Running of the charm-quark mass from HERA deep-inelastic scattering data

Combined HERA data on charm production in deep-inelastic scattering have previously been used to determine the charm-quark running mass in the renormalisation scheme. Here, the same data are used as a function of the photon virtuality to evaluate the charm-quark running mass at different scales to one-loop order, in the context of a next-to-leading order QCD analysis. The scale dependence of the mass is found to be consistent with QCD expectations

Running of the Charm-Quark Mass from HERA Deep-Inelastic Scattering Data

Combined HERA data on charm production in deep-inelastic scattering have previously been used to determine the charm-quark running mass $m_c(m_c)$ in the MSbar renormalisation scheme. Here, the same data are used as a function of the photon virtuality $Q^2$ to evaluate the charm-quark running mass at different scales to one-loop order, in the context of a next-to-leading order QCD analysis. The scale dependence of the mass is found to be consistent with QCD expectations

Measurement of jet production cross sections in deep-inelastic

A precision measurement of jet cross sections in neutral current deep-inelastic scattering for photon virtualities $$5.5<Q^2 <80\,\mathrm {GeV}^2$$ and inelasticities $$0.2<y<0.6$$ is presented, using data taken with the H1 detector at HERA, corresponding to an integrated luminosity of $$290\,\mathrm {pb}^{-1}$$. 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 $$150<Q^2 <15{,}000\,\mathrm {GeV}^2$$ are extended to low transverse jet momenta $$5<P_\mathrm{T}^\mathrm{jet} <7\,\mathrm {GeV}$$. 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 $$\alpha _s(M_Z)$$ is determined in next-to-leading order

Search for QCD Instanton-Induced Processes at HERA in the High-Q2Q^2 Domain

23 pages, 9 figures, this version accepted by EPJCInternational audienceSignals of QCD instanton-induced processes are searched for in neutral current deep-inelastic scattering at the electron-proton collider HERA in the kinematic region defined by the Bjorken-scaling variable $x > 10^{-3}$, the inelasticity $0.2< y < 0.7$ and the photon virtuality $150 < Q^2 < 15000$ GeV$^2$. The search is performed using H1 data corresponding to an integrated luminosity of ~$351$ pb$^{-1}$. No evidence for the production of QCD instanton-induced events is observed. Upper limits on the cross section for instanton-induced processes between $1.5$~pb and $6$~pb, at $95\%$~ confidence level, are obtained depending on the kinematic domain in which instantons could be produced. Compared to earlier publications, the limits are improved by an order of magnitude and for the first time are challenging theory predictions

Exclusive

A first measurement is presented of exclusive photoproduction of $$\rho ^0$$ mesons associated with leading neutrons at HERA. The data were taken with the H1 detector in the years 2006 and 2007 at a centre-of-mass energy of $$\sqrt{s}=319$$ GeV and correspond to an integrated luminosity of 1.16 pb$$^{-1}$$. The $$\rho ^0$$ mesons with transverse momenta $$p_T0.35$$, are detected in the Forward Neutron Calorimeter. The phase space of the measurement is defined by the photon virtuality $$Q^2 < 2$$ GeV$$^2$$, the total energy of the photon–proton system $$20 < W_{\gamma p}< 100$$ GeV and the polar angle of the leading neutron $$\theta _n < 0.75$$ mrad. The cross section of the reaction $$\gamma p \rightarrow \rho ^0 n \pi ^+$$ is measured as a function of several variables. The data are interpreted in terms of a double peripheral process, involving pion exchange at the proton vertex followed by elastic photoproduction of a $$\rho ^0$$ meson on the virtual pion. In the framework of one-pion-exchange dominance the elastic cross section of photon-pion scattering, $$\sigma ^\mathrm{el}(\gamma \pi ^+ \rightarrow \rho ^0\pi ^+)$$, is extracted. The value of this cross section indicates significant absorptive corrections for the exclusive reaction $$\gamma p \rightarrow \rho ^0 n \pi ^+$$