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== Spectator protons ==  
 
== Spectator protons ==  
   −
-Crucial for identifying processes with a neutron “target” (e+n) in e+<sup>3</sup>He. <br>
+
-Crucial for identifying processes with a neutron “target” (e+n) in e+<sup>3</sup>He (and e+d). <br>
 
-Spectator neutron (<~3 mrad) can be measured by ZDC.<br>
 
-Spectator neutron (<~3 mrad) can be measured by ZDC.<br>
-Tagging spectator protons from <sup>3</sup>He. <br>
+
-Tagging spectator protons from <sup>3</sup>He (and d): <br>
*Relying on separation from magnetic rigidity (B<sub>r</sub>) changes <sup>3</sup>He: p = 3/2:1
+
*Relying on separation from magnetic rigidity (B<sub>r</sub>) changes <sup>3</sup>He: p = 3/2:1 (d:p = 2:1)
 
*No need to reconstruct momentum but need clean identification: position+directional measurement
 
*No need to reconstruct momentum but need clean identification: position+directional measurement
 
*Common detectors (Roman Pots) can be utilized for tagging forward proton from DVCS and the spectator protons from <sup>3</sup>He
 
*Common detectors (Roman Pots) can be utilized for tagging forward proton from DVCS and the spectator protons from <sup>3</sup>He
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|[[image:p.png|thumb|350px|]]
 
|[[image:p.png|thumb|350px|]]
 
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'''Scattering angle vs. momentum of spectator protons in e+<sup>3He</sup> at 10(e)x100(N) GeV [left].  The projections in angle (rad) and momentum (GeV/c) are shown in the center and right panels. The acceptance of the protons at the detector depends on the IR optics of the beam.  The calculation was done using DPMJETIII with Fluka implementation.  The requirements of the detectors for the spectator tagging with an IR design can be found [https://indico.bnl.gov/getFile.py/access?contribId=12&sessionId=2&resId=0&materialId=slides&confId=405 here].'''
+
'''Scattering angle vs. momentum of spectator protons in e+<sup>3He</sup> at 10(e)x100(N) GeV [left].  The projections in angle (rad) and momentum (GeV/c) are shown in the center and right panels. The acceptance of the protons at the detector depends on the IR optics of the beam.  The calculation was done using DPMJETIII with Fluka implementation.  The requirements of the detectors for the spectator tagging with an IR design can be found [https://indico.bnl.gov/getFile.py/access?contribId=12&sessionId=2&resId=0&materialId=slides&confId=405 here].  The distributions are similar for spectator protons in e+d as the dominant contribution to the angular and momentum distribution is from fermi momenta in the "target" nucleus.'''
    
== Detector Space and Magnetic Field ==
 
== Detector Space and Magnetic Field ==
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