A. V. Nefediev

Moscow Institute of Physics and Technology, Moskva, Moscow, Russia

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Publications (92)234.47 Total impact


  • No preview · Article · Feb 2016 · Journal of Physics Conference Series
  • V Baru · E Epelbaum · A A Filin · J Gegelia · A V Nefediev

    No preview · Article · Feb 2016 · Journal of Physics Conference Series
  • V. Baru · E. Epelbaum · A. A. Filin · J. Gegelia · A. V. Nefediev
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    ABSTRACT: Chiral extrapolation of the $X(3872)$ binding energy is investigated using the modified Weinberg formulation of chiral effective field theory for the $D \bar{D}^*$ scattering. Given its explicit renormalisability, this approach is particularly useful to explore the interplay of the long- and short-range $D \bar{D}^*$ forces in the $X(3872)$ from studying the light-quark (pion) mass dependence of its binding energy. In particular, the parameter-free leading-order calculation shows that the $X$-pole disappears for unphysical large pion masses. On the other hand, without contradicting the naive dimensional analysis, the higher-order pion-mass-dependent contact interaction can change the slope of the binding energy at the physical point yielding the opposite scenario of a stronger bound $X$ at pion masses larger than its physical value. An important role of the pion dynamics and of the 3-body $D\bar{D}\pi$ effects for chiral extrapolations of the $X$-pole is emphasised. The results of the present study should be of practical value for the lattice simulations since they provide a non-trivial connection between lattice points at unphysical pion masses and the physical world.
    No preview · Article · Dec 2015 · Physical Review D
  • V. Baru · E. Epelbaum · A. A. Filin · J. Gegelia · A. V. Nefediev
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    ABSTRACT: Chiral extrapolation of the $X(3872)$ binding energy is investigated using the modified Weinberg formulation of chiral effective field theory for the $D \bar{D}^*$ scattering. Given its explicit renormalisability, this approach is particularly useful to explore the interplay of the long- and short-range $D \bar{D}^*$ forces in the $X(3872)$ from studying the light-quark (pion) mass dependence of its binding energy. In particular, the parameter-free leading-order calculation shows that the $X$-pole disappears for unphysical large pion masses. On the other hand, without contradicting the naive dimensional analysis, the higher-order pion-mass-dependent contact interaction can change the slope of the binding energy at the physical point yielding the opposite scenario of a stronger bound $X$ at pion masses larger than its physical value. An important role of the pion dynamics and of the 3-body $D\bar{D}\pi$ effects for chiral extrapolations of the $X$-pole is emphasised. The results of the present study should be of practical value for the lattice simulations since they provide a non-trivial connection between lattice points at unphysical pion masses and the physical world.
    No preview · Article · Sep 2015
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    ABSTRACT: We propose a practical parametrization for the line shapes of near-threshold states compatible with all requirements of unitarity and analyticity. The coupled-channel system underlying the proposed parametrization includes a bare pole and an arbitrary number of elastic and inelastic channels treated fully nonperturbatively. The resulting formulas are general enough to be used for a simultaneous analysis of the data in all available production and decay channels of a given (system of) state(s) for a quite wide class of reactions. As an example, we fit the experimental data currently available for several decay channels for the charged $Z_b(10610)$ and $Z_b(10650)$ states in the spectrum of bottomonia and find a remarkably good overall description of the data.
    Preview · Article · Jul 2015 · Physical Review Letters
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    ABSTRACT: In a recent paper Phys.Rev.Lett. 111, 042002 (2013) (arXiv:1304.0846), the charmonium state X(3872) is studied in the framework of an effective field theory. In that work it is claimed that (i) the one-pion exchange (OPE) alone provides sufficient binding to produce the X as a shallow bound state at the $D^0\bar{D}^{*0}$ threshold, (ii) short-range dynamics (described by a contact interaction) provides only moderate corrections to the OPE, and (iii) the X-pole disappears as the pion mass is increased slightly and therefore the X should not be seen on the lattice, away from the pion physical mass point, if it were a molecular state. In this paper we demonstrate that the results of Phys.Rev.Lett. 111, 042002 (2013) (arXiv:1304.0846) suffer from technical as well as conceptual problems and therefore do not support the conclusions drawn by the authors.
    Full-text · Article · Jan 2015 · Physical Review D
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    ABSTRACT: Starting from the hypothesis that the X(3872) is a $D\bar D^*$ molecule, we discuss the radiative decays of the X(3872) into $\gamma J/\psi$ and $\gamma\psi'$ from an effective field theory point of view. We show that radiative decays are not sensitive to the long-range structure of the X(3872). In particular, contrary to earlier claims, we argue that the experimentally determined ratio of the mentioned branching fractions is not in conflict with a wave function of the X(3872) that is dominated by the $D\bar D^*$ hadronic molecular component.
    Full-text · Article · Oct 2014 · Physics Letters B
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    Achim Denig · Feng-Kun Guo · Christoph Hanhart · Alexey V. Nefediev
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    ABSTRACT: Direct production of the charmonium-like state $X(3872)$ in $e^+e^-$ collisions is considered in the framework of the vector meson dominance model. An order-of-magnitude estimate for the width $\Gamma(X\to e^+e^-)$ is found to be $\gtrsim$0.03 eV. The same approach applied to the $\chi_{c1}$ charmonium decay predicts the corresponding width of the order 0.1 eV in agreement with earlier estimates. Experimental perspectives for the direct production of the $1^{++}$ charmonia in $e^+e^-$ collisions are briefly discussed.
    Preview · Article · May 2014 · Physics Letters B
  • A. Denig · Feng-Kun Guo · C. Hanhart · A. V. Nefediev
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    ABSTRACT: Direct production of the charmonium-like state $X(3872)$ in $e^+e^-$ collisions is considered in the framework of the vector meson dominance model. An order-of-magnitude estimate for the width $\Gamma(X\to e^+e^-)$ is found to be $\gtrsim$0.03 eV. The same approach applied to the $\chi_{c1}$ charmonium decay predicts the corresponding width of the order 0.1 eV in agreement with earlier estimates. Experimental perspectives for the direct production of the $1^{++}$ charmonia in $e^+e^-$ collisions are briefly discussed.
    No preview · Article · Apr 2014
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    ABSTRACT: We discuss the role of non-perturbative pion dynamics on the near-threshold resonant X(3872) charmonium state, which is assumed to be an S-wave DD¯ ∗ bound system. We calculate the contribution to the width of the X(3872) from the DD¯ π intermediate state treated non-perturbatively and compare it with different approximate approaches. Further, we explore the quark-mass dependence of the pole position of the X(3872) state. We find that the trajectory of the X(3872) depends strongly on the assumed quark-mass dependence of the short-range interactions which can be determined in lattice QCD calculations.
    No preview · Article · Jan 2014
  • Yu. S. Kalashnikova · A. V. Nefediev
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    ABSTRACT: The 1D 2 charmonium assignment for the X(3872) is considered, which is compatible with the 2−+ quantum numbers, as favoured by the BABAR Collaboration analysis presented recently for the π +π −π 0J/ψ decay mode. It is demonstrated that established properties of the X(3872) are in a drastic conflict with the 1D 2c \(\bar c\) assignment. Furthermore, it is argued that a combined analysis of the data for different decay channels of the X, with the help of theoretical formulae which meet a number of constraints imposed by phenomenology, results in a suitable description of the experimental data for the X compatible with its quantum numbers 1++.
    No preview · Article · Nov 2013 · Physics of Atomic Nuclei
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    ABSTRACT: In this Technical Design Report (TDR) we describe the SuperB detector that was to be installed on the SuperB e+e- high luminosity collider. The SuperB asymmetric collider, which was to be constructed on the Tor Vergata campus near the INFN Frascati National Laboratory, was designed to operate both at the Upsilon(4S) center-of-mass energy with a luminosity of 10^{36} cm^{-2}s^{-1} and at the tau/charm production threshold with a luminosity of 10^{35} cm^{-2}s^{-1}. This high luminosity, producing a data sample about a factor 100 larger than present B Factories, would allow investigation of new physics effects in rare decays, CP Violation and Lepton Flavour Violation. This document details the detector design presented in the Conceptual Design Report (CDR) in 2007. The R&D and engineering studies performed to arrive at the full detector design are described, and an updated cost estimate is presented. A combination of a more realistic cost estimates and the unavailability of funds due of the global economic climate led to a formal cancelation of the project on Nov 27, 2012.
    Full-text · Article · Jun 2013
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    V. Baru · E. Epelbaum · A. A. Filin · C. Hanhart · U. -G. Meißner · A. V. Nefediev
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    ABSTRACT: We explore the quark-mass dependence of the pole position of the X(3872) state within the molecular picture. The calculations are performed within the framework of a nonrelativistic Faddeev-type three-body equation for the $D\bar{D}\pi$ system in the $J^{PC}=1^{++}$ channel. The $\pi D$ interaction is parametrised via a $D^*$ pole, and a three-body force is included to render the equations well defined. Its strength is adjusted such that the X(3872) appears as a $D\bar{D}^*$ bound state 0.5 MeV below the neutral threshold. We find that the trajectory of the X(3872) depends strongly on the assumed quark-mass dependence of the short-range interactions which can be determined in future lattice QCD calculations. At the same time we are able to provide nontrivial information on the chiral extrapolation in the $X$ channel.
    Full-text · Article · Jun 2013 · Physics Letters B
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    Yu. S. Kalashnikova · A. V. Nefediev
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    ABSTRACT: We re-examine one-pion exchange as a possible binding mechanism in the X(3872) charmonium-like state and argue it to be not sufficiently binding for this purpose. We conclude therefore that other short-range dynamics are responsible for the X formation.
    Preview · Article · Dec 2012 · JETP Letters
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    ABSTRACT: We point out the physics opportunities of future high-luminosity B-factories at the ϒ(5S) resonance and above. Currently the two B-factories, the SuperB factory in Tor Vergata, Italy and the Belle II factory in KEK, Japan, are under development and are expected to start operation in 2017 and 2016, respectively. In this paper we discuss numerous interesting investigations, which can be performed in the e +e − center-of-mass energy region from the ϒ(5S) and up to 11.5GeV, where an efficient data taking operation should be possible with the planned B-factories. These studies include abundant Bs production and decay properties; independent confirmation and, if found, exhaustive exploration of Belle’s claimed charged bottomonia; clarification of puzzles of interquarkonium dipion transitions; extraction of the light-quark mass ratio from hadronic ϒ(5S) decays; analysis of quarkonium and exotic internal structure from open flavour decays, leading to severe SU(3) symmetry violations; clarification of whether a hybrid state has similar mass to the ϒ(5S) bottomonium, making it a double state; searches for molecular/tetraquark states that should be more stable with heavy quarks; completion of the table of positive-parity BJ mesons and study of their basic properties; production of \(\Lambda _b \bar \Lambda _b\) heavy baryon pairs, that, following weak decay, open vistas on the charmed baryon spectrum and new channels to study CP violation; confirmation or refutation of the deviation from pQCD of the pion transition form factor, by extending the Q2 reach of current analysis; and possibly reaching the threshold for the production of triply charmed baryons. If, in addition, the future colliders can be later upgraded to 12.5GeV, then the possibility of copious production of \(B_c \bar B_c\) pairs opens, entailing new studies of CP violation and improved, independent tests of the CKM picture (through determination of V bc , and of effective theories for heavy quarks.
    Full-text · Article · Oct 2012 · European Physical Journal A
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    A. V.nefediev · Yu. A.simonov · M. A.trusov
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    ABSTRACT: The theory of confinement and deconfinement is discussed as based on the properties of the QCD vacuum. The latter are described by field correlators of color-electric and color-magnetic fields in the vacuum, which can be calculated analytically and on the lattice. As a result one obtains a self-consistent theory of the confined region in the (μ, T) plane with realistic hadron properties. At the boundary of the confining region, the color-electric confining correlator vanishes, and the remaining correlators describe strong nonperturbative dynamics in the deconfined region with (weakly) bound states. Resulting equation of state for μ = 0, p(T), are in good agreement with lattice data. Phase transition occurs due to evaporation of a part of the color-electric gluon condensate, and the resulting critical temperatures Tc(μ) for different nf are in good correspondence with available data.
    Full-text · Article · Jan 2012 · International Journal of Modern Physics E
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    ABSTRACT: We re-analyse the two- and three-pion mass distributions in the decays X(3872)->rho J/psi and X(3872)->omega J/psi and argue that the present data favour the 1++ assignment for the quantum numbers of the X.
    Preview · Article · Nov 2011 · Physical review D: Particles and fields
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    ABSTRACT: We investigate the role played by the three-body DD̅ π dynamics on the near-threshold resonance X(3872) charmonium state, which is assumed to be formed by nonperturbative DD̅ * dynamics. It is demonstrated that, as compared to the naive static-pions approximation, the imaginary parts that originate from the inclusion of dynamical pions reduce substantially the width from the DD̅ π intermediate state. In particular, for a resonance peaked at 0.5 MeV below the D0D̅ *0 threshold, this contribution to the width is reduced by about a factor of 2, and the effect of the pion dynamics on the width grows as long as the resonance is shifted towards the D0D̅ 0π0 threshold. Although the physical width of the X is dominated by inelastic channels, our finding should still be of importance for the X line shapes in the DD̅ π channel below DD̅ * threshold. For example, in the scattering length approximation, the imaginary part of the scattering length includes effects of all the pion dynamics and does not only stem from the D* width. Meanwhile, we find that another important quantity for the X phenomenology, the residue at the X pole, is weakly sensitive to dynamical pions. In particular, we find that the binding energy dependence of this quantity from the full calculation is close to that found from a model with pointlike DD̅ * interactions only, consistent with earlier claims. Coupled-channel effects (inclusion of the charged DD̅ * channel) turn out to have a moderate impact on the results.
    Preview · Article · Oct 2011 · Physical review D: Particles and fields
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    ABSTRACT: We investigate the role played by the three-body $D\bar{D}\pi$ dynamics on the near-threshold resonance X(3872) charmonium state, which is assumed to be formed by nonperturbative $D\bar D^*$ dynamics. It is demonstrated that, as compared to the naive static-pions approximation, the imaginary parts that originate from the inclusion of dynamical pions reduce substantially the width from the $D\bar{D}\pi$ intermediate state. In particular, for a resonance peaked at 0.5 MeV below the $D^0\bar D^{*0}$ threshold, this contribution to the width is reduced by about a factor of 2, and the effect of the pion dynamics on the width grows as long as the resonance is shifted towards the $D^0\bar{D^0}\pi^0$ threshold. Although the physical width of the $X$ is dominated by inelastic channels, our finding should still be of importance for the $X$ line shapes in the $D\bar{D}\pi$ channel below $D{\bar D}^*$ threshold. For example, in the scattering length approximation, the imaginary part of the scattering length includes effects of all the pion dynamics and does not only stem from the $D^*$ width. Meanwhile, we find that another important quantity for the $X$ phenomenology, the residue at the $X$ pole, is weakly sensitive to dynamical pions. In particular, we find that the binding energy dependence of this quantity from the full calculation is close to that found from a model with pointlike $D\bar D^*$ interactions only, consistent with earlier claims. Coupled-channel effects (inclusion of the charged $D\bar{D}^*$ channel) turn out to have a moderate impact on the results.
    Preview · Article · Aug 2011
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    C. Hanhart · Yu. S. Kalashnikova · A. V. Nefediev
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    ABSTRACT: We investigate the interplay of quark and meson degrees of freedom in a physical state representing a near-threshold resonance for the case of multiple continuum channels. The aim is to demonstrate the full complexity of possible near-threshold phenomena. It turns out that those are especially rich, if both quark and meson dynamics generate simultaneously weakly coupled near-threshold poles in the S-matrix. We study the properties of this scenario in detail, such as t-matrix and production amplitude zeros, as well as various effects of the continuum channels interplay.
    Preview · Article · Aug 2011 · European Physical Journal A

Publication Stats

1k Citations
234.47 Total Impact Points

Institutions

  • 2015
    • Moscow Institute of Physics and Technology
      Moskva, Moscow, Russia
  • 2012-2015
    • National Research Nuclear University MEPHI
      Moskva, Moscow, Russia
  • 1997-2013
    • Institute for Theoretical and Experimental Physics
      Moskva, Moscow, Russia
  • 2001
    • Instituto Superior de Contabilidade e Administração de Lisboa
      Lisboa, Lisbon, Portugal