We report on the search for heavy metastable particles that decay into quark pairs with a macroscopic lifetime (c{tau} {approx} 1 cm) using data taken with the CDF II detector at Fermilab. We use a data driven background approach, where they build probability density functions to model Standard Model secondary vertices from known processes in order to estimate the background contribution from the Standard Model. No statistically significant excess is observed above the background. Limits on the production cross section in a Hidden Valley benchmark phenomenology are set for various Higgs boson masses as well as metastable particle masses and lifetimes.

A search for the standard model Higgs boson is performed in 6.4 fb{sup -1} of p{bar p} collisions at {radical}s = 1.96 TeV, collected with the D0 detector during Run II of the Fermilab Tevatron. The final state considered is a pair of jets originating from b quarks and missing transverse energy, as expected from p{bar p} {yields} ZH {yields} {nu}{bar {nu}}b{bar b} production. The search is also sensitive to the WH {yields} {ell}{nu}b{bar b} channel, where the charged lepton is not identified. Boosted decision trees are used to discriminate signal from background. Good agreement is observed between data and expected backgrounds, and a limit is set at 95% C.L. on the section multiplied by branching fraction of (p{bar p} {yields} (Z/W)H) x (H {yields} b{bar b}). For a Higgs boson mass of 115 GeV, the observed limit is a factor of 3.5 larger than the value expected from the standard model.

The longitudinal beam dynamics in circular accelerators is mainly defined by the interaction of the beam current with the accelerating Radio Frequency (RF) stations. For stable operation, Low Level RF (LLRF) feedback systems are employed to reduce coherent instabilities and regulate the accelerating voltage. The LLRF system design has implications for the dynamics and stability of the closed-loop RF systems as well as for the particle beam, and is very sensitive to the operating range of accelerator currents and energies. Stability of the RF loop and the beam are necessary conditions for reliable machine operation. This dissertation describes theoretical formalisms and models that determine the longitudinal beam dynamics based on the LLRF implementation, time domain simulations that capture the dynamic behavior of the RF station-beam interaction, and measurements from the Positron-Electron Project (PEP-II) and the Large Hadron Collider (LHC) that validate the models and simulations. These models and simulations are structured to capture the technical characteristics of the system (noise contributions, non-linear elements, and more). As such, they provide useful results and insight for the development and design of future LLRF feedback systems. They also provide the opportunity to study diverse longitudinal beam dynamics effects such as coupled-bunch impedance driven …

This thesis presents a measurement of the dijet invariant mass spectrum and search for new particles decaying to dijets at CMS in 7 TeV pp collisions using data corresponding to an integrated luminosity of 2.875 pb{sup -1}. The measured dijet mass distribution is compared to QCD prediction from PYTHIA . It is required the pseudorapidity separation of the two jets to satisfy |Dh| < 1.3 with each jet inside the region of |{eta}| < 2.5. The observed dijet mass spectrum is fitted by a smooth function to search for dijet resonances. Since there is no evidence for dijet resonances, the upper limits at 95% Confidence Level (C.L.) on the resonance cross section are set. These generic cross section limits are compared with theoretical predictions for the cross section for several models of new particles: string resonances, axigluons, colorons, excited quarks, E{sub 6} diquarks, Randall-Sundrum gravitons, W' and Z'. It is excluded at 95% C.L. string resonances in the mass range 0.50 < M(S) < 2.50 TeV, excited quarks in the mass range 0.50 < M(q*) < 1.58 TeV, axigluons and colorons in the mass ranges 0.50 < M(A) < 1.17 TeV and 1.47 < M(A) < 1.52 TeV, and E{sub …