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## Optimizing the W resonance in dijet mass

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**Optimizing the W resonance in dijet mass**Daniel Abercrombie Pennsylvania State University 8 August 2013 Advisors: Phil Harris and Andreas Hinzmann**The Goal of the Project**• Compare jet cone sizes and algorithms • Identify the algorithm and parameters that givesa stable W mass and narrowest resonance • Results will be used in talks with ATLAS to determine a common set of parameters for jet reconstruction between the experiments Daniel Abercrombie**The Event**Daniel Abercrombie**Characterizing the W peak**Searching for stable mean and smallest fractional width 200 GeV < pT < 225 GeV Daniel Abercrombie**Comparing cone sizes**• Using the anti-kT algorithm gives the most conic shape and is resistant to soft radiation • Scanned through cone sizes from ΔR = 0.4 to ΔR = 0.8 with a resolution of 0.1 Daniel Abercrombie**Comparing cone sizes**• Jump in larger cones probably due pT cut for single jets Daniel Abercrombie**Comparing cone sizes**• ΔR = 0.4 gives narrowest width Daniel Abercrombie**Comparing cone sizes**• Reasonably constant responses from each cone size Daniel Abercrombie**Comparing cone sizes**• Again, ΔR = 0.4 gives the narrowest width Daniel Abercrombie**Comparing cone sizes**• Again, ΔR = 0.4 gives the narrowest width Daniel Abercrombie**Comparing algorithms**Daniel Abercrombie**Comparing algorithms**ΔR = 0.5 • Grooming keeps mass relatively constant compared to anti-kT Daniel Abercrombie**Comparing algorithms**ΔR = 0.5 • Trimming and filtering compete for best resolution Daniel Abercrombie**Comparing algorithms**ΔR = 0.5 • Pruning may be too aggressive at low pileup Daniel Abercrombie**Comparing algorithms**ΔR = 0.5 • Trimming and filtering compete for best resolution Daniel Abercrombie**Conclusions**• Smaller cone sizes give the best mass resolution with a reasonably small response • Pruning looks like it might be too aggressive • Current plots should be improved by finding ways to increase the efficiency of picking the correct jets Daniel Abercrombie**Future work**• Explore additional parameter space of the algorithms • Look at the effects of jet reconstruction onthe top quark mass • Work on selection cuts and parameters to increase the efficiency of selecting the correct jet Daniel Abercrombie**Thank you!**Daniel Abercrombie**Thank you!**Daniel Abercrombie**Backup Slides**Daniel Abercrombie**Selection criteria jets**• Events must have at least two b tagged jets and one isolated muon with pT > 10 GeV and |η| < 2.4 • Two jets with pT > 20 GeV and the highest combined secondary vertex values were selected as the b jets • Other jets were in the opposite hemisphere from the muon, MET, and b tagged jet closer to the muon i.e. Daniel Abercrombie**Selection criteria jets (cont.)**• Single jets were picked with the following cuts:p > 200 GeV; mass > 60 GeV; MET > 30 GeV • MET cut helps ensure boosted tops • If there were no single jets, the dijet system with the highest pTjets with a invariant mass of 30 GeV < m < 250 GeV is picked Daniel Abercrombie**Comparing algorithms**• Pruningtight: nsubjets=2, zcut=0.1, dcut factor=0.5, algo = CAloose: nsubjets=2, zcut=0.1, dcut factor=0.2, algo = CA • Filteringtight: rfilt=0.2, nfilt=3, algo = CA loose: rfilt=0.3, nfilt=3, algo = CA • Trimmingtight: rtrim=0.2, pTfrac=0.05, algo = CA loose: rtrim=0.2, pTfrac=0.03, algo = CA Daniel Abercrombie**Other measures of efficiency**ΔR = 0.5 • All of the lines for each algorithm fall well withinthe uncertainties Daniel Abercrombie**Other measures of efficiency**ΔR = 0.5 • All of the lines for each algorithm fall well withinthe uncertainties Daniel Abercrombie**Effects of PU**ΔR = 0.4 • Pileup decreases efficiency • This is more prominent using larger cone sizes Daniel Abercrombie**Effects of PU**ΔR = 0.5 • Pileup decreases efficiency • This is more prominent using larger cone sizes Daniel Abercrombie**Effects of PU**ΔR = 0.7 • Pileup decreases efficiency • This is more prominent using larger cone sizes Daniel Abercrombie**Effects of PU**ΔR = 0.9 • Pileup decreases efficiency • This is more prominent using larger cone sizes Daniel Abercrombie**PU jets simulation**Weighting: Daniel Abercrombie**PU jets simulation**NPU = 10 • Everything above 20 GeV can be mistakenfor a quark jet Daniel Abercrombie**PU jets simulation**NPU = 15 • Everything above 20 GeV can be mistakenfor a quark jet Daniel Abercrombie**PU jets simulation**NPU = 20 • Everything above 20 GeV can be mistakenfor a quark jet Daniel Abercrombie**PU jets simulation**NPU = 25 • Everything above 20 GeV can be mistakenfor a quark jet Daniel Abercrombie**PU jets simulation**NPU = 30 • Everything above 20 GeV can be mistakenfor a quark jet Daniel Abercrombie**PU jets simulation**NPU = 35 • Everything above 20 GeV can be mistakenfor a quark jet Daniel Abercrombie**PU jets simulation**NPU = 40 • Everything above 20 GeV can be mistakenfor a quark jet Daniel Abercrombie**ΔR = 0.3**Daniel Abercrombie**ΔR = 0.4**Daniel Abercrombie**ΔR = 0.5**Daniel Abercrombie**ΔR = 0.6**Daniel Abercrombie**ΔR = 0.7**Daniel Abercrombie**ΔR = 0.8**Daniel Abercrombie**ΔR = 0.9**Daniel Abercrombie**ΔR = 1.0**Daniel Abercrombie**ΔR = 0.7**175 GeV < pT < 200 GeV Daniel Abercrombie