Recents results from Run 1

1
B Physics results from CDF
Daniela Bortoletto Purdue University

• Introduction
• Recents results from Run 1
• ? 100 pb-1 collected between August
  1992-February 1996.
• Measurement of the B production cross section
  ?test of QCD
• Searches for radiative penguin decays ? sensitive
  to new physics
• The measurement of sin(2?) ? CP violation
• Future prospects in Run II
• March 2001
• CDF/D0 expects to collect 2 fb-1 in two years

Moriond EWK March 2000
2
B Physics and CKM matrix

• The goal of B-physics is to over-constrain the
  unitarity triangle to test the CKM ansatz or to
  expose new physics

Vud VubVcd VcbVtdVtb0
V?td,ts
(?,?)
d(s)
b
t
?
b
t
d(s)
B???
Vtd,ts
?
(1-?-i?)
(?i?)
?
B?J/?K0s
B?DK
?
?
(1,0)
(0,0)

Moriond EWK March 2000
3
Hadron collider B-physics

• The strong interaction produces b quarks which
  then fragment into b-hadrons
• The lowest energy states decay weakly
• Test of QCD (unique to hadronic machines)
• mbgt?QCD? Perturbation theory can be used to
  estimate inclusive b production
• b production at the Tevatron is dominated by
  gluon processes ?Probe gluon structure functions

• Study of weak decays and unique capabilities for
  Bs, ?b and Bc which are not produced at B
  factories running at the ?(4S)

4
Hadron colliders challenge

• Large production cross section
• Even larger inelastic cross section (S/B?10-3) ?
  specialized triggers
• Single lepton triggers ? BR(b ?? ?X) (23.1
  ?1.5) . Requiring pT(?)gt 7-8 GeV/c ? ltpT(b)gt ?
  20 GeV
• J/ ? ? ? ? - triggers ? Use clean signature of
  b ? J/? X . Requiring pT(2 ?)gt 1.5 GeV/c ?
  ltpT(b)gt ? 10 GeV
• In Run II, L2 trigger on displaced tracks (SVT)
  will allow CDF to trigger hadronic B decays and
  study B0 ???-,Bs ?Ds-K ...

At 1.8 TeV
At Z0
At ?(4S)

5
Run I CDF detector

• Crucial components for B physics
• Silicon vertex detector ? proper time
  measurements
• impact parameter resolution
• ?d(1340/pT) ?m
• typical 2D vertex error ?(r-?) ? 60
  ?m
• Central tracking chamber ? mass resolution.
  B1.4T, R1.4m (?pT/pT)2(0.0066)2?(0.0009pT)2
• typical J/?K0S mass resolution ? 10 MeV/c2
• Lepton detection (triggering and tagging)

Moriond EWK March 2000
6
B Production cross section

• The B meson cross section
• engineering number
• provides a check of NLO QCD calculations
• sensitive to gluon distribution functions
• In run 1A (?20 pb-1) CDF found the data to be ?
  2? NLO QCD predictions (?3)
• New analysis uses the full run 1 data sample and
  the decay B?J/?K.

Moriond EWK March 2000
7
B Production cross section

• Both ?s must be well measured in the SVX
• ct(J/?)gt100 ?m
• pT(K)gt1.25GeV
• Fit in 4 pT bins
• 6-9 GeV/c
• 9-12 GeV/c
• 12-15 GeV/c
• 15-25 GeV/c

Moriond EWK March 2000
8
B Production cross section

• The cross section is
• QCD NLO central value ? 1.2 ?b
• ?0(mb2pT2)1/2
• ?0.006
• mb4.75 GeV
• fu0.375
• Data is still higher than theory

Moriond EWK March 2000
9
B Production cross section

• Fully correlated Systematic errors 13.1
• Branching Fraction 10.6
• Kaon decay in flight 4.0
• reconstruction efficiency 3.1
• Luminosity 5.8

• Fully uncorrelated Systematic errors 2.8-3.6
• QCD scale 1.5-1.6
• Peterson 0.7-1.6
• Trigger efficiency 1.7-3.1

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10
Radiative Penguins

• Radiative penguins are sensitive to physics
  beyond the SM
• CP asymmetry in SM lt1
• Extraction of Vtd/Vts
• Inclusive b ? d ?/b?s? difficult
• Exclusive Bd ???/Bd?K0?
• Exclusive Bs ?K0?/Bs???
• CDF

Unique to CDF
Moriond EWK March 2000
11
Radiative Penguins

• I) Specialized ? trigger (22.3 pb-1 in Run 1B
  and 6.6 pb-1 in Run 1C).
• pT(?)gt10 (6) GeV/c 2tracks with pTgt2 GeV/c
• Energy resolution in EM calorimeter ? ?(MB)?100
  MeV/c2
• Ratios w.r.t. B ? e- D0 X (D0 ?K-?)
• II) ? conversions in the CDF inner detector
• trigger with pT gt 8 GeV/c electrons (74 pb-1)
• CTC pT resolution??(MB)?45 MeV/c2
• Ratios w.r.t. to B ? J/?K ? ee-K

Position of conversions

CTC inner wall
12
Radiative Penguins

• Method II
• Reconstruct K ?K ?- and ? ?KK- using SVX
  tracks
• ct(B)gt100 ?m c
• B isolation
• Systematic errors dominated by statistics of
  J/?K(20), Br(B??K) (10) and fs/fu (18)

• Method I
• Reconstruct K ?K ?- and ? ?KK- using SVX
  tracks
• impact parameter cut
• B isolation, alignment between pT and VT
• Systematic errors dominated by statistics of
  eD0(20), f(12), Br(B?eD0X) (14) and fs/fu
  (18)

13
Radiative Penguins

• Combining the two searches CDF finds
• 2 candidates for Bd?K? while we were expecting
  B0.6 ? 0.3.
• 0 candidates for Bs??? while we were expecting
  B0.1 ? 0.1 .

Moriond EWK March 2000
14
? Conversions
1 candidate
0 candidate
28 candidates
34 candidates

15
? Trigger

16
Radiative Penguins

• Search for ?b???
• Polarization of ? is sensitive to New Physics
• Use only conversion trigger
• Tracks are not required to be in SVX
• Expectations for 2fb-1
• Bd?K? 1000 events
• Bs??? 400 events
• Bs ?K? 10 events
• ?b??? Studies are in progress to find optimal
  trigger

17
Measurement of sin2?

• Requires
• Reconstruction of the signal B0/B0? J/?K0S
• Measurement of the proper time t
• Flavor tagging to determine if we had a B0 or a
  B0 at the time of production
• The effectiveness of flavor tagging algorithms is
  quantified by
• Measured ACP is reduced by D, while ?D2 effects
  ? A and ?(sin2?)

18
Measurement of sin2?

• CDF pp?bb Abe et al. PRL. 81, 5513 (1998) (June
  1998)

• 198 ?17 B0/B0 ?J/?K0S candidates with both muons
  in the SVX ( S/B ? 1.2). Measure asymmetry with
  Same side tagging
• Dsin2?0.31? 1.1 ? 0.3.
• Using D0.166 ? 0.018 (data) ? 0.013 (MC) from
  mixing measurement MC

sin2?1.8? 1.1 ? 0.3
19
Improved measurement

• Accepted for publication in PRD, T. Affolder et.
  Al., FERMILAB-Pub-99/225-E, hep-ex/9909003
• Improve statistical significance
• Add candidate events not fully reconstructed in
  the SVX
• Double the signal to 400 events but additional
  signal has larger ?(ct)
• Use two additional flavor tag methods to
  establish b flavor at production (Increase ?D2)
• soft lepton and jet charge (both opposite side
  tagging methods used for the mixing analysis)
• calibrated using B-?J/?K-
• Use a maximum likelihood method to combine the
  tags. Include terms in the likelihood for
• Account for detector biases
• Prompt background
• Long lived background

20
J/?K0S Signal sample

• CDF run1, L110 pb-1
• 202 events with both muons in SVX ? ?(ct)? 60 ?m.
  
• 193 with one or both muons NOT in SVX ? ?(ct)?
  300-900 ?m

Both ? in SVX
202 ?18 events
395 ?31 events
S/B0.9
One or Both? not in SVX
193?26
S/B0.7
S/B0.5

• Plot normalized mass
• M????-MB/ error on M

21
Flavor tagging methods

• We must determine if we had a B0 or a B0 at the
  time of production.
• Opposite-side flavor tagging (OST)? bb produced
  by QCD? Identify the flavor of the other b in the
  event to infer the flavor of the B0 /B0? J/?K0S.
  At CDF? 60 loss in efficiency due the acceptance
  of the other B0.
• Lepton tagging
• b?? X ?b
• b?? -X ?b
• Jet charge tag
• Q(b-jet) gt 0.2 ?b
• Q(b-jet) lt- 0.2 ?b

B0(bd)? J/?K0S
?
?-
?
K0S
?-
Opposite side b
?
Q(b-jet)gt0.2
22
Same side tagging

• Same side flavor tagging (SST). Exploits the
  correlation between the charge of nearby ? and
  the b quark charge due to fragmentation or B
  production (Gronau,Nippe,Rosner)
• Correlation due to excited B production
• B (I1/2) resonance B- ?B0 ?-

No K/? separation ? higher correlation for
charged B
d
23
Flavor Tagging Summary

• Soft lepton e pT(e)gt1 GeV/c ? pT(?)gt2
  GeV/c
• ? (5.6?1.8) D (62.5 ? 14.6) ?D2 (2.2
  ?1.0)
• Jet charge
• If there is a soft lepton do not use jet charge
• ? (40.2 ? 3.9) D (23.5 ?6.9 ) ?D2
  (2.2 ?1.3)
• Same side pion tagging
• ?(35.5?3.7) D (16.6 ?2.2 ) in SVX
• ?(38.1?3.9) D (17.4 ?3.6 ) not in SVX
• Combined flavor tagging power including
  correlations and multiple tags
• A sample of 400 events has the statistical power
  of 25 perfectly tagged events
• About 80 of the events have a tag

?D2 (2.1 ?0.5)
?D2 (6.3 ?1.7)
24
Measurement of sin2?

• The minimization of the likelihood function
  yields
• sin2?0.79?0.39(stat)?0.16(syst) Statistical
  error gtsystematics.
• Time integrated measurement
• sin2?0.71?0.63 (stat?sys)
• Using Feldman and Cousing frequentist approach
• 0ltsin2?lt1 _at_93C.L.
• New world average (Taipei) includes this
  measurement and a new Aleph results
• sin2?0.82 ?0.38

25
Results in ? and ? plane
1? bounds

• CDF sin2 ? measurements ? fourfold ambiguity ?,
  ?/2- ?, ??, 3?/2-?
• Solid lines are the 1 ? bounds, dashed lines two
  solutions for ? for ?lt1, ?gt0 (shown)
• two solutions for ?gt1, ?lt0 (not-shown)

26
Run II upgrade

• New silicon tracking system ? 3 D information
• SVX II 5 layers, 96 cm, r-? and r-z readout
• ISL 2 additional layers
• L00 at r1.4 cm
• New central drift chamber ? maintain run 1
  tracking efficiency and resolution
• New trigger
• L1 tracking trigger
• L2 trigger on displaced tracks ? trigger on
  hadronic B decays

• Time off flight ? 2 ? K/? separation for plt1.6
  GeV/c
• gt2 fb-1 of data

27
Run II expectations

• Sin 2 ? from B0/B0 ?J/?K0S
• for 10K events, ?D2 6.7 (2.4 TOF) ? ?(sin2
  ?)?0.084
• B??? expect 8400-15200 events if BR1?10-5
• for 5K events , ?D29.1 ? ?A(??)?0.1-0.15
• Modes to study ?
• Expect 6000 Bs?J/?? where asymmetry would be sign
  of new Physics

• Bs oscillations
• Expected signal 20,000 Bs ? Ds-?, Ds??-? with
  Ds ? ??, KK
• Proper time resolution with L00
• Flavor tagging effectiveness
• ?D211.3 with TOF (5.7 with old baseline)

Sensitive to xslt63 if S/N2/1 Sensitive to xslt56
if S/N1/2
20ltxslt 30.8 _at_96 C.L.
28
Conclusions

• Important contribution to B physics using run I
  data
• Discovery of the Bc through
• First measurement of sin(2?) from
• Precise measurements of B hadron lifetimes
• Neutral B meson oscillation ( measurement of ?md,
  limits on ?ms)
• Studies of b-tagging methods
• Searches for rare B decays
• (FCNC
  )
  
• B production
• Excellent prospects for Run II