1. Introduction This paper has three parts. The first part is a simplified presentation of the basic ideas of the renormalization group and the ε expansion applied to critical phenomena , following roughly a summary exposition given in 1972 1. The second part is an account of the history (as I remember it) of work leading up to the papers in I971-1972 on the renormalization group. Finally, some of the developments since 197 1 will be summarized, and an assessment for the future given.

The renormalization group and critical phenomena

The Bonn Meson Exchange Model for the Nucleon Nucleon Interaction

http://cds.cern.ch/record/183730/files/198801416.pdf

A measurement of the spin asymmetry and determination of the structure function g1 in deep inelastic muon-proton scattering

New coupled equations describing collisions of an atom and a diatomic molecule are derived in this paper. By utilizing a description of the collision in terms of rotating coordinates, all coupling in the z component of angular momentum is isolated into purely kinematic effects. By neglecting these couplings, one is led to approximate equations for which the jz component of angular momentum for the molecule is conserved. In addition, the scattering cross sections are formulated by neglecting the effect on the wavefunction of the rotation of the coordinate axes so that in place of Wigner rotation matrices dmmJ (Θ) appearing, one deals with simple Legendre polynomials and the orbital angular momentum l2 is approximated by l(l + 1) ℏ2. It is noted that the procedure involves no approximations so far as the potential matrix elements are concerned. Furthermore, the number of equations remaining coupled is drastically reduced and a completely quantum mechanical description of the dynamics of both internal states and relative motion is retained. The physical implications of the approximations are examined, and it is seen that the neglect of intermultiplet coupling gives rise to consideration of only transitions where both the orientation and magnitude of the rotor angular momentum change. Further, the neglect of transformation effects on the wavefunction is expected to be least accurate for the inelastic forward scattering and best for backward scattering and the j =0→0 elastic scattering. Finally, the present simplest version of the approximation obviously is not intended for treating processes dependent on mj transitions, e.g., NMR relaxation in He–H2. Next the formalism is applied in test calculations to He–H2 collisions using the Krauss‐Mies potential energy surface. Numerical results for elastic and inelastic integral and differential cross sections are compared with exact quantum mechanical close coupling solutions of the standard coupled channel equations. Over the energy range studied (from 0.1 eV up to 0.9 eV), agreement to within a few percent is obtained. Additional coupled states calculations are reported at 1.2 eV and computation times are compared against those required for a full close coupling solution. Calculations for the Roberts He–H2 surface are also reported to illustrate the independence of the approximations on the strength of the coupling (so long as the inelastic scattering is predominantly in the backward direction). The dramatic savings afforded by the present approach are such as to make possible fully converged calculations at collision energies typically studied in molecular beam experiments. Thus, for elastic and inelastic nonreactive collisions, involving a repulsive‐type interaction, the approach makes the a priori quantum mechanical description of the scattering of a diatom by an atom practical.

Quantum mechanical close coupling approach to molecular collisions. jz ‐conserving coupled states approximation

https://cds.cern.ch/record/147786/files/198311273.pdf

A QCD model for jet fragmentation including soft gluon interference

On the general theory of collisions for particles with spin

The year 1994 marked the beginning of the CERN lead beam programme. A beam of 33 TeV (or 160 GeV per nucleon) lead ions from the SPS now extends the CERN relativistic heavy ion programme, started in the mid eighties, to the heaviest naturally occurring nuclei. A run with lead beam of 40 GeV per nucleon in fall of 1999 complemented the program towards lower energies. Seven large experiments participate in the lead beam program, measuring many different aspects of lead-lead and lead-gold collision events: NA44, NA45/CERES, NA49, NA50, NA52/NEWMASS, WA97/NA57, and WA98. Some of these experiments use multipurpose detectors to measure simultaneously and correlate several of the more abundant observables. Others are dedicated experiments to detect rare signatures with high statistics. This coordinated effort using several complementing experiments has proven very successful. The present document summarizes the most important results from this program at the dawn of the RHIC era: soon the relativistic heavy ion collider at BNL will allow to study gold-gold collisions at 10 times higher collision energies. Physicists have long thought that a new state of matter could be reached if the short range repulsive forces between nucleons could be overcome and if squeezed nucleons would merge into one another. Present theoretical ideas provide a more precise picture for this new state of matter: it should be a quark-gluon plasma (QGP), in which quarks and gluons, the fundamental constituents of matter, are no longer confined within the dimensions of the nucleon, but free to move around over a volume in which a high enough temperature and/or density prevails. This plasma also exhibits the so-called “chiral symmetry” which in normal nuclear matter is spontaneously broken, resulting in effective quark masses which are much larger than the actual masses. For the transition temperature to this new state, lattice QCD calculations give values between 140 and 180 MeV, corresponding to an energy density in the neighborhood of 1 GeV/fm 3 , or seven times that of nuclear matter. Temperatures and energy densities above these values existed in the early universe during the first few microseconds after the Big Bang.

Evidence for a New State of Matter: An Assessment of the Results from the CERN Lead Beam Programme

Physics at the CERN-ISR

http://cds.cern.ch/record/138264/files/CM-P00061332.pdf

Maurice Jacob

Papers

On the general theory of collisions for particles with spin

Evidence for a New State of Matter: An Assessment of the Results from the CERN Lead Beam Programme

Physics at the CERN-ISR

Quark matter formation and heavy ion collisions A general review and status report

Spin physics at short distances