Data Taking Strategy

The FPD is designed to be a sub-detector of DØ and will be well-integrated into the DØ trigger framework. Due to the relatively small number of channels (about 2000 compared to hundreds of thousands for other sub-detectors), this detector will have a negligible effect on the event size. It should be read out on every event since any standard type of physics process below mass threshold can be produced diffractively.

It will also be necessary to have a few dedicated triggers which demand tracks at the trigger level. Dedicated triggers will be required for

• Diffractive jet production. The low jet cross section is too large to have an unprescaled diffractive jet trigger unless a track requirement is explicitly included. A diffractive jet trigger would combine a low cluster with a track in a p or spectrometer.
• Double pomeron exchange. This will require tracks in p and \ spectrometers, as well as an cluster for the hard double pomeron exchange case.
• Inclusive single diffraction. This prescaled trigger will be necessary to understand the operation of the FPD, as well as for soft single diffraction studies and ratios of diffractive jet to inclusive diffraction, which allows for the cancellation of many systematic uncertainties.
• Elastic scattering. This requires tracks in diagonally opposite spectrometers. A sample of elastic events should be accumulated each run for alignment purposes and luminosity monitoring. These events should be quiet in all the other detectors and could be written at a high rate without requiring much bandwidth.

To minimize the bandwidth for these dedicated triggers, the capability to cut on at Level 1 is essential (See Sec. 4.2.2). This allows the different triggers to only accept tracks in the kinematic range of interest. In addition to the requirement of a p or \ (and in some cases jets), the dedicated triggers must include elements to reject multiple interaction and halo backgrounds, which will be discussed in the following section prior to the discussion of trigger rates and data samples.

Although the bulk of data taking will be done during typical collider running conditions, it may be advantageous to take occasional low luminosity runs or special runs for systematic studies. It will be useful to map out the acceptance contours and a few dedicated runs are typically optimal for high cross section and alignment studies.