B Physics Review: Part II

1
B Physics Review Part II
Donatella Lucchesi INFN and University of
Padova RTN Workshop The 3rd generation as a
probe for new physics Bratislava, 4 6
July, 2003

• Review of Tevatron measurements
• B and ?b lifetimes and masses
• Bs Mixing
• New CDF results
• Bs and ?b yields
• J/? cross section
• D0 branching ratio and CP
• asymmetries

2
How do we collect b?

• Old style
• Di-muon trigger
• 2 muons Pt gt 1.5 GeV
• (RunI Pt gt 2 GeV)
• charmonium physics
• B lifetime, B mass, rare decays Bs???
• New era
• Multi-bodies Hadronic trigger (SVT)
• 2 tracks Ptgt2 GeV, dgt120 ?m, ?Ptgt5.5 GeV,
  Lxygt200 ?m
• All you can imagine with B?X where Xgt2
• A combination of Old and New
• Lepton Ptgt4 GeV (Run I Ptgt8 GeV) track Ptgt2 GeV
  dgt120 ?m
• B?lDX decays, flavor tagging optimization

3

D0 Results from J/? trigger
4

D0 Results from J/? trigger
5
B Mesons Mass Measurements
Decay modes
The current results
Best in the world
6
b Hadrons Lifetime Measurements
Is it still interesting?
Several decays channels are available at Tevatron
good test of the theory
7
b Hadrons Lifetime Measurement

• Experimental needs
• calibrate resolution
• understand the alignments
• ?? correction if not fully reconstructed decays

• Inclusive b lifetime b? J/? X

CDF result
? 1.527?0.033?0.033 ps
8
Inclusive B ? J/y X Lifetime at D0
D0 Run II Preliminary
First time at D0 Use the same technique of CDF
MC
D0 Result t 1.561?0.024?0.074 ps
D0 Run II Preliminary
PDG 2003 t 1.564?0.014 ps
9
b Hadrons Lifetime Measurement

• Exclusive lifetime with J/?

?? well measured
Simultaneous fitting of MB Extract signal
fraction ct Extract the lifetime
CDF Results
10
News about ?b
?b ? J/? ?

• Exclusive ?b lifetime
• (pre-blessed)
• Mass measurement
• (pre-blessed)

11
News about ?b contd
?b ? ?cl? ? pK? l?

• Semi-exclusive lifetime
• Branching ratio

Difficult to disentangle from decays through
excited baryons
And dE/dX
12

B Lifetime measurement semi-leptonic decays
Useful to optimize B mixing and flavor tagging
13
Flavor tagging

• Lepton (muon and electron) tagging under
  optimization in
• the huge sample of B ? lDX
• Same Side Tagging (SST) B0 (B0) accompanied by
  ?- (?)

B0 A(t) Dcos(?mt)
B A(t) cost
14

Bs Lifetime measurement semi-leptonic decays
Muons
Electrons
Signal to noise ratio better than expected !
Observed yield RunI?5
15
Lifetime and DG Perspectives

• CDF lifetime expectation in 2 fb-1 are
• Bs?J/?? and Bs?lDsX combined ? s(DG/G)?few
• for both CDF and D0
• CP asymmetry in Bs?J/?? expected small in S. M.
• If bigger ? new physics
• If Dms larger
• difficult to measure also with high statistics
  sample
• DG/G sizeable ? easy to measure
• Dms DGC where C can be calculated inside the
  S. M.

16
XsDms??Bs measurement semi-leptonic decays
Decays included Bs ? Ds?l, Ds?l (Ds?????,
K0K?, ?????) 40K events in 2 fb-1 Proper time
resolution ?t 60 fs ? t ? ?K/K ?K/K
14 Tagging ?D2 11.3 (all taggers)
CDF
Current limit Xsgt 20.6
Sensitive up to xs ? 30
17
D0 Bs mixing in fully hadronic decays
D0
Fully reconstructed decays
Decays included Bs? Ds???, Ds???????
(Ds?????, K0K?, K?K0) Bs?J/?K0 Proper time
resolution 0.40 ps Tagging ?D2 3.1 Jet
Charge ?D2 4.7 Lepton S/B 12
CDF sensitive up to xs ? 60 old (Y.B.)
prediction
18
Bs Yield Study the cuts applied

• Offline Trigger confirmation
• 3D Vertex for D and B vertices
• 1.013ltm(KK)lt1.028 GeV
• Ds Mass constraint
• DR(Ds-p)lt1.5
• cxyB lt 15 and cxyD lt 10
• PDsgt 4 GeV and PtBgt6 GeV
• LxyDgt400 mm
• LxyBgt100 mm
• dBlt100 mm

19
Bs Yield Study the signal
First observation !

• Can we measure the yield?
• fs/fd discrepancy LEP - CDF
• Branching Fraction unknown
• Cross section big uncertainty

20
Bs Yield Study the technique

Br(Bs?Ds-p) Br(Ds-???-) Br(??kk-)

Br(Bd?D-?) Br(D-?k?-?-)
PDG
Monte Carlo
Big effort in a full detector and trigger
simulation optimization a la LEP to measure
the efficiencies
21
Bs Yield Study Normalization mode

• Same mode for
• Similar cuts to signal
• also visible.

22
Bs Yield Study Systematic
Uncertainty in due to fit.
Uncertainty in
23
Bs Yield Study Result
24
Bs Yield Measurement where we are
Signal to noise optimization S/?B is optimized
with ?gt60

• Offline Trigger confirmation
• 3D Vertex for D and B vertices
• 1.010ltm(KK)lt1.028 GeV (only for Bs)
• D Mass constraint
• DR(D-p)lt1.5
• cxyB lt 15 and cxyD lt 10
• PDgt 3 GeV (3.5 for Bs) and PtBgt6 GeV (5.5 for
  Bs)
• LxyDgt-150 mm
• LxyBgt250 mm (400 for Bs)
• dBlt80 mm
• Pt(?B)gt1.6 (1.9 for Bs)

25
Bs Yield Measurement where we are
Signal to noise optimization
26
?b? ?c? Relative Yield Measurement
Same technique used for Bs

• Confirm trigger cuts
• Pt(proton)gt2 GeV
• Pt(? from ?b)gt2 GeV
• Pt(?c)gt4.5 GeV
• Pt(?b)gt7.5 GeV
• c?(?b)gt 225 ?m
• c?(?cfrom ?b)gt -65 ?m
• d0(?b)lt85 ?m
• Pt(proton)gtPt(? from ?c)
• 2.269ltm(?c)lt2.302 GeV
• ?xy(?b)lt30
• ?xy(?c)lt20

27
?b? ?c? Relative Yield Measurement
28
The Normalization Channel
B0?D-? same cuts optimized for ?b are applied
29
?b? ?c? Relative Yield Measurement
30
?b? ?c? Relative Yield Measurement
31
Many other B decays
32
CP violation in Standard Model g at CDF

• R. Aleksan et al. Z Phys. C54 653 (1992)
  proposal
• Bs?Ds?K? time dependent decay rate depends
  on
• sin(d?g) and cos(d?g)
• Theoretically clean
• Reasonable Branching ratio
• Background Bs?Dsp
• Need tagging
• Need time dependent analysis

1000 events in RunIIa 3500 events in
RunIIb
33
J/? cross section
Pt?gt1.5 ?Pt(J/?)?0 First time at Tevatron
34
CP Asymmetries and Decays Ratios of D0?hh-
Two Tracks Trigger open CDF to a new field, charm
physics

• Pure D0 samples are required ? D tag used
• The charge of the slow pion gives the D0 flavor

35
CP Asymmetries and Decays Ratios of D0?hh-
36
CP Asymmetries and Decays Ratios of D0?hh-
9.38 0.18 (stat) 0.10 (syst)
3.686 0.076 (stat) 0.036 (syst)
Results competitive with dedicated experiments
and ee- machines i.e. CLEO FOCUS
ACP
ACP(??) 2.0 1.7 (stat) 0.6 (syst)
ACP(KK) 3.0 1.9 (stat) 0.6 (syst)
37
Summary

• CDF is starting doing competitive B physics
  measurements
• D0 need more time since the new detector
• In Italy many activities
• Bs branching ratio
• analysis
• D0 branching ratio
• CP measurements
• No contribution on
• J/? analysis
• Many opportunities
• for students !