R Group Working ReportR Group Working Report
Haiming HuRepresenting R Group
BES Annual Shanxi, May. 23-26, 2004
OutlineR&QCD data takinge+ e- →proton-antiproton cross section e+ e- →+-+- form factorThe fit of the excited ψ-family resonant parameters Conclusions/Perspectives
R and QCD
R98 and R99 results
Comments on the Rexp and RQCD
☻ Deviate about 1σ in wide region 2.2-2.7GeV.
Systematic Error? Hitting the new physics?
☺ Central values of Rexp and RQCD coincide at 2.0, 2.8-3.2GeV.
Due to error? True agreement ?
Ecm (GeV) Rexp
2.2 2.38±0.07±0.17
2.6 2.38±0.06±0.15
3.0 2.21±0.05±0.11
R&QCD Data Taking
In general, the R&QCD data quality is good.
Ecm Run
Luminosity Handron
2.22 ~64 nb–1 34900
2.60 ~1244 nb–10 24900
3.07 ~ 2310 nb–10 1500Jan
.3 –
Feb
. 7
2004
Analysis by the programs
of R99 measurement
Data quality check
Jin Yi’s report
The cross section of eThe cross section of e+ + ee- - ++--++- - ①22Yuan Jianming Tong Guoliang Hu Haiming
The measurement of hadronic form factor may promote the understand to strong interaction, which give the expression to electro-magnetic
vertex with influence of the strong interaction. For the process ee++ e e-- ++--++--
The cross section and the Form factor measured by CDM,ND, DM2, OLYA groups between 1-2 GeV
The cross section of eThe cross section of e+ + ee- - ++--++- - ②
Event selection Back-ground analysis
Cross section
The cross section of eThe cross section of e+ + ee- - ++--++- - ③
Two analysis have been done with reconstructed R scan data by V101 and then V103 respectively, the number of events from V103 is consist with V101 exceptat energy points 2.9 and 3.0 GeV.
The efficiencies estimated by SIMBES are lower about 40% than by BOSER, The cross section are about 1.6 to 2.0 times as large as former.
The cross sections and the form factors measured using SOBER/SIMBES seems consistent/not consistent with the low energy experiments by other groups. But more check and analysis have to do.
The cross section of eThe cross section of e+ + ee- - ++--++- - ④
BES V101& SOBER
BES V103& SIMBES
Cross section
Form factor
Cross section
Can not fit the theory by V103 andSIMBES results together with the low energy experiments, they are notconsistent with each other obviously.
The EM form factor of proton
Li Huihong
The Conserved Vector Current – SU(2)
hadrons
W hadrons
e+
e–
CVC: I =1 & V W: I =1 & V,A : I =0,1 & V
Hadronic physics factorizes in Spectral Functions:
Isospin symmetry (CVC) connects I=1 e+e– cross section to vector spectral functions:
2( 1) 04I e e
s
0
0
0 20
22 2
BR 1
BR 1 / 1 /e
dN m
N dse s m s m
branching Fractions mass spectrum kinematic factor (PS)
fundamental ingredient relating long distance (resonances) to short distance description (QCD)
The fit of the excited ψ-family resonant parameters ①
Hu Haiming Huang Guangshun
The 4 excited -family resonant Structure was scanned in 1999.
The fit of the excited ψ-family resonant parameters ②
The resonant parameters were fitted in 2002, the preliminary results were reported at BES Anuual02. The memo about the parameter fit
has submitted to BES Collaboration, and some reviews came .
The preliminary results at BES02 The fit result by K.K.Scth hep-ex/0405007
A simple BG and constant width was assumed. The two experiments by CB and BES are in good agreement
The fit of the excited ψ-family resonant parameters ③
Fit R values iteratively, the polynomial and QCD BG forms were used
Fit R values iteratively, the polynomial and QCD BG forms were used
Fit the observed cross section, the DASP type BG form was used
Fit the observed cross section, the DASP type BG form was used
The fit of the excited ψ-family resonant parameters ④
Main review from the BES referees
The problem about the reliable QED backgrounds form used
DASP type polynomial form QCD-like form
The problem about the correct energy-dependent hadronic width for the wide resonance.
AT BES02 report, a form of the total width derived from potential model of quantum mechanics was used
Eichten model predicts the decay channels:
The fit of the excited ψ-family resonant parameters ⑤
Some attempts to meet referee’s requests
The continuum backgrounds form based on QCD and Lund area law
The lowest cross section for the exclusive channel
The QED cross section for quark pair production
The string fragmentation probability in Lund area law
The fit of the excited ψ-family resonant parameters ⑥
Some attempts to meet referee’s requests
Energy-dependent hadronic width
The effective interaction theory was used
Interaction matrix element:
The decay types concerned:
The interactive Hamiton: Hadronic decay width:
The fit of the excited ψ-family resonant parameters ⑦
Some attempts to meet referee’s requests
The running mass parameter
means the principal value of integral
The fit of the excited ψ-family resonant parameters ⑧
Some attempts to meet referee’s requests
The comparison between experiment and theory/model
The parameters were putted by hand, i.e. not fit yet
Continuum QCD BGwith u,d,s qurks: RQCD(u,d,s)
Continuum two-body BGfrom e+e-→DD’
Continuum three-body BG
from e+e-→DMD’
Total continuum GB
R value by theory & model
R value by experiment
e+e – Radiative Corrections
Multiple radiative corrections are applied on measured e+e – cross sections
Situation often unclear: whether or not - and if - which corrections were applied
Vacuum polarization (VP) in the photon propagator:
leptonic VP in general corrected for
hadronic VP correction not applied, but for CMD-2 (in principle: iterative proc.)
Final state radiation (FSR) [we need e+e
– hadrons () in disper-sion integral]
usually, experiments obtain bare cross section so that FSR has to be added “by hand”; done for CMD-2, (supposedly) not done for others
Initial state radiation (ISR)
corrected by experiments
2002 Analysis of ahad
Motivation for new work:
New high precision e+e – results (0.6% sys.
error) around from CMD-2 (Novosibirsk)
New results from ALEPH using full LEP1 statistics
New R results from BES between 2 and 5 GeV
New theoretical analysis of SU(2) breaking
Cirigliano-Ecker-NeufeldJHEP 0208 (2002) 002
ALEPH CONF 2002-19
CMD-2 PL B527, 161 (2002)
Outline of the 2002 analysis:
Include all new Novisibirsk (CMD-2, SND) and ALEPH data
Apply (revisited) SU(2)-breaking corrections to data
Identify application/non-application of radiative corrections
Recompute all exclusive, inclusive and QCD contributions to dispersion integral; revisit threshold contribution and resonances
Results, comparisons, discussions... Davier-Eidelman-Höcker-ZhangEur.Phys.J. C27 (2003) 497
BES PRL 84 594 (2000); PRL
88, 101802 (2002)
The Problem
Relative difference between and e+e
– dataRelative difference between and e+e
– data
zoom
The Changes in the Input Data
• ee databugs found by CMD-2 Coll. in their analysis
• data
no change, precision improved slightly with new L3 result on B0
2.2-2.7% luminosity correction from change in Bhabha
1.2-1.4% change in
both changes affect event separation ee / /
0.6% systematic error unchanged
and contributions re-evaluated (new SND, corrected CMD-2)
The New Situation
Relative difference between and e+e
– dataRelative difference between and e+e
– data
zoom
–
0: Comparing ALEPH, CLEO, OPAL
Good agreement observed between ALEPH and CLEO
ALEPH more precise at low s
CLEO better at high s
Good agreement observed between ALEPH and CLEO
ALEPH more precise at low s
CLEO better at high s
Shape comparison only. Both norma-lized to WA bran-ching fraction (dominated by ALEPH).
Testing CVC
Infer branching fractions from e+e– data:
2
20 SU(2)-corrected
CVC 20
6 | |BR kin( ) ( )
m
ud EWV Sds s s
m
Difference: BR[ ] – BR[e+e – (CVC)]:
Mode ( – e+e –) „Sigma“
– – 0 + 0.94 ± 0.32 2.9
– – 3 0 – 0.08 ±
0.110.7
– 2 – + 0 + 0.91 ± 0.25 3.6
leaving out CMD-2 : B0 = (23.69 0.68) % (7.4 2.9) % relative discrepancy!
Results: the Data & the Theory
Better agree-ment between ex-clusive and inclu-sive (2) data than in 1997-98 analyses
Better agree-ment between ex-clusive and inclu-sive (2) data than in 1997-98 analyses
Agreement bet-ween Data (BES) and pQCD
Agreement bet-ween Data (BES) and pQCD
use QCD
use data
Results: the Compilation
Contributions to ahad from the different energy domains:
ModesEnergy range
[GeV]
ahad (10 –10)
e+e –
Low s expansion
2m – 0.5 58.0 ± 1.7 ± 1.1rad 56.0 ± 1.6 ± 0.3SU(2)
+ – 2m – 1.8 450.2 ± 4.9 ± 1.6rad 464.0 ± 3.20± 2.3SU(2)
+ – 20 2m – 1.8 16.8 ± 1.3 ± 0.2rad 21.4 ± 1.4 ± 0.6SU(2)
2 + 2 – 2m – 1.8 14.2 ± 0.9 ± 0.2rad 12.3 ± 1.0 ± 0.4SU(2)
(782) 0.3 – 0.81 38.0 ± 1.0 ± 0.3rad -
(1020) 1.0 – 1.055 35.7 ± 0.8 ± 0.2rad -
Other exclusive 2m – 2.0 32.2 ± 1.6 ± 0.3rad -
J /, (2S) 3.08 – 3.11 7.4 ± 0.4 ± 0rad -
R [data] 2.0 – 5.0 33.9 ± 1.7exp ± 0rad -
R [QCD] 5.0 – 9.9 ± 0.2theo -
Sum 2m – 696.3 ± 6.2 ± 3.6rad 711.0 ± 5.0 ± 0.8rad ± 2.8SU(2)
Discussion
The problem of the + – contribution :
Experimental situation:
corrected CMD-2 results in agreement with data up to s 0.7 GeV2
within 2 % per point: large improvement!
older e+e exp. low in this range by 4 % (OLYA), almost within systematics
CMD-2 and older e+e exp. low / in the range 0.7- 0.9 GeV2 by 9 %
ALEPH and CLEO spectral functions in good agreement within errors, OPAL deviates more (especially below 0.4 GeV2)
Concerning the remaining line shape discrepancy (0.7- 0.9 GeV2):
e+e is consistent among experiments, large radiative corrections applied, preliminary results from KLOE in agreement
is consistent among experiments in different environments
SU(2) corrections: basic contributions identified and stable since long; overall correction applied to is (– 2.2 ± 0.5) %, dominated by uncontroversial short distance piece; additional long-distance corrections found to be small
At present, we believe that it is still unappropriate to combine and e+e – :
[ – e+e ] = (–14.7 ± 6.9exp ± 2.7rad ± 2.8SU(2) ) 10–10 1.9
[DE
HZ
’03]
Final Results
(696.3 ± 7.2) 10–10
[ e+e ] = (2.1 ± 1.1)% 692.4 ± 6.28) 10–10
(11 659 180.9 ± 7.2had ± 3.5LBL ± 0.4QED+EW) 10–10
(11 659 195.6 ± 5.8had ± 3.5LBL ± 0.4QED+EW) 10–10
Hadronic contribution from higher order : ahad [(s/)3] = – (10.0 ± 0.6) 10 –10
Hadronic contribution from LBL scattering : ahad [LBL] = + ( 8.6 ± 3.5) 10 –10
[DH’98]
(exp and theo errors added in quadrature)
inclu-ding:
a [exp ] – a [SM ]
(10–10)=
22 ± 11[e+e
–]
7 ± 10 [ ]
Observed Difference with Experiment:
Conclusions/Perspectives
Hadronic vacuum polarization creates dominant systematics for SM predictions of the muon g-2
2002 analysis of leading hadronic contribution motivated by new, precise e+e
– (0.6% systematic error) and (0.5% error on normalization) data
Correction of spectral function for SU(2) breaking on better ground
Radiative (VP and FSR) corrections in e+e – : major source of systematics
All exclusive and inclusive as well as resonance contributions re-evaluated
2003 re-analysis using corrected CMD-2 results
We still conclude with two incompatible numbers from e+e – and , leading
to SM predictions that differ by 1.9 [e+e – ] and 0.7 [ ] from experiment
Hadronic vacuum polarization creates dominant systematics for SM predictions of the muon g-2
2002 analysis of leading hadronic contribution motivated by new, precise e+e
– (0.6% systematic error) and (0.5% error on normalization) data
Correction of spectral function for SU(2) breaking on better ground
Radiative (VP and FSR) corrections in e+e – : major source of systematics
All exclusive and inclusive as well as resonance contributions re-evaluated
2003 re-analysis using corrected CMD-2 results
We still conclude with two incompatible numbers from e+e – and , leading
to SM predictions that differ by 1.9 [e+e – ] and 0.7 [ ] from experiment
The key problem is the quality of the experimental data...
Future experimental input expected from:
More CMD-2 results to come, new VEPP, CLEO & BES as /charm factories
B factories: will improve the line shape from , but not the normalization
ISR production e+e– hadrons + @ KLOE, BABAR
The key problem is the quality of the experimental data...
Future experimental input expected from:
More CMD-2 results to come, new VEPP, CLEO & BES as /charm factories
B factories: will improve the line shape from , but not the normalization
ISR production e+e– hadrons + @ KLOE, BABAR
BaBar ISR : e+e-
2)(
NN sF
Ratio cancels:• luminosity• ISR and VP radiative corrections• many efficiencies (photon, tracking)
Boost:• acceptance down to threshold• easier particle ID
Small corrections:• trigger efficiency (track and EMC triggers)• FSR corrections, can be studied exp.
Major work: particle ID efficiency matrix (P,,)
BaBar ISR : e+e- 22
BaBarBaBar89.4fb89.4fb-1-1
• very clean sample (background~2% )very clean sample (background~2% )• whole mass range is coveredwhole mass range is covered• large statistics (~75k events), syst. error large statistics (~75k events), syst. error ~5%~5%
preliminary
BaBar ISR : impact on g-2
• most important channel still under study (need <1% syst)
• BaBar is the only experiment covering at the moment the energy range 1.4 - 2 GeV where previous results are not accurate
• illustrate power of BaBar data with available 4 results:
contribution to ahad (1010) from 2+ 2 (0.56 – 1.8 GeV)
from all e+ e exp. 14.21 0.87exp 0.23rad
from data 12.35 0.96exp 0.40SU(2)
from BaBar 12.95 0.64exp 0.13rad
Top Related