1. SLHC Muon Upgrades and Impact on Trigger
Alexei Safonov
Texas A&M University
(for many people who contributed to this talk)

2. Challenges of the SLHC Regime
Increase in hit occupancies:
Combinatorics in finding segments and ghosts
Processing time increase, implications for electronics
Out of time pile-up is no more negligible:
Hits from previous BXs can induce “deadtime”
Implications for electronics requirements
Increased number of segments in chamber/station/sector
Hard limits built into the system significantly affect standalone tracking efficiency
Increased segment combinatorics has implications on track finder electronics requirements
Assignment mistakes and momentum resolution have paramount effect on performance:
Loss of efficiency for single threshold muon triggers
Promotion of soft “muons” towards higher pT increases and flattens the rate
CMS Upgrade Workshop

3. Trigger Rate Flattening
Softer muons get occasionally promoted to higher pt
Because there are a lot of them, this “occasional” promotion is enough to flatten the trigger rate for acceptable thresholds
Ultimate solution will have to include tracker to improve momentum measurement
From J. Alcaraz
CMS Upgrade Workshop

4. Efficiency Degradation
Endcap Muon pT>10 efficiency for PU=400
No neutron backgrounds
Severe degradation of efficiency
Main reasons due to low level electronics limitations
Resolving these issues will cause significant increase in rate of primitives requiring additional upgrades (e.g. CSC Track Finder)
CMS Upgrade Workshop

5. Key Directions of Ongoing R&D
Barrel:
MTT detector to resolve ghost ambiguities
Moderate upgrade of existing electronics for Phase I
Matching with tracker to improve momentum resolution and control rates for Phase II
Endcap:
New station ME4/2 to increase redundancy in central region for Phase I
Upgraded electronics for ME1/1:
DCFEBs, TMB, ALCT(?) for ME1/1 for Phase I to increase trigger eta coverage from 2.1 to 2.4
Upgrade of the CSC Track finder and port cards to deal with segment multiplicities
CMS Upgrade Workshop

6. Simulation Framework FullSim is much preferred option:
Occupancy related effects and out-of-time pile-up very important
Implementation of High PU environment is challenging
Severe memory problems
Custom solution (Khotilovich):
FullSimin a fraction of the detector:
All bells and whistles including out of time pile-up
Drop unnecessary information and code components
Neutron backgrounds – work in progress (R. Wilkinson, Caltech)
For more details see talk by Khotilovich in Simulations session of the workshop
Khotilovich, Texas A&M
CMS Upgrade Workshop

7. MTT Detector R&D
From A. Montanarri
A new tile tagging detector in front of the Barrel muon system:
Ghost/fake suppression, also important for tracker matching
Technology considered:
Scintillator tiles (Aachen, Bologna)
2D RPC (Bari)
Promising results:
Scintillator tiles show ~20 g signal with unglued fiber and SiPM
Simulation predicts ~80 g for glued one
CMS Upgrade Workshop

8. New Station ME4/2 & High Eta Region
From J. Hauser, D. Loveless
Increased redundancy improves CSC TF track reconstruction
Substantial decrease in trigger rate and better behavior
Improvement in reconstruction efficiency of high quality tracks
All technology to build new chambers intact:
A prototype built this year
Another “big” project is restoring efficiency beyond eta=2.1 (more on this later)
Khotilovich, Texas A&M
CMS Upgrade Workshop

9. Barrel Electronics
Use PU MC (including neutrons) to estimate hit occupancies in chambers
Dominated by low multiplicity hits, occasionally full segments
ROB (read out boards) seem to be safe handling the rate
Molina, Bedoya, Arse
Evaluate ROS (read out server) performance for scenarios:
Hits “all over the place” (most difficult)
Track-like correlated hits
All in one channel
Nhit>60: ROS can’t run on par with 100 kHz L1 rate
Likely needs an upgrade
CMS Upgrade Workshop

10. Endcap Electronics
ME1/1 is most affected by SLHC occupancies and rates
The plan is to build new electronics for ME1/1 capable of operating in this environment
New Digital CFEBs (DCFEBs) with optical links necessary to handle high rate
That triggers necessary upgrade of TMB, DMB, LVDB to handle optical links
Expanding trigger beyond h=2.1 requires deeper modifications of at least the TMB board
Existing electronics from ME1/1 will be moved to new ME4/2 saving substantial costs
As it turned out, simple adaptation of new electronics to new DCFEBs is not enough to maintain trigger performance
CMS Upgrade Workshop

11. TMB Upgrade – High Eta Region
EMU instrumented to h=2.4
Trigger stops at 2.1 because chambers in ME1/1 are split in high (ME1/1a) and low (ME1/1b) eta regions
ME1/1a have strips ganged rendering stubs useless for track reconstruction
Plan: un-gang strips and implement a more sophisticated algorithm in TMB to expand trigger from h=2.1 to 2.4
A new algorithm developed and demonstrated to work with simulation
Requires deep redesign of TMB
Khotilovich, Texas A&M
CMS Upgrade Workshop

12. TMB Upgrade
Simulation has shown large inefficiency at high PU traced to TMB dead time
TMB produces cathode stubs and matches them with wire stubs to make LCTs
Chamber-wide deadtime of 6 BXs after a trigger leads to “sensitivity” to out of time PU
Chamber is often “dead” when a muon shows up
Solutions: improve performance by reducing deadtime and switching from chamber-wide to “regional” dead-time
Khotilovich, Texas A&M
CMS Upgrade Workshop

13. MPC and CSC TF Upgrades
Restoring performance of lower level algorithms leads to substantial increase in rate of trigger primitives sent downstream
Largely unavoidable as all those stubs are real: one needs more information (other stations) to select the “good” ones
Two components affected and need an upgrade:
CSC TrackFinder to cope with more stubs in order to play its new larger role
MPC (Muon Port Cards handling degree sectors) and the MPC-TF connection to get the larger number of stubs to CSCTF
Acosta, Madorsky, Matveev, Padley
CMS Upgrade Workshop

14. Barrel Muon-Track Matching
Use “bending angle” at DT to extrapolate muons into the tracker
High correlation allows narrow “roads”
Uncertainty in vertex z-position dominates q resolution
Higher tracker layers less affected
Matching algorithm nearly completed, looking into pT measurement and rates
Full gory details in Ignazio’s talk in tracking session
Df(muon, tracker stub)
Bending angle fB
Zotto, Lazzizzera, Vanini
CMS Upgrade Workshop

15. Endcap Muon-Tracker Matching
Propagate along roads from EMU into tracker:
Eta- and tracker layer-dependent width of the region of interest
Select tracker stub pairs consistent with muon stubs
Reconstruct z0, q, pT
Very promising results, now switching to rate calculations
For details see Ivan’s talk in tracking session
Furic, Fisher, at al.
CMS Upgrade Workshop

16. Summary
The big picture starts emerging thanks to the large progress made over the past months
Shortcomings of the current system identified and understood with simulation studies
Potential improvements from using track trigger are being understood and quantified
Need to bring all the pieces (and add missing ones, e.g. neutron backgrounds) together:
Common samples, single trigger emulator framework, well established performance figures
And we better do it before first data when everyone will be busy discovering Higgses!
More work needed to improve full simulation framework
CMS Upgrade Workshop