sPHENIX cold QCD topical group

[David Morrison <morrison AT bnl.gov>]

Hi all,

I've had a chance to read the draft LOI.  Nice work, everyone, getting
the document to its current state.  I've compiled a long list of
line-by-line comments, but I think it's more productive to start with
some general observations.  I'll save the details for a later email.

Something that seems not to be widely known - partly because we've asked
ALD Berndt Mueller to provide us this direction in writing - is that
he's no longer asking for a cost estimate to accompany the LOI.

That un-request by the ALD could have a ripple effect on how we present
the LOI.  If you're going to cost something realistically, you need to
be concrete about choices.  It's tough to produce a detailed cost
estimate of "forward tracking system" – you want to be able to cost N
stations of a particular technology.  The estimate would look different
if it were M stations of a different technology.  The current document
follows the technological choices of the 2013 LOI closely – GEMs for
forward tracking, DIRC for barrel PID, etc. – be as we're not being
asked to deliver an estimate, we might broaden the discussion to
indicate various options.  There's some of that discussion in the
current draft, but it could be fleshed out.

Having just argued that a discussion of options complicates costing, I
still think it's in our interest to produce a cost estimate, but maybe
on a time scale of December or so.  Perhaps in time for the
collaboration meeting.

There isn't yet an executive summary.  Who will be writing that?  That
will be a rather important for establishing the aim of the document.
The ALD specifically didn't provide any costing guidance in the charge,
so we should carefully describe the approach we're taking.  Is this
intended to be a conservative update of the 2013 LOI?  Are we describing
a detector that does EIC physics at minimal cost?  Maximizes re-use of
sPHENIX components?  Without cost guidance, we could describe options
that replace some sPHENIX components but would incur significant cost
(presumably so that we would get improved capabilities).  We could
describe this in the executive summary and, in more detail, in an
introduction.  We could look at the cost scale of detectors for other
new machines (RHIC, Tevatron, ...), or use other insights, to describe a
plausible cost scale for sPHENIX/EIC and then see what that implies.

The document needs a table of specific guidance from C-AD on projected
eRHIC capabilities for the timeframe relevant to the charge.  That would
need someone to talk with Ferdinand Willeke and/or Wolfram Fischer.

There are a number of developments in sPHENIX in the last year or so
that could be used to advantage.  For instance, there has been extensive
engineering of the support cradle and the flux return doors.  It may
seem pretty far removed from TMDs, but the concept is that those doors
slide into place, instead of being hinged.  That might help with
concerns about the longitudinal space constraints due to the location of
the final focusing quads.  Or that we're going to be buying 100% spares
of the MVTX staves.  That might mute criticism that the MVTX staves will
be radiation damaged by the end of the SPHENIX program.

I think it would help to plan a writing workfest – in person or virtual
– to work toward finalized the document.

Cheers,
Dave

-- 
David Morrison  Brookhaven National Laboratory  phone: 631-344-5840
                Physics Department, Bldg 510 C    fax: 631-344-3253
                          Upton, NY 11973-5000  email: dave AT bnl.gov