slac experimental seminar april 3, 2012fah/bestalks/slac_besiiitalk_harris_2012j.pdf3. physics of...
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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
68
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.
69
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).
74
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.