Mark Thomson University of Cambridge

Timing Status

Mark Thomson 2

ILD Time-stampingAt 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 ?)

CLIC WG6, 26/1/2011

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, -ve z approx 5 min/event (LEPTracking, FullLDCTracking, Pandora) 110 BXs feasible, but may require further slicing

Implemented Calorimeter 20 ns multi-hit separation

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

CLIC WG6, 26/1/2011

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 pZ track 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

Mark Thomson 4

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 ?

pT and p cuts left to individual analyses

CLIC WG6, 26/1/2011

PFO Selection

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

CLIC WG6, 26/1/2011

Tim

e/n

s

pT/GeV

Mark Thomson 6

Photons in Endcap

CLIC WG6, 26/1/2011

pT/GeV

Tim

e/n

s

Mark Thomson 7

Neutral Hadrons in Barrel

CLIC WG6, 26/1/2011

Timing spread due toW HCAL

Mark Thomson 8

Neutrals in Barrel (E)

CLIC WG6, 26/1/2011

For clusters with ECAL energy > 0.5 GeV use ECAL hits only for cluster time

Mark Thomson 9

Neutrals in Endcap

CLIC WG6, 26/1/2011

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 ofthe 10ns window

Mark Thomson 10

Charged particles in Barrel

CLIC WG6, 26/1/2011

Dominated by HCAL

Helical rather thanstraight propagation

Mark Thomson 11

Charged particles in Barrel

CLIC WG6, 26/1/2011

Dominated by HCALPropagation times

corrected

Mark Thomson 12

Charged particles in Barrel

CLIC WG6, 26/1/2011

For clusters with ECAL energy > 0.5 GeV use ECAL hits only for cluster time

Mark Thomson 13

Charged in Endcap

CLIC WG6, 26/1/2011

One of main sources of background – for tracks with small pT, background is very large

Need to look at p not justpT, e.g. only apply timing cuts to tracks with p<5 GeV

Mark Thomson 14

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

CLIC WG6, 26/1/2011

Where Now ?

Cluster Timing Cuts

ILD Reconstruction Path

Need to commit changes Converge on ILD steering file