Diffractive Dijet Production: Update on analysis issues Hardeep Bansil Birmingham Weekly ATLAS Meeting 22/09/2011

Contents Updates on issues Next steps 2

Analysis Bottleneck Broken! Running over 2010 periods A&B, ∫L dt = 8.75 nb -1, 75mil events Grid running fast enough (only some slow sites) Running locally over ntuples now significantly faster – Using SFrame (thanks Simon!) Adds additional step in merging files – Requires more initial preparation – Worked only with Fedora ROOT, not general 5.26 ROOT ver. – Large files means this takes a day – has skimming of runs by requiring high pT jets helped in any way? – Still faster than previous method 3 Running jobs on grid  get ntuples (1/1.5 days) Merge root files for each run (1 day) Running over ntuples on batch server to get useful histograms (20 minutes – prev 2+ days) Run over histos to get final plots (5 minutes)

Monte Carlo Generators Request to get official Pomwig Monte Carlo production done – Need to show results at Soft QCD Working Group meeting first before this can be done – Hopefully soon Rapgap possible – Still waiting on Rivet authors to get this running – Issue with “incompatible beams” Set up independent version of Pomwig at CERN – Files for this given by Radek Zlebcik 4

AntiKt η confusion Analysis uses both AntiKt R=0.4 and R=0.6 jets Using MinBias data sample, ask for forward gap (∆η F >2.0) with jet 1 > 26 GeV, jet 2 > 20 GeV, jets not within gap AntiKt6 - before and after gap cuts, see a (approximately) symmetric η distribution for jet 1, similar for jet 2 AntiKt4 - see a big spike between 0<η<1 in both cases, after gap cuts gets even worse  INVESTIGATE! 5 AntiKt4 - After forward gap cuts AntiKt6 - After forward gap cuts

AntiKt η confusion Thanks to SFrame, could determine that it was not a bug eLog says issue comes from run , problem in TILE modules LBA47,48 (0.050<η<0.950, <φ<-1.624) – Does not show up in DQ defects database, maybe in old system? Look at φ distribution for events in where jets have fallen in the 0<η<1 region – More obvious in AKt4 but still a number of candidates in Akt6 6 AntiKt4 - Before forward gap cuts AntiKt6 - Before forward gap cuts Run

AntiKt η confusion Thanks to SFrame, could determine that it was not a bug Issue comes from run , problem in TILE modules LBA47,48 (0.050<η<0.950, <φ<-1.624) Look at Et distribution for events in where jets have fallen in the 0<η<1 region – Not limited to any particular Et range 7 AntiKt4 - Before forward gap cuts AntiKt6 - Before forward gap cuts Run

AntiKt η with ATLANTIS In an otherwise empty event, the problem modules create a large energy deposit in TILE In AntiKt4 this can make 2 high Et jets passing the cuts, but with a larger cone size it will only create 1 jet Note the large amount of missing Et required to balance the event 8 AntiKt4 AntiKt6 Thanks Juergen!

AntiKt η with ATLANTIS Similar to the last event but now the secondary AntiKt4 jet is covered almost 100% by the primary jet Energy deposits remain in the same place Who to speak to about this? 9 AntiKt4 AntiKt6

AntiKt η with ATLANTIS Amongst the noisy events, there are some genuine candidates passing cuts Unfortunately all of them are in the same LBs as noisy events Only choice is to remove run from analysis ∫L dt ≈ 20 μb -1 so it should only make a small dent in total (8 nb -1 ) 10

Next steps Make plots Present them at Soft QCD Get official Pomwig samples Speak to someone about jet issues in run