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Mark Thomson University of Cambridge

Timing Status. Mark Thomson University of Cambridge. ILD Time-stamping. At last meeting proposed:. Ideally routinely overlay 110 BXs or 60 BXs if not feasible driven by W HCAL timing. Physics event at BX number 10 allow for main calorimeter contributions from previous BXs.

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Mark Thomson University of Cambridge

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  1. Timing Status Mark Thomson University of Cambridge

  2. ILD Time-stamping At last meeting proposed: • Ideally routinely overlay 110 BXs or 60 BXs if not feasible • driven by W HCAL timing • Physics event at BX number 10 • allow for main calorimeter contributions from previous BXs • Calorimeter time resolution of 1 ns with 20 ns multi-hit separation • Silicon detectors integrate over 10 ns • assumes starting time of integration is “physics hit” – occupancy ? • TPC track reconstruction for full 110 BX • tracks selected based on timing in other detectors (Si hits) • PFO Selection (needs study, just first estimate) • photons – require cluster time(< 1 ns ?) • neutral hadrons – require cluster time(< 5 ns ?) • tracks with cluster – require in time cluster (<5 ns ?) • need to account for helical track time to reach calorimeter • tracks with no associated cluster –(reject ?) Mark Thomson

  3. ILD Time-stamping Status • Implemented the above proposal • Can now routinely reconstruct events with 60 BXs overlay • required slicing TPC in two parts, +ve, -vez • approx 5 min/event (LEPTracking, FullLDCTracking, Pandora) • 110 BXs feasible, but may require further slicing • Implemented Calorimeter 20 ns multi-hit separation • Decided not to smear calorimeter times with resolution of 1 ns • New issue related to CLIC time structure • For looping tracks, i.e. low pT and low pZtrack takes finite time to • endcap Calorimeter • Hence may have thrown away associated calorimeter hits • Decided to reject all tracks which take more than 20 ns to • propagate to ECAL • Implemented track timing cuts • new processsor – CLICTrackSelector • cuts on SI hits + propagation time • doesn’t (yet) use times of TPC tracks crossing TPC endplate • keep tracks from V0s Mark Thomson

  4. PFO Selection • Plan to make cuts on reconstructed PFOs using calorimeter timing • reduce out-of-time background • believe ~factor 5 reduction is possible • e.g. PFO Selection (needs study, just first estimate) • photons – require cluster time < 1 ns • neutral hadrons – require cluster time < 5 ns • tracks with cluster – require in time cluster (<5 ns) • need to account for helical track time to reach calorimeter • tracks with no associated cluster – reject ? • pTand p cuts left to individual analyses • Following plots show cluster time (energy weighted mean) vs PFO pT • for PFOs from 91 GeV Z->uds events (colours) • and gamma gamma -> hadrons background (points) • broken down into PFO type (photon, neutral, charged) Mark Thomson

  5. Photons in Barrel Time/ns pT/GeV Mark Thomson

  6. Photons in Endcap Time/ns pT/GeV Mark Thomson

  7. Neutral Hadrons in Barrel Timing spread due to W HCAL Mark Thomson

  8. Neutrals in Barrel (E) • For clusters with ECAL energy > 0.5 GeV use ECAL hits only for cluster time Mark Thomson

  9. Neutrals in Endcap • One of main sources of background – dominated by PFOs made from • hits from multiple particles (one reason why full overlay is necessary) ! Background peaks Around 5ns, i.e. half of the 10ns window Mark Thomson

  10. Charged particles in Barrel Helical rather than straight propagation Dominated by HCAL Mark Thomson

  11. Charged particles in Barrel Dominated by HCAL Propagation times corrected Mark Thomson

  12. Charged particles in Barrel • For clusters with ECAL energy > 0.5 GeV use ECAL hits only for cluster time Mark Thomson

  13. Charged in Endcap • One of main sources of background – for tracks with small pT, background • is very large Need to look at p not just pT, e.g. only apply timing cuts to tracks with p<5 GeV Mark Thomson

  14. Where Now ? Cluster Timing Cuts • Prototype Algorithm in Pandora • Need to look at background in terms of p and pT • only apply additional PFO timing cuts to background dominated • region • needs some cut tuning ILD Reconstruction Path • Need to commit changes • Converge on ILD steering file Mark Thomson

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