New Fields and Strings in Subnuclear Physics

PREFACE.

CONTENTS.

In the Standard Model, quarks and gluons are permanently confined by the strong interaction into hadronic bound states. The values of the quark masses and the strengths of the decays of one quark flavour into another cannot be measured directly, but must be deduced from experiments on hadrons. This requires calculations of the strong-interaction effects within the bound states, which are only possible using numerical simulations of lattice QCD. These are computationally intensive and, for the past twenty years, have exploited leading-edge computing technology. In conjunction with experimental data from B Factories, over the next few years, lattice QCD may provide clues to physics beyond the Standard Model. These lectures provide a non-technical introduction to lattice QCD, some of the recent results, QCD computers, and the future prospects.

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The s and t-channel approaches to the high energy hadron scattering are reviewed. The parton model is applied to describe the high energy and deep-inelastic processes. In QCD the parton picture leads to the DGLAP evolution equations for the parton distributions. The gluon and quark are shown to lie on their Regge trajectories. The integrability properties of the effective theory for the high energy QCD in the multi-colour limit are outlined. The Baxter - Sklyanin representation for the wave function of the composite colourless states is formulated. Next-to-leading corrections to the BFKL equation in QCD and supersymmetric gauge theories are discussed. The effective action for the gluon and quark integrations local in the parton rapidities is presented.

In early years the cosmic ray studies were ahead of the accelerator research, starting from the discovery of positrons, through muons, to that of pions and strange particles. Today we are facing the situation that the puzzling saga of cosmic rays of the highest energies may again unfold in the discovery of new physics, now beyond the Standard Model; or it may bring to life an "extreme" astrophysics. After a short review of the Greisen-Zatsepin-Kuzmin puzzle, I discuss different models which were suggested for its resolution. Are there any hints pointing to the correct model? I argue that the small-scale clustering of arrival directions of cosmic rays gives a clue, and BL Lacs are probable sources of the observed events.

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An overview on new developments in experimental particle and astroparticle physics is presented. This includes observation of CP violation in the B-sector, detection of direct CP violation in the K⁰-system, new measurements on solar neutrinos, cosmic microwave background radiation and properties of the universe, electroweak results from the large colliders and tests of the Standard Model, measurement of the anomalous magnetic moment of muons, structure of the proton at large energy transfers and virtualities, and heavy ion collisions at very high energies. Finally, the physics reach of TEVATRONII, LHC and TESLA, a linear e⁺e^- collider proposed for the 0.5 - 1 TeV regime, is briefly reviewed.

The Gran Sasso National Laboratory of the INFN has given important contributions to the discovery of the phenomenon of neutrino oscillations with experiments both on electron neutrinos from the Sun and muon neutrinos indirectly produced by cosmic rays interactions in the atmosphere. Other experiments in the laboratory give the best limits on electron neutrino effective Majorana mass with two different isotopes. We appear to have entered a new physics domain in which the study of neutrinos may lead us to discover new phenomena, corresponding to energy scales by much higher than those of the present accelerators. Underground laboratories are showing their relevance complementary to the colliders for the advance of basic physics.

The physics program at the Gran Sasso Laboratory that we are defining will be focussed on neutrino physics with a complementary set of experiments on the muon neutrino beam from CERN (CNGS project), on solar neutrinos, on atmospheric neutrinos and on neutrinos from Supernova explosion. The relevant thermonuclear cross-sections will be measured. The Majorana vs. Dirac nature of electron neutrinos will be explored with the search for neutrino-less double beta decays in different isotopes.

A precise measurement of the anomalous g value, a = (g - 2)/2, for the positive muon has been made at the Brookhaven Alternating Gradient Synchrotron. The result a_μ⁺ = 11 659 202(14)(6) × 10^-10 (1.3 ppm) is in good agreement with previous measurements and has an error one third that of the combined previous data. The measurement tests standard theory and has the potential to discover new physics. The analysis of data collected in 2000 and 2001 is well underway and, when combined with data from a requested and final run in the fall of 2002 and winter of 2003, are expected to reduce the experimental uncertainty on a_μ to 0.4 ppm.

Recent results from Super-Kamiokande are presented. Solar and atmospheric neutrinos have been studied in detail since 1996. The data of atmospheric neutrinos show strong up-down asymmetry and provide evidence for oscillation along their way through Earth. The selected data support oscillations of ν_μ → ν_τ and rule out the two-flavor ν_μ → ν_s oscillation. The underlying parameters for the ν_μ → ν_τ oscillations are determined to be and sin² 2θ > 0.89ata90 %C.L. Proton decays into various final states have been searched for but no evidence was found. Lower limits on the partial lifetimes are presented for major decay modes, especially those for p → e⁺ π⁰ and are 5.0 × 10³³ yr and 1.9 × 10³³ yr, respectively.

We have developed a procedure to study the helicity of the W boson in events. Using events generated with the PYTHIA program at a top mass M_t = 175 GeV/c², we employ a maximum likelihood method to extract the fraction of right-handed, longitudinal and left-handed W bosons in top decays. Assuming V–A coupling in the decay, we obtain a longitudinal fraction of 0.696±0.097 for 50 simulated experiments of 100 events in lepton+jets final states, a result that is consistent with the input fraction of 0.703.

We describe a nonstandard proposal for baryogenesis in models with a low fundamental scale. The scenario has Standard Model field content and enhanced baryon number violating operators deriving from time-dependent fermion localization in an extra dimension. The CKM matrix provides sufficient CP violation. The major constraints are the low reheating temperature and rate of perturbative B-violating reactions compared to the total entropy created. A sufficient baryon fraction may arise, but the cosmological evolution required is likely to be somewhat contrived. Based on work in collaboration with D. J. H. Chung.

In this talk we discuss the scenario of multigravity according to which the gravity we observe in intermediate scales (1mm< r < 10²⁶cm) is mediated by both a massless graviton and one or more of ultralight spin-2 states. We present how this can be realized in a five dimensional brane-world theory with flat branes and the complications associated with the extra polarizations of the massive gravitons (van Dam-Veltman-Zakharov discontinuity) and the ghost radions corresponding to the fluctuations of the negative tension branes present in these models. We then show how we can construct models of AdS₄ branes instead with exclusively positive tension and demonstrate how the van Dam-Veltman-Zakharov no-go theorem can be circumvented in curved space. These models, although they are consistent, face phenomenological problems related to the presence of a remnant negative cosmological constant on the branes. We finally present how we can obtain the same constructions in six dimensions with flat positive tensions branes only, in a manner that they are both theoretically consistent and phenomenologically acceptable. The latter come in two copies each and offer the first problem-free realization of the multigravity scenario.

An estimate of the energy of neutrino-induced muons in MACRO is provided by a multiple Coulomb scattering measurement. The MACRO original upward-muon data sample has been subdivided according to the reconstructed muon energy. Data in each subset are then compared with expected fluxes from atmospheric neutrinos. The results are interpreted in terms of neutrino oscillations.

We review the non-linear behavior of compactifications with localized brane matter discussed in [1]. The example chosen to test is Randall-Sundrum gravity, with one brane, having no moduli problem and reproducing astrophysical gravity in the long wavelength linear regime. The full 5-dimensional Einstein equations are solved numerically for static spherically symmetric matter localized on the brane, yielding regular geometries in the bulk with axial symmetry. The algorithm performs best for small stars (radius less than the AdS length) yielding highly non-linear solutions, photons emitted from the stellar core having redshifts up to . An upper mass limit is observed in these small stars. We are able to show that the intrinsic geometry of large stars, with radius several times the AdS length, is described by 4-dimensional General Relativity past the perturbative regime and up to the largest mass stars studied with core photon redshifts of .

The vitality of Subnuclear Physics is proved by the existence of its challenges, which are presented and discussed with reference to their implementation in the near future.

SCHOLARSHIPS.

PRIZES.

PARTICIPANTS.