Detector Considerations EIC

1
Detector Considerations _at_EIC
Rolf Ent, eA Meeting _at_ BNL, 05/07/05
Here, we will only discuss a multi-purpose
high-luminosity ep detector, not a dedicated
lower-luminosity ep/eA detector as suggested by
Allen Caldwell et al. At present, potential
high-luminosity eA studies have not been
integrated into these considerations yet, we hope
to start the MC simulations for eA after this
meeting! The following slides are only a working
document for discussions, they are the summary
of the last EIC Monte Carlo Group meeting,
presently only drafted by Antje, Abhay, and me.

• Open Charm Production
• Electron Detection
• Flavor Decomposition
• Questions/To Do

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Detector Considerations _at_EIC

• Open Charm Production
• Dominant reaction mechanism through glue at small
  x ? e/ion momentum mismatch not so relevant and
  created nearly at rest ? Decay products at large
  angles. Need to determine angle range.
• Background reduction critical issue ? requires
  lt100 m vertex resolution ? drives vertex detector
• Decay products have typical momenta between 0-2
  GeV ? Need good particle id in this region and
  good track capability in large rate region ? GEM
  layers as TPC would work, use dE/dx plus TOF of
  hodoscope (with 100 ps timing resolution, 3.2
  meters gives 3s p/K separation)
• HERA typical momentum cutoff of 5 GeV, studies
  show can push down to Field (in Tesla) of
  Solenoid. STAR has only 0.5 T field and lower
  cut-off of 0.4 GeV ? Need low T (about 0.5)
  magnetic field in central region.

3
Detector Considerations _at_EIC - II

• Electron Detection
• Do we need momentum determination through
  magnetic field or can one simply use this to
  determine charge-sign and rely on high-resolution
  calorimetry (PbWO4?). Needs to be determined from
  simple kinematic arguments and (as quantitative
  example) from QCD analysis.
• A solenoid has implications for the highest
  luminosity one can reach in the IR, as it acts as
  a (de-)focusing element for the electrons/ions.
  Could one use a torus instead? For a solenoid,
  the lower the field (0.5T?) the better, should
  we only cover the IR of relevance (10-30 cm?). In
  general reduce ?B.dl along beam axis.
• How can we accomplish small angle electron
  scattering? Is placing E.M. calorimeters all
  around the ring o.k., like in the Muon/g-2 ring?
  What x-Q2 resolution/coverage?

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Detector Considerations _at_EIC - III

• Flavor Decomposition
• Need comfortable z cut (gt 0.2?) for reliable
  flavor decomposition ? This gives pions/kaons of
  a few GeV or higher. What pion/kaon momenta
  range?
• Probably do need reasonable momentum resolution
  and charge-sign determination ? is a larger field
  (solenoid or other) needed outside the central
  region? What resolution is needed?
• DES processes likely drive hadron resolutions
  required.
• Analysis with purity matrices should show to what
  extent p/K identification is a requirement (note
  that it is likely that DES processes drive the
  p/K requirements).
• Urgently need momentum/angle distributions of
  particles associated with physics processes of
  interest!!!

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Detector Considerations _at_EIC - Questions

• Can one get away with a small length inner vertex
  detector to only cover the bunch crossing?
• Does one need a composite field structure (0.5T
  in inner region, step function more radially out?
  PHENIX).
• Is PbWO4 and a 0.5 T solenoid field sufficient
  for electron resolutions? Could we use a toroidal
  field?
• What momentum resolutions are required for
  few-GeV/c pions/kaons? What field would be needed
  for this?
• Is a gap in p/K identification acceptable for the
  intermediate hadron momenta (2-5? GeV/c)?
• Are EM calorimeters all around the ring
  sufficient for very-small angle electron
  detection?
• What are the implications of a 100 mr crossing
  angle? (relevant for ELIC only)