[BDXlist] BDX presentation to JLab directorate - SUMMARY -

[Marco Battaglieri]

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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