Parton distribution functions at LO, NLO and NNLO with correlated uncertainties between orders

Sets of parton distribution functions (PDFs) of the proton are reported for the leading (LO), next-to-leading (NLO) and next-to-next-to-leading-order (NNLO) QCD calculations. The parton distribution functions are determined with the HERAFitter program using the data from the HERA experiments and preserving correlations between uncertainties for the LO, NLO and NNLO PDF sets. The sets are used to study cross-section ratios and their uncertainties when calculated at different orders in QCD. A reduction of the overall theoretical uncertainty is observed if correlations between the PDF sets are taken into account for the ratio of WW di-boson to Z boson production cross sections at the LHC

Diffractive dijet production with a leading proton in ep collisions at HERA

The cross section of the diffractive process e + p → e + Xp is measured at a centre-of-mass energy of 318 GeV, where the system X contains at least two jets and the leading final state proton p is detected in the H1 Very Forward Proton Spectrometer. The measurement is performed in photoproduction with photon virtualities Q 2 < 2 GeV 2 and in deep-inelastic scattering with 4 GeV 2 < Q 2 < 80 GeV 2 . The results are compared to next- to-leading order QCD calculations based on diffractive parton distribution functions as extracted from measurements of inclusive cross sections in diffractive deep-inelastic scattering

Measurement of Feynman- x spectra of photons and neutrons in the very forward direction in deep-inelastic scattering at HERA

Measurements of normalised cross sections for the production of photons and neutrons at very small angles with respect to the proton beam direction in deep-inelastic <math><mrow><mi>e</mi><mi>p</mi></mrow></math> scattering at HERA are presented as a function of the Feynman variable <math><msub><mi>x</mi><mi>F</mi></msub></math> and of the centre-of-mass energy of the virtual photon-proton system <math><mi>W</mi></math> . The data are taken with the H1 detector in the years 2006 and 2007 and correspond to an integrated luminosity of <math><mrow><mn>131</mn><mspace width="3.33333pt"/><msup><mtext>pb</mtext><mrow><mo>-</mo><mn>1</mn></mrow></msup></mrow></math> . The measurement is restricted to photons and neutrons in the pseudorapidity range <math><mrow><mi mathvariant="italic">η</mi><mo>&gt;</mo><mn>7.9</mn></mrow></math> and covers the range of negative four momentum transfer squared at the positron vertex <math><mrow><mn>6</mn><mo>&lt;</mo><msup><mi>Q</mi><mn>2</mn></msup><mo>&lt;</mo><mn>100</mn></mrow></math>  GeV <math><msup><mrow/><mn>2</mn></msup></math> , of inelasticity <math><mrow><mn>0.05</mn><mo>&lt;</mo><mi>y</mi><mo>&lt;</mo><mn>0.6</mn></mrow></math> and of <math><mrow><mn>70</mn><mo>&lt;</mo><mi>W</mi><mo>&lt;</mo><mn>245</mn><mspace width="3.33333pt"/></mrow></math> GeV. To test the Feynman scaling hypothesis the <math><mi>W</mi></math> dependence of the <math><msub><mi>x</mi><mi>F</mi></msub></math> dependent cross sections is investigated. Predictions of deep-inelastic scattering models and of models for hadronic interactions of high energy cosmic rays are compared to the measured cross sections

Measurement of multijet production in ep collisions at high Q2 and determination of the strong coupling αs

Inclusive jet, dijet and trijet differential cross sections are measured in neutral current deep-inelastic scattering for exchanged boson virtualities 150<Q2<15000GeV2 using the H1 detector at HERA. The data were taken in the years 2003 to 2007 and correspond to an integrated luminosity of 351pb-1 . Double differential Jet cross sections are obtained using a regularised unfolding procedure. They are presented as a function of Q2 and the transverse momentum of the jet, PTjet , and as a function of Q2 and the proton’s longitudinal momentum fraction, ξ , carried by the parton participating in the hard interaction. In addition normalised double differential jet cross sections are measured as the ratio of the jet cross sections to the inclusive neutral current cross sections in the respective Q2 bins of the jet measurements. Compared to earlier work, the measurements benefit from an improved reconstruction and calibration of the hadronic final state. The cross sections are compared to perturbative QCD calculations in next-to-leading order and are used to determine the running coupling and the value of the strong coupling constant as αs(MZ)=0.1165(8)exp(38)pdf,theo

Measurement of dijet production in diffractive deep-inelastic ep scattering at HERA

A measurement is presented of single- and double-differential dijet cross sections in diffractive deep-inelastic ep scattering at HERA using data collected by the H1 experiment corresponding to an integrated luminosity of 290 pb −1 . The investigated phase space is spanned by the photon virtuality in the range of 4 < Q 2 < 100 GeV 2 and by the fractional proton longitudinal momentum loss x ℙ < 0 . 03. The resulting cross sections are compared with next-to-leading order QCD predictions based on diffractive parton distribution functions and the value of the strong coupling constant is extracted