Download presentation

Presentation is loading. Please wait.

Published byEmily Garrison Modified over 4 years ago

1
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

2
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:1208.5967) MRST2004QED PDF used (includes QED corrections to DGLAP evolution of PDFs) Introduction D.Bourilkov, Florida, CMS EW Corrections in Z and DY 2

3
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

4
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 2012 @ TeV will start probing at this level of precision Electroweak Corrections for Z/* D.Bourilkov, Florida, CMS EW Corrections in Z and DY 4

5
Early Studies LHC SM workshop “SM Physics (and more) at the LHC” CERN Yellow Report 2000-004 http://arxiv.org/abs/hep-ph/0003275 Studies for 14 TeV Highlighted the importance of pure EW corrections D.Bourilkov, Florida, CMS EW Corrections in Z and DY 5

6
Z Cross Sections @ 8 TeV https://cdsweb.cern.ch/record/1460098 Dedicated low pile-up run at 8 TeV Pair mass 60-120 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

7
Inclusive Z Cross Sections @ 8 TeV 10710 Z events, very low background Experimental uncertainties 2.8-1.9% for ee, Systematics dominated by lumi (4.4 %) and theory uncertainty, mainly acceptance (2.6-1.9%) EW corrections smaller D.Bourilkov, Florida, CMS EW Corrections in Z and DY 7

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

9
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

10
Drell-Yan Mass Spectrum https://cdsweb.cern.ch/record/1439026 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

11
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 45-60 and 60-120 GeV: excellent agreement with POWHEG and FEWZ Z peak bin systematics limited 120-200 and 200-1500 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

12
Forward-backward Asymmetry http://cdsweb.cern.ch/record/1430637 POWHEG+PYTHIA+CT10 Forward-backward asymmetry will become sensitive to EW corrections D.Bourilkov, Florida, CMS EW Corrections in Z and DY12

13
Z P T Z P T spectrum at 7 TeV http://arxiv.org/abs/1110.4973 Theory predictions: QCD at NNLO New physics can show up in the tail D.Bourilkov, Florida, CMS EW Corrections in Z and DY 13

14
Z’ Search @ 7 TeV http://lanl.arxiv.org/abs/1206.1849 Accumulating events > 1 TeV Entering the Sudakov zone D.Bourilkov, Florida, CMS EW Corrections in Z and DY 14

15
Z’ Search @ 8 TeV https://cdsweb.cern.ch/record/1461216 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

16
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

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

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

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

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

21
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

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

Similar presentations

© 2020 SlidePlayer.com Inc.

All rights reserved.

To make this website work, we log user data and share it with processors. To use this website, you must agree to our Privacy Policy, including cookie policy.

Ads by Google