Summary Talk: Particle Physics Phenomenology

289 Brazilian Journal of Physics, vol. 31, no. 2, June, 2001 Summary Talk: Particle Physics Phenomenology Erasmo Ferreira Instituto de Fisica, U.F.R.J., Rio de Janeiro, RJ, 21945-970, Brasil E-mail: Received on 25 February, 2001 We summarize the contributed papers and the talks in the plenary and parallel sessions in this XXI Brazilian National Meeting on Particles and Fields that are classi ed as of phenomenology kind. We try to put the activities here developed in the perspective of the existing community of phenomenologists in Brazil 2000. We recall that the phenomenology of the interaction of elementary particles was probably our main area of reasearch in the time when physics research in Brazil began, in the 1940, 1950 decades. It is interesting to remark that at those times there was fair amount of experimental activity in particle physics in Brazil (cosmic rays, nuclear emulsions), and there was also the remarkable work of Cesar Lattes in Bristol and in the Chicago accelerator. Since then, for some decades, there was less experimental particle physics than there should be, and correspondingly theoretical phenomenology developed slowly in the country. It was not at all easy to work in phenomenology in a place like Brazil before the internet came to solve the information/communication problem. Experimental data and theoretical ideas could usually take several months to reach physicists here. Some decades ago the elementary particles were the mesons, nucleons, eletrons, photons ..., and the study of their interactions were the concern of elementary particle physics. QED succeeded beautifully, and the structure of the weak interactions was understood, while the strong interactions remained for several decades as an unsolved problem, in spite of the brilliant description of the hadron spectroscopy through SU(3). Then the energies went up, and the investigations of the eletroweak properties of heavy quarks and leptons and of intermediate vector bosons took the center of the stage and became the de nition of elementary particle physics research, the standard model being investigated thoroughly. The Higgs boson, its only undiscovered building block, seems to be around the corner, according to experiments described in this meeting. Brazilian physicists have been working actively in both experimental and theoretical aspects of these investigations, as exhibited in the present meeting. The strong interactions, with the diÆculties caused by the con nement and the non-perturbative aspects of QCD, poses big problems in calculations of hadron production and hadronic interactions. Methods and concepts must be developed to face these questions. The fundamental properties of QCD (vacuum structure, mechanisms of con nement, behaviour of matter at high densities and high temperatures) are still mysterious. The speci city of the problems creates the area called hadron physics (the study of hadronic structures and interactions). The biggest electron machine LEP is now closed, its place being taken over by LHC, that together with Fermilab Tevatron and RHIC at BNL will form a group of hadronic machines where the studies of the fundamental interactions and the search for fundamental constituents will be made. Besides them, there will be the e+ e colliders dedicated mainly to b-physics. It is remarkable that Hadron Physics is well organized in Brazil, with a strong and active community that holds regular meetings of both national and international scope. Only a small part of this community participate regularly in ENFPC. With the changes in the frontiers of particle physics research described above, it is important that more communication and more merging develops between the areas. The amount of particle physics research presented in the hadronic meetings could enrich substantially the programs of ENFPC, and e ort must be made in this direction. On the other hand, the interface between particle and nuclear physics, in large part provided by hadronic physics, must be incentivated in Brazil. Modern Nuclear Physics must be QCD based, which requires rather profound changes in the research that is traditionally made in our laboratories in Brazil. The interface between particle and nuclear physics, provided by 290 Erasmo Ferreira hadronic physics must be developed to impulsionate these changes. The Plenary Sessions PL1 - Maria Beatriz Gay Ducati, UFRGS, Brazil : High Density QCD. PL2 - Jonathan L. Rosner, University of Chicago, USA : CP Violation: Past, Present and Future. The Parallel Sessions PA1 - Gast~ao Krein, IFT/Unesp, Brazil : The Gerasimov-Drell-Hearn Sum Rule and the Spin Structure of the Proton. PA2 - Marcelo M. Guzzo, UNICAMP, Brazil : New Paradigms in Neutrino Physics. I nd that the organizing committee was wise and lucky in choosing these topics for the plenary and parallel sessions in phenomenology. M.B. Gay Ducati described the work of hers and her students on the diÆcult dynamics of QCD in the con nement regime. Including unitarity and screening corrections in the evolution equations, they obtain new equations, which are then solved with approximations, to obtain observable quantities of the proton structure. The screening corrections will be particularly important in the analysis of the heavy ion and hadronic collisions that will be observed in future accelerators. J.L. Rosner presented a beautiful and competent review of the studies of CP violation that date since the rst discovery of neutral K0 mesons decaying in wrong CP states. The violation of CP symmetry, which is related to the behaviour of systems under time reversal, is now under intense scrutiny by experimentalists and theorists, who try to understand all aspects of the systems and dynamics involved. The studies will clarify the parameters of the standard model and the dynamics of the electroweak interaction. The B mesons produced in Fermilab and in the b factories in Cornell, SLAC and KEK and the complex experiments to study K decays in CERN and Fermilab are giving extensive and accurate information for this fundamental area of particle physics. In spite of the frightening title (how many people knew about the GDH sum rule, with all its simplicity and exactness?) the talk by Gast~ao Krein was pedagogically very clear and stimulating. Interesting to hear how the low energy photon experiments can test the proton structure, complementing the studies with deep inelastic scattering made in the high energy machines. It was nice to hear about the Ragusa polarizabilities (Silvestre Ragusa, our colleague from S~ao Carlos), which were introduced many years ago and are a useful tool in these studies. Neutrino physics has been a very hot subject in the recent years, with several problems and intriguing questions, and a dramatic e ect in our knowledge of the fundamental particles, due to the discovery of the non-zero neutrino masses and the neutrino oscillations. The discoveries are important also for cosmolog (...truncated)