B Physics at CDF

Shin-Hong Kim(University of Tsukuba)
October 9 , 2003
ICFP2003 at KIAS, SeoulTevatron pp Collider at Fermilab
RunI (1992〜1996)√s = 1.8 TeV

CDF
Tevatron Ring

Main Injector

RunII（2001〜）√s = 1.96 TeV+ Main Injector

Tevatron Status
2002

2001

Run I（1992〜1996）:

Initial Luminosity• Record Luminosity
2x1031 cm-2sec-1• Integrated Luminosity
110 pb-1 on Tape

Now

Run II（2001〜）:• 5 x1031 cm-2sec-1 （August 2003）• Integrated Luminosity 330 pb-1
– 270 pb-1 on Tape
– 120 pb-1 analyzed

2001

2002

330 pb-1Integrated Luminosity
Delivered
270 pb-1

Schedule:• 2 fb-1 (by the end of 2005)• 9 fb-1 (by the end of 2009)

On tapeMuon SystemCDF

Drift Chamber

Central Calor.
NewSolenoid

Old
PartiallyNew

Time-of-Flight

Plug Calor.

Muon

Front End Electronics
Triggers / DAQ (pipeline)
Online & Offline Software

Silicon Microstrip
Tracker

Silicon Vertex Trigger (SVT)•SVT incorporates silicon info in theLevel 2 trigger… select events withlarge impact parameter!

SecondaryVertex

LxyPrimaryVertex

BPT(B) ≥ 5 GeV<Lxy> 〜450µm

d = impact parameter•••

35µm ⊕ 33µmresol ⊕ beam
⇒ σ = 48µm

Uses fitted beamline
impact parameter per track
System is deadtimeless:– ~ 25 µsec/event for readout +clustering + track fitting-500-250
0250500
SVT impact parameter (µm)

B Physics at Hadron Colliders
b’s produced by strong interaction, decay by weak interaction

Advantage• Enormous cross-section– ~100 µb total– ~ 4 µb “reconstructable”– At 4x1031cm-2s-1 ⇒ ~150Hz ofreconstructable BB!!
• All B hadrons produced– Bu,Bd,Bs,Bc,Λb,…
Disadvantage• Large inelastic background– Triggering and reconstruction are challenging

Heavy Flavor Cross Sections (RunI)• Tevatron B cross sections measured at √s =1.8TeV(Run I: 1992-1996) consistently higher than NLO calculation
Integrated cross sections• Theoretical work is ongoing– Fragmentation effects– Small x, threshold effects– Proposed beyond SM effects• What can experiments do?
– Measure more cross sectionsXX• √s =1.96 TeV• go to lower pT(B)– Look at bb correlations– Measure the charm crosssection

Observation of Bc meson (RunI)
Invariant mass of J/ψ＋lin Bc→ J/ψlν decay modeN（Bc）＝ 20.4＋6.2ー5.6

Cross section times Branching ratio
vs Lifetimeτ ( B c ) = 0.46 ± 0.18 ps+ 0.061
σ ( p p → B c X)BR( B c → J / ψlν )= 0.132- 0.052σ ( p p → Bu X)BR( Bu → J / ψK )

Anomalous J/ψDirect Production (RunI)●Cross section of J/ψ andψ(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/ψ andψ(2s) disfavors the color octet model.J/ψ production cross section ( RunⅡ)
CDF measured theJ/ψ cross section fromPT > 0GeV/c by lowering
the trigger threshold.
Consistent with Run I
Measurement in PT >5GeV/c region.
Need a comparison
between this result andtheoretical prediction in
the PT < 5GeV/c region.

B Hadron Lifetimes• All lifetimes equal in spectator model. Heavy Flavor Averaging GroupzDifferences from interference & othernonspectator effects

http://www.slac.stanford.edu/xorg/hfag/index.html• Heavy Quark Expansion predicts thelifetimes for different B hadronspeciesτ ( B + ) ≥ τ ( B 0 ) ≈ τ ( BS ) > τ (Λ b ) ≫ τ ( Bc )• Measurements:
zB0,B+ lifetimes measured to better than 1%!
zBs known to about 4%
zLEP/CDF (Run I) Λb lifetime lower thanHQE prediction• Tevatron can contribute to Bs, Bc andΛb (and other b-baryon) lifetimes.

B hadron

Average lifetime (ps)

B0B+BsBc

1.534±0.013
1.653±0.014
1.439±0.053
0.46 +−0.18
0.16

Λb1.233 +−0.078
0.076

B+, B0 Lifetimes in J/ψ Modes
τ(B0) 1.63 ± 0.05(stat.) ± 0.04 (syst.) ps
τ(B+) 1.51 ± 0.06(stat.) ± 0.02 (syst.) ps zTrigger on low pTdimuons (1.5-2GeV/µ)zFully reconstruct
9 J/ψ, ψ(2s)→µ+µ−
9 B+→ J/ψK+
9 B0 → J/ψK*, J/ψKs
9 Bs → J/ψφ
9 Λb→ J/ψΛProper decay length:
Lxy LxymB
ct = =βγpT

Bs Lifetime
Bs→J/ψ Φ with J/ψ→μ+μ- and Φ→K+KB+→ J/ΨK+, B0 →J/ΨK*0 check technique, systematicsmB
ct = Lxy B
pTcandidates per 50 µ m

Bs lifetime - PDG 1.461 ± 0.057 ps
1.33 ± 0.14(stat) ± 0.02(sys) ps
103L ≈ 138 pb

CDF Run II Preliminary

Bs → J/ ψ φdatact (Sig)
102ct (BkgS)

ct (BkgL)

Fit prob: 19.7%

101-0.1

0.0

0.1

0.2

0.3

ct, cm-1

Λb Lifetime• Use fully reconstructed Λb →J/ψΛ with J/ψ→ µ+µ− and Λ→ pπ−– Previous LEP/CDF measurements used semileptonic Λb → Λclν
• Systematics different
primaryLxyµ−π−p+µ46±9 signalτ ( Λb ) =1.25± 0.26( stat.) ± 0.10( syst.) psFirst lifetime from fullyreconstructed Λb decay!

B Hadron Masses• Measure masses using fullyreconstructed B→J/ψX modes• High statistics J/ψ→µ+µ− andψ(2s)→J/ψπ+π− for calibration.
• Systematic uncertainty fromtracking momentum scale– Magnetic field– Material (energy loss)• B+ and B0 consistent withworld average.
• Bs and Λb measurements areworld’s best.
CDF result:M(Bs)=5365.5 ±1.6 MeVWorld average: M(Bs)=5369.60 ±2.40 MeV
CDF result:M(Λb)=5620.4 ±2.0 MeV
World average: M(Λb)=5624.4 ±9.0 MeV

New Particle decaying to J/ψπ+π−
Belle observes narror state
final state J/ψπ+π−• exclusive: B+ →J/ψπ+π− K+• 35.7 ±6.8 events• possibly charmonium• mass is unexpected• shown August 12, 2003

CDF confirms this September 20• final state J/ψπ+π−• mostly prompt prodction• 709±86 events

B→h+h−αγtreeβV•ub• charmless two-body decays– longer term Bs modes help extract unitarity
angle γpenguin• Signal is a combination of:– B0→π+π− BR~5x10-6– B0→K+π− BR~2x10-5– Bs→K+K− BR~5x10-5– Bs→π+K− BR~1x10-5} Υ(4s),Tevatron} Tevatron

280±26 eventsµ = 5.252(4) GeV/c2
σ = 41.0(4.0) MeVc2• Requirements– Displaced track trigger– Good mass resolution– Particle ID (dE/dx)

π+π− hypothesisM(ππ)

BR(Bs→K+K−)
Simulation
Bd→Kπ
Bs→KK
Bd→π π
Bs→K π320±60 eventsµ = 5.252(2) GeV/c2
σ = 41.1(1.9) MeV/c2M(ππ)

Fitted contributions:
mode

Yield (65 pb-1)

B0→Kπ

148±17(stat.)±17(syst)

B0→ππ
Bs→KK

39±14(stat.)±17(syst)
90±17(stat.) ±17(syst)

Bs→Kπ

3±11(stat.) ±17(syst)

kinematics & dE/dx to separate contributions

CDF RunII Preliminary

D*ÆD0π,Sep.~1.3σ

D0ÆKπFirst observation of Bs→K+K− !!
Result:f s BR( Bs → KK )f d BR ( B → Kπ )Measure ACP(dE/dx – dE/dx(π))/σ(dE/dx)

0= 0.74 ± 0.20 ± 0.22

N ( B → K −π + ) − N ( B → K +π − )= 0.02 ± 0.15 ± 0.02−++−N ( B→K π )+ N ( B→K π )Λb→Λcπ with Λc→pKπ
Backgrounds: real B decays
Reconstruct π as p: Bd → D−π+→K+π−π−π+¾ Use MC to parametrize the shape.
¾ Data to normalize the amplitude¾ Dominant backgrounds are real heavyflavor¾ proton particle ID (dE/dx) improves
S/B

Fitted signal:

N Λb = 96 ± 13( stat.) −+67 ( syst.)

Measure:σ b × fbaryon × BR(Λ b → Λ + c π − )σ b × f d × BR( B 0 → D − π + )New Result !
BR(Λb Æ Λc π±) = (6.0 ±1.0(stat) ± 0.8(sys) ± 2.1(BR) ) x 10-3

Bs Yields: CDF Bs→Dsπ+

Bs→Dsπ− with

Ds →φπ+ and φ→K−K+BR(Bs Æ Ds π±) = ( 4.8 ± 1.2 ± 1.8 ± 0.8 ± 0.6) ×10-3
New measurement !

(Stat) (BR) (sys) (fs/fd)

Previous limit set by OPAL: BR (Bs Æ Ds π± ) < 13%

BR result uses less data
than shown in plot.

Measuring Bs Oscillation• Bs reconstruction− +– e.g. Bs → Ds π
• Flavor tagging ( Bs or Bs at the time of production?)– Tagging “dilution”: D=1-2w
Typical power (one tag):– Tagging power proportional to: εD2 εD2 = O(1%) at Tevatron
εD2 = O(10%) at PEPII/KEKB• Proper decay time

ct =Lxy( βγ )=Lxy mB

uncertainty

pT– Crucial for fast oscillations (i.e. Bs)⎛ σ pT ⎞mB
σ ct =σ Lxy ⊕ ct ⎜⎟pT
⎝ pT ⎠

Flavor Tagging• Strategy: use data for calibration(e.g. B±→J/ψK±, B→lepton)– “know” the answer, can measureright sign and wrong sign tags.

Results:zSame-side (B+) εD2=(2.1±0.7)%(B+/B0/Bs correlations different)
zMuon tagging
εD2=(0.7±0.1)%“same-side” tagging

CDF Bs Sensitivity Estimate••••Current performance:
hadronic mode only
– S=1600 events/fb-1 (i.e. σeffective for produce+trigger+recon)– S/B = 2/1– εD2 = 4%
– σt = 67fs
2σ sensitivity for ∆ms =15ps-1 with ~0.5fb-1 of data
surpass the current world averageWith “modest” improvements– S=2000 fb (improve trigger, reconstruct more modes)– S/B = 2/1 (unchanged)– εD2 = 5% (kaon tagging)– σt = 50fs (event-by-event vertex + L00)
5σ sensitivity for ∆ms =18ps-1 with ~1.7fb-1 of data
5σ sensitivity for ∆ms =24ps-1 with ~3.2fb-1 of data
∆ms=24ps-1 “covers” the expected region based upon indirect fits.
This is a difficult measurement.
There are ways to further improve this sensitivity…

RunII Projected Integrated Luminosity
Middle of 2007
∆ms =24ps-1(5σ)
Now

End of 2005
∆ms =18ps-1(5σ)

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

BACKUP SLIDESTOF counter• TOF time resolution〜100ps(design value)• Φ meson → K+ KS/N: 0.025 → 0.45

S/N = 1942/4517
S/N = 2354/93113

TOF

Material & Momentum Calibration• Use J/ψ’s to understand E-loss
and B-field corrections
σ(scale)/scale ~ 0.02% !

D0• Check with other known signals
Add B scale correction
Tune missing material ~20%
Correct for materialin GEANT

confirmwithγ→ee

Υ
1S2S

Raw tracks

3SµµJ/ψproduction in RunⅡaPossible interpretations•A ψ(13D2) state:– Because D-states have negativeparity, spin-2 states cannot
decay to DD– They are narrow as long as
below the DD* threshold– η2(11D2) preferentially decays
to hc(11P1). Decays to π+π− J/ψ
would be of magnetic type andare suppressed.
– Some models predict large
widths for ψ(13D2) → π+π− J/ψ
– All models predict even larger
widths for ψ(13D2) → γ χc(13P2,1) Should easily seeψ(13D2) → γγ J/ψ.
• Discovery of the signal isvery recent. Belle is working
on this channel but is notready to present any results.

ψ(13D3)
η2(11D2) ψ(13D2)γ14%ψ(13D1)

γ 65%
γ

DD

γ γ
γ

32%
20%

7%

π +π −

Based on:
E.J.Eichten, K.Lane
C.Quigg
PRL 89,162002(2002)

J/ψBR (ψ (13 D2 ) → γγ J /ψ )~3BR(ψ (13 D2 ) → π +π − J /ψ )

Ds, D+ mass difference• Ds± - D± mass difference– Both D Æ φπ (φÆKK)∆m=99.28±0.43±0.27
MeV• PDG: 99.2±0.5 MeV(CLEO2, E691)– Systematics dominated bybackground modeling
Brand new CDF
capability

11.6 pb-1~1400
events~2400
eventsBd Mixingd• t •W−B0b

B0W+• t •Vtb~1bdRe(Vtd)≈0.0071

Bd mixing measured with greatprecision– World average now
dominated by Babar andBelle

Bd fully mixes in about 4.1 lifetimes

α ∆ms/∆mdγ•••

Towards Bs Mixing

βMeasurement of ∆ms helps improve
our knowledge of CKM triangle.
Combined world limit on Bs mixing– ∆ms>14.4ps-1 @95%CL– Bs fully mixes in <0.15 lifetime!!!
Bs oscillation much faster than Bd
because of coupling to top quark:
Re(Vts)≈0.040 > Re(Vtd)≈0.007s• t •
W−B0b

B0W+

• t •

Vtb~1bs

Re(Vts)≈0.04

Combined limit comes from 13
measurements from LEP, SLD& CDF Run I

Semileptonic Bs Yields

Plots show: Bs→Dsl−νwith Ds →φπ+ and φ→K−K+(will also reconstruct Ds →K*0K+ and Ds →KsK+)RunII

Luminosity

RunII

WeeklyLuminosity

RunIIPhysics
Program