Possible New Experimental Program in Baryon Spectroscopy Utilizing the MIPP Facility at Fermilab

Michael E. Sadler

Department of Engineering and Physics,

Abilene Christian University, Abilene, TX

Tuesday, January 25, 2014

3:30 p.m., Room 104, Physics Building

Refreshments

3:15 p.m., Room 104

Abstract:

The need for a rejuvenated program in pion-nucleon (πN) and kaon-nucleon (KN) scattering will be presented and possible facilities for doing the experiments will be discussed. The MIPP (Main Injector Particle Production) installation at Fermilab will be highlighted, as the accelerator, beam line and detector already exist. Magnet controls are being implemented to make available pion beams as low as 1 GeV/c. The utilization of a Time Projection Chamber to measure outgoing charged particles will make it possible to measure elastic scattering (πN → πN) and multiple pion production simultaneously. Experiments in strangeness production (e.g., π − p → K 0 Λ ) can also be made, all with one overall normalization for the luminosity. Final states involving a single neutral

particle (e.g., a neutron, π0, or η) in the final state can be reconstructed using missing mass techniques. These measurements are important in their own right, as tabulations by the Particle Data Group of the properties (masses, widths, pole positions, and inelasticities) of N* and Δ* resonances, the excited states of the nucleon, have been determined almost exclusively from partial-wave analyses of πN scattering data. Intense efforts are underway to study these resonances via coupled-channel analyses of photo- or electro- production, but accurate πN data are still needed because the observed particles are the result of hadronic decay. A primary goal of the combined programs is to investigate the so-called "missing states" of relativistic quark models of the baryon spectrum. In general, these missing states are predicted to couple weakly to the πN channel but may become more apparent through the formation reactions available at MIPP.