Photon + Jets

1. Photon + Jets Michael Anderson March 4, 2009

2. Today • Plots g’s and jets faking g’s • Results of Fisher multivariate to discriminate g’s and g’s faked by jets • I use pythiag+jet events for signal sample and pythia QCD for background

3. g+jet Monte Carlo • ET distribution of the ggen from the hard-scattering for • Barrel |h|<1.45 • Endcap 1.55<|h|<2.50 • Required ET(ggen)>20 GeV Scaled to 200pb-1 -ggen(Barrel) -ggen (Endcap)

4. g+jet Monte Carlo • Current default in CMSSW requires that H/E < 0.2before a superclustercan be turned into a “reco::Photon” Scaled to 200pb-1 -ggen(Barrel) -ggen (Endcap)

5. g+jet Monte Carlo • To match grec to ggen, required:Dh < 0.15, and Df < 0.1 Scaled to 200pb-1 -Barrel -Endcap -Barrel -Endcap

6. g+jet Monte Carlo • ET distribution of • gen g from the hard scattering (ET>20GeV, and|h|<1.45) and • the DR matched recg (DR<0.1, and H/E<0.2) • Photons are notbeing increasinglylost, they’re justshifted to lower energy [see next slide] Scaled to 200pb-1 -ggen -DR-Matched grec

7. g+jet Monte Carlo • ET distribution of • gen g from the hard scattering (ET>20GeV, and|h|<1.45) and • gen g IF a DR matched recg was found (DR<0.1, and H/E<0.2) • Loss of ~1% of g’s in Barrel is roughly constant as functionof ET(ggen) Scaled to 200pb-1 -ggen -ggen if DR-Matched grec found

8. g+jet Monte Carlo • ET distribution of • gen g from the hard scattering (ET>20GeV, and 1.55<|h|<2.5) and • the DR matched recg (DR<0.1, and H/E<0.2) • This is the Endcap,and again energy is being lost, notg’s [see next slide] Scaled to 200pb-1 -ggen -DR-Matched grec

9. g+jet Monte Carlo • ET distribution of • gen g from the hard scattering (ET>20GeV, and 1.55<|h|<2.5) and • the DR matched recg (DR<0.1, and H/E<0.2) • Loss of ~1% of g’sin Endcap is roughlyconstant withET(ggen) Scaled to 200pb-1 -ggen -ggen if DR-Matched grec found

10. g+jet Monte Carlo • Energy resolutiondistribution of DR matched grec in • Barrel and • Endcap • Required ET(ggen)>20GeV • Location of grecbelow thisshown onnext 3 slides Scaled to 200pb-1 -Barrel -Endcap

11. g+jet Monte Carlo • fmod in Barrel of grecwhen Energy loss is > 10% • fmod = f to nearest module boundary (there are 18 module boundaries in f) Scaled to 200pb-1 Barrel

12. g+jet Monte Carlo • f in Endcap of grecwhen Energy loss is > 10% Scaled to 200pb-1

13. g+jet Monte Carlo • |h| of grec when Energy loss is > 10% • There are 4 module boundaries in barrel Scaled to 200pb-1 ECAL System

14. QCD Monte Carlo • ET distribution of the grec in Barrel from • QCD (Highest grec in event) • g+jet events (the grecDR matched to ggen from hard scattering) • Required only • ET > 20 GeV • H/E < 0.2 Scaled to 200pb-1 -grec (from QCD) -grec(from g+jet) Will run on higher pT QCD events soon

15. QCD Monte Carlo • H/E distribution of the grec in Barrel from • QCD (Highest grec in event) • g+jet events (the grecDR matched to ggen from hard scattering) • Required only • ET > 20 GeV • H/E < 0.2 Scaled to 200pb-1 -grec (from QCD) -grec(from g+jet)

16. Fisher Input • Plots on the next 2 slides show area-normalized inputs to Fisher to discriminate g’s and jets faking g’s: • SEcal in 0.4 cone / ET(g) • STrackpT in 0.4 cone / ET(g) • R9 = E3x3/E(g) • Zernike-20 moment • E2x5 / E5x5 • E3x2 / E5x5 • E-weighted f width • E-weighted h width Cuts on both signal and background grec: H/E < 0.2 |h| < 1.45 (in Barrel) ET > 20 GeV ET < 500 GeV Trained with: 250K signal events 250K background events Tested with: 1.9M signal events 2.2M background events

17. Fisher Input

18. Fisher Input

19. Fisher Result

20. Next • Add in higher QCD bins • Do for endcap events as well • Make cut on HCAL Isolation • Try non-linear Fisher • Cut events near ECAL module boundaries?