A. Drutskoy University of Cincinnati

A. Drutskoy University of Cincinnati

Results from the Y(5S) Engineering Run at Belle

July 7, 2006, Fermilab.

Joint Experimental-Theoretical Seminar

Fermilab seminar Results from the (5S) Engineering Run at Belle , July 7, 2006 A. Drutskoy

Outline

Number of bb events at Y(5S) dataset.

Inclusive production of Ds, D0 and J/ at Y(5S).

Exclusive decays Bs-> J/ (/) and Bs-> Ds+(*) - (/-).

Search for rare Bs decays.

Data taking.

Introduction.

All results in this talk are Belle preliminary.


Results are based on 1.86 fb-1 dataset taken at Y(5S).

CLEOPRL 54, 381 (1985)

(5S)

Introduction

e+ e- ->Y(4S) -> BB, where B is B+ or B0 meson

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) ~116 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 the 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)

Masses, widths, lifetimes, CM momenta

Particle Mass,

MeV/c2

Width,

MeV/c2

M,

MeV/c2

c,m

Pcm(BB),

MeV/c

Y(4S) 10580.0 3.5

20 2 4

Y(5S) 10865 8 110 13

B+ 5279.0 0.5 502 1282

B0 5279.4 0.5 462 1281

B* 5325.0 0.6 45.8 0.4 1075

Bs5366.0 0.8 438 851

Bs* 5416.6 3.5 51 4 415


Belle

Y(5S) Engineering Run at the KEKB e+e- collider

3.5 GeV e + 8 GeV e

-

Electron and positron beamenergies were increased by 2.7%(same Lorentz boost = 0.425)to move from Y(4S) to Y(5S).

3 days of engineering run at Y(5S) : June 21 – June 23 , 2005 => 1.86 fb-1 ; Very smooth running !Almost 100% of Y(4S) specific luminosity. Belle can take > 1 fb-1 per day at Y(5S).


2005: Energy scan (30pb-1 at 5 points) : Y(5S) peak position ECM = 10869 MeV chosen.

Beam currents were lowered by ~10% to keep background level under control.

Energy scan

Non-relativistic Breit-Wigner to describe signal and Const to describe background.

Shape is slightly asymmetric(?). Energy scan was performed to find the best position for following Y(5S) runs. Not enough energy range to measure Y(5S) mass and width.


No modifications arerequired for Belle detector, trigger systemor software to move from Y(4S) to Y(5S).


Beam currents werelowered :backgrounds are similar to Y(4S) runs


Y(5S) Engineering Run

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 for the first time (4S).

~22 fb-1

Correction factor(1.056)is necessary for 5S rundue to smaller Bhabha Cross section.

New 2006 run at Y(5S) at Belle D

aily

lu

min

os

ity

Belle collected more data at Y(5S): June 9 - June 31, 2006 => 21.7 fb-1



New 2006 run at Y(5S) at Belle

• Integrated luminosity reached 600 fb-1 on May-31st .

Belle

Babar

~630fb-1

May-31st

Belle integrated luminosity at Y(4S)


http://accmac-server.kek.jp:8080/kekb/Luminosity/graph.gif

Move to Test Stand for Cool-down & High Power Test

Mt. TsukubaCrab cavity for HER

Luminosity will be increased ~ twice after crab cavity installation.


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)


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

- - - -


Luminosity ratio L (5S) / L (continuum).

Luminosity ratio can be checked using the ratio of normalized momentumdistributions of fastest charged track, fastest K0 and D0 mesons.

We obtained energy corrected luminosity ratio:

0.477 ± 0.0050.471 ± 0.005 0.471 ± 0.005

=> Good agreement within errors with energy corrected luminosity ratio.

L (5S) / L (cont) = 0.4740 ± 0.0019


Inclusive analyses : selections

Particle ID:/K : standard ID(K/)

J/ -> + - :Standard Muon ID

D0 -> K+ - : no cuts

Ds -> :

| M(–M(K+K-) | < 12 MeV/c2 ~3|cos(heli) (Ds)| > 0.25 for + No continuum suppression cuts.


Inclusive analysis : Y(5S) -> Ds X , Ds ->

Y(5S)

Ds-> +

3775 ± 100 ev

P/Pmax< 1Theory : hep- ex/0508047 CLEO

Bf (Bs -> DsX) = (92 ± 11) %

Bf(Ds-> +) = (4.4 ± 0.6)%

PDG 2006:

Bf (B -> DsX) = ( 8.6 ± 1.2)%

After continuum subtraction and efficiency correction:

Bf (Y(5S) -> Ds X) 2 = (23.6 ± 1.2 ± 3.6) %

fs = (17.9 ± 1.4 ± 4.1 )%=>

Similarly, CLEO measured fs = (16.0 ± 2.6 ± 5.8 )%

Syst. err. dominates by Bf(Ds->+)

points:5Shist: cont


Inclusive analysis : Y(5S) -> D0 X , D0 -> K- +

Theory :

PDG 2006:

Bf (Bs -> D0X) = (8 ± 7) %

hep- ex/0508047 CLEO

Bf (B -> D0X) = (64.0 ± 3.0) %

Bf (D0 -> K- +) = (3.80 ± 0.07) %


Bf (Y(5S) -> D0 X) 2 = (53.8 ± 2.0 ± 3.4) %

fs = (18.1 ± 3.6 ± 7.5 )% Syst. error dominated by N(bb).

P/Pmax< 1

Y(5S)

55009 ± 510 ev

D0 -> K- +

=>

points:5Shist: cont


Combining with Ds result: fs = (18.0 ± 1.3 ± 3.2 )%

CLEO measurement: fs = (16.0 ± 2.6 ± 5.8 )%

Inclusive analysis : Y(5S)-> J/ X , J/ -> +-

Theory :

Bf(Bs-> J/ X)

Bf(B -> J/ X)= 1.00 ± 0.10

Bf (B -> J/X) = (1.094 ± 0.032) %

PDG:

Bf (J/ -> + - ) = (5.88 ± 0.10 ) %


Bf (Y(5S) -> J/ X) 2 = (1.030 ± 0.080 ± 0.067) %

Good agreement with expectations => bb number is correct

P/Pmax<0.5

446±28 ev

Y(5S)

+-

points:5Shist: cont


Signature of fully reconstructed exclusive Bs decays

BsBs , Bs*Bs , Bs*Bs*

Detailed MC event simulation and reconstruction with Belle detector was

performed. Figures 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 well separated.

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 MC

Exclusive analyses: selections

Particle ID:K/: standard ID(K/) ; standard lepton IDMasses:0 –> 3

KS –> + - 3K*0 –> K+ -–> 2.5+ –> + 0 , P() >150 MeV/c

–K+K- 3– 30 < M(+-) – M(J/) < 30 MeV/c2 3– 100 < M(e+e-) – M(J/) < 30 MeV/c2

Ds+ -> + , K*0 K+, Ks K

+ 3Ds*

+ -> Ds+ : M(Ds)- M(D*s), 2, P()>50 MeV/c

Continuum suppression:Angle between Bs thrusts: |cos< 0.8 for Ds

(*)+ - ; |cos| < 0.9 for J/ ;|cos| < 0.7 for Ds

(*)+ - ; |cos| < 0.6 for K*0 K+ modes ;

Fox2<0.3 for Ds(*)+ -/ -; Fox2<0.4 for J/ modesFermilab seminar Results from the (5S) Engineering Run at Belle , July 7, 2006 A. Drutskoy

Exclusive Bs -> Ds(*)+ - decays

BsBs , Bs*Bs , Bs*Bs*

Ds+ ->+ , Ds

+ -> K*0 K+, Ds+ -> Ks K

+

Clear signal at Bs* Bs* channel ; no signals in Bs* Bs and BsBs.

MC

Bs -> Ds+ -

9 events in Bs* Bs*

Bs -> Ds*+ -

4 events in Bs* Bs*

Taking # of Bs’s from the inclusive analysis:

Bf(Bs -> Ds+ - ) = (0.65 ± 0.21 ± 0.19)%

CDF measured Bf ratio, taking Bf(B0->D+-) from PDG: (0.40 ± 0.06 ± 0.13)%


Exclusive Bs-> Ds(*)+- and Bs-> J/decays

Ds+->+ ,Ds

+->K*0 K+,Ds+->KsK+

Clear signal at Bs* Bs* channel ; signals in Bs* Bs and BsBs channels are not seen.

Bs -> J/ Bs -> J/,

We can combine all shown channels to obtain quantitative Bs(*) parameters.

Bs* Bs* dominance was also observed by CLEO.

Bs -> Ds(*)+ -

Bs -> J/

7 events in Bs* Bs* 3 events in Bs* Bs*


CLEO: Exclusive Bs Signals at the (5S)

Pre

limin

ary

(5S) decay to Bs(*)Bs

(*) is dominated by the Bs*Bs* mode!

BsJ/' , J/+e+e-

K+K

* * *(5 ) , ,s s s s s sS B B B B B B

E beam

– E

cand

idat

e (G

eV)

Mbc (Bs candidate) (GeV)

BsDs(*) Ds*Ds

DsK+K0 K+K*0

* * *(5 ) , ,s s s s s sS B B B B B B E beam

– E

cand

idat

e (G

eV)

Mbc (Bs candidate) (GeV)

Nsignal = 4, Nbkg 0.1

Nsignal = 8, Nbkg 1

H. Vogel, CLEO, FPCP 2004 (obsolete), Korea, exclusive Bs decays


E distributions, sum of all Bs decay modes

Decay (5S) -> Bs* Bs* , with Bs* -> Bs

E peak = Ecm(accel.)/2 – Ecm(real)/2 – E()

E peak = – 47.6 ± 2.6 MeV

Nev= 1.3 ± 2.0 ev. => small signal

Potential models predict Bs* Bs*dominance over Bs*Bs and BsBs

channels, but not so strong.

5.408< MBC<5.429 GeV/c2

Bs* Bs*Nev=20.0 ± 4.8

6.7

5.384< MBC<5.405GeV/c2

Bs* Bs Bs Bs

5.36< MBC<5.38GeV/c2

N(Bs*Bs*) / N(Bs(*)Bs

(*)) = (94± 69)%


MBC distribution, sum of all Bs decay modes

Mbc = E*B2 – P*B

2 = M(Bs*)Mbc = (E*B+ Epeak)2 – P*B

2 = M(Bs)

Ecm = 10869 MeV ; E*B = Ecm/2

M (Bs*) = 5418 ± 1 ± 3 (acc. err) MeV/c2

Photon momentum is neglected => does not change Bs* mass position, only smearing.

M (Bs) = 5370 ± 1 ± 3 MeV/c2

Photon energy smearing does not change Bs mass position

CDF: M (Bs) = 5366.0 ± 0.8 MeV/c2

Bs* Bs*

- 0.08<E<- 0.02 MeV

Bs* Bs*

- 0.08<E<- 0.02 MeV

PDG: M (Bs) = 5369.6 ± 2.4 MeV/c2


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

fs = (16.4 ± 1.4 ± 4.1 )%

N ev = 101,000 ± 7,000 ± 19,000

f(Bs*Bs*) = (94 ± 69)%

N ev = 95,000 ± 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 )%

Exclusive Bs -> K+ K- and Bs -> decays

MC

Partner of B -> K+ - penguin decay Partner of B -> K* penguin decay

Tight cuts are used to suppress backgr.

Bs ->

Signal: 2 eventsBgr. ~ 0.14 ev.Est. sign.~ 0.7 ev.

Signal: 1 eventBgr. ~ 0.15 ev.Est. sign.~ 0.4 ev.

Bs -> K+ K-


Exclusive Bs -> Ds(*)+ Ds

(*)- decays

Bs-> Ds*+ Ds*-

Bs-> Ds*+ Ds-

Bs-> Ds+ Ds*

-

Bs-> Ds+ Ds

-

Ds+ -> + , K*0 K+, Ks K+

Bf(Bs->Ds+ Ds

- ) < 7.1% at 90% CL

Bf(Bs->Ds*+ Ds- ) < 12.7% at 90% CL

Bf(Bs->Ds*+ Ds*- ) < 27.3% at 90% CL

s

s

~ Bf(Bs->Ds

(*) + Ds(*) - )

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

(*) - ) / 2

Expected with 23 fb-1:

Bs->Ds(*) + Ds

(*) - decays are CP- even states

with large BF’s, leading to large s/s:

Bf (Bs->Ds(*)+ Ds

(*)- ) = (14 ± 5 )%

Expected (2 fb-1): ~ 0.5 events in each mode.

should be compared with direct s/s measurement to test SM.<=~


MC

E

Many “conventional” BSM models can be better constrained by B -> K* and

B->s processes, however not all. In some BSM models Bs -> provides the best

limit, in particular in 4-generation model (VTs) and R- parity violating SUSY ( x M()).

90% CL UL with 1.86 fb-1 : Bf (Bs -> ) < 0.56 x 10- 4.

PDG limit : Bf (Bs -> ) < 1.48 x 10- 4

MC

Bs ->

Exclusive Bs -> decay

Natural mode to search for BSM effects, many theoretical papers devoted to this decay.

In SM: Bf(Bs-> ) = (0.5 -1.0) x 10-6

BSM can increase Bf up to two orders


Tasks expected with 23 fb-1

It seems, very strong physics program can be performed with 23 fb-1:

Bs -> Ds(*)+ Ds

(*)- - CP eigenstate, s / s estimate

Bs -> K+ K- - penguin, to compare with B->K

Bs -> J/ (’/) - CP eigenstate

Bs -> - radiative penguin , to compare with B->K*

Bs -> DsJ - tree with DsJ , to test DsJ production mechanism

Bs -> Ds+l - - exclusive leptonic, SU(3) test

Bs -> - the best world upper limit (intrinsic penguin)

Bs lifetime - precision ~ 5% using same sign leptons

Bs semileptonic - accuracy ~ 5-10%, quark-hadron duality test

Bs -> D0 KS0 - color suppressed, no rescattering diagram


Bs -> Ds(*)+ (/)- - direct measurements with stat. error ~15%

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(5S) : B(l +) B(l +) / B(l +) B(l - ) ~ 10%

Comparison with Fermilab Bs studies.

Running at Y(5S) is a new tool to study Bs physics. First Belle

results are very promising. Collider exists => relatively low price.

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) Measurement of 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.

Conclusions

Significant exclusive Bs signals are observed in Y(5S) -> Bs* Bs* channel.

Combining all studied decay modes, mass of Bs* meson was measured:

M(Bs*) = 5418 ± 1 ± (acc. err) MeV/c2, and mass of Bs was measured:

M (Bs) = 5370 ± 1 ± 3 MeV/c2. Obtained Bs mass is in agreement with

recent CDF measurement M (Bs) = 5366.0 ± 0.8 MeV/c2.

Inclusive production branching fractions of J/, D0 and Ds mesons are

measured at Y(5S). Ratio of Bs meson production over all bb-events

is determined: fs = (16.4 ± 1.4 ± 4.1 )% (in good agreement with CLEO).

Many new interesting results can be obtained with 23 fb-1. Significant

signals are expected in many Bs decays with 23 fb-1. Engineering runs

demonstrated, that background level is not large for studied decays.

Rare Bs decays are searched for at Y(5S) for the first time.

Bs studies at e+ e- colliders running at Y(5S) have many advantages

comparing with hadron-hadron colliders: high efficiency of photonreconstruction; no problems with trigger efficiency; good K/ PID.


Background slides


CDF: Bs-> Ds-+ decays

Results with 119 pb-1 :

fs Bf( Bs -> Ds- +)

fd Bf( B0 -> D- +)

= 0.35 ± 0.05 ± 0.04 ± 0.09

Bf( Bs -> Ds- +)

Bf( B0 -> D- +)

From PDG : fs / fd = 0.270±0.028 ,

fs is rate of “b quark” -> Bs

= 1.4 ± 0.2(stat) ± 0.2(syst) ± 0.4(BF) ± 0.2(PR)

Uncertainty of absolute branchingfraction measurement dominates

already by 10% uncertainty of fs/fd.


CDF: Bs-> h+ h’- decays

Unbinned likelihood fit.fs Bf( Bs -> K+ K-)

fd Bf( B0 -> K+ -)

= 0.50 ± 0.08 ± 0.07

fs Bf( Bs -> K+ -)

fd Bf( B0 -> K+ -)< 0.11 (90%CL)

Bf( Bs -> + -)< 0.10 (90%CL)

Bf( Bs -> K+ K-)

No absolute branching fractions.Statistical separation of final states.


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A. Drutskoy University of Cincinnati