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Muon System: Challenges (Talk #1)

Muon System: Challenges (Talk #1). Pascal Dupieux (ALICE) Alexei Safonov (CMS) Peter Kluit (ATLAS) Giacomo Graziani ( LHCb ). Muon and Physics at CMS & ATLAS. Robust muon triggering and identification are major discovery drivers at the LHC:

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Muon System: Challenges (Talk #1)

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  1. Muon System: Challenges (Talk #1) Pascal Dupieux (ALICE) Alexei Safonov (CMS) Peter Kluit (ATLAS) Giacomo Graziani (LHCb)

  2. Muon and Physics at CMS & ATLAS • Robust muon triggering and identification are major discovery drivers at the LHC: • Critical for precision Higgs measurements of both bosonic and fermionic couplings: • H WW and ZZ key for HVV couplings • Htt mth+X is key for measuring Hff couplings • Relative impact increases at high luminosity • Muons are least affected by collective effects of occupancy, e.g. trigger rates grow only linearly with luminosity • Focus on maximizing the potential of large datasets to be collected at HL-LHC • Maintain performance • Major acceptance gains in forward region CMS: 50% acceptance increase if hmax=2.44.0

  3. Triggering Challenges at CMS • Triggering capability is most vulnerable at high luminosity • Forward region is particularly challenging due to high rates • Hard to control rate for h>1.6 without severe efficiency losses • Flattening of the rate plots exacerbates these challenges • Once on the “plateau”, extreme threshold increases required for even modest rate reduction • Improvements are possible: • Precision measurements of muon bending angle help control the rate • Example: GEM-based detector GE-1/1 in the region 1.6<|h|<2.1 • Even larger developing challenge is the region 2.1<|h|<2.4: • The low performance “corner” for both the new track trigger and current muon system • Very real danger of loosing trigger there

  4. Forward Triggering Options • GE-1/1 is shown to allow x5-10 trigger rate reduction in 1.6<|h|<2.1 • Extending GEM “bending angle” success into 2.1 <|h|<2.5 not easy • Gains limited by magnetic field • New detectors only helpful if placed in stations close to IP • Radial B-field turns muons back reducing separation of soft and hard muons while multiple scattering demolishes resolution • Rate reduction of x5-6 only with the “all of the above” solution: • A high precision GEM-based “near tagger” in front of ME-11 • Can be integrated with the calorimeter • A lower resolution GEM in station 2, and GRPC-based taggers in stations 3,4

  5. ME-0: Forward Muon Tagger • Extend offline muon coverage • Upper portion 2.1<|h|<2.5 also has trigger capabilities • Match: • Forward pixel extension tracks • Muon “stubs” (multi-layer detector to suppress neutron backgrounds) • Challenge is in maintaining low rate of accidental coincidences of reconstructed pixel tracks with hits due to soft muons • At this eta ultra soft muons with pT=0.5 GeV have enough momentum to make it through the material • Fortunately, multiple scattering is low enough to maintain low fake rate • Strong potential for large acceptance gains pT=20 GeV

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