Thu, 23 Jun 2005
 
Subject: Urgent MDI questions to the detector concepts.

 FROM the Co-Chairs of the Worldwide Study of Physics 
      and Detectors for the ILC.

 MACHINE DETECTOR INTERFACE QUESTIONS WHICH THE ILC DETECTOR CONCEPT GROUPS 
 ARE ASKED TO ANSWER AS FULLY AS THEY CAN BEFORE SNOWMASS.
 
 These questions are urgent.  Concept groups are encouraged to give the
 best answers they can before Snowmass - as guidance to the decisions which
 the GDE wishes to make on the baseline machine design by the end of
 2005.  They have been prepared in close consultation with the 
 Machine-Detector Interface Panel of the WWS (P.Bambade, T.Tauchi and 
 M.Woods) and with the Working Group 4 conveners of the ILC Study 
 (A.Seryi, T.Sanuki, G.Blair).
 
 PLEASE REPLY - IF POSSIBLE BY BY 1 AUGUST - TO THE WWS CO-CHAIRS (BRAU,
 YAMAMOTO, MILLER)

If you find you cannot answer any of the questions, as put, please tell us 
why and give whatever relevant information you can.
 
 
 1.  What factors determine the strength and shape of the magnetic field in
    your detector?  Give a map of the field, at least on axis, covering
    the region up to +-20 m from the IP.  What flexibility do you have to
    vary the features of this field map?
 
 2.  Provide a GEANT (or equivalent) geometry description of the detector
    components within 10 meters in z of the IP and within a radial
    distance of 50 cm from the beamline.

 3. Would you mind if the baseline bunch-spacing goes to ~150 ns instead
    of ~300ns; with ~1/2 the standard luminosity per crossing and twice as
    many bunches?
 
 4.  For each of your critical sub-detectors, what is the upper limit you
    can tolerate on the background hit rate per unit area per unit
    time (or per bunch)?  Which kind of background is worst for each of
    these sub-detectors (SR, pairs, neutrons, muons, hadrons)?
 
 5.  Can the detector tolerate the background conditions for the ILC
    parameter sets described in the Feb. 28, 2005 document at
    www-project.slac.stanford.edu/ilc/acceldev/beamparameters.html ?  
    Please answer for both 2-mrad and 20-mrad crossing angle geometries.  
    If the high luminosity parameter set poses difficulties, can the
    detector design be modified so that the gain in luminosity offsets the
    reduction in detector precision?
 
 6.  What is your preferred L*?  Can you work with 3.5m < L* < 4.5m?  
    Please explain your answer.
 
 7.  What are your preferred values for the microvertex inner radius and
    length?  If predicted backgrounds were to become lower, would you
    consider a lower radius, or a longer inner layer?  If predicted
    backgrounds became higher, what would be lost by going to a larger
    radius, shorter length?
 
 8.  Are you happy that only 20mr and 2mr crossing angles are being studied
    seriously at the moment?  Are you willing to treat them equally as 
    possibilities for your detector concept.

 9.  Is a 2mr crossing angle sufficiently small that it does not
    significantly degrade you ability to do physics analysis, when
    compared with head-on collisions?
 
 10.  What minimum veto and/or electron-tagging angle do you expect to use
    for high energy electrons?  How would that choice be affected by the
    crossing angle?  How does the efficiency vary with polar angle in each 
    case?
 
 11.  What do you anticipate the difference will be in the background
     rates at your detector for 20mr and for 2 mr crossing angle?  Give
     you estimated rates in each case.
 
 12.  What is your preliminary evaluation of the impact of local solenoid
     compensation (see LCC note 143) inside the detector volume, as needed
     with 20mr crossing angle, on the performance of tracking detectors
     (silicon, and/or TPC, etc.)
 
 13.  Similarly, what is you preliminary evaluation of the impact of
     compensation by anti-solenoids (LCC note 142) mounted close to the
     first quadrupole?
 
 14.  Do you anticipate a need for both upstream and downstream polarimety
     and spectrometry?  What should be their precision, and what will the
     effect of 2 or 20 mr crossing angle be upon their performance.
 
 15.  Is Z-pole calibration data needed?  If so, how frequently and how
     much? What solenoid field would be used for Z-pole calibration?  Are
     beam energy or polarization measurements needed for Z-pole
     calibration?

 16.  Would you like the e-e- option to be included in the baseline, and
     if so what minimum integrated luminosity would you want?

 17.  What will be your detector assembly procedure.

 18.  What size is required for the detector hall?

 
 There are, of course, many more questions to be answered and studies made
 before the ILC CDR at the end of 2006.  The MDI group's report at
 (http://www.hep.ucl.ac.uk/~djm/MDIpanelreportJune05.doc) gives a fuller
 overview of the issues to be addressed.