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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 H1 Collaboration at HERA reports the first measurement of groomed event shape observables in deep inelastic electron-proton scattering (DIS) at s = 319 GeV, using data recorded between the years 2003 and 2007 with an integrated luminosity of 351 pb - 1 . Event shapes provide incisive probes of perturbative and non-perturbative QCD. Grooming techniques have been used for jet measurements in hadronic collisions; this paper presents the first application of grooming to DIS data. The analysis is carried out in the Breit frame, utilizing the novel Centauro jet clustering algorithm that is designed for DIS event topologies. Events are required to have squared momentum-transfer Q 2 > 150 GeV 2 and inelasticity 0.2 < y < 0.7 . We report measurements of the production cross section of groomed event 1-jettiness and groomed invariant mass for several choices of grooming parameter. Monte Carlo model calculations and analytic calculations based on Soft Collinear Effective Theory are compared to the measurements.

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.

The H1 Collaboration at HERA reports the first measurement of groomed event shape observables in deep inelastic electron-proton scattering (DIS) at \\(\\sqrt{s}=319\\) GeV, using data recorded between the years 2003 and 2007 with an integrated luminosity of \\(351\\) pb\\(^{-1}\\). Event shapes provide incisive probes of perturbative and non-perturbative QCD. Grooming techniques have been used for jet measurements in hadronic collisions; this paper presents the first application of grooming to DIS data. The analysis is carried out in the Breit frame, utilizing the novel Centauro jet clustering algorithm that is designed for DIS event topologies. Events are required to have squared momentum-transfer \\(Q^2 > 150\\) GeV\\(^2\\) and inelasticity \\( 0.2 < y < 0.7\\). We report measurements of the production cross section of groomed event 1-jettiness and groomed invariant mass for several choices of grooming parameter. Monte Carlo model calculations and analytic calculations based on Soft Collinear Effective Theory are compared to the measurements.

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 \\(\\alpha_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 \\pm 3.9\\,\\%_\\text{stat} \\pm 4.5\\,\\%_\\text{syst} \\pm 1.6\\,\\%_\\text{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.

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 .

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.

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 [Formula omitted] 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 [Formula omitted]. Reactions where the proton stays intact ( [Formula omitted]) are statistically separated from those where the proton dissociates to a low-mass hadronic system ( [Formula omitted]). The double-differential cross sections are measured as a function of the invariant mass [Formula omitted] 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 [Formula omitted]. The phase space restrictions are [Formula omitted], [Formula omitted], and [Formula omitted]. Cross section measurements are presented for both elastic and proton-dissociative scattering. The observed cross section dependencies are described by analytic functions. Parametrising the [Formula omitted] dependence with resonant and non-resonant contributions added at the amplitude level leads to a measurement of the [Formula omitted] meson mass and width at [Formula omitted] and [Formula omitted], respectively. The model is used to extract the [Formula omitted] contribution to the [Formula omitted] cross sections and measure it as a function of t and [Formula omitted]. In a Regge asymptotic limit in which one Regge trajectory [Formula omitted] dominates, the intercept [Formula omitted] and the slope [Formula omitted] of the t dependence are extracted for the case [Formula omitted].

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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