1
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
2
Outline
Introduction
Search for
Summary
Evidence of /)3770( Jψ
..)3770( * ccKKψ
3
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)
4
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)
5
(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
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