Yellow Report Detector Polarimetry-Ancillary

Working Group Status: June 15, 2020

Brief summary of the Polarimetry-Ancillary Working Group as of June 15, 2020

• Global
  • All systems are at a stage that drafting of the Yellow Report section can begin. An Overleaf document will be set up soon.

• Luminosity monitor
  • Location and preliminary layout of luminosity monitor exists - layout will be refined based on synchrotron radiation studies and beam pipe desing
  • Mature GEANT4 simulation exists
  • Event generation scheme validated by comparison to HERA data
  • Detector technology under study - PbWO4 too slow (and probably not radiation hard enough) to measure bunch-by-bunch. Tungsten powder/sci-fi detector (similar to sPHENIX concept) under study

• Compton polarimeter
  • Location of Compton at IP12 defined
  • Space is very tight and the trajectory of the laser, back-scattered photons, and scattered electrons places requirements on the beamline magnet apertures and sizes. This has been studied by two independent simulations - a summary of requirements is being collected and a discussion with the machine design group will be scheduled.
  • Rate studies indicate that a single pass (pulsed) laser will be sufficient (no cavity necessary). 1064 nm is perhaps adequate, but 532 nm provides reduced measurement times, requires less aggressive detector segmentation.
  • Event-generator level studies indicate a photon (electron) detector with vertical position resolution on the order of 100 um (50 um) is desirable to measure the transverse beam polarization.
  • Horizontal segmentation in the electron detector and a calorimeter for the photons will allow longitudinal (hopefully null) polarization measurements.
  • Bunch-by-bunch polarization measurements will require <10 ns time resolution. Diamond strips may be a possibility.
  • GEANT4 simulation under development - will inform detector technology choice.
  • Also need information on impact of wake field on the electron detector and synchrotron backgrounds.
  • Investigating longitudinal Compton close to detector IR

• Hadron polarimeters
  • Will use existing H-Jet and carbon polarimeters
  • Backgrounds will be challenging at high beam frequency - origins of these backgrounds under study via Monte Carlo
  • Possible issues with carbon target heating due to wake field - simulations underway
  • Verification of analyzing powers (and detector acceptance) for deuteron, helium-3 beams possible during remaining RHIC running. Breakup contributions can also be studied.