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Register a new userMeasurement of D* Production in Diffractive Deep Inelastic Scattering at HERA
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H1 Collaboration
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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.
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Production of exclusive dijets in diffractive deep inelastic $e^pm p$ scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 372 pb$^{-1}$. The measurement was performed for $gamma^*-p$ centre-of-mass energies in the range $90 < W < 250$ GeV and for photon virtualities $Q^2 > 25$ GeV$^2$. Energy and transverse-energy flows around the jet axis are presented. The cross section is presented as a function of $beta$ and $phi$, where $beta=x/x_{rm I!P}$, $x$ is the Bjorken variable and $x_{rm I!P}$ is the proton fractional longitudinal momentum loss. The angle $phi$ is defined by the $gamma^*-$dijet plane and the $gamma^*-e^pm$ plane in the rest frame of the diffractive final state. The $phi$ cross section is measured in bins of $beta$. The results are compared to predictions from models based on different assumptions about the nature of the diffractive exchange.
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.
Several recent measurements of charmed hadron production in deep inelastic scattering at HERA are reviewed. Cross sections for the production of D mesons were measured and compared to NLO QCD predictions. The charm contribution to the inclusive structure function F_{2} was extracted and compared to previous measurements and theoretical predictions. The reconstruction of decays with a neutral strange hadron in the final state allowed the measurement of charm production to be extended into the low transverse momentum region. The fraction of c quarks hadronising into Lambda_{c}^{+} baryons was extracted using two different decay modes.
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.
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.
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