BoNuS meeting

[Sebastian Kuhn <skuhn@odu.edu>]

BOund NUcleon Structure Working Group
Today we had a brief meeting to get organized. After a short report on the PAC 
recommendation ("we'd like to see the proposal" - I still haven't gotten the 
Theory Advisory Committee report! ROLF!!), we looked at the main issues we need 
to work on and the rather tight time schedule to accomplish them (and nearly 
despaired ;-)

Schedule: We need to present our proposal to the CLAS SoN (Structure of the 
Nucleon) PWG (Physics working group) at the next CLAS collaboration meeting, 
beginning October 17. In order for the proposal to be approved as "CLAS 
collaboration proposal", we need to provide a draft for the SoN to review BEFORE 
the meeting (probably late September). I will ask Mauro Taiuti, head of the SoN 
working group (hello Mauro!) to set up a review process and let us know what the 
deadlines will be.

Meanwhile, we have formed 3 preliminary working groups to tackle the main issues 
we need to address for the proposal:

Group 1) Detector design. Contact: Thia Keppel. Members: Thia, Rolf Ent, Stepan 
Stepanyan, Ioana Niculescu, and maybe Kim Egiyan. Technical advice from Stan 
Majewsky, Howard Fenker, and Fabio Sauli. Tasks:
i) Draw up a "strawman" design with all ingredients specified, including 
dimensions, materials and thicknesses, number and orientation (and resolution) 
of channels. Target chamber and readout boards/cables.
ii) Send this design to the Simulations group (2), including the existing MC for 
the protons.
iii) Discuss alternative designs, e.g. low-pressure wire chambers plus Si strip 
detectors (NIKHEF recoil detector). Also, do we want to increase the gap size of 
the first layer with hopes of getting some directional information (or at least 
a better energy measurement/particle ID) for the protons?
iv) After feedback from simulations, iterate and optimize.
v) Cost and work effort estimate.

Subgroup 1a): Electronics. Contact: Marco Ripani. Members: Genova group.
i) After the number of channels becomes known, develop a first design for the 
readout and DAQ electronics, obtain cost estimates.
ii) Check whether we can use the backwards (blinded) CLAS DC channels (ADBs and 
TDCs) to thread the recoil detector into the CLAS CODA DAQ system. What else do 
we need? (cables, delays, HV supplies...)

Group 2) Simulation. Contact: Sebastian Kuhn. Members: Sebastian, Alexei 
Klimenko, Will Brooks, possibly Bi Tao Hu (?), others??? (urgently needed)
i) Write simulation code for the D(e,e'p_s)X reaction inside the target, follow 
both proton and electron to the exit of some "internal cylinder", hand off the 
electron to CLAS GSIM code to simulate resolution (momentum and vertex!) and 
acceptance. Include multiple scattering and energy loss for the proton in the 
target and recoil detector and parametrize information (on particle ID, momentum 
and direction) we can get from the GEMs to get overall resolution in missing 
mass/Bjorken-x.
ii) Based on realistic estimates of count rates and backgrounds, optimize 
parameters including target density, length and overall running time. Iterate 
with group 1)

Subgroup 2a): Estimate singles rates for protons, deuterons and pions and the 
likely contamination of our D(e,e'p_s)X signal from these sources (how do they 
differ in their signals?). THIS NEEDS LOTS OF HELP! Maybe we can ask Blaine 
Norum for some of the code/experimental results on deuteron threshold 
disintegration that he presented to the PAC.

Subgroup 2b): Moeller backgrounds. Contact: Volker Burkert.
Once we have a design for the target parameters, Volker will ask the UVa group 
(Cole Smith) working on the DVCS solenoid to run simulations of the Moeller 
background for our luminosity and geometry.

Group 3) Physics. Contact: Wally Melnitchouk. Workers: Wally, Misak Sargsian, 
Claudio Ciofi degli Atti (?), Sabine Jeschonnek.
i) Identify competing processes (e.g. target nucleon fragmentation) and estimate 
their contribution.
ii) Study possible distortions of the spectator picture, e.g. through Final 
State Interaction.
iii) Collect full range of competing theoretical expectations for off-shell 
effects and other modifications of convolution picture.

We will meet again in 2 weeks (July 30th), Tuesday AFTERNOON at 2:00 p.m. (NOTE 
DIFFERENT TIME!) in Room B101 CC. By that time, hopefully we have first reports 
from all groups. I will be gone for 3 weeks after that, but hopefully somebody 
else can run the next meeting. We are planning to meet every other week at 2:00 
p.m. from now on (2 meetings in August, 2 more in September before we need to 
have a draft proposal).

- Sebastian