EW Corrections for CMS Z and Drell-Yan Measurements Dimitri Bourilkov University of Florida For the CMS Collaboration Working Group on Electroweak precision measurements at the LHC, and PDF4LHC, CERN, October 9, 2012

 Electroweak (EW) corrections around the Z peak and for high mass Drell-Yan  Review of CMS Z (W) and Drell-Yan results  Reached/expected experimental precision  control QCD and EW corrections in precision calculations  Calculations with FEWZ3.1: a tool to calculate simultaneously QCD corrections up to NNLO and EW corrections at NLO:  O(α s 2 ) + O(α EW ) for Z/γ ∗ → ℓℓ (arXiv: )  MRST2004QED PDF used (includes QED corrections to DGLAP evolution of PDFs) Introduction D.Bourilkov, Florida, CMS EW Corrections in Z and DY 2

 Non-resonant contributions from s-channel * exchange  Gauge invariance of photonic O() corrections  splitting in QED (not discussed here) and pure weak O() corrections:  Near Z peak: l QED corrections described by radiator functions l Weak corrections absorbed in line shape parameters  Invariant mass M l + l - directly related to off- shellness of Z boson  EW corrections depend on the scales probed; important for mass determinations (W), for high invariant masses of Z/* Electroweak Corrections for Z/* D.Bourilkov, Florida, CMS EW Corrections in Z and DY 3

 At the TeV scale, large and significant impact of pure weak corrections; factors like Sudakov logs (from vertex and box corrections) modify the inclusive cross sections:  ~  W ln 2 ( 2 /M W 2 )  At  = 1 TeV this is ~ 25 *  W  Effects ~ 10 % in the TeV region  Data in TeV will start probing at this level of precision Electroweak Corrections for Z/* D.Bourilkov, Florida, CMS EW Corrections in Z and DY 4

Early Studies LHC SM workshop  “SM Physics (and more) at the LHC” CERN Yellow Report Studies for 14 TeV Highlighted the importance of pure EW corrections D.Bourilkov, Florida, CMS EW Corrections in Z and DY 5

Z Cross 8 TeV Dedicated low pile-up run at 8 TeV Pair mass GeV Lepton P T > 25 GeV, || < 2.1 for muons, || < 2.5 for electrons (excluding barrel-endcap transition) Lineshape described well by POWHEG+PYTHIA D.Bourilkov, Florida, CMS EW Corrections in Z and DY 6

Inclusive Z Cross 8 TeV Z events, very low background Experimental uncertainties % for ee,  Systematics dominated by lumi (4.4 %) and theory uncertainty, mainly acceptance ( %) EW corrections smaller D.Bourilkov, Florida, CMS EW Corrections in Z and DY 7

W/Z Ratios and 8 TeV Satisfactory agreement with NNLO predictions: FEWZ + MSTW2008 D.Bourilkov, Florida, CMS EW Corrections in Z and DY 8

W/Z Ratios and 8 TeV Only PDF uncertainties are included in the theory uncertainties D.Bourilkov, Florida, CMS EW Corrections in Z and DY 9

Drell-Yan Mass Spectrum Lepton pairs with P T > 14,9 GeV , > 20 GeV ee FSR effects unfolded (“Born” leptons, before QED FSR) NNLO predictions with FEWZ+MSTW08 NNLO effects at low mass important D.Bourilkov, Florida, CMS EW Corrections in Z and DY 10

Drell-Yan Double Diff. Cross Section Double differential cross section in M & Y In CMS acceptance, for , normalized to Z cross section 6 bins in M, 24 or 12 bins in |Y| Low mass needs more work, improve theory predictions and GeV: excellent agreement with POWHEG and FEWZ Z peak bin systematics limited and GeV: good agreement with POWHEG and FEWZ High mass bin statistics limited; will improve with 8 TeV data D.Bourilkov, Florida, CMS EW Corrections in Z and DY 11

Forward-backward Asymmetry POWHEG+PYTHIA+CT10 Forward-backward asymmetry will become sensitive to EW corrections D.Bourilkov, Florida, CMS EW Corrections in Z and DY12

Z P T Z P T spectrum at 7 TeV Theory predictions: QCD at NNLO New physics can show up in the tail D.Bourilkov, Florida, CMS EW Corrections in Z and DY 13

Z’ 7 TeV Accumulating events > 1 TeV Entering the Sudakov zone D.Bourilkov, Florida, CMS EW Corrections in Z and DY 14

Z’ 8 TeV Expanding the reach above 1 TeV By the end of the 2012 run the statistical precision will start to probe EW corrections D.Bourilkov, Florida, CMS EW Corrections in Z and DY 15

 Calculations with FEWZ_3.1.b2 (good backward compatibility with FEWZ2): a tool to calculate simultaneously QCD corrections up to NNLO and EW corrections up to NLO for Z and DY production  Results for QCD NLO  EW NLO shown  MRST2004QED PDF used  G  scheme to “minimize” higher order EW corrections  “Standard” input file for muons  Roughly in CMS acceptance:  P T > 25 GeV, || < 2.4 for both leptons EW Corrections with FEWZ3.1 D.Bourilkov, Florida, CMS EW Corrections in Z and DY 16

EW Corrections with FEWZ3.1: Mass D.Bourilkov, Florida, CMS EW Corrections in Z and DY 17

EW Corrections with FEWZ3.1: A fb D.Bourilkov, Florida, CMS EW Corrections in Z and DY 18

EW Corrections with FEWZ3.1: Y D.Bourilkov, Florida, CMS EW Corrections in Z and DY 19

EW Corrections with FEWZ3.1: P T D.Bourilkov, Florida, CMS EW Corrections in Z and DY 20

 EW corrections will grow in importance for the complete 2012 data set  New tools e.g. FEWZ3.1 (beta) available to study these effects  First round of calculations looks promising  Refine the studies:  QCD NNLO  EW NLO  Realistic experimental cuts for electrons and muons Outlook D.Bourilkov, Florida, CMS EW Corrections in Z and DY 21

D.Bourilkov, Florida, CMS EW Corrections in Z and DY 22 Backup Slides