1. + GE2/1 Case Considerations Alexei Safonov

2. + CMS Muon Upgrades CMS Technical Proposal in its part related to muon systems lists following: MEX/1 electronics upgrade (needed to keep up with L1 rate and latency GE1/1 detector (“early Phase- 2” to aid forward muon trigger) & a matching GE2/1 (regular Phase-2) GE0/1 detector (extends offline coverage beyond  =2.4, a.k.a. ME0) RPC stations 3/1 and 4/1 (based on improved technology) DT mini-crates 2

3. + GE2/1: Local Reconstruction Helps improve local stub- reconstruction efficiency in station 2 Without it, local stub reconstruction inefficiency due to CSC HV spacers Overall increase in efficiency due to requiring 3 hits instead of 4 if GEM hits are present Cant drop it in near stations as without an extra confirmation as neutron backgrounds can increase 3

4. + GE2/1: L1 Muon Track Reconstruction Better local reconstruction propagates into higher efficiency for Track Finding Here, we use 3+ stub configuration, which is the tighter option leading to low trigger rate (assume we are considering up to 200 PU) Caveat: below plots also include RE3/1-4/1, but with CSC 3 hit requirement in far stations we only lose 1% in plateau if RE3/1 and RE4/1 are disabled Effect on trigger rate is limited: even without GE1/1, on itself GE2/1 rate reduction is less than x1.5-2 (limited by ME2/1 resolution at L1) 4

5. + Muon Triggering at HL-LHC Tracking trigger will help tremendously for the entire physics program Matching muons with tracks allows dramatic improvement in resolution and trigger rate But… many physics models (new and old ones) predict long lived particles Higgs portal, dark sector, new bosons, SUSY extensions, W-primes etc. CMS won’t see any of that new physics if it’s there Tracking trigger inefficient for dxy above ~2 mm 5

6. + Is Standalone Muon Trigger at HL- LHC Possible? Absolutely! Even with no improvements, a dimuon trigger will work Take thresholds from Phase-1 L1 Upgrade Trigger TDR for 2.2x10 34 : pt=15 and 10 GeV yielding 10 kHz of rate GE1/1 will make it more like 7.5 kHz At 5x10^ 34 that trigger will yield a rate of ~15 kHz as all muon triggers evolve linearly Efficient to modestly displaced muons: Studied in the barrel: current muon trigger is efficient to muons with dxy up to ~10 cm Beyond that the problem is in p T assignment Still beats 2mm by a large margin! So it is absolutely doable, but requires maintaining standalone muon trigger capabilities (dimuon = 2 x standalone muon) 6

7. + Muon Trigger at HL-LHC Current barrel muon trigger p T assignment is inefficient for highly displaced muons It finds them, but p T is measured low Impact parameter of ~10cm still beats 2mm by a large margin, but we may be able to do better Study shows the problem is a consequence of the momentum measurement algorithm focusing on absolute values of bending angles in station 1 Great for prompt muons, really non-optimal for displaced muons 7

8. + Stub Alignment Algorithm Checks if the stubs are aligned with each other If aligned, it’s high p T, whether prompt or displaced Figure of merit: difference of inverse bend angles 1/  Implies we can measure bending angles in at least some stations New p T assignment works well with even a very simplistic algorithm Trigger rate (PU only) is the same as for the current algorithm Should decrease with adding more features to the algorithm Gearing up for a more complete simulation Working on implementing it in HLT (Sven) Started expanding into forward region (Jose) 8

9. + Bending Angles Important for triggering on highly displaced muons Work well in the barrel: Thick detectors make a large lever arm, large magnetic field CSC bending patterns in ME-X/2 may be sufficient as magnetic field is much larger in ME2/1 compared to ME1/1 The only problem is we won’t have these studies done by the end of this Summer Works in the very forward region Weakened magnetic field, but GE1/1 example says that an increased lever arm helps Need more than a single angle measurement (GE2/1!) Region of eta below 1.6: 9

10. + Further Considerations If ME1/1 performance at HL-LHC is significantly degraded, having high efficiency in station 2 will help GE2/1 helps increase that efficiency from 80-85% to 95% Can be important for matching with tracking trigger tracks as GE1/1 alone HLT uses standalone muon reconstruction in its selections If ME3/1 and ME4/1 do not receive new electronics, expect decrease in reconstruction efficiency Additional points from GE2/1 and GE2/1-ME2/1 bending angle will help strengthening standalone muon reconstruction in that region At the very least descoping both GE2/1 and ME3/1+ME4/1 in the same scenario seems worrisome 10