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New Measurements of ψ(3770) Resonance Parameters & DD-bar Cross Section at

BES-II & CLEO-c

Gang RONG

Institute of High Energy Physics, Beijing 100039, P.R. China

3rd Workshop on QuarkoniumIHEP Beijing, China October 12—15, 2004

The review talk is based on the talks given at ICHEP’04 by Anders Ryd, Ian Shipsey, Gang Rong

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OutlineIntroduction

ψ(3770) resonance parameters

production at 3.773 GeVDDResult from BES-IIResult from CLEO-c

What indicate the new measurements ?

Summary

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Introduction Puzzle of ψ(3770)production and decays

Puzzle of ψ(3770) decay

It has long been a puzzle that the measured DD-bar cross section fail to fit the measured cross section for ψ(3770) production at 3.770 GeV in e+e- experiments.

nb 8.16.11))3770((122

)3770()3770( ±=→×= −+eeBF

Mprd ψπσ

ψψ

MeV 5.29.3769)3770( ±=ψM 51012.1))3770(( −−+ ×=→ eeBF ψMass and branching fraction (PDG02):

ψ(3770) production cross section at peak

For example:

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DD-bar cross sectionMARK-III measured the observed DD-bar cross section (at Ecm = 3.768 GeV)

nb 0.50.5)( ±=→−+ DDeeobsσproduction cross section

(Added all errors in quadrature)

70.0=ISRf

nb 7.01.7)( ±=→−+ DDeeprdσ

Potentail Models predict that ψ(3770) decay into DD-bar with branching fraction of ￣100%.

Non-saturate decay ?

About 39% of ψ(3770) does not decay to DD-bar ?

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Are there non-DD-bar decay ?Theoretical prediction

There are theoretical arguments about ψ(3770) decays

Lipkin pointed out that ψ(3770) could decay to non-DD-bar final states with large branching fraction

)155PRD41(1990 Kuang, Y.P. keV, 200) /)3770(( <→Γ ππψψ J

Rosner) L. J. ,ph/0405196-(hep keV 620 ) )3770(( ≤→Γ cJχγψ

keV, 170) /)3770((37 <→Γ< ππψψ J (Y.P. Kuang, PRD65, (2002) 094024)

(1991)11 PLB267keV 160)( 13 =→Γ gggD

keV 950))3770(( ≤−→Γ DDnonψ

4.0%))3770(( ≤−→ DDnonBF ψ Added all above numbers up !

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Are there non-DD-bar decay ?About 35% of ψ(3770) missing ?

If all measurements are all right, these mean that 35%of ψ(3770) is missing

Lipkin proposed a rescattering model many years agoPL B179,278(1986)

Very recently Jonathan L. Rosner proposed a new model ---re-annihilation model to deal with that decays to charmless final states

ψ(3770)

arXiv:hep-ph/0405196 v2

To clarify this situation, it is important to more precisely measure both DD-bar cross section and ψ(3770) resonance parameters at same experiment simultaneously !

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The Beijing Electron Positron Collider(BEPC)

L ~ 1 ×1031 /cm2⋅s at ψ(3770) peak Ecm~2-5 GeV

One of the two e+e- machines in the world in the τ-charm energy region

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BESII Detector

VC: σxy = 100 µm TOF: σT = 180 ps µ counter: σrφ= 3 cm MDC: σxy = 220 µm BSC: ∆E/√E= 22 % σz = 5.5 cm

σdE/dx= 8.5 % σφ = 7.9 mr B field: 0.4 T∆p/p=1.7%√(1+p2) σz = 3.1 cm

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Muon identification can be done for the charged track with momentum of great than 0.52 GeV/c

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11

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BES-II ψ(3770) data sample

~18 pb-1 of data taken at 3.773 GeV~7 pb-1 of data taken at the region from 3.768 GeV to 3.778 GeV

~8 pb-1 of data taken in the energy region from 3.665 to 3.878 GeV

about 33 pb-1 of data collected around 3.773 GeV in total.

CLEO-c ψ(3770) data sample

about 57 pb-1 of data taken at (around) 3.773 GeV

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World ψ(3770) Samples (pb-1)

Largest sample from CLEO-c by Spring, 2004

0

10

20

30

40

50

60

MARK-I DELCO MARK-II MARK-III BES-II CLEO-c

ψ(3770)

Energy [GeV] Lum [pb^-1] Exp. Note

3.60 –3.89 ~2 MARK-I parameters3.60 –3.89 ~2 DELCO parameters3.60 –3.89 ~2 MARK-IIparameters

3.768 9.6 MARK-III D decays

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ψ(3770) Resonance ParametersCross section scan experiment

The data were collected at 49 energy points from 3.66 to 3.89 GeV, which begin from off-resonance, cover ψ(2S), ψ(3770) and stop at DD* threshold .

Separated beam collision data at 3 energy points were collected to study beam associated background.

Some J/ψ, ψ(2S) data were also taken to calibrate BEPC energy and determine εtrg

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Integrated luminosities

Luminosities were measured by using large angleBhabha scattering

About 5.4 pb-1 of data were collected for the experiment

Monte Carlo

Developed a inclusive hadronic event generator with high order ISR corrections to simulate thehadronic event productions (including Lorentzboost due to initial state photon emission) in the full energy region

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ρ ωϕ

ψ/J'ψ

)3770(ψ

GeV 78.3energy c.m. Nominal =s

Monte Carlo productionhadronsee →−+

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Events Recorded by BESII

Primarycosmic rayNπ0

e+e-e+e-

µ+

νµ

π+µ-

e+

e-e-τ-

e+ µ+ τ+

e- e-

e+ e+

e+

e- γ

γ

Nhad

e- e-

e+ e+

l+l-

qq

Primarycosmic rayNπ0

e+e-e+e-

µ+

νµ

π+

-e

e+

q-

q

Cosmic-ray and beam associated background

physics background could be estimated based on cross sections, luminosities and acceptances

bN

bN

bNhadn +)1( δ+= hadNhadn

Distributions of the vertex of events

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Hadron efficiency vs C.M. energy

[GeV] cmE

trgcmhadcm

hadcm

obshad EEL

nEεε

σ )( )(

)( =

∫ −=1

0

exp ))1(( ),( )( xssxfdxs Becthad σσ

)()()(12

)( 2222 sMMss

stot

feeB

Γ+−

ΓΓ=

πσ

(Kuraev and Fadin)

functionsampling issxf ),(

hadεObserved cross section

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'ψ

ψ/J

ψ(3770) productionTo get right resonance parameters, the two resonance productions and decays should be considered simultaneously. In this way the “correct” QED background ( )can be determined correctly !

udsR

quarks) s and du, (from QED

'ψ

)3770(ψ

)3770(ψ

BES-II Preliminary ![GeV] cmE [GeV] cmE

obshadσ obs

hadσ

0.142.24 ±=udsR

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Comparison of ψ(3770) Resonance Parameters

(preliminary !)BES-II

PDG02

MARK-II

DELCO

MARK-I

Experiment (MeV) Γ tot (eV) Γee

63772 ±

63770 ±

2.53769.9 ±

1.33772.8±

528±

524±

90370±

60180±

50276±

40260±

36225 ±

388±

286±

280±

(MeV) M∆

2.483.9 ±

524±

2.723.6±

53764 ±

4.025.5± 1.386.8±

(MeV) )3770(ψM

nb 99.011.9| MeV 8.3772)3770( ±==s

prdψσ

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Comparison of ψ(2s) Resonance Parameters

PDG2002

BES-II published(PLB550(2002)24)

This measurement(preliminary !)

experiment (keV) 'tot

ψΓ (keV) '

eeψ

Γ(MeV) M 'ψ

2860275 ±±

27264±

25300±

02.012.025.2 ±±3.01.07.3685 ±±

..AN 21.044.2 ±

09.096.3685 ± 15.019.2 ±

Using a constant for vacuum polarization correction

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DD-bar Cross Section at 3.773 GeV1pb 3.17 −=LBES-II: of data

@ 3.773 GeV

Using Kinematical fit method to improve momentum resolution and select the singly tagged D meson

D+

K-π+π+

Dtag

Single tag analysis e+ e-

D D-

−Xεσ

2 BrLN

tagDobsDD = From Monte

Carlo Xfit M=MRequiring

PDG02 Br

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+−→ πKD 0

−++−→ πππKD0

++−+ → ππKD

Observed cross sections for DD-bar production at 3.773 GeV

nb 0.310.093.58 00 ±±=obsDD

σ

nb 0.260.082.56 ±±=−+obs

DDσ

nb 0.500.126.14 ±±=obsDDσ

Preliminary !

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Radiative correctionAssuming that decay exclusively intoψ(3770) DD

2/41

0|))1((1|))1(( ),( )(

2−−

−Π−−= ∫ xsxssxfdxssM Bobs

DD

D σσ

024.0047.1)1(|))1((1| 2 ±=+=−Π− −vpxs δ PR D62

(2000)012002-1

)()()(12

)( 2222 sMMss

stot

feeB

Γ+−

ΓΓ=

πσ

B

obs

gσσ

=Initial State Radiation correction factor

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GeV 773.3At =s

MeV2.53769.9M ±=

MeV2.723.6" ±=Γtotψ

eV 40260" ±=Γeeψ

036.0779.0 ±== Tree

obs

gσσ

Obtained based on PDG02 ψ(3770) resonance parameters:

Radiative correction factor

Due to the uncertainties in resonance parameters and vaccum polarization )1( vpδ+

nb 0.370.103.29 ±±=−+tree

DDσ

nb 0.740.157.88 ±±=treeDDσ

nb 0.450.124.60 00 ±±=treeDD

σ

GeV 773.3@ =s

preliminary

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and

12.002.029.1 ±±==−+−+ → µµ

σσ

ee

treeDD

DDR

R

The contribution to R in the charm threshold region from the light quarks is estimated to be , which is obtained by fitting to the R values from 2.0 to 3.0 GeV measured by BES-II. The theoretical expectation is that is approximately independent of center of mass energy in this region.

14.026.2 ±=udsR

udsR

18.002.055.3 ±±=R

R DDR

The open square is charm counting method of R measurementAssuming that decays

exclusively into DD-bar

GeV) 3.773(at nb 709.6(GeV)

nb 8.8622 ==−+−+ →

cmee Eµµ

σ

Squares are the BES-II direct R measurements by counting inclusive hadronic events

(preliminary !)

ψ(3770)

0.142.24 ±=udsR which is obtained in measurement of ψ(3770) resonance parameters

udsDD RRR += udsDD RRR +=or

DDR

yielding

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1pb 2.57 −=L

DD-bar Cross Section at 3.773 GeVCLEO-c: of data @ 3.773 GeVUsing ‘double tag’ method, pioneered by MARK-III

Near DD-bar production threshold region

DK-π+tag

D+

π+

D D-

−X Doubly tagged D

e+ e- e-

DK-

tag

D0

π+

Singly tagged D sample

D D0

0X

e+

28

44780)(

00 =DD

N

17360)(

=−+ DDN

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DDiii NBN ε2=2

2

4 i

ii

ii

iDD N

NNεε

=DDiiiii NBN 2ε=

510)03.004.098.1(00 ×±±=DD

N510)04.006.048.1( ×±±=−+DD

N

nb )150070473(00 ...obsDD

±±=σ

nb )110110592( ...obsDD

±±=−+σ

nb )22013006.6( ..obsDD ±±=σ

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What indicate the new measurements ?What information can we obtain from the new measurements at BES-II and CLEO-c ?

Based on the measured DD-bar cross sections from BES-II & CLEO-c, we obtain the averaged DD-bar cross section

nb )150493(00 ..obs

DD±=σ

nb )140582( ..obsDD

±=−+σnb )23008.6( .obs

DD ±=σ

averaged cross sections

Using the new ψ(3770) resonance parameters measured by BES-II, we obtain the ISR correction factor at 3.773 GeV

76.0=g

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Tree level cross sections

nb )200594(00 ..tree

DD±=σ

nb )180393( ..treeDD

±=−+σnb )30099.7( .tree

DD ±=σ

averaged cross sections from BES-IIand CLEO-c

From BES-II preliminary result of

nb 99.011.9| MeV 8.3772)3770( ±==s

prdψσ

We can obtain the tree level cross section for ψ(3770)production to be

nb )95.070.8()37770(

±=treeψσσ

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ψ(3770)Branching fractions of decays

Using the BES-II & CLEO-c preliminary results on and presented at ICHEP’04, we can obtain

DDσ)3770(ψ

σ

Branching fraction [%]

00(3770) DD→ψ 6.252.8 ±

−+→ DD(3770)ψ 4.739.0 ±

10.691.8 ±DD→(3770)ψ

10.68.2 ±DDnon −→(3770)ψ

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SUMMARYBES measured ψ(3770) resonance parameters .

PDG02

BES-II

Experiment (MeV) M )3770(ψ (MeV) Γ tot (eV) Γee

2.53769.9 ±

1.33772.8±

40260±

36225 ±

(MeV) M∆

2.723.6±

4.025.5± 1.386.9±(preliminary !)

2.483.9 ±

nb 0.999.11 )3770( ±=prdψσ (BES-II preliminary !)

0.142.24±=udsR From 3.66 to 3.87 GeV

BES measured the DD-bar Cross Section at 3.773 GeVto be.

( ISR based on PDG02 )nb 0.740.157.88 ±±=treeDDσ (BES-II preliminary !)

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SUMMARYMeasured the Observed cross section at 3.773 GeV .

CLEO-cBES-IIobs

DD00σ

obsDD −+σ

nb )31.009.058.3( ±±

nb )26.008.056.2( ±±

nb )50.012.014.6( ±±

nb )150070473( ... ±±

nb )110110592( ... ±±

nb )22013006.6( .. ±±

(preliminary !) (preliminary !)

Both the BES-II and the CLEO-c results were reported at ICHEP’04 as well

obsDDσ

.What is the non-DD-bar branching fraction of ψ(3770)

It is reduced to about from using the new measurements at BES-II and CLEO-c

)%118( ± %39

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谢 谢！

Thank You！