DØ Beauty Physics in Run II Rick Jesik Imperial College BEACH 2002 V International Conference on Hyperons, Charm and Beauty Hadrons Vancouver, BC, June BEACH 2002 V International Conference on Hyperons, Charm and Beauty Hadrons Vancouver, BC, June  + +  - - + Q > 0.2  - - b b

B S mixing semileptonic decays Spectroscopy and lifetimes B 0, B +, B s, B c,  b Rare decays DØ Run II B Physics Goals QCD tests cross sections bb correlations charmonium polarization CP violation sin(2  non SM

The first year of Run II Luminosity 38 pb -1 delivered 26 pb -1 utilized 12 pb -1 physics Fiber Tracker fully instrumented New data is processed within a week 84 million events reconstructed so far New data is processed within a week 84 million events reconstructed so far

The DØ Silicon Detector 6 barrel, 16 disk, hybrid design 4 layer barrels good position resolution: 10  m tracking out to |  | = 3 inner most layer at r = 2.6 cm 793 k channels Rad hard up to 1 Mrad

The DØ Silicon Detector

Silicon Detector Performance pulse height correlation between n- and p-sides Full coverage - all detectors installed 95% of the channels are operational p-side pulse height ( ADC )

Silicon Tracker Performance The Silicon Tracker is performing very well. Precision alignment is underway. The Silicon Tracker is performing very well. Precision alignment is underway.

The DØ Fiber Tracker 8 cylinders with 4 layers of 830  m scintillating fibers each Radial and alternating (2 o ) stereo doublets Fast response, good resolution, low mass

u ~ 10 photons will get to VLPCs u Operate at 9 Kelvin u Work in a high rate environment u Quantum efficiency ~80% u High gain 17k to 65k electrons per converted photon Visible Light Photon Counters ped 1 photon 2 photons

Inner Tracker Performance

Primary Vertex Finding num tracks in vtx

DØ Muon System

A-  Counters : 630 scintillators (  x  0.2 x 4.5  matches central tracker trigger sectors facilitates low p T muon ID and triggers pT > 1.5 GeV/c A-  Counters : 630 scintillators (  x  0.2 x 4.5  matches central tracker trigger sectors facilitates low p T muon ID and triggers pT > 1.5 GeV/c DØ Central Muon Scintillators

3 layers of mini drift tubes position resolution: 350  m 3 scintillator pixel layers (  x  x 4.5 o ) 3 layers of mini drift tubes position resolution: 350  m 3 scintillator pixel layers (  x  x 4.5 o ) The DØ Forward Muon System

Muon System performance J/  mass from muon system only pT measurement helps link to tracks found in inner tracker excellent sample for alignment and efficiency checks J/  mass from muon system only pT measurement helps link to tracks found in inner tracker excellent sample for alignment and efficiency checks

DØ Detector Performance Good Momentum resolution: u dp T /p T 2 = GeV/c (Silicon + Fiber tracker) High tracking efficiency:  pT > 0.5,  (Silicon disks) Vertex Reconstruction:   =  m (r-  ), 80  m (r-z) Excellent lepton coverage and efficiency:  muons: pT > 1.5 GeV,   electrons: pT > 2 GeV 

2.3 MHz 5 kHz1 kHz L1L2 L3 50 Hz Decision time 4.2  s Decision time 100  s Decision time ~50ms Single Sub-Det’s Towers, Tracks, E T -miss Some correl’s Not quite deadtimeless Correlations Calibrated Data Physics Objects e, ,j, ,E T -miss Simple Reco Physics Algo’s The DØ Trigger System Missing L1 Fiber Tracker Trigger - expected by end of summer Essential for low pT central muon trigger Missing half of readout computers Commissioning ongoing Silicon Tracks in the Fall 250 Hz

b-tagging with Muons Relative P T of muon wrt jet axis: p T rel Fit p T rel distribution to a mixture of b   and background templates to determine b content

Impact Parameter Based b-tagging Clear evidence of high impact parameter tracks in Muon Tagged sample!

Sin(2  ) via B  J/  + K S full reconstruction of final state u two V’s u soft pions measure decay length tag flavor at production + - ++  - - + Q > 0.2  - - b b same side flavor tag u pion charge opposite side flavor tags u lepton charge u jet charge

J/  Reconstruction

K S Reconstruction

B  J/  + K S Reconstruction Perform 4-track fit assuming B  J/  +K S constrain   and   to mass of K S and J/  force K S to point to B vertex and B to point to primary Monte Carlo

Flavor Tagging

Sin(2  Expectations for 2 fb -1 For a time dependent analysis : (S/B ~ 0.75)  D 2 ~ 10 %  t ~ 80 fs (S/B ~ 0.75)  D 2 ~ 10 %  t ~ 80 fs

B S Mixing at DØ Semileptonic modes easy, efficient trigger on final state lepton and di-leptons initial flavor tagged by opp. lepton or general tags  D 2 = % final flavor tagged by same side lepton’s charge missing neutrino and in final state degrades proper time resolution limited x s reach but measurement could come early in run Exclusive hadronic modes difficult to trigger - must require lepton from opposite b initial flavor tagged by opposite side lepton’s charge:  D 2 = 30% final flavor tagged by Ds’s charge no missing final state particles - excellent time resolution larger x s reach, but will take longer

DØ’s x s reach Monte Carlo B s mass We can measure B s mixing out to an x s of at least 30 in 2 fb -1

Conclusions A year into Run II, the DØ detector is in great shape and is taking physics data. Our trigger system will be up to speed by the end of summer - with a Silicon Track Trigger in the fall. We are poised to make significant beauty physics measurements in the next year or two: measure sin2  to an accuracy of 0.04 measure Bs mixing up to at least x s ~ 30 continue QCD studies measure  b lifetime in exclusive decays rare decays, heavy baryons,