Tracking at LHC

Precise tracking is an indispensable tool for the study of many phenomena at new energy frontier accessible with the CERN Large Hadron Collider (LHC). The tracking detectors of ATLAS and CMS have been designed to cope with the harsh experimental conditions of the LHC interaction region. In this paper, we discuss and compare the tracking performance of these two detectors

Physics opportunities with future proton accelerators at CERN

We analyze the physics opportunities that would be made possible by upgrades of CERN's proton accelerator complex. These include the new physics possible with luminosity or energy upgrades of the LHC, options for a possible future neutrino complex at CERN, and opportunities in other physics including rare kaon decays, other fixed-target experiments, nuclear physics and antiproton physics, among other possibilities. We stress the importance of inputs from initial LHC running and planned neutrino experiments, and summarize the principal detector R&D issues.Comment: 39 page, word document, full resolution version available from http://cern.ch/pofpa/POFPA-arXive.pd

Exact Results on e+ e- --> e+ e- + 2 Photons at SLC/LEP Energies

We use the spinor methods of the CALKUL collaboration, as realized by Xu, Zhang and Chang, to calculate the differential cross section for e+ e- --> e+ e- + 2 photons for c.m.s. energies in the SLC/LEP regime. An explicit complete formula for the respective cross section is obtained. The leading log approximation is used to check the formula. Applications of the formula to high precision luminosity calculations at SLC/LEP are discussed.Comment: 16 pages(LaTeX), UTHEP-92-0601 (contains corrected figures

Using b→sγb \to s\gamma to Probe Top Quark Couplings

Possible anomalous couplings of the top-quark to on-shell photons and gluons are constrained by the recent results of the CLEO Collaboration on both inclusive and exclusive radiative $B$ decays. We find that the process \bsg\ can lead to reasonable bounds on both the anomalous electric and magnetic dipole moments of the top-quark, while essentially no limits are obtained on the corresponding chromoelectric and chromomagnetic moments, which enter the expression for the decay rate only through operator mixing.Comment: 10 pages plus 6 figures (available by request), LaTex, ANL-HEP-PR-93-3

Gaseous Dark Matter Detectors

Dark Matter detectors with directional sensitivity have the potential of yielding an unambiguous positive observation of WIMPs as well as discriminating between galactic Dark Matter halo models. In this article, we introduce the motivation for directional detectors, discuss the experimental techniques that make directional detection possible, and review the status of the experimental effort in this field.Comment: 19 pages, review on gaseous directional dark matter detectors submitted to New Journal of Physic

A New Model for Fermion Masses in Supersymmetric Grand Unified Theories

We present a simple model for fermion mass matrices and quark mixing in the context of supersymmetric grand unified theories and show its agreement with experiment. Our model realizes the GUT mass relations $m_d=3m_e$, $m_s= m_\mu/3$, $m_b=m_\tau$ in a new way and is easily consistent with values of $m_t$ suggested by MSSM fits to LEP data.Comment: Latex, 8 p., ITP-SB-93-37 (revised version contains minor changes in some wording and citations; no changes in analytic or numerical results.

R_b and New Physics: A Comprehensive Analysis

We survey the implications for new physics of the discrepancy between the LEP measurement of $R_b$ and its Standard Model prediction. Two broad classes of models are considered: ($i$) those in which new Z\bbar b couplings arise at tree level, through $Z$ or $b$-quark mixing with new particles, and ($ii$) those in which new scalars and fermions alter the Z \bbar b vertex at one loop. We keep our analysis as general as possible in order to systematically determine what kinds of features can produce corrections to $R_b$ of the right sign and magnitude. We are able to identify several successful mechanisms, which include most of those which have been recently been proposed in the literature, as well as some earlier proposals (\eg\ supersymmetric models). By seeing how such models appear as special cases of our general treatment we are able to shed light on the reason for, and the robustness of, their ability to explain $R_b$.Comment: 60 pages, 8 figures, plain tex, uses epsf. Final version to appear in Phys. Rev. D; propgating sign error corrected in eqs. 78, 87, 88, 89, 98, and 107; results unchange

Tracing CP violation in the production of top quark pairs by multiple TeV proton-proton collisions

We investigate the possibilities of searching for non-standard CP violation in $pp\to t\bar{t}X$ at multiple TeV collision energies. A general kinematic analysis of the underlying partonic production processes $gg\to t\bar{t}$ and $q\bar{q}\to t\bar{t}$ in terms of their density matrices is given. We evaluate the CP-violating parts of these matrices in two-Higgs doublet extensions of the standard model (SM) and give results for CP asymmetries at the parton level. We show that these asymmetries can be traced by measuring suitable observables constructed from energies and momenta of the decay products of $t$ and $\bar{t}$. We find CP-violating effects to be of the order of $10^{-3}$ and show that possible contaminations induced by SM interactions are savely below the expected signals.Comment: 24 pages, SLAC-PUB-6403, PITHA 93/43, 9 Figs. available upon request. Written in LaTe

Incorporation of QCD Effects in Basic Corrections of the Electroweak Theory

We study the incorporation of QCD effects in the basic electroweak corrections \drcar, \drcarw, and \dr. They include perturbative \Ord{\alpha\alpha_s} contributions and $t\bar{t}$ threshold effects. The latter are studied in the resonance and Green-function approaches, in the framework of dispersion relations that automatically satisfy relevant Ward identities. Refinements in the treatment of the electroweak corrections, in both the \ms\ and the on-shell schemes of renormalization, are introduced, including the decoupling of the top quark in certain amplitudes, its effect on \hat{e}^2(\mz) and \sincarmz, the incorporation of recent results on the leading irreducible \Ord{\alpha^2} corrections, and simple expressions for the residual, i.e.\ ``non-electromagnetic'', parts of \drcar, \drcarw, and \dr. The results are used to obtain accurate values for \mw\ and \sincarmz, as functions of \mt\ and \mh. The higher-order effects induce shifts in these parameters comparable to the expected experimental accuracy, and they increase the prediction for \mt\ derived from current measurements. The \ms\ and the on-shell calculations of \dr, in a recently proposed formulation, are compared and found to be in excellent agreement over the wide ranges 60\GeV \leq \mh \leq 1 \TeV, \mz \leq \mt \leq 250 \GeV.Comment: 51 pages (needs doublespace, equations, and cite styles