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