We present a search for a Higgs boson decaying to two W bosons in pp collisions at √ s = 1.96TeV center-of-mass energy. The data sample corresponds to an integrated luminosity of 3.0 fb −1 collected with the CDF II detector. We find no evidence for production of a Higgs boson with mass between 110 and 200 GeV/c 2 , and determine upper limits on the production cross section. For the mass of 160 GeV/c 2 , where the analysis is most sensitive, the observed (expected) limit is 0.7 pb (0.9 pb) at 95% Bayesian credibility level which is 1.7 (2.2) times the standard model cross section.

We present a new measurement of the inclusive forward-backward tt production asymmetry and its rapidity and mass dependence. The measurements are performed with data corresponding to an integrated luminosity of 5.3 fb −1 of pp collisions at √ s = 1.96 TeV, recorded with the CDF II Detector at the Fermilab Tevatron. Significant inclusive asymmetries are observed in both the laboratory frame and the tt rest frame, and in both cases are found to be consistent with CP conservation under interchange of t andt. In the tt rest frame, the asymmetry is observed to increase with the tt rapidity difference, ∆y, and with the invariant mass M tt of the tt system. Fully corrected parton-level asymmetries are derived in two regions of each variable, and the asymmetry is found to be most significant at large ∆y and M tt . For M tt ≥ 450 GeV/c 2 , the parton-level asymmetry in the tt rest frame is A tt = 0.475 ± 0.114 compared to a next-to-leading order QCD prediction of 0.088 ± 0.013.

Laser plasma accelerators 1 have produced high-quality electron beams with GeV energies from cm-scale devices 2 and are being investigated as hyperspectral fs light sources producing THz to γ-ray radiation 3-5 , and as drivers for future highenergy colliders 6,7 . These applications require a high degree of stability, beam quality and tunability. Here we report on a technique to inject electrons into the accelerating field of a laser-driven plasma wave and coupling of this injector to a lower-density, separately tunable plasma for further acceleration. The technique relies on a single laser pulse powering a plasma structure with a tailored longitudinal density profile, to produce beams that can be tuned in the range of 100-400 MeV with per-cent-level stability, using laser pulses of less than 40 TW. The resulting device is a simple stand-alone accelerator or the front end for a multistage higher-energy accelerator.Producing high-quality electron beams from an accelerator requires electron injection into the accelerating field to be localized in time and space. For laser plasma accelerators (LPAs) that rely on homogeneous plasmas driven with single laser pulses, continuous injection can occur when driving large-amplitude plasma waves (wakefields), resulting in large energy spread. Lower energy spread can be achieved through termination of injection by operating near the injection threshold or by injecting enough charge to suppress the wake amplitude (that is, beam loading). Subsequent termination of the accelerating process at dephasing (that is, when electrons are starting to outrun the accelerating wave) minimizes energy spread. These mechanisms have produced per-cent-level energy-spread beams 2,8-10 , but small changes in parameters can result in large changes in beam quality. As a result, tunability has been limited, necessitating the development of a simple, robust and controlled injection technique combined with an independently controllable accelerating stage.In general, injection of electrons into a plasma wave occurs when the velocity of background electrons approaches the wake phase velocity. Laser-based methods for boosting the electron velocity have been proposed 11,12 and implemented 13,14 to achieve tunable electron beams, but require sophisticated alignment and synchronization of the multiple laser pulses. Injection can also be triggered by introducing electrons into the correct phase of the wake through ionization 15 , but so far the technique has resulted in broad energy-spread beams with high divergence 16,17 . A different approach, that relies on a single laser pulse for powering the LPA, is to momentarily slow down the wake phase velocity to facilitate trapping 18 . The control of the wake phase velocity can be achieved by tailoring the nonlinear plasma wavelength λ p (z) along the longitudinal coordinate z, through control of the electron density n e and the laser parameters. Specifically, λ p (z) = λ p0 (z)F , where the linear plasma wavelength λ p0 (µm) ≈ 3.3 × 10 10 / √ n e (cm −3 ) and F ...

The study demonstrates highly accurate knowledge-based 3D dose predictions for radiotherapy plans.