Plasma-Wakefield Accelerator Group

Abstract:

A combination is presented of all inclusive deep inelastic cross sections previously published by the H1 and ZEUS collaborations at HERA for neutral and charged current e±p scattering for zero beam polarisation. The data were taken at proton beam energies of 920, 820, 575 and 460 GeV and an electron beam energy of 27.5 GeV. The data correspond to an integrated luminosity of about 1 fb−1 and span six orders of magnitude in negative four-momentum-transfer squared, Q2, and Bjorken x. The correlations of the systematic uncertainties were evaluated and taken into account for the combination. The combined cross sections were input to QCD analyses at leading order, next-to-leading order and at next-to-next-to-leading order, providing a new set of parton distribution functions, called HERAPDF2.0. In addition to the experimental uncertainties, model and parameterisation uncertainties were assessed for these parton distribution functions. Variants of HERAPDF2.0 with an alternative gluon parameterisation, HERAPDF2.0AG, and using fixed-flavour-number schemes, HERAPDF2.0FF, are presented. The analysis was extended by including HERA data on charm and jet production, resulting in the variant HERAPDF2.0Jets. The inclusion of jet-production cross sections made a simultaneous determination of these parton distributions and the strong coupling constant possible, resulting in αs(MZ)=0.1183±0.0009(exp)±0.0005(model/parameterisation)±0.0012(hadronisation)+0.0037−0.0030(scale). An extraction of xFγZ3 and results on electroweak unification and scaling violations are also presented.

Abstract:

A combination is presented of all inclusive deep inelastic cross sections previously published by the H1 and ZEUS collaborations at HERA for neutral and charged current (Formula presented.) scattering for zero beam polarisation. The data were taken at proton beam energies of 920, 820, 575 and 460 GeV and an electron beam energy of 27.5 GeV. The data correspond to an integrated luminosity of about 1 fb(Formula presented.) and span six orders of magnitude in negative four-momentum-transfer squared, (Formula presented.), and Bjorken x. The correlations of the systematic uncertainties were evaluated and taken into account for the combination. The combined cross sections were input to QCD analyses at leading order, next-to-leading order and at next-to-next-to-leading order, providing a new set of parton distribution functions, called HERAPDF2.0. In addition to the experimental uncertainties, model and parameterisation uncertainties were assessed for these parton distribution functions. Variants of HERAPDF2.0 with an alternative gluon parameterisation, HERAPDF2.0AG, and using fixed-flavour-number schemes, HERAPDF2.0FF, are presented. The analysis was extended by including HERA data on charm and jet production, resulting in the variant HERAPDF2.0Jets. The inclusion of jet-production cross sections made a simultaneous determination of these parton distributions and the strong coupling constant possible, resulting in (Formula presented.). An extraction of (Formula presented.) and results on electroweak unification and scaling violations are also presented.

Abstract:

The FLASHForward project at DESY is a pioneering plasma-wakefield acceleration experiment that aims to produce, in a few centimetres of ionised hydrogen, beams with energy of order GeV that are of quality sufficient to be used in a free-electron laser. The plasma is created by ionising a gas in a gas cell with a multi-TW laser system. The plasma wave will be driven by high-current-density electron beams from the FLASH linear accelerator. The laser system can also be used to provide optical diagnostics of the plasma and electron beams due to the <30 fs synchronisation between the laser and the driving electron beam. The project will explore both external and internal witness-beam injection techniques. The operation parameters of the experiment are discussed, as well as the scientific programme.

Abstract:

H1 and ZEUS have published single-differential cross sections for inclusive D^∗±-meson production in deep-inelastic ep scattering at HERA from their respective final data sets. These cross sections are combined in the common visible phase-space region of photon virtuality Q²> 5 GeV², electron inelasticity 0.02 < y < 0.7 and the D^∗± meson’s transverse momentum pT(D^∗) > 1.5 GeV and pseudorapidity |η(D^∗)| < 1.5. The combination procedure takes into account all correlations, yielding significantly reduced experimental uncertainties. Double-differential cross sections d²σ/dQ²dy are combined with earlier D^∗± data, extending the kinematic range down to Q²> 1.5 GeV². Perturbative next-to-leading-order QCD predictions are compared to the results.

Abstract:

The PXIE accelerator [1] is the front-end test stand of the proposed Proton Improvement Plan (PIP-II) [2] initiative: a CW-compatible pulsed H-superconducting RF linac upgrade to Fermilab's injection system. The PXIE Ion Source and Low-Energy Beam Transport (LEBT) section are designed to create and transfer a 1-10 mA H-beam, in either pulsed (0.001-16 ms) or DC mode, from the ion source through to the injection point of the RFQ. This paper discusses the range of diagnostic tools - Allison-type Emittance Scanner, Faraday Cup, Toroid, DCCT, electrically isolated diaphragms - involved in the commissioning of the beam line and preparation of the beam for injection into the RFQ.