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Search for (3770) non-DD-bar Decays

Dahua Zhang

(for BES Collaboration)

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

QWG’ 04October 12—15, 2004

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Outline

Introduction

Search for

Summary

Evidence of /)3770( Jψ

..)3770( * ccKKψ

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Introduction

Since its mass is above open charm-pair threshold and its width is two order of magnitude larger than that of , (3770) is thought to decay almost entirely to pure DD-bar.

(3770) resonance

Theoretical arguments

It is believed to be a mixture of and states of system

131 D 1

32 S cc

)3686(

There are some theoretical arguments about decays

Lipkin pointed out that could decay to non-DD-bar final states with a large branching fraction.

(3770)

(3770)

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DDnon

Also see (hep-ph/0105327, J.L. Rosner)

Experimental study or search for some exclusive decaymodes can be used to check the potential models of quarkonium and the hadronic transition mechanism of quarkonium states.

To understand the long standing ρ-π puzzle in charmonium decays, the measurement of the partial width of V-P channels in ψ(3770) decay is necessary and is very interesting.

Study of exclusive decays of ψ(3770)

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(1991)11 PLB267keV 160)( 13 gggD

Rosner) J.L. ,ph/0105327-(hep keV 620 )χ γΓ(ψ(3770) cJ

)155PRD41(1990 Kuang, Y.P. keV, 200) /)3770(( J

keV 980))3770(( DDnon

4.2%))3770(( DDnonBF Added all above numbers up !

Theoretical prediction

VP)ψJΓ(VP)Γ(ψ(3770)

J.L. Rosner predicts

There are some theoretical calculations about non-DD-bar decays

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(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.

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4-prong with net charge zero0.85|cos|

(K) 0.001CL (K) π

01.0)4,P( 2 K

ππππ

22 ,4)P(χ)4,P( K

selection Ksatisfy 0S

Selection criteria

..00* ccKK S

.C.L 90%at @ 3.2)( * KKeeN

Search for charmless decays of

Data taken around (3770) peak

.. ,..)3770( *00* ccK KccKK

1pb 727 .Ldt

windowmass K0S

0SK

M

8.35.12)( 00* SKKeeN

0)( * KKeeN

Neutral mode Charged mode

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observed signalt significan No 00 c.c. KK S*

observed signal No KK*

.C.L 90% @ 3.2)( * KKeeN

Data taken off-resonance (@ 3.65 GeV)

7.100*

SKKQEDN

2.4*

KK

QEDN

Normalized to the luminosity and phase space of ψ(3770) production

1pb 4.6 Ldt

.C.L 90% @ 3.9)( 00* SKKeeN

Check if there are continuum

production ?

0SK

M

KK *

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c

c

process photon one onannihilati process continuumphoton one

hadrons hadrons

e e

e e

Resonance productions and decays QED process

Observed in experiment

ga amplitude a amplitude QEDa amplitude

Charmless final states observed

2||)hadrons charmless( QEDgobserved aaaeeN

** *c

c

hadrons

e

e

*g

processon annihilatigluon three

|a|~|a| and |a||a| gQEDg around 3.77 GeV

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A detailed maximum likelihood analysis based on above observed event numbers gives

69592 .

230.246.1

00* ||86.1))3770(( gS aKKN

2490300

00 4390 |a|.)KKee(N QED..QEDS

*

16162 . χ 0 |a| set g

giving a significance of

is the phase difference between and

2.4

ga QEDao.cos 1809990

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Those yield the branching fraction and upper limit to be

pb 4.0)6.04.18()( GeV 3.773

00* KKeeobs

L. C. 90%at 102.1))3770(( 3-00* KKBF

keV 3.3)1.10( 7.120.8)3770(

00*

KK

C.L. 90% @ keV 2900*)3770(

KK

4-5.44.3

00* 101.3)3.4())3770(( KKBF

and partial width to be

(preliminary !)

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)3770(

c

c c

c

/J

/Jψ ''Evidence for

4.17.27 1pb data @ around 3.773 GeV

4 good charged tacks per event

ll are identified by combining dE/dx, TOF, BSC & Muon

20openning

/'' JSearch for in two different ways

0)P , E(Efit 4C )2

of mass recoil examine )1

cm

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Main source of background is

/)3770( J /' J andproductions generated at different actual energy after ISR

/' J

/)3770( J

dotted line solid line

Evidence for (cont’d)

/Jψ ''

/' J

e

e

*

produced

around nominal center-of-mass energy due to Breit-Wigner tail and ISR

Nominal c.m. energy

Actual c.m. energy

Nominal c.m. energy of 3.773 GeV

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Examine the recoil mass of

Projecting the events on to the vertical scale (recoil mass of

), the evidence for is observed

llECMll

EE

5 . 2| |

MeV150| | / JllMM

22 ||)(

PEEM cmREC

/'' J

'

(mainly)

/)3770( J

Due to ISR

Evidence for (cont’d)

/Jψ ''

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Evidence for (cont’d)

/Jψ ''

/ return ISR ' Jψ

/)3770( J

/' Jand

Data MC

9.55.25 /J MeV3.03103.3M1

signal events

Analysis of the recoil mass

4.23.11.11 9.55.25

/' J

out of

events in total

/' J

20 times large than the data

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Evidence for (cont’d)

/Jψ ''

analysis of the fitted dilepton masses of llOpen histogram is for e+e- channel,

histogram in yellow is for mu+mu- channelISR todue production '

mainly

The histogram is psi(3686), while error bars are the psi(3686) + psi(3770)

/Jψ ''

8.48.17

3.15.00.6

/)3686( Jψ

/)3686( Jψ

/J

8.48.11)/)3770(( JN

data MC

20 times large than the data

signal events

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Check for other background

Two photon events

Analysis of 100000 two-photon Monte Carlo events, no “ ” “signal” events are found from analyzing the Monte Carlo events

/J

events

Analysis of 50000 events, no “ ” “signal” events are found from analyzing the Monte Carlo events

ee/J

(~4 times larger than the data)

(~4 times large than the data)

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events

Analysis of the MC events of 13 times large than the data, no “ ” “signal” events are found from analyzing the Monte Carlo events

DDee where the D or D-bar auto-decay to all possible final states

Analysis of the data taken at 4.03 GeV with BES-I

Analysis of 22.3 pb-1 of data (@4.03 GeV), no significant “ ” “signal” events are found from analyzing the Monte Carlo events

/J

/J

eventshadronsee Generated with Lund generator (JETSET74)

/JAnalysis of the MC events of 1.6 times large than the data, no “ ” “signal” events are found from analyzing the Monte Carlo events

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5)3770( 10)37.085.1( prodN

Number of

002.0160.0

Efficiency

003.0193.0 (for analysis of pi+pi- recoil mass)

(for analysis of the fitted dilepton masses)

/Jψ ''Evidence for (cont’d)Signal significance

The probability that the 17.8 events observed are due to a fluctuation of the events is .

)3770(

3.15.00.6 3101.1

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/Jψ ''

Branching fraction

Partial width

)%083.0142.0342.0()/( '' JBF

)%082.0137.0338.0()/( '' JBF

Evidence for (cont’d)

(recoil mass)

(K.F.)

keV )213280()/( '' J

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BES searched for the charmless decay events of

measured the partial width of

BES observed hadronic transition of to and measured the partial width to be

(3770) /J

keV )213280()/( '' J

.

.

keV 3.3)1.10( 7.120.8)3770(

00*

KK

..,..)3770( *00* ccK KccKK

C.L. 90% @ keV 2900*)3770(

KK

and set its upper limit to be

(preliminary !)

(preliminary !)

SUMMARY

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谢 谢！

Thank You ！

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Assuming the continuum as CLEO-c observed, then

31.154.0

200* 55.0))3770(( aKKN S

giving a significance of 2.6 σ

0.500*

SKKN

4-3.12.1

00* 100.4)3.1())3770(( KKBF

Backup slides