A Consideration on Muon System II

1
A Consideration on Muon System II

• Y.Sugimoto
• KEK
• 2005.12.13

2
Muon ID in a Jet

• How to identify muon track in the TPC?
• Conventional method
• Extrapolate TPC track and find a matching track
  segment in the Muon Tracker within a range of
  expected spread by multiple scattering
• For muons inside jets (small ptjet), background
  is large
• Pion punch-through
• Decay of shower pion
• Pion sail-through (irreducible, but very small
  for GLDgt7l)
• Pion decay-in-flight (irreducible)
• Kaon decay-in-flight (reducible by dE/dx and
  kink)
• If there are two near-by tracks in TPC, both can
  be the muon candidate, or mismatching due to M.S.
  can happen
• At ILC, we have to study more collimated jets and
  the matching using spatial information only may
  not be sufficient

?
3
Power of GLD

• Deflection of muon
  0.15BRc2 0.3BRc(RM-Rc)
• (Rc coil radius, RM MUD radius, reverse
  bending outside coil not included)
• At the front surface of MUD
• TOPAZ 1 Tm2
• OPAL 1 Tm2
• ALEPH 4 Tm2
• GLD 9 Tm2
• SiD 8.5 Tm2
• LDC 11 Tm2

(dE/dx not taken into account)
4
Muon deflection and M.S.

• Muon deflection in front of iron return yoke is
  x20 larger than the fluctuation by multiple
  coulomb scattering due to calorimeter
• Extrapolation of TPC track to find a matching
  track segment in the muon tracker within a range
  of expected spread by multiple scattering will
  work quite well (dE/dx and bending by B field
  have to be taken into account Kalman filter can
  do equivalent procedure?)
• Better spatial resolution can do better job for
  high momentum tracks

5
Summary

• Because of large deflection of tracks in GLD
  solenoid, muons below 10 GeV/c becomes
  isolated tracks
• So, the muon system does NOT have to have muon
  range measurement capability in the barrel region
• However, for low momentum muons, multiple point
  measurement with first few layers with thin Fe
  plates would be effective to define a track
  segment and discriminate it from shower punch
  through
• Because of the sizable deflection even for high
  momentum tracks, the conventional method of muon
  identification (extrapolation of TPC track to
  find a matching track segment in the muon tracker
  within a range of expected spread by multiple
  scattering) will work quite well (dE/dx and
  bending by B field have to be taken into
  account), and stand-alone momentum measurement by
  the muon system may not be necessary
• Even with the conventional method, however,
  better spatial resolution of the muon tracker (at
  least for few layers) can do the better job for
  high momentum muons

6
Appendix

• Stand-alone p measurement
• With L2.3m, BFe2T, Nmeas5, smeas1cm,