A detailed analysis is presented of the diffractive deep-inelastic scattering process ep → eXY , where Y is a proton or a low mass proton excitation carrying a fraction 1−x I P > 0.95 of the incident proton longitudinal momentum and the squared four-momentum transfer at the proton vertex satisfies |t| < 1 GeV 2 . Using data taken by the H1 experiment, the cross section is measured for photon virtualities in the range 3.5 ≤ Q 2 ≤ 1600 GeV 2 , triple differentially in x I P , Q 2 and β = x/x I P , where x is the Bjorken scaling variable. At low x I P , the data are consistent with a factorisable x I P dependence, which can be described by the exchange of an effective pomeron trajectory with intercept α IP (0) = 1.118 ± 0.008 (exp.) +0.029 −0.010 (model). Diffractive parton distribution functions and their uncertainties are determined from a next-to-leading order DGLAP QCD analysis of the Q 2 and β dependences of the cross section. The resulting gluon distribution carries an integrated fraction of around 70% of the exchanged momentum in the Q 2 range studied. Total and differential cross sections are also measured for the diffractive charged current process e + p →ν e XY and are found to be well described by predictions based on the diffractive parton distributions. The ratio of the diffractive to the inclusive neutral current ep cross sections is studied. Over most of the kinematic range, this ratio shows no significant dependence on Q 2 at fixed x I P and x or on x at fixed Q 2 and β.

A measurement of charm and beauty dijet photoproduction cross sections at the ep collider HERA is presented. Events are selected with two or more jets of transverse momentum p jet 1(2) t > 11(8) GeV in the central range of pseudo-rapidity −0.9 < η jet 1(2) < 1.3. The fractions of events containing charm and beauty quarks are determined using a method based on the impact parameter, in the transverse plane, of tracks to the primary vertex, as measured by the H1 central vertex detector. Differential dijet cross sections for charm and beauty, and their relative contributions to the flavour inclusive dijet photoproduction cross section, are measured as a function of the transverse momentum of the leading jet, the average pseudo-rapidity of the two jets and the observable x obs γ . Taking into account the theoretical uncertainties, the charm cross sections are consistent with a QCD calculation in next-to-leading order, while the predicted cross sections for beauty production are somewhat lower than the measurement.

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The cross section for the diffractive deep-inelastic scattering process ep → eXp is measured, with the leading final state proton detected in the H1 Forward Proton Spectrometer. The data analysed cover the range x IP < 0.1 in fractional proton longitudinal momentum loss, 0.08 < |t| < 0.5 GeV −2 in squared four-momentum transfer at the proton vertex, 2 < Q 2 < 50 GeV 2 in photon virtuality and 0.004 < β = x/x IP < 1, where x is the Bjorken scaling variable. For x IP < ∼ 10 −2 , the differential cross section has a dependence of approximately dσ/dt ∝ e 6t , independently of x IP , β and Q 2 within uncertainties. The cross section is also measured triple differentially in x IP , β and Q 2 . The x IP dependence is interpreted in terms of an effective pomeron trajectory with intercept α IP (0) = 1.114±0.018 (stat.)±0.012 (syst.) +0.040 −0.020 (model) and a sub-leading exchange. The data are in good agreement with an H1 measurement for which the event selection is based on a large gap in the rapidity distribution of the final state hadrons, after accounting for proton dissociation contributions in the latter. Within uncertainties, the dependence of the cross section on x and Q 2 can thus be factorised from the dependences on all studied variables which characterise the proton vertex, for both the pomeron and the sub-leading exchange.

Unravelling the interaction of biological macromolecules with ligands and substrates at high spatial and temporal resolution remains a major challenge in structural biology. The development of serial crystallography methods at X-ray free-electron lasers and subsequently at synchrotron light sources allows new approaches to tackle this challenge. Here, a new polyimide tape drive designed for mix-and-diffuse serial crystallography experiments is reported. The structure of lysozyme bound by the competitive inhibitor chitotriose was determined using this device in combination with microfluidic mixers. The electron densities obtained from mixing times of 2 and 50 s show clear binding of chitotriose to the enzyme at a high level of detail. The success of this approach shows the potential for high-throughput drug screening and even structural enzymology on short timescales at bright synchrotron light sources.