Electroweak Physics at the Tevatron Aidan Robson University of Glasgow for the CDF and D0 Collaborations Aspen, 13 February 2011

CDF Z  ee (from Stirling, ICHEP04) 2004, using < 100 pb –1 2 Electroweak Physics at the Tevatron

Jets W/Z Higgs Susy quark top bottom quark dibosons 3 Electroweak Physics at the Tevatron

4  Z   WZ  ZZ  WW/WZ -> l jj  Motivation  High-statistics precision measurements  Diboson physics  Outlook Electroweak Physics at the Tevatron  p T (Z) x3   (W)

Tevatron   = 1.0  = 0.6  = 2.0 muon chambers D0  =2  = m tracker had cal hadronic cal EM cal had cal solenoid pre-radiatorshower max silicon E M cal  =1 CDF Fibre tracker to |  |<1.8 Calorimeter to |  |<4 Muon system to |  |<2 Drift chamber to |  |<1 Further tracking from Si Calorimeter to |  |<3 Muon system to |  |<1.5 5 Electroweak Physics at the Tevatron

Electrons: good EM shower shape small hadronic energy isolated in calorimeter well-matching good track (except far forward) Muons: MIP in calorimeter isolated hits in muon chamber well-matching good track Z selection: 2 oppositely-charged electrons or muons invariant mass consistent with m Z W selection: exactly one electron or muon energy imbalance in reconstructed event, associated with neutrino 6 Electroweak Physics at the Tevatron W and Z selection

p T (Z) 7 p pTpT pZpZ antiprotonproton y  1/2 ln E+pzE–pzE+pzE–pz CDF [~angular variable] p T (Z) 30 0 d  /dp T p T (Z) 30 0 d  /dp T p T (Z) 30 0 d  /dp T 0<|y|<11<|y|<22<|y|<3 distribution different for different y? p T (Z) pQCD reliable resummation / parton shower with non-perturbative model resummation required multiple soft gluon radiation 30 0 Z Z 2 Z 2 Z Z/  * q q l+l+ l–l–

Earlier p T (Z) Electroweak Physics at the Tevatron 8 PRL (2008) Electron channel: Compare 4 models: Resbos with default parameters Resbos with additional NLO–NNLO K-factor NNLO (Melnikov and Petriello) NNLO rescaled at to data at 30GeV/c RESBOS event generator implements NLO QCD and CSS resummation

p T (Z) Electroweak Physics at the Tevatron 9 New measurement in muon channel Presented at the level of particles entering the detector to avoid model-dependent corrections However for comparison with previous measurement, correct to 4  and for mass window: Phys. Lett. B

p T (Z) Electroweak Physics at the Tevatron 10 At particle level: Phys. Lett. B

** 11 a T : component of p T (ll) transverse to dilepton thrust axis. Less susceptible than p T (ll) to detector effects Best variable: – highly correlated with a T /m ll ( measures scattering angle of leptons wrt beam, in rest frame of dilepton system) Electroweak Physics at the Tevatron

** 12 eee  arXiv:

** Electroweak Physics at the Tevatron 13 arXiv:

Drell-Yan angular coefficients Electroweak Physics at the Tevatron 14 LO term : determine A fb LO term cos 2 θ : higher order term (θ, φ) terms very small terms Rest frame of dilepton system Integrate over all cosθ, =0 Integrate over all φ,

Drell-Yan angular coefficients Electroweak Physics at the Tevatron 15 A2=A0 at LO ‘Lam-Tung’ relation True only for spin-1 gluons, strongly broken for scalar gluons

Drell-Yan angular coefficients Electroweak Physics at the Tevatron 16 A4 sensitive to Weinberg angle A4 using 2.1 fb -1 data = ± Translated to sin 2 θ W in FEWZ : sin 2 θ W = ± Translated sin 2 θ W in POWHEG : sin 2 θ W = ± CDF Run II Preliminary

W charge asymmetry Electroweak Physics at the Tevatron 17 A l (  )  = A(y W )  (V–A) ~ d  ( l + )/d  – d  ( l – )/d  d(x) d  ( l + )/d  + d  ( l – )/d  u(x) A W (y)  d  (W + )/dy – d  (W – )/dy d  (W + )/dy + d  (W – )/dy Run 1 measurement resulted in d quark increased by 30% at Q 2 =(20GeV) 2 W±W± pp l±l± d u u u u d

W charge asymmetry Electroweak Physics at the Tevatron 18

mWmW m W : D0: m W = ± 43 MeV/c 2 CDF: m W = ± 48 MeV/c 2 Tev: m W = ± 31 MeV/c 2 (includes Run 1) LEP: m W = ± 33 MeV/c 2 Heading to CDF 25MeV/c 2 measurement CDF  m Z (stat) published (200/pb)43 MeV expected (2.3/fb)13 MeV 19 Electroweak Physics at the Tevatron

WW Tev error improves from 62 to 49 MeV 20 Electroweak Physics at the Tevatron  W predicted in Standard Model:  W SM = 2091±2 MeV (PDG)

Dibosons Electroweak Physics at the Tevatron 21 q q’ W/Z/  W/Z W/Z/  W  Z   WW tt WZ t ZZ H → WW

ZZ photon E T (GeV) events Z  Z  non-SM h 3, ZZ  |h 3 | < 0.037, |h 4 | < (  =1.2TeV) h 3, Z  SM non-SM 22 Z  Using (Z→ll)+  and (Z→  + 

WZ q q’ W Z/  W σ(pp → WZ) = (4.1 ± 0.7) pb σ(pp → WZ) / σ(pp → Z) = (5.5 ± 0.9) x

WZ Electroweak Physics at the Tevatron 24 arXiv: σ(pp → WZ) = (3.9 (stat+sys) ± 0.31 (lumi)) pb –0.85

WZ Electroweak Physics at the Tevatron 25 arXiv: for  =2TeV

ZZ seen in 4 lepton at 5.7σ All now observed! ZZ  4l W  Z   WW tt WZ t ZZ H → WW Z Z q q’ 26 σ(pp → ZZ ) = ( (stat) ± 0.2 (syst)) pb σ(pp → ZZ) / σ(pp → Z) = ( (stat) ± 0.3 (syst)) x 10 -4

ZZ  ll Electroweak Physics at the Tevatron 27

WW/WZ  l jj Electroweak Physics at the Tevatron 28 Similar final state to low-mass Higgs: MuonsElectrons

WW/WZ  l jj Electroweak Physics at the Tevatron σ(WW+WZ ) = (18.1 ± 3.3(stat) ± 2.5(sys) )pb 5.2  significance

WW/WZ  l jj Electroweak Physics at the Tevatron 30 Use matrix element techniques 5.4 σ(WW+WZ ) = ( ) pb 5.4  significance

Tevatron outlook End : Sep 2011(?) Integrated luminosity (pb –1 ) On tape: ~ 8.5 fb -1 per experiment Results shown today : 1-7 fb -1 now Electroweak Physics at the Tevatron

Outlook ♦ Completing strong electroweak physics programme ♦ Focusing on high-statistics Tevatron legacy measurements and diboson physics underpinning symmetry-breaking searches 32 Electroweak Physics at the Tevatron

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WW/WZ  l jj Electroweak Physics at the Tevatron 35 differences q.g jets

W+W+ W–W– Z/  W+W+ W–W– W+W+ W–W– W+W+ W–W– W+W+ W–W– W+W+ W–W– W+W+ W–W– W+W+ W–W– W+W+ W–W– W+W+ W–W– H H required to cancel high- energy behaviour WW scattering 36

W/Z primitive objects Electroweak Physics at the Tevatron 37 for non-collider physicists

H g g p p 38 Electroweak Physics at the Tevatron

PDFs Higgs Physics at the Tevatron Tevatron y = LHC H g g p p  pp → H =  gg → H f g/p (x 1,Q=M H ) f g/p (x 2,Q=M H ) + … 39

40/54Higgs Physics at the Tevatron Matrix element method  Use LO matrix element (MCFM) to compute event probability H  WW  l l WW  l l ZZ  ll W+parton  l +jet W  l +  E T model lepton energy resn pxpypzpxpypz lep1 LO | M | 2 : pxpypzpxpypz lep2 E x, E y parton  lepton fake rate  conversion rate x obs : (with true values y )  Compute likelihood ratio discriminator R = P s P s +  k b i P b i i k b is relative fraction of expected background contrib. P s computed for each m H  Fit templates (separately for high S/B and low S/B dilepton types)

41/54Higgs Physics at the Tevatron Neural network method NN score 0 1 var1 var2 var n Background Higgs  Various versions. Current:  Apply preselection (eg E T to remove Drell-Yan)  Train on {all backgrounds / WW} against Higgs m H =110,120…160…200 { possibly separate ee,e ,  x10  Pass signal/all backgrounds through net  Form templates NN 0 1  Pass templates and data to fitter E T  E T m ll E lep1 E lep2 E T sig Data HWW WW DY Wg WZ ZZ t fakes E T jet1  R leptons  leptons  E T lep or jet E T jet2 N jets Most recent CDF “combined ME/NN” analysis also uses ME LRs as NN input variables

mtmt Matrix element-based top mass measurement Lepton+jets with 4.8fb -1 NN for background discrimination Likelihood fit over variables sensitive to top mass Simultaneous constraint of jet energy scale using W in lepton+jets m t =172.8 ± 1.3 total GeV (0.7 stat 0.6 JES 0.8 sys ) More precise than CDF 2009! Expect 1GeV precision achievable E T model lepton energy resn pxpypzpxpypz lep1 pxpypzpxpypz jet1 E x, E y x obs : (true values y ) etc. Higgs Physics at the Tevatron 42

Single top Single top observed u W l g b b b t W d u W l b b t W d t-channel s-channel t-channel cross section [pb] s-channel cross section [pb] Higgs Physics at the Tevatron 43

Limit setting Higgs Physics at the Tevatron 44 background suppression signal separation Background Higgs signal x 10 events X X = some observable H 1 =SM+Higgs (of mass m H ) H 0 =SM only  Construct test statistic Q = P(data|H 1 )/P(data|H 0 ) –2lnQ =  2 (data|H 1 ) –  2 (data|H 0 ), marginalized over nuisance params except   H  Find 95 th percentile of resulting   H distribution – this is 95% CL upper limit.  When computed with collider data this is the “observed limit”  Repeat for pseudoexperiments drawn from expected distributions to build up expected outcomes  Median of expected outcomes is “expected limit” Expected outcomes 95% CL Limit/SM Median = expected limit  H (pb) 95%  H /  SM 95% rescale PDF

Indirect constraints e+e–e+e– ZHZH Z bbbb m H >114GeV m H <154GeV estimated final precision 45

Tevatron projection Higgs Physics at the Tevatron 46 End : Sep 2011? On tape: ~ 6 fb -1 per experiment Results shown today : 3-5 fb -1 Integrated luminosity (fb –1 )

47/22 Aidan Robson Glasgow University W charge asymmetry unknown neutrino p Z  is a smaller effect for higher E T electrons measurement divided into two E T regions for given  e, E T regions probe different y W and therefore different x experimental challenges: alignment; charge misidentification measurement relies on calorimeter- seeded silicon tracking PRD First Run 2 charge asymmetry measurement: similar approach to Run 1 e|e| e|e|

48/22 Aidan Robson Glasgow University W charge asym. – new method Instead: probe the W rapidity directly M W constraint  two kinematic solutions for p z of  Ambiguity can be resolved statistically from known centre-of-mass  * distribution for V-A decay  weight solutions according to (cos  *, y, p T W ) d  /dy is an input; iterate to remove dependence. Uncertainties: Charge mis-ID rate Energy scale and mismeasurement Background/trigger/electron ID Relies on Si-only tracking cos  *

49/22 Aidan Robson Glasgow University W charge asym. – new method Under improvement using better forward tracking and higher stats

W width  Generator: LO MC matched with Resbos (QCD ISR) and Berends/Kleiss (QED FSR)  Fast simulation for templates: electron conversions + showering muon energy loss parametric model of recoil energy (QCD, underlying event + brem)  Tracking scale/resn  Calorimeter scale/resn m  (GeV) m ee (GeV)  Backgrounds m T (GeV)  21 MeV, 31 MeV  17 MeV, 26 MeV  32 MeV  33 MeV  54 MeV (ele), 49 MeV (mu)  2 /dof = 27.1/22  2 /dof =18/22

 W = 2032 ± 73 (stat+sys) MeV  W SM = 2091 ± 2 MeV) PRL (2008) Compare to CDF indirect measurement: NNLO calcFrom LEP SM value  W (indirect) = 2092 ± 42 MeV J Phys G World most precise single measurement W width