a. drutskoy university of cincinnati

A. Drutskoy University of Cincinnati

Bs physics at Y(5S) in Belle experiment

January 17, 2006, SLAC.

SLAC Experimental Seminar

Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy

Outline

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

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

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

Search for rare Bs decays.

Data taking.

Introduction.


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

B0 = s b , B0 = s b _ _

s s

_

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)


_ _

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

Bs5365.5 1.3 438 851

Bs* 5416.6 3.5 51 4 415


Electron and positronbeam energies have tobe increased by 2.7% (same Lorentz boost = 0.425) to move from Y(4S) to Y(5S).

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


3 days of engineering run at Y(5S) : June 21 – June 23.

Plan for 3 day engineering runs:

1. Energy scan: five points with ~30 pb-1 at each point:10825, 10845, 10865, 10885 and 10905 MeV.

2. Data taking at Y(5S) peak; to collect integral lumi ~2 fb-1 .

Results:

Y(5S) peak position ECM=10869 MeV was chosen from energy scan.

Integrated luminosity of ~1.86 fb-1 (ECL lumi) was taken !!!

Maximum luminosity ~13.9 /nb/sec, almost 100% of Y(4S) specificluminosity (taking into account smaller currents). Belle can take

1 fb-1 per day at Y(5S) or even more.

Very smooth running, all goals are reached.

Engineering run at Y(5S)


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


Number of Bs in dataset

To obtain the full number of initial Bs* Bs* events in our data sample

we should go through steps:

1. Obtain the number of hadronic events in Y(5S) dataset.2. Subtract u,d,s,c continuum using continuum data below Y(4S) with luminosity scale factor.

3. Calculate the ratio N(Bs(*)Bs

(*)) / N(bb) using inclusive Ds and D0

spectra.

4. Calculate the ratio N(Bs*Bs*)/ N(Bs(*)Bs

(*)) using reconstructed

exclusive events.

To calculate any exclusive branching fraction we must know

the full number of Bs* Bs* events.

To calculate any inclusive branching fraction we must know

the full number of Bs mesons.


Number of bb events.

2 ~ 1/Ecm

R = (hadrons) / ()

Ncont(5S) = Ncont(E=10.519)* L(5S) / L(cont) * (Econt/E5S)2 (5S/ cont)

Y(5S) :

Cont : Lumi = 3.670 ± 0.001 (stat) fb-1

(1.857/3.67)*(10.5189/10.869)2 = 0.4740± 0.0019

Nbb(5S) =

CLEO : 0.42 fb-1 Nbb(5S)/ fb-1 = 310,000 ± 52,000

Lumi = 1.857 ± 0.001 (stat) fb-1

561,000 ± 3,000 ± 29,000

5S/ cont = 1.007 ± 0.003

Nbb(5S) / fb-1 = 302,000 ±15,000


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 luminosity ratio:

Using MC simulation CLEO obtained (0.6 ± 1.1)% correction for new channels opening.That correction was applied to these numbers.

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.

Ratio of Bs(*) Bs

(*) pair number to all bb pair number fs = N(Bs

(*) Bs(*)) / N(bb) can be obtained from:

Bf (Y(5S) -> Ds X) / 2 = fs Bf (Bs -> Ds X) + (1- fs) Bf (B -> Ds X)xx


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

Y(5S)

Ds-> +

3775 ± 100 ev

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

Bf (Bs -> DsX) = (92 ± 11) %

PDG : Bf (Ds-> +)=(3.6 ± 0.9)%

Sum: Bf(Ds-> +) = (4.4 ± 0.5)%

Bf(Ds-> +)=(4.8 ± 0.6)% Babar :

Babar :CLEO : Bf (B -> DsX) = ( 9.0 ± 0.3 ±1.4 )%

Bf (B -> DsX) = ( 8.94 ± 0.16 ± 1.12 )%

After continuum subtraction and efficiency correction:

Bf (Y(5S) -> Ds X) 2 = (22.6 ± 1.2 ± 2.8) %CLEO measured: Bf (Y(5S) -> Ds X) / 2 = (22.35 ± 2.1 ± 4.95)%

fs = (16.4 ± 1.4 ± 4.1 )%=>

Using Ds mesons CLEO measured fs = (16.0 ± 2.6 ± 5.8 )%

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


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

Theory :

PDG:

Bf (Bs -> D0X) = (8 ± 7) %

hep- ex/0508047 CLEO

Bf (B -> D0X) = (63.7 ± 3.0) %

Bf (D0 -> K- +) = (3.81 ± 0.09 ) %


Bf (Y(5S) -> D0 X) 2 = (53.3 ± 2.0 ± 2.9) %

Then we obtain ratio fs = N(Bs(*) Bs

(*)) / N(bb) :

fs = (18.7 ± 3.6 ± 6.7 )% Syst. error dominates by N(bb).

Using Ds mesons CLEO measured fs = (16.0 ± 2.6 ± 5.8 )%

P/Pmax< 1

Y(5S)

55009 ± 510 ev

D0 -> K- +


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

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 = (1.068 ± 0.086 ± 0.057) %

Good agreement with expectations => bb number is correct

Assuming approximately 17% Bs(*)Bs

(*) production over bb :

Bf ( Bs -> J/ X) = ( 0.94 ± 0.51 ± 0.37 ) %

P/Pmax<0.5

446±28 ev

Y(5S)

+-


Exclusive analysis: signature of fully reconstructed Bs decays

BsBs , Bs*Bs , Bs*Bs*

Detailed MC event simulation and reconstruction with Belle detector was

performed. Figures are shown for decay mode Bs -> Ds- + with Ds

- -> - .

Mbc = E*beam2 – P*B

2

Bs signal can be well separated for BsBs, Bs*Bs and Bs* Bs* final states.

e+ e- -> Y(5S) -> BB, B*B, B*B*, BsBs, Bs*Bs, Bs*Bs*where B* -> B and Bs* -> Bs

Mbc vs E


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/ modesBs physics at Y(5S), SLAC seminar, Jan 17, 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 channels.

MC

Bs -> Ds+ -

9 events in Bs* Bs*

Bs -> Ds*+ -

4 events in Bs* Bs*

Taking full number of Bs from 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* channel dominance was also observed by CLEO (next slide).

Bs -> Ds(*)+ -

Bs -> J/

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


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

- 13 -

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

Small signal, Nev= 1.3 ± 2.0 (6± 96)%

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


MBC distribution, sum of all Bs decay modes

Mbc = E*B2 – P*B

2 Mbc = (E*B+ Epeak)2 – P*B2

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

M (Bs*) = 5418 ± 1 ± (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 = 92,000 ± 8,000 ± 23,000

f(Bs*Bs*) = (94 ± 69)%

N ev = 86,500 ± 7,500 ± 22,500Bs* Bs* channel

Lumi = 1.857 fb-1


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

MC

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

K- : tight ID(K/),

Fox2 < 0.4,

|cos | < 0.8

Bs ->

|cos | < 0.5

Bgr. ~ 0.14 ev.Est. sign.~ 0.7 ev.

Bgr. ~ 0.15 ev.Est. sign.~ 0.4 ev.

Bs -> K+ K-

Fox2 < 0.3,


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.


Exclusive Bs -> Ds(*)+ Ds

(*)- decays

Fox2 < 0.4

Angle between B thrusts: |cos | < 0.8

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 30 fb-1:

Bs->Ds(*) + Ds

(*) - decays are CP- even states

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

Bf (Bs->Ds(*)+ Ds

(*)- ) = (12 ± 5 )%

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

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


~

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

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 violation SUSY ( x M()).

90% CL UL with 1.86 fb-1 :Bf(Bs -> ) < 0.56 x 10- 4. Better than PDG limit : < 1.48 x 10- 4

MCFox2 < 0.5 |cos | < 0.8

Bs ->

Exclusive Bs -> decay


Signals with 50 fb-1

It seems, very strong physics program can be performed with 50 fb-1:

Bs -> Ds(*)+ Ds

(*)- - CP eigenstate

Bs -> K+ K- - penguin

Bs -> Ds+ K- - Cabibbo suppressed

Bs -> - radiative penguin

Bs -> DsJ - tree with DsJ

Bs -> Ds+l - - exclusive leptonic

Bs -> - intrinsic penguin

Bs lifetime

Bs semileptonic

Bs -> D0 KS0 - color suppressed


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 measured: fs = (16.4 ± 1.4 ± 4.1 )%

Good agreement with published CLEO results is obtained in bothinclusive and exclusive analyses. Our Y(5S) dataset is 4.4 times largerthan CLEO dataset, providing better accuracy.

Many new interesting results can be obtained with 50 fb-1. Significant

signals are expected in many Bs decays with 50 fb-1 (maybe 30 fb-1)

Engineering runs demonstrated, that background level is not large forstudied decay modes.

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


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.


a. drutskoy university of cincinnati

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