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Register a new userMeasurement of Jet Production Cross Sections in Deep-inelastic ep Scattering at HERA
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The H1 collaboration
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A precision measurement of jet cross sections in neutral current deep-inelastic scattering for photon virtualities $5.5<Q^2<80,{rm GeV}^2$ and inelasticities $0.2<y<0.6$ is presented, using data taken with the H1 detector at HERA, corresponding to an integrated luminosity of $290,{rm pb}^{-1}$. 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 $150<Q^2<15,000,{rm GeV}^2$ are extended to low transverse jet momenta $5<P_{T}^{rm jet}<7,{rm GeV}$. 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.
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Recent results from jet production in deep inelastic ep scattering at HERA are reviewed. The values of alpha_s(M_z) extracted from a QCD analysis of the data are presented.
Measurements of open charm and beauty production cross sections in deep inelastic $ep$ scattering at HERA from the H1 and ZEUS Collaborations are combined. Reduced cross sections are obtained in the kinematic range of negative four-momentum transfer squared of the photon $2.5$ GeV$^2<Q^2<2000$ GeV$^2$ and Bjorken scaling variable $3cdot10^{-5}<x_{text{Bj}}<5cdot10^{-2}$. The combination method accounts for the correlations of the statistical and systematic uncertainties among the different datasets. Perturbative QCD calculations are compared to the combined data. A next-to-leading order QCD analysis is performed using these data together with the combined inclusive deep inelastic scattering cross sections from HERA. The running charm- and beauty-quark masses are determined as $m_c(m_c) = 1.290^{+0.046}_{-0.041}text{(exp/fit)}^{+0.062}_{-0.014}text{(model)}^{+0.003}_{-0.031}text{(parameterisation)}$ GeV and $m_b(m_b) = 4.049^{+0.104}_{-0.109}text{(exp/fit)}^{+0.090}_{-0.032}text{(model)}^{+0.001}_{-0.031} text{(parameterisation)}$~GeV.
Measurements of $D^{*}(2010)$ meson production in diffractive deep inelastic scattering $(5<Q^{2}<100~{rm GeV}^{2})$ are presented which are based on HERA data recorded at a centre-of-mass energy $sqrt{s} = 319{rm~GeV}$ with an integrated luminosity of $287$ pb$^{-1}$. The reaction $ep rightarrow eXY$ is studied, where the system $X$, containing at least one $D^{*}(2010)$ meson, is separated from a leading low-mass proton dissociative system $Y$ by a large rapidity gap. The kinematics of $D^{*}$ candidates are reconstructed in the $D^{*}rightarrow K pipi$ decay channel. The measured cross sections compare favourably with next-to-leading order QCD predictions, where charm quarks are produced via boson-gluon fusion. The charm quarks are then independently fragmented to the $D^{*}$ mesons. The calculations rely on the collinear factorisation theorem and are based on diffractive parton densities previously obtained by H1 from fits to inclusive diffractive cross sections. The data are further used to determine the diffractive to inclusive $D^{*}$ production ratio in deep inelastic scattering.
Charm production in deep inelastic scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 120 pb^{-1}. The hadronic decay channels D^{+} -> K^{0}_{S} pi^{+}, Lambda_{c}^{+} -> p K^{0}_{S} and Lambda_{c}^{+} -> Lambda pi^{+}, and their charge conjugates, were reconstructed. The presence of a neutral strange hadron in the final state reduces the combinatorial background and extends the measured sensitivity into the low transverse momentum region. The kinematic range is 0 < p_{T}(D^{+}, Lambda_{c}^{+}) < 10 GeV, |eta(D^{+}, Lambda_{c}^{+})| < 1.6, 1.5 < Q^{2} < 1000 GeV^{2} and 0.02 < y < 0.7. Inclusive and differential cross sections for the production of D^{+} mesons are compared to next-to-leading-order QCD predictions. The fraction of c quarks hadronising into Lambda_{c}^{+} baryons is extracted.
We present the complete next-to-leading order calculation of isolated prompt photon production in association with a jet in deep-inelastic scattering. The calculation involves, direct, resolved and fragmentation contributions. It is shown that defining the transverse momenta in the proton virtual-photon frame (CM*), as usually done, or in the laboratory frame (LAB), as done in some experiments, is not equivalent and leads to important differences concerning the perturbative approach. In fact, using the latter frame may preclude, under certain conditions, the calculation of the next-to-leading order correction to the important resolved component. A comparaison with the latest ZEUS data is performed and good agreement is found in the perturbatively stable regions.
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