Color models of hadrons

The evidence for a three-valued “color” degree of freedom in hadron physics is reviewed. The structure of color model is discussed. Consequences of color models for elementary particle physics are discussed, including saturation properties of hadronic states, π^o → 2ψ and related decays, leptoproduction, and lepton pair annihilation. Signatures are given which distinguish theories with isolated colored particles from those in which color is permanently bound.     

Symmetry breaking and asymptotic freedom in colour SU(3) gauge models

A class of quark models based on the colour gauge group SU(3) is shown to be asymptotically free despite the conplete breakdown of local symmetry to guarantee infrared stability. The symmetry breakdown is achieved by the presence of elementary scalar fields either through the Higgs mechanism or dynamically as first proposed by Coleman and Weinberg. Asymptotic freedom is preserved by imposing eigenvalue conditions on the coupling constants as first proposed by Chang. New quark species must be present, but below their production threshold, colour can still be a global symmetry which is approximate under SU(3), but exact under SU(2). Among the many implications of this class of models is the possibility of producing isolated quarks and gluons of non-zero mass without altering the short-distance behaviour of the superstrong interaction which binds them.     

Selection rules in a unified gauge model of leptons and hadrons

Decay modes and lifetimes of quarks, vector mesons and protons are determined for the unified model of leptons and hadrons recently proposed by Pati and Salam. It is found that while both the quarks and gauge mesons decay too rapidly to be observed, protons will be comfortably stable against decay into leptons, consistent with earlier estimates and existing experimental evidence. It is of special interest that while quarks may not be directly observable, their presence may be verified owing to the uniqueness of their preferred decay into quite a large number of pions. We also discuss an anomalous lepton-hadron scattering process whose occurrence would imply the presence of exotic SU(4) gluons carrying both baryon and lepton number.     

Asymptotic freedom in gauge theories and quantum gravity

Restrictions on the structure of a gauge theory which follow from the requirement of asymptotic freedom with respect to all coupling constants are studied. One-loop counterterms for renormalizable gravity with matter are computed. It is shown that for the group O(N), taking into account the contribution of quantum R²-gravity allows one to construct new, asymptotically free gauge theories with a reduced number of spinor multiplets. The results are compared with those obtained earlier for conformal gravity with matter.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 36–41, January, 1990.The authors thank A. O. Barvinskii, I. L. Bukhbinder, and E. S. Fradkin for the discussions.     

Double duality and hidden gauge freedom in the poincaré gauge theory of gravitation

We investigate the double duality ansatz of the Poincaré gauge theory of gravitation. It is shown that many known exact solutions belong, as special cases, to larger families of solutions. These families of solutions include several arbitrary functions and can be generated by a transformation which is a Lorentzian rotation of the connection with fixed tetrad. Several new spherically symmetric and wavelike exact solution are presented.     

Relative yield of heavy hadrons as a function of the transverse momentum in LHC experiments

Physics of Atomic Nuclei - The relative yield of hadrons involving a b quark (B c , B s , B, Ʌ b , etc.) is studied as a function of the transverse momentum. It is shown that the yields in...     

Introduction to Nambu Jona-Lasinio models of hadrons

These are introductory lectures to the Nambu Jona-Lasinio model with scalar interactions. It is applied to quark models of mesons and baryons. A critical survey is made of regularization methods. The collective rotation of solitons is briefly summarized.Lecture given at the 8th Summer School on Intermediate Energy Physics: Hadron Dynamics at Low and Intermediate Energies, Prague, July 10–14, 1995.     

Extended-natural gauge models and complementarity

We propose a new condition “extended naturalness” which should be satisfied by any physically sensible gauge theory. In order that a theory is extended-natural, all discrete quantities observed in low energies must be stable against variations of discrete parameters of the theory defined in large mass scales. We find that SU(N) gauge models become extended-natural when we choose appropriate fermion representations. Further, if N is a multiple of 8, the models turn out to be good examples of complementary gauge theories.     

A possibility of asymptotic freedom without non-Abelian gauge theories

We discuss solutions of the renormalization group equations for a Yukawa field theory. For an increasing effective boson mass we find that the leading terms in the vertex functions in the high-energy region are given by diagrams which contain no internal boson lines. In e⁺e^? annihilation into hadrons we get the parton model formula R(s) = Σ_iQ_i², whereas in the deep inelastic e^?p scattering the simple parton model behaviour is modified by the (in general) non-canonical dimension of the quark field.     

Infrared instability of the vacuum state of gauge theories and asymptotic freedom

The radiative corrections to the Yang-Mills massless theory are found to lead to an instability of the vacuum state. This fact is in full compliance with the asymptotic freedom of gauge theories and is due to infrared singularities.     

Reduced models and noncommutative gauge theories

A brief review of the relation between reduced models and noncommutative Yang-Mills (NCYM) theory is given. The twisted Eguchi-Kawai model, the mapping onto NCYM, the Morita equivalence, the fundamental matter, the Wilson loops in NCYM, and the D-brane interpretation are considered.     

Finite formation time of hadrons: the QGP signatures

In order to investigate the possible emergence of guark-gluon plasma, it is necessary to understand the properties of multiparticle production mechanisms in a more simple case than in relativistic collisions of heavy ions. The purpose of this article is to discuss some problems of the role of zone formation effectwhich are under active investigation nowadays. The formation length of hadron from particle-nucleus collision is derived and compared with those from relativistic ion collisions.