1 Electroweak Measurements from Run II at the Tevatron Presented on behalf of CDF and D by: Terry Wyatt University of Manchester, UK With special thanks to the other members of the Tevatron Electroweak Working Group: Sarah Eno, Harald Fox, Martin Grnewald, Eva Halkiadakis, Eric James, Ashutosh Kotwal, Giulia Manca, Sean Mattingly, Pasha Murat, Emily Nurse, Michael Schmitt, Georg Steinbrck, Paul Telford, Alexei Varganov, Marco Verzocchi, Junjie Zhu 2 Overview Introduction Measurements of: Z Br(Zl + l ) W Br(Wl ) CDF + D combinations: Z Br(Zl + l ), W Br(Wl ) W Br(Wl ) Z Br(Zl + l ) Other measurements with W and Z Di-boson production Summary and Outlook R = 3 Delivered and Collected Luminosity Tevatron Run II: proton-antiproton collisions at 1.96 TeV 4 W and Z Production Need accurate knowledge of PDFs: modify longitudinal boost experimental acceptance Correct for photon: N Z = N cand [ Z / Z ] MC Z/ e-e- e+e+ 5 Experimental Signature: Zl + l pair of charged leptons: high p T isolated opposite-charge redundancy in trigger and offline selection low backgrounds control of systematics 6 Experimental Signature: Wl single charged lepton: high p T isolated E T miss (from neutrino) less redundancy in trigger and offline selection more difficult to control backgrounds and systematics need to understand hadronic recoil but more interesting than Z! (post-LEP) Br 10 times larger than Z 7 DD CDF 8 D Z + Event selection: Two central tracks: loose -id p T > 15 GeV opposite charge || < 1.8 M > 30 GeV Cosmic veto 1 isolated Dominant systematics: luminosity: 10% efficiency measurements from Z + data: 3.3% (statistics limited) N cand = 6126 L = 117 pb -1 Backgrounds: QCD: (0.6 0.3)% Z + : (0.5 0.1)% total = 19% (updated for this conference) 9 Measuring Efficiencies using the Z + data There are two s The backgrounds are low Can select pure Z sample with even looser cuts on one Level-1 trigger efficiency Z Br(Z + ) = 5.0 8.9 26.2 pb stat. syst. lumi. 10 CDF: Z + Event selection: Two central tracks: p T > 20 GeV opposite charge minimum ionizing in CAL at least one || < 0.6 both || < < M < 116 GeV Cosmic veto cosmic background (0.9 0.9) % Largest systematics: luminosity: 6% PDFs: 3% N cand = 1631 L = 72 pb -1 total = 9% Z Br(Z + ) = 246 6 12 15 pb stat. syst. lumi. 11 CDF and D Ze + e Two isolated electrons, E T > 25 GeV, || < 1.1 N cand = 1631 L = 42 pb -1 CDF: Z Br(Ze + e ) = 6.3 15.2 16.0 pb D: Z Br(Ze + e ) = 275 9 9 28 pb stat. syst. lumi. 12 CDF: We p T (e) > 25 GeV E T miss > 25 GeV N cand = QCD background estimate (3.5 1.7)% W Br(We ) = 2.64 0.01 0.09 0.16 nb stat. syst. lumi. 13 CDF: W p T () > 20 GeV E T miss > 20 GeV N cand = Backgrounds: (10.81.1)% Systematics: PDFs 2.6% hadronic recoil 1.6% W Br(W ) = 2.64 0.02 0.12 0.16 nb stat. syst. lumi. 14 D: We and W p T (e) > 25 GeV E T miss > 25 GeV N cand = L = 42 pb -1 p T () > 20 GeV E T miss > 20 GeV N cand = 8302 L = 17 pb -1 W Br(We ) = nb W Br(W ) = nb stat. syst. lumi. 15 CDF: W Look for jet within narrow 10 degree cone Isolated within wider 30 degree cone p T ( ) > 25 GeV E T miss > 25 GeV N cand = 2345 W Br(W ) = 2.62 0.07 0.21 0.16 nb stat. syst. lumi. 16 Comparing and Combining Br (W,Z) Measurements from CDF and D Luminosity determination: measure total rate of inelastic pp collisions inelastic measurements by CDF and 1.8 TeV disagree at ~3 level different methods of averaging CDF and E811 give values in the range: 59.1 < inelastic < 60.7 mb (extrapolated to 1.96 TeV) (2.7% difference) For Br (W,Z) results quoted above: CDF uses inelastic = 60.7 mb D uses inelastic = 57.6 mb (5.3% difference) 17 Comparing and Combining Br (W,Z) Measurements from CDF and D For my combinations presented below I have chosen to: Scale reported Br (W,Z) values to correspond to consistent value of inelastic Arbitrarily chose: inelastic = 60.7 mb Multiply Br (D ) by factor Quote additional 2.7% syst. error to cover ambiguity in choice of inelastic total error of ( = 4.8)% assumed for inelastic 100% correlated between CDF and D PDFs next most significant error (13)% N.B. These issues have been discussed within Tevatron EWWG, but . No official policy yet agreed by CDF and D my combinations should be taken as the responsibility of a review speaker: not official CDF / D results 18 Standard Model: Z Br(Zl + l ) = 252 9 pb NNLO calculation [Nucl.Phys. B359 (1991) 343] NNLO MRST2002 PDFs 3.5% uncertainty assessed using CTEQ error PDFs [But also see talk by Robert Thorne at this conference] LEP Br(Zl + l ) = Tevatron Average Z Br(Zl + l ) = 258 10 16 pb expt. lumi. expt. error from counting Zs statistics limited 19 Standard Model: W Br(W l ) = 2.72 0.10 nb NNLO calculation [Nucl.Phys. B359 (1991) 343] NNLO MRST2002 PDFs 3.5% uncertainty assessed using CTEQ error PDFs SM Br(W l ) =.1082 .0002 Tevatron Average W Br(W l ) = 2.69 0.09 0.17 nb expt. lumi. N.B. expt. error will always be smaller than lumi. In the future we can use Br(W,Z) to determine the luminosity 20 W Br(Wl ) Z Br(Zl + l ) Luminosity error cancels Other important systematics partially cancel: PDFs Experimental: high p T, isolated leptons Tevatron EWWG: Evaluated correlated systematics Performed official average of CDF(e,) and D(e) shown at EPS-Aachen Update including D() here R = 0.20 Run (I + II) 0.30 Run II 22 Indirect measurement of Br(Wl ) measure W Br(Wl ) Z Br(Zl + l ) NNLO LEP calculation R = 23 Indirect measurement of W Br(Wl ) = (Wl ) / W SM Tevatron combined result : W = GeV cf LEP+Tevatron direct measurements: W = GeV Promising future for such measurements with ~2 fb -1 : O(10 6 ) Wl events per channel per experiment O(10 5 ) Zl + l events per channel per experiment for calibration LEP2: O(10 3 ) Wl decays per channel per experiment my combination 24 Other measurements with W, Z events High mass tail of Z Forward-backward asymmetry D Run II Preliminary 25 Other Measurements with W,Z Events Data/MC comparisons for p T (Z) probe QCD phenomenolgy Many more such measurements to come: e.g, W/Z rapidity probe PDFs Z + 26 Looking for Z + Look for isolated, high p T e or opposite narrow hadronic jet CDF D small numbers of candidates rates consistent with expectations M( ) 27 CDF W , Z Events Require central E T ( ) > 7 GeV Br quoted for R(l- ) = ( 2 + 2 ) >0.7 these cuts (updated for this conference) L = 128 pb-1 47 seen 43 expected 133 seen 141 expected Br = 5.8 1.0 (stat.) 0.4 (syst.) 0.4 (lumi.) pb Br = 17.2 2.2 (stat.) 2.0 (syst.) 1.1(lumi.) pb 28 CDF W W Search isolated lepton pair opposite-charge, high p T E T miss Z veto veto events with jets L = 126 pb -1 5 events seen 9.2 events expected (2.3 background, 6.9 1.5 W W l l ) (updated for this conference) 29 Summary, Outlook EW analyses with Run II L > 100 pb -1 becoming available Detectors/triggers/simulations becoming better understood entire physics programme benefits Looking forward to a flood of new EW results this autumn: Br (W,Z) and ratios QCD of W,Z production Tevatron EWWG becoming very active Need more streamlined procedure for CDF/D to approve combinations of updated measurements once combination methods are well-established