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S. Keller

Publications and source records attributed to S. Keller.

32 records · Page 2Linked to original sources
arXiv1998

Compositeness Test at the FMC with Bhabha Scattering

It is possible that quarks and/or leptons have substructure that will become manifest at high energies. Here we investigate the limits on the muon compositeness scale that could be obtained at the First Muon Collider using Bhabha scattering. We study this limit as a function of the collider energy and the angular cut imposed by the detector capability.

hep-ph↗
arXiv1997

Summary of the Very Large Hadron Collider Physics and Detector Workshop

One of the options for an accelerator beyond the LHC is a hadron collider with higher energy. Work is going on to explore accelerator technologies that would make such a machine feasible. This workshop concentrated on the physics and detector issues associated with a hadron collider with an energy in the center of mass of the order of 100 to 200 TeV.

hep-ph↗
arXiv1997

QED Radiative Corrections to $Z$ Boson Production and the Forward Backward Asymmetry at Hadron Colliders

The ${\cal O}(α)$ radiative corrections to the process $p\,p\hskip-7pt\hbox{$^{^{(\!-\!)}}$} \rightarrow γ^*, \, Z \rightarrow \ell^+ \ell^-$ ($\ell=e,\,μ$) are calculated. Factorizing the collinear singularity associated with initial state photon bremsstrahlung into the parton distribution functions, we find that initial state corrections have a much smaller effect than final state radiative corrections. Due to mass singular logarithmic terms associated with photons emitted collinear with one of the final state leptons, QED radiative corrections strongly affect the shape of the di-lepton invariant mass distribution, the lepton transverse momentum spectrum, and the forward backward asymmetry, $A_{FB}$. They lead to a sizeable shift in the $Z$ boson mass extracted from data, decrease the di-lepton cross section by up to 10\%, and increase the integrated forward backward asymmetry in the $Z$ peak region by about 7\% at the Tevatron. We also investigate how experimental lepton identification requirements modify the effect of the QED corrections, and study the prospects for a high precision measurement of $\sin^2θ^{lept}_{eff}$ using the forward backward asymmetry at the Large Hadron Collider (LHC).

hep-ph↗
arXiv1997

Determination of W-boson Properties at Hadron Colliders

Methods for measuring the W-boson properties at hadron colliders are discussed. It is demonstrated that the ratio between the W- and Z-boson observables can be reliably calculated using perturbative QCD, even when the individual W- and Z-boson observables are not. Hence, by using a measured Z-boson observable and the perturbative calculation of the ratio of the W- over Z-boson observable, we can accurately predict the W-boson observable. The use of the ratio reduces both the experimental and theoretical systematic uncertainties substantially. Compared to the currently used methods it might, at high luminosity, result in a smaller overall uncertainty on the measured W-boson mass and width.

hep-ph↗
arXiv1996

Measuring the mass of the W at the LHC

We explore the ability of the Large Hadron Collider to measure the mass of the W boson. We believe that a precision better than ~ 15 MeV could be attained, based on a year of operation at low luminosity (10^(33)cm^(-2)s^(-1)). If this is true, this measurement will be the world's best determination of the W mass. We feel this interesting opportunity warrants investigation in more detail.

hep-ph↗
arXiv1994

W Plus Heavy Quark Production at the Tevatron

We summarize the motivations for and the status of the calculation of the $W +$ heavy quark production process in $p \bar p$ colliders to Next-to-Leading Order in QCD. This process can be used to constrain the strange quark distribution function at high $Q^2$ at the Tevatron, and also to study the bottom content of $W+1$~jet events. In addition, when crossed, the calculation essentially describes the single top quark production process to Next-to-Leading Order in QCD.

hep-ph↗
arXiv1993

The Charm Content of W+1 Jet Events as a Probe of the Strange Quark Distribution Function

We investigate the prospects for measuring the strange quark distribution function of the proton in associated $W$ plus charm quark production at the Tevatron. The $W+c$ quark signal produced by strange quark -- gluon fusion, $sg\rightarrow W^-c$ and $\bar sg\rightarrow W^+\bar c$, is approximately 5\% of the inclusive $W+1$ jet cross section for jets with a transverse momentum $p_T(j)>10$~GeV. We study the sensitivity of the $W$ plus charm quark cross section to the parametrization of the strange quark distribution function, and evaluate the various background processes. Strategies to identify charm quarks in CDF and DØ\ are discussed. For a charm tagging efficiency of about 10\% and an integrated luminosity of 30~pb$^{-1}$ or more, it should be possible to constrain the strange quark distribution function from $W+c$ production at the Tevatron.

hep-ph↗
arXiv1993

Measuring the Longitudinally Polarized Proton Gluon Distribution using Photoproduction Processes

Little information is known about the polarization of gluons inside a longitudinally polarized proton. We investigate the sensitivity of photoproduction experiments with both beam and target longitudinally polarized to the polarization of the gluon distribution in the proton. We study the photoproduction of jets and heavy quarks and conclude that they are both sensitive to the gluon polarization.

hep-ph↗
arXiv1993

Measurement of the Strange Quark Distribution Function in W + Charm Quark Events

We investigate the prospects of measuring the strange quark distribution function at the Tevatron, using $W$ plus charm quark events. The $W$ plus charm quark signal produced by strange quark--gluon fusion, $sg\rightarrow W^-c$ and $\bar sg\rightarrow W^+\bar c$, is approximately 5\% of the inclusive $W+1$ jet cross section for jets with a transverse momentum $p_T(j)>10$~GeV. We study the sensitivity of the $W$ plus charm quark cross section to the parametrization of the strange quark distribution function, and evaluate the various background processes. Strategies to identify charm quarks in CDF and D$0\llap/$ are briefly described.

hep-ph↗