James D. Bjorken

ELECTROPRODUCTION OF NUCLEON RESONANCES

Abstract We compute the differential cross section for the process e + p → e + pr where pR is a nucleon resonance characterized by parity πR, spin J, and mass MR. The two inelastic form factors describing this cross section are expressed in terms of three amplitudes characterizing the (p, pR) electromagnetic vertex. The kinematic and analytic structure of these three amplitudes as a function of q2 are discussed. The case of the 33 resonance is discussed in some detail.

Cosmology and the standard model

We consider the properties of an ensemble of universes as function of size, where size is defined in terms of the asymptotic value of the Hubble constant (or, equivalently, the value of the cosmological constant). We assume that standard model parameters depend upon size in a manner that we have previously suggested, and provide additional motivation for that choice. Given these assumptions, it follows that universes with different sizes will have different physical properties, and we estimate, very roughly, that only if a universe has a size within a factor

Search for disoriented chiral condensate at the Fermilab Tevatron

\sqrt{2}

Analysis of charged-particle–photon correlations in hadronic multiparticle production

of our own will it support life as we know it. We discuss implications of this picture for some of the basic problems of cosmology and particle physics, as well as the difficulties this point of view creates.

Regge Behavior of Forward Elastic Scattering Amplitudes

We present results from MiniMax (Fermilab T-864), a small test/experiment at the Fermilab Tevatron designed to search for the production of a disoriented chiral condensate (DCC) in p-p(bar sign) collisions at {radical}(s)=1.8 TeV in the forward direction, {approx}3.4<{eta}<{approx}4.2. Data, consisting of 1.3x10{sup 6} events, are analyzed using the robust observables developed in an earlier paper. The results are consistent with generic, binomial-distribution partition of pions into charged and neutral species. Limits on DCC production in various models are presented. (c) 2000 The American Physical Society.

The Classification of Universes

In order to analyze data on joint charged-particle/photon distributions from an experimental search (T-864, MiniMax) for disoriented chiral condensate (DCC) at the Fermilab Tevatron collider, we have identified robust observables, ratios of normalized bivariate factorial moments, with many desirable properties. These include insensitivity to many efficiency corrections and the details of the modeling of the primary pion production, and sensitivity to the production of DCC, as opposed to the generic, binomial-distribution partition of pions into charged and neutral species. The relevant formalism is developed and tested in Monte-Carlo simulations of the MiniMax experimental conditions.

Standard Model Parameters and the Cosmological Constant

A theorem concerning the asymptotic behavior of forward elastic scattering amplitudes in relativistic theories is stated and proved. The assumptions made are (1) identical spinless particles interact via Gφ3 and λφ4 couplings; (2) a cutoff of the propagators is introduced; (3) the forward scattering amplitude satisfies a Bethe‐Salpeter equation in the crossed channel; (4) the kernel of the equation is an arbitrary finite subset of the Feynman graphs which compose the exact kernel. The theorem states that under these assumptions, the forward scattering amplitude exhibits Regge behavior, i. e., A(s, 0) → sα + O (1) as s → ∞.

Rapidity-gap events in e+e− annihilation

We define a universe as the contents of a spacetime box with comoving walls, large enough to contain measurable phenomena, but not much larger. This allows the construction of a local ensemble of such universes, given modest extrapolations of the observed properties of the cosmos. We then assume that further out similar universes can be constructed, but with different standard model parameters, strongly correlated with the size in a definite way, where by size is meant the Hubble scale at late times. This allows an estimate of the range of sizes supporting life as we know it. The result allows some understanding of the hierarchy problems of particle physics. Other possible implications of the assumptions made will be discussed, including a possible connection between the QCD vacuum structure and cosmological horizon structure. In all cases, our approach is as bottoms-up and as phenomenological as possible, suggesting that theories of the multiverse may eventually lay some claim of being scientific.

Intersections 2000: What’s new in hadron physics

Simple functional relations among standard model couplings, including gravitational, are conjectured. Possible implications for cosmology and future theory are discussed.

FELIX: A Full acceptance detector at the LHC: Letter of intent

Abstract We discuss the significance of events containing rapidity-gaps in high-energy scattering processes, in particular in e+e− annihilation and/or W, Z decays. We compute explicitly the fraction of events containing rapidity-gaps in e+e− →q q q q and e+e− →q q gg processes at low jet-pair invariant mass limit. These events follow a distinctive sin2θ distribution in the jet-pair scattering angle. Similar processes are candidate backgrounds for important Higgs and W+W− scattering physics at the SSC and LHC.