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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 strong coupling constant α s is determined from inclusive jet and dijet cross sections in neutral-current deep-inelastic ep scattering (DIS) measured at HERA by the H1 collaboration using next-to-next-to-leading order (NNLO) QCD predictions. The dependence of the NNLO predictions and of the resulting value of α s ( m Z ) at the Z -boson mass m Z are studied as a function of the choice of the renormalisation and factorisation scales. Using inclusive jet and dijet data together, the strong coupling constant is determined to be α s ( m Z ) = 0.1157 ( 20 ) exp ( 29 ) th . Complementary, α s ( m Z ) is determined together with parton distribution functions of the proton (PDFs) from jet and inclusive DIS data measured by the H1 experiment. The value α s ( m Z ) = 0.1142 ( 28 ) tot obtained is consistent with the determination from jet data alone. The impact of the jet data on the PDFs is studied. The running of the strong coupling is tested at different values of the renormalisation scale and the results are found to be in agreement with expectations.

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.

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.

A bstract 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.

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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