B Physics at CDF

1
B Physics at CDF
Shin-Hong Kim (University of Tsukuba) October
9 , 2003 ICFP2003 at KIAS, Seoul
2
Tevatron pp Collider at Fermilab
RunI (19921996) s 1.8 TeV RunII(2001)
s 1.96 TeV Main Injector
v
CDF
Tevatron Ring
v
Main Injector
3
Tevatron Status
2002
2001

• Run I(19921996)
• Record Luminosity
• 2x1031 cm-2sec-1
• Integrated Luminosity
• 110 pb-1 on Tape
• Run II(2001)
• 5 x1031 cm-2sec-1 (August 2003)
• Integrated Luminosity 330 pb-1
• 270 pb-1 on Tape
• 120 pb-1 analyzed
• Schedule
• 2 fb-1 (by the end of 2005)
• 9 fb-1 (by the end of 2009)

Initial Luminosity
Now
2001
2002
330 pb-1
Integrated Luminosity
Delivered
270 pb-1
On tape
4
Drift Chamber
Muon System
Central Calor.
New
Solenoid
Old
Partially New
Time-of-Flight
Plug Calor.
Muon
Silicon Microstrip Tracker
Front End Electronics Triggers / DAQ
(pipeline) Online Offline Software
5
Silicon Vertex Trigger (SVT)

• SVT incorporates silicon info in the Level 2
  trigger select events with large impact
  parameter!
• Uses fitted beamline
• impact parameter per track
• System is deadtimeless
• 25 ?sec/event for readout clustering track
  fitting

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B Physics at Hadron Colliders
bs produced by strong interaction, decay by weak
interaction

• Advantage
• Enormous cross-section
• 100 ?b total
• 4 ?b reconstructable
• At 4x1031cm-2s-1 ? 150Hz of reconstructable BB!!
• All B hadrons produced
• Bu,Bd,Bs,Bc,?b,

• Disadvantage
• Large inelastic background
• Triggering and reconstruction are challenging

7
Heavy Flavor Cross Sections (RunI)

• Tevatron B cross sections measured at vs 1.8TeV
• (Run I 1992-1996) consistently higher than NLO
  calculation

• Theoretical work is ongoing
• Fragmentation effects
• Small x, threshold effects
• Proposed beyond SM effects
• What can experiments do?
• Measure more cross sections
• vs 1.96 TeV
• go to lower pT(B)
• Look at bb correlations
• Measure the charm cross section

Integrated cross sections
X
X
8
Observation of Bc meson (RunI)
Cross section times Branching ratio vs Lifetime
Invariant mass of J/?l in Bc? J/?l? decay mode
N(Bc) 20.46.2?5.6
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Anomalous J/?Direct Production (RunI)
?Cross section of J/? and?(2s) direct production
is larger than QCD theoretical prediction by a
factor of 50. PRL 79 (1997) 572, PRL 79
(1997) 578 ? Polarization of J/? and?(2s)
disfavors the color octet model.
10
J/? production cross section ( Run?)
CDF measured the J/? cross section from PT gt
0GeV/c by lowering the trigger threshold. Consist
ent with Run I Measurement in PT gt 5GeV/c
region. Need a comparison between this result
and theoretical prediction in the PT lt 5GeV/c
region.
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B Hadron Lifetimes

• All lifetimes equal in spectator model.
• Differences from interference other
  nonspectator effects
• Heavy Quark Expansion predicts the lifetimes for
  different B hadron species
• Measurements
• B0,B lifetimes measured to better than 1!
• Bs known to about 4
• LEP/CDF (Run I) ?b lifetime lower than HQE
  prediction
• Tevatron can contribute to Bs, Bc and ?b (and
  other b-baryon) lifetimes.

Heavy Flavor Averaging Group http//www.slac.stanf
ord.edu/xorg/hfag/index.html
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B, B0 Lifetimes in J/? Modes
?(B0)
1.63 ? 0.05(stat.) ? 0.04 (syst.) ps
?(B)

• Trigger on low pT dimuons (1.5-2GeV/?)
• Fully reconstruct
• J/?, ?(2s)????
• B? J/?K
• B0 ? J/?K, J/?Ks
• Bs ? J/??
• ?b? J/??

• 1.51 ? 0.06(stat.) ? 0.02 (syst.) ps

Proper decay length
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Bs Lifetime
Bs?J/? F with J/??µµ- and F?KK- B? J/?K, B0
?J/?K0 check technique, systematics

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?b Lifetime

• Use fully reconstructed ?b ?J/?? with J/??
  ??? and ?? p??
• Previous LEP/CDF measurements used semileptonic
  ?b ? ?cl?
• Systematics different

46?9 signal

First lifetime from fully reconstructed ?b decay!
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B Hadron Masses

• Measure masses using fully reconstructed B?J/?X
  modes
• High statistics J/????? and ?(2s)?J/???? for
  calibration.
• Systematic uncertainty from tracking momentum
  scale
• Magnetic field
• Material (energy loss)
• B and B0 consistent with
• world average.
• Bs and ?b measurements are worlds best.

16
New Particle decaying to J/?pp?

• Belle observes narror state
• final state J/?pp?
• exclusive B ?J/?pp? K
• 35.7 6.8 events
• possibly charmonium
• mass is unexpected
• shown August 12, 2003

• CDF confirms this September 20
• final state J/?pp?
• mostly prompt prodction
• 70986 events

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B?hh?

• charmless two-body decays
• longer term Bs modes help extract unitarity angle
  ?
• Signal is a combination of
• B0???? BR5x10-6
• B0?K?? BR2x10-5
• Bs?KK? BR5x10-5
• Bs??K? BR1x10-5
• Requirements
• Displaced track trigger
• Good mass resolution
• Particle ID (dE/dx)

?(4s),Tevatron

Tevatron
??? hypothesis
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BR(Bs?KK?)
Fitted contributions
First observation of Bs?KK? !! Result Measure
ACP
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?b??c? with ?c?pK?

• Backgrounds real B decays
• Reconstruct p as p Bd ? D?p?Kp?p?p
• Use MC to parametrize the shape.
• Data to normalize the amplitude
• Dominant backgrounds are real heavy flavor
• proton particle ID (dE/dx) improves S/B

Fitted signal
New Result !
BR(Lb ? Lc p?) (6.0 ?1.0(stat) ? 0.8(sys) ?
2.1(BR) ) x 10-3
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Bs Yields CDF Bs?Ds?
Bs?Ds?? with Ds ??? and ??K?K
BR(Bs ? Ds p?) ( 4.8?? 1.2?? 1.8?? 0.8?? 0.6)
?10-3
(Stat) (BR) (sys) (fs/fd)
New measurement ! Previous limit set by OPAL BR
(Bs ? Ds p? ) lt 13
BR result uses less data than shown in plot.
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Measuring Bs Oscillation

• Bs reconstruction
• e.g.
• Flavor tagging ( Bs or Bs at the time of
  production?)
• Tagging dilution D1-2w
• Tagging power proportional to ?D2
• Proper decay time
• Crucial for fast oscillations (i.e. Bs)

Typical power (one tag) ?D2 O(1) at
Tevatron ?D2 O(10) at PEPII/KEKB
uncertainty
22
Flavor Tagging

• Strategy use data for calibration (e.g.
  B??J/?K?, B?lepton)
• know the answer, can measure right sign and
  wrong sign tags.

• Results
• Same-side (B) ?D2(2.1?0.7)
• (B/B0/Bs correlations different)
• Muon tagging ?D2(0.7?0.1)

same-side tagging
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CDF Bs Sensitivity Estimate
hadronic mode only

• Current performance
• S1600 events/fb-1 (i.e. ?effective for
  producetriggerrecon)
• S/B 2/1
• ?D2 4
• ?t 67fs
• surpass the current world average
• With modest improvements
• S2000 fb (improve trigger, reconstruct more
  modes)
• S/B 2/1 (unchanged)
• ?D2 5 (kaon tagging)
• ?t 50fs (event-by-event vertex L00)
• ?ms24ps-1 covers the expected region
  based upon indirect fits.
• This is a difficult measurement.
• There are ways to further improve this
  sensitivity

2? sensitivity for ?ms 15ps-1 with 0.5fb-1 of
data
5? sensitivity for ?ms 18ps-1 with 1.7fb-1 of
data 5? sensitivity for ?ms 24ps-1 with 3.2fb-1
of data
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RunII Projected Integrated Luminosity
Middle of 2007 ?ms 24ps-1 (5s)
End of 2005 ?ms 18ps-1 (5s)
Now
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Conclusion

• New results of masses, lifetimes and branching
  ratio
• on B physics produced at CDF, especially on
• heavier B-hadrons.
• New measurements on heavier B-hadrons, such as
• Bs oscillation, Bc mass and ?b branching
  ratio will
• come in the near future.

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BACKUP SLIDES
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TOF counter

• TOF time resolution
• 100ps(design value)
• F meson ? K K-
• S/N 0.025 ? 0.45

S/N 1942/4517
TOF
S/N 2354/93113
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Material Momentum Calibration

• Use J/ys to understand E-loss and B-field
  corrections
• s(scale)/scale 0.02 !
• Check with other known signals

D0
confirm with g?ee
U
1S
2S
3S
mm
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J/?production in Run?a
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Possible interpretations

• A y(13D2) state
• Because D-states have negative parity, spin-2
  states cannot decay to DD
• They are narrow as long as below the DD
  threshold
• h2(11D2) preferentially decays to hc(11P1).
  Decays to pp- J/y would be of magnetic type and
  are suppressed.
• Some models predict large widths for y(13D2) ?
  pp- J/y
• All models predict even larger widths for y(13D2)
  ? g cc (13P2,1) Should easily see
  y(13D2) ? gg J/y.
• Discovery of the signal is very recent. Belle is
  working on this channel but is not ready to
  present any results.

y(13D3)
y(13D2)
h2(11D2)
y(13D1)
14
g
g
65
g
g
g
7
32
pp-
g
20
Based on E.J.Eichten, K.Lane C.Quigg PRL
89,162002(2002)
J/y
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Ds, D mass difference
11.6 pb-1

• Ds - D mass difference
• Both D ? fp (f?KK)
• Dm99.280.430.27 MeV
• PDG 99.20.5 MeV
• (CLEO2, E691)
• Systematics dominated by background modeling

2400 events
1400 events
Brand new CDF capability
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Bd Mixing

• Bd mixing measured with great precision
• World average now dominated by Babar and Belle

Bd fully mixes in about 4.1 lifetimes
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Towards Bs Mixing

• Measurement of ?ms helps improve our knowledge of
  CKM triangle.
• Combined world limit on Bs mixing
• ?msgt14.4ps-1 _at_95CL
• Bs fully mixes in lt0.15 lifetime!!!
• Bs oscillation much faster than Bd because of
  coupling to top quark
• Re(Vts)?0.040 gt Re(Vtd)?0.007

Combined limit comes from 13 measurements from
LEP, SLD CDF Run I
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Semileptonic Bs Yields
Plots show Bs?Dsl?? with Ds ??? and
??K?K (will also reconstruct Ds ?K0K and Ds
?KsK)
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RunII Luminosity
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RunII Weekly Luminosity
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RunIIPhysicsProgram