A. Drutskoy, University of Cincinnati

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

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) ->… .

2

(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)+- - - - -

3

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)

4

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

5

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

6

Belle + BaBar > 1 ab-1

Integrated luminosity

Belle (10 Mar 08)All: ~ 778 fb-1 ,Cont: ~ 68 fb-1 ,Y(5S): ~24 fb-1

7

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)

8

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

- - - -

9

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

10

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

11

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

12

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)?

13

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

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).

15

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?).

16

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


Jean Wicht


Bf (Bs->)=(5.7 +1.8+1.2) 10-5-1.5-1.1

Bf (Bs->) < 8.7x10-6 (90% CL)


First measurement of Bs-> X +l - decay.

18

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).

19

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)

20


Jean Wicht


Bf (Bs->)=(5.7 +1.8+1.2) 10-5-1.5-1.1

Bf (Bs->) < 8.7x10-6 (90% CL)


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

21

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.

22

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.

23

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

“

24

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= –)


-(*))

CPs

s

~ ~

Bf(Bs->Ds(*) + Ds

(*) - )

1- Bf(Bs->Ds(*) + Ds

(*) - ) / 2

(first proposedby Y. Grossman)

25

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.


-(*))

Y(5S), 1.86 fb-1

26

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/ )

27

3. Bs -> DsJ+ - (4 states).

Interesting physics issues, critical test of DsJ nature.

Inclusive DsJ production study?


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).

28

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

~

29

5. Bs -> Ds+ l- , Bs -> Ds*

+ l- (Bs->K+ l- ?).

7. Bs lifetime measurement.


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 … .

30

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%

31

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 (???).

32

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

33

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.

34

Yes, we can.

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

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

__ _ _

36

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.

37

Background slides

/ 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

dz resolution

dz resolutoin

SuperBSVD3modSVD3

For 0.2GeV 0.5GeV 1.0GeV 2.0GeV

dz

T.Kawasaki,Atami BNM2008Jan 2008

A. Drutskoy, University of Cincinnati

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