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125 bytes removed ,  23:01, 1 November 2020
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==Low Q2-tagger==
 
==Low Q2-tagger==
for many physics topics it is important to tag the scattered lepton at very small scattering angles and such as very low Q<sup>2</sup>.
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for many physics topics it is important to tag the scattered lepton at very small scattering angles and such as very low Q<sup>2</sup>.<br />The main detector covers -4 to 4 in rapidity for the scattered lepton. So scattered leptons with a scattering angle > 178 degree will not be detected in the main detector.The plots below correlate the momentum of the scattered lepton with its scattering angle and its Q<sup>2</sup>.
 
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[[https://wiki.bnl.gov/eic/index.php/File:JA-Tagger acceptance_20201027.pdf|A study on tagger acceptance is given here.]]<br />The main detector covers -4 to 4 in rapidity for the scattered lepton. So scattered leptons with a scattering angle > 178 degree will not be detected in the main detector.
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The plots below correlate the momentum of the scattered lepton with its scattering angle and its Q<sup>2</sup>.
   
To see some of these low Q<sup>2</sup> leptons it is important to separate the scattered lepton from the outgoing lepton beam.  
 
To see some of these low Q<sup>2</sup> leptons it is important to separate the scattered lepton from the outgoing lepton beam.  
 
To have a reasonable low Q<sup>2</sup> acceptance the requirement for the IR is to transport<br />'''leptons with 10% momentum of the full beam energy (E<sub>e'</sub> >= 0.9 E) and with a scattering angle from 179.5 to 178 degree (180 degree being the outgoing beam) through the magnets.'''<br />The resulting Q<sup>2</sup> distribution after applying all the requirements listed above is shown in the 4th row below.
 
To have a reasonable low Q<sup>2</sup> acceptance the requirement for the IR is to transport<br />'''leptons with 10% momentum of the full beam energy (E<sub>e'</sub> >= 0.9 E) and with a scattering angle from 179.5 to 178 degree (180 degree being the outgoing beam) through the magnets.'''<br />The resulting Q<sup>2</sup> distribution after applying all the requirements listed above is shown in the 4th row below.
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