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E. Mirkes

Publications and source records attributed to E. Mirkes.

27 records · Page 2Linked to original sources

Polarization Effects in Drell-Yan Type Processes h_1+h_2 -> (W,Z,γ*,J/psi)+X

The measurement of the angular distribution of leptons from the decay of a $W$, $Z$, $γ^{\ast}$, or $\Jpsi$ produced at high transverse momentum in hadronic collisions provides a detailed test of the production and decay mechanism of the spin one state. In the absence of cuts on the final state leptons, the lepton angular distribution in the lepton pair rest frame is determined by the polarization of the spin one state. At leading order in perturbative QCD the general structure of the decay lepton distribution arising from a $W,Z [γ^{\ast},\Jpsi]$ is controlled by six [four] invariant structure functions. In the presence of cuts, the lepton angular distributions are dominated by kinematic effects rather than polarization effects. We present Monte Carlo studies for Tevatron energies and discuss how polarization effects can be highlighted in the presence of cuts.

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Complete O(alpha_s^2) Corrections to (2+1) Jet Cross Sections in Deep Inelastic Scattering

Complete next-to leading order QCD predictions for (2+1) jet cross sections and jet rates in deep inelastic scattering (DIS) based on a new parton level Monte Carlo program are presented. All relevant helicity contributions to the total cross section are included. Results on total jet cross sections as well as differential distributions in the basic kinematical variables $x,W^2$ and $Q^2$ are shown for HERA energies and for the fixed target experiment E665 at FERMILAB. We study the dependence on the choices of the renormalization scale $μ_R$ and the factorization scale $μ_F$ and show that the NLO results are much less sensitive to the variation of $μ=μ_F=μ_R$ than the LO results. The effect of an additional $p_T$ cut to our jet definition scheme is investigated.

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Testing J/psi Production and Decay Properties in Hadronic Collisions

The polar and azimuthal angular distributions for the lepton pair arising from the decay of a J/psi meson produced at transverse momentum p_T balanced by a photon [or gluon] in hadronic collisions are calculated in the color singlet model (CSM). It is shown that the general structure of the decay lepton distribution is controlled by four invariant structure functions, which are functions of the transverse momentum and the rapidity of the J/psi. We found that two of these structure functions [the longitudinal and transverse interference structure functions] are identical in the CSM. Analytical and numerical results are given in the Collins-Soper and in the Gottfried-Jackson frame. We present a Monte Carlo study of the effect of acceptance cuts applied to the leptons and the photon for J/psi+ gamma production at the Tevatron.

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W and Z Polarization Effects in Hadronic Collisions

A Monte Carlo study of the polar and azimuthal angular distributions of the lepton pair arising from the decay of a $W$ or $Z$ boson produced at high transverse momentum in hadronic collisions is presented. In the absence of cuts on the final state leptons, the lepton angular distribution in the gauge boson rest frame is determined by the gauge boson polarization. Numerical results for the lepton angular distributions in the Collins--Soper frame with acceptance cuts and energy resolution smearing applied to the leptons are presented. In the presence of cuts, the lepton angular distributions are dominated by kinematic effects rather than polarization effects, however, some polarization effects are still observable on top of the kinematic effects. Polarization effects are highlighted when the experimental distributions are divided by the Monte Carlo distributions obtained using isotropic gauge boson decay.

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Jet Production in Polarized Lepton-Hadron Scattering

We calculate exact analytical expressions for \oas 3-jet and \oasz \\ 4-jet cross sections in polarized deep inelastic lepton nucleon scattering. Introducing an invariant jet definition scheme, we present differential distributions of 3- and 4-jet cross sections in the basic kinematical variables $x$ and $W^2$ as well as total jet cross sections and show their dependence on the chosen spin-dependent (polarized) parton distributions. Noticebly differences in the predictions are found for the two extreme choices, i.e. a large negative sea-quark density or a large positive gluon density. Therefore, it may be possible to discriminate between different parametrizations of polarized parton densities, and hence between the different physical pictures of the proton spin underlying these parametrizations.

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Single-Lepton Top Signals with a b-Tag at the Tevatron

Events with a leptonic W-decay plus jets should contain top-quark signals, but a QCD W+jets background must be separated. We compare transverse W-momentum, jet multiplicity, and b-tagging separation criteria, and find that the main background after tagging comes from mistagging. We illustrate how to extract the mass m_t via event reconstructions and how to confirm signal purity by lepton angular distributions.

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Exotic Bound State Production at Hadron Colliders

Hadronic production of nonrelativistic boundstates of $b^{\prime}$ or isosinglet quarks D with suppressed weak decays is investigated for LHC and SSC energies. QCD corrections to production and decay rates are incorporated. Large rates for final states from $η_{b^{\prime}}\rightarrow HZ$ are predicted.

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Measuring the Wess-Zumino Anomaly in Tau Decays

We propose to measure the Wess-Zumino anomaly contribution by considering angular distributions in the decays $τ\toν_τηπ^{-}π^{0}$, $τ\toν_τK^- π^{-} K^+ $ and $τ\toν_τK^- π^- π^+$. Radial excitations of the $K^*$, which cannot be seen in $e^++e^-$, should be observed in the $ K^- π^+ π^-$ decay channel.

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QCD Corrections to Toponium Production at Hadron Colliders

Toponium production at future hadron colliders is investigated. Perturbative QCD corrections to the production cross section for gluon fusion are calculated as well as the contributions from gluon-quark and quark-antiquark collisions to the total cross section. The dependence on the renormalization and factorization scales and on the choice of the parton distribution functions is explored. QCD corrections to the branching ratio of $η_{t}$ into $γγ$ are included and the two-loop QCD potential is used to predict the wave function at the origin. The branching ratio of $η_{t}$ into $γZ$, $ZZ$, $HZ$ and $WW$ is compared with the $γγ$ channel.

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