Status & results of PFA studies at U. Iowa Mat Charles Usha Mallik 1
Event Type e + e − → Z 1 Z 2 CM energy: 500 GeV νν (light jets) qq (light jets) • This produces jets that have realistic energies, but without excessive overlap. • No confusion from jet-finding when calculating dijet mass. 2
Barrel angle cuts • For e + e − → ZZ, Z → light jets, jets tend to be produced at small angles. • In most events, a lot of energy goes down the beampipe and resolution is lousy even with perfect pattern recognition. • So we will look only at barrel events, defined by one of: • Thrust of reconstructed jet has |cos ϑ | < 0.8 • Generated quark has |cos ϑ | < 0.8 in truth info • Turns out not to make a big difference which we use. 3
acme0605 Event mass in barrel Width for Entries per 1 GeV bin physics: 6.9 GeV 100 Below Z 80 mass ⇒ bias 60 : 85.7482524 µ 90 RMS : 6.91099016 40 90 20 0 50 60 70 80 90 100 110 120 130 2 Dijet mass residual (GeV/c ) 4
acme0605 Mass residuals in barrel Width for algorithm Entries per 1 GeV bin development: 6.1 GeV 100 80 60 : -5.23752828 µ 90 RMS : 6.12522086 90 40 20 0 -40 -30 -20 -10 0 10 20 30 40 2 Dijet mass residual (GeV/c ) 5
acme0605 Mass residuals in barrel (alternate angle cut) Entries per 1 GeV bin 300 250 200 : -5.14835757 µ 90 150 RMS : 6.09970774 90 100 50 0 -40 -30 -20 -10 0 10 20 30 40 2 Dijet mass residual (GeV/c ) Almost no change w.r.t. nominal barrel cut 6
acme0605_steel_scint Event mass in barrel 120 Width for Entries per 1 GeV bin physics: 7.3 GeV 100 Bias even worse 80 : 83.7073796 µ 60 90 RMS : 7.27732482 90 40 20 0 50 60 70 80 90 100 110 120 130 2 Dijet mass (GeV/c ) 7
acme0605_steel_scint Mass residuals in barrel Width for algorithm 140 Entries per 1 GeV bin development: 6.5 GeV 120 100 80 : -7.35414919 µ 90 60 RMS : 6.52988089 90 40 20 0 -40 -30 -20 -10 0 10 20 30 40 2 Dijet mass residual (GeV/c ) 8
acme0605_w_rpc Event mass in barrel Entries per 1 GeV bin Width for physics: 6.6 GeV 100 80 Bias moderate : 87.349175 µ 60 90 RMS : 6.64252395 90 40 20 0 50 60 70 80 90 100 110 120 130 2 Dijet mass (GeV/c ) 9
acme0605_w_rpc Mass residuals in barrel Entries per 1 GeV bin Width for algorithm 120 development: 5.7 GeV 100 80 : -3.82898492 µ 90 60 RMS : 5.69404332 90 40 20 0 -40 -30 -20 -10 0 10 20 30 40 2 Dijet mass residual (GeV/c ) 10
acme0605_steel_rpc Event mass in barrel Width for Entries per 1 GeV bin 120 physics: 6.8 GeV 100 Bias smaller 80 : 88.3217593 µ 90 60 RMS : 6.80778351 90 40 20 0 50 60 70 80 90 100 110 120 130 2 Dijet mass (GeV/c ) 11
acme0605_steel_rpc Mass residuals in barrel Width for algorithm Entries per 1 GeV bin 140 development: 5.9 GeV 120 100 : -2.55145842 80 µ 90 RMS : 5.87387943 60 90 40 20 0 -40 -30 -20 -10 0 10 20 30 40 2 Dijet mass residual (GeV/c ) 12
Summary RMS 90 of mass RMS 90 of Design Bias (including Γ ) residuals (no Γ ) 6.9 GeV 6.1 GeV − 5.2 GeV acme0605 [w/scint] 7.3 GeV 6.5 GeV − 7.4 GeV acme0605_steel_scint 6.6 GeV 5.7 GeV − 3.8 GeV acme0605_w_rpc 6.8 GeV 5.9 GeV − 2.6 GeV acme0605_steel_rpc For this real (i.e. confused) PFA: • RPCs give noticeably better resolution and smaller bias than scintillators • Tungsten gives somewhat better resolution than steel 13
Next steps • Code is in CVS (but considered unstable) • org.lcsim.contrib.uiowa.NonTrivialPFA • org.lcsim.contrib.uiowa.NonTrivialPFAWrapper • org.lcsim.contrib.uiowa.NonTrivialPFAWrite • Work with Ron to feed the PFA output into his analysis tools (we are close!) • Look again at the origin of the bias • For energy sums it was an excess of (neutral → charged) confusion over (charged → neutral)... is that still true for the dijet mass? • Algorithm development, testing of new components • Move on to next event type (4 jets) 14
Recommend
More recommend
