PAC27 endorses GlueX

[Elton Smith <elton@jlab.org>]

Dear collaborators,

The PAC27 report on the 12 GeV upgrade is now public and accessible at
http://www.jlab.org/exp_prog/PACpage/PAC27/PAC27_review.pdf

The main conclusion is that "GlueX represents one of the key projects
requiring the JLab 12 GeV Upgrade. The PAC recommends adhering to the
original plan outlined in the pCDR. Possibilities for cost reduction
should be considered without compromising the proposed physics reach of
the experiment."  This is a very favorable endorsement of our physics
program and provide stimulus for the upcoming reviews and milestones.

For ease of reference I reproduce below some of the most important and
relevant sections to Hall D.

Cheers, Elton.


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Fourth Charge: Comment on the merits and drawbacks of possible alternate
equipment configurations. A variety of possible alternate equipment
configurations under consideration will be presented.  For each of these
configurations, identify the essential physics programs that it can
support roughly at the level of the equipment presented in the pCDR (as
enhanced by further design work since the publication of that document),
and for each identify critical physics reach that will be lost relative to
the design-enhanced pCDR equipment.

Hall D, GlueX Issues: The merits of photoproduction versus
electroproduction for the spectroscopy of light mesons and baryons, the
option of locating Hall D behind Hall B, the importance of 12 GeV beam
energy for the success of the experiment, the need for a close
collaboration between Hall B and Hall D staffs.

Conclusions: GlueX represents one of the key projects requiring the JLab
12 GeV Upgrade. The PAC recommends adhering to the original plan outlined
in the pCDR.  Possibilities for cost reduction should be considered
without compromising the proposed physics reach of the experiment. A close
collaboration between Hall B and Hall D throughout the instrumentation and
operation phases is highly recommended.

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Second Charge: Review the new research programs that are under
consideration for being highlighted in the executive summary of the CDR.
Do they represent compelling science that must be done to advance our
understanding of nuclear physics? Have we omitted key science initiatives
that should be used as primary motivations for the Upgrade?

1.A.1 Spectroscopy (light mesons and baryons)

The inclusion of baryon spectroscopy as a research emphasis for the GlueX
experiment is a clear improvement. The excellent hermeticity of this
detector for charged and neutral final state particles is a necessary
pre-condition for the reliable partial wave analysis of lowmomentum
baryonic systems, especially those involving small amplitudes.

The CLAS12 detector will provide very useful measurements of transition
form factors for particular hadron resonances at high Q. The improved
capabilities of an upgraded CLAS detector should be emphasized strongly.
This topic should find its place in 1.A.2 Quark structure and nucleon
excitations.



Elton Smith
Jefferson Lab
elton@jlab.org
(757) 269-7625