proton density is more than 1014 per (May 19.91, page 6). More complex sq cm. superlattices have been investigated T. Niinikoski looked at polarized by a KEK/Nagoya/NEC group. Light cone approach solid target developments, where the Turning to the future, A.D. Krisch high deuteron polarization in organic looked at what is in store at UNK, One of the most challenging prob­ materials through r.f modulation is Fermilab and the US Superconduct­ lems in theoretical high energy impressive. High polarizations in ing Supercollider. RHIC at physics is to compute the bound- lithium compounds have been Brookhaven will also offer interesting state structure of the proton and achieved at Saclay, LAMP F and PSI polarized proton possibilities. KEK's other hadronslrom quantum (Switzerland), and the possibility of 12 GeV proton machine will cover a chromodynamics (QCD), the field proton polarization at room tempera­ complementary kinematic range. theory of quarks and gluons. ture proposed by the Kyoto/KEK P. Taxil showed how polarized The goal is not only to calculate the group is intriguing. S.Y. Lee ex­ beam physics at future large proton spectrum of hadron masses from first plained polarized beam acceleration colliders will probe beyond the principles, but also to derive the with 'snakes', indicating the possibili­ Standard Model, while D. Burke momentum and spin distributions of ties for major ongoing projects. looked at what electron-positron the quarks and gluons which control Highlights of the parallel workshop colliders will offer. Spin physics will high energy hadron interactions. on polarized electron sources and continue to be a fruitful field. One approach to these difficult electron spin polarimeters were calculations is to simulate QCD on an summarized by T. Nakanishi. From Akira Masaike artificial lattice. Recently, several new Remarkable progress in methods based on "light-cone" photoemission from semiconductors quantization have been proposed as has been seen in recent years. alternatives to lattice theory for Nagoya has obtained 86% polariza­ solving non-perturbative problems in tion with strained gallium arsenide, Tau production and decay in experiments at QCD and other field theories. CERN's LEP electron-positron collider while SLAC/Wisconsin has achieved provides valuable precision information on The basic idea is a generalization of 71% with indium gallium arsenide Standard Model parameters. Heisenberg's pioneer matrix formula­ tion of quantum mechanics: if one could numerically diagonalize the matrix of the Hamiltonian represent­ ing the underlying QCD interaction, then the resulting eigenvalues would give the hadron spectrum, while the corresponding eigenstates would describe each hadron in terms of its quark and gluon degrees of freedom. The new ingredient which appears to make this method tractable is quantization on the light-cone - as if the observer were travelling at the speed of light. For example if a laser is shone along the z-axis of an atom, the scattered photons determine the coordinates of each electron at a fixed value of t-z/c, where c is the speed of light. The equations of quantum electrodynamics then predict the electron coordinates at later values of t-z/c. 14 CERN Courier, March 1993 More valves. answers. Because their engineers know valves. Better design. And how to solve vacuum problems. First-class tech support. Plus, they've got a lot more than valves . Whether you need butterfly or gate valves. Pneumatic or Its all in the free catalog. manual. Bakeable or elastomer- Everything. From positioners to sealed. Right-angle, in-line or straight-through - connectors to full custom chambers. To get Huntington is the place . the catalog, just call: Huntington Laboratories, Broader selection and better designs. Like their unique 1040 L'Avenida, Mountain View, CA 94043. conical seats, for tighter seals. Or their patented butterfly (800) 227-8059 or (415) 964-3323. floating shaft, for perfect flapper centering. Or their solid construction, with less welding for better integrity . Huntington And when you call Huntington, you get intelligent Better-Built Vacuum Components This allows a finite basis of non- provides .a precise definition of model For QCD(1+1), complete numerical interacting quark and gluon states structure in terms of quarks and solutions for the spectrum and light- without violating the essential relativ­ gluons, and a general calculus for cone wavefunctions can be obtained ists invariance of the theory. computing relativistic scattering, form as a function of the coupling strength, The foundations of light-cone quan­ factors, electroweak transitions, and the quark masses, and the number of tization date back to Dirac, who in other hadronic phenomena. flavours and colour. 1949 showed that there are remark­ The problem of computing the Light-cone quantization of QCD in able advantages in quantizing relativ­ hadronic spectrum and the corre­ physical space-time is a highly- ists field theories at fixed "light-cone sponding light-cone wavefunctions of challenging numerical computational time", t-z/c, rather than ordinary time. QCD can thus be reduced to the problem. In the DLCQ method, the In the traditional formulation, han­ diagonalization of a finite matrix size of the quark and gluon basis and dling a moving bound state is as representation of the light-cone the discretization of the transverse complicated as diagonalizing the Hamiltonian. This method, called momenta quickly leads to very large Hamiltonian itself. On the other hand, "discretized light-cone quantization" matrices. In addition, the quantization on the light-cone can be (DLCQ), has now been successfully Hamiltonian must be supplemented formulated without having to choose applied to a number of quantum field by renormalization terms. a specific frame of reference. Thus a theories in one-space and one-time Approximate methods have also light-cone QCD Hamiltonian de­ dimension, including QCD, quantum been developed which use effective scribes bound states of confined electrodynamics, Yukawa models, light-cone Hamiltonians and a trunca­ relativistic quarks and gluons of and the two-dimensional matrix tion of the quark and gluon states arbitrary four-momentum. It also models of superstring theory. t (the "Light-Front Tamm Dancoff method"), or a combination of light- cone quantization with traditional lattice gauge theory in the transverse dimensions. In the case of quantum electrodynamics in 3+1 dimensions, the positronium spectrum has been obtained at large coupling strength (a=0.3) by solving an integral equa­ tion derived from the truncated QED light-cone Hamiltonian. The most subtle problem now confronting light-cone quantization methods is how to understand the spontaneous symmetry breaking normally associated with the struc­ ture of the vacuum. In light-cone quantization the momentum-inde­ pendent "zero modes" of the quan­ tum fields are determined from The positronium mass spectrum (for a=0.3) computed from a truncated quantum electrody­ namics light-cone Hamiltonian (from M. Krautgârtner, H. C. Pauli, and F. Wôlz) showing the convergence of the bound and continuum spectrum of positronium, including the hyperfine splitting, as one increases the number of integration points. This light cone approach promises new insights into complex field theory calculations. 16 CERN Courier, March 1993 MAKE YOUR BUDGET GO FURTHER. ... if you have, until now, postponed purchasing high-quality ultra high vacuum components for financial reasons. 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