1. Tests of the Electroweak Interactions at Hadron Colliders
37th International Conference on High Energy Physics
July 7, 2014 Valencia, Spain
Jeffrey Berryhill (Fermilab)
On behalf of ATLAS, CDF, CMS, DØ, and LHCb collaborations

2. Outline W Physics W mass W asymmetry and PDFs Z and Drell-Yan Physics
Cross sections
Sin2qeff & prospects
Diboson Physics and Triple Gauge Couplings
Dimension 6 gauge boson effective field theory (EFT)
Diboson cross sections
Triple gauge couplings
Observation of electroweak Z+2 jets
Tribosons, VBS, and Quartic Gauge Couplings
Dimension 8 gauge boson EFT
Triboson production and vector boson scattering results
VBS prospects for 13 TeV
Links for complete set of results:
CMS public electroweak results
ATLAS public electroweak results
CDF public electroweak results
D0 public electroweak results
LHCb public electroweak results
V+jets studies:
See C. Roda
QCD summary

3. State of the Electroweak Theory: Precision Frontier
Radiative corrections to precision EWK measurements of W, Z sensitive to Mt, MH
SM-like Higgs discovery
at ~126 GeV is compatible
with global EWK data
at 1.3 sigma (p = 0.18)
Indirect constraints are now superior to precise direct W, Z measurements
(MW, sin2qeff)
Can W,Z experiment catch up?

4. State of the Electroweak Theory: Energy Frontier
The successful LHC Run 1 is now providing TeV-scale tests
of single and multiple electroweak boson production
Mass of DY pairs up to 1500 GeV
PLB 725 (2013) 223
CMS-PAS-SMP
Z PT in WZ
up to 400 GeV
ATLAS-CONF
Mass of ZZ
Up to 900 GeV

5. W Physics

6. Status of Tevatron W mass
PRL 108 (2012)
PRD 89 (2014)
CDF and DØ have world’s most precise measurements based on 20% and 50% of their data → 1.1M and 1.7M Ws, resp.
MT is the most sensitive single variable, lepton PT and MET used also
Precision lepton response (0.01%) and recoil models (1%) built up from Z dileptons, Z mass reproduced to 6X LEP precision
MW precision:
CDF 19 MeV,
DØ 23 MeV,
LEP2 33 MeV
CDF W muons
PRL 108 (2012)
PRD 89 (2014)
DØ W electrons

7. Status of Tevatron W mass
PRL 108 (2012)
PRD 89 (2014)
CDF and DØ have world’s most precise measurements based on 20% and 50% of their data → 1.1M and 1.7M Ws, resp.
MT is the most sensitive single variable, lepton PT and MET used also
Precision lepton response (0.01%) and recoil models (1%) built up from Z dileptons, Z mass reproduced to 6X LEP precision
MW precision:
CDF 19 MeV,
DØ 23 MeV,
LEP2 33 MeV
2012 world average: 15 MeV

8. Prospects for Tevatron W mass
arxiv:
projected
Largest single uncertainties are stat. and PDF syst.
2X PDF improvement and incremental improvement elsewhere results in 9 MeV projected final Tevatron precision
<10 MeV precision is well motivated to further confront indirect precision (11 MeV)

9. Prospects for LHC W mass
Phys.Rev.D83:
113008,2011
The LHC has excellent detectors and semi-infinite statistics and thus has a good a priori prospect for a <10-MeV measurement
Biggest three obstacles to surmount:
PDFs: sea quarks play a much stronger role than the Tevatron. Need at least 2X better PDFs.
Momentum scale
Recoil model/MET
arxiv:

10. W charge asymmetry arXiv:1312.6283
At 7 TeV, ~4M W muon candidates produced per /fb
Differential W charge asymmetry precisely probes u/d ratio vs. x
Recent CMS measurement can precisely extract a clean W asymmetry using ~20 million W candidates!
Mu+
Mu-

11. W charge asymmetry arXiv:1312.6283
At 7 TeV, ~4M W muon candidates produced per /fb
Differential W charge asymmetry precisely probes u/d ratio vs. x
Asymmetry measured to 0.1% absolute per bin
Has obvious constraining power for all PDF families

12. W charge asymmetry PRD 88 (2013) 091102
Tevatron has only exploited a fraction of their data until recently.
DØ muon rapidity asymmetry also has clear constraining power
DØ W rapidity asymmetry uses electron and MET to estimate W rapidity directly
PRL 112 (2014)

13. W charge asymmetry NEW for ICHEP14
LHCb has unique access to high rapidity leptons
(2 < h < 4.5)
New observed 1/fb W asymmetry constrains PDFs at lower x
In agreement with CMS/ATLAS in overlap region (2-2.4)

14. W charge asymmetry arXiv:1312.6283 d-valence improvement
CMS W asymmetry is combined with HERA DIS to exhibit valence PDF improvement
Tevatron W asymmetry strongly constrains NNPDF2.3
Tevatron vs.
NNPDF2.3

15. Z and
Drell-Yan

16. Drell-Yan Cross Section at LHC (7 TeV)
JHEP 12 (2013) 030
Cross section vs. dilepton mass measured at 7 TeV, from GeV in mass.
1M events/fb/experiment at 7 TeV!
ee, mumu in agreement with each other and with the Standard Model

17. Drell-Yan Cross Section at LHC (7 TeV)
NNLO QCD corrections are important at low mass (mostly boosted events)
NLO EWK corrections and photon-induced production relevant at high masses. Photon PDF is needed for accurate predictions.
JHEP 06 (2014) 112
JHEP 12 (2013) 030
FEWZ 3 NNLO QCD + NLO EWK + ggl+l-
PLB 725 (2013) 223

18. Drell-Yan Cross Section at LHC (8 TeV)
CMS-PAS-SMP
NEW for ICHEP14
Cross section vs. dilepton mass now measured at 8 TeV, from GeV in mass.
Differential double ratios (1/sZ)(ds/dm)8TeV / (1/sZ)(ds/dm)7TeV
measured for the first time

19. Z production properties at LHC
CMS-PAS-SMP
Z PT and rapidity can now be precisely sampled and compared with predictions
Now measured at 7 (ATLAS) and 8 TeV (CMS) doubly differentially

20. Z production properties at LHC
Diverse (dis)agreement with predictions observed in low PT (resummation) and high PT (NNLO+)
arxiv:
PLB 720 (2013) 32

21. Z production properties at LHC
PDFs and UE models can improve upon tuning to this data
arxiv:
ATLAS has a new tune for PYTHIA8 and PYTHIA8+POWHEG
“AZ” and “AZNLO”
which flattens disagreement at the percent level at low PT up to 100 GeV PT
High PT Z data could potentially constrain the gluon PDF

22. Weak mixing angle at hadron colliders
In the dilepton CM, lepton angle with respect to axis of quark momentum is sensitive to interference effects: vector with axial-vector Z couplings, Z with photon, or Z with new physics
V-A int. ~ sin2qeff -1/4
Suppression of odd cos q*
term due to dilution
at 7 TeV LHC
This relation is (un)diluted in (pp) pp collisions, where reconstructed cos q* axis is (strongly) weakly correlated with real quark axis.

23. Weak mixing angle at LHC
ATLAS-CONF
Select central dilepton pairs, and also central-forward electrons with full 7 TeV dataset
Raw AFB = Count forward/backward abundance in CS frame
AFB in good agreement with PYTHIA * PHOZPR NNLO K-factor (MSTWNNLO2008)
1.8s lower angle than LEP+SLD average
backward
forward
ATLAS 5/fb
LEP + SLD

24. Weak mixing angle at Tevatron
DØ note 6426-CONF
Low dilution makes raw AFB visibly apparent
~10/fb analyzed by D0 (CDF) for ee (mumu)
Much lower PDF and energy scale systematics than realized at LHC
3X less precise than LEP+SLD
With CDF 9/fb ee, expect
Tevatron ≈ LEP ≈ SLD!
Raw AFB
LEP + SLD

25. Prospects for weak mixing angle at LHC
Need a 6X better measurement to achieve world-average precision
Statistical error hits this target with TeV
PDF uncertainty is biggest concern, needs >5-10X improvement over pre-LHC PDFs!
Lepton energy scale must also improve >5X
Gfitter: Next 2X in world direct precision (1.6E-4) will match indirect precision (1.0E-4)

26. Triple Gauge Couplings

27. Effective Field Theory and Boson Interactions
UNBROKEN
For generic new physics effects descended from some high energy scale L, explore operator product expansion with Wilson coefficients c_i
Before EWSB, 5 gauge boson interaction terms respect gauge invariance (3 CP even + 2 CP odd)
BROKEN
After EWSB, induces trilinear VVV’, VV’H, and quartic interactions with correlated coefficients.
At dim 6, expect WWg, WWZ interactions with 3 CP-even parameters (g1, k, l)
Manifested as high mass/momentum production tails

28. WZ and Wg Production PRD 87, 112003 (2013) CMS-PAS-SMP-12-006
LHC has thousands of high purity trilepton WZ candidates, tens of thousands of Wg
Photon and lepton fakes are the predominant background
No evidence of new physics in high PT tails
WZ trileptons,
Z PT
Wg,
g PT
inclusive
exclusive 0-jet

29. Zg Production Zg  llg g PT
JHEP 10 (2013) 164 
PRD 89 (2014)
PRD 87 (2013)
Zg  llg
g PT
Thousands of dilepton-photon events at 7 TeV agree with SM
MET-photon channel: Higher BR and low background at high PT gives superior (dim 8) TGC constraint
Zg MET+g
g PT

30. ZZ Production ZZ  4l ZZ mass32
ZZ Production
ATLAS-CONF
arxiv:
ZZ  4l
ZZ mass
~300 ZZ to 4-lepton candidates observed at 8 TeV/experiment with SM rate and shapes
~200 ZZ to 2l2v candidates observed at 8 TeV, give best (dim 8) TGC constraint
ZZ  2l2v
Z PT

31. WW Production (7 TeV) Thousands of candidates in dilepton channel
PRD 87 (2013)
WW Production (7 TeV)
EPJC 73 (2013) 2610
EPJC 73 (2013) 2283 
ATLAS-CONF
WW leading lepton PT, 7 TeV
WW leading lepton PT, 7 TeV
Thousands of candidates in dilepton channel
Leading lepton PT shows no anomalous contribution
Significant diboson signal in semileptonic channel
Higher BR and low background at high PT gives superior TGC constraint
W dijet mass, 7 TeV
W dijet PT,
7 TeV

32. Charged aTGCs: World Summary
Best single LHC 7 TeV measurements equal LEP2 or Tevatron combinations
Semileptonic WW gives the best information on k and l, leptonic WW and WZ better for g.
LHC 8 TeV will provide 2-3X better constraints, eclipsing LEP2
Higgs-VV’ couplings also compete here!
Probing L ≈ GeV
for c ≈ 1

33. WW Production (8 TeV) NEW for ICHEP14
PLB 721 (2013) 190 
ATLAS-CONF
NEW for ICHEP14
Kinematic shapes agree with prediction, but cross section excess observed at 20% level in CMS and ATLAS
~5000 emu ATLAS candidates with 20/fb!
Systematics from jet veto acceptance, background methods
Not yet reporting: CMS lvlv 20/fb,
WWlvjj 20/fb
Theory calculation being actively studied (jet vetoes, NNLO)
leading lepton PT, 8 TeV
WW scaled by 1.2
emu dilepton mass, 8 TeV
WW scaled by
1.2
CMS ±2.8 (stat.)±5.6 (syst.)±3.1 (lum.) pb (1.8s)
ATLAS 71.4±1.2 (stat.)±5.0 (syst.)±2.2 (lum.) pb (2.1s)
MCFM 58.7±3.0 (syst.) pb
=qq,qg MCFM NLO
+gg MCFM LO
+HWW NNLO+NNLL
Higher order/other≈ +3-4pb?

34. Electroweak Z + 2 jet production
JHEP 04 (2014) 031
JHEP 10 (2013) 062
CMS 8 TeV to be submitted
VBF Z one of 3 (interfering)
EWK Z + 2 jet amplitudes
Unique laboratory for studying rapidity gaps and VBF jet dynamics
Require dijet “VBF topology”:
large dijet mass ( GeV)
large dijet Dy (or rapidity gap)
and other kinematic information to separate from QCD Z+ 2 jet
CMS observed a 2.6s signal in the 7 TeV data after a BDT selection

35. Electroweak Z + 2 jet production
JHEP 04 (2014) 031
JHEP 10 (2013) 062
CMS 8 TeV to be submitted
>5 s evidence has been reported by both experiments at 8 TeV,
first published by ATLAS. Cross sections are consistent with SM predictions.
sEWK = 226 ± 44 fb
sVBFNLO = 239 fb
After reweighting QCD Z+2 jets in sidebands, jet dynamics well-modeled in and around search regions
sEWK = 10.7 ± 2.1 fb
sPOWHEG = 9.4 fb

36. Electroweak Z + 2 jet production
JHEP 04 (2014) 031
JHEP 10 (2013) 062
CMS 8 TeV to be submitted
Now a laboratory for studying generator behavior in VBF/VBS context!
TGC limits obtained from ATLAS less stringent than diboson

37. ATLAS Diboson Summary

38. CMS Diboson Summary

39. Quartic Gauge Couplings

40. Effective Field Theory Revisited
SM has 4 quartic interactions (QGCs): WWWW, WWZZ, WWgg, and WWZg
Dim 6 OPE has QGC correlated with TGCdibosons dominate their constraints
19 new quartic terms become relevant at Dim 8. Neutral 4 boson vertices can be non-zero (ZZZZ, ZZZg, ZZgg, Zggg).
Manifested as triboson or vector-boson scattering phenomena
SM Quartic interactions

41. WW QGC via two-photon production
JHEP 1307 (2013) 116
Two photon production
of WW (s, t, and u channel)
First search for photon-photon scattering production of WW
WWgg quartic gauge coupling one of the amplitudes
Two em events observed with no UE present
First quartic gauge coupling limits at LHC; WWgg limit two orders better than LEP or Tevatron!

42. Triboson search in WWg and WZg
arxiv:
Studied in lv+jj+g final state for best aQGC sensitivity
Photon PT exhibits no anomalous high PT tail
Cross section UL on SM triboson rate is 3.4XSM (<241 fb)
First limits ever on several aQGCs

43. W±W± scattering at LHC NEW for ICHEP14
arxiv:
CMS-PAS-SMP
NEW for ICHEP14
SM electroweak symmetry breaking with Higgs essential to preserve vector boson scattering cross section unitarity
Same-sign WW vector boson scattering production provides attractive S/B at LHC
Anomalous differential cross sections would indicate extended Higgs sector (e.g. George-Machacek H++), new particles, or (giant) anomalous QGCs

44. W±W± scattering at LHC
arxiv:
CMS-PAS-SMP
The 8 TeV data have been searched by both CMS and ATLAS for same-sign WW+2 jets
ATLAS: 500 GeV dijet mass and 2.4 rapidity gap define signal rich VBS region
ATLAS: Good agreement with SM expectation in signal and control regions. Background mainly from real multilepton sources.

45. W±W± scattering at LHC
arxiv:
CMS-PAS-SMP
Cross section in VBS region is SM-like with 3.6 s
significance (2.8 expected)
first evidence for vector boson scattering!
Limits obtained on aQGCs in a unitarized model,
L ≈ 650 GeV for c ≈ 1

46. W±W± scattering at LHC
arxiv:
CMS-PAS-SMP
CMS: 500 GeV dijet mass and 2.5 dijet rapidity gap, with top veto, Z veto, and dilepton mass > 50 GeV
Most remaining background is fake/non-prompt leptons
Observed events agree with SM predictions
2.0s excess from VBS
(3.1 expected)
−2.0 (stat)
+1.1−1.0 (syst) fb
VBFNLO: 5.8 ± 1.2 fb

47. W±W± scattering at LHC
arxiv:
CMS-PAS-SMP
aQGC limits obtained in non-unitarized scheme from dilepton mass spectrum
H++ sBR limits as low as 20 fb obtained from George-Machacek model

48. VV scattering: future prospects
Snowmass study to understand VBS potential of Run2+
Select 3 lepton or same-sign dilepton events with “VBF dijet” (dijet mass > 1 TeV )
Several modes expected to be observed with < 300/fb
5 sigma anomalous dim 8 production at the 1 TeV scale possible in Phase 1
ATLAS-PHYS-PUB

49. Summary
W and Z physics at Tevatron+LHC now providing precision tests of PDFs and NNLO QCD + NLO EWK calculations, in preparation for further constraining the precision electroweak sector.
The LHC is now the leading laboratory for exploring the gauge boson self-interactions.
The vector boson scattering era is upon us! Now poised to directly test electroweak symmetry breaking.
Joaquin Sorolla,
Valencia,

50. Backups

51. Effective Field Theory Revisited
Dim 6

52. Charged aTGCs: World Summary
 arXiv:
HVV’ operators are also induced by dim 6 anomalous interactions  Higgs sBR’s also constrain aTGCs!
Full 8 TeV Higgs data has better constraining power than 7 TeV dibosons. 8 TeV dibosons should catch up.
Full Run 1 analysis should combine Higgs and diboson data in a consistent, multi-dimensionally correlated way

53. Neutral aTGCs: World Summary
7 TeV Zg (vvg) world-leading in ZZg/Zgg sensitivity
New CMS 8 TeV ZZ (2l2v) result world-leading in ZZZ sensitivity

54. WW cross section uncertainties (theory)

55. WW cross section uncertainties (ATLAS)

56. Triboson search in WWg and WZg
CMS-PAS-SMP
Triboson search in WWg and WZg
Triboson final state is an admixture of QGC, TGC, and double radiative events

57. Triboson search in WWg and WZg
CMS-PAS-SMP
Triboson search in WWg and WZg
Dim 6 and Dim 8 operators will exhibit a high PT tail for the photon
Can interpret results in both dim 6 (k’s) and dim 8 (f’s) picture.