→ ++

∆Vcs /Vcs = 1.6%,

∆Vcd /Vcd = 1.8% Emissing-Pmissing

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Pure Leptonic decays

2.5%0.1%1.8%1.7%fDsD+s→µ+ν

3.0%1.8%1.2%2.4%fDD+→µ+ν

Precision of decay constants

CKM Elements

Life time

Branching ratios

Decay

Constant

Decay Modes

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Absolute Br measurement: clear D tagging

beam energy spread important

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Non-leptonic decays

~ 1.2%60.0%~3.0D+s→ φπ+22.5%~5.07.9%~8.69.2%~5.612.5%2.8

~ 0.6%

52.0%~7.732.0%~12.034.0%~7.8 ~ 0.4%72.2%3.7

Statistics Error (∆B/B)

Detection efficiency

InputBr(%)

Decay Mode

+−π→ KD0

−++− πππ→ KD000 KD ππ→ +−

++−+ ππ→ KD++ π→ 0KD

0KD πππ→ ++−+

−+++ πππ→ 0KD00KD ππ→ ++

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CKM matrix elements measurement

5%39%Vts

5%36%Vtd

3%5%Vcb

1%16%Vcs

1%7%Vcd

5%25%Vub

BESIII Current

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Precision test of SMand Search for new Physics

• DD mixing• Lepton universality• CP violation• Rare decays

FCNC, Lepton no. violation, ...

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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-π+) (Κ+π−) Acceptance: ~ 40% Background: ~ 10-4

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QCD and hadron production

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

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R-value measurement

1

2

3

4

5

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2 3 4 5

(a)

Ecm (GeV)

R Va

lue

Gamma2MarkIpluto

BESII (1998)BESII (1999)

2

3

4

5

3.8 4 4.2 4.4 4.6

(b)

Ecm (GeV)

R Va

lue

0.02761 ±0.000292%0.02761 ±0.00030 3%0.02761 ±0.000365.9%∆α(5)had (MZ2)Error on R R-value below 2GeV

is important,

via rediative returns

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Errors on R at BESIII

--2.5Statistics

2 - 36 – 7 Total

1 – 22 - 3Hadron decay model11 - 2 Radiative corrections

0.50.5Trigger efficiency1 - 23 - 4Detection efficiency

12 - 3Luminosity

BESIII (%)BESII (%)Error sources

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Light hadron spectroscopy

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

1010 J/ψ events is probably enough to pin down most of problems of light hadron spectroscopy

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Excited Baryons from J/ψ and ψ(2s) Decays

• Test of QCD and confinement

• Reveal the quark-gluon structure of matter

• Only 10% excited baryons(N*, Λ*, Σ* and Ξ*) observed

• Complementary to CEBAF, GRAAL and SPRING8

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Search for glueballs• no place in nonet• enhanced in J/ψ decays• branching ratios incom-

patible with SU(3) predictions

• reduced γγ couplings

Candidates: f0(1500), f0(1700),ξ(2230), ….

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Good energy/mass resolution

J/ψ −> γξ(2230)−>γηη’--> γγγγγπ+π−

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Non qqbar exotic 1-+ state

• J/ψ ρ0ηπ0

Well identifiedρ(1390) ρ(2300)

via partial waveanalysis 0

10000

20000

30000

40000

50000

0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4M η π0 (Gev / c

2)

30

Mev

/bin

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Search for 1P1Βr = (1.2 – 3.3)×10-6

450-1200 evts/year

ψ(2S) π0 1 P 1 γγγ ηc γγγ 4ΚΒackground: ψ(2S) γ χc1, γχc2,, ηψ,π0π0ψ

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Event Statistics: BESIII vs CLEO-c

0.0015

—

0.03 *——

1.0

CLEOBEPCIICLEOBEPCII

0.50

0.50

0.300.300.300.15

0.0121.03.67τ

0.0020.64.14Ds

0.0010.64.03Ds

0.0251.03.77D3.0 1.03.686ψ’

10.00.63.097J/ψ

Events/year(109)

Luminosity(1033 cm–2s –1)

Energy (GeV)

Physics Channel

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

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~2%~1.5%7%Vcd

~1.5%~1%16%Vcs

~2.5%~2%6-9%fDs

~3%~2%>10 %fD

~ 2%

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International collaborationIHEP, BeijingBeijing University , BeijingTsinghua University , BeijingUSTC, HefeiNational Central University, TaipeiKEK, Tokyo University, Tokyo

Hawaii University, Honolulu

Washington University, Seattle

Welcome more collaborators

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Summary• The BEPCII/BESIII has been approved officially

by the Chinese government• The BESIII detector design is finished,

prototyping is underway, some of the mass production have been started

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