arXiv subjects
U. Baur
Publications and source records attributed to U. Baur.
Two Photon Radiation in W and Z Boson Production at the Tevatron Collider
We present a calculation of two photon radiation in W and Z boson production in hadronic collisions, based on the complete matrix elements for the processes q\bar q'\to\ell^\pmνγγand q\bar q\to\ell^+\ell^-γγ, including finite charged lepton masses. In order to achieve stable numerical results over the full phase space, multiconfiguration Monte Carlo techniques are used to map the peaks in the differential cross section. Numerical results are presented for the Fermilab Tevatron.
Zero Zeros After All These (20) Years
We celebrate two birthdays connected with the radiation zero phenomenon. First, a striking dip in the theoretical angular distributions of radiative weak-boson production was discovered twenty years ago. The key experimental interest is that this will not occur in any deviation from the standard model. Second, the classical training of Stanley Brodsky began sixty years ago, which was instrumental in understanding why theoretical spin-independent radiation zeros appear in almost all Born amplitudes for the radiation of photons and gluons and other massless gauge bosons (but rarely in physical kinematic regions). And there are approximate zeros for massive bosons and ``Type II'' zeros that can also be studied. We discuss how the difficulties in observing the original Mikaelian-Samuel-Sahdev zero finally may be surmounted next year.
Electroweak Radiative Corrections to W Boson Production at the Tevatron
We discuss the O(alpha) electroweak radiative corrections to W boson production at the Tevatron and their effect on the W boson mass extracted by experiment. The results of a new calculation of the O(alpha) corrections are presented and compared with those of a previous calculation. We also briefly discuss the O(alpha) corrections to Z boson production at the Tevatron and two-photon radiation in W and Z events.
Electroweak Radiative Corrections to W Boson Production in Hadronic Collisions
The O(α) electroweak radiative corrections to the process pp, ppbar\to W \to\ell^\pmν(\ell=e,μ) are calculated. The O(α) corrections can be decomposed into separately gauge invariant contributions to the W boson production and decay processes. Factorizing the collinear singularity associated with initial state photon radiation into the parton distribution functions, we find that initial state corrections have a significantly smaller effect than final state radiative corrections. We study in detail the effect of electroweak radiative corrections on a number of interesting observables: the W transverse mass distribution, the W to Z transverse mass ratio, the charge asymmetry of leptons in W\to\ellνdecays, as well as the W production cross section and the W to Z cross section ratio. We also investigate how experimental lepton identification requirements change the effect of the electroweak corrections.
Measuring Trilinear Gauge Boson Couplings at Hadron and Lepton Colliders
We discuss the measurement of the $WWV$ ($V=γ,\, Z$) gauge boson couplings in present and future collider experiments. The major goals of such experiments will be the confirmation of the Standard Model (SM) predictions and the search for signals of new physics. The present limits on these couplings from Tevatron and LEP2 experiments as well as the expectations from future hadron and lepton collider experiments are summarized. We also study the impact of initial state radiation on the sensitivity limits which can be achieved at the NLC and a $μ^+μ^-$ collider.
QCD Corrections and Anomalous Couplings in $Zγ$ Production at Hadron Colliders
The processes $pp/ pbar p \to Z γ+ X \to \ell^+ \ell^- γ+ X$ ($\ell=e, μ$) and $pp/ pbarp \to Z γ+ X \to \barννγ+ X$ are calculated to ${\cal O}(α_s)$ for general $ZZγ$ and $Zγγ$ couplings. The impact of ${\cal O}(α_s)$ QCD corrections on the observability of $ZZγ$ and $Zγγ$ couplings in $Zγ$ production at the Tevatron and the Large Hadron Collider (LHC) is discussed.
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.
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).
$Wγγ$ Production at the Fermilab Tevatron Collider: Gauge Invariance and Radiation Amplitude Zero
The electroweak process $p\bar p \to \ell^\pmνγγ$ is calculated at tree level, including finite W width effects. In order to obtain a gauge invariant amplitude, the imaginary parts of $WWγ$ triangle graphs and $WWγγ$ box diagrams have to be included, in addition to resumming the imaginary contributions to the W polarization. We demonstrate the existence of a radiation amplitude zero in $p\bar p \to W^\pm γγ\to \ell^\pmνγγ$, and discuss how it may be observed in correlations of the $γγ$ and lepton rapidities at the Fermilab Tevatron.
Anomalous Gauge Boson Couplings
The measurement of anomalous gauge boson self couplings is reviewed for a variety of present and planned accelerators. Sensitivities are compared for these accelerators using models based on the effective Lagrangian approach. The sensitivities described here are for measurement of generic parameters kappa_v, lambda_v, etc., defined in the text. Pre-LHC measurements will not probe these couplings to precision better than O(1/10). The LHC should be sensitive to better than O(1/100), while a future NLC should achieve sensitivity of O(1/1000) to O(1/10000) for center of mass energies ranging from 0.5 to 1.5 TeV.
Precision Electroweak Physics at Future Collider Experiments
We present an overview of the present status and prospects for progress in electroweak measurements at future collider experiments leading to precision tests of the Standard Model of Electroweak Interactions. Special attention is paid to the measurement of the W mass, the effective weak mixing angle, and the determination of the top quark mass. Their constraints on the Higgs boson mass are discussed.
Electroweak Radiative Corrections to W Boson Production at the Tevatron
We present some results of a new calculation of the O(alpha) electroweak radiative corrections to W boson production at hadron colliders with special emphasis on the transverse mass distribution.
Implications of $μνγγ$ Production on Precision Measurement of the W Mass
The process $p \bar p \rightarrow μ^- \bar νγγ$ is calculated including finite lepton mass effects. Implications for precision measurements of the $W$ mass at the Tevatron are discussed.
Electroweak Radiative Corrections to $W$ and $Z$ Boson Production in Hadronic Collisions
Some results of a calculation of electroweak radiative corrections to $W$ and $Z$ boson production in hadronic collisions are presented.
Anomalous Couplings and Chiral Lagrangians: An Update
We present an update of the limits expected for anomalous gauge boson couplings in the language of chiral Lagrangian operators at the LHC and the Linear Collider. Both, the $e^+e^-$ and the $γγ$ mode of the Linear Collider are analyzed. With a 500~GeV $e^+e^-$ collider, and an integrated luminosity of 50~--~80~fb$^{-1}$, one reaches the domain of precision measurements.
Self-Couplings of Electroweak Bosons: Theoretical Aspects and Tests at Hadron Colliders
The current theoretical understanding of anomalous gauge boson couplings is reviewed, and the direct measurement of these couplings in present and future hadron collider experiments is briefly discussed.