ERHIC Dedicated Detector Design

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The design philosophy of the dedicated eRHIC detector is to have a detector, which is suited for Phase-I and II of eRHIC and
accounts for all the requirements given by the EIC physics program as described here.
Phase-I: full RHIC hadron energies combined with 5 - 10 GeV lepton beams
Phase-II: full RHIC hadron energies combined with lepton beam energies 10 - 30 GeV
The detector and its roman pots and other equipment has been integrated in an IR design as described here
The detector design is flexible enough, that detector parts can be staged according to their importance for the different phases.
The figure below shows the development of the detector from Phase-I to Phase-II.

Phase-I dedicated eRHIC detector
Phase-II dedicated eRHIC detector

Magnet Design:

The design details and the how-to are described in this dedicated page

Tracking detectors:

It is very important to have over a wide-rapidity range excellent momentum resolution to provide excellent photon - hadron/lepton separation to identify the scattered lepton.
To have good x-Q2 resolution for the lepton or hadron method it is also important to measure the momentum of the particles and particular the scattered lepton well.
The hadron momentum is also needed as input for π ,K, p separation through RICH detectors in the forward/backward direction.
The detector technologies currently under consideration are:

  • Barrel micro-vertex tracking (VST)detector based on MAPS-technology. A continuation of the development of the MAPS pixel part of the STAR-HFT.
    (see here)
  • Forward / Backward vertex tracker (FST and BST)detector disks based on MAPS-technology. (see here)
  • Barrel-Tracker: TPC with GEM read-out, following the design of the ILD-TPC
  • Forward / Backward: possible GEM Tracker planes (FGT and BGT)

All technologies currently under investigation also provide low radiation length to keep multiple scattering and bremsstrahlung for the scattered lepton at a minimum.


Electromagnetic calorimetry:

The different electromagnetic calorimeters have different technologies to account for the different requirements.

  • Forward ECal: the requirements for the electromagnetic calorimeter are relatively moderate as its main function is to detect leptons from the decay of VMs and photons from dominately π0 decay.
    • currently the idea is to have a SciFi-tungsten powder sampling calorimeter
  • Barrel ECal: This calorimeter needs tp provide PID for the scattered lepton at high Q2 and leptons from VM-decays, the energy of these leptons will be determined from the tracking detectors. Further photons from π0 decays, the DVCS and BH process need to be measured.
    • currently the idea is to have a SciFi-tungsten powder sampling calorimeter
  • Backward ECal: This calorimeter needs to provide PID for the scattered lepton at Phase-I and II depending on the final tracking momentum resolution for Phase-II also the scattered lepton energy will be measured in the calorimeter, this might be especially important for the scattered lepton at low Q2. At Phase-II center-of-mass energies photons from π0 decays, the DVCS and BH process are in the acceptance of the backward ECal.
    • currently the idea is to have a PWO crystal calorimeter as the requirements in energy and angular resolution are most demanding.
      • for Phase-I the calorimeter can be moved closer if either the focus point for a projective geometry is chosen such that moving it by 1.5 m to 2 m does not cause any inefficiencies or if a non-projective design is chosen. Of course the trade of in angular resolution by moving the calorimeter closer needs to be still in the required limits.

Hadron Calorimetry

The forward and backward hadron calorimeters have different purpose and are needed at different phases of eRHIC. The resolution requirements are relatively moderate, therefore standard HCal techniques are totally applicable.

  • Forward HCal: This hadron-calorimeter is mainly for Phase-II eRHIC for jet physics in DIS and diffractive events. It also helps to define cleanly a rapidity gap.
  • Backward HCal: This hadron-calorimeter has to functions jet physics in DIS during Phase-II eRHIC and it will be important in the scattered lepton ID for low Q2 events, for which e/p from the ECal alone might

not give enough rejection power for hadrons.

π, K, p PID:

Positive identification of π, K, p is extremely crucial for the physics program of semi-inclusive physics.

  • Forward / Backward RICH: Due to the momentum ranges to be covered the RICH in forward and backward direction needs to be a dual radiator RICH, i.e. Aerogel and C4F10, following/extending designs from HERMES and LHCb. For RICH detectors with extended radiators any magnetic field still bending the track in the acceptance of the radiator needs to be avoided.
  • Barrel Particle ID: Particle ID in the barrel can have several different solutions. It could be done by a DIRC, following/extending designs from BABAR and PANDA, or a proximity focusing RICH, i.e. CLEO-III. In the case of a TPC as main Barrel tracker of course dE/dx can be combined with a high resolution ToF, as is currently done in STAR.

Other Detector elements

  • Roman Pots: the plan is to follow very closely in design and performance requirements, what is currently done in LHC and RHIC

the development for the following important detector parts is still ongoing

  • low angle ECal to detect very low Q2</sub> scattered leptons
  • the luminosity detector
  • the polarimeters
    • the electron polarimeter, which should sit as close as possible to the IR
    • local polarimetry to monitor the degree of longitudinal polarization for the hadron beam

Old page about the eRHIC dedicated detector design, this page is mainly outdated