/ and Jets at Cdf

Events with signatures involving large missing transverse energy (E T /) are among the quintessential search modes for R-parity conserving supersymmetry. CDF has conducted two recent analyses for supersymmetry which use E T / and jets. The E T / and monojet signature is employed to determine process independent limits for the production of new physics beyond the Standard Model and then applied to models of spontaneous breaking of supersymmetry to determine limits on the supersymmetry breaking parameter and the gravitino mass. Direct searches for scalar top and scalar bottom quarks within the framework of supersymmetric models are performed using a signature of E T / and two heavy flavor jets. Since the data is found to be consistent with Standard Model expectations, limits are determined in the mass planes m(˜ χ 0 1)−m(˜ t 1) and m(˜ χ 0 1)−m(˜ b 1). Several theories beyond the Standard Model 1 contain light, neutral particles which have extremely small interaction cross sections. These particles typically pass through detectors unobserved producing a signature with an imbalance in transverse energy (E T) quantified as missing transverse energy (E T /). CDF has performed a search for physics beyond the Standard Model by examining events with large E T / and a high E T jet. 2 Trigger induced systematic effects are reduced by increasing the 35 GeV trigger threshold to E T / ≥ 50 GeV. A high E T jet is obtained by selecting events which contain a leading jet with E T ≥ 80 GeV. The effects of jet energy mismeasurement and additional instrumental backgrounds are reduced by requiring that the angle between the E T / direction and the nearest jet satisfy ∆φ(E T / , jet) ≥ 90 •. Events with identified electrons or muons are removed. The E T / spectrum and the estimated backgrounds after all selection criteria have been applied are shown in the left plot of Figure 1. The number of observed events is 379 while 380 ± 129 background events are determined. The 95% confidence level (CL) upper limit for the product of acceptance and cross section for new physics as a function of E min T / , the E T / threshold, are shown in the top right plot of Figure 1. To determine a process specific cross section limit, the pertinent acceptance is calculated. Theories in which supersymmetry is broken via …