TESLA Technical Design Report, Part VI, Chapter 1: The Photon Collider at TESLA
TESLA Technical Design Report, Part VI, Chapter 1: The Photon Collider at TESLA
hep-ex↗
arXiv subjects
M. Klasen
Publications and source records attributed to M. Klasen.
J/psi plus dijet associated production in two-photon collisions
We study the production of a J/psi meson in association with one or two jets in gamma gamma collisions concentrating on the direct-photon contribution, which is expected to be dominant for large J/psi-meson transverse momentum and/or large dijet invariant mass. We work at leading order in the factorization formalism of nonrelativistic QCD and include all relevant colour-octet processes. We present distributions in J/psi-meson transverse momentum and rapidity appropriate for CERN LEP2, a future e^+e^- linear collider, and a possible gamma gamma collider mode of the latter. In the case of the e^+e^- linear collider, we assume the beamstrahlung spectrum appropriate for DESY TESLA.
hep-ph↗
Status of Hard Interactions (Jets and Heavy Flavor)
We review the status of hard interactions, in particular of jet and heavy flavor production, at HERA and LEP. Emphasis is given to recent theoretical developments. Instantons, event shapes, and prompt photons are also briefly discussed.
hep-ph↗
The pion structure function and jet production in $γp \to n X$
Despite its theoretical and practical importance, the pion structure is still badly constrained, particularly at low $x_π$ and in the sea-quark and gluon sectors. Recently ZEUS have presented data on dijet photoproduction with a leading neutron, which is dominated by slightly off-shell pion exchange and can be used to constrain the pion densities down to $x_π\simeq 0.01$. We compare a recent NLO calculation to the ZEUS data and find that the lower gluon densities of SMRS seem to be preferred by the data. Theoretical uncertainties, in particular from the pion flux, are discussed in some detail.
hep-ph↗
Jet Photoproduction at THERA
We demonstrate that a future high-energy electron-proton collider like THERA could largely extend the current HERA program in jet photoproduction of testing QCD and determining the partonic structure of the proton and the photon. Depending on the electron beam energy (250-500 GeV) and the collider mode ($ep$ or $γp$), the range in the hard transverse energy scale of the jets could be increased by a factor of 2-3 and the reach in the momentum fraction $x$ of the partons in the proton or photon by at least one order of magnitude. It would thus become possible to check the determinations of the gluon density in the proton obtained in deep-inelastic scattering experiments, to measure the gluon density in the photon down to low values of $x$, and to study the QCD dynamics in multi-jet events.
hep-ph↗
Photoproduction of Jets on a Virtual Pion Target in Next-to-Leading Order QCD
Differential cross sections for inclusive dijet photoproduction on a virtual pion have been calculated in next-to-leading order QCD as a function of $E_T, η$, and $x_π$. The cross sections are compared with recent ZEUS data on photoproduction of dijets with a leading neutron in the final state.
hep-ph↗
Next-to-leading Order Calculation of Associated Production of Gauginos and Gluinos
Results are presented of a next-to-leading order calculation in perturbative QCD of the production of charginos and neutralinos in association with gluinos at hadron colliders. Predictions for total and differential cross sections are shown at the energies of the Fermilab Tevatron and CERN Large Hadron Collider for a typical supergravity model of the sparticle mass spectrum and for a light gluino model.
hep-ph↗
Next-to-leading Order SUSY-QCD Calculation of Associated Production of Gauginos and Gluinos
Results are presented of a next-to-leading order calculation in perturbative QCD of the production of charginos and neutralinos in association with gluinos at hadron colliders. Predictions for cross sections are shown at the energies of the Fermilab Tevatron and CERN Large Hadron Collider for a typical supergravity (SUGRA) model of the sparticle mass spectrum and for a light gluino model.
hep-ph↗
Constraints on the Proton's Gluon Density from Lepton-Pair Production
Massive lepton-pair production, the Drell-Yan process, should be a good source of independent constraints on the gluon density, free from the experimental and theoretical complications of photon isolation that beset studies of prompt photon production. We provide predictions for the spin-averaged and spin-dependent differential cross sections as a function of transverse momentum $Q_T$.
hep-ph↗
Sfermion production at photon colliders
We calculate total and differential cross sections for sfermion production in $e^+e^-$ annihilation and in photon-photon collisions with arbitrary photon polarization. The total cross section at a polarized photon collider is shown to be larger than the $e^+e^-$ annihilation cross section up to the kinematic limit of the photon collider.
hep-ph↗
Sfermion Pair Production in Polarized and Unpolarized $γγ$ Collisions
We calculate total and differential cross sections for the production of sfermion pairs in photon-photon collisions, including contributions from resolved photons and arbitrary photon polarization. Sfermion production in photon collisions depends only on the sfermion mass and charge. It is thus independent of the details of the SUSY breaking mechanism, but highly sensitive to the sfermion charge. We compare the total cross sections for bremsstrahlung, beamstrahlung, and laser backscattering photons to those in $e^+e^-$ annihilation. We find that the total cross section at a polarized photon collider is larger than the $e^+e^-$ annihilation cross section up to the kinematic limit of the photon collider.
hep-ph↗
Parton Distributions Working Group
The main focus of this working group was to investigate the different issues associated with the development of quantitative tools to estimate parton distribution functions uncertainties. In the conclusion, we introduce a "Manifesto" that describes an optimal method for reporting data.
hep-ph↗
Lepton Pair Production at the LHC and the Gluon Density in the Proton
The hadroproduction of lepton pairs with mass $Q$ and finite transverse momentum $Q_T$ is dominated by quark-gluon scattering in the region $Q_T > Q/2$. This feature provides a new independent method for constraining the gluon density with data at hadron collider energies. Predictions are provided at the energy of the LHC.
hep-ph↗
Constraints on the Gluon Density from Lepton Pair Production
The hadroproduction of lepton pairs with mass Q and finite transverse momentum Q_T is described in perturbative QCD by the same partonic subprocesses as prompt photon production. We demonstrate that, like prompt photon production, lepton pair production is dominated by quark-gluon scattering in the region Q_T>Q/2. This feature leads to sensitivity to the gluon density in kinematical regimes accessible in collider and fixed target experiments, and it provides a new independent method for constraining the gluon density.
hep-ph↗
Photon Structure and the Production of Jets, Hadrons, and Prompt Photons
We give a pedagogical introduction to hard photoproduction processes at HERA, including the production of jets, hadrons, and prompt photons. Recent theoretical developments in the three areas are reviewed.
hep-ph↗
Low mass lepton pair production in hadron collisions
The hadroproduction of lepton pairs with mass $Q$ and transverse momentum $Q_T$ can be described in perturbative QCD by the same partonic subprocesses as prompt photon production. We demonstrate that, like prompt photon production, lepton pair production is dominated by quark-gluon scattering in the region $Q_T>Q/2$. This leads to sensitivity to the gluon density in kinematical regimes that are accessible both at collider and fixed target experiments while eliminating the theoretical and experimental uncertainties present in prompt photon production.
hep-ph↗
The Production of Charginos/Neutralinos and Sleptons at Hadron Colliders
We analyse the production of charginos/neutralinos and sleptons at the hadron colliders Tevatron and LHC in the direct channels: $p\bar{p}/pp \to \tildeχ_i \tildeχ_j + X$ and $\tilde{\ell} \bar{\tilde{\ell}'} +X$. The cross sections for these reactions are given in next-to-leading order SUSY QCD. By including the higher-order corrections, the predictions become theoretically stable, being nearly independent of the factorization and renormalization scales. Since the corrections increase the cross sections, the discovery range for these particles is extended in the refined analysis.
hep-ph↗