1 / 14

More on Trigger, Retention, Efficiency with the Minimal Layout S. Blusk Nov 4, 2009

More on Trigger, Retention, Efficiency with the Minimal Layout S. Blusk Nov 4, 2009. Introduction. Goal is come up with a sensible trigger strategy that can be implemented when we have a new detector description and reconstruction.

kalia-fulton
Download Presentation

More on Trigger, Retention, Efficiency with the Minimal Layout S. Blusk Nov 4, 2009

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. More on Trigger,Retention, Efficiency withthe Minimal LayoutS. BluskNov 4, 2009

  2. Introduction • Goal is come up with a sensible trigger strategy that can be implemented when we have a new detector description andreconstruction. • Victor has shown with a various set of selection requirements, he can ~double the TRIGGER efficiency in a few channels. • The signal efficiencies are evaluated for offline selected events.(more on this later)

  3. Intro - 2 • Implement Victor’s cuts, except • I use ‘Offline tracks’: Expect lower ghost rate in upgraded trigger than in current HLT. Assume we can get ‘offline’ quality, hope for better..(lower ghosts) • Assume comparable slope resolution between Velo and upgraded Velo. • Degrade pT resolution by smearing the reconstructed pT bys(1/pT)/(1/pT)=(15.0 - 0.76pT + 0.86pT2)%, pT in GeV • I have not included L0 CAL trigger (pT>2 GeV in CAL), could be used to throttle (but maybe tracking info is better ?) • Look at efficiencies and retention rates vs Luminosity.DC06 vs MinLayout. V. CocoLHCb-INT-2009-008 CAL cut rejects ~ 50%of MB at 1e33..

  4. Trigger Flow (for results in this talk) • Select VELO tracks with IP to nearest vertex > 120 mm (N1) • Get pT of tracks passing #1, cut on pT>1 GeV and IPS>3.0 (N2) • Form N2(N2-1) pairs and require: • DOCA < 80 mm • 2.0 < (Zsv-Zpv) < 100 mm, Rsv<5.8 mm • pT(L)>1.25 GeV, pT(c)> 1.0 GeV • Require polar angle q >23 mrad, both tracks • Point < 0.3 (see last talk for explanation of this cut) • Track c2/DOF < 4.5 If any 2-body combination passes all these cuts, I call this a “triggered event”. This is meant to imply that the event or candidate is passed on to a higher-level trigger that looks for specific exclusive or inclusive decays. I can then ask & answer: - Composition of triggered events, b, c, or u,d,s,g…? - Was the event ‘triggered’ by a 2-body in which both tracks were MC matched? - How often do ghost track pairs lead to a trigger (with no real track pairs) ?

  5. MC Samples • DC06 – Bsff, Offline Selected Eventsat various L • MinBias and Bsff from “Minimal Layout” from recent MC Production, also at several L values. • Thanks Tomasz!

  6. Track Multiplicity in VELO – Minimal Layout 2e32 5e32 10e32 20e32 Yes, we do seeincreased multiplicityas expected All Mean #’s: 43, 53, 74, 110 MC Matched Mean #’s: 4.8, 8.3, 19.5, 69.3 NOT MC Matched

  7. pT Resolution How does a ~15-20% pT resolution impact the fraction of events passing the trigger? Evaluate using “Minimal Layout” pT smearing s(1/pT)/(1/pT)=(15.0 - 0.76pT + 0.86pT2)%, • At 1e33, about a factor of 500 rejection: 30 MHz  ~50 kHz • Victor obtained ~30 kHz, but I do not have CAL pT > 2 GeV (~50% eff, see backup) • ~90% of the events passing are either b or c, not light ! Negligible impact of pT resolution on trigger efficiency for Bsff as well…

  8. Trigger efficiencies in % this analysis (no CAL Cut)Current LHCb Detector using new trigger scheme,except use nominal pT Bsff Trigger Efficiencies on Offline selected events(DC06) L = 5e32 10e32 20e32 -- factors out the efficiency in reconstructing the event… more in a bit on this. V. CocoLHCb-INT-2009-008 1st number: Any “di-hadron trigger” 2nd number: All daughters MC matched to recon. long tracks 47/43 58/53 40/30 Probably due to B daughters accidentallypointing to a PV • Input files: Offline Selected Bsff events • 5e32: /castor/cern.ch/user/d/dijkstra/Selections-Upgrade/phiphi-lum5.dst • 10e32: /castor/cern.ch/user/d/dijkstra/Selections-Upgrade/phiphi-lum10.dst • 20e32: /castor/cern.ch/user/d/dijkstra/Selections-Upgrade/phiphi-lum20.dst

  9. Bs ff “Actual” Efficiency Run over “Minimal Layout” Events. They only have DecProdCut applied, which is ~20% efficient for all 4 daughters to be in LHCb acceptance. 1K events, so stat error ~ 1% (on #’s in first 3 rows) Without and with VeloTT track req. DC06 Offline Selected MinimalLayout Most of loss in efficiency trigger? Vertex tracks “accidentally” pointing toa PV? * Assumes an “offline” analysis selection efficiency of 65% (see backup); will try and apply offline selection cuts Efficiency in LHCb light TDR is ~0.5% (esel listed as 39% there) If want to assume this efficiency, reduce efficiencies in bottom row by 40%

  10. MinBias Rejection Comparison vs Lumi Minimal Layout • Rejection scales roughly with the #inelastic collisions / crossing… very good! • Must be reconstructing PVs efficiently & rejecting primary tracks… good • But fraction of non-empty x-ing increasing also.. • Probability of getting b or cper crossing increases as expected: • % b per X-ing: 1.3  2  3.2  7 % • % c per X-ing: XX  15  23.2  40 % • Trigger still dominated by heavy flavor, even at highest lumi… very good! • But lots of it !! • CAL pT cut can be used as a throttle, but should explore track-based selections..

  11. Summary • Looking at offline selected events, my #’s consistent with Victors • ~15-20% pT resolution does not appear to be a problem • Looked at “Minimal Layout” for Bsff: • Lose about a factor of 2 in trigger efficiency in going from 2e32  2e33 • In Minimum Bias • Rate of events passing trigger increases ~ as expected, from10 kHz at 2e32 to 150 kHz at 2e33) • Most triggers are from real heavy flavor, not light quarks or g. • Other cuts to reduce the rate should be explored, ECAL ET cut, or/and other tracking cuts • The big issue is not really whether we can maintain the efficiency, it’s the CPU cost. • If upgraded detector provides comparable tracking performance to current offline tracks, ghosts do not swamp this first level trigger. • It would be nice to have “offline-selected” samples from the MinLayout, and to know what the efficiencies were for those selections. • To do’s: • Look at impact on other signal samples • Explore other cuts to reduce MinBias rate

  12. V. Coco, LHCb WeekFeb 26, 2009 CAL cut removes ~50% of min bias events at 1e33. But, the reduction at Step 1 will likely remove more events than after Step 15(since after Step 15, one is guaranteed to have 2 tracks with pT>1.0, 1.25 GeV) Anyhow, 50% probably still not too unreasonable.

  13. Bsff Offline Selectionsfrom LHCb-2007-047 • Pre-selection: • IPS > 2 to PV • DLL(K-p) > -2 • M(KK)<1050 MeV • Vertex c2(f)<100 • Vertex c2(Bs)<36 • 4 < M(Bs) < 7 GeV • Mostly loose cuts, but the PID goes as e4 • Taking 95%/kaon epid~80% Analysis selection The efficiency of these offline criteria are ~ 4663/5843 ~ 80% So, offline selections + PID are ~ 65% efficient

More Related