Searcharxiv⌕ Search

arXiv subjects

Arnd Leike

Publications and source records attributed to Arnd Leike.

17 recordsLinked to original sources
arXiv2000

Discovery and Identification of W' Bosons in e gamma to nu q +X

We examine the sensitivity of the process e gamma to nu q +X to W' bosons which arise in various extensions of the standard model. We consider photon spectra from both the Weizsacker Williams process and from a backscattered laser. The process is found to be sensitive to W' masses up to several TeV, depending on the model, the center of mass energy, the integrated luminosity, and assumptions regarding systematic errors. If extra gauge bosons were discovered first in other experiments, the process could also be used to measure W' couplings. This measurement would provide information that could be used to unravel the underlying theory, complementary to measurements at the Large Hadron Collider.

hep-ph↗
arXiv2000

Constraints on Extra Gauge Bosons in e gamma Collisions

We investigate the sensitivity of e- gamma ---> nu_e nu_mu(bar) mu- to extra charged gauge bosons. The sensitivity is much below that of e-e+ ---> nu nu(bar) gamma. We conclude that e- gamma ---> d u(bar) nu_e and e- gamma ---> f f(bar) e- are also inferior to e+e- collisions in setting bounds on extra charged and neutral gauge bosons and on four fermion contact interactions.

hep-ph↗
arXiv2000

Discovery and Identifictation of Extra Gauge Bosons in e^+e^- -> nu nubar gamma

We examine the sensitivity of the process e+e- -> nu nubar gamma to extra gauge bosons, Z' and W', which arise in various extensions of the standard model. The process is found to be sensitive to W' masses up to several TeV, depending on the model, the center of mass energy, and the assumed integrated luminosity. If extra gauge bosons were discovered first in other experiments, the process could also be used to measure Z' nu nubar and W' couplings. This measurement would provide information that could be used to unravel the underlying theory, complementary to measurements at the Large Hadron Collider.

hep-ph↗
arXiv1999

Constraints on Couplings of Extra Gauge Bosons from e+e- --> nu nubar gamma

If extra gauge bosons are observed at the LHC or at a linear e+e- collider, the reaction e+e- --> nu nubar gamma can give information on the couplings (W' nu l) and (Z' nu nubar). The total cross section and polarization asymmetries are the most sensitive observables for such a measurement. Small systematic errors are crucial to obtain reasonable coupling constraints, especially for a high luminosity collider.

hep-ph↗
arXiv1997

Scaling of Z' limits at the Linear Collider

Z' exclusion limits and errors of Z' model measurements are compared for different reactions at future linear colliders. The influence of the c.m. energy, integrated luminosity, beam polarization and systematic errors is discussed. The sensitivity to a Z' depends only on the product Ls and not on the integrated luminosity and the c.m. energy separately.

hep-ph↗
arXiv1995

Production of B_c Mesons in Photon-Photon and Hadron-Hadron Collisions

We discuss two-photon and hadronic production of $B_c$ mesons in nonrelativistic bound state approximation and to lowest order in the coupling constants $α$ and $α_s$. It is shown that in photon-photon collisions, heavy quark fragmentation is dominated by recombination of $\bar b$ and $c$ quarks up to the highest accessible transverse momenta. In contrast, in hadroproduction, which at high energies mainly involves gluon--gluon collisions, the fragmentation mechanism dominates at transverse momenta $p_T > m_{B_c}$, providing a simple and satisfactory approximation of the complete $O(α_s^4)$ results in the high-$p_T$ regime. Contradictions in previous publications on hadroproduction of $B_c$ mesons are clarified. We also present predictions for cross sections and differential distributions at present and future accelerators.

hep-ph↗
arXiv1995

S-Matrix Approach to the $Z$ Line Shape

We analyze the $Z$ line shape assuming the existence of an analytic, unitary S-matrix. As an example, from hadron production at LEP we determine $M_{Z}=91.134 \pm 0.020 \pm 0.020 \: ({\rm LEP})$ GeV, $Γ_{Z}=2.506 \pm 0.018$ GeV. This is in accordance with earlier results after performing a shift of the $Z$ mass value of about $\frac{1}{2}Γ_Z^2/M_Z = 34$ MeV. The cross section and related observables may be described by a small number of additional degrees of freedom without relying on a specific field-theoretic model.

hep-ph↗
arXiv1995

ZZ' Mixing and Radiative Corrections at LEP I

We present a method for a common treatment of $Z'$ exchange, QED corrections, and weak loops in $e^+ e^-$ annihilation. QED corrections are taken into account by convoluting a hard-scattering cross section containing $γ,\ Z,$ and $Z'$ exchange. Weak corrections and $ZZ'$ mixing are treated simultaneously by a generalization of weak form factors. Using the properly extended Standard Model program for the $Z$ line shape, ZFITTER, we perform and compare two different analyses of the 1990 LEP~I data in terms of theories based on the E$_6$-group and in terms of LR-symmetric models. From the LEP~I data alone, the $ZZ'$ mixing angle may be limited to $|θ_M| \le 0.01$ and the $Z'$ mass to $M_2 > 118$--148 GeV, depending on the model (95\%~CL).

hep-ph↗
arXiv1995

SEMIANALYTIC DISTRIBUTIONS IN FOUR FERMION NEUTRAL CURRENT PROCESSES

Analytical formulae for triple differential distributions ${\rm d}^3σ/({\rm d}\cosθ{\rm d}s_1{\rm d}s_2)$ in the neutral current process $e^+e^-\rightarrow f_1\bar f_1 f_2\bar f_2$ are given. They allow to obtain angular distributions, rapidity distributions and transversal momentum distributions of one fermion pair by only two numerical integrations. Cuts can be applied to the integration variables.

hep-ph↗
arXiv1995

PRODUCTION OF $B_c$ MESONS IN HADRONIC COLLISIONS

We investigate hadroproduction of $B_c$ mesons from initial gluons using QCD perturbation theory and nonrelativistic bound state approximations. Our results obtained by two completely independent calculations are confronted with existing results which contradict each other. Moreover, we examine the approximation based on heavy quark fragmentation and determine the range of validity of it. Predictions for cross sections and differential distributions at Tevatron and LHC energies are presented.

hep-ph↗
arXiv1995

Higgs production in $e^+ e^- \to l{\bar l} q{\bar q}$ at LEP and NLC

Predictions for Higgs production with processes of the type $e^+ e^- \rightarrow μ{\bar μ}\;b\bar b $ at LEP~2 and the NLC are calculated. Short analytical formulae describe the double differential distribution in the invariant masses of the $μ\bar μ$ and $b \bar{b}$ pairs. The total cross section may be got with two numerical integrations. The various Higgs-background interferences vanish either identically or are small. The background contributions depend strongly on cuts applied on the invariant masses.

hep-ph↗
arXiv1994

THE PROCESS $e^+ e^- \rightarrow l \bar l q \bar q$ AT LEP AND NLC

The cross sections for the reaction $e^+ e^- \rightarrow l \bar l q \bar q $ and for similar four fermion production processes at LEP~1, LEP~2 and the NLC are calculated. Due to the extraordinary symmetry properties of the process, very compact analytical formulae describe the double differential distributions in the invariant masses of the $l \bar l$ and $q \bar{q}$ pairs. The total cross sections may be obtained with two numerical integrations.

hep-ph↗
arXiv1993

Model Independent $Z'$ Constraints at Future $e^+e^-$ Colliders}

Model independent constraints on the mass of extra neutral gauge bosons and their couplings to charged leptons are given for LEP~II and a 500\,GeV $e^+e^-$ collider. Analytical exclusion limits are derived in the Born approximation. The $Z'$ limits obtained with radiative corrections are always worse than those calculated at the Born level. Polarized beams are only useful for degrees of polarization essentially larger than 50\%. Known discovery limits on extra $Z$ bosons predicted by popular $Z'$ models are reproduced as special cases. The $Z'$ constraints are compared to those predicted by four fermion contact interactions.

hep-ph↗
arXiv1993

Experimental Constraints on the Scale of New Physics in Top Condensate Models

We obtain mass limits on the extra neutral gauge boson which is predicted in a model with hidden gauge symmetry and dynamical breaking of the electroweak symmetry by a top quark condensate. For typical model assumptions, present LEP data exclude masses below 3\,TeV. With LEP200 or an electron-positron collider of a c.m. energy of 500 GeV masses below 15\,TeV or 50\,TeV could be excluded, respectively. Such high mass limits allow the calculation of the observables used in the analysis in the context of the Nambu-Jona-Lasinio model.

hep-ph↗