1 A Consideration on Muon System II Y.Sugimoto KEK

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 p t jet ), background is large:  Pion punch-through  Decay of shower pion  Pion sail-through (irreducible, but very small for GLD:>7 )  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 ~ 0.15BR c BR c (R M -R c ) (R c : coil radius, R M : MUD radius, reverse bending outside coil not included) At the front surface of MUD TOPAZ ~1 Tm 2 OPAL ~ 1 Tm 2 ALEPH ~ 4 Tm 2 GLD ~ 9 Tm 2 SiD ~ 8.5 Tm 2 LDC ~ 11 Tm 2 (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 P (GeV/c)  m.s. (cm) Deflection (cm)

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 L=2.3m, B Fe =2T, N meas =5,  meas =1cm,