February 21, 2006 16:00 (Geneve time)

   Phone conference on Crystal channeling
   for diffractive physics

Participants:
   Mario Macri, Walter Scandale (CERN)
   Mike Albrow, Dick Carrigan, Nikolai Mokhov (FNAL)
   (First name?) Gurinovich, Victor Tikhomirov (BSU, Minsk)
   Yuri Ivanov, Alexander Denisov (PNPI)

1. A letter was sent to potential participants a month ago (see below)
   proposing to study potential benefit of crystals to increase the physics
   capability of the TOTEM and CMS experiments in the field of diffractive
   physics.

2. Mario started with a general description of this initiative:

 - this activity is a part of a new INTAS project approved recently for
   funding;
 - first important steps were made by Nikolai by extending the IP5 MARS
   model for tracking diffractive protons from IP5 to Si strip detector
   (Roman pot);
 - layout under consideration consists of a crystal and a Roman pot located
   at distances 175 m and 220 m from IP5,respectively;
 - double and single pomeron exchanges should be considered in the pp-event
   generators.

3. Nikolai decribed the model status and upcoming activities:

 - a very detailed MARS15 model of the IP5 region (+/- 500 m from the IP,
   lattice version 6.5), with all the machine and TOTEM components there
   (realistic 3-D geometries, magnetic fields etc) is ready for the studies;
 - it is based on the official low-beta optics files for nominal luminosity;
   Massimo Giovannozzi promised to provide optics tables for the TOTEM's
   beta* = 1540 m case within a few days; then it is a matter of a few weeks
   to implement them into the MARS model and test;
 - Valery Biryukov promised to provide the appropriate version of the CATCH
   code for implementation into the MARS model to model particle channeling
   in a crystal at 175 m; the concern is how to handle with CATCH a
   multi-projectile spray at the crystal in a broad energy and angular range;
   it can take several months to solve this problem;
 - we should decide on the interface to the TOTEM/CMS software: MARS can
   handle particles in the Roman Pots, but it seems preferable to leave it
   to the detector folks, with MARS providing a source term upstream of the
   detector, at z=220 m; this approach is currently used with the TOTEM group;
 - DPMJET is currently used as an pp-event generator at 14 TeV COM energy in
   the MARS model; double and single pomeron exchanges are there but, for
   the application considered, it is vital to benchmark it against PYTHIA
   and other models (e.g., developed at PNPI);
 - physics channels and requirements should be clarified.

4. Mike described detector considerations "CMS Use for Crystal Channeling"
   (transparensies attached).

5. Nikolai agreed with Mike that serious concerns are if the crystal
   preserves position and slope info and how precisely the crystal needs
   to be positioned with respect to the beam. He noted that the considered
   case is a single-pass situation, therefore an achieavable channeling
   efficiency is much lower than expected >90% one for the multi-pass
   case. Moreover, smearing by multiple Coulomb scattering can further
   reduce the desirable benefit.

6. Yuri I. discussed

 - a possibility to deflect halo particles away from the detector instead of
   deflecting diffractive protons to the detector;
 - details of diffractive proton beam and halo beam at the crystal and
   detector positions could help in choosing initial crystal parameters
   (Nikolai's comments: these are promptly available from MARS modeling).

7. Victor noted
 - on a possibility to use channeling effect for precise angle measurements.