1

Frederick A. HarrisFrederick A. HarrisUniversity of HawaiiUniversity of Hawaii

Recent Results from

BESIIISLAC Experimental Seminar

April 3, 2012

2

OUTLINE

IHEP

• Introduction • BEPCII/BESIII• Physics results c hc cJ

decaysψ’

P, pp

X(1860), X(1835), X(1870) J/

decays

• Charm physics• Beam energy measurement• Summary

Thanks to Haibo

Li, Steve Olsen, and many others.

3

Physics of tau

–

charm regionAn important measurement at an e+e-

collider

is thecross section for e+e-

hadrons, σ(e+e-

hadrons), asa function of the energy.Often this is given as a ratio: )(

)(

ee

hadronseeR

BES

4

Physics of tau

– charm region

Charmonium: cc

threshold for

pairsopen charm

Very rich and interesting energy region.

Nobel prize

Likepositronium

5

• Light hadron spectroscopy.•

Charmonium: J/, (2S), C

(1S), C{0,1,2}

, C

(2S), hC

(1P1

), (3770), etc. •

New Charmonium states above open charm threshold (X, Y, Z).• In J/

and (2S) hadronic

decays:

Exotics : hybrids, glueballs, and other exotics.

Baryons and excited baryons.

Mesons and mixing of quarks and gluons.

•

Electromagnetic form factors and QCD cross section (R values).•

High precision tau

and charm physics near threshold. Tau

mass.

Physics of tau

–

charm region

bsdtcu

e

eTremendous

variety:

6

Open charm factory: ψ”

DD• Absolute BR measurements of D and Ds decays• Rare D decay• D0 - D0bar mixing• Quantum correlations (ψ”)• CP violation, strong phase.• f D+

, fDs

, form factors in leptonic

D decays• Can provide calibrations and tests of lattice QCD.• Precise measurement (~1.6%) of CKM (Vcd, Vcs)• Light meson spectroscopy in D0

and D+

Dalitz

plot analyses.• Search for new physics.

Very rich and interesting energy region.

Physics of tau

–

charm region

(3770) (4040), etc.: D, D*, DS

7BEPCII/BESIII

8

BEPCII:

a high luminosity double–ring collider

SC RF

Beam magnets

Beam energy: 1.0-2.3GeV

Luminosity: 1×1033 cm-2s-1

Optimum energy:1.89 GeV

No. of bunches:93

Bunch length:1.5 cm

Total current:0.91 A

SR mode:0.25A @ 2.5 GeV

Circumference:237 m Use many bunches

and SC mini-beta.

22 mrad

crossing angle

9

10

BESIII Detector

Be beam pipe

1 T SC magnetMagnet Yoke

CsI(Tl) calorimeter:E = 2.5% at 1 Gev

TOF:80 ps

-

barrel

RPC9 layers

1 m

MDC:

p/p

= 0.58%, dE/dx

~ 6% at 1 GeV Int. J. Mod. Phys. A24, 377 (2009)NIM A614, 345 (2010)

11

12

13

c

14

c

(1s)

Precise measurement of c

mass provides information on the hyperfine (ΔM(1S)) splitting of c

and J/. Also important to check lattice QCD calculations.

S wave spin singlet ground state of charmonium.

Known for long time.

15

ExclusiveJ/Ψ

c

15

CLEOc: J/Ψ

and Ψ(2S) c

•

Shape can not be explained by simple BW + resolution.

•

Use empirical form.•

May explain 3σ

difference

with mass from

fusion and p-pbar

annihilation.

CLEO, Phys. Rev. Lett. 102, 011801 (2009).

PDG2010

CLEO

c

(1s) But: mass and width poorly determined.

1616

’c

, c

exclusive decays

Relative phase

for each mode consistent within

3, use a common phase value in the simultaneous fit.

KsKK+K

KsK3 2K2

Simultaneous fit with modified Breit-Wigner

(hindered M1) with sig. interference

(15 between c

and non-c

decays.

BESIII

17

Mass and Width of Mass and Width of ccBESIII

mass

= 2984.4±0.5stat±0.6syst

MeV/c2

width

= 30.5±1.0stat±0.9syst

MeV

= 2.35±0.05stat

±0.04syst

rad

Currently BESIII is the most precise measurement

BESIII

BESIII, accepted by PRL, arXiv:1111.0398

Hyperfine splitting: ∆M(1S) = 112.5 ±

0.8 MeV/c2

Theorists much happier.

18

c

(2S)•

First “observation”

by Crystal Ball in 1982 (M=3.592GeV,

from '

X) never confirmed.•

Published results:

•

Combined with two-photon results from BaBar

and Belle reported at ICHEP 2010, the world average (c

(2S))=12±3 MeV/c2.•

BESIII studies: ' c

(2S) Ks

K

(K+K-

0

etc. in progress).

19

Simultaneous fit of c

(2S) and

cJ N(c

(2S)) = 50.6±9.7 Statistical significance more than

6

Significance with systematic variations not less than

5

2/ndf=0.9

c

(2S) signal: modified BW (M1) with fixed width. (The resolution is extrapolated from

cJ

) cJ

signal: MC shape smeared with Gaussian.

BG from

e+

e- Ks

K (ISR), ' Ks

K

(FSR), '

0

Ks

K , : are measured from data.

First observation

of

c

(2S)

preliminary

20

Preliminary measurements from '

c

(2S)KsK

Br(Br(' cc

(2S))=(4.7(2S))=(4.7±±0.90.9statstat±±3.03.0syssys

) ) ××1010--44

CLEO-c: <7.6104 (PRD81,052002(2010))Potential model: (0.16.2)104

(PRL89,162002(2002))

M(M(cc

(2S))=3638.5(2S))=3638.5±±2.32.3statstat±±1.01.0sys sys (MeV/c(MeV/c22))

Br(Br('cc

(2S)(2S)KsKKsK)=(2.98)=(2.98±±0.570.57statstat±±0.480.48syssys

) ) ××1010--66

Br(c

(2S)KK)=(1.9±0.4±1.1)% from BaBarpreliminary

21

hc

2222

hc

(1P1

)

CLEOc

used 'πo

hc

, hc

c

and obtained:

CLEO

M(hC

)

important to learn about hyperfine (spin-spin) interaction of P wave states.

M(hC

)AVG

= 3525.20

0.18

0.12 MeV/c2

(B1

x B2

)AVG = (4.16 ±

0.30 ±

0.37) x 10-4PRL 101, 182003 (2008).

Hyperfine or triplet-singlet splitting determined by spin-spin term in QCD potential models. ~ 0 if no spin-spin interaction.

∆Mhf

(1P) = <M(3PJ

)> -

M(1P1

) = +0.08 ±

0.18 ±

0.12 MeV,where <M(3PJ

)> = spin weighted centroid

of 3PJ

states = [M(cJ

) + 3*M(cJ

) + 5*M(cJ

)]/9Consistent with lowest order expectation of 0.

Poorly known. Not in PDG summary table until 2008.

23

Methods to study hc

Only detect π0

: inclusive.Rate ~ B(‘

πo

hc

)

Detect π0

and : E1

tagged. Rate ~ B(‘

πo

hc

) x B(hc

c

)

Exclusive c

decays

Detect π0, , and c

decay:exclusive. Rate ~ B(‘

πo

hc

) x B(hc

c

) x B(c

X)

24

´0hc

24

BESIII

backgroundsubtracted

BES Collaboration, PRL 104, 132002 (2010)

backgroundsubtracted

Inclusive events

Tagged events

Mass = 3525.40±0.13±0.18 MeV/c2

Width = 0.73±0.45±0.28 MeV< 1.44 MeV

@90% CL

combining inclusive and tagged results B(' 0 hc ) =

(8.4±1.3±1.0) ×10-4

B(hc c ) = (54.3±6.7±5.2)%

First measurement

First measurements

25

hc

: tagged/inclusive analysis summary

BESIII theoretical predictionsBr(’→0hc

) [10-4] 8.4±1.3±1.0 4 –

13 Kuang

Br(hc→c

) [%] 54.36.75.2 41 (NRQCD) Kuang88 (PQCD) Kuang38 Godfrey, Rosner

Theoretical predictions: Kuang, PRD65, 094024 (2002), Godfrey & Rosner, PRD 66, 014012 (2002).

BES Collaboration, PRL 104, 132002

(2010)

CLEO-c Collaboration, PRL 101, 182003 (2008)

2

BESIII CLEOc Th(Kuang)

Br(’→0hc

) ×Br(hc→c

) [10-4]4.58±0.40±0.50 4.16±0.30±0.37

M [MeV/c2] 3525.400.130.18 3525.200.180.12

[MeV] 0.73±0.45±0.28< 1.44 @ 90%CL

1.1 (NRQCD) 0.51 (PQCD)

Mhf

(1P) [MeV/c2] 0.10±0.13±0.18 0.08±0.18±0.12

2626

’

0hc

, hc

c

, c

exclusive decays

Simultaneous fit to

0

recoiling mass2/d.o.f. = 32/46Mass

=

3525.31±0.11±0.15

MeV/c2

Width =

0.70±0.28±0.25 MeV

Consistent with BESIII inclusive and CLEOc

results

Summed distribution

832±35 evts.

BESIII Preliminary

Currently the most precise measurements

27

c

lineshape

from

’

0hc

, hc

c

Lineshape

from this decay mode is much less distorted than for J/, ‘

c

; the non-resonant interfering background is small. This channel may be much better for determining the c

resonance parameters.BESIII Preliminary

28

cJ

results

29

Measurements of cJ

→

V, V=,ρ,

• c1

observed for first time.

)2 (GeV/cωH

γM3.35 3.4 3.45 3.5 3.55 3.6

)2E

vent

s / (

0.0

1 G

eV/c

0

10

20

30

40

50

60

70

80

)2 (GeV/cωH

γM3.35 3.4 3.45 3.5 3.55 3.6

)2E

vent

s / (

0.0

1 G

eV/c

0

10

20

30

40

50

60

70

80

)2 (GeV/cρH

γM3.35 3.4 3.45 3.5 3.55 3.6

)2E

vent

s / (

0.0

05 G

eV/c

0

20

40

60

80

100

120

140

160

)2 (GeV/cρH

γM3.35 3.4 3.45 3.5 3.55 3.6

)2E

vent

s / (

0.0

05 G

eV/c

0

20

40

60

80

100

120

140

160

)2 (GeV/cφH

γM3.35 3.4 3.45 3.5 3.55 3.6

)2E

vent

s / (

0.0

1 G

eV/c

0

5

10

15

20

25

30

)2 (GeV/cφH

γM3.35 3.4 3.45 3.5 3.55 3.6

)2E

vent

s / (

0.0

1 G

eV/c

0

5

10

15

20

25

30

Mh

(GeV/c2)Mhρ

(GeV/c2)Mh

(GeV/c2)

c1

c1

ρ c1

BESIIIpreliminary

BESIIIpreliminary

BESIIIpreliminary

BESIIIψ’

χcJ

, χcJ

V (, ρ, ) K+K-, ρ

π+π-, π+π-π0

mKK

mππ mπππ

30

Measurements of cJ

→

V, V=,ρ,B (10-6) BESIII CLEOc pQCDc0

< 16.2 < 6.4 0.46c1

25.8 ±

5.2

±

2.3 < 26 3.6c2

< 8.1 < 13 1.1c0

ρ0 < 10.5 < 9.6 1.2c1

ρ0 228 ±

13 ±

22 243 ±

19 ±

22 14c2

ρ0 < 20.8 < 50 4.4c0

< 12.9 < 8.8 0.13c1

69.7 ±

7.2 ±

6.6 83 ±

15 ±

12 1.6c2

< 6.1 < 7.0 0.5

CLEOc: PRL 101, 151801 (2008)

pQCD: Y.J. Gao

et al., hep-ph/0701009

• pQCD

predictions x10 too low.•

Difference may be explained by non-perturbative

QCD “loop

corrections”. D.Y Chen et al, Eur. Phys. J. C70, 177 (2010).

BESIII

BESIII: Phys. Rev. D83, 112005 (2011)

31

φφ→4K

φφ→K+K-+-0

ωω→2(+-0)

φω→K+K-+-0 large and clear

c1

signal

•

c1

VV

is suppressed due to helicity

selection rule in

pQCD•

Only

c0

and

c2

decays into

and

have been observed

so far.•cJ

ωφ is doubly OZI suppressed, never observed before

Obvious φω

signal

cJ

VV, V = in BESIIIBESIII

Phys. Rev. Lett. 107, 092001 (2011).

32

•

C1

→φφ, ωω

decays observed for the first time with surprisingly large branching ratios. Helicity

selection rules not applicable here?• Doubly OZI-suppressed decay

CJ → φω observed for the first time.•

Other branching ratios consistent with but more accurate than previous measurements.

cJ

VV, V = in BESIIIBESIII

33

First observation of ψ’

P, pp

34

' P (P = 0,, and

')• Important for testing various phenomenological mechanisms:

vector meson dominance, c

–

(‘)

mixing, 2 gluon couplingsto qq

states, and final state radiation by light quarks.

• RJ/

= B(J/ η)/B(J/ η‘)• R'

= B(' η)/B('

η‘) ≈ RJ/

is expected. LO-pQCD• B(' π0) expected to be small (2.2 x 10-7).

• Recently, CLEOc

reported on J/, ‘, “

P:• Found no evidence for ‘

π0

or η.• Determine

B(‘

π0) < 5 x 10-6.

• Obtain

R'

< 1.8% at 90% CL and

RJ/

= (21.1 +/-

0.9)%.R'

<< RJ/

poses a significant challenge to theory.

CLEOc, PRD 79, 111101 (2009)

Rosner, PRD 79,097301 (2009)

35

' P (P =

and

')BESIIIBESIII studies:

• ' 0

using 0

.• '

using +

-

0

and 000.• ' ' using ' +-

and +-

withη.

π0

+-0

000

' +-

‘

+-

36

' P (P = ,, and

')BESIII

Phys. Rev. Lett

105, 261801 (2010).

BranchingRatios(x 10-6)

• Measured branching ratiosfor ‘

π0

and η

for first time.• First measurement of

R'

= (1.10 ±

0.38 ±

0.07).• Consistent with CLEO upper limit.

• R'

<< RJ/

• Related to

puzzle? Q. Zhao, Phys. Lett. B697, 52 (2011).

37

M2(p

M2 (

pp

M2(

M2(p

38

X(1835), X(1860), & X(1870)

39

pp threshold enhancement: X(1835)

Consistent observation by BESIII !

Published in Chinese Physics C 34, 421 (2010)

M=1861 +6 -13

+7-26

MeV/c2

< 38 MeV/c2

(90% CL)

J / , J / pp BESIIIJ/ pp

M=1859 +3 -10

+5-25

MeV/c2

< 30 MeV/c2

(90% CL)

Phys. Rev. Lett. 91, 022001 (2003) 195 citations

40

pp threshold enhancementBESIIIJ/ pp

41

pp threshold enhancementBESIIIPWA results and projections

42

pp threshold enhancementBESIII

•

Fit with BW and S-wave FSI (I=0) can describe pp-bar mass threshold.• Much better than without FSI effect (7.1 ).• Different FSI models considered.• JPC

= 0-+

(> 6.8 than other JPC

assignments)

M=1832 ±5 (stat)

+18 -17 (sys) ± 19 (model) MeV/c2

= 13 ± 20 (stat)+11-33

(sys) ± 4 (model) MeV/c2

or Γ < 76 MeV/c2 (90% CL)

B(J/ X)•B(X pp-bar)

= (9.0 +0.4-1.1

(stat) +1.5-5.0 (syst) ±2.3 (model)) x 10-5

BESIII, accepted by PRL, arXiv:1112.0942 (2011)

43

44

X(1835) at BESII

•

The X(1860) should be detected in other decay modes.

•

G.J. Ding and M.L. Yan suggest η’ππ to be a

favorable mode. (PRD C72, 015208 (2005).) –

there is gluon content in pp

–

η’

has strong coupling to gluons

PRL 95, 262001 (2005)

M = 1833.7 ±

6.1 ±

2.7 MeV/c2

= 67.7 ±

20.3 ±

7.7 MeV/c2

45

X(1835) at

BESIIIBESIII

Phys. Rev. Lett, 106, 072002 (2011).

X(1835) + 2 new peaks

Fit with four resonances (f1

(1510) + 3 higher mass)

Mass (MeV/c2 ) Width (MeV/c2) Significance

X(1835) > 20 σ

X(2120) 7.2 σ

X(2370) 6.4 σ

6.51.20.35.1836

7.47.27.64.2122

2.33.47.83.2376

38369190

31111683

4461783

X(1835) consistent with 0-+, others not excluded.

f1

(1510)

46

J/ BESIII

Phys. Rev. Lett. 107, 182001 (2011).

M(ao

(980)) M() –

non ao

(980)

a2

(1320)±

J/

X,X ao

±(980)

∓, ao

±(980) ±

47

Phys. Rev. Lett. 107, 182001 (2011).

f1

(1285)(1405)X(1870)

J/ X, X

ao±(980)

∓

BESIII

B(J/

X, X ao±(980)

∓)

• Select M(in ao

(980)region.• See X(1870) –

7.2

•

Same as X(1835), (1870), or both?• Need PWA.

Phys. Rev. Lett. 107, 182001 (2011).

48Other J/

decays

49

J/ 3π

decays Study J/ π+π-πo

and πoπoπo using 225 M J/

decays

3π

'

3π

(1405)

fo

(980)π0

• (1405) couples mainly to ao

(980)π

and KKπ•

fo

(980) controversial: scalar meson, tetra-quark, hybrid, or KK molecule?• ‘

3π

decays probe isospin

breaking.

BESIII

BESIII, accepted by PRL, arXiv:1201.2737

50

'

3π

in J/ 3π

decays

J/ π+π-πo

J/ πoπoπo

B(‘

π+π-π0) = (3.83 ±

0.15 ±

0.39) x 10-3

PDG2010: (3.6+1.1

-0.9

) x 10-3

(2009 CLEOc)

B(‘

3π0) = (3.56 ±

0.22 ±

0.34) x 10-3

PDG2010: (1.68 ±

0.22) x 10-3

(1984 GAM2)

BESIII

BESIII, accepted by PRL, arXiv:1201.2737

51

'

3π

in J/ 3π

decays

r±

= B(‘

π+π-π0)/B(‘

π+π-) = (8.87 ±

0.98) x 10-3

r0

= B(‘

3π0)/B(‘

π0π0) = (16.41 ±

1.94) x 10-3

•

Ratios are related to strange quark mass and SU(3) symmetry breaking. D.J. Gross, S.B. Treiman, and F. Wilczek, Phys. Rev. D19, 2188 (1979).

•

Values more than 4σ

from both π0-

mixing predictions and chiral

unitary framework prediciton. B. Borasoy etal.,

Phys Lett. B643,41 (2006).

BESIII

BESIII, accepted by PRL, arXiv:1201.2737

52

Anomalous fo

(980) in J/ fo

π0BESIII

Fitted mass:M = 989.9 ±

0.4 MeV/c2

Γ

= 9.5 ±

1.1 MeV/c2

Width very narrow!PDG2010:

Γ

= 40 –

100 MeV/c2

BESIII, accepted by PRL, arXiv:1201.2737

53

(1405) in J/ fo

(980)

π0

BESIIIBESIIIfo

(980) π+π- fo

(980) π0π0f1

(1285)4.8σ

f1

(1285)1.4σ

Helicity

analysis indicates peak at 1400 MeV/c2

from (1405), not from f1

(1420).B(J/ (1405) fo

π0

π+π-π0)= (1.48 ±

0.13 ±

0.17) x 10-5

B(J/ (1405) fo

π0

π0π0π0)= (6.99 ±

0.93 ±

0.95) x 10-5

1st observation of (1405)

fo

(980)π0

and J/ fo

(980)π0BESIII, accepted by PRL, arXiv:1201.2737

Isospin

violating decay

(1405) (1405)

54

(1405) in J/ fo

(980)

π0

BESIIIBESIIILarge isospin

violation:

For comparison:

J.J. Wu etal.,arXiv:1108.3772

K*K pair in TS almost on-shell, together with mixing explain narrow fo

(980) and large isospin

violation. Mixing by itself too small.

BESIII, accepted by PRL, arXiv:1201.2737

55

The old

puzzle

B(J/ ) =

B(' ) =

BESIII:

56

The old

puzzle

57

Charm Physics

58

Charm Physics•

BESIII has accumulated 2.9 fb-1

at the ψ(3770).•

Peak luminosity 0.65 x 1033

cm-2

s-1.•

Accumulated 480 pb-1 at 4010 MeV.

•

ψ(3770): quantum coherent DD-bar pairs. Ideal for mixing and CP violation studies.

•

Threshold production very clean.•

Double tagging techniques important. Useful for semi-leptonic

decays. Can determine absolute

branching fractions.•

First results will be reported at CHARM2012.

5959

Clean single tag at BESIII

D0K D+K

D0K D0K

BESIIIPreliminary

BESIIIPreliminary

BESIIIPreliminary

BESIIIPreliminary

@(3770) with 420pb1 first clean single tagging sample:

2 2| |BC beam DM E p

Resolution: 1.3 MeVfor pure charged modes;1.9 MeV

for modeswith one .

60

61Beam Energy Measurement

62

•

Tau

Mass status:–

KEDR: Most precise:

–

Consistent with BES 1996:

•

PDG (2008): 1776.84 ±

0.17 MeV

•

KEDR used two methods to calibrate beam energies:–

Resonant spin depolarization technique (<~30 KeV)–

Compton back scattering (<~60 KeV) to be used by BESIII–

Also measured masses of J/ψ, ψ(2S), ψ(3770)

ARGUS 1992

BES 1996

CLEO 1997

OPAL 2000

KEDR 2007

KEDR 2008

BABAR 2008

BELLE 2007

mτ - 1777, MeV

1

2

3

4

5

6

7

8

-4 -3 -2 -1 0 1 2 3

M

= 1776.96 MeV+0.18 + 0.25‐0.21 – 0.17

Nucl. Phys. B (Proc. Suppl.) 181-182, 311 (2008).PLB573, 63 (2003).

Tau

mass measurements

MeV ..M KEDRτ 150691776 17.0

19.0

63

Importance of

Mass

Measurement•

M() is fundamental parameter of SM.

•

M(e) and M(μ) are known to δM/M ~ 10-8 while M() is only known ~ 10-4.

•

Improved precision important to test universality:

•

At present:

)1)(1(),(),(

)()(

52

W

e

e

mmFmmF

eBeB

mm

gg

0022.00006.1

gg

Tests universality at 0.2% level.

A. Pich, arXiv0711.0028 (2007).

64

BESIII Beam Energy Measurement•

BESIII can improve

mass measurement but precision is limited by knowledge of beam energy.

•

Use BINP method: measure energies of back scattered Compton photons produced by a CO2 laser beams on both the e+ and e-

beams:1.

Beam energy

determined by max energy (ωmax

) of back scattered photons:

where ω0 is laser photon energy.2. Back scattered photons measured with High Purity Ge

(HPGe) detector with precision of δ/

~ 1 x 10-5.3. Absolute calibration of energy scale done using -active

radionuclides.4. Expected resolution at BESIII ∆

= 50 keV.

max0

2max 112

em

measured at VEPP-4M

∆

m

< 0.1 MeV/c2

;

PDG08, ∆

m

≈

0.16 MeV/c2

65

BESIII Beam Energy Measurement•First BESIII upgrade.•Collaboration by IHEP, BINP, and U. of Hawaii.•Scheme:

λ

= 10.835 μm (0.114 eV)System complete.

66

BESIII Beam Energy Measurement

Supplied by U. of Hawaii

67

BESIII Beam Energy Measurement

Laser beamphotons

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BEMS Performance

Accuracy determined by comparison of ‘

mass with value with that determined using BEMS. ~4 pb-1

in 2010

M = M'

– MBEMS= 1 ± 72 keVM/2= 1 ± 36 keV

Accuracy of BEMS= 2 x 10-5

Accuracy consistent with design.

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Summary•

BEPCII/BESIII completed successfully: –

Peak Luminosity of 6.5*1032

achieved.–

106 M ψ(2S) and 226 M J/ψ events obtained in 2009.

–

~940 pb-1 obtained at ψ(3770) in 2010.–

~2 fb-1 obtained at ψ(3770) and 480 pb-1

at 4010 MeV

in 2011.

•

Many exciting results with much, much more to come.•

Rich physics after CLEOc.

•

BES is unique.

Backup Slides

CM Energy ranges from 2 to 5 GeVLuminosity at J/ ~ 5 x 1030 cm–2 s -1

Beijing, China

BESII

The Beijing Electron Positron Collider

(BEPC)

BESII detector removed in 2004.

CLEO-cLate comer

to tau

–

charm energy region.

•

Lowered CESR CM energy in 2003 to run in tau-

charm region.

•

Stopped in 2008.

•

Peak luminosity ~0.6 x 1032 pb-1 s-1.

•

Luminosity at ψ(3770) ~800

pb-1.

•

ψ’: ~25 M.

•

Well understood, state of the art detector.

•

But BESIII has a comparable detector and higher luminosity. Future belongs to BESIII.

7373

BESIII DetectorBerylium

beam pipeSmall-celled, helium-based MDC:

|cos

θ| < 0.83 (all 43 layers), < 0.93 (20 layers)σp

/p

= 0.58 % at 1 GeV/c; dE/dx

resol

= 6% at 1 GeV/c

(hadron)TOF (2 layers in barrel; 1 layer endcap)

σT = 80 ps

barrel (Bhabha); σT = 100 ps

endcapCsI

electromagnetic calorimetercrystal length: 28 cm (15 X0

)energy: 2.5%, space 0.6 cm at 1 GeV

Superconducting Magnet –

1 TMuon

Counter9 layers of RPCs

in barrel; 8 in endcap

For details, see “BEPCII and BESIII”,Int. J. Mod. Phys. A24, 377 (2009).“Design and Construction of the BESIIIDetector”, NIM A614, 345 (2010).

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Study of

cJ

VV,

V =

Previous measurements from BESII.

BR(10‐3) c0 c2 0.940.21±0.13 1.700.30±0.25

2.29±0.58±0.41 1.770.47±0.36

BESII, PLB 642, 197 (2006)

BESII, PLB 630, 7 (2005)

cJ

and

cJ

are Singly OZI suppressed

c1

VV

suppressed by helicity

selection rule.

cJ

is doubly OZI suppressed, not yet seen.