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A. Drutskoy, University of Cincinnati
Results and prospects of Y(5S) running at Belle.
March 14, 2008, Lausanne, Switzerland.
LPHE seminar Results and prospects of Y(5S) at Belle, March 14, 2008 , Lausanne A. Drutskoy
LPHE seminar
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Outline
Recent Belle measurements at Y(5S).
Prospects of Bs meson (and other) studies at Y(5S).
Introduction.
Conclusion.
My thoughts (speculations) about Y(5S) -> Y(6S) ->… .
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(4S)
CLEOPRL 54, 381 (1985)
(5S)
(4S)
(6S)
e+
e-
B
B_
e+ e- hadronic cross section
Resonance to continuum hadron production ratios are Y(4S)/Cont ~ 1./3.5 and Y(5S)/Cont ~ 1./10.
bb (cc,ss,uu,dd)+- - - - -
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CLEOPRL 54, 381 (1985)
(5S)
Running at Y(4S) and Y(5S)
e+ e- -> Y(5S) -> BB, B*B, B*B*, BB, BB, BsBs, Bs*Bs, Bs*Bs*
where B* -> B and Bs* -> Bs
Asymmetric energy e+e- colliders(B Factories) running at Y(4S) : Belle and BaBar
_
_ _ _ _ _ _
1985: CESR (CLEO,CUSB) ~ 0.1 pb-1 at Y(5S)
2003: CESR (CLEO III) ~ 0.42 fb-1 at Y(5S)
_ _
Bs rate is ~10-20% => high lumi e+e- collider at Y(5S) -> Bs factory.
2005: Belle, KEKB ~ 1.86 fb-1 at Y(5S)
CLEOPRL 54, 381 (1985)
(5S)
(4S)
2006, June 9-31: Belle, KEKB ~21.7 fb-1 at Y(5S)
e+ e- ->Y(4S) -> BB, where B is B+ or B0 meson
M(Y(5S)) = 10865 8 MeV/c2 (PDG) (Y(5S)) = 110 13 MeV/c2 (PDG)
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Belle
First Y(5S) runs at the KEKB e+e- collider
3.5 GeV e + 8 GeV e
-
Electron and positron beam energies were increased by 2.7% (same Lorentz boost = 0.425) to move from Y(4S) to Y(5S).
No modifications are required for Belle detector, trigger system or software to move from Y(4S) to Y(5S).
Integrated luminosity of ~1.86 fb-1 at 2005 and ~21.6 fb-1 at 2006 was taken by Belle detector at Y(5S). The same luminosity per day was taken at Y(5S) as it is at Y(4S).
Very smooth running
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Daily Luminosity
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
4/13
4/20
4/27 5/
45/
115/
185/
25 6/1
6/8
6/15
6/22
6/29
Date
Dai
ly L
umin
osity
( fb
-1)
Off-resonance run5S run
Exceeded 1.2fb-1/day forthe first time at Y(4S).
~22 fb-1
Correction factor(1.056)is necessary for 5S rundue to smaller Bhabha Cross section.
New 2006 runs at Y(5S) at Belle D
aily
lu
min
os
ity
Belle collected data at Y(5S): June 9-June 31, 2006 => 21.7 fb-1
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Belle + BaBar > 1 ab-1
Integrated luminosity
Belle (10 Mar 08)All: ~ 778 fb-1 ,Cont: ~ 68 fb-1 ,Y(5S): ~24 fb-1
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hadronic events at (5S)
u,d,s,c continuum
bb events
Bs* Bs Bs BsBs* Bs* channel
Bs events
b continuum5S) events
Hadronic event classification
CLEOPRL 54, 381 (1985)
(5S)
B0, B+ events
N(bb events) = N(hadr, 5S) - N(udsc, 5S)
fs = N(Bs(*) Bs
(*)) / N(bb)
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Number of bb events, number of Bs events
How to determine fs = N(Bs(*) Bs
(*)) / N(bb)?
Bf (Y(5S) -> Ds X) / 2 = fs Bf (Bs -> Ds X) + (1- fs) Bf (B -> Ds X)xx
2. Bf (B -> Ds X) is well measured at the Y(4S).
1. Bf (Bs -> Ds X) can be predicted theoretically, tree diagrams, large.
bb at Y(5S)
B BBs Bs
_
Ncont(5S) = Ncont(E=10.519)* L(5S) / L(cont) * (Econt/E5S)2 (5S/ cont)
Y(5S) : Lumi = 1.857 ± 0.001 (stat) fb-1
Nbb(5S) = 561,000 ± 3,000 ± 29,000 events
Cont (below 4S) : 3.670 ± 0.001 (stat) fb-1
Nbb(5S) / fb-1 = 302,000 ±15,000 CLEO: Nbb(5S)/ fb-1 = 310,000 ± 52,000
Continuum event yield (uu,dd,ss,cc) is estimated using data taken below the Y(4S):
_
=> 5% uncertainty from luminosity ratio
- - - -
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Inclusive analyses: Y(5S)->Ds X, Y(5S)->D0X
Y(5S)
Ds-> +
3775 ± 100 ev
After continuum subtraction and efficiency correction:
Bf (Y(5S) -> Ds X) 2 = (23.6 ± 1.2 ± 3.6) %
=>
points:5Shist: cont
D0 -> K- + Ds-> +
points:5Shist: cont
P/Pmax<0.5
fs = N(Bs(*) Bs
(*)) / N(bb)
Bf (Y(5S) -> D0 X) 2 = (53.8 ± 2.0 ± 3.4) %
= (18.0 ± 1.3 ± 3.2 )%
Nbb(5S) =
561,000 ± 3,000 ± 29,000 events
L = 1.86 fb-1
(Y(5S)->bb) = (0.302 ± 0.015)nb at E=10869MeV
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Signature of fully reconstructed exclusive Bs decays
BsBs , Bs*Bs , Bs*Bs*
Figures (MC simulation) are shown for the decay mode Bs -> Ds- + with Ds
- -> - .
Mbc = E*beam2 – P*B
2 ,
The signals for BsBs, Bs*Bs and Bs* Bs* can be separated well.
e+ e- -> Y(5S) -> BsBs, Bs*Bs, Bs*Bs*,where Bs* -> Bs
Mbc vs E
E = E*B – E*beam
Reconstruction: Bs energy and momentum, photon from Bs* is not reconstructed.
Two variables calculated:
MC Zoom
Mbc vs E
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Exclusive Bs -> Ds(*)+ -/- and Bs-> J// decays
Bs -> Ds+ -
Bs -> Ds*+ - Bs -> Ds(*)+ - Bs -> J/
7 evnts in Bs* Bs* 3 evnts in Bs* Bs*9 evnts in Bs* Bs* 4 evnts in Bs* Bs*
N(Bs*Bs*) / N(Bs(*)Bs
(*)) = (93± 79 ± 1)%
Potential models predict Bs* Bs* dominance over Bs*Bs and BsBs channels, but not so strong.
5.408<MBC<5.429GeV/c2
Bs* Bs*Nev=20.3 ± 4.8
Conclusions:1. Belle can take ~30 fb-1 per month.2. Number of produced Bs at Y(5S) is ~105/fb-1.
3. Bs*Bs* channel dominates over all Bs(*)Bs
(*).
4. Backgrnds in exclusive modes are not large.
Data at Y(5S), 1.86 fb-1
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Number of Bs in dataset
hadronic events at Y(5S)
bb events
Bs events
bb continuum included
N ev = 561,000 ± 3,000 ± 29,000
N ev = 101,000 ± 7,000 ± 19,000
f(Bs*Bs*) = (93 ± 79 ± 1)%
N ev = 94,000 ± 7,000 ± 20,000Bs* Bs* channel
Lumi = 1.857 fb-1
~105 Bs mesons per 1 fb-1 at Y(5S)
fs = (18.0 ± 1.3 ± 3.2 )%
Biggest uncertainty comes from fs systematics. How to improve it (3 times)?
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How to measure fs with 5% uncertainty ?
I spent a lot of time thinking about that. It could be:
2. Using same-sign lepton-lepton sample, maybe with z-distance measurement between profile-lepton vertices
3. J/ vertex xy-distance from profile.
4. Bf(B-> D+-), Bf(B-> D0-), Bf(B-> D*0-) measurements.
5. Number of slow photons from Bs* decays.
No one of these methods is perfect
1. CLEO method, from Bf(Y(5S)-> Ds X), with better statistics.
Improved measurement of fs14
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New Belle results with 23.6 fb-1
Jean Wicht
First observation of Bs-> and new upper limit for Bs-> .
Bf (Bs->)=(5.7 +1.8+1.2) 10-5-1.5-1.1
Bf (Bs->) < 8.7x10-6 (90% CL)
First measurement of Y(5S) -> Y(nS) +-decays (21.7 fb-1).
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Is the ϒ(10860) purely ϒ(5S)?
(2S)
(3S)
(2S)
(1S)
(1S)
-> look for:
+-h+h-
e+e- -> (1S) +-X
e+e- -> (2S) +-X
arXiv:0710.2577[hep-ex](accepted PRL)
Study motivated by observation ofY(4230) -> J/ +-signal (analogous?).
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4 modes seen :
Expectation: Υ(5S) width comparable to Υ(2S/3S/4S)
larger by > 102
Conclusion: not pure Υ(5S)? Energy scan: 12/07 .
Y(5S) -> (nS) h+h-
Is the ϒ(10860) purely ϒ(5S)? 17
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New Belle results with 23.6 fb-1
Jean Wicht
First observation of Bs-> and new upper limit for Bs-> .
Bf (Bs->)=(5.7 +1.8+1.2) 10-5-1.5-1.1
Bf (Bs->) < 8.7x10-6 (90% CL)
First measurement of Y(5S) -> Y(nS) +-decays (21.7 fb-1).
First measurement of Bs-> X +l - decay.
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Motivation, feasibility of Bs lifetime measurement.
Bs and Ds lifetimes can be measured using
Ds vertex, lepton track and beam profile.K+
K-
+
Ds+
+
z
This analysis requiresmuch more work … .
PDG 2007: Bf( B0->X+l-) = ( 10.33 0.28 )%
Theory predicts about 12%. It is not yet understood by theory.Some recent models predict better (dis)agreement. Calculation
problems? Exotics? Maybe semilep. Bs decays can shed some light.
Semileptonic decays have no hadronic corrections.
(B0) > (Bs) - 2.9 difference (in contrast with theory).
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Electron : Bf( Bs->X+e-) = ( 10.9 1.0 0.9 )%
Combined fit (electron+muon) :
Bf( Bs->X+l-) = ( 10.2 0.8 0.9 )%
it can be compared to PDG 2007: Bf( B0->X+l-) = ( 10.33 0.28 )%
First measurement of Bs-> X+l - decay
Electron Muon MC
from Bs
from Ds,D…
DATA DATAp
relim
inary
pre
lim
inary
23.6 fb-1 23.6 fb-1
Muon : Bf( Bs->X+-) = ( 9.2 1.0 0.8 )%
Assuming similar decay widths and (Bs)/(B0)=1.000.01 (theory; exp.diff.~2.3)
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New Belle results with 23.6 fb-1
Jean Wicht
First observation of Bs-> and new upper limit for Bs-> .
Bf (Bs->)=(5.7 +1.8+1.2) 10-5-1.5-1.1
Bf (Bs->) < 8.7x10-6 (90% CL)
First measurement of Y(5S) -> Y(nS) +-decays (21.7 fb-1).
First measurement of Bs-> X +l - decay.
Measurement of Bs-> Ds+- and Bs->Ds
+K- decays.
Bf (Bs->Ds+-)=(3.31 +0.31+0.67) 10-3
-0.30-0.64
Bf (Bs->Ds+-)=(2.2 +1.1+0.5) 10-4
-0.9-0.4 R=0.066 0.015
R. Louvot,T. Aushev, J.Wicht
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Why it is interesting?
Bf (Bs->Ds+-)=(3.31 +0.31+0.67) 10-3
-0.30-0.641.
PDG: Bf (B->D+-)=(2.68 0.13) 10-3
W-exchange diagram? Difference is not yet significant.
2. M(Bs*)=5417.4 0.4 1.0 MeV/c2
PDG: M(Bs)=5366.1 0.6 MeV/c2
(Bs0)= 51.3 1.2 MeV/c2 (B0)= 45.78 0.35 MeV/c2
Very unexpected difference
3. N(Bs*Bs*) / N(Bs(*)Bs
(*)) = (90± 3.73.9 ± 0.2)% very unexpected
4. Flat B direction angular distribution –> has to be explained.
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1. K. Sayeed, A. Schwartz: Bs-> J/ and Bs-> J/ Ks decays.
2. J.-H. Chen : Search for Bs-> K+ K- decay.
Important for future CP studies.
CP eigenstate, can be used in future for s/s measurement.
Analysis started:
1. S. Esen : Measurement Bs-> Ds+(*) Ds
-(*)
Belle results expected soon with 23.6 fb-1
Mostly CP eigenstates, important for indirect s/s measurement.
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s/s measurement from Bf (Bs -> Ds+(*) Ds
-(*))
MBs = (MH + ML)/ 2 s = (H + L)/ 2
id
d t( )Bs
Bs
= ( M – / 2 )i ( )Bs
Bs
- Schrodinger equation
Matrices M and G are t-dependent, Hermitian 2x2 matrices
Assuming CPT: M11 = M22 11 = 22
| BH,L(t) > = exp( - ( i MH,L+H,L/ 2)t ) | BH,L>
BSMs = arg (- M12/ 12) 2s = s s = 2 | 12| cos 2s
SM:s=arg(-Vts Vtb*/ Vcs/ Vcb*) =O(2) - no CP-violation in mixing
ms = MH – ML = L- H >0 in SM
“
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s = 2 | 12| cos s sSM = CP
s = 2 | 12|
To prove this formula experimentally : a) Contribution of
Bs -> Ds+(*) Ds
-(*) nis small b) Most of Bs -> Ds+ Ds
- *
and Bs -> Ds+* Ds
- * states are CP- even.
Since CPs is unaffected by NP, NP effects will decrease s.
Assuming corrections are small (~5-7%), Bf measurement will
provide information about CPs or |12|.
Bs->Ds(*) + Ds
(*) - decays have CP-even final states with largest BF’s of ~ (1-3)% each, saturating s/s .
CPs = (CP=+) – (CP= –)
s/s measurement from Bf (Bs -> Ds+(*) Ds
-(*))
CPs
s
~ ~
Bf(Bs->Ds(*) + Ds
(*) - )
1- Bf(Bs->Ds(*) + Ds
(*) - ) / 2
(first proposedby Y. Grossman)
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Ds+ -> + , K*0 K+, Ks K+
Eff(Bs->Ds+ Ds
- ) ~ 2x10-4
Eff(Bs->Ds*+ Ds- ) ~1x10-4
CPs
s~
Bf(Bs->Ds(*) + Ds
(*) - )
1- Bf(Bs->Ds(*) + Ds
(*) - ) / 2
Expected with 25 fb-1 at Y(5S):
=>Accuracy of Bf (Bs->Ds(*)+ Ds
(*)- ) has to be ~25%.
should be compared with direct s/s measurement to test SM.
<=~
Bs-> Ds+ Ds
-
Bs-> Ds*+ Ds-
Bs-> Ds*+ Ds*-
Eff(Bs->Ds*+ Ds*- ) ~5x10-5
N ~ 107 x 2x10-4 x 10-2~ 5 ev
N ~ 107 x 10-4 x 2x10-2~ 5+5 ev
N ~ 107 x 5x10-5 x 3x10-2~ 4 ev
s/s lifetime difference can be measured directly with high accuracy at Y(5S) and also at Tevatron and LHC experiments.
s/s measurement from Bf (Bs -> Ds+(*) Ds
-(*))
Y(5S), 1.86 fb-1
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1. Bs -> Ds+ - , Bs -> Ds
+ a1- ,
Bs -> Ds*+ - , Bs -> Ds*
+ - , Bs -> Ds*+ a1
- .
BF’s should be compared with B0 partners to test SU(3).
2. Bs -> J/ , J/ ’ , J/ , J/ f0(980) , … ,Bs-> J/ K+ K-.
What is fraction of ss component in different mesons?
Further physics program with 23 fb-1
Quark model : ()=(uu+dd-ss)/ 3 (’ )=(uu+dd+2ss)/ 6
B(Bs0->J/ ) = 1/3 B(Bs
0->J/ )
Mixed channels? Enhanced branching fractions?
B(Bs0->J/ ’ ) = 2/3 B(Bs
0->J/ )
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3. Bs -> DsJ+ - (4 states).
Interesting physics issues, critical test of DsJ nature.
Inclusive DsJ production study?
Further physics program with 23 fb-1
4. Bs -> D0 K0(*).
Statistically significant signals are expected with BF’s predicted at [C-K.Chua,W-S.Hou, hep-ph/0712.1882].
Color-suppressed
Bf(Bs->D0K0) ~8x10- 4 => ~20 signal
events should be seen with 23.6 fb-1
at Y(5S).
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Color-suppressed Bs-> D0 K0 decay
Bf (B0->D+-)
Bf (B0->D00) =(2.91 ± 0.28) x10- 4
(3.4 ± 0.9) x10- 3~ 0.1
Which diagram, color-suppressed or FSI, is dominant in B0->D00 decay ? Decay mode Bs->D0K(*)0 has no FSI
diagram. If the ratio Bf(Bs->D0K0)/Bf(Bs->Ds+-) ~0.1,
then color-suppressed diagram dominates. If the ratio issignificantly smaller, then FSI diagram dominates.
Color-suppressedFSI
Color-suppressed
~
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5. Bs -> Ds+ l- , Bs -> Ds*
+ l- (Bs->K+ l- ?).
7. Bs lifetime measurement.
Further physics program with 23 fb-1
Important SU(3) test. CDF obtained large DsJ semileptonic BF (?).
Good accuracy is expected (5-10%). Important measurement.
6. Bs decays with baryons (with baryons).
Largest B0 baryonic Bf’s are ~10-3. Is it similar in Bs decays?
Different samples can be used: fully reconstructed events,
CP-fixed modes, two lepton events, Ds+ lep+ events … .
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Feasibility of Bs lifetime measurement with same-sign leptons
Lifetime can be measured using two fast same sign lepton tracks and beam profile. To remove secondary D meson
semileptonic decays: P(l )>1.4 GeV.
+
z = c t
+
Y(5S)
Bs
Bs
Beam profile
Z beam ~ 3 mm;
z ~ 0.1- 0.2 mm.
Y(5S) : Bs(l +) Bs(l
+) / Bs(l +) Bs(l
-) = 100%
Y(4S) : B(l +) B(l +) / B(l +) B(l - ) ~ 10%
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Comparison with Fermilab Bs studies.
There are several topics, where Y(5) running has advantagescomparing with CDF and D0:1) Model independent branching fraction measurements.
2) Measurement of decay modes with , 0 and in final state (Ds+-).
3) No trigger problems for multiparticle final states (like Ds+ Ds
-).
4) Inclusive branching fraction measurements (semileptonic Bs).
5) Partial reconstruction ( Bf (Ds+ l- ) using “missing- mass” method).
There are also disadvantages:1) We have to choose between running at Y(4S) or Y(5S).
2) Number of Bs is smaller than in Fermilab experiments.
3) Vertex resolution is not good enough to measure Bs mixing (???).
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Future physics program at Y(5S)
Realistic value of 200 fb-1
Optimistic value of 2000 fb-1
Only big deals:
1. s/s measurement
2. Measurement of Bs-> decay
Decay modes Ds(*)Ds
(*), K+K-, , , J/()
~500 CP-fixed events with 200fb-1 => 5-10% accuracy in s.
It also requires about 1000fb-1 to measure.
3. Bs mixing measurement
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It is often postulated, that Bs mixing cannot me measuredat the Y(5S). Have anybody checked it? Is it correct or not?
Bs mixing measurement
Can we measure Bs mixing? Let’s check it.Distance between max and min of oscillation function:z= ms c = 22.5m with =0.425
Can we increase at Y(5S) runs by 50%? Probably yes.
Then we need to get single vertex resolution of ~20 m.
Is is planned resolution for fast (00 dip angle) tracks (next slide).
=> with high statistics we can select high vertex resolution events.
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Yes, we can.
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Impact Parameter resolution
r-direction z directionCalculated by TRACKERR
Occupancy effects. Degradation of intrinsic resolution is included. Efficiency loss is NOT included
Beampipe radius is importantCompetitive performance as the current SVD
LoI ‘04sBelleSVD2(now)
For
0.2GeV 0.5GeV 1.0GeV 2.0GeV
sin0 1.4
0.02
0.01
[cm]
0.03[cm]
T.Kawasaki,Atami BNM2008Jan 2008
20m
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CLEOPRL 54, 381 (1985)
(5S)
What else can be done at Super B Factory?
Rates at e+e- continuum should besimilar, baryon production is large.
M(b)x2 = (11248 ± 18) MeV/c2 => 6.3 % up from Y(4S) CME.
M(b) = (5624 ± 9) MeV/c2
Can Super B factory CM energy range be increased ?
M(Bc) = (6286 ± 5) MeV/c2
e+e- Y(6S,7S) BsBs, bb, BcBc, bb … ?
PDG (Z->bb, pp at S1/2=1.8TeV) b hadron fraction(%)
B+ , B0 39.8 ± 1.0
Bs 10.4 ± 1.4
b baryons 9.9 ± 1.7
__ _ _
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Conclusions
Bs studies at e+ e- colliders running at Y(5S) have some advantages
comparing with hadron-hadron colliders. These colliders are in somesense complementary.
Bs decays with branching fractions down to 10-6 can be measured
with statistics of ~100 fb-1 at e+e- colliders running at Y(5S).
Many important SM tests can be done with statistics of the order
of 1000 fb-1.
It is important to have more flexibility in beam energies.
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Background slides
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/ KL detector
Central drift chamberHe(50%)+C2H6(50%)
EM calorimeter (CsI(Tl))
Cherenkov detector n=1.015~1.030
Si vertex detector
TOF counter
SC solenoid 1.5T
Belle DetectorBelle Detector
8GeV e
3.5GeV e
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dz resolution
dz resolutoin
SuperBSVD3modSVD3
For 0.2GeV 0.5GeV 1.0GeV 2.0GeV
dz
T.Kawasaki,Atami BNM2008Jan 2008