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The H1 Collaboration reports the first measurement of the 1-jettiness event shape observable τ 1 b in neutral-current deep-inelastic electron-proton scattering (DIS). The observable τ 1 b is equivalent to a thrust observable defined in the Breit frame. The data sample was collected at the HERA ep collider in the years 2003–2007 with center-of-mass energy of s = 319 GeV , corresponding to an integrated luminosity of 351.1  pb - 1 . Triple differential cross sections are provided as a function of τ 1 b , event virtuality Q 2 , and inelasticity y , in the kinematic region Q 2 > 150 GeV 2 . Single differential cross sections are provided as a function of τ 1 b in a limited kinematic range. Double differential cross sections are measured, in contrast, integrated over τ 1 b and represent the inclusive neutral-current DIS cross section measured as a function of Q 2 and y . The data are compared to a variety of predictions and include long-standing and more recent Monte Carlo event generators, predictions in fixed-order perturbative QCD where calculations up to O ( α s 3 ) are available for τ 1 b or inclusive DIS, and resummed predictions at next-to-leading logarithmic accuracy matched to fixed order predictions at O ( α s 2 ) . These comparisons reveal sensitivity of the 1-jettiness observable to QCD parton shower and resummation effects, as well as the modeling of hadronization and fragmentation. Within their range of validity, the fixed-order predictions provide a good description of the data. Monte Carlo event generators are predictive over the full measured range and hence their underlying models and parameters can be constrained by comparing to the presented data.

The Breit frame provides a natural frame to analyze lepton–proton scattering events. In this reference frame, the parton model hard interactions between a quark and an exchanged boson defines the coordinate system such that the struck quark is back-scattered along the virtual photon momentum direction. In Quantum Chromodynamics (QCD), higher order perturbative or non-perturbative effects can change this picture drastically. As Bjorken- x decreases below one half, a rather peculiar event signature is predicted with increasing probability, where no radiation is present in one of the two Breit-frame hemispheres and all emissions are to be found in the other hemisphere. At higher orders in α s or in the presence of soft QCD effects, predictions of the rate of these events are far from trivial, and that motivates measurements with real data. We report on the first observation of the empty current hemisphere events in electron–proton collisions at the HERA collider using data recorded with the H1 detector at a center-of-mass energy of 319 GeV. The fraction of inclusive neutral-current DIS events with an empty hemisphere is found to be 0.0112 ± 3.9 % stat ± 4.5 % syst ± 1.6 % mod in the selected kinematic region of 150 < Q 2 < 1500 GeV 2 and inelasticity 0.14 < y < 0.7 . The data sample corresponds to an integrated luminosity of 351.1 pb - 1 , sufficient to enable differential cross section measurements of these events. The results show an enhanced discriminating power at lower Bjorken- x among different Monte Carlo event generator predictions.

A precision measurement of jet cross sections in neutral current deep-inelastic scattering for photon virtualities [Formula omitted] and inelasticities [Formula omitted] is presented, using data taken with the H1 detector at HERA, corresponding to an integrated luminosity of [Formula omitted]. 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 [Formula omitted]. Jet cross sections normalised to the inclusive neutral current DIS cross section in the respective [Formula omitted]-interval are also determined. Previous results of inclusive jet cross sections in the range [Formula omitted] are extended to low transverse jet momenta [Formula omitted]. 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 [Formula omitted], the strong coupling constant [Formula omitted] is determined in next-to-leading order.

The parameters of the electroweak theory are determined in a combined electroweak and QCD analysis using all deep-inelastic \\[e^+p\\] and \\[e^-p\\] neutral current and charged current scattering cross sections published by the H1 Collaboration, including data with longitudinally polarised lepton beams. Various fits to Standard Model parameters in the on-shell scheme are performed. The mass of the W boson is determined as \\[m_W=80.520\\pm 0.115~\\mathrm {GeV} \\]. The axial-vector and vector couplings of the light quarks to the Z boson are also determined. Both results improve the precision of previous H1 determinations based on HERA-I data by about a factor of two. Possible scale dependence of the weak coupling parameters in both neutral and charged current interactions beyond the Standard Model is also studied. All results are found to be consistent with the Standard Model expectations.

The determination of the strong coupling constant αs(mZ) from H1 inclusive and dijet cross section data [1] exploits perturbative QCD predictions in next-to-next-to-leading order (NNLO) [2–4]. An implementation error in the NNLO predictions was found [4] which changes the numerical values of the predictions and the resulting values of the fits. Using the corrected NNLO predictions together with inclusive jet and dijet data, the strong coupling constant is determined to be αs(mZ)=0.1166(19)exp(24)th. Complementarily, αs(mZ) is determined together with parton distribution functions of the proton (PDFs) from jet and inclusive DIS data measured by the H1 experiment. The value αs(mZ)=0.1147(25)tot obtained is consistent with the determination from jet data alone. Corrected figures and numerical results are provided and the discussion is adapted accordingly.

The measurement of the jet cross sections by the H1 collaboration had been compared to various predictions including the next-to-next-to-leading order (NNLO) QCD calculations which are corrected in this erratum for an implementation error in one of the components of the NNLO calculations. The jet data and the other predictions remain unchanged. Eight figures, one table and conclusions are adapted accordingly, exhibiting even better agreement between the corrected NNLO predictions and the jet data.

Charged particle multiplicity distributions in positron-proton deep inelastic scattering at a centre-of-mass energy s=319 GeV are measured. The data are collected with the H1 detector at HERA corresponding to an integrated luminosity of 136 pb-1. Charged particle multiplicities are measured as a function of photon virtuality Q2, inelasticity y and pseudorapidity η in the laboratory and the hadronic centre-of-mass frames. Predictions from different Monte Carlo models are compared to the data. The first and second moments of the multiplicity distributions are determined and the KNO scaling behaviour is investigated. The multiplicity distributions as a function of Q2 and the Bjorken variable xbj are converted to the hadron entropy Shadron, and predictions from a quantum entanglement model are tested.

Abstract Exclusive photoproduction ofρ 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 reactionγ p → π ⁺π ⁻Yγ 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)

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