CLIC e+e- Linear Collider Studies

This document provides input from the CLIC e+e- linear collider studies to the update process of the European Strategy for Particle Physics. It is submitted on behalf of the CLIC/CTF3 collaboration and the CLIC physics and detector study. It describes the exploration of fundamental questions in particle physics at the energy frontier with a future TeV-scale e+e- linear collider based on the Compact Linear Collider (CLIC) two-beam acceleration technique. A high-luminosity high-energy e+e- collider allows for the exploration of Standard Model physics, such as precise measurements of the Higgs, top and gauge sectors, as well as for a multitude of searches for New Physics, either through direct discovery or indirectly, via high-precision observables. Given the current state of knowledge, following the observation of a \sim125 GeV Higgs-like particle at the LHC, and pending further LHC results at 8 TeV and 14 TeV, a linear e+e- collider built and operated in centre-of-mass energy stages from a few-hundred GeV up to a few TeV will be an ideal physics exploration tool, complementing the LHC. Two example scenarios are presented for a CLIC accelerator built in three main stages of 500 GeV, 1.4 (1.5) TeV, and 3 TeV, together with the layout and performance of the experiments and accompanied by cost estimates. The resulting CLIC physics potential and measurement precisions are illustrated through detector simulations under realistic beam conditions.Comment: Submitted to the European Strategy Preparatory Grou

CTEQ Parton Distributions and Flavor Dependence of Sea Quarks

This paper describes salient features of new sets of parton distributions obtained by the CTEQ Collaboration based on a comprehensive QCD global analysis of all available data. The accuracy of the new data on deep inelastic scattering structure functions obtained by the very high statistics NMC and CCFR experiments provides unprecedented sensitivity to the flavor dependence of the sea-quark distributions. In addition to much better determination of the small x dependence of all parton distributions, we found: (i) the strange quark distribution is much softer than the non-strange sea quarks and rises above the latter at small-x; and (ii) the difference $\bar d-\bar u$ changes sign as a function of x. A few alternative sets of viable distributions with conventional assumptions are also discussed.Comment: 13 pages with figures, MSUHEP-92-27, Fermilab-Pub-92/371, FSU-HEP-92-1225, ISU-NP-92-1

Measuring Parton Densities in the Pomeron

We present a program to measure the parton densities in the pomeron using diffractive deep inelastic scattering and diffractive photoproduction, and to test the resulting parton densities by applying them to other processes such as the diffractive production of jets in hadron-hadron collisions. Since QCD factorization has been predicted NOT to apply to hard diffractive scattering, this program of fitting and using parton densities might be expected to fail. Its success or failure will provide useful information on the space-time structure of the pomeron.Comment: Contains revisions based on Phys. Rev. D referee comments. RevTeX version 3, epsf, 31 pages. Uuencoded compressed postscript figures appended. Uncompressed postscript files available at ftp://ftp.phys.psu.edu/pub/preprint/psuth136