Electroweak Physics at the Tevatron Adam Lyon / Fermilab for the DØ and CDF collaborations 15 th Topical Conference on Hadron Collider Physics June 2004 Outline  Importance  Methodology  Single Boson Measurements  Summary & Outlook  W/Z+  and Diboson Results up next

2 A. Lyon (HCP2004) Learning from Electroweak Physics  m W, m t, and m H are related  Constrain Higgs mass  Test of standard model couplings (and see M. Kirby's talk)  Study higher order QCD  Many uses in detector studies and luminosity determination

3 A. Lyon (HCP2004) Uncertainties in m W  Run 1 uncertainties (from hep-ex/ )  Uncorrelated uncertainties scale with luminosity  Correlated systematics improve as theory improves  Perhaps can reach 40 MeV/ c 2 per channel & exp with 2 fb -1

4 A. Lyon (HCP2004) Collider: Tevatron for Run II Base goal is 4.4 fb -1 (Design is 8.5 fb -1 ) by end of FY09

5 A. Lyon (HCP2004) Detectors: CDF  Saved from Run I  Solenoid  Central Calorimeter  Central Muon System  New/Improved in Run II  8 layer Si tracking (|  | < 2)  Central Outer Tracker (|  | < 1)  Plug Calorimeter (1.0 < |  | < 3.6)  Extended muon coverage to |  | < 1.5  New and improved trigger and DAQ  Luminosity  ~400 pb -1 on tape  Analyses shown here use pb -1

6 A. Lyon (HCP2004) Detectors: DØ  Saved from Run I  Hermetic LAr Calorimeter  Muon Toroid and proportional drift tubes  New in Run II  2T Superconducting Solenoid  Inner Tracker (Si Microstrips and Scintillating Fiber tracker)  Preshower detectors  Upgraded muon system (including better shielding)  New and improved trigger and DAQ

7 A. Lyon (HCP2004) Detectors: DØ  Luminosity 370 pb -1 on tape Analysis here use pb -1

8 A. Lyon (HCP2004) W/Z Production and Event Topology  Use clean leptonic decays  W  (energetic lepton + E T )  Z 0 (energetic opposite sign leptons)

9 A. Lyon (HCP2004) W and Z events are extremely useful  Measure cross sections  Calibration of detectors, luminosity measurements  Lepton universality, W width  Measure W and Z properties ( p T (W), p T (Z), y(Z), lepton angular distributions)  Constrain PDFs, fit for couplings, look for new resonances  Measure W m T, lepton p T spectra  Yields m W, W width  W/Z + Jets  Backgrounds to Higgs and Top analyses  W/Z + , Dibosons  Probe electroweak gauge structure  Backgrounds to New Phenomena searches

10 A. Lyon (HCP2004) Analysis Methodologies  Both DØ and CDF follow similar strategies  Triggers:  Calorimeter triggers for electrons  Track triggers for muons  Selection:  W - a lepton and large missing transverse energy  Z - two opposite charge leptons  Electron requirements:  Isolated EM cluster  Shower shape (CDF uses shower max, DØ has finely segmented calorimeter)  Track pointing to calorimeter EM cluster  Muon requirements:  Track matched to calorimeter MIP trace and/or muon system track  Reject cosmics by timing and impact parameter  Track and calorimeter isolation  Measure identification efficiencies with Z events  Measure backgrounds with QCD Dijet events  Systematics  Luminosity (~6%)  PDF (use CTEQ6 and MRST) (1-2%)  Lepton ID (~1%)  Backgrounds, E scale, Recoil model, Detector Description

11 A. Lyon (HCP2004) Z  ee Cross Section  2 EM objects with p T > 25 GeV/ c  CDF: central + plug cal (|  |< 2.8)  DØ: central only  Small backgrounds  QCD  Z  CDF: DØ:

12 A. Lyon (HCP2004) Z   Cross Section  p T cut lowered to GeV/c for muons  DØ efficient for m  > 30 GeV/ c 2  DØ applies a Drell-Yan correction  Very small backgrounds: QCD (b-jets), Z   CDF: DØ:

13 A. Lyon (HCP2004) W  e Cross Section  Requirements:  1 electron with E T > 25 GeV  E T > 25 GeV (CDF plug analysis used 20 GeV)  CDF: central & plug  DØ requires |  | < 1.1  Track match required  Backgrounds  QCD, Z  ee, W  

14 A. Lyon (HCP2004) W  e Cross Section CDF (central): DØ: CDF (plug):

15 A. Lyon (HCP2004) W   Cross Section  Require  p T, E T > 20 GeV  Backgrounds: QCD (b-jets), Z  , W   CDF: DØ:

16 A. Lyon (HCP2004) Cross section comparisons * Track match required  CDF and DØ are rather similar, except in angular coverage  CDF uses plug calorimeter for far e coverage  DØ uses forward muon system for far  coverage

17 A. Lyon (HCP2004)  Use measured W and Z cross sections and R  Measured (CDF Preliminary)  Theory (NNLO, PDG)  LEP  Infer the W width (Preliminary)

18 A. Lyon (HCP2004) Analyses with Taus  Reconstructing  leptons is challenging  Must use hadronic decays for ID (1 or 3 charged tracks plus  0 's)  But these are hadronic jets; high QCD background  Look for tracks in a narrow 10° cone pointing toward a narrow calorimeter cluster  Require 30° cone isolation for tracks  Reconstruct  0 's (in shower max for CDF)  Require effective mass of tracks and  0 's to be < 1.8 GeV/ c 2 ( m  + resolution)

19 A. Lyon (HCP2004) W   (CDF Run II Preliminary)  Start with track + E T trigger  Require   E T > 25 GeV, E T > 25 GeV  No other jets above 5 GeV  2345 candidates in 72 pb -1  Bkg = 612  61 events   ID  · A = 1.06  %

20 A. Lyon (HCP2004) Z    Look for 1-prong decays  Look for other  via e or   Understand tau ID  Important for searches  Proof of principle that  resonances are seen at the Tevatron CDF:

21 A. Lyon (HCP2004) Charge asymmetry in W  e  Goal is to improve understanding of PDFs using W charge asymmetry  Since u quarks on average carry more of the p momentum than d quarks,  W + produced in ud  W + are boosted along p  W - produced in du  W - are boosted along p  The e  from the W decay carries information on the W direction, but true W direction cannot be reconstructed due to unmeasured p z of  Use the e  direction to measure A yW convoluted with V-A decay distribution  Results are sensitive to ratio of PDFs for u and d  Do for low and high E T [NEW APPROACH] (at higher e E T, e dir is closer to W dir; less cancellation with V-A )  Sensitivity is best at high |  | where it is least constrained

22 A. Lyon (HCP2004) Charge asymmetry in W  e  Require  e E T and E T > 25 GeV  50 < m T < 100 GeV  No other EM object with E T > 25 GeV  In forward region, use "calorimeter seeded Si tracking" to utilize new forward Silicon  This along with drift chamber can determine charge within |  | < 2  Measure charge mis-id rate with data using Zs  < ~1% within |  | < 1.5  < ~4% far forward  Backgrounds  Z [MC], W   [MC], QCD [data]

23 A. Lyon (HCP2004) Drell-Yan Forward Backward Asymmetry  Interference of  * and Z f = u, d, e  Leads to A FB in  Depends on uuZ, ddZ and eeZ couplings  Can probe couplings  Near the Z resonance, A FB is related to sin 2  W  New interactions may modify the SM A FB prediction Z ** f f f ’ + f f  q q e-e- e+e+

24 A. Lyon (HCP2004) Drell-Yan Forward Backward Asymmetry CDF Run II Preliminary  Require 2 isolated electrons with p T > 20 GeV/c  5211 candidates in 72 pb -1  No asymmetry seen in dijet background  Use Collins-Soper reference frame for measuring electron scattering angle  Reduces uncertainty in scattering angle due to p T of incoming partons

25 A. Lyon (HCP2004) Drell-Yan Forward Backward Asymmetry CDF Run II Preliminary  Fit for weak mixing angle  Fits for couplings are in good agreement with world averages  No evidence of new interactions above the Z pole

26 A. Lyon (HCP2004) High Mass Drell-Yan Spectrum  Sensitive to new physics  New gauge bosons (e.g. Z' ), extra dimensions  Run 1 limits surpassed and new models explored

27 A. Lyon (HCP2004) Summary  Current preliminary results consistent with SM  (Theory lines NNLO from Hamberg, van Neerven, Matsuura)

28 A. Lyon (HCP2004) Outlook  1.96 TeV cross sections nearing publication  Tevatron electroweak working group will make combinations  Stay tuned for further analyses; > 300 pb -1 on tape  Preliminary W mass measurements soon

29 A. Lyon (HCP2004) EXTRAS

30 A. Lyon (HCP2004) Z  ee Cross Section

31 A. Lyon (HCP2004) Afb Acceptance

32 A. Lyon (HCP2004) Uncorrected A fb