A. Drutskoy University of Cincinnati
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Transcript of 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.
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
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)
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
_ _
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
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
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).
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
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)
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
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
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
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.
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
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
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
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
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
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
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
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->+)
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
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 ) %
After continuum subtraction and efficiency correction:
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- +
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
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 ) %
After continuum subtraction and efficiency correction:
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)
+-
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
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
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
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)%
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
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*
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
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
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
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
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
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
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
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
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
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,
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
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.
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
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.<=
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
~
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
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
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
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
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.
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
Background slides
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy
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.
Bs physics at Y(5S), SLAC seminar, Jan 17, 2006, A. Drutskoy