[Moller_simulation] MOLLER sim. telecon. extra meeting

Peiqing Wang pqwang at jlab.org
Tue Nov 20 18:40:18 EST 2012

Hi KK and all,

We had a phone conference this afternoon and exchanged some thoughts
about my recent work.  There were some updates and additional comments
on the slides, see

The PREX stack detector simulation is a very useful reference for our
detector study. However, I have a quite different purpose in my
simulation. My purpose was not to optimize "shower-max" detector;
instead, it was to find out an optimized pre-radiator.  This was
motivated by the Qweak experience.  We had lots of unexpected soft
backgrounds in Qweak, which were about 10% of our signal size. With a
set of pre-radiators, we were able to suppress them down to an
acceptable level. In our moller detector simulation, therefore, I tried
to find the optimized pre-radiator thickness. These pre-radiators can be
used as optional "add-on" components for the thin quartz detectors. In
case we also have large soft background (I naively imagine that could be
potentially huge), we could easily put them on, as we did for Qweak. The
"single pre-radiator" version of "shower-max" detector in my simulation
is indeed a side product of this effort.  From the slide #11, the
"single pre-radiator" detectors can reach an excess noise level of ~3% -
8% for 4-10 GeV beam, which looks reasonably acceptable for such a
simple design.

It was suggested in the meeting that the optimization of shower-max
detector itself should be listed as a small simulation project. Although
the PREX stack detector simulation was performed at a beam energy of
~0.85 GeV that was not comparable to our application of wide beam energy
range, it could still be the most useful resource for our shower-max
detector simulation.


On 12-11-17 03:18 PM, Krishna Kumar wrote:
> Hi, Folks. I will not be able to call in on Tuesday since I will be out of town. However, I gather that you will be discussing Peiqing's slides that were posted on the previous meeting page. I will take a detailed look at the results for the thin quartz and perhaps send further comments. However, I wanted to make sure that I immediately communicate our main idea for the "shower max" detector that is to sit behind the  main detector rings:
> The idea is to have a sandwich of quartz and tungsten. This is much better than having a single pre-radiator. Piotr Decowski (cc'ed here) did such a study for a potential sandwich detector for PREX. The optimization of the ratio of tungsten thickness to quartz thickness and the number of such layers is the key to the required MC study.  The goal would be to ensure that 3 to 8 GeV particles will have at least 20% resolution. Then the excess noise will be below 2%. I would not worry too much about 1 to 3 GeV particles in this optimization. They are much rarer and have a much lower figure of merit (analyzing power). Hopefully the optimization will show that we need somewhere in the range of 10 to 15 X_0 total thickness and no more. This will reduce the relative pion background by a factor of 3 compared to thin quartz, which is another determining factor in this optimization. If the optimization is relatively flat for a range of thicknesses, then the thinnest solution should be chosen. 
> I seem to recall that our simulations showed that one can get about 35%/Sqrt(E) for 7 or 8 layers of alternating 1 mm tungsten and 10 mm of quartz (or maybe it was 5 mm?). Piotr might be able to quickly find a technical note where we did the optimization for PREX. We ultimately decided not to use it because the resolution was far worse than for thin Quartz at 1 GeV. But it will be much better for 3 GeV and up. 
> BTW, Piotr should be put into the simulation emails. I am sure he would like to call in when possible.
> Cheers, KK
> On Nov 15, 2012, at 1:02 PM, Juliette Mammei <crowder at jlab.org> wrote:
>> Hey guys,
>> Thanks to all who responded to the Doodle poll.  It looks like the best 
>> time for the extra meeting is next Tuesday, November 20th at 4pm EST.  
>> I'll send an announcement with an agenda by Monday afternoon.
>> Talk to you later,
>> Juliette
>> On 13/11/2012 1:44 PM, Juliette wrote:
>>> Hey guys,
>>> The simulation meetings have been taking longer than expected, and we 
>>> have had to put agenda items off until the next meeting several times, 
>>> including this last time.  Also, there are some special scheduling 
>>> issues coming up, including the Qweak collaboration meeting this week 
>>> and Thanksgiving.  So, we would like to have an "extra meeting" 
>>> between now and our next regularly scheduled meeting time.  I have 
>>> created a Doodle poll to set up the time for that meeting:
>>> http://www.doodle.com/mrgmnabip6iisskm
>>> Please fill out times when you can attend this special meeting. Note 
>>> that you can choose your time zone in the upper right.  The first 
>>> couple times should be tomorrow (Wednesday) at 3pm and 4pm EST, which 
>>> are actually not ideal for me.
>>> At this meeting we will also consider having weekly meetings with set 
>>> agendas, possibly with "results" one week and discussion about 
>>> development in the alternating week.
>>> Talk to you later,
>>> Juliette
>> -- 
>> Dr. Juliette Mammei
>> Assistant Professor
>> Department of Physics and Astronomy
>> University of Manitoba
>> Winnipeg, Manitoba
>> R3T 2N2 Canada
>> Office: 1-204-474-6195
>> _______________________________________________
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