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Dear all,<br>
we just finished two-hours of discussion with Bob, Rolf and Patrizia
(present me, Elton and Stepan).<br>
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.<br>
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.<br>
Here is the list of what I remember. Elton and Stepan will complete
the list with what I missed.<br>
Cheers<br>
Marco<br>
<br>
- <b>civil construction</b>: 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).<br>
<br>
- <b>Physics case</b>: we really need to work more on that putting
in the context of other experiments and carefully compare the
BDX@JLab <br>
to show the big advantage wrt other experiments/techniques.<br>
here is a list of possible actions:<br>
-- discuss the current activity in Direct Detection at low masses
and show BDX vs. other experiment reach and kinematic coverage
(e.g. supeCDMS);<br>
-- 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, ...<br>
-- provide consistent reach plots (same model parameter values, same
variables, ...) to minimize the confusion<br>
-- 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. <br>
-- convince that the experiment has unique potentialities (new
technology used, measurement of many different channels at the same
time, consistency checks, systematic checks ...)<br>
Just mentioning that other facilities will run a similar program
does not work: we need to demonstrate that we will do much better!<br>
<br>
-<b> EOT and reach</b>: 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.<br>
<br>
- <b>Collaboration and funds</b>: 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.<br>
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.<br>
<br>
- <b>Background</b>: there was a lot of discussion about <b>muons</b>
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.<br>
-- muons: run different physics lists to be sure that they are
correctly generated and parametrized; <br>
-- timing: we need to clearly state that time coincidence with the
CW beam structure does not help to cut any discussions at the origin<br>
-- cosmogenic bg: requires to be tuned to the real measurement (see
below)<br>
-- shielding optimization: we need to run simulation and check how
heavy shielding that might replace the 10m dirt is affecting the
civil costs<br>
<br>
- <b>Understanding the cosmic bg measurement with BaBar crystal at
LNS is mandatory</b>: 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. <br>
<br>
<br>
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