Trigger & Analysis Avi Yagil UCSD

14-June-2007HCPSS - Triggers & AnalysisAvi Yagil 2 Table of Contents Introduction –Rates & cross sections –Beam Crossings –What do we trigger on? –Trigger Table (example) Trigger terminology –Trigger paths –Prerequisites –Volunteers –Overlaps Primary Data Sets Online streams –Why? How many? –Express stream Data flow overview Analysis –Physics signature –What is my trigger? –Where do I find the data? Experiment dependent Sample location & content –An aside: Data formats RAW, RECO, AOD, ESD, TAG… What do I need? What can I afford? Where is it? –Efficiency measurements backup triggers, samples –How fast can I run over my sample? Vertical and Horizontal skims An Example

14-June-2007HCPSS - Triggers & AnalysisAvi Yagil 3 Rates… Cross Section: σ(pp) = 70 mb Interaction Rate, R = 7x10 8 Hz Bunch Spacing:  t= 25 ns Physics Cross Sections: Inelastic: 109Hz W→l ν: 102Hz t t production: 10 Hz Higgs (100 GeV/c2): 0.1 Hz Higgs (600 GeV/c2): Hz 250 GeV ET Jets - 1kHz Rejection needed: 1:

14-June-2007HCPSS - Triggers & AnalysisAvi Yagil 4 Time to think? Bunch Spacing… Less time to think, MUCH more to think about…

14-June-2007HCPSS - Triggers & AnalysisAvi Yagil 5 From P. Sphicas, talk - i

14-June-2007HCPSS - Triggers & AnalysisAvi Yagil 6 From P. Sphicas, talk - ii

14-June-2007HCPSS - Triggers & AnalysisAvi Yagil 7 What do we trigger on? General considerations Basics: –Hadron colliders produce mostly low momentum hadrons –Most interesting Physics has signatures involving large transverse energy (E T ) particles. ==> Require high E T on reconstructed particles Basic objects used for trigger: –Electrons, Photons, Muons, Jets, Missing Et Approximate thresholds and associated rates: –Single muon with P T >20 GeV - 10kHz Double muon P T >6 GeV - 1kHz –Single em cluster with E T >30 GeV kHz Double em cluster with E T >20 GeV - 5 kHz –Single jet with E T >300 GeV kHz The more complexity one adds to the a signature - the lower the rate, and hence the required threshold The more complex the signature is - the harder it is to understand…

14-June-2007HCPSS - Triggers & AnalysisAvi Yagil 8 HLT Trigger Table - Example (CMS)

14-June-2007HCPSS - Triggers & AnalysisAvi Yagil 9 Evolution of Ana goals, implications… Detector commissioning –Timing –Cabling –… Comish. Low level reco. –Val. hits, segments, clusters –Calibrate –Noise, 0-suppression Comish. Object reco. –Establish e, m, jet… IDs –Define basic eff. - Z signal –Measure rejection –Isolation! Counting experiments Cross section measurements Raw Data Latch-all (no 0-suppression) Basic detector DQM software Local/global daq Raw and RecHits Local geometry, DB access Low level reconstruction software Establish 0-suppression asap! Raw, RecHits and Reco Detector geometry, DB, Ca/Al… Full reconstruction software (HLT) Basic trigger, Access to data Absolute efficiencies (tracking…), MC scale factors Luminosity

14-June-2007HCPSS - Triggers & AnalysisAvi Yagil 10 Trigger Path The “name” of the sequence of requirements that resulted in an event being recorded: –L1 accept –HLT confirmation Object type(s) and threshold(s), cut(s) (things like: emu_20_20_iso_met_50 or maybe hipt_emu_met) There has to be a bit for each one. Defines how events are classified (immutably!) –Implication: complete exploration of all L1 accepts

14-June-2007HCPSS - Triggers & AnalysisAvi Yagil 11 Pre-requisites, Volunteers Pre-Requisite: Only muons that have a L1 accept are pursued in the HLT. Moreover, only that region is reconstructed. Volunteer: A muon “found” in the HLT, without a corresponding L1 accept cannot result in a trigger –this cannot happen if we do “seeded” (on L1 muon track) reconstruction in HLT, but can happen if we do global reconstruction.

14-June-2007HCPSS - Triggers & AnalysisAvi Yagil 12 Overlaps A frequently asked question is: –What is the overlap between Primary Data Sets? Recall that the overlap between data sets is a result of the overlap between trigger paths. How big is it? How big should it be? Up front overlap - express stream. –An experiment decides how big it is (~10%) –Completely controlled Additional duplication occurs due to Physics but is very small in comparison. An e-mu-met event will (hopefully) go to three data sets and we want them to! But (sadly) there are few of these… –Can have huge overlaps - need good design of trigger table One can have as big an overlap as one can afford.

14-June-2007HCPSS - Triggers & AnalysisAvi Yagil 13 Primary Data Sets It is easy to foresee about 50 primary datasets to be identified during the HLT processing, each following a strict trigger path (L1 and the appropriate HLT confirmation of it). –How many will be needed? –There is danger in too many, and also in too few… –Serious Physics Coordination issue! As a Data Management artifact in the Online farm, these 50 primary datasets may be grouped into about 10 streams constructed to be roughly of similar sizes and contain more or less related primary datasets. These streams have no (physics) significance outside of the Online-to-Offline data management context.

14-June-2007HCPSS - Triggers & AnalysisAvi Yagil 14 Streams (online, intermediate) One can imagine the following example of streams definition: –Jet data stream –electron/photon –Muon, tau/MET –calibration –min bias –… Where for example the ele/photon stream will contain the primary datasets for inclusive electron as well as the di-electron triggers of various thresholds (some may be pre-scaled) and the closely related photon triggers. These primary datasets should contain back-up triggers (primary datasets) to assist in understanding the efficiency and rejection of the main ones (they will be usually looser and pre-scaled).

14-June-2007HCPSS - Triggers & AnalysisAvi Yagil 15 End-to-End example Basic characteristic: –Low production rate signal –Large background –Many, small channels to assemble Search for top quark –Pick a signature: (di-leptons, lep+jets…) pp-->tt+X and tt-->WbWb Where: W-->e  W-->  Final States: -lepton pair, two b jets - lepton, 2 b-jets, 2 q-jets Why limit oneself to only leptonic W decays? –Why not look at all W and Z decays? (leptonic rates very low) –… >> It’s the rates! Analysis steps: – Find corresponding triggers: Inclusive electron, muon Di-electron, muon Maybe others (bb+met), but much harder (why?) –Define the samples to use: W & Z samples (to e and mu) –Which level of information is needed? 4 vectors? RAW data? Something in between?? –Where is it to be found? –How big is it? How long does it take to run over it? –Can it be “reduced”?

14-June-2007HCPSS - Triggers & AnalysisAvi Yagil 16 Notes from the search for top Triggers & Data sets used Relied primarily on inclusive electron and inclusive muon triggers Many backup triggers needed: –Various inclusive jet samples for jet corrections –Gamma-jet sample for E-scale –W-notrack trigger for tracking efficiency –Jet50 sample for b-tagging MC scale factor –Many many more A “family” of analyses Three main classes –Di-lepton –Lepton+jets –All hadronic All predicated on the basic trigger path, or primary data set. Finer split within each –Electron, Muon or jets as “anchor leg” (trigger requirement) – additional features (e.g. vertex b-tagging, SLT…)

14-June-2007HCPSS - Triggers & AnalysisAvi Yagil 17 Sample definitions: Inclusive Electron/Muon Samples

14-June-2007HCPSS - Triggers & AnalysisAvi Yagil 18 W selection

14-June-2007HCPSS - Triggers & AnalysisAvi Yagil 19 Jets and Met in top events

14-June-2007HCPSS - Triggers & AnalysisAvi Yagil 20 b jets from top decays

14-June-2007HCPSS - Triggers & AnalysisAvi Yagil 21 “Soft” leptons in top decays

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