Pr

1
R Group Working Report
Haiming Hu Representing R Group
BES Annual Shanxi, May. 23-26, 2004

• Outline
• RQCD data taking
• e e- ?proton-antiproton cross section
• e e- ???-??- form factor
• The fit of the excited ?-family resonant
  parameters
• Conclusions/Perspectives

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R and QCD

• R98 and R99 results
• Comments on the Rexp and RQCD
• ? Deviate about 1s 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 ?

3
RQCD Data Taking
Jan.3 Feb. 7 2004
Analysis by the programs of R99 measurement
Data quality check
Jin Yis report
In general, the RQCD data quality is good.
4
The cross section of e e- ???-??- ?
2
Yuan 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 e e- ???-??-
The cross section and the Form factor measured
by CDM,ND, DM2, OLYA groups between 1-2 GeV
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The cross section of e e- ???-??- ?
Back-ground analysis
Event selection
Cross section
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The cross section of e e- ???-??- ?
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 except at 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.
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The cross section of e e- ???-??- ?
BES V103 SIMBES
Cross section
BES V101 SOBER
Cross section
Can not fit the theory by V103 and SIMBES results
together with the low energy experiments, they
are not consistent with each other obviously.
Form factor
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The EM form factor of proton
Li Huihong
9
The Conserved Vector Current SU(2)
CVC I 1 V
W I 1 V,A
? I 0,1 V
??
e
?
?
hadrons
W
e
hadrons
fundamental ingredient relating long distance
(resonances) to short distance description (QCD)
Hadronic physics factorizes in Spectral Functions
Isospin symmetry (CVC) connects I1 ee cross
section to vector? spectral functions
branching Fractions mass spectrum
kinematic factor (PS)
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The fit of the excited ?-family resonant
parameters ?
Hu Haiming Huang Guangshun
The 4 excited ?-family resonant Structure was
scanned in 1999.
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The fit of the excited ?-family resonant
parameters ?
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
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The fit of the excited ?-family resonant
parameters ?
Fit R values iteratively, the polynomial and QCD
BG forms were used
Fit the observed cross section, the DASP type BG
form was used
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The fit of the excited ?-family resonant
parameters ?
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
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The fit of the excited ?-family resonant
parameters ?
Some attempts to meet referees 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
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The fit of the excited ?-family resonant
parameters ?
Some attempts to meet referees requests
Energy-dependent hadronic width
The effective interaction theory was
used
Interaction matrix element
The decay types concerned
The interactive Hamiton
Hadronic decay width
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The fit of the excited ?-family resonant
parameters ?
Some attempts to meet referees requests
The running
mass parameter
means the principal value of integral
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The fit of the excited ?-family resonant
parameters ?
Some attempts to meet referees requests
The comparison between experiment
and theory/model The
parameters were putted by hand, i.e. not fit yet
R value by experiment
R value by theory model
Total continuum GB
Continuum QCD BG with u,d,s qurks RQCD(u,d,s)
Continuum two-body BG from ee-?DD
Continuum three-body BG from ee-?DMD
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ee Radiative Corrections
Multiple radiative corrections are applied on
measured ee 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.)

• Initial state radiation (ISR)
• corrected by experiments

• Final state radiation (FSR) we need ee ?
  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

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2002 Analysis of a?had

• Motivation for new work
• New high precision ee 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

CMD-2 PL B527, 161 (2002)
ALEPH CONF 2002-19
BES PRL 84 594 (2000) PRL 88, 101802 (2002)
Cirigliano-Ecker-Neufeld JHEP 0208 (2002) 002

• 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-Zhang Eur.Phys.J. C27
(2003) 497
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The Problem
Relative difference between ? and ee data
zoom
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The Changes in the Input Data

• e?e? data

bugs found by CMD-2 Coll. in their analysis

• 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)

• ? data

no change, precision improved slightly with new
L3 result on B??0
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The New Situation
Relative difference between ? and ee data
zoom
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? ? ? ? 0?? Comparing ALEPH, CLEO, OPAL
Shape comparison only. Both norma-lized to WA
bran-ching fraction (dominated by ALEPH).

• Good agreement observed between ALEPH and CLEO
• ALEPH more precise at low s
• CLEO better at high s

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Testing CVC
Infer? branching fractions from ee data
Difference BR? BRee (CVC)
leaving out CMD-2 B??0 (23.69 ? 0.68)
? (7.4 ? 2.9) relative discrepancy!
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Results the Data the Theory
use data

• Agreement bet-ween Data (BES) and pQCD

• Better agree-ment between ex-clusive and
  inclu-sive (??2) data than in 1997-98 analyses

use QCD
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Results the Compilation
Contributions to a?had from the different energy
domains
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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 ee? exp. low in this range by ? 4
  (OLYA), almost within systematics
• CMD-2 and older ee? 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)
• ee? 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 ee
?? ee? (14.7 6.9exp 2.7rad
2.8SU(2) ) 1010 1.9 ?
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Final Results
(exp and theo errors added in quadrature)
DH98
DEHZ03
Hadronic contribution from higher order a?had
(?s/?)3 (10.0 0.6) 10 10 Hadronic
contribution from LBL scattering a?had LBL
( 8.6 3.5) 10 10
inclu-ding
Observed Difference with Experiment
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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 ee (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 ee
  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 ee and ? , leading to SM predictions
  that differ by 1.9 ? ee 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 ee ? hadrons ? _at_ KLOE, BABAR

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BaBar ISR ee- ? ? ?????

• Boost
• acceptance down to threshold
• easier particle ID

• Ratio cancels
• luminosity
• ISR and VP radiative corrections
• many efficiencies (photon, tracking)

• Small corrections
• trigger efficiency (track and EMC triggers)
• FSR corrections, can be studied exp.

Major work particle ID efficiency matrix (P,?,?)
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BaBar ISR ee- ? ? 2???2??
BaBar 89.4fb-1
preliminary

• very clean sample (background2 )
• whole mass range is covered
• large statistics (75k events), syst. error 5

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BaBar ISR impact on g-2

• most important ?? channel still under study
  (need lt1 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 a?had (?10?10) 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