[BDXlist] BDX presentation to JLab directorate - SUMMARY -

[Elton Smith]

Hi Marco,

Thank you for the nice summary.

I looked back at the documentation on shielding muons for Hall D. See 
document
Shielding Basis for Hall D Complex. Technical Report JLAB-TN-08-03, 
particularly p. 12 and Fig 5.
Photon Commissioning Rate Estimat<br> <br> <br> <br> 
https://jlabdoc.jlab.org/docushare/dsweb/Get/Document-33207/08-033.pdf

The conclusion was that we needed 10 m of Fe (7800 g/cm2) to shield the 
muons, or 233 ft (71 m, ~12000 g/cm2) of dirt. This last estimate seems 
a bit extreme, but depends on the assumed density of dirt.

I am told that our GEANT simulations, muons range out much sooner, but 
this should be checked. For an initial test, I would suggest simply 
generating 11 GeV fixed energy muons at the center of the beam dump and 
see where they range out in the current geometry. In any case, at the 
present distance it seems like just dirt may not be adequate.

Cheers, Elton.


On 3/24/16 6:22 PM, Marco Battaglieri wrote:
> Dear all,
> we just finished two-hours of discussion with Bob, Rolf and Patrizia 
> (present me, Elton and Stepan).
> The discussion has been very thorough with many questions and 
> interruptions. Overall I would say it was good to have them aware 
> about the proposal and the extensive ($1M) infrastructural cost that 
> (only) JLab could cover.
> During the discussion some issues were raised. Some of them reflected 
> the early stage in the proposal process we are and will be worked out 
> in the future weeks. Other are more serious and it was good to have 
> them expressed before to go in front of the PAC.
> Here is the list of what I remember. Elton and Stepan will complete 
> the list with what I missed.
> Cheers
> Marco
>
> - *civil construction*: they were very happy to know the cost 
> ($1.1-1.2M direct costs) and that this figure is realistic. They were 
> very cautious but started discussing where money could be taken from 
> (good sign!). Money is obviously an issue but I had the impression 
> that it is their issue (we made very clear that we are not chasing 
> money for infrastructures at JLab).
>
> - *Physics case*: we really need to work more on that putting in the 
> context of other experiments and carefully compare the BDX at JLab
> to show the big advantage wrt other experiments/techniques.
> here is a list of possible actions:
> -- discuss the current activity in Direct Detection at low masses and 
> show BDX vs. other experiment reach and kinematic coverage (e.g.  
> supeCDMS);
> -- find the weak points in the extraction of limits  from previous 
> experiments (LSND and E137) and translate them in some strong 
> statement: not show the limits derived by electron measurement in the 
> plot that shows the Chi-Nucleon scattering, ...
> -- provide consistent reach plots (same model parameter values, same 
> variables, ...) to minimize the confusion
> -- visible vs invisible scenario: how limits change and why need to be 
> explain in a clear and simple way. In other world: the model 
> dependence of all the exclusion plots need to be defined and explained.
> -- convince that the experiment has unique potentialities (new 
> technology used, measurement of many different channels at the same 
> time, consistency checks, systematic checks ...)
> Just mentioning that other facilities will run a similar program does 
> not work: we need to demonstrate that we will do much better!
>
> -*EOT and reach*: Rolf mentioned many times that 10e22 is not 
> realistic (Bob said that 1 PAC year corresponds to few 10e21 EOT): we 
> need to tune all our reach plots to this value, may be increasing the 
> length of the detector and the measurement time to recover the missing 
> factor of 2-3. We should also check the allocated beam time to Moeller 
> and Solid (and other long-running) expes in Hall-A to check weather 
> BDX could run parasitically with them.
>
> - *Collaboration and funds*: the estimated cost of the detector  is 
> ~$1M (considering that the crystals will be provided for free): how we 
> think to manage and share the costs?  local funding agencies (INFN, 
> UK, MRI)? MRI? NSF funds? Not urgent but we need to be prepared for 
> such discussion.
> It would be good to have in the collaboration some HEP-involved 
> institutions to access money from a different pocket than DOE-NP: this 
> would be very positively considered by the Lab. It will also good to 
> have BDX explained to a vast audience since Bob mentioned that he will 
> ask for what DOE representatives think about and he would like to have 
> them aware of what he is talking about.
>
> - *Background*: there was a lot of discussion about *muons* produced 
> in the dump and how many will reach the detector. We need to start 
> running extensive simulations of the dump asap to include also the 
> obvious bg to have convincing arguments (they were much less worried 
> about n and gamma that we scrutinized more). Also muon sky-fall may be 
> an issue: need to be investigated with the realistic 
> geometry/materials of dump and environment.
> -- muons: run different physics lists to be sure that they are 
> correctly generated and parametrized;
> -- timing: we need to clearly state that time coincidence with the CW 
> beam structure does not help to cut any discussions at the origin
> -- cosmogenic bg: requires to be tuned to the real measurement (see below)
> -- shielding optimization: we need to run simulation and check how 
> heavy shielding that might replace the 10m dirt is affecting the civil 
> costs
>
> - *Understanding the cosmic bg measurement with BaBar crystal at LNS 
> is mandatory*: the proposal can not be submitted if we do not 
> understand prototype data taken  without overburden (current 
> configuration, last LNS floor) and with (configuration in the original 
> BDX location). This is probably the most serious issued raised in the 
> discussion. We need to derive rates vs thresholds asap including all 
> the info from  the veto and compare to simulation to extrapolate to 
> the real experiment.
>
>
>
>
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