Sample π-spectra from the Fall '04 polarized target run

The present detector configuration is optimized for π⁰ detection. More information will be posted soon. Missing energy spectra from polarized HD are shown in the accompanying figure HD(g,pi0) raw_incl.pdf for the two helicity states corresponding to photon and nucleon spins anti-parallel (h=3/2) and parallel (h=1/2). These histograms show inclusive results with two photons reconstructed to form π⁰'s with no cuts (designated raw in the figure). The data were taken during the first five days of running during which H and D spins were parallel, and reflect an energy bin of 340 ± 15 MeV and a c.m. angle bin of 90° ± 20°. The indicated empty cell contributions come from the unpolarizable nucleons in aluminum cooling wires embedded in the HD and in the Kel-F cell walls. The solid Monte Carlo line is the expected shape using a code from Harry Lee (impulse level only) to generate events from H and from D. The secondary peak at +135 MeV is evidently from a second π⁰ produced in the material of the target cell. The separation of the second (background) π⁰ peak is larger in the individual spectra of the two π⁰ photons and cuts on these yield the histograms shown in HD(g,pi0) Ediff 340MeV90cm.pdf (Figure 2 above).

Exclusive pion spectra, in coincidence with recoil neutrons, are shown in figures D(g,pi0n)340MeV fall04.pdf for the π⁰n final state and in HD(g,pi+n)340MeV fall04.pdf for the π⁺n final state. The empty cell contribution is less in the charged channel.