Commissioning of the GlueX detector is in progress in Hall D at the upgraded Jefferson Lab in Newport News, Virginia. Although the main mission of GlueX is to use a linearly polarized, 9 GeV photon beam to search for anticipated gluon-quark hybrid mesons, it is also an impressive factory for light mesons. The η(548) is of particular interest as it provides a laboratory to study isospin violation, and to search for laboratory evidence of dark sector particles as well as new, flavor-conserving sources of C and CP violation. Our experimental program will begin with the relatively common η→π+π-π⁰ branch (~23%) to better determine the light quark mass ratio.  A spin-off of the precise new Dalitz distribution for this branch will be improved direct constraints on C violating, P conserving interactions. Ultimately, we need to upgrade the forward calorimeter from lead glass to lead tungstate to search for lepto-phobic dark matter by the reaction η→γ+B→γ+(π⁰γ). This decay would appear as a bump in the Dalitz plot for the allowed but rare decay η→π⁰2γ.  The increased sensitivity of the lead tungstate calorimeter will allow us to extend searches for C violating, P conserving interactions to η→3γ and η→2π⁰γ.

个人简介：DaveMack, attended the U. of Iowa where he received a BA degree with majors in Physics, Astronomy, Mathematics, and Spanish in 1981. At the U. of Maryland, CollegePark, he received a Ph.D. in nuclear physics in 1987 for a measurement of (π+,2p) on ¹⁶O at SIN (now PSI) which firmly established quasi-deuteron dominance in the reaction mechanism for pion absorption. As a U. Alberta postdoc at TRIUMF during 1987-1990, he supported their wide-ranging program of nucleon and pion-induced measurements. Hired as a Hall C staff scientist in 1990, he led the teams that built the scintillating hodoscopes for the two Hall C spectrometers, also making major contributions to the beam current monitoring, spectrometer commissioning, and many early Hall C experiments. In 1993, he proposed the pion form factor program which led to several highly cited papers and demonstrated that Hall C could carry out precision L-T separations. In 2000, he co-wrote andeditedtheQweakprotonproposal,an experiment with unusual sensitivity to new parity violating interactions. He subsequently led the teams which built and shielded the experiment’s main Cerenkov detector, and for several years has been the coordinator of  Qweak’s 23 graduate students. He is a member of the APS, a Jefferson Lab Professor at ODU, taught Modern Physics one semester at CNC (now CNU), and has served on both the JLab User’s Group Board of Directors and the DNP program committee. He is a Glue X collaboration member and hasco-sponsored a proposal to exploit Hall D’s potential for precise measurements of eta and eta’ decays.