1. UK Simulation Planning
UK L1Calo upgrade project now “funded”
still uncertainties given current climate, but a positive message
need to clearly define goals of UK simulation effort
Work should focus on the central questions for UK (and L1Calo) upgrade
generally a good approach – identify main physics issues and
critical questions
What are the critical questions? Very broadly…
How does current system perform as function of luminosity
trigger rates
thresholds necessary to keep rates “reasonable”
impact on physics
What is required for Phase I (1-2 E34) ?
need for CMM++/Topological processor – not yet demonstrated
how much do topological triggers bring for L1Calo ?
benefit of L1Muon in possible topological processor
What is required for Phase II (5 E34) ?
different type of question
upgrade driven by LAr as well as pile-up
much more open-ended…
RAL, 17th August 2010
Mark Thomson 1

2. What do we know now? What we know now:
Simulating effects of pile-up in ATLAS is non-trivial…
current studies suggest need for upgraded L1Calo at Phase I
but not yet a compelling definition of upgrade requirements
not yet fully demonstrated benefits of topological processor for physics
What we don’t know:
Detailed knowledge of how trigger rates scale with Luminosity
Detailed knowledge of how thresholds (for reasonable trigger rates)
scale with lumi
Impact on physics
What physics signatures benefit from topological triggers vs. higher
thresholds
Phase II…
How should we approach the problem:
In principle, rather easy:
Just ask the right questions (the hard bit)
Then do the work

3. Example: electron triggers
Central Questions – driven by physics needs:
What are the limitations of current L1Calo :
e.g. how do the electron thresholds scale with lumi?
limited by rate due to pile-up + handle of “noise” thresholds
would like a plot of EN trigger rate versus lumi (+noise threshold)
a “killer plot” would be “Electron energy threshold (50%) for
trigger rate of 10 kHz as function of luminosity”
Trigger Threshold
Luminosity
would need to optimize noise threshold at each point
but encapsulates performance for single physics object

4. How would we make such a plot…
need large pile-up samples ~100k events (1/4000 = 10 kHz)
only gives to 20 % error at 10 kHz
would also need “signal” sample
for electrons not so hard… could use single electons from G4
How to Assses Impact on Physics:
If we can understand L1Calo in terms of threshold vs energy…
then physics impact can be understood in conjunction with
physics groups
define benchmark reactions
inform requirements for Phase I
For today try and define “questions” we want to
address and what work is required