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First steps to radiative return studies at Belle
B.A.Shwartz
BINP, Novosibirsk
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Plan1. Basic things
2. A sample for first study
3. What’s seen for: , , KK and
This is our first steps to see what can be done at Belle for radiative return physics.
The events with 2 charged particles were studied
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)1(ln)(
)(3
422
422
3
22
em
s
mss
msmR
sdm
dσm
)1(ln)(
)(
][
][4035.022
422
2
2
em
s
mss
ms
m
mR
GeVs
GeVnb
dm
dσ
1
0
30
e+e
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)1(ln)(πs
222
4
em
s
mss
msαm
Ldm
dl
KEKB VEPP-2000
Luminosity,
см-2 s-1
1034 1032
Integrated lum. (per 107 s)
100 fb-1 1 fb-1
Integrated in the range [1-2] GeV
0.1 fb-1 1 fb-1
Comparison to VEPP-2000project, ee up to 2 GeV
(under construction at BINP)
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A sample to study
The Tau-pair sample (skim) is used ( 2<Ntrk<8, Pch<9GeV, Eecl<9GeV)
Then the following cuts were applied:
1. Ntrk=2
2. 10<Erec<11 GeV
3. Ptot <0.5 GeV
4. N>0
5. Emax>3 GeV
6. 0.7<<2.6
7. Pmin >0.7 GeV (charged)
25.9 fb-1 is used study
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Erec
Ptot
Minv
P
)( 2)(2
1beam
invbeam E
ME
PR
E2<0.2 (for 2 particles modes)
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Minv(2tr), GeV
All events , (p1/, p2/ >0.5)
Two particle events
Minv(2tr), GeV
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background
calculation
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N/N ratio
By a simple separation procedure the number of and events are obtained and ratio is calculated
(just demonstration, not for usage!)
The difference 5% can be caused by the different trigger efficiency for pion and muon events. This is a measure of systematics.
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How to compare with BaBar?
N=183093
M =31061 MeV
=16.30.9 MeV
71 J/ per 1 fb-1
From BaBar J/ paper – 7800 J/ event at 88.4 fb-1 88.2 J/ per 1 fb-1
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KK 0
ECM – ( | pmax | + | p+ | +p | )>1
GeV
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Conclusion
1. Events with radiative return can be seen at Belle with reasonable efficiency.
2. New Bhabha trigger implementation should improve the trigger efficiency at low invariant mass area
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