New Results from BES

1
New Results on ?(3770) and D Mesons Production
and Decays From BES
Gang RONG (for BES Collaboration) Presented by
Yi-Fang Wang
Charm07 Cornell University, August 4-8 2007
2
Outline
Introduction

Inclusive decays of D Mesons

Measurements of R

Parameters of ?(3770)

B?(3770)?non-DD and Search for Charmless decays
of ?(3770)

Summary

3
Introduction
BESII ?(3770) data sample of about 33 pb-1
Data Samples

• about 17.3 pb-1 data taken at 3.773 GeV

• about 7 pb-1 data taken from 3.768 GeV to 3.778
  GeV

• about 8 pb-1 data taken from 3.665 to 3.878 GeV

• about 6.5 pb-1 data taken at 3.650 GeV

• about 1 pb-1 data taken at 3.665 GeV

pb-1
World ?(3770) Samples (pb-1)
(by summer,2005)
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D- and D0 tags
Double tag analysis
Absolute measurements
5
D??X
With the singly tagged D sample, we can do some
absolute measurements of D decays on the side
recoiling against the tags .
K
Singly tagged D sample
D
p
tag
p
PT
D-
e
e-
0.52-0.62 GeV
D
D
P
0.62-0.72 GeV
Xany particles
0.72-0.82 GeV
0.82-0.92 GeV
P is any charged particle (?, e, p and K)
0.92-1.02 GeV
mKnp(Dtag)
Nµobs
6
D??X
µtrue
etrue
Ktrue
ptrue
eim ratio of a particle i to be identified as
m
Nobsi observed particle I Ntruei true
particle i

ARGUS 6.00.71.2 -
CHORUS 6.51.20.3 -
BES-II 6.81.50.6 17.60.71.3
PDG 6.50.7 16.10.4
First measurements
PDG
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D?eX and D?KX
B(D?eX) and B(D?KX)

CLEO-c 6.460.170.13 16.130.200.33
MarkIII 7.51.10.4 17.01.90.7
BES-II 6.30.70.4 15.21.00.7
PDG2007 6.550.17 16.10.4
Preliminary
Comparison of Results

BES-II 24.71.31.2 15.21.00.7 57.81.63.4 3.50.70.3
PDG2007 27.52.4 5.51.6 534 3.40.6-0.4
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The quantity R

• Why are we interested in R(s) ?

• Vacuum polarization correction needs the R(s)
  values, which plays an important role in the
  precision test of the Standard Model.

• For evaluation of the electromagnetic coupling at
  the Z mass scale,

• For determination of of
  the muon.

• Evaluate

• Non-DD decays of ?(3770)

• important in open charm region for the
  understanding of 1-- resonance production, for
  searching for new states, and for studying
  dynamics

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The quantity R

• ?(3770) production decays

It is believed to be a mixture of and
states of system. It is thought to
decay almost entirely to pure DD-bar.

Before BES-II CLEO-c, previously published data
indicate that more than about 35 of ?(3770) does
not decay to DD-bar ? This conflicts with
theoretical prediction.
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The quantity R

• New Measurements

Recently BES and CLEO-c measured the DD and
?(3770) production at 3.773 GeV based on the data
taken below DD threshold and at 3.773 GeV.
To uncover the puzzle, a better way is to make
cross section scan
A better way to measure the cross sections, the
widths of the resonance and the DD branching
fractions of ?(3770) is to analyze the
line-shapes of ?(3770), ?(3686) and DD production
simultaneously.
BES made several fine cross section scans
covering both the ?(3686) and ?(3770) to measure
the resonance parameters, branching fractions
and search for non-DD decays
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The quantity R
The Previously Measured quantity R
Precision measurement of the cross sections in
this region
Including all hadrons
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The quantity R
Definition of different R
above cc-bar threshold
below cc-bar threshold
hadrons
where q is the light (u,d,s) quarks
Ruds
Evaluate
Rhad(s)Ruds(c)(s)SRres,i(s),
Rres,i(s) is R values due to all 1-- resonances
decay to hadrons except ?(3770).
hadrons
calculate
Rhad
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The quantity R
ISR corrections
Effective c.m. energy
Moninal c.m. energy
Kuraev Fadin
the electron equivalent radiator thickness
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The quantity R
Vacuum polarization correction
Vacuum polarization change the photon propagator
results in
Radiative correction factor
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The quantity R
Results
PRL 97, 262001 (2006)
above cc-bar threshold
below cc-bar threshold
Below DD-bar threshold
Sources ?SYS ()
Luminosity 1.8
Hadron selection 2.5
M.C. modeling 2.0
ISR 1.5
?(3770) resonance parameters 2.7
Total (off ?(3770) region) 3.9
Total (within ?(3770) region) 4.9
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The quantity R
Comparison of R measurements from different
experiments
PLB 641 (2006) 145
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Resonance Parameters of ?(3770)
New measurements
68 energy points
Dec. 2003 data
The paper is being in press (PLB)
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Resonance Parameters of ?(3770)
New measurements
Comparison with those measured by other
experiments
Experiment ?prdee-??(3770)nb ?obsee-??(3770)nb
This work Dec. 2003 data 10.0?0.3?0.5 7.2?0.2?0.4
BES PRL 97(2006)121801 9.6?0.7?0.4 6.9?0.5?0.3
MARKII 9.3?1.4
M?(3770)(MeV) ?tot?(3770)(MeV) ?ee?(3770)(eV) Note
3772.4?0.4?0.3 28.5?1.2?0.2 277?11?13 PLB in press
3772.2?0.7?0.3 26.9?2.4?0.3 251?26?11 PRL 97(2006)121801
Dec. 2003 data
Experiment PLB in press PRL 97(2006)121801 PDG
B?(3770)?ee-?10-5 0.97?0.03?0.05 0.93?0.06?0.03 1.05?0.14
Dec. 2003 data
Ruds2.121 ?0.023 ?0.084
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Resonance Parameters of ?(3770)
What about World Average
Comparison of measurements of the cross section
for ?(3770) production
Leptonic branching fraction
PRL 97 (2006) 121801
Preliminary !
PRL 97 (2006) 121801
PDG04
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B?(3770)?non-DD
PLB641 (2006) 145
Determined from analysis of R values and DD-bar
cross sections
PRL 97 (2006) 121801
Obtained by fitting to the inclusive hadron and
the DD-bar production cross sections
simultaneously.
PDG07
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Search for Charmless Decays of ?(3770)
Search for Charmless decays of ?(3770)
Mode ?3.773pb ?3.650pb Bup?10-3
??0 lt3.5 lt8.9 lt0.5
?? lt12.6 lt18.0 1.9
2(??-) 173.7?8.4?18.4 177.7?13.3?18.8 4.8
KK-??- 131.7?10.1?14.1 161.7?17.9?17.1 4.8
???- lt11.1 lt22.9 1.6
2(KK) 19.9?3.6?2.1 24.1?6.5?2.6 1.7
?KK 15.8?5.1?1.8 17.4?9.2?2.0 2.4
ppbar??- 33.2?3.4?3.8 42.1?6.1?4.8 1.6
ppbarKK 7.1?2.0?0.8 6.1?3.1?0.7 1.1
?ppbar lt5.8 lt9.1 0.9
3(??-) 236.7?14.7?33.4 234.9?23.8?33.1 9.1
2(??-)? 153.7?40.1?18.4 86.6?40.3?10.4 24.3
2(??-)?0 80.9?13.9?10.0 124.3?21.7?14.9 6.2
KK-??-?0 171.6?26.0?20.9 222.8?37.7?27.2 11.1
2(KK)?0 18.1?7.7?2.1 lt23.0 4.6
ppbar?0 10.1?2.2?1.0 9.2?3.4?1.0 1.2
ppbar??-?0 53.1?9.2?6.8 29.0?11.1?3.7 7.3
3(??-)?0 105.8?34.4?16.9 126.6?47.1?19.2 13.7
We have searched for more than 40 modes for the
light hadron decays.
PLB650(2007)111
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Search for Charmless Decays of ?(3770)
Preliminary Results
Mode ?3.773pb ?3.650pb Bup?10-3
KK-2(??-) 168.0?18.2?23.7 164.9?30.3?23.2 lt10.3
2(KK-)??- 11.9?5.8?1.7 lt49.1 lt3.2
ppbar2(??-) 23.5?5.0?3.5 22.8?8.4?3.4 lt2.6
4(??-) 131.8?19.5?23.6 76.2?24.4?13.9 lt16.7
KK-2(??-)?0 231.5?63.6?37.5 lt375.2 lt52.0
4(??-)?0 lt206.9 lt119.4 lt30.6
?0??- 111.9?13.1?13.1 113.6?21.3?13.1 lt6.9
?0KK- 34.2?11.5?4.4 57.6?17.9?6.3 lt5.0
?0ppbar 13.1?3.2?1.8 17.7?6.2?2.8 lt1.7
K0K-? 94.7?15.5?10.4 85.5?26.3?14.4 lt9.7
??bar lt2.5 lt6.1 lt0.4
??bar??- lt26.7 lt42.9 lt4.4
Search for light-hadron decays of ?(3770)
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Search for Charmless Decays of ?(3770)
Search for light-hadron decays of ?(3770)
Mode ?3.773pb ?3.650pb Bup?10-3
???- lt37.1 lt50.8 5.5
?KK- lt44.4 lt53.2 6.6
?ppbar lt20.3 lt30.9 3.0
???-?0 lt25.5 lt66.7 3.8
K0K-??0 116.3?32.7?20.0 128.1?59.5?17.9 16.3
KK-??- 173.9?73.3?26.1 189.0?116.3?28.2 32.4
KK-?0?0 lt5.6 47.6?33.4?10.7 0.8
KK-??- 94.2?31.6?11.7 141.9?53.3?19.7 14.6
??bar?0 lt7.9 lt21.4 1.2
Upper limits are set at 90 CL
Preliminary Results
We searched for ?(3770)?light hadrons over 40
channels, but no significant signals were found.
This does not mean that ?(3770) does not decay
into light hadrons. To extract the branching
fractions for ?(3770)?light hadrons from the
observed cross sections, one need to make finer
cross section scan covering both ?(3686) and
?(3770) with larger data samples (BES-III can do
this well).
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SUMMARY

• Inclusive decays of D mesons

Measured BF(D ?mu X)(17.6-2.7-1.3) for the
first time
Measured BF(D ?K- X)(24.7-1.3-1.2)
Improved measurements
Measured BF(D ?K X)(6.1-0.9-0.4)
Measured BF(D0 ?K- X)(57.8-1.6-3.4)

• R value

Improved measurements of R in the range from 3.65
to 3.88 GeV
Measured Ruds 2.121-0.023-0.085
Measured Ruds(c)?(3770) for the first time

• ?(3770) parameters

Precisely measured M?(3770) 3772.3-0.5 MeV
Gtot28.5-1.2 MeV Gee277-16 eV
Precisely measured BF(??ee-)(0.97-0.08-0.05)x1
0-5
sobs?(3770) 7.15-0.25-0.25 nb combined two
measurements
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SUMMARY
Combined 49 energy point cross section scan
results and 3 energy point cross section results
(inclusive hadron and DD-bar cross sections)

• BF?(3770)?non-DDbar

Measured BF?(3770)?non-DDbar (15-5)
Measured BF?(3770)?DDbar (85-5) PDG07
BES

• Light hadron decays of ?(3770)

No significant signals for ?(3770)?light hadron
were found in about 40 channels.

• How to solve this problem ?

Finer cross section scan over ?(3686) and ?(3770)
to measure the cross sections for exclusive modes
and fitting the cross sections to extract out the
branching fractions (My comment only !)
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Thank You!
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Backup slides
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Comparison with those measured by CLEO-c
BES-II
CLEO-c
(hep-ex/0512038) PRL 96 (2006) 092002
Based on analysis of inclusive hadron and DD-bar
cross section scan data.
PLB 141 (2006) 145
Actually, considering the errors, the two
results are not in contradiction.
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Comparison with those measured by CLEO-c
BES-II
CLEO-c
Assuming that there are interference between the
two amplitudes of continuum and resonance
Based on measured R values.
Method
Method
BES measured near DD-bar threshold and R
at 3.773 GeV with traditional method, then
calculate the Born order cross section for
?(3770) production. By comparing the cross
sections for DD-bar and ?(3770) production, BES
obtained the branching fraction. BES used an ISR
generator to simulate the decay ee-? hadrons and
obtain the efficiency for ee- ? hadrons.
CLEO-c directly count the number of hadronic
events observed at 3.773 GeV, and subtract the
backgrounds from J/?, ?(2S) radiative tails and
continuum QED background. CLEO-c used the
efficiency for the decay ?(3770)? J/? p p- to
estimate the efficiency for ee- ? hadrons.
Use parameter
Use parameter
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Comparison with those measured by CLEO-c
BES-II
CLEO-c
Discussion
Method
Method
CLEO-c did not consider the difference of ISR
vacuum polarization corrections for continuum
hadron production at the two energy points (3.671
GeV and 3.773 GeV) when subtracting
background at 3.773 GeV.
if we use to
calculate the ISR vacuum polarization
correction factor, and assuming that there are
interference between the two amplitudes of the
continuum and the resonance, we would obtain
PRL 97 (2006) 121801