Other Physics Topics

There are many other physics topics besides hard diffraction that will be accessible with the FPD. These include

• Inclusive double pomeron. This process has not been observed at the Tevatron and there are large uncertainties in the cross section. Recent predictions of shadowing effects [29] can be tested as well as the pomeron flux factor. Inclusive double pomeron interactions are an ideal place to look for glueball production, and the clean event topologies would make them easier to detect.
• Centauros. The observation of anomalous cosmic ray events [30] has not been adequately explained. It has been proposed that centauros may be produced diffractively, which would explain why they have not yet been observed by collider experiments [31]. The FPD would allow the search for centauro production in diffractive events.
• High-|t| elastic scattering. There is little data on elastic scattering except at small momentum transfers, so the FPD would be in a unique position to map out the |t| dependence of the elastic cross section up to a few GeV.
• Inclusive single diffraction. Many properties of inclusive single diffraction have been measured at the Tevatron [21], but there is little data on the momentum transfer dependence of these results. The FPD will allow us to make significant contributions to the understanding of soft as well as hard diffraction.
• Comparison of results with different tags. Combining rapidity gap tags and proton tags will also be an interesting study to see how often the proton is associated with a rapidity gap and vice versa. Complete overlap is not expected due to the super-hard pomeron, which would not generally give a rapidity gap in the DØ detector, and also due to diffractive excitation of the proton.