Post on 12-Aug-2020
Frederick A. HarrisFrederick A. HarrisUniversity of HawaiiUniversity of Hawaii
Jan. 5, 2005Jan. 5, 2005
e+ e- physics in the tau – charm energy region
Part I
OUTLINEIntroduction
Oldies but goodiesτ mass measurement and R scan
ψ(2S) scan and radiative and hadronic transitions:ψ(2S) → γγJ/ψ, XJ/ψ
12% Rule and ρπ puzzleψ(2S) → VT and VP
ηC parameters
Summary
The Beijing Electron Positron Collider
L ~ ~5 ×1030 /cm2⋅sat J/ψ peak
Ecm~2-5 GeV
A unique e+e- machinein the τ-charm energyregion from 1989 –
2003.
Beijing, China
BESII Detector
VC: σxy = 100 μm TOF: σT = 180 ps μ counter: σrφ= 3 cm MDC: σxy = 220 μm BSC: ΔE/√E= 22 % σz = 5.5 cm
σdE/dx= 8.5 % σφ = 7.9 mr B field: 0.4 TΔp/p=1.7√(1+p2) σz = 2.3 cm
CLEO-cNew comer to tau – charm energy region.
• Ran at ψ" in 2003 with 6 wigglers (~60 pb-1).
• Running now with all 12.
Luminosity ~0.6 x 1032
pb-1 s-1
• Luminosity expected ~2 x 1032 pb-1 s-1
• 300 pb-1 at ψ" this year?
• Have well understood, state of the art detector.
n 2S+1 L J
Charmonium spectrum below open charm
Charm thresholdψ(3770)
World J/ψ and ψ(2S) Samples (×106)
J/ψ ψ(2S)
0
10
20
30
40
50
60
MarkIII DM2 BESI BESII0
2
4
6
8
10
12
14
MKI MKII MKIII CBAL BESI BESII CLEO
58 M 14 M
Oldies but goodies
Tau mass measurement
• Use e+ + e- →τ+ τ- → e e, e μ, e h, μ μ, μ h, and h h events (+ 4 ν’s). h = π or K
• Use PID plus cuts on kinematic variables.• Fit threshold excitation over 12 scan points • 5 pb-1 of data.
Tau mass measurement• BES measurement:
• 10X better precision
225.018.017.021.0 MeV/c96.1776 ++
−−=τm
J. Z. Bai et al, PRD53, 20 (1996).
Tau mass measurementLeptonic decay rate in SM:
For muon decay, mμ, tμ, and Fcor are used to determine GF
For tau:
Lifetime, leptonic branching ratio, and mass related.
Was poorly satisfied before BES measurement.
),(192
) ( cor3
52
lLLL
lL mmFmGlLπ
νν =→Γ
τ
ννττννττ νντ
tB
Be eee
→→ =Γ=→Γ ) (
(Fcor ~ 1)
μμ ννμ
te e
1) ( =→Γ
Tau mass measurement• Lifetime, leptonic branching ratio, and mass:
Status 1992 (2.4 σ)
and 1994 (1.3 σ)
Status 2000
A. Pich, hep-ph0012297
1992
Tau mass measurementTest lepton universality:
Value should be ~1 if universality holds.
0085.09886.0)( 2 ±=→
→
ννμ
νντ
e
e
GG
0051.00020.1)( 2 ±=→
→
ννμ
νντ
e
e
GG
using PDG2004
Tests universality at ½% level.
With new mτ - 1996
Novosibirsk planning a new tau mass measurement.
R MeasurementR Measurement
PDG2000 – Selected measurements
R provides strong
evidence for the quark
model and 3 colors.
For u, d, s
R ≈ 2
For u, d, s, c
R ≈ 3 1/3
For u, d, s, c, b
R ≈ 3 2/3
R MeasurementR Measurement
Improved R values are very important:
Needed for interpretation
of aμ = (g – 2)/2.
Much of the theoretical
uncertainty from
R - but mostly from
ECM < 2 GeV region.
M. Davier et al., Eur. Phys. J. C31,
503 (2003).
1.9 σ0.7 σ
R measurementR measurementNeeded to improve precision of α(M2
Z):
Uncertainties in α introduced when it is extrapolated to the Z-pole:
Dominant uncertainty due to hadronic vacuum polarization.
This is determined from R values using a dispersion relation.
R measurementR measurementThe Higgs mass determined from radiative corrections in the SM is very sensitive to α(M2
Z).
B. Pietrzyk and H.
Burkhardt (1997).
BES R MeasurementBES R MeasurementDetermination of R:
Runs
~1000 events per energy point
BES R-scan
Results published: J.Z. Bai et.al., Phys. Rev. Lett. 84, 594 (2000).J.Z. Bai et.al., Phys. Rev. Lett. 88, 101802 (2002).59 + 106 citations so far; tau mass paper - 67
BES R MeasurementBES R MeasurementBES Results (continued).
R Below 10 GeV
Before BES R Scan After BES R Scan
BES reduces R errors from 15 – 20 % to an average of 6% in the 2 – 5 GeV region. Important region!
Current StatusBurkhardt and Pietryzk have updated analysis
[Phys. Lett. B513, 46 (2001).]
Error about half previous error.
Shifts Standard Model Higgs mass upward.
Data driven approach:
data for E < 12 GeV
The SM Fit to mH
GeVmGeVm
H
H
17062 53
30
<= +
−
(95% C.L.) GeVmGeVm
H
H
21298 58
38
<= +
−
Without BES dataWith BES data
(95% C.L.)
The Latest SM Fit to mH
GeVmGeVm
H
H
17062 53
30
<= +
−
(95% C.L.) GeVm
GeVm
H
H
260
114 6945
<
= +−
(95% C.L.)
Without BES data
With BES data
Thanks to B. Pietrzyk
In 2004 with new top mass
ψ(2S) scan and radiative and
hadronic transitions
ψ(2S) Scanψ(2S) ScanPurpose: Improve accuracies of ψ(2S) parameters: Γ, Γh, Γμ, Γππ J/ψ,
B(h), B(μ), and B(π+ π- J/ψ).
Ψ(2S) → μ+ μ- and Ψ(2S) → π+ π- J/ψ are importantfor identifying Ψ(2S) decays in B-factory and otherexperiments.
Scanned 24 energy points from 3.67 and 3.71 GeV.Integrated luminosity = 1150 nb-1
Four channels: ψ(2S)→ hadrons, μ+ μ-, e+ e-, and π+π- J/ψ
Fitting
• Fit observed σh(W), σππ J/ψ(W), σe(W), and σμ(W).• Include resonance and continuum production plus
interference, beam spread (Δ), ISR and FSR.• Assume Γe = Γμ = Γτ /0.3885, Γt = Γh + Γμ + Γe + Γτ.
• Determine Γh, Γμ, Γππ J/ψ, M(ψ(2S)), Δ, and R.• Results:
– R = 2.15 ± 0.17 consistent with BES R measurement (R = 2.25 ± 0.06 at 3.55 GeV).
– Δ = 1.298 ± 0.007 MeV. Agrees with expected beam spread.
Fitting Result
Parameter BES MARK I PDG2002264 ± 27(10.1 %) 228 ± 56 (24.6 %) 300 ± 25 (8.3 %)
258 ± 26(10.1 %) 224 ± 56 (25.0 %)
85.4 ± 8.7 (10.1 %)
2.44 ± 0.21 (8.8 %) 2.1 ± 0.3 (14.29 %) 2.19 ±0.15 (6.8 %)
97.8 ± 0.15 (0.16 %) 98.1±0.3 (0.31 %) 98.10 ±0.30 (0.31 %)
32.3 ± 1.4 (4.4 %) 32 ± 4 (12.5 %) 30.5 ± 1.6 ( 5.2 %)
0.93 ± 0.08 (8.5 %) 0.93 ±0.16(17.2 %) 0.7 ±0.09(12.9 %)
(keV)tΓ
(keV)hΓ(keV)ψππ JΓ
(keV)μΓ(%)hB
(%)ψππ JB(%)μB
Phys. Phys. LettLett. B550, 24 (2002). B550, 24 (2002)
Measure:ψ' → πoJ/ψ, ηJ/ψ
ψ'→ γ χcJ → γ γ J/ψ (J=1,2)• Old measurements disagree.• B(ψ’ → πoJ/ψ) very crude:
(23 evts at CBAL, 7 evts at MRK2).• Theoretical predictions for charmonium hadronic
transition amplitudes can be tested by high statistics measurements.
ψ'→ γ γ J/ψ
ηJ/ψ
πoJ/ψ
γ χcJ → γ γ J/ψ
ψ'→ γ γ J/ψ
BKG from πoπoJ/ψ
J/ψ ee or μμ, 5C (J/ψ mass) kinematic fit is applied!
ψ(2S) → ηJ/ψ
ψ'→ γ γ J/ψψ(2S) → πoJ/ψ
γ γ ee
γ γ ee
γ γ ee
γ γ μμ
γ γ μμγ γ μμ
ψ (2S) → γχcJ → γ γ J/ψ
ψ (2S) → γχcJ → γ γ J/ψ
ψ'→ γ γ J/ψ
PDG04 2.67 ± 0.15 1.30 ± 0.08
ψ'→ γ γ J/ψ
πoJ/ψ
ηJ/ψ
γ χc1
γ χc2
BES measures the BRswith high precision!
BES
Phys.Rev.D70:012006,2004
BES most
accurate
ψ'→ γ γ J/ψ
• PCAC [G. A. Miller, Phys. Rep. 194,1(1990)]: R=0.0162 (too small!)
BES (+PDG for ϒ):
R= 0.048 ± 0.007R' < 0.0098R" < 0.0065
• QCD Multipole expansion & BTG potential model[Y. P. Kuang, PRD24, 2874(1981), ibid. 37, 1210(1988)]
R' = 0.0025R" = 0.0013
ψ' → X J/ψB(ψ(2S) → hadrons)/B(J/ψ → hadrons) =
B(ψ(2S) → ggg + ggγ)/B(J/ψ → ggg + ggγ)
= 0.23 ± 0.07
Disagrees with “12 % Rule”
Important to measure ψ’ → X J/ψ and
components.
M. Suzuki, PRD63,
054021, (2001).
Y. F. Gu and X. H. Li,
PRD63, 114019 (2001).
Method – identify J/ψ → μ+μ-
Select muons.
1 C fit to mJ/ψ
determine mX
pX
p μ-p μ+ pJ/ψ
ψ' → X J/ψ
J/ψ peak
Background
e+ e- → γ μ+ μ- and
e+ e- → ψ’ → γ μ+ μ-
Fit distribution:
• background (mμμ < 3.4)
1307 events
• signal 44498 events
Inclusive measurement – use events that satisfy 1 C fit.
ψ' → X J/ψTo separate ψ’ → π0π0 J/ψ and π0π0 J/ψ, plot mX for
no extra charged tracks and for extra charged tracks.
Fit two simultaneously with component shapes.
ππ
η
χc1χc2backgrd
no extra extraππ
η
χ2 < 7
Exclusive measurements
ψ' → X J/ψ
Results
Phys.Rev.D70:012003,2004
measured
BESI – 4 million ψ(2S) events.
Determine ratio of branching ratios to
B(ψ’ → π+ π- J/ψ ) to cancel systematic errors.
Constrain χC2/χc1 since shapes similar.
CLEOc results on ψ(2S) transitions
and radiative decays
From talk by Brian Heltsley at the Third Quarkonium
Working Group Meeting, Beijing, Oct. 12 – 15, 2004.
(www.qwg.to.infn.it)
• Measure inclusive and exclusive.
• 3.1 M (± 3 %) ψ(2S) decays
• Fully reconstruct events
• J/ψ → μμ, ee
• η → γγ, π+ π- π0
• Preliminary
CLEOc ψ(2S) inclusive gamma spectrum
cJS χγψ →)2(
Good calorimeter allows measurement of inclusive spectrum.
Can determine B( ).
Higher than PDG? Yes.cJS χγψ →)2(
(www.qwg.to.infn.it)
12% Rule and ρπ Puzzle
pQCD 12% rule :T. Appelquist & H.D. Politzer, PRL 34 (1975) 43A. De Rujula & S.L. Glashow, PRL 34 (1975) 46
• J/Ψ and Ψ’ hadronic decays proceed via 3 gluons or a virtual photon.cc annihilation → decay rate ~ |ψ(0)|2
• Complications:αS correctionsRelativistic correctionsInterference with continuum (See talk by C.Z. Yuan at 2nd QWG meeting)Etc.
• Take as “Rule of thumb”
12% Rule and ρπ puzzle
12%
eeJ/ψB
eeψ'B
XJ/ψBXψ'B
hQ =−+→
−+→=→
→=
strong electromagnetic non-resonant
ψ(2S) signal continuum
(www.qwg.to.infn.it)
12% Rule and ρπ puzzle
ρπ puzzle:
• Suppression in VP mode (ρπ & K*K ) revealed by MARK-II { M.E.B. Franklin et al, PRL 51 (1983) 963 }
Q(ρπ) < 0.6% Q(K*K) < 2 %
• Suppression confirmed by BESI with higher sensitivity
• Suppression in VT mode found by BESI{ J. Z. Bai et al, PRL 81 (1998) 5080 }
Q(ωf2) < 4.0%, Q(ρa2)< 2.1%, Q(K*K*2) < 1.8%, Q(φf2
’) < 3.7%
Theoretical explanations:Brodsky, Lepage, Tuan: {PRL 59 (1987) 621 } Intermediate vector glueballChaichian & Torngvist : {NP B323 (1989) 75 } Hadronic form factor Pinsky : {PL B236 (1990) 479 } Generalized hindered M1 transitionLi-Bugg-Zou {PR D55 (1997) 1421 } Final-state interactionBrodsky-Karliner {PRL 78 (1997) 4 Intrinsic charm |qqcc> Fock components of
the light vector mesonsChen-Braaten {PRL 80 (1998) 5060 } Fock state with cc pair in a color-octet
Gerard-Weyers {PL B462 (1999) 324 } cc annihilation into 5g via 2 steps
Feldmann-Kroll {PR D62 (2000) 074006 } Decays thru light-quark Fock component by a soft mechanism
Suzuki {PR D63 (2001) 054021 } ψ(2S) - vector glueball mixing
Rosner {PR D64 (2001) 094002 } ψ(2S) - ψ(1D) mixing
J. P. Ma {PR D65 (2002) 097506 } Relativistic Correction
12% Rule and ρπ puzzle
Many ruled out. Still interesting: ψ(2S) - ψ(1D) mixing.
Ψ(2S) → V T ω f2 ↓ ↓
π+π–π0 π+π–
ρ a2 ↓
↓ ρ π↓ ↓ππ ππ
K* K*2
↓ ↓Kπ Kπ
φ f2'
↓ ↓K+K– KK
π+ π– π+ π– π0↓
γ γ
K+ K– π + π –
⇒
⇒
⇒
⇒
Ψ(2S)π+ π– π+ π– π0
↓γ γ
K+ K– K + K –
)1270(2fω
Ψ(2S) → V T
f2 (1270)
B.G.(M.C.)
B.G.( σ )
)1320(2aρ
a2 (1320)
First observation
BESII14 million ψ(2S) events
..)1430()892( 20 cc+ΚΚ ∗∗
Ψ(2S) → V T
B.G.
K*2 (1430)
K*(892)
)1525(2f ′φ
f0(980)f2
' (1525)
First observations
BESII
Ψ(2S) → V T
MCYXS
obsYXS
XS Nn
εψ
ψψ ⋅⋅
=→
→→
→ BB
)2(
)2()2(
VT mode
Bψ(2S) →X (10 – 4)(BES-II)
B J/ψ→X (10 – 3)(PDG2002)
Qh(%)
4.3±0.6 4.8±1.5
2.3±1.1
2.4±1.2
3.9±1.6
10.9±2.2
6.7±2.6
1.23±0.06±0.20†
ω f22.05± 0.41 ±
0.46ρ a2 2.55± 0.73± 0.60
K* K*2
1.64± 0.33 ±0.41
φ f2' 0.48 ± 0.14 ±
0.12† This value from DM2 only
Suppressed!!12 % rule ( pQCD rule )Phys.Rev.D69:072001,2004
BESII
BESII Preliminary
VP Mode ρ π
Dalitz plot for J/Ψ and Ψ(2S) → 3π are very different
J/ Ψ → 3πΨ(2S) → 3π
PRD70 (2004) 012005
Mππ in Ψ(2S) → 3π
ρ(770), ρ(2150) -- dominantBESII Preliminary( PWA )
VP Mode
ρ π
Results on BRs____________________________________________________________________________________________________________________________________________
BR BESII (10 – 5 ) PDG04 (10 – 5 )
Ψ(2S) → π+π-π0 18.1 ± 1.8 ± 1.9 8 ± 5
Ψ(2S) → ρ π 5.1 ± 0.7 ± 0.8 < 8.3
Ψ(2S) →
ρ(2150) π → π+ π- π0 19.4 ± 2.5____________________________________________________________________________________________________________________________________________
BESII Preliminary( PWA )
VP Mode ρ π
2.111.2
+−
hep-ex/0408047 submitted to PRL
Should help the understanding of the ρπ puzzle.
ψ (2S)→ K*(892)K + c.c. → KSKπKS →π+ π-
VP Mode
K*0
K*±
Ψ(2S) → K*±(892) K+ Ψ(2S) → K*0(892) K 0
K*(892)KVP Mode
Br±(2.9±1.3±0.4)×10 –5 Br0(15.0±2.1±1.9)×10 –5
K*±K*0
= 5.2±2.7
65.6±9.0 Evts.
Large isospin-violation
9.6±4.2 Evts.
)( 0 mπKM )( mπ±KM
hep-ex/0407037 , submitted to PRL
ψ’→ Nevt B(ψ’) (×10-5) B(J/ψ) (×10-4)PDG04
Q (%)
ρ (770) π 5.1 ± 0.7 ± 0.8 127 ± 9 0.40 ±0.08ρ (2150) π
ρ η 13.2 ± 4.8 1.78 ± 0.65 ± 0.22 1.93 ± 0.23 9.2 ± 3.7
ρ η’ 2.5 ± 1.7 1.87 ± 1.27 ± 0.36 1.05 ± 0.18 17.8 ± 12.9
ω π 14.0 ±4.8 1.88 ± 0.64 ± 0.32 4.2 ± 0.6 4.5 ± 1.8
ω η <3.3 < 1.1 15.8 ± 1.6 < 0.7
ω η’ 4.1 ±2.8 4.3 ± 2.9 ± 1.0 1.67 ± 0.25 26 ± 19
ϕ π < 3.0 < 0.3 < 0.068
ϕ η 17.8 ± 5.3 3.5 ± 1.0 ± 0.6 6.5 ± 0.7 5.4 ± 1.9
ϕ η’ 9.1 ± 3.6 3.2 ± 1.3 ± 0.6 3.3 ± 0.4 9.7 ± 4.5
K+K*-+c.c. 9.6 ± 4.2 2.9 ± 1.3 ± 0.4 50 ± 4 0.58 ± 0.27
K0K*0+c.c. 65.6 ± 9.0 15.0 ± 2.1 ± 1.9 42 ± 4 3.6 ± 0.8
* PreliminaryUpper limit @90% C.L. Results of VP mode
2.111.25.24.19 +
−±
BESII Preliminary
Test of pQCD
12% Rule
Results
12% Rule to naive
Even more BES
BESII preliminary
Test of pQCD
12% Rule
CLEOc ResultsTalk by Brain Heltsley at Third
Quarkonium Workshop, Oct. 2004. ( www.qwg.to.infn.it )
• ~3 million ψ(2S) events
• continuum data: 20.46 pb-1
(BES 6.42 pb-1)
• CLEOc subtracts continuum without considering interference.
• For ρπ, no PWA. Just use ρ(770) peak. Neglect interference.
CLEOc Results
Upper limit @90% C.L. BESII vs. CLEO (ψ’ BRs Results) BESII Preliminary
• Most channelsBRs are consistent.
• BES BR(ρπ) > CLEO by ~ 3σ,
because PWAtakes into acount theinterference.
• BR(K*0K0) aredeviated
CLEO BRs calculated from hep-ex/0407028
12% Rule and ρπ puzzle
• There are many new measurements from BES and
CLEOC.
• Agreement is good, especially if differences
in continuum subtraction taken into consideration.
• These should help to explain the ρπ puzzle.
ηc parameters
ηc ParametersPrecise (mJ⁄ψ - mηc) needed for potential models.But ηc mass not well determined: PDG02 CL = 0.001
Width Measurements
Values spread all over with large errors.
M(pp)
J/ψ→γ ηC , ηC →pp
ηC measurements with BESII 58 M J/ψ sample
M(K+K-π+π-) M(π+π- π+π-)
M(K+/- K0Sπ-/+)
M(φφ)
J/ψ→ γηC , ηC → K+ K- π+ π- J/ψ→ γηC , ηC → π+ π- π+ π-
J/ψ→ γηC , ηC → K KS π J/ψ→ γηC , ηC → φ φ
Results: Mass and WidthResults: Mass and WidthCombined fit of five channels:
M(ηC) = 2977.5 ± 1.0 ± 1.2 MeV/c2
Γ(ηC) = 17.0 ± 3.7 ± 7.4 MeV/c2
PDG
M(ηC) = 2979.7 ± 1.5 MeV
Γ(ηC) = 16.0 +3.6-3.2 MeV
Phys. Phys. LettLett. B555, 174 (2003). B555, 174 (2003)
Results: Mass and WidthResults: Mass and Width
PDG2004
BES2003BaBar BaBar
BaBar Γ = 34.3 ± 2.3 ± 0.9 MeV/c2
γγ production – 88 fb-1 of data
hep-ex/0311038,
Phys. Rev. Lett. 92: 142002 (2004).
Results: Branching Fractions
SystematicErrors
Product BranchingFractions
Results: Branching FractionsResults: Branching FractionsDividing by B(J/ψ → γ ηc ) = 1.3 ± 0.4 % (PDG2002)
† H.C. Huang et al., hep-ex/0305068
* Calculated from results in F. Fang, et al., PRL 90:071801,2003.
B(ηc → φ φ) is smaller than PDG and agrees with Belle
measurement (hep-ex/0305068).
Physics Letter B578, 16 (2003).
*
†
*
Summary
BES has
• Made fundamental measurements of the τ mass and R in the 2-5 GeV energy region. Important for testing lepton universality and the SM.
• Improved ψ(2S) parameters from a ψ(2S) scan and measurements of radiative and hadronic transitions.
ψ(2S) → π0 J/ψ, η J/ψ, π0π0 J/ψ, γχcJ, and anything J/ψ.
• Measurements for BRs of ψ(2S) → VP channels: ψ(2S) → (ρ,ω,ϕ)(π,η,η’), K*Ko In ψ(2S) → 3π, ρ(770) & ρ(2150) dominant.o Large isospin-violation in ψ(2S) → KK* channel.o Results agree well with CLEOc.
• Measured ηC mass, width, and branching ratios.
Thanks