Transcript Slide 1
SUSY in DC1 Davide Costanzo Lawrence Berkeley Laboratory [email protected] Davide Costanzo Feb24th 2004. ATLAS tutorial on SUSY Introduction • ATLAS physics has been carefully studied in the past ~ potential ~ (Physics TDR--1999, fortran based simulation/reconstruction) • Effort to develop and test the production software. Data Challenges: – DC1 finished a few months ago (validation of the new OO reconstruction) – DC2 to start in spring 2004 (validation of the new OO simulation) – DC3 to end in 2005 ATLAS Physics readiness report • SUSY Studies with DC1 to repeat with full simulation one of the cases studied with the fast simulation – – – – More “realistic” way of doing analysis Reconstruction of fully simulated events Some Physics plots ATL-COM-PHYS-2003-55 2 Davide Costanzo Feb24th 2004. ATLAS tutorial on SUSY Data Challenge 1 • Fortran/Geant3 based simulation • OO Reconstruction (C++), comparison with the Physics TDR • Physics workshop last May in Athens • Physicists/Users getting used to the new framework (athena) • Reconstruction task-force, to identify the points which need improvement • Number of physicist contributing to the ATLAS software is significantly increasing! 3 ATLAS DC1 Phase 1 : July-August 2002 4 Contribution to the overall CPU-time (%) per country Feb24th 2004. ATLAS tutorial on SUSY GEANT3 SIMULATION 3200 CPU‘s 110 kSI95 1,41% 71000 CPU days 0,02% Davide Costanzo 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 10,92% 14,33% Australia Austria Canada 3,99% CERN Czech Republic 1,89% France 4,33% Germany Israel 3,15% Italy 2,22% Japan Nordic Russia 10,72% Spain Taiwan 4,94% UK 2,36% USA 1 2 3 4 5 6 7 39 Institutes in 18 Countries grid tools used at 11 sites 28,66% 0,01% 9,59% 8 9 10 1,46% 11 12 5*10*7 events generated 1*10*7 events simulated 3*10*7 single particles 30 Tbytes 35 000 files 13 14 15 16 The SUSY data challenge ~~ ~~ ~~ Davide Costanzo Feb24th 2004. ATLAS tutorial on SUSY Herwig: ppgg, qg, qq (MSUSY≈0.6TeV) m0 = 100 GeV m1/2 = 300 GeV A0 = -300 GeV tan b = 6 sgn m = + Point chosen similar to SUGRA point 5 (Physics TDR), Adjusted to have mH=115GeV 100K events simulated with Geant3 (just 1% of the all DC production) 1 Tbyte of data Simulation ~30m/event (5 sites + US Grid) Reconstruction ~ 1m/event (LBL) 100K events corresponding to 5.13fb-1, (Something that we can realistically/hopefully have at the end of 2007…) 5 SUSY Physics with Full Simulation Davide Costanzo Feb24th 2004. ATLAS tutorial on SUSY • Selection cuts (used for the Physics TDR): – – – ≥ 4 jets with Et > 100,50,50,50 GeV Meff > 800 GeV Et > max (100 GeV, 0.2 Meff) • Expect negligible SM background, so just show SUSY distribution. Typical for SUSY: “main background from SUSY itself”. No SM Background events simulated for this study. • Very good stress-test for the ATLAS simulation and reconstruction. SUSY events have: – – – – • Lots of Jets and Missing Et B-jets Charged leptons (e, m) Tau Leptons Getting ready to do Physics in a more “realistic” way (w.r.t. fast simulation) – – – Big (disk space) data sets Long processing time Several collaborators, over different time zones Look at the reconstruction tools and at some Physics plots that can be made using these tools 6 Jet Reconstruction in SUSY Events Davide Costanzo Feb24th 2004. ATLAS tutorial on SUSY ~~ ~~ ~~ Herwig: ppgg, qg, qq (MSUSY≈0.6TeV) • Simplest test g distribution of Truth and Detector jets as function of h. • Some Effects evident: – Barrel-Endcap Crack – Loss of Detector jets in Endcap-Forward crack – Shower leakage at large h . PT > 25, 50, 100 GeV ―Truth ―Calo 7 Jet Reconstruction (1) Davide Costanzo Feb24th 2004. ATLAS tutorial on SUSY Reconstructed jet vs. True jet. Cone Algorithm KT Algorithm 8 Davide Costanzo Linearity Resolution Cone Algorithm KT Algorithm s(ET)/ET th -1 DE Feb24 ATLAS tutorial on SUSY T/ET2004. Jet Reconstruction (2) 65 %/√E 5% 9 Davide Costanzo Feb24th 2004. ATLAS tutorial on SUSY Missing ET -- Good agreement with TDR for SET<1 TeV -- For increasing pT di-jets points higher than the expected curve (same effect see in DiJet events) The Effect of El. Noise/ Pile-up needs more study for ET and Jet Reconstruction 10 Meff from Full Simulation Davide Costanzo Feb24th 2004. ATLAS tutorial on SUSY Meff = Pt,1 + Pt,2 + Pt,3 + Pt,4 + ET Jet + Missing Et sample 5 fb-1 are enough to spot a statistically significant signal SM Background is from top, QCD (fast simulation) 11 ~ qR Mass Measurement Feb24th 2004. ATLAS tutorial on SUSY q p ~ qR p ~ qR 0 q c1 c0 1 NEW: Not done with fast simulation. Davide Costanzo Select Events with two jets (>100GeV) and Missing ET (>200 GeV) Define “s-tranverse mass” as: mT22 = min [max{mT2(pTj(1),qTc(1);mc),mT2(pTj(2),qTc(2);mc)}] qTc(1)+qTc(2)=ETmiss Expected: 611GeV Syst: ~5% 12 Electrons Reconstruction Davide Costanzo Fake e/j is ~ 10-3. Good for SUSY. (not using the TR information) Full: iPatRex Dash: xKalman Pseudorapidity Efficiency Efficiency Feb24th 2004. ATLAS tutorial on SUSY Energy compared to closest MC electron in Dr = DhDf ET (GeV) 13 Davide Costanzo Feb24th 2004. ATLAS tutorial on SUSY Muon Reconstruction Muon Reconstruction gives excellent results. Better than 90% overall acceptance Dip in acceptance at h=0 due to hole for services. (MuonBox gives results similar to Moore) Black: Moore Blue: MuId Standalone Red: MuId InDet comb. 14 Mass Edge Davide Costanzo Feb24th 2004. ATLAS tutorial on SUSY ~ qL M(c2)-M(c1) ≈ 105 GeV ~ 0 q c2 l ~ l Apply corrections for electron and muon energy scale and efficiency (previous plots) Flavor Subtracted mass to remove the contribution from uncorrelated SUSY decays: e+e- + m+m- - e+m- - e-m+ ~ c0 1 l 15 Mass measurements (leptons + Jets) Davide Costanzo Feb24th 2004. ATLAS tutorial on SUSY Decay chains like: ~ qL ~ 0 q c2 l Smaller (llq) mass 16 ~ l ~ c0 1 l Larger (llq) mass ? Not present In fast Sim. Efficiency Vertex detector can not cleanly identify t l nn Rely on hadronic decays. Narrow, 1-prong jets. Lots of QCD background: • 1 Track in Jet with pT>2GeV • ET,had > 0.1 ET • Likelihood Lt, for the shower shape Davide Costanzo Feb24th 2004. ATLAS tutorial on SUSY Tau Reconstruction Likelihood ht 17 Di-Tau invariant mass Template: From MC Davide Costanzo Feb24th 2004. ATLAS tutorial on SUSY For t+t- use all MC c20t~1 t to find expected Mtt,vis distribution Fit shape to reconstructed t+t- + t-t+ - t+t+ - t-t- Fit gives 103.5 ± 4.9 GeV. Consistent with expected 98.3 GeV tt visible Invariant mass 18 Davide Costanzo Feb24th 2004. ATLAS tutorial on SUSY B-jet tagging • • • • Impact parameter of tracks combined in likelihood ratio Both transverse and Z impact parameter used Severe requirements on track quality (e.g. innermost pixel cluster is unambiguous) Tagging possible in SUSY events Open: Hbb Full: SUSY 19 Conclusions Davide Costanzo Feb24th 2004. ATLAS tutorial on SUSY • Reconstruction and Analysis of fully simulated SUSY events for the first Data Challenge has been successful • Useful to conduct the analysis in a more “realistic” way (and to debug the Reconstruction software) • Results are in good agreement with previous fast simulation studies • Some problems still to be understood: low tail in the m(llq) distribution, b-tagging • Did not use fully simulated background (top) • Calorimeter noise and pile-up to be treated better in DC2 • Great work of a wide-spread collaboration • Look forward to DC2 (and to the first 5.13pb-1 of data!) 20