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HERAFitter is an open-source package that provides a framework for the determination of the parton distribution functions (PDFs) of the proton and for many different kinds of analyses in Quantum Chromodynamics (QCD). It encodes results from a wide range of experimental measurements in lepton–proton deep inelastic scattering and proton–proton (proton–antiproton) collisions at hadron colliders. These are complemented with a variety of theoretical options for calculating PDF-dependent cross section predictions corresponding to the measurements. The framework covers a large number of the existing methods and schemes used for PDF determination. The data and theoretical predictions are brought together through numerous methodological options for carrying out PDF fits and plotting tools to help to visualise the results. While primarily based on the approach of collinear factorisation, HERAFitter also provides facilities for fits of dipole models and transverse-momentum dependent PDFs. The package can be used to study the impact of new precise measurements from hadron colliders. This paper describes the general structure of HERAFitter and its wide choice of options.

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 W W di-boson to Z boson production cross sections at the LHC.

(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).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 ... 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... and span six orders of magnitude in negative four-momentum-transfer squared, ..., 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 ... An extraction of ... and results on electroweak unification and scaling violations are also presented.

HERAFitter is an open-source package that provides a framework for the determination of the parton distribution functions (PDFs) of the proton and for many different kinds of analyses in Quantum Chromodynamics (QCD). It encodes results from a wide range of experimental measurements in lepton-proton deep inelastic scattering and proton-proton (proton-antiproton) collisions at hadron colliders. These are complemented with a variety of theoretical options for calculating PDF-dependent cross section predictions corresponding to the measurements. The framework covers a large number of the existing methods and schemes used for PDF determination. The data and theoretical predictions are brought together through numerous methodological options for carrying out PDF fits and plotting tools to help to visualise the results. While primarily based on the approach of collinear factorisation, HERAFitter also provides facilities for fits of dipole models and transverse-momentum dependent PDFs. The package can be used to study the impact of new precise measurements from hadron colliders. This paper describes the general structure of HERAFitter and its wide choice of options.

A precision measurement of jet cross sections in neutral current deep-inelastic scattering for photon virtualities 5.5 < Q 2 < 80 GeV 2 and inelasticities 0.2 < y < 0.6 is presented, using data taken with the H1 detector at HERA, corresponding to an integrated luminosity of 290 pb - 1 . Double-differential inclusive jet, dijet and trijet cross sections are measured simultaneously and are presented as a function of jet transverse momentum observables and as a function of Q 2 . Jet cross sections normalised to the inclusive neutral current DIS cross section in the respective Q 2 -interval are also determined. Previous results of inclusive jet cross sections in the range 150 < Q 2 < 15 , 000 GeV 2 are extended to low transverse jet momenta 5 < P T jet < 7 GeV . The data are compared to predictions from perturbative QCD in next-to-leading order in the strong coupling, in approximate next-to-next-to-leading order and in full next-to-next-to-leading order. Using also the recently published H1 jet data at high values of Q 2 , the strong coupling constant α s ( M Z ) is determined in next-to-leading order.

Exclusive photoproduction of ρ 0 ( 770 ) mesons is studied using the H1 detector at the ep collider HERA. A sample of about 900,000 events is used to measure single- and double-differential cross sections for the reaction γ p → π + π - Y . Reactions where the proton stays intact ( m Y = m p ) are statistically separated from those where the proton dissociates to a low-mass hadronic system ( m p < m Y < 10 GeV ). The double-differential cross sections are measured as a function of the invariant mass m π π of the decay pions and the squared 4-momentum transfer t at the proton vertex. The measurements are presented in various bins of the photon–proton collision energy W γ p . The phase space restrictions are 0.5 ≤ m π π ≤ 2.2 GeV , | t | ≤ 1.5 GeV 2 , and 20 ≤ W γ p ≤ 80 GeV . Cross section measurements are presented for both elastic and proton-dissociative scattering. The observed cross section dependencies are described by analytic functions. Parametrising the m π π dependence with resonant and non-resonant contributions added at the amplitude level leads to a measurement of the ρ 0 ( 770 ) meson mass and width at m ρ = 770.8 - 2.7 + 2.6 ( tot. ) MeV and Γ ρ = 151.3 - 3.6 + 2.7 ( tot. ) MeV , respectively. The model is used to extract the ρ 0 ( 770 ) contribution to the π + π - cross sections and measure it as a function of t and W γ p . In a Regge asymptotic limit in which one Regge trajectory α ( t ) dominates, the intercept α ( t = 0 ) = 1.0654 - 0.0067 + 0.0098 ( tot. ) and the slope α ′ ( t = 0 ) = 0.233 - 0.074 + 0.067 ( tot. ) GeV - 2 of the t dependence are extracted for the case m Y = m p .

Exclusive photoproduction of$${{\\rho ^0}} (770)$$ρ 0 ( 770 ) mesons is studied using the H1 detector at the ep collider HERA. A sample of about 900,000 events is used to measure single- and double-differential cross sections for the reaction$$\\gamma p \\rightarrow \\pi ^{+}\\pi ^{-}Y$$γ p → π + π - Y . Reactions where the proton stays intact ($${{{m_Y}} {=}m_p}$$m Y = m p ) are statistically separated from those where the proton dissociates to a low-mass hadronic system ($$m_p{<}{{m_Y}} {<}10~{{\\text {GeV}}} $$m p < m Y < 10 GeV ). The double-differential cross sections are measured as a function of the invariant mass$$m_{\\pi \\pi }$$m π π of the decay pions and the squared 4-momentum transfer t at the proton vertex. The measurements are presented in various bins of the photon–proton collision energy$${{W_{\\gamma p}}} $$W γ p . The phase space restrictions are$$0.5\\le m_{\\pi \\pi } \\le 2.2~{{\\text {GeV}}} $$0.5 ≤ m π π ≤ 2.2 GeV ,$$\\vert t\\vert \\le 1.5~{{\\text {GeV}^2}} $$| t | ≤ 1.5 GeV 2 , and$$20 \\le W_{\\gamma p} \\le 80~{{\\text {GeV}}} $$20 ≤ W γ p ≤ 80 GeV . Cross section measurements are presented for both elastic and proton-dissociative scattering. The observed cross section dependencies are described by analytic functions. Parametrising the$${m_{\\pi \\pi }}$$m π π dependence with resonant and non-resonant contributions added at the amplitude level leads to a measurement of the$${{\\rho ^0}} (770)$$ρ 0 ( 770 ) meson mass and width at$$m_\\rho = 770.8{}^{+2.6}_{-2.7}~({\\text {tot.}})~{{\\text {MeV}}} $$m ρ = 770.8 - 2.7 + 2.6 ( tot. ) MeV and$$\\Gamma _\\rho = 151.3 {}^{+2.7}_{-3.6}~({\\text {tot.}})~{{\\text {MeV}}} $$Γ ρ = 151.3 - 3.6 + 2.7 ( tot. ) MeV , respectively. The model is used to extract the$${{\\rho ^0}} (770)$$ρ 0 ( 770 ) contribution to the$$\\pi ^{+}\\pi ^{-}$$π + π - cross sections and measure it as a function of t and$${W_{\\gamma p}}$$W γ p . In a Regge asymptotic limit in which one Regge trajectory$$\\alpha (t)$$α ( t ) dominates, the intercept$$\\alpha (t{=}0) = 1.0654\\ {}^{+0.0098}_{-0.0067}~({\\text {tot.}})$$α ( t = 0 ) = 1.0654 - 0.0067 + 0.0098 ( tot. ) and the slope$$\\alpha ^\\prime (t{=}0) = 0.233 {}^{+0.067 }_{-0.074 }~({\\text {tot.}}) ~{{\\text {GeV}^{-2}}} $$α ′ ( t = 0 ) = 0.233 - 0.074 + 0.067 ( tot. ) GeV - 2 of the t dependence are extracted for the case$$m_Y{=}m_p$$m Y = m p .

Exclusive photoproduction of ρ0(770) mesons is studied using the H1 detector at the ep collider HERA. A sample of about 900,000 events is used to measure single- and double-differential cross sections for the reaction γp→π+π-Y. Reactions where the proton stays intact (mY=mp) are statistically separated from those where the proton dissociates to a low-mass hadronic system (mp

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