Changes

Jump to navigation Jump to search
no edit summary
Line 1: Line 1:  
__NOTOC__
 
__NOTOC__
This page discusses the requirements imposed by the EIC physics on the IR design.<br />
+
This page discusses the requirements imposed by the EIC physics on the IR design.<br />The following requirements will be discussed in more detail below
The following requirements will be discussed in more detail below
   
# [[#Breakup Neutrons | the detection of neutrons of nuclear break up in the outgoing hadron beam direction]]
 
# [[#Breakup Neutrons | the detection of neutrons of nuclear break up in the outgoing hadron beam direction]]
 
# [[#Scattered protons from exclusive reactions | the detection of the scattered protons from exclusive and diffractive reaction in the outgoing proton beam direction]]
 
# [[#Scattered protons from exclusive reactions | the detection of the scattered protons from exclusive and diffractive reaction in the outgoing proton beam direction]]
Line 23: Line 22:  
== Neutrons from ep → e'n+pi+==  
 
== Neutrons from ep → e'n+pi+==  
 
To measure certain GPDs exclusive Pseudoscaler and Vector meson production are the golden channels.
 
To measure certain GPDs exclusive Pseudoscaler and Vector meson production are the golden channels.
In some of these process you have a charge exchange reaction and the forward going proton is changed into a neutron, i.e. ep → e'n+pi+<br />
+
In some of these process you have a charge exchange reaction and the forward going proton is changed into a neutron, i.e. ep → e'n+pi+<br />In this case it is critical to detect the neutron and measure its angle and energy.
In this case it is critical to detect the neutron and measure its angle and energy.
   
Below are several plots thanks to Tanja Horn simulating the the angle and t = p<sub>t</sub><sup>2</sup> of the neutron for the following electron proton beam energy combinations.
 
Below are several plots thanks to Tanja Horn simulating the the angle and t = p<sub>t</sub><sup>2</sup> of the neutron for the following electron proton beam energy combinations.
 
{| class="wikitable" border="0"
 
{| class="wikitable" border="0"
Line 46: Line 44:  
|}
 
|}
 
'''This poses the following requirement that for different hadron beam energies 100 GeV and 250 GeV protons with a momentum at a maximum of 10% lower then the proton beam energy and a scattering angles up to 10 mrad need to be transported through the different magnets.'''
 
'''This poses the following requirement that for different hadron beam energies 100 GeV and 250 GeV protons with a momentum at a maximum of 10% lower then the proton beam energy and a scattering angles up to 10 mrad need to be transported through the different magnets.'''
<br />
+
<br />There is basically no correlation between the momentum and the scattering angle. For diffractive events an acceptance of 5% of the beam momentum would be totally acceptable as well.
There is basically no correlation between the momentum and the scattering angle. For diffractive events an acceptance of 5% of the beam momentum would be totally acceptable as well.
   
These protons cannot be detected in the main detector. The standard detectors used to detect the scattered proton are roman pots placed at different distances from the IR.
 
These protons cannot be detected in the main detector. The standard detectors used to detect the scattered proton are roman pots placed at different distances from the IR.
 
Using this detector technology poses an other requirement on the machine performance. To reach as small scattering angles as possible a small emittance of the beam is crucial as there is also an additional requirement of 10 σ clearance from the core of the beam.  
 
Using this detector technology poses an other requirement on the machine performance. To reach as small scattering angles as possible a small emittance of the beam is crucial as there is also an additional requirement of 10 σ clearance from the core of the beam.  
<br />
+
<br />'''This translate in the requirement thet we need an acceptance in pt<sup>2</sup> of 0.17 GeV to 1.3 GeV, which translates into a t acceptance of 0.03 GeV<sup>2</sup> to 1.6 GeV<sup>2</sup> at 100 GeV and 250 GeV proton beam energy.
'''This translate in the requirement thet we need an acceptance in pt<sup>2</sup> of 0.17 GeV to 1.3 GeV, which translates into a t acceptance of 0.03 GeV<sup>2</sup> to 1.6 GeV<sup>2</sup> at 100 GeV and 250 GeV proton beam energy.
   
To have good acceptance at low scattering angle the beam needs to be cooled in transverse direction to achieve a beam angular divergence of ~100μrad'''
 
To have good acceptance at low scattering angle the beam needs to be cooled in transverse direction to achieve a beam angular divergence of ~100μrad'''
   Line 58: Line 54:  
== Spectator protons ==  
 
== Spectator protons ==  
   −
-Crucial for identifying processes with a neutron “target” (e+n) in e+<sup>3</sup>He (and e+d). <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 />-Tagging spectator protons from <sup>3</sup>He (and d): <br />
-Spectator neutron (<~3 mrad) can be measured by ZDC.<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 (d:p = 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
Line 72: Line 66:  
'''Scattering angle vs. momentum of spectator protons in e+<sup>3</sup>He 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 distributions are from fermi momenta in the "target" nucleus.'''
 
'''Scattering angle vs. momentum of spectator protons in e+<sup>3</sup>He 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 distributions are from fermi momenta in the "target" nucleus.'''
 
==Detector Space and Magnetic Field==
 
==Detector Space and Magnetic Field==
the [https://wiki.bnl.gov/eic/index.php/ERHIC_Dedicated_Detector_Design detector] needs a '''+/- 4.5m beam element free region'''.<br />
+
the [https://wiki.bnl.gov/eic/index.php/ERHIC_Dedicated_Detector_Design detector] needs a '''+/- 4.5m beam element free region'''.<br />Any magnetic field which is introduced in addition to the solenoidal field of the detector, needs to obey the following requirements.  
Any magnetic field which is introduced in addition to the solenoidal field of the detector, needs to obey the following requirements.  
   
* the region of the RICH in the forward and backward direction should be free of any magnetic field
 
* the region of the RICH in the forward and backward direction should be free of any magnetic field
 
* the magnetic field homogeneity needs to obey the requirements posed by the TPC
 
* the magnetic field homogeneity needs to obey the requirements posed by the TPC
Line 80: Line 73:     
==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>.<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>.
+
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>.
To see some of these low Q<sup>2</sup> leptons it is important to separate the scattered lepton from the outgoing lepton beam.  
+
 
 +
 
 +
A study on tagger acceptance is given [https://wiki.bnl.gov/eic/upload/JA-Tagger acceptance_20201027.pdf 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.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 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.
 
{| class="wikitable" border="0" cellpadding="5"
 
{| class="wikitable" border="0" cellpadding="5"
11

edits

Navigation menu