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A. Kudryavtsev

Publications and source records attributed to A. Kudryavtsev.

14 recordsLinked to original sources
arXiv2009

Extraction of the strong neutron-proton mass difference from the charge symmetry breaking in pn-->d pi0

We perform a complete calculation of charge symmetry breaking effects for the reaction pn -> d pi0 at leading order in chiral perturbation theory. A new leading-order operator is included. From our analysis we extract δm_N^{str}, the strong contribution to the neutron-proton mass difference. The value obtained, δm_N^{str} = 1.5 \pm 0.8 (exp.) \pm 0.5 (th.) MeV, is consistent with the result based on the Cottingham sum rule. This agreement provides a non-trivial test of our current understanding of the chiral structure of QCD.

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arXiv2007

Pion--deuteron scattering length in Chiral Perturbation Theory up to order χ^{3/2}

A complete calculation of the corrections to pion-deuteron scattering length up to order $χ^{3/2}$ with $χ=m_π/M_{N}$ is performed. The calculation includes the dispersive contributions and corrections due to the explicit treatment of the $Δ$ resonance. s-wave pion-nucleon scattering parameters are extracted from a combined analysis of modern experimental data.

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arXiv2007

Progress in NN --> NNpi

We survey the recent developments in the reaction $NN \to NNπ$ in effective field theory. We show that the proper construction of the production operator needs a careful separation of irreducible pieces from reducible ones. The result of this consideration is a complete cancellation of all loops in the production operator at NLO. Moreover, we show that this procedure brings the leading Weinberg-Tomozawa vertex on-shell, thus enhancing the corresponding contribution to the transition amplitude by a factor of 4/3 as compared to the commonly used value. We also discuss the role of the $Δ(1232)$ for the s-wave pion production. Being relatively sizable individually the direct and rescattering mechanisms of the $Δ$ excitation at NLO cancel each other to a large extent. Thus, we conclude that the net effect of the $Δ$ at NLO is very small.

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arXiv2007

Role of the Delta(1232) in pion-deuteron scattering at threshold within chiral effective field theory

We investigate the role of the delta isobar in the reaction $πd\to πd$ at threshold in chiral effective field theory. We discuss the corresponding power counting and argue that this calculation completes the evaluation of diagrams up to the order (m_pi/M_N)^(3/2), with m_pi (M_N) for the pion (nucleon) mass. The net effect of all delta contributions at this order to the pion-deuteron scattering length is (2.4 +/- 0.4)x 10^(-3) m_pi^{-1}.

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arXiv2006

Dispersive and absorptive corrections to the pion-deuteron scattering length

We present a parameter--free calculation of the dispersive and absorptive contributions to the pion--deuteron scattering length based on chiral perturbation theory. We show that once all diagrams contributing to leading order to this process are included, their net effect provides a small correction to the real part of the pion--deuteron scattering length. At the same time the sizable imaginary part of the pion--deuteron scattering length is reproduced accurately.

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arXiv2006

Advances in the field-theoretic understanding of pion production in nucleon-nucleon collisions

We study the production amplitude for the reaction $NN\to NNπ$ up to next-to-leading order in chiral perturbation theory. We show that the irreducible chiral loops at this order exactly cancel those terms that arise from the off-shell parts of the $πN$ rescattering vertex. This cancellation is required for formal consistency of the whole scheme. The net effect of the inclusion of all next-to-leading order loops is to enhance the leading rescattering amplitude by a factor of 4/3 compared to phenomenological studies, bringing its contribution to the cross section for $pp\to dπ^+$ close to the experimental value.

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arXiv2006

Insights on scalar mesons from their radiative decays

We estimate the rates for radiative transitions of the lightest scalar mesons f_0(980) and a_0(980) to the vector mesons rho and omega. We argue that measurements of the radiative decays of those scalar mesons can provide important new information on their structure.

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arXiv2004

Flatte-like distributions and the a_0(980)/f_0(980) mesons

We explore the features of Flatte-like parametrizations. In particular, we demonstrate that the large variation in the absolute values of the coupling constants to the pi-eta (or pi-pi) and KKbar channels for the a_0(980) and f_0(980) mesons that one can find in the literature can be explained by a specific scaling behaviour of the Flatte amplitude for energies near the KKbar threshold. We argue that the ratio of the coupling constants can be much better determined from a fit to experimental data.

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arXiv2003

Evidence that the a0(980) and f0(980) are not elementary particles

We study the interesting problem of whether it is possible to distinguish composite from elementary particles. In particular we generalize a model-independent approach of S. Weinberg to the case of unstable particles. This allows us to apply our formalism to the case of the a0(980) and f0(980) resonances and to address the question whether these particles are predominantly genuine, confined quark states (of $\bar q q$ or $qq\bar q\bar q$ structure) or governed by mesonic components.

hep-ph↗
arXiv2000

Energy Dependence of the Near-Threshold Total Cross-Section for the pp --> pp eta' Reaction

Total cross sections for the pp --> pp eta' reaction have been measured in the excess energy range from Q = 1.53 MeV to Q = 23.64 MeV. The experiment has been performed at the internal installation COSY-11 using a stochastically cooled proton beam of the COoler SYnchrotron COSY and a hydrogen cluster target. The determined energy dependence of the total cross section weakens the hypothesis of the S-wave repulsive interaction between the eta' meson and the proton. New data agree well with predictions based on the phase-space distribution modified by the proton-proton final-state-interaction (FSI) only.

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arXiv1999

On momentum dependence of the reaction $π^- p \to ωn$ near threshold

We discuss the near-threshold behavior of the $ω$ production amplitude in the reaction $π^-p \to ωn$. In contrast to the results of earlier analyses we find that the averaged squared matrix element of the production amplitude must be a decreasing function of energy in order to describe the existing experimental data.

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arXiv1997

Skyrmions and domain walls in (2+1) dimensions

We study classical solutions of the vector O(3) sigma model in (2+1) dimensions, spontaneously broken to O(2)xZ2. The model possesses Skyrmion-type solutions as well as stable domain walls which connect different vacua. We show that different types of waves can propagate on the wall, including waves carrying a topological charge. The domain wall can also absorb Skyrmions and, under appropriate initial conditions, it is possible to emit a Skyrmion from the wall.

hep-th↗
arXiv1996

Mesons, Baryons and Waves in the Baby Skyrmion Model

We study various classical solutions of the baby-Skyrmion model in $(2+1)$ dimensions. We point out the existence of higher energy states interpret them as resonances of Skyrmions and anti-Skyrmions and study their decays. Most of the discussion involves a highly exited Skyrmion-like state with winding number one which decays into an ordinary Skyrmion and a Skyrmion-anti-Skyrmion pair. We also study wave-like solutions of the model and show that some of such solutions can be constructed from the solutions of the sine-Gordon equation. We also show that the baby-Skyrmion has non-topological stationary solutions. We study their interactions with Skyrmions.

hep-th↗