Study of SHMS resolution

Using the following setup for SHMS single arm MC

• • 2 GeV , 20 deg scattered electrons
  • Reconstruction of tracks in the focal plane assumed 200 microns resolution.
  • LH2 target with 20cm length. Assume beer can with radius of 3.37cm and wall thickness in 0.005in Al.
  • 16 mil Al scattering chamber window (X0=8.89cm) followed by 15 cm air (X0=30420cm)
  • Spectrometer entrance window 15 mil Kevlar (X0=74.6cm) and 5 mil Mylar (X0=28.7cm)
  • Spectrometer exit window spectrometer exit window, 15 mil Kevlar, 5 mil Mylar (use 20 mil,X0=53.3)
  • Two options in Hut when AR/Neon Cerenkov is removed
    • Vacuum pipe so the the spectrometer exit window is moved to location of Cerenkov exit window
    • Helium bag. The spectrometer exit window is located in front of Cerenkov entrance, but the Cerenkov is replaced by a helium bag. Assume the entrance and exit of helium bag is aluminized mylar. Each window is 17 micron mylar and 3 micron aluminum. Filled with helium ( Radlen = 754560 cm).
  • Drift through air until drift chamber 1
  • Chamber 1 entrance foil, 1 mil of Mylar
  • Scattering in drift chamber, for each plane
    • Effective cathode plane, Be/Cu with Rad Len = 28.7cm , 0.0005 in
    • Drift through Chamber gas, 50/50 ethane/argon with Rad Len = 16700.0cm
    • Effective wire plane, 25 micron W+Be/Cu
    • Fill hit position for plane
    • Drift through Chamber gas, 50/50 ethane/argon with Rad Len = 16700.0cm
  • Chamber 1 exit foil, 1 mil of Mylar
  • Drift through air until drift chamber 2
  • Chamber 2 entrance foil, 1 mil of Mylar
  • Scattering in drift chamber, for each plane
    • Effective cathode plane, Be/Cu with Rad Len = 28.7cm , 0.0005 in
    • Drift through Chamber gas, 50/50 ethane/argon with Rad Len = 16700.0cm
    • Effective wire plane, 25 micron W+Be/Cu
    • Fill hit position for plane
    • Drift through Chamber gas, 50/50 ethane/argon with Rad Len = 16700.0cm
  • Chamber 2 exit foil, 1 mil of Mylar

Comparing resolutions with vaccuum pipe versus helium bag

• Table with the sigma for all events

mc FLAGS	Xptar (mr)	Yptar (mr)	Delta %	Ytar (cm)
no wire chamber smearing, no multiple scattering in material	0.08	0.01	.014	.002	wire chamber smearing, no multiple scattering in material	0.36	0.26	.038	.084	wire chamber smearing, multiple scattering in material with vacuum pipe	1.00	0.94	.072	.12	wire chamber smearing, multiple scattering in material with helium bag	1.04	0.96	.092	.14