arXiv subjects

P. Osland

Publications and source records attributed to P. Osland.

103 records · Page 6Linked to original sources

arXiv1998

On the phenomenology of a Z' coupling only to third-family fermions

The phenomenology of an additional U(1) neutral gauge boson Z' coupled to the third family of fermions is discussed. One might expect such a particle to contribute to processes where taus, b and t quarks are produced. Precision data from LEP1 put severe constraints on the mixing and heavy-boson mass. We find that the effects of such a particle could not be observed at hadronic colliders, be it at the Tevatron or the LHC, because of the QCD background. At LEP2 and future e^+e^- linear colliders, one could instead hope to observe such effects, in particular for b\bar b final states.

hep-ph↗

arXiv1998

Two-loop three-gluon vertex in zero-momentum limit

The two-loop three-gluon vertex is calculated in an arbitrary covariant gauge, in the limit when one of the external momenta vanishes. The differential Ward-Slavnov-Taylor (WST) identity related to this limit is discussed, and the relevant results for the ghost-gluon vertex and two-point functions are obtained. Together with the differential WST identity, they provide another independent way for calculating the three-gluon vertex. The renormalization of the results obtained is also presented.

hep-ph↗

arXiv1997

Event Orientation in e+e- Annihilation

We review the orientation of e+e- \to q\bar q g events in terms of the polar and azimuthal angles of the event plane w.r.t. the electron beam direction. The asymmetry of the azimuthal-angle distribution is, like the left-right forward-backward polar-angle asymmetry, sensitive to parity-violating effects in three-jet events; these are presently being explored experimentally. We present these observables at O(α_s) in perturbative QCD and discuss their dependence on longitudinal beam polarisation and c.m. energy. A moments analysis in terms of the orientation angles allows a more detailed test of QCD by isolating the independent helicity cross-sections.

hep-ph↗

arXiv1997

Optimal observables for new-physics search at LEP2

New observables σ_\pm for the process e^+e^-\toμ^+μ^- allow one to get more direct information on additional Z' boson effects than what is obtained from the canonical ones, σand A_{FB}. Their deviations from the Standard Model predictions have very specific energy dependences, which are precisely determined by SM parameters. At energies varying from TRISTAN to LEP2, one can uniquely predict the signs of Δσ_{\pm} induced by a Z' as well as the locations of their extrema and zeros. This unambiguous energy correlation could be quite useful in distinguishing effects due to Z' exchange from those caused by other new physics sources. Furthermore, there are two energy points, \sqrt{s_{+}}\simeq 78 GeV and \sqrt{s_{-}}\simeq 113 GeV, where the SM quantities σ_\pm^{SM} as well as the deviations Δσ_{\pm} attain their minimum values or vanish. These points could be very favourable for a search for new physics beyond the SM and beyond Z' effects.

hep-ph↗

arXiv1997

The Effective Lagrangian of QED with a Magnetic Charge and Dyon Mass Bounds

The effective Lagrangian of QED coupled to dyons is calculated. The resulting generalization of the Euler-Heisenberg Lagrangian contains non-linear P and T noninvariant terms corresponding to the virtual pair creation of dyons. The corresponding P and T violating part of the matrix element for light-by-light scattering is considered. This effect induces an electric dipole moment for the electron, of order M^{-2}, where M is the dyon mass. The current limit on the electric dipole moment of the electron yields the lower dyon mass bound M > 1 TeV.

hep-ph↗

arXiv1997

Three-Jet Event Orientation in e+e- Annihilation: New Tests of the Standard Model

We discuss the orientation of e+e- -> q qbar g events in terms of the polar and azimuthal angles of the event plane w.r.t. the electron beam direction. We define an asymmetry of the azimuthal-angle distribution, which, along with the left-right forward-backward polar-angle asymmetry, is sensitive to parity-violating effects in three-jet events; these have yet to be explored experimentally. We have evaluated these observables at O(alpha_s) in perturbative QCD and present their dependence on longitudinal beam polarisation and c.m. energy. We also define a moments analysis in terms of the orientation angles that allows a new and more detailed test of QCD by isolating the six independent helicity cross-sections.

hep-ph↗

arXiv1996

Z' interference effects from TRISTAN to LEP2

We discuss the potential of present e^+e^- colliders to probe for a heavy Z^' boson via its interference effects, in a model-independent framework. The leptonic channel is unambiguous, and thus favourable over the hadronic ones. The effect on the leptonic cross section $σ_{μμ}$, induced by a heavy Z^' with arbitrary couplings, is uniquely determined at LEP2 energies. It results in a negative deviation from the standard model prediction, due to destructive $γ-Z'$ and Z-Z' interferences. At TRISTAN energies the former dominates and is given by the vector coupling of the Z^'. Around the Z peak, the Z-Z' interference dominates and depends on the axial-vector coupling. The forward-backward asymmetry is complementary to $σ_{μμ}$ in the Z^' search. Comparison of the e^+e^- potentials indicates that already after one year of operation, LEP2 will achieve a sensitivity to Z^' that exceeds the current one at TRISTAN.

hep-ph↗

arXiv1996

Lightest MSSM Higgs Boson Production and its Two-Photon Decay at the LHC

We present an analysis of the production and two-photon decay of the lightest CP-even Higgs boson of the Minimal Supersymmetric Standard Model (MSSM) at the Large Hadron Collider (LHC). A rather general model is considered, without supergravity constraints. All parameters of the model are taken into account, we especially study the dependence of the cross section on the squark masses, on the bilinear parameter $μ$ and the trilinear supersymmetry breaking parameter $A$. Non-zero values of these parameters lead to significant mixing in the squark sector, and, thus, affect the masses of Higgs bosons through radiative corrections, as well as their couplings to squarks. The cross section times the two-photon branching ratio of $h^0$ is of the order of 15--25~fb in much of the parameter space that remains after imposing the present experimental constraints on the parameters.

hep-ph↗

arXiv1996

Three-gluon vertex in arbitrary gauge and dimension

One-loop off-shell contributions to the three-gluon vertex are calculated, in arbitrary covariant gauge and in arbitrary space-time dimension, including quark-loop contributions (with massless quarks). It is shown how one can get the results for all on-shell limits of interest directly from the general off-shell expression. The corresponding general expressions for the one-loop ghost-gluon vertex are also obtained. They allow for a check of consistency with the Ward--Slavnov--Taylor identity.

hep-ph↗

arXiv1996

One-loop results for three-gluon vertex in arbitrary gauge and dimension

We review the calculation of one-loop contributions to the three-gluon vertex, for arbitrary (off-shell) external momenta, in arbitrary covariant gauge and in arbitrary space-time dimension. We discuss how one can get the results for all on-shell limits of interest directly from the general off-shell expression.

hep-ph↗

arXiv1996

The Effective Lagrangian of QED with a Magnetic Charge

The effective Lagrangian of QED coupled to dyons is calculated. The resulting generalization of the Euler-Heisenberg Lagrangian contains non-linear $P$- and $T$-nonivariant (but $C$ invariant) terms corresponding to the virtual pair creation of dyons. As examples, the amplitudes for photon splitting and photon coalescence are calculated.

hep-th↗

arXiv1996

The Two-Photon Decay Mode of MSSM Higgs Bosons at the Large Hadron Collider

At the Large Hadron Collider (LHC), the CP-even Higgs bosons ($h^0$ and $H^0$) of the Minimal Supersymmetric Standard Model (MSSM) will be searched for mainly through their two-photon decay. We present a detailed analysis of the production and two-photon decay of the CP-even Higgs bosons of MSSM at the LHC by taking into account all the parameters of the model, especially the bilinear parameter $μ$ and the trilinear supersymmetry breaking parameter $A$. Non-zero values of these parameters lead to significant mixing in the squark sector, and, thus, affect the masses of Higgs bosons through radiative corrections, as well as their couplings to squarks. The dependence of the cross section for the production of Higgs, and its subsequent decay to two photons, on various parameters of the MSSM is described in detail. The cross section times the two-photon branching ratio of $h^0$ is of the order of 15--25~fb in much of the parameter space that remains after imposing the present experimental constraints on the parameters. For the $H^0$, the two-photon branching ratio is only significant if it is light. With a light $H^0$ the cross section times the branching ratio may be 200~fb or more.

hep-ph↗

arXiv1995

Production and Two-photon Decay of the MSSM Scalar Higgs Bosons at the LHC

We consider the production and two-photon decay of the $CP$-even Higgs bosons ($h^0$ and $H^0$) of the Minimal Supersymmetric Standard Model (MSSM) at the Large Hadron Collider. We study in detail the dependence of the cross section on various parameters of the MSSM, especially the dependence on the mixing effects in the squark sector due to the Higgs bilinear parameter $μ$ and the soft supersymmetry breaking parameter $A$. We find that the cross section for the production of these Higgs bosons has a significant dependence on the parameters which determine the chiral mixing in the squark sector. The cross section times the two-photon branching ratio of $h^0$ is of the order of 15--25~fb in much of the parameter space that remains after imposing the present experimental constraints. For the $H^0$ the two-photon branching ratio is only significant if the $H^0$ is light, but then the cross section times the branching ratio may exceed 200~fb. The QCD corrections due to quark loop contributions are known to increase the cross section by 50\%. We find the dependence of the cross section on the gluon distribution function used to be rather insignificant.

hep-ph↗