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A. Vereshagin

Publications and source records attributed to A. Vereshagin.

12 recordsLinked to original sources

CP violation in unpolarized e^+ e^- to charginos at one loop level

We study CP violation in e^+ e^- to \tildeχ_i^+\tildeχ_j^- in the framework of the MSSM. Though the cross section of this process is CP-even at the tree level even for polarized electron-positron beams, we show that it contains a CP-odd part at the one loop order and there are CP-odd observables that can in principle be measured even using unpolarized electron-positron beams. The relevant diagram calculations are briefly discussed and the results of selected (box) diagram computations are shown.

hep-ph

On the S-matrix renormalization in effective theories

This is the 5-th paper in the series devoted to explicit formulating of the rules needed to manage an effective field theory of strong interactions in S-matrix sector. We discuss the principles of constructing the meaningful perturbation series and formulate two basic ones: uniformity and summability. Relying on these principles one obtains the bootstrap conditions which restrict the allowed values of the physical (observable) parameters appearing in the extended perturbation scheme built for a given localizable effective theory. The renormalization prescriptions needed to fix the finite parts of counterterms in such a scheme can be divided into two subsets: minimal -- needed to fix the S-matrix, and non-minimal -- for eventual calculation of Green functions; in this paper we consider only the minimal one. In particular, it is shown that in theories with the amplitudes which asymptotic behavior is governed by known Regge intercepts, the system of independent renormalization conditions only contains those fixing the counterterm vertices with $n \leq 3$ lines, while other prescriptions are determined by self-consistency requirements. Moreover, the prescriptions for $n \leq 3$ cannot be taken arbitrary: an infinite number of bootstrap conditions should be respected. The concept of localizability, introduced and explained in this article, is closely connected with the notion of resonance in the framework of perturbative QFT. We discuss this point and, finally, compare the corner stones of our approach with the philosophy known as ``analytic S-matrix''.

hep-th

Renormalization programme for effective theories

We summarize our latest developments in perturbative treating the effective theories of strong interactions. We discuss the principles of constructing the mathematically correct expressions for the S-matrix elements at a given loop order and briefly review the renormalization procedure. This talk shall provide the philosophical basement as well as serve as an introduction for the material presented at this conference by A. Vereshagin and K. Semenov-Tian-Shansky.

hep-ph

Explicit equations for renormalization prescriptions in the case of pion-nucleon scattering

This talk is a natural continuation of that given by V.Vereshagin at this conference. We discuss some details not covered in that talk and review the calculational technique using the (πN)-elastic scattering as an example. Finally, we briefly mention some results of numerical comparison with experimental data. More technical details can be found in the talk by K.Semenov-Tian-Shansky (this conference)devoted to the analysis of elastic KN scattering.

hep-ph

Renormalization prescriptions and bootstrap in effective theories

We discuss the peculiar features of the renormalization procedure in the case of infinite-component effective theory. It is shown that in the case of physically interesting theories (namely, those leading to the amplitudes with asymptotic behavior governed by known Regge intercepts) the full system of required renormalization prescriptions only contains those needed to fix the minimal counterterm vertices with one, two, three and (in some cases) four lines. There is no necessity in imposing the prescriptions for n-leg counterterm vertices with (n > 4). Moreover, the prescriptions for n =< 4 cannot be taken arbitrary: an infinite system of bootstrap constraints must be taken into account. The general method allowing one to write down the explicit form of this system is explained and illustrated by the example of elastic scattering process.

hep-ph

Renormalization prescriptions in effective theory of pion-nucleon scattering

Using the results presented in the talk by V.Vereshagin (this conference), we illustrate the approach developed in earlier papers by the calculation of (πN) elastic scattering amplitude and explain how to derive corresponding bootstrap conditions. In the end, we briefly mention some results of numerical comparison with experimental data.

hep-ph

Bootstrap and the Parameters of Pion-Nucleon Resonances

In this talk we demonstrate the results of application of the perturbative effective theory formalism developed in recent papers to the calculation of $πN$ elastic scattering amplitude. Restrictions on the contributing resonance parameters are obtained and the low energy coefficients are calculated.

hep-ph

The resultant parameters of effective theory

This is the 4-th paper in the series devoted to a systematic study of the problem of mathematically correct formulation of the rules needed to manage an effective field theory. Here we consider the problem of constructing the full set of essential parameters in the case of the most general effective scattering theory containing no massless particles with spin J > 1/2. We perform the detailed classification of combinations of the Hamiltonian coupling constants and select those which appear in the expressions for renormalized S-matrix elements at a given loop order.

hep-th

Bootstrap equations in effective theories

We consider the general properties of effective field theories. We note that the freedom to fix the renormalization conditions in the effective field theory is not as great as it seems. The consideration of minimal requirements of correctness of the perturbative scheme based on Dyson's formula for S-matrix leads to severe restriction on the essential parameters of a theory and, hence, on the allowed set of renormalization conditions. In the first part we make a short review of the structure of localizable effective field theories. We discuss the conditions needed to ensure the correctness of the very first step of perturbative calculation of the S-matrix -- the construction of the tree-level amplitudes. In the second part we consider the examples demonstrating the main stages of derivation and analysis of the system of bootstrap equations.

hep-th

Bootstrap equations for effective theories and the calculation of the $G_T/G_V$ ratio

A method is described for dealing with effective theories of hadron scattering. It allows one to reduce the number of independent renormalization prescriptions in those theories and gives a possibility to make numerical predictions. As an illustration, we show the results of comparison with the known data on $ππ$, $πK$ and $πN$ elastic scattering. This work presents a generalization and the further development of our results first discussed at the MENU'99 Symposium

hep-ph

Chiral Symmetry in algebraic and analytic approaches

We compare among themselves two different methods for the derivation of results following from the requirement of polynomial boundedness of tree-level chiral amplitudes. It is shown that the results of the algebraic approach are valid also in the framework of the analytical one. This means that the system of Sum Rules and Bootstrap equations previously obtained with the help of the latter approach can be analyzed in terms of reducible representations of the unbroken Chiral group with the known structure of the mass matrix.

hep-ph