Motivations for a L1 Track Trigger

Transcription

1 Motivations for a L1 Track Trigger Véronique Boisvert, RHUL TDAQ week Rome May 2009 Thanks to: Simon G., Alan W., Monika W., Stefan T., Fred W., Pedro T., Teresa F., Michael B.

2 Motivation for the Motivation Decision to implement a L1 Track Trigger is not trivial Technologically not straightforward Impact on various systems: L1Calo/L1Muon Tracker (timescale quite critical) Should be physics motivated Also not trivial Basic question number 1 is: To do the physics that we want to do at the SLHC, how much do we gain/need a L1Track Trigger to have appropriate L1 lepton triggers? Appropriate = In terms of rate and efficiency (thresholds) CMS needs a L1 Track Trigger Basic question number 2: If we think a L1 Track Trigger is feasible, should we take the risk of not having one? Veronique Boisvert, RHUL 2

3 Physics Motivations for SLHC Studies done in 2002 to kick start SLHC Summary in hep-ph/ : Physics potential and experimental challenges of the LHC luminosity upgrade Main topics: 1. Improvement of the accuracy in the determination of SM parameters (TGC, QGC, Higgs couplings) 2. Improvement of the accuracy in the determination of parameters of New Physics possibly discovered at the LHC (e.g. sparticle spectroscopy, tanb measurements) 3. Extension of the discovery reach in the high-mass region (e.g. quark compositeness, new heavy gauge bosons, etc) 4. Extension of the sensitivity to rare processes (e.g. FCNC top decays, Higgspair production, multi gauge boson production) Veronique Boisvert, RHUL 3

4 Examples relevant to L1Track Trigger 1. Multiple Gauge boson production Studies assume: 90% id efficiency for each lepton η l <2.5, P T l >20GeV 2. H µµ: LHC: not better than 3.5σ Study assumes: 90% id efficiency for each muon η l <2.5, P T l >20GeV Veronique Boisvert, RHUL 4

5 Examples relevant to L1Track Trigger 3. Top FCNC t qγ: 1 iso. γ E T >75GeV, η <2.5 1 l p T >20GeV, η <2.5 Jets t qg: 1 l p T >20GeV, η <2.5 Jets t qz: 3 l p T >20GeV, η <2.5 Jets 4. SUSY: Point K M eff = E T miss + Σ E Tjet + Σ E Tlepton lepton E T >15GeV Veronique Boisvert, RHUL 5

6 Examples relevant to L1Track Trigger 5. ED in RS model G ll LHC 10fb -1 LHC 100fb -1 SLHC 1000fb -1 Conclusions from examples: 1. Most signatures require >1 leptons 2. Offline p T cut is always >20GeV, η <2.5 Don t know dependence of results vs p T, η cut L1 Track Trigger will have to be both barrel and endcap 3. Total efficiency is assumed to be 90% Don t know dependence of results vs efficiency 4. A lot of results are at the limit of what the SLHC can offer E.g. need 6000fb-1 to achieve 5σ Veronique Boisvert, RHUL 6

7 Trigger Strategy at SLHC Very high p T for discovery physics Low p T thresholds but then use multi-objects or exclusive (1 el + MET + N jets) triggers Can we achieve this? What impact does this have on physics goals? Prescaled control/calibration triggers From scaling of L1 TDR, does not take into account full pile-up or cavern background Veronique Boisvert, RHUL 7

8 L1 Calo SLHC L1 will have longer latency Foreseen to have significant improvements compared to current system How much? Enough to allow ok rate at low p T thresholds? Could use L2 algorithms to get upper limit on performance E.g. use T2Calo as L1Calo T2Calo runs off ROI, but could hack this Also, remember that L1Calo simulation can run off ATLFAST II Veronique Boisvert, RHUL 8

9 L1 Muon One of the reasons for CMS getting L1 Track trigger is flatness of L1 muon rate See e.g. arxiv: Turns out ATLAS is also pretty flat But feasible solutions related with adding layer to Muon Note that this is meant to address how the rate should be falling with p T thresholds But ideally we don t want to raise those! Absolute rate will decrease by how much? Kawamoto, 13/11/08 Mikenberg, 26/02/09 Veronique Boisvert, RHUL 9

10 How to proceed further If want to answer basic question: To do the physics that we want to do at the SLHC, how much do we gain/need a L1Track Trigger to have appropriate L1 lepton triggers? Ideal world: full simulation, full 400 pile-up, upgraded ID, upgraded L1Calo/L1 Muon simulation Get Rates/Turn-on curves vs p T thresholds See how much gain/need L1 Track trigger Need answer within 6-9 months Impossible to get this! Need approximations (which ones?) and then extrapolate Inherent uncertainties in all this What do we have now? Veronique Boisvert, RHUL 10

11 L1 Rates Estimates 2x10 33 cm -2 s -1 Detector Paper Detector Paper Hep-ph/ SLHC estimates (10 35 ) EM55I 20 2EM30I 5 MU MU20 few Inclusive e Inclusive e e/γ pair e/γ pair L1 TDR Veronique Boisvert, RHUL 11

12 L1 Rates Estimates Numbers from Rate Group: Using or 15.0 (Hz) TeV TeV TeV 1032+PU 14 TeV /1 3/2 4/2 L1_EM13I L1_EM L1_EM18I L1_EM23I L1_2EM L1_2EM13I L1_2EM L1_MU L1_MU L1_2MU L1_2MU L1_2MU Veronique Boisvert, RHUL 12

13 L1 Rates Estimates Unfortunately, impossible to extrapolate to from these numbers: Growth term is Highly nonlinear Trigger dependent Pile-up dependent E.g. Do the e/γ pair rates include the case of 2 single EM from different pp interactions happening in the same bunch crossing? Remember: In 100 min bias events: 7 particles with p T >5 GeV, 0.6 particles with p T >10GeV Veronique Boisvert, RHUL 13

14 Trigger Efficiencies HLT TDR At 2x10 33 : For e p T >25GeV, EF:80% x L1:95% x ID eff: 98% (?) = 74% vs 90% assumed by physics studies More recent numbers: use Z ee for T&P method E.g. e25i_tight for SUSY: 93% x ID eff: 98% = 91% e25i_tight, 14TeV, no pile-up Tamsett, 5/2/09 Veronique Boisvert, RHUL 14

15 Trigger Efficiencies Need multi-object trigger efficiency Not a lot of work on this so far E.g. to get 2e5 trigger efficiency use T&P with J/ ψ using e5 trigger More exclusive triggers: Trigger simulation Per object trigger efficiency Does the squaring approximation works? 90%^2 = 80% Tuan, 5/2/09 Begel, 5/2/09 Veronique Boisvert, RHUL 15

16 Conclusions We do not have the full set of tools to answer satisfactorily whether L1 Track Trigger is really needed or how much gain it could provide Not least of which: data experience! Yet decision is needed soon Veronique Boisvert, RHUL 16

17 To go further 1. Need better feel for possible L1Calo/L1Muon improvement (L1 rate) Run T2Calo on current layout but high lumi/pile-up? Run a modified L1Calo sim using ATLFAST II (with PU)? L1Muon? Probably custom rate determination 2. Need trigger efficiencies studies for interesting processes Di-electron, di-muon triggers Exclusive triggers Performance vs pile-up Use Current full sim samples, truth, check with PU would be nice 3. Might be useful to revisit a few SLHC analysis examples to get a feel for performance vs lepton efficiency Veronique Boisvert, RHUL 17