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This document presents the current status of the Silicon Detector (SiD) effort to develop an optimized design for an experiment at the International Linear Collider. It presents detailed discussions of each of SiD's various subsystems, an overview of the full GEANT4 description of SiD, the status of newly developed tracking and calorimeter reconstruction algorithms, studies of subsystem performance based on these tools, results of physics benchmarking analyses, an estimate of the cost of the detector, and an assessment of the detector R and D needed to provide the technical basis for an optimised SiD.

In the standard Higgs model of electroweak symmetry breaking, the Higgs boson is associated with both vector-boson and fermion mass generation. In contrast, we discuss a two-Higgs-doublet model in which these masses are associated with two different scalar bosons. We show that the Higgs boson associated with vector-boson mass generation produces a {\it dip\/} in the cross section for $t\bar t\to ZZ$ via a final-state interaction. Such a dip will be difficult to observe at the LHC/SSC., 15 pages, FERMILAB--PUB--92/27--T

We study the transverse momentum distribution for a $pair$ of heavy quarks produced in hadron-hadron interactions. Predictions for the large transverse momentum region are based on exact order $\alpha_s^3$ QCD perturbation theory. For the small transverse momentum region, we use techniques for all orders resummation of leading logarithmic contributions associated with initial state soft gluon radiation. The combination provides the transverse momentum distribution of heavy quark pairs for all transverse momenta. Explicit results are presented for $b\bar b$ pair production at the Fermilab Tevatron collider and for $c\bar c$ pair production at fixed target energies., Comment: LaTeX (27 pages text, 8 figures not included, but available on request)

Calculations are presented of the longitudinal structure function $F_L(x, Q^2)$. We use next-to-leading order expressions in QCD $({\cal{O}}(\alpha_s^2))$ plus parton densities determined previously from global fits to data on deep inelastic lepton scattering, prompt photon production, and bottom quark production. Anticipated data from the DESY ep collider HERA should provide discriminating information on the gluon density, particularly for values of $x < 0.05$., Comment: 7 pages, LaTeX, 2 figs available upon request, ANL-HEP-PR-93-7 & CERN-TH 6785/93

A review is presented of data and theoretical interpretations of the nuclear dependence of quark and antiquark distributions as observed in the deep inelastic scattering of neutrinos and charged leptons from nuclei. After a summary of the experimental situation and a survey of proposed explanations, I concentrate on interpretations in terms of conventional nuclear physics and on the Q2-rescaling approach. The review concludes with a list of desirable future experiments.

To check predictions of the Deck model, dσ/dt′ distributions are compared for the reactions π+p→π+(π−Δ++) and π−p→π−(π−Δ++) at 16 GeV/c, for M(π−Δ++) ⩽ 1.9 GeV. No cross-over in dσ/dt′ is observed for the total sample of events. When the data are divided into two subsets, according to whether the absolute value of the azimuthal angle φS of the Δ++ in the s-channel helicity system is greater than or less than 12π, then cross-over effects are observed for each subset. For |φS|>12π the “normal” result is obtained that slope b− of the dσ/dt′ distribution for negative beam particles is greater than that for positive beam particles, i. e. b− > b+. For |φS| b− is obtained, a situation observed here for the first time in high-energy reactions. These results are consistent with predictions of the Deck model.

We analyze the decays of heavy meson resonances into baryon-antibaryon final states within the formalism of exclusive processes in QCD. The decay of JPC = 2++ states into proton-antiproton pairs is examined in detail. Predictions are presented for the branching ratios with the proton wave function normalized by data for ψ → pp. Predictions for the cross section of charmed resonance production in pp collisions are given. We discuss the feasibility of studying bb spectroscopy in pp collisions as well as the reliability of our predictions.

Simple scaling arguments based on ISR results suggest that the cross section for the associated production of heavy quark mesons at the SPS pp collider may be quite sizeable. We consider thsemi-leptonic decay of such a heavy meson, and emphasize a technique for determining the mass and longitudinal momentum distribution. The important features are illustrate using a simple theoretical model.

Massive lepton pair production in hadronic collisions, A + B → μ+ μ− X, is usually assumed to proceed via ann intermediate virtual photon, ψ∗ → μ+ μ−, the Drell-Yan process. We examine other contributions arising from heavy flavour production, A + B → QQX; Q → μνX. We find that this background is comporable to the Drell-Yan signal at small values of Mμμ2/s but negligible at large values. Characteristic siggnatures are described that distinguish the background from the signal.

Charged particle multiplicity cross sections for 100 GeV/ c π − p inelastic interactions are presented and compared with results at other energies. The results for multiplicities n ⪖ 4 show a consistent trend in their energy dependence. The two-prong cross section curve differs as it tends to flatten off at the higher energies. The zero-prong cross section values decrease steeply as p lab −1.1 . The results for n ⩾ 2 for π − p and pp reactions appear to lie on a “universal” curve if nσ n / σ inel is plotted against 〈 n 〉/ n . This “scaling” rule is equivalent to KNO scaling, but the plot suggested here is more useful in studying low multiplicities. An interpretation in terms of a two-component model and a possible extrapolation to higher energies are proposed.

Quantum chromodynamic (QCD) predictions are made for the large transverse momentum production of single and double photons in proton-proton, proton-antiproton, and pion-proton collisions. In π−p collisions at center-of-mass energy W = 27.4 GeV and pT = 4.0 GeV, it is estimated that about 0.3% of the 90° single photon triggers will be balanced on the “away-side” by a single photon with roughly the same transverse momentum. In π+p collisions this fraction drops to about 0.09%. These fractions increase with pT. In addition to the pure QED annihilation term q q →γγ , it is found that the QCD-induced subprocess gg→γγ provides an important source of double photons. Photon bremsstrahlung contributions are also examined. Experimental study of the systematics of single and double photon production in hadron-hadron collisions will provide information on the size of the strong interaction coupling constant, αs(Q), and on the charges of the quarks. Knowledge of the gluon distributions within hadrons and of the effective transverse momentum of partons in hadrons can also be gained.

We study the multiplicity distributions and the correlations of charged particles produced forward and backward in the centre-of-mass system. The correlations are small but significant. This type of analysis shows clearly the presence of the diffractive component of the inelastic cross section, amounting to about 15% of it. It is also apparent that KNO multiplicity scaling is not satisfied.

Rapidity correlations in the central region among hadrons produced in proton-proton collisions of fixed final state multiplicity n at NAL and ISR energies are investigated in a two-step framework in which clusters of hadrons are emitted essentially independently, via a multiperipheral-like model, and decay isotropically. For n>or approximately=/sup 1///sub 2/(n), these semi-inclusive distributions are controlled by the reaction mechanism which dominates production in the central region. Thus, data offer cleaner insight into the properties of this mechanism than can be obtained from fully inclusive spectra. A method of experimental analysis is suggested to facilitate the extraction of new dynamical information. It is shown that the n independence of the magnitude of semi-inclusive correlation functions reflects directly the structure of the internal cluster multiplicity distribution. This conclusion is independent of certain assumptions concerning the form of the single cluster density in rapidity space. (23 refs).

No abstract available

The discussion of hadron physics includes a few interesting unanswered questions concerning correlations in general, and then a new method is described for extracting dynamical information from the invariant mass dependence of inclusive correlation functions. (JFP)

The discussion of a program of hadronic physics investigations includes some of the open questions which may be resolved through studies with the Doubler in its collision mode, and then with external beams. Low momentum-transfer conventional hadron physics is emphasized. Elastic and inelastic scattering, total and differential cross sections, inclusive processes, pomeron exchange and spin flip are covered. (JFP)

The discussion of the status of the Z$sub 1$* covers the substantial improvement in the differential cross section data for K$sup +$p elastic scattering and an improved energy dependent analysis based on the K-matrix formalism, which in order to fit the data, requires a P/sub $sup 3$/$sub 2$/- resonance pole. (JFP)

Recently reported data on monojet events and on massive eν-jet and jet-jet systems at the CERN SPS pp collider suggest a common origin which could be the production of new hadronic states with mass in the neighbourhood of 160 GeV. We explore the consequences of postulating that such states exist and are excited in qq or gg subprocesses. To be specific, we identify the states as coloured mesonic systems and we then compute production cross sections and branching fractions into qq, gg, gZ 0 , gW, and gγ, obtaining fair consistency with data. Implications and predictions are discussed.

We use the formalism of exclusive processes at high momentum transfer, to give predictions for the decay of the 2++ chi state into a pp pair and the production cross section for chi in pp collisions.

From an approach to multiparticle production in which clusters of hadrons are emitted, the formalism is developed for an analysis of rapidity correlations in the central region at fixed multiplicity. Predictions are given for multiplicity, energy, and rapidity dependence of correlation functions.

A unitary Deck model with coupled K*..pi.. and Krho channels, including only one resonance in the Q region is constructed. Adjusting the resonance parameters, one achieves a satisfactory description of the experimental phase variations and structure in the mass spectra. The resonance is determined to belong to the J/sup PC/ = 1/sup + -/ SU(3) octet, and is thus the Q/sub B/. The relative coupling strength K*..pi../Krho is approximately 2/3.

Quantitative predictions are presented for a specific hard-scattering reaction ..pi..N ..-->.. ..gamma..X in which both the incident meson and the produced prompt photon couple directly in the QCD amplitude. The process leads to a highly constrained class of events at large p/sub T/ in which the photon momentum is balanced by that of a recoil quark jet, with no spectator jet of final-state particles emerging along the beam axis. Normalized absolutely in terms of the electromagnetic form factor of the pion, F/sub ..pi../(Q/sup 2/), the cross section provides a lower bound on the total p/sub T//sup -6/ high twist contribution to the inclusive prompt-photon yield.

From a simple fragmentation approach to inelastic production at large fixed angles, the authors obtain an inclusive cross-section which falls as an inverse power of large transverse momentum p/sub T/ and which scales according to (p/sub T// square root s), both consistent with ISR data. Predictions for charge ratios and associated multiplicities are also presented and compared with available data. (12 refs).

A simple two-parameter model incorporating pion clusters produced with a multiperipheral-like matrix element is proposed. It gives a good qualitative description of multiplicity, and of single- and two- particle rapidity distributions above 50 GeV/c. (20 refs).

A dispersion parameter for individual events is defined and advocated as a quantitative measure of clustering of particles along the longitudinal rapidity axis in high energy multiparticle interactions. General arguments and Monte Carlo simulations indicate that the parameter should discriminate between fragmentation-type and multiperipheral-type models at p/sub lab/>or approximately=100 GeV/c. (14 refs).