[Halld-physics] Solenoid - field and physics

[Eugene Chudakov]

Hi,

today we ran through a review of the solenoid project, see:

http://www.jlab.org/Hall-D/reviews/Solenoid_Magnet_Internal_Review_Nov09/

They gave a recommendation to show the physics impact of
running at 80-90% of the planned field (2.2T at 1500A).

The point is that the magnet may not reach 1500A. Before,
it ran at not more than 1250A. Also, it turns out that the full 
axial force on coil 2 changes sign at 1350A, which might become a problem.
This magnet is not expected to quench, but still, if a piece of 
conductor  moves it may generate a voltage which would look
like quenching to the control system, which would power 
the magnet down. Other problems may occur.

Before the review we discussed this question with Curtis. It seems
that no hard numbers have been collected in one place to be used
in such occasions.

We must provide this info before the next Lehman review
(February?). We should assume the detector design finished
and not adapted to a lower field. 
Here I list several possible impacts to consider:

a) Higher EM background close to the beam. Result - running
    at lower luminosity, losses of small angles.

b) Missing mass resolution. Let us take 3-4 reactions and estimate
    the contamination from reactions with an additional pion (unseen).

c) Particle identification (pi/K/p) from TOF and kinematic fitting.
    BG for events with charged kaons and no missing particles.

d) The ultimate parameter is the sensitivity to an exotic wave
    at a certain confidence level, at least for one "gold" reaction.

While a)-c) are simple, c) is complex, but quite important, 
since similar questions will be asked in future.

Any numbers or suggestions? Who would work on this?

Eugene
------------------------------------------------------
Eugene Chudakov
http://www.jlab.org/~gen
phone (757) 269 6959  fax (757) 269 6331
Thomas Jefferson National Accelerator Facility
12000 Jefferson Ave,
Newport News, VA 23606 USA