# Presentation: 024501

## Recent b-physics Results from CDF

**Recent b-physics Results from CDF**

**Lake Louise Winter Institute:  20-26 February  2000**

**Giorgio Apollinari**
**Fermilab**
**for the CDF Collaboration**
- Introduction
- CP Violation and b Mixing
- Rare B Decays
- Polarization in B     V V
- Future Prospects

## Introduction

- Tevatron Advantage
- Large production:
- 
- All b-hadron states produced:
- Bu,Bd,Bs,Bc,b
- Tevatron disadvantage:
- Large Background (in~ 1000 x bb)
- b-production peaked at low pt
- Unknown initial state
- Experimental Strategies:
- Specialized triggers
- dilepton & single lepton
- J/’ from (ee, B mixing from (e, ee, 
- b-hadron semileptonic decays
- Precise Secondary Vertex reconstruction

## Introduction

- Examples of Run I b-physics results from CDF

## CP Violation 

- SM with 3 generations and mixing among the quark families (mass eigenstates  weak eigenstates) can accomodate CP violation** **if the complex phase in the unitary mixing matrix  is  0CP.
**	**
**	**
- In the B0d,s case, like in the Ks system,higher order weak interactions mix meson and anti-mesons states.

## CP violation can be manifested as:
CP violation in the decay if |A(f)|/|A(f)|   1
CP violation in the mixing if the neutral mass eigenstates are not CP eigenstates
CP violation in the interference between decays with and without mixing to a CP eigenstate.
Vtd introduces a complex phase in the box diagram and the interference between the two terms leads to a time dependent asymmetry
Golden mode:

**B****0**

**B****0**

**J/**** K****0****s**

**CP Violation **

- CP violation can be manifested as:
- CP violation in the decay if |A(f)|/|A(f)|   1
- CP violation in the mixing if the neutral mass eigenstates are not CP eigenstates
- CP violation in the interference between decays with and without mixing to a CP eigenstate.
- Vtd introduces a complex phase in the box diagram and the interference between the two terms leads to a time dependent asymmetry
- Golden mode:

**B****0**

**B****0**

**J/**** K****0****s**

## Unitary Triangle representation
from unitarity of CKM

S. Mele 	CERN-EP-98-133, 1998 		sin2=0.75 0.09 
Parodi et al. hep-ph/9802289 		sin2=0.725 0.06
Ali et al.  	0.52<sin2<0.94

- Unitary Triangle representation
- from unitarity of CKM
**S. Mele ****	****CERN-EP-98-133, 1998 ****	****	****sin2********=0.75******** 0.09 **
**Parodi et al. hep-ph/9802289 ****	****	****sin2********=0.725******** 0.06**
**Ali et al.  ****	****0.52<sin2********<0.94**

## Time integrated ACP does not vanish at hadron colliders (since the B0B0 system is not produced in a coherent state)

				PDG 98

A measurement of the proper time dependence of ACP(t) is preferable
more statistical power
reduces effect of combinatorial background at small t 

- 				PDG 98
- A measurement of the proper time dependence of *A**CP**(t)* is preferable
- more statistical power
- reduces effect of combinatorial background at small t

**CP Violation **

## Measurement of ACP(t) requires 3 pieces of information for each decaying meson:
Signal Reconstruction
Flavor of original meson
Use flavor tagging
Proper time of decay
Reconstruct the B vertex
Tagging algorithms characterized by efficiency  and dilution D
AobsCP= D ACP
D = dilution
Ntot=Total number of events
NW=Number of wrong tags
NR=number of right tags
D=2P-1 (P=prob. of a ccorrect tag)
Best tagging has highest D2   

- Measurement of *A**CP**(t)* requires 3 pieces of information for each decaying meson:
- Signal Reconstruction
- Flavor of original meson
- Use flavor tagging
- Proper time of decay
- Reconstruct the B vertex
- Tagging algorithms characterized by efficiency  and dilution *D*
*A**obs**CP**= D A**CP*
*D* = dilution
- Ntot=Total number of events
- NW=Number of wrong tags
- NR=number of right tags
- D=2P-1 (P=prob. of a ccorrect tag)
- Best tagging has highest ***D**2   *

**CP Violation **

**Opposite Side Lepton and/or Kaon tagging****  ****(OST)**
- Use decay of the away side B-hadron
**Opposite Side Jet-Charge tagging**
- Reconstruct the away-side B-hadron and use statistical methods to determine the flavor
**Same Side tagging (SST)**
- Uses correlation with p produced along with the B-hadron being tagged
- Correlation from the B** and fragmentation
- All tagging methods cross-checked on mixing analysis

## Same Side Tagging
uses correlation between the charge of the nearby p and the b quark charge due to fragmentation or B** production 
Gronau, Nippe, Rosner
+ (K+) tags a B0 and a - (K-) tags a B0
better acceptance (efficiency) than OST

- Same Side Tagging
- uses correlation between the charge of the nearby p and the b quark charge due to fragmentation or B** production
- Gronau, Nippe, Rosner
- + (K+) tags a B0 and a - (K-) tags a B0
- better acceptance (efficiency) than OST

**CP Violation **

**P****B**

**P****tr****rel**

**P****B****+ P****tr**

**P****tr**

**Cone ********R=0.7**

**B direction**

- Track Selection
- R<0.7 from B meson
- pT > 400 MeV
- >2 SVX hits
- consistent with primary vtx in *r-*** and *z*
- minimum prelT

## CP Violation 

**CP Violation **

- SST and		        mixing measurement provides information on *D*

**Amplitude**
**gives D**

**Mostly Charge B’s**

**Mostly Neutral B’s**

- F.Abe et al., Phys. Rev. Lett 80, 2057 (1998)
-         Phys. Rev. D 59 (1999)

## CP Violation 

**CP Violation **

- First measurement of sin2
- 198   17 B0,B0 events
- Asymmetry measured with SST
*D* sin2=0.31   0.18   0.03 (syst.)
*D*=0.166  0.018  0.013
- sin2=1.8   1.1  0.3
- Improvements
- add candidates not fully reconstructed in SVX
- ~400 events, larger (t)
- Add Opposite Side Taggers (OST)
- calibrate using    J
- Multiple taggers
- use maximum L to include terms for possible detector biases, prompt bkg. and long-lived bkg.

- F.Abe et al., Phys. Rev. Lett 81, 5513 (1998)

## CP Violation 

**Both ******** in SVX**

**One or Both******** not in SVX**

**395 ******** 31 events**

**S/B=0.7**

**S/B=0.9**

**S/B=0.5**

**202 ******** 18 events**

**193******** 26**

- Full Run I signal sample

## CP Violation 

- Soft Lepton Tagging (SLT)
- Identify flavor of opposite B Hadron through semileptonic decay
- Semileptonic branching ratio leads to ~6%.
- Electron Selection
- Central track (pt>1 GeV) matched to EM shower.
- Muon Selection
- Central track (pt>2 GeV) matched to muon stub in the central muon chambers.
- When present *D=62.5 **** 14.6 %*

- Jet Charge Tagging (JTEQ)
- Identify flavor of opposite B Hadron through charge of opposite jet
- Use a variant of the JADE track cluster algorithm
- optimized for low pt jets
- Weight individual track charges by
- transverse momentum
- impact parameter (*T**i** ~ 0* for displaced tracks)
- Qjet>0.2 identifies a b jet
- Qjet<-0.2 identifies a b jet
- |Qjet|<0.2 is a no-tag
- 40% of J/Ks0 have a JTEQ tag.

- F.Abe et al., Phys. Rev. D60 (1999)

## Taggers Calibration on un-mixing B+/B- samples:

- Taggers Calibration on un-mixing B+/B- samples:

**CP Violation **

**JETQ Tagging**

**SLT Tagging**

## Combination of flavor taggers
Correlations 
 Multiple tags

Fixing md=0.4640.018 ps-1

md floating

- Combination of flavor taggers
- Correlations
-  Multiple tags
- Fixing md=0.4640.018 ps-1
- md floating

**CP Violation **

- Time integrated

- T. Affolder et al.,FERMILAB-Pub-99/225-E

## CP Violation 

**CP Violation **

- Systematics
- Dilution ~0.16
- dominated by statistic in the calibration samples
-  Others ~0.02
- Statistical errors larger than systematics

-  Confidence Limit
- 0<sin 2 <1 at 93% CL
- if sin2 =0, the probability of observing sin2>0.79 is 3.6%

## Conclusive Evidence for CP violation in B sector
Summary of sin 2 determinations

OPAL							Euro. Phys. C5, 379 (98)				
CDF(Partial)						PRL 81, 5513 (98)

CDF(Final)						hep-ex/9909003

ALEPH (Prelim.)					BCP3 Taipei, Dec. 99

AVERAGE 

- Conclusive Evidence for CP violation in B sector
- Summary of sin 2 determinations
- OPAL							Euro. Phys. C5, 379 (98)
- CDF(Partial)						PRL 81, 5513 (98)
- CDF(Final)						hep-ex/9909003
- ALEPH (Prelim.)					BCP3 Taipei, Dec. 99
- AVERAGE

**CP Violation **

## b Mixing

- Neutral B Meson flavor oscillations due to 2nd order Weak Int.
- measure proper time dependence
- produce B0, measure probability P(B0      B0) as a function of the proper decay time t.
- needs
- flavor of B at production
- other B in the event can be used
- flavor of B at decay
- proper decay time t of B
- if decays are classified as “mixed” and “unmixed”, then measure

- ms > 5.8 ps-1 at 95% C.L.
- F.Abe et al., Phys. Rev. Lett. 82, 3576 (1999)

## Flavor Changing Neutral Current
Limits on Bo/Bs     +-
F.Abe et al, PRD 57, R3811 (1998)
Allowed by SM, 3 orders of magnitude below current sensistivity
Some SUSY models predict substantial enhancement

- Flavor Changing Neutral Current
- Limits on Bo/Bs     +-
- F.Abe et al, PRD 57, R3811 (1998)
- Allowed by SM, 3 orders of magnitude below current sensistivity
- Some SUSY models predict substantial enhancement

- Lepton Number Conservation
- Limits on Bo/Bs      +-
- F.Abe et al, PRL 81, 5742 (1998)
- Forbidden in SM
- Sensitive to new particles (e.g. Pati-Salam Leptoquarks)

- F. Abe et al., Phys. Rev. D 57, R3811 (1998)

- F. Abe et al., Phys. Rev. Lett. 81, 5742 (1998)

## Non Resonant B    K and ”charmless” decays
Allowed by SM, sensitive to presence of new particles

- Non Resonant B    K and *”charmless”* decays
- Allowed by SM, sensitive to presence of new particles

## B     VV Polarization

- Decay distributions in
- 	described by 3 complex amplitudes

- Yields CP Composition
-      - is parity-odd (L=1)
- Is                             a pure CP state?

## B     VV Polarization

## Tevatron Run II B-Physics

- CDF Upgrades
- New Silicon Tracker, 96 cm long, r-z and r-measurements
- ~2 times more acceptance
- New dead-time-less trigger
- Tracking information used at L1
- Use Silicon information at L2
- Purely hadronic B trigger possible
- Time-of-flight
- 2 K/ separation at p<1.6 GeV/c
- D0 Upgrades
- Superconducting Solenoid
- Central Fiber Tracker
- Silicon Microstrip Tracker

## Precise Measurement of |Vtd/Vts|
              flavor oscillation and                , sensitive to xs<63
Radiative Decays:
Precise Measurement of  CP violation and sin 2 in
Observe CP violation and measure asymmetry in 
Measure CP asymmetry in
Observe decay modes related to the angle 


Rare Decays

Study Bc meson and b-barions

Unique to Hadron Machines

-               flavor oscillation and                , sensitive to xs<63
- Radiative Decays:
- Precise Measurement of  CP violation and sin 2 in
- Observe CP violation and measure asymmetry in
- Measure CP asymmetry in
- Observe decay modes related to the angle 
- 
- Rare Decays
- Study Bc meson and b-barions
- Unique to Hadron Machines

**Tevatron Run II B-Physics**

## Tevatron Run II B-Physics

**Tevatron Run II B-Physics**

- Expectations for CP modes
- sin 2 from B0      J/ Ks0
- ~10K reconstructed J/ Ks0
- Taggers calibrated on
- 40K B+       J/ K+
- 20K B0       J/ K0*
- D2=6.7% (add 2.4% with TOF)
- (sin2)~0.084
- Asymmetry in B0/ B0    +- (sin2)
- 8K-15K signals (if BR~10-5)
- If signal 10K and D2=9.1%
- A(+-) ~ 0.09
- sin  modes
- ~700 events of  Bs0/Bs0      Ds+K-

**Next phase in b-physics investigation  is around the corner**