GAUGE- and POINT-INVARIANT VERTICLES of NUCLEON-TO-RESONANCE INTERACTIONS. Physical Review

ПУБЛИКАЦИИ ЛАБОРАТОРИИ ФИЗИКИ ФУНДАМЕНТАЛЬНЫХ ВЗАИМОДЕЙСТВИЙ НИИ ФИЗИКИ ЮФУ

1. G. Vereshkov, N. Volchanskiy.

GAUGE- AND POINT-INVARIANT VERTICLES OF NUCLEON-TO-RESONANCE INTERACTIONS. // Physical Review C 87, 035203 (2013).

We construct interactions of nucleons N with higher-spin resonances R invariant under point and gauge transformations of the Rarita-Schwinger field. It is found for arbitrarily high spin of a resonance that the requirement of point- and gauge-invariance uniquely determines a Lagrangian of NR interactions with pions, photons, and vector mesons, which might reduce model ambiguity in effective-field calculations involving such vertices. Considering the NR interactions with photons and vector mesons, the symmetry provides a classification of three NR vertices in terms of their differential order. The Q2 dependencies of the point and gauge invariant form factors are considered in a vector-meson-dominance model. The model is in good agreement with experimental data. In addition, we point out some empirical patterns in the Q2dependencies of the form factors: low-Q2scaling of the N-Delta(1232) form factor ratios and relations between form factors for N-N(1520) and N-N(1680) transitions.

1. R. Pasechnik, V. Beilin, G. Vereshkov.

DARK ENERGY FROM GRAVITON-MEDIATED INTERACTIONS IN THE QCD VACUUM // Journal of Cosmology and Astroparticle Physics, 1306 (2013) 011.

Adopting the hypothesis about the exact cancellation of vacuum condensates contributions to the ground state energy in particle physics to the leading order in graviton-mediated interactions, we argue that the observable cosmological constant can be dynamically induced by an uncompensated quantum gravity correction to them after the QCD phase transition epoch. To start with, we demonstrate a possible cancellation of the quark-gluon condensate contribution to the total vacuum energy density of the Universe at temperatures $T<100$ MeV without taking into account the graviton-mediated effects. In order to incorporate the latter, we then calculate the leading-order quantum correction to the classical Einstein equations due to metric fluctuations induced by the non-perturbative vacuum fluctuations of the gluon and quark fields in the quasiclassical approximation. It has been demonstrated that such a correction to the vacuum energy density has a form $\varepsilon_{\Lambda}\sim G \Lambda_{\rm QCD}^6$, where $G$ is the gravitational constant, and $\Lambda_{\rm QCD}$ is the QCD scale parameter. We analyze capabilities of this approach based on the synthesis between quantum gravity in quasiclassical approximation and theory of non-perturbative QCD vacuum for quantitative explanation of the observed Dark Energy density.

1. G. Vereshkov, L. Marochnik.

1. V. Kuksa, N. Volchanskiy,

FACTORIZATION IN THE MODEL OF UNSTABLE PARTICLES WITH CONTINUOUS MASSES // European Journal of Physics C, 11, 182-194 (2013).

We study processes with unstable particles in intermediate time-like states. It is shown that the amplitudes squared of such processes factor exactly in the framework of the model of unstable particles with continuous masses. Decay widths and cross sections can then be represented in a universal factorized form for an arbitrary set of interacting particles. This exact factorization is caused by specific structure of propagators in the model. We formulate the factorization method and perform a phenomenological analysis of the factorization effects. The factorization method considerably simplifies calculations while leading to compact and reasonable results.

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1. V. Kuksa,R. Pasechnik, D. Vlasenko.

MASS SHELL SMEARING EFFECTS IN TOP PAIR PRODUCTION // International Journal of Modern Physics A27, (2012)1250072.

The top quark pair production and decay are considered in the framework of the smeared-mass unstable particles model. The results for total and differential cross sections in vicinity of $t\bar{t}$ threshold are in good agreement with the previous ones in the literature. The strategy of calculations of the higher order corrections in the framework of the model is discussed. Suggested approach significantly simplifies calculations compared to the standard perturbative one and can serve as a convenient tool for fast and precise preliminary analysis of processes involving intermediate time-like top quark exchanges in the near-threshold region.

Ссылка на полный текст статьи: DOI: 10.1142/S0217751X12500728

1. Yu.F. Novoseltsev, R.V. Novoseltseva and G.M. Vereshkov.

ON THE MASS COMPOSITION OF PRIMARY COSMIC RAYS IN THE ENERGY REGION 1015 – 1016eV // Journal of Physics G: Nuclear and Particle Physics, 39 (2012) 105202.

A method to determine the primary cosmic ray mass composition is presented. Data processing is based on the theoretical model representing the integral muon multiplicity spectrum as the superposition of the spectra corresponding to different kinds of primary nuclei. The method consists of two stages. In the first stage, the permissible intervals of primary nuclei fractions fi are determined on the basis of the EAS spectrum versus the total number of muons (Eμ ≥ 235 GeV). In the second stage, the permissible intervals of fi are narrowed by the fitting procedure. We use the experimental data on high multiplicity muon events (nμ ≥ 114) collected at the Baksan underground scintillation telescope. Within the framework of three components (protons, helium and heavy nuclei), the mass composition in the region 1015–1016eV has been defined: fp = 0.235 ± 0.02, fHe = 0.290 ± 0.02, fH = 0.475 ± 0.03. The average logarithmic mass is lnA1.93 and it is in good agreement with results before the knee energy obtained by JACEE, RUNJOB, ATIC. At energies above the knee (1015–1016eV) our analysis supports KASCADE results and contradicts to CASA-BLANCA and DICE data.

Ссылка на полный текст статьи: doi:10.1088/0954-3899/39/10/105202

1. Yu.F. Novoseltsev, R.V. Novoseltseva and G.M. Vereshkov. ON THE MASS COMPOSITION OF PRIMARY COSMIC RAYS IN THE ENERGY REGION 1015 – 1016eV // Journal of Physics:Conference Series, v.375 (2012) 052015.

The method of the determination of Primary Cosmic Ray mass composition is presented. Data processing is based on the theoretical model representing the EAS spectrum vs the total number of muons as the superposition of the spectra corresponding to different kinds of primary nuclei. The method consists of two stages. At the first stage, the permissible intervals of primary nuclei fractions fi are determined on the base of the EAS spectrum vs the total number of muons (Eμ ≥ 235 GeV). At the second stage, the permissible intervals of fi are narrowed by fitting procedure. Within the framework of three components (protons, helium and heavy nuclei), the mass composition in the region 1015 – 1016eV has been defined: fp = 0.235 ± 0.02, fHe = 0.290 ± 0.02, fH = 0.475 ± 0.03.

Ссылка на полный текст статьи:doi:10.1088/1742-6596/375/1/052015

Статьи, принятые к публикации во второй половине 2013 года

1. R. Pasechnik, V. Beilin, G. Vereshkov.

ON A POSSIBLE COMPENSATION OF THE QCD VACUUM CONTRIBUTION TO THE DARK ENERGY // // Physical Review D (2013).

We suggest one of the possible ways to compensate the large negative quantum-topological QCD contribution to the vacuum energy density of the Universe by means of a positive constant contribution from a cosmological Yang-Mills field. An important role of the exact particular solution for the Yang-Mills field corresponding to the finite-time instantons is discussed. An interesting connection of the compensation mechanism to the color confinement in the framework of instanton models has been pointed out. Besides the $\Lambda_{\rm QCD}$ scale, this proposal relies on one yet free dimensionless normalisation constant which cannot be fixed by the perturbative QCD theory, and thus should be fine-tuned for the exact compensation to hold.

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1. L. Marochnik, D. Usikov, G. Vereshkov.

MACROSCOPIC EFFECT OF QUANTUM GRAVITY: GRAVITON, GHOST AND INSTANTON CONDENSATION ON HORIZON SCALE OF THE UNIVERSE // Journal of Modern Physics, 8, (2013).

We discuss a special class of quantum gravity phenomena that occur on the scale of the Universe as a whole at any stage of its evolution. These phenomena are a direct consequence of the zero rest mass of gravitons, conformal non-invariance of the graviton field, and one-loop finiteness of quantum gravity. The effects are due to graviton-ghost condensates arising from the interference of quantum coherent states. Each of coherent states is a state of gravitons and ghosts of a wavelength of the order of the horizon scale and of different occupation numbers. The state vector of the Universe is a coherent superposition of vectors of different occupation numbers. To substantiate the reliability of macroscopic quantum effects, the formalism of one-loop quantum gravity is discussed in detail. The theory is constructed as follows: Faddeev-Popov path integral in Hamilton gauge -> factorization of classical and quantum variables, allowing the existence of a self-consistent system of equations for gravitons, ghosts and macroscopic geometry -> transition to the one-loop approximation. The ghost sector corresponding to the Hamilton gauge ensures of one-loop finiteness of the theory off the mass shell. The Bogolyubov-Born-Green-Kirckwood-Yvon (BBGKY) chain for the spectral function of gravitons renormalized by ghosts is used to build a self-consistent theory of gravitons in the isotropic Universe. We found three exact solutions of the equations, consisting of BBGKY chain and macroscopic Einstein's equations. The solutions describe virtual graviton, ghost, and instanton condensates and are reproduced at the level of exact solutions for field operators and state vectors. Each exact solution corresponds to a certain phase state of graviton-ghost substratum. We establish conditions under which a continuous quantum-gravity phase transitions occur between different phases of the graviton-ghost condensate.

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