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* the forward tracking resolution must be retained
 
* the forward tracking resolution must be retained
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== low Q2-tagger ==
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==Low Q2-tagger==
 
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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 />
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 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>.
 
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>
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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>
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'''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.
 
The resulting Q<sup>2</sup> distribution after applying all the requirements listed above is shown in the 4th row below.
{| border="0" cellpadding="5"
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{| class="wikitable" border="0" cellpadding="5"
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|-
 
|[[image:20x100.p.vs.theta.png‎|thumb|350px| 20 GeV x 100 GeV]]
 
|[[image:20x100.p.vs.theta.png‎|thumb|350px| 20 GeV x 100 GeV]]
 
|[[image:10x100.p.vs.theta.png‎|thumb|350px| 10 GeV x 100 GeV]]
 
|[[image:10x100.p.vs.theta.png‎|thumb|350px| 10 GeV x 100 GeV]]
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|[[image:5x100.Q2.png‎|thumb|350px| 5 GeV x 100 GeV]]
 
|[[image:5x100.Q2.png‎|thumb|350px| 5 GeV x 100 GeV]]
 
|}
 
|}
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For some details on running the low Q<sup>2</sup>-tagger simulations within the EicRoot framework, see the [https://wiki.bnl.gov/eic/index.php/LowQ2-tagger_Sim low Q2-tagger sim page]
 
For some details on running the low Q<sup>2</sup>-tagger simulations within the EicRoot framework, see the [https://wiki.bnl.gov/eic/index.php/LowQ2-tagger_Sim low Q2-tagger sim page]
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