June 28, 2002BEACH2002 B Physics at the Tevatron B Physics at the Tevatron Jack Cranshaw Texas Tech University For the CDF and D0 Collaborations

June 28, 2002 BEACH2002 B Physics at the Tevatron

B Physics at the Tevatron

Jack Cranshaw

Texas Tech UniversityFor the CDF and D0

Collaborations


Tevatron

• Proton-antiproton collider with center of mass energy of 1.96 TeV.


Why Do B Physics at the Tevatron?

• Large Cross Section!

• Produce bottom mesons with all flavor combinations as well as bottom baryons.– Bc, b, b, ...

• Multipurpose detectors CDF and D0 capable of reconstructing many B final states.

• Experience with a 110 pb-1 of Run I data (1992-1996)

)kHz! 15(~ TeV 2at 150)( bbbpp 0Zat 7)( nbbbee (4S)at 1)( nbBBee


This Allows Measurements of

• Mixing in the Bd and Bs systems.

• CP violation in the Bd and Bs systems.

• Search for rare decays.

• Properties of the Bc meson.

• Lifetimes

• Branching Ratios

• Cross sections


CP Violation in the B System

13

(1,0)

Vtb*Vtd Vcb

*Vcd Vub* Vud 0

Mixing between weak eigenstates and mass eigenstates described by the CKM matrix.

Vud Vus Vub

Vcd Vcs Vcb

Vtd Vts Vtb

Use orthogonality of unitary matrix columns to define unitary triangle, e.g.

Measure all of the angles• determines level of CP violation• if ≠ 180o then evidence for non-SM CP violation


Types of CP Violation

1. Mixing (F=2 or indirect CP violation)• Is there a relative phase between the mass

mixing and the decay widths?

2. Decay (F=1 or direct CP violation)• Is there an asymmetry in the amplitudes <B|

f> and <B|f> where f is a CP eigenstate?

3. Interference between Decay and Mixing


CP violation in B Meson Mixing

• Measure sin(2q) using

– Measure oscillations between B-Bbar– Since |Vts| >> |Vtd| the oscillations are much faster in the Bs system

relative to the Bd system need good vertex resolution.

– Precise measurement of md/ms

Mixing depends on CKM t quark dominates:

b

q

q

b

q

q b

b

W+

W-

W-W+ uq uq

uq

uq

2*tqtbq VVm

)sin()2sin()()(

)()()( tm

tNtN

tNtNtA qq

q=d, squ=u,c,t


Run I sin(2) Measurement

• CDF Published Result sin(2)=0.79±0.39±0.16• CDF Result (2001) sin(2)=0.91±0.32±0.18

Measured using decay channels BdJ/Ks

0, BdSKs

0.• Babar sin(2)=0.75±0.09±0.04• Belle sin(2)=0.82±0.12±0.05

Run I silicon vertexing sufficient for measurement of sin(2) in Bd mixing


Bs Mixing

• Reconstruct Bs decays using fully hadronic and semileptonic decay channels.

• Measure xs=ms/

• With 2 fb-1 should cover full range of theoretically predicted values for xs.

• Afterwards, we can search for CP violation in the Bs

system (Bs JLarge window for non-SM physics.


Unitarity Angles ,

• Measure/limit based on Bd , Bs

Ds

• Measure using combination of

– Bd

– Bs

• Challenges

– Separation of Bd,s

– Understanding penguin contributions (using both decays helps)

– In addition there are interference amplitudes due to mixing.

• However ample statistics for precision observation of asymmetry.

Dominant Subdominant

bd

u

sb b

bW-

W-

W-

W- s

u

d

u

u

Decays related by d,s interchange

Fleischer PLB 459 (1999) 306


Meson/Baryon Spectroscopy

• Spectroscopy of B mesons with second generation quarks, and B baryons currently available only at hadron colliders.

Mass Measurements:• m(Bs) = 5.3699 ± 0.0023 ± 0.0013 GeV/c2 • m(b) = 5.621 ± 0.004 ± 0.003 GeV/c2

• m(Bc) = 6.40 ± 0.39 ± 0.13 GeV/c2

Run I Measurements


b and Bc

bJ/

bJ/bpD0, D0K-

bpK-

Run IIBcJ/e/BcJ/BcBs

Run IRun I


Cross Sections and Branching Ratios

• During Run I we measured b inclusive cross sections.

• These were systematically above the NLO predictions (by factor ~2.5).

• Many measurements of cross sections and branching ratios were calculated with respect to a reference signal to avoid uncertainties on trigger efficiencies and measured luminosity.

• In this sense, the ‘B factories’ provide us with valuable ‘calibrations’ for our reference signals.


Experimental Challenges

• High resolution tracking and vertexing for reconstructing decays and lifetimes.

• The ability to trigger on displaced vertices.• Particle identification for flavor tagging.• Excellent muon reconstruction.• Good EM calorimetry for rare decay searches and

radiative decays. • Well understood simulation of detector and

physics.• Efficient use of trigger bandwidth budget.


Charm Production

• As we lower our pT thresholds we see a lot of charm. (~106 reconstructed events per pb-1!)

• This will lead to a world class charm program.


Accelerator Upgrades

• Replace Main Ring with Main Injector

• Upgrade Pbar storage

• Tevatron upgrade:– major luminosity increase

• 1031 5 x 1031 2 x 1032

110pb-1 2fb-1 15fb-1

– Short interbunch to limit Nint/crossing

• 3.5 s 396 ns 132 ns1030 1031 1032 1033

0.1

1.0

10.

100.

AverageNumber ofInteractions

per crossing

Luminosity

6 Bunch

es

36 bunch

es

108 b

unches

Run I Run IIa Run IIb


Status of Integrated Luminosity

• Just finished shutdown.

• Top Run II luminosity so far 2 X 1031 cm-2 s-1

• Currently the major hurdle for producing Run II physics.

• Approximately 30 pb-1 on tape with a variety of triggers and detector conditions.


CDF Run II Detector

MuonsCalorimetersTracking

TrackingSilicon Vertex Detector

-L00

Intermediate SiliconCentral Outer Tracker

Endplug Calorimeter Muon systems

TOF


D0 Run II Detector

Build on existing strengths• Excellent calorimetry

with faster readout• Upgraded muon system

for better -IDAdd new capabilities• Inner tracking (silicon

tracker, fiber tracker) with 2T superconducting solenoid

• Preshowers• Pipelined 3-level

trigger• Si Track Trigger

(displaced vertices)


Physics Program, First Stages

• Stage 1 (50 pb-1)– Refine triggers– Lifetime measurements– Cross sections, branching ratios

• Stage 2 (50-200 pb-1)– First Bs mixing measurement– Run II sin(2) measurement– Charmonium polarization

• Stage 3 (200+ pb-1)– Bs, Bc, b properties measurements– Cross sections, branching ratios– …


Conclusion

• Exciting physics opportunities at the Tevatron for Run II

• Developing new measurements/ techniques

• More about status and prospects in Stephen and Rick’s talks.


Run II Improvements

• Silicon detectors (SVXII, ISL):– Double SVX length for full acceptance (SVX II)

– Double sided silicon for 3-D track reconstruction (SVXII)

– More silicon layers & forward silicon (ISL) for standalone tracking

– Secondary vertex trigger at LV2 (20 ms) (SVT)

• Central tracker (COT):– Double the number of stereo layers (COT)

– x 6 more sense wires improves occupancy (COT)

• Muon system:– Improved coverage: old “holes” fixed and push to || = 1.5 (IMU)

• New Plug calorimeter– Add preshower and shower max detector


Why Do B Physics?

• Heaviest quark that can currently be produced in large samples.

• CP Violation: Gives access to the unitarity triangle with the simplest interpretation.

• Spectroscopy of B mesons.

• Heavy quark – light quark pairings more easily understood theoretically.


Jet Tagging Algorithms

To measure mixing, must tag the initial flavor of produced B meson.

– Away Side Tags (tag the other b quark) 1. Lepton tagging: b Xlb Xl

2. Kaon tagging: b c XKb c XK

3. Jet charge tagging: form pT weighted jet charge, b Qjet<0, b Qjet>0

4. Vertex Charge tagging

– Same Side Tags1. Soft pion tag: b associated with collinear -,

b associated with collinear +


CDF Run II Trigger System

Front-end electronicsLevel1 Trigger

• synchronous, 132 ns• 42 deep pipeline gives 5.5 ms for L1 decision• Accept rate 40-50 kHz

Level2 Trigger• asynchronous• Accept rate 300 Hz

Level3 Trigger (not shown)• Farm of 175 PC’s• Accept rate 75 Hz

Control Infrastructure

Documents

June 28, 2002BEACH2002 B Physics at the Tevatron B Physics at the Tevatron Jack Cranshaw Texas Tech University For the CDF and D0 Collaborations