Mark ThomsonUniversity of Cambridge

LoI loose ends New physics studies? What next...

Future Plans…

This talk:

TILC09, Tsukuba, 21/04/2009 Mark Thomson 2

LoI Debrief Generally ILD physics/optimisation studies rather successful However a few loose ends:Backgrounds:

A great deal of progress on understanding backgrounds… Reconstruction software Nevertheless, the TPC studies are very impressive Silicon tracking studies made major progress, but (in my opinion) raised a number of questions

Physics: Still differences between analyses used by ILD and SiD which aren’t understood

In particular, Higgs BRs from qqcc Some very nice studies, but what should we do with them ?

In the next few slides, a few ideas to hopefully prompt discussion regarding future directions…

The LoI process, pushed ILD forwards very rapidly Should try not to lose too much momentum…

TILC09, Tsukuba, 21/04/2009 Mark Thomson 3

Large fraction of hits from low energy electrons/positrons from photon conversions Form tight helices, “micro-curlers”, along length of TPC Background concentrated on relatively few TPC readout pads Developed PatRec software to identify and remove “micro-curlers”

150 BXs of pair background

TPC Background

TILC09, Tsukuba, 21/04/2009 Mark Thomson 4

Top (pT>1 GeV) Background

Raw hits ~8,600 ~265,000

After ~8,500 ~3,000

Effective removal of large fraction of background hits

By eye – clear that this should be no problem for PatRec

TILC09, Tsukuba, 21/04/2009 Mark Thomson 5

Superimpose 150 BXs TPC background on For 100 events, NO loss in track-finding efficiency observed Similar story for 3x nominal background Believe this is a clear demonstration of the robustness of a TPC operating in ILC beam conditions

TILC09, Tsukuba, 21/04/2009 Mark Thomson 6

Background: VTX

Background in VTX detector complicated by assumptions for Si pixel readout rate IF one assumes single BX tagging capability then background is not an issue For ILD studies “conservatively” assume 30 s / 125 s integration times for VTX layers (0,1) and (2,3,4,5) respectively Therefore VTX integrates over 83/333 BXs Superimpose on fully-hadronic top-pair events at 500 GeV

200,000 background hits per event !

Also consider finite cluster size of background hits (~10 pixels) Significantly increases occupancy

layer Occ.

0 3.3 %

1 1.9 %

2 0.4 %

3 0.3 %

4 0.08 %

5 0.06 %

TILC09, Tsukuba, 21/04/2009 Mark Thomson 7

Background: VTX - fake tracks Combinatorics produce fake “ghost” tracks In addition to some real electron/positron background tracks Large combinatoric background challenges pattern recognition Reconfigured current algorithm (not ideal) From 83/333 BXs overlayed on : reconstruct ~34 “ghost” tracks/event (~1/3 are genuine) Rejected by requiring at least 1 SIT hit or >10 TPC associated hits

34/event 1/event

Left with ~0.5 GeV per event (mixture of real tracks/combinatorics)

TILC09, Tsukuba, 21/04/2009 Mark Thomson 8

Personal view TPC studies look pretty solid The VTX studies assumed integration times of 83/333 BXs (31/125 s) To get background level down to acceptable level assumed single BX-tagging capability in SIT and in TPC Occupancies in inner layers are high for nominal ILC background i.e. 2-3 % With assumed integration times, safety factor not great, i.e. for 10 x current background probably lose inner layers

Issue of time-stamping in ILD needs more consideration

Comments ?

I believe:

TILC09, Tsukuba, 21/04/2009 Mark Thomson 9

Physics Should think carefully about what to do with current physics studies

There are a number of individual publication being pursued (this is good) But I would like to raise the possibility of a more general ILD physics publication addressing a couple of bigger issues.. How about a combined ILD physics paper ? e.g. comparing reach for

• different polarisations• none• 80% e-

• 80% e- ; 30 % e+

• 80% e- ; 60 % e+

• different luminosity spectra• RDR • low-p• …

The text describing the analyses (at an appropriate level exists) All results could be obtained by reweighting current samples Such a publication would be timely; these are relevant questions for the design of the ILC

Is this worth pursuing ?

TILC09, Tsukuba, 21/04/2009 Mark Thomson 10

Physics at 1 TeV The question of ILD performance at 1 TeV is bound to come up Should we be thinking about this now ? What would this mean:

preparing stdHep files simulation of some processes ?

Comments ?

TILC09, Tsukuba, 21/04/2009 Mark Thomson 11

Optimisation Plans To date concentrated on global optimisation

Now need to focus on more sub-detector specific issues These fall into two categories:

• alternate technologies, e.g. DHCAL, Scint-W ECAL• sub-detector “global” issues

• e.g. does the thickness of the TPC end-plate really matter ?• … add your favourites here …

Comments ?

We need to start to construct a list of questions we want to answer Propose that each sub-detector group comes up with a list of such question (via EB reps) We can then try and prioritise/make more concrete plans

TILC09, Tsukuba, 21/04/2009 Mark Thomson 12

That’s all