[en] The future compact linear collider (CLIC) offers a possibility for a rich precision physics programme, in particular in the Higgs sector through the energy staging. This is the first paper addressing the measurement of the standard model Higgs boson decay into two muons at 1.4 TeV CLIC. With respect to similar studies at future linear colliders, this paper includes several novel contributions to the statistical uncertainty of the measurement. The latter includes the equivalent photon approximation employed to describe e"+e"- and eγ interactions whenever the virtuality of the mediated photon is smaller than 4 GeV and realistic forward electron tagging based on energy deposition maps in the forward calorimeters, as well as several processes with the Beamstrahlung photons that results in irreducible contribution to the signal. In addition, coincidence of the Bhabha scattering with the signal and background processes is considered, altering the signal selection efficiency. The study is performed using a fully simulated CLICILD detector model. It is shown that the branching ratio for the Higgs decay into a pair of muons BR(H → μ"+μ"-) times the Higgs production cross-section in WW-fusion σ (Hνanti ν) can be measured with 38 % statistical accuracy at √(s) = 1.4 TeV, assuming an integrated luminosity of 1.5 ab"-"1 with unpolarised beams. If 80 % electron beam polarisation is considered, the statistical uncertainty of the measurement is reduced to 25 %. Systematic uncertainties are negligible in comparison to the statistical uncertainty. (orig.)

[en] New concepts in nuclear reactor technology require precise neutron reaction data in the intermediate and high energy range. At present, experimental and evaluated nuclear data, particularly for (n, xn) reactions, arc very scarce. Moreover, real discrepancies exist between different databases. The lack of experimental data is essentially due to the difficulty of measuring (n, xn) reactions. No universal method applicable to all isotopes exists. One of the possible methods is the in-beam γ-ray spectroscopy and neutron time of flight technique on white neutron beams. In this way one actually directly measures (n, xnγ) reaction cross-sections. These serve as a starting point in the subsequent derivation of (n , xn) reaction cross-sections using nuclear models. This method was applied with a natural lead sample at die GELINA white neutron beam facility in Geel, Belgium. (author)

[en] A prototype of a luminometer, designed for a future e⁺e^- collider detector, and consisting at present of a four-plane module, was tested in the CERN PS accelerator T9 beam. The objective of this beam test was to demonstrate a multi-plane tungsten/silicon operation, to study the development of the electromagnetic shower and to compare it with MC simulations. The Moliere radius has been determined to be 24.0 ± 0.6 (stat.) ± 1.5 (syst.) mm using a parametrization of the shower shape. Very good agreement was found between data and a detailed Geant4 simulation. (orig.)

[en] The Compact Linear Collider (CLIC) is an option for a future e"+e"- collider operating at centre-of-mass energies up to 3 TeV, providing sensitivity to a wide range of new physics phenomena and precision physics measurements at the energy frontier. This paper is the first comprehensive presentation of the Higgs physics reach of CLIC operating at three energy stages: √(s) = 350 GeV, 1.4 and 3 TeV. The initial stage of operation allows the study of Higgs boson production in Higgsstrahlung (e"+e"- → ZH) and WW-fusion (e"+e"- → Hν_e anti ν_e), resulting in precise measurements of the production cross sections, the Higgs total decay width Γ_H, and model-independent determinations of the Higgs couplings. Operation at √(s) > 1 TeV provides high-statistics samples of Higgs bosons produced through WW-fusion, enabling tight constraints on the Higgs boson couplings. Studies of the rarer processes e"+e"- → t anti tH and e"+e"- → HHν_e anti ν_e allow measurements of the top Yukawa coupling and the Higgs boson self-coupling. This paper presents detailed studies of the precision achievable with Higgs measurements at CLIC and describes the interpretation of these measurements in a global fit. (orig.)

[en] Inclusive production of D^* mesons in deep-inelastic ep scattering at HERA is studied in the range 5< Q²<100 GeV² of the photon virtuality and 0.02< y<0.7 of the inelasticity of the scattering process. The observed phase space for the D^* meson is p_T(D^*) >1.25 GeV and vertical stroke η(D^*) vertical stroke <1.8. The data sample corresponds to an integrated luminosity of 348 pb ^-1 collected with the H1 detector. Single and double differential cross sections are measured and the charm contribution F₂^cantic to the proton structure function F₂ is determined. The results are compared to perturbative QCD predictions at next-to-leading order implementing different schemes for the charm mass treatment and with Monte Carlo models based on leading order matrix elements with parton showers. (orig.)

[en] Charged particle production in deep-inelastic ep scattering is measured with the H1 detector at HERA. The kinematic range of the analysis covers low photon virtualities, 5 < Q² < 100 GeV², and small values of Bjorken-x, 10^-4 < x < 10^-2. The analysis is performed in the hadronic centre-of-mass system. The charged particle densities are measured as a function of pseudorapidity (η^*) and transverse momentum (p_T^*) in the range 0<η^* < 5 and 0< p_T^* < 10 GeV in bins of x and Q². The data are compared to predictions from different Monte Carlo generators implementing various options for hadronisation and parton evolutions. (orig.)

[en] The production of leading neutrons, where the neutron carries a large fraction x_L of the incoming proton's longitudinal momentum, is studied in deep-inelastic positron-proton scattering at HERA. The data were taken with the H1 detector in the years 2006 and 2007 and correspond to an integrated luminosity of 122 pb ^-1. The semi-inclusive cross section is measured in the phase space defined by the photon virtuality 6< Q²<100 GeV ², Bjorken scaling variable 1.5 .10 ^-4< x <3 .10 ^-2, longitudinal momentum fraction 0.32 < x_L <0.95 and neutron transverse momentum p_T <0.2 GeV. The leading neutron structure function, F₂^LN(3)(Q²,x,x_L), and the fraction of deep-inelastic scattering events containing a leading neutron are studied as a function of Q², x and x_L. Assuming that the pion exchange mechanism dominates leading neutron production, the data provide constraints on the shape of the pion structure function. (orig.)

[en] The production of photons at very small angles with respect to the proton beam direction is studied in deep-inelastic positron-proton scattering at HERA. The data are taken with the H1 detector in the years 2006 and 2007 and correspond to an integrated luminosity of 126 pb^-1. The analysis covers the range of negative four momentum transfer squared at the positron vertex 6< Q ²<100 GeV² and inelasticity 0.05< y<0.6. Cross sections are measured for the most energetic photon with pseudorapidity η>7.9 as a function of its transverse momentum p_T^lead and longitudinal momentum fraction of the incoming proton x_L^lead. In addition, the cross sections are studied as a function of the sum of the longitudinal momentum fraction x_L^sum of all photons in the pseudorapidity range η>7.9. The cross sections are normalised to the inclusive deep-inelastic scattering cross section and compared to the predictions of models of deep-inelastic scattering and models of the hadronic interactions of high energy cosmic rays. (orig.)

[en] A search for squarks in R-parity violating supersymmetry is performed in e ^± p collisions at HERA using the H1 detector. The full data sample taken at a centre-of-mass energy √(s)=319 GeV is used for the analysis, corresponding to an integrated luminosity of 255 pb^-1 of e ⁺ p and 183 pb^-1 of e ^- p collision data. The resonant production of squarks via a Yukawa coupling λ' is considered, taking into account direct and indirect R-parity violating decay modes. Final states with jets and leptons are investigated. No evidence for squark production is found and mass dependent limits on λ' are obtained in the framework of the Minimal Supersymmetric Standard Model and in the Minimal Supergravity Model. In the considered part of the parameter space, for a Yukawa coupling of electromagnetic strength λ'=0.3, squarks of all flavours are excluded up to masses of 275 GeV at 95% confidence level, with down-type squarks further excluded up to masses of 290 GeV. (orig.)

[en] The diffractive process ep→eXY, where Y denotes a proton or its low mass excitation with M_Y<1.6 GeV, is studied with the H1 experiment at HERA. The analysis is restricted to the phase space region of the photon virtuality 3≤Q²≤ 1600 GeV ², the square of the four-momentum transfer at the proton vertex vertical stroke t vertical stroke < 1.0 GeV ² and the longitudinal momentum fraction of the incident proton carried by the colourless exchange x_P<0.05. Triple differential cross sections are measured as a function of x_P, Q ² and β=x/x_P where x is the Bjorken scaling variable. These measurements are made after selecting diffractive events by demanding a large empty rapidity interval separating the final state hadronic systems X and Y. High statistics measurements covering the data taking periods 1999-2000 and 2004-2007 are combined with previously published results in order to provide a single set of diffractive cross sections from the H1 experiment using the large rapidity gap selection method. The combined data represent a factor between three and thirty increase in statistics with respect to the previously published results. The measurements are compared with predictions from NLO QCD calculations based on diffractive parton densities and from a dipole model. The proton vertex factorisation hypothesis is tested. (orig.)