Publications (92)234.47 Total impact


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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 shortrange $D \bar{D}^*$ forces in the $X(3872)$ from studying the lightquark (pion) mass dependence of its binding energy. In particular, the parameterfree leadingorder calculation shows that the $X$pole disappears for unphysical large pion masses. On the other hand, without contradicting the naive dimensional analysis, the higherorder pionmassdependent 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 3body $D\bar{D}\pi$ 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 nontrivial connection between lattice points at unphysical pion masses and the physical world.  [Show abstract] [Hide abstract]
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 shortrange $D \bar{D}^*$ forces in the $X(3872)$ from studying the lightquark (pion) mass dependence of its binding energy. In particular, the parameterfree leadingorder calculation shows that the $X$pole disappears for unphysical large pion masses. On the other hand, without contradicting the naive dimensional analysis, the higherorder pionmassdependent 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 3body $D\bar{D}\pi$ 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 nontrivial connection between lattice points at unphysical pion masses and the physical world.  [Show abstract] [Hide abstract]
ABSTRACT: We propose a practical parametrization for the line shapes of nearthreshold states compatible with all requirements of unitarity and analyticity. The coupledchannel 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. 
Article: Remarks on the study of the X(3872) from Effective Field Theory with PionExchange Interaction
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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 onepion exchange (OPE) alone provides sufficient binding to produce the X as a shallow bound state at the $D^0\bar{D}^{*0}$ threshold, (ii) shortrange dynamics (described by a contact interaction) provides only moderate corrections to the OPE, and (iii) the Xpole 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.  [Show abstract] [Hide abstract]
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 longrange 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.  [Show abstract] [Hide abstract]
ABSTRACT: Direct production of the charmoniumlike state $X(3872)$ in $e^+e^$ collisions is considered in the framework of the vector meson dominance model. An orderofmagnitude 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.  [Show abstract] [Hide abstract]
ABSTRACT: Direct production of the charmoniumlike state $X(3872)$ in $e^+e^$ collisions is considered in the framework of the vector meson dominance model. An orderofmagnitude 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.  [Show abstract] [Hide abstract]
ABSTRACT: We discuss the role of nonperturbative pion dynamics on the nearthreshold resonant X(3872) charmonium state, which is assumed to be an Swave DD¯ ∗ bound system. We calculate the contribution to the width of the X(3872) from the DD¯ π intermediate state treated nonperturbatively and compare it with different approximate approaches. Further, we explore the quarkmass dependence of the pole position of the X(3872) state. We find that the trajectory of the X(3872) depends strongly on the assumed quarkmass dependence of the shortrange interactions which can be determined in lattice QCD calculations. 
Article: X(3872) as the 1 D 2 charmonium
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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++. 
Article: SuperB Technical Design Report
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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) centerofmass 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.  [Show abstract] [Hide abstract]
ABSTRACT: We explore the quarkmass dependence of the pole position of the X(3872) state within the molecular picture. The calculations are performed within the framework of a nonrelativistic Faddeevtype threebody 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 threebody 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 quarkmass dependence of the shortrange 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.  [Show abstract] [Hide abstract]
ABSTRACT: We reexamine onepion exchange as a possible binding mechanism in the X(3872) charmoniumlike state and argue it to be not sufficiently binding for this purpose. We conclude therefore that other shortrange dynamics are responsible for the X formation.  [Show abstract] [Hide abstract]
ABSTRACT: We point out the physics opportunities of future highluminosity Bfactories at the ϒ(5S) resonance and above. Currently the two Bfactories, 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 − centerofmass energy region from the ϒ(5S) and up to 11.5GeV, where an efficient data taking operation should be possible with the planned Bfactories. 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 lightquark 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 positiveparity 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. 
Article: Deconfinement and quarkgluon plasma
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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 colorelectric and colormagnetic fields in the vacuum, which can be calculated analytically and on the lattice. As a result one obtains a selfconsistent theory of the confined region in the (μ, T) plane with realistic hadron properties. At the boundary of the confining region, the colorelectric 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 colorelectric gluon condensate, and the resulting critical temperatures Tc(μ) for different nf are in good correspondence with available data.  [Show abstract] [Hide abstract]
ABSTRACT: We reanalyse the two and threepion 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.  [Show abstract] [Hide abstract]
ABSTRACT: We investigate the role played by the threebody DD̅ π dynamics on the nearthreshold resonance X(3872) charmonium state, which is assumed to be formed by nonperturbative DD̅ * dynamics. It is demonstrated that, as compared to the naive staticpions 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. Coupledchannel effects (inclusion of the charged DD̅ * channel) turn out to have a moderate impact on the results.  [Show abstract] [Hide abstract]
ABSTRACT: We investigate the role played by the threebody $D\bar{D}\pi$ dynamics on the nearthreshold 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 staticpions 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. Coupledchannel effects (inclusion of the charged $D\bar{D}^*$ channel) turn out to have a moderate impact on the results. 
Article: Interplay of quark and meson degrees of freedom in a nearthreshold resonance: Multichannel case
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ABSTRACT: We investigate the interplay of quark and meson degrees of freedom in a physical state representing a nearthreshold resonance for the case of multiple continuum channels. The aim is to demonstrate the full complexity of possible nearthreshold phenomena. It turns out that those are especially rich, if both quark and meson dynamics generate simultaneously weakly coupled nearthreshold poles in the Smatrix. We study the properties of this scenario in detail, such as tmatrix and production amplitude zeros, as well as various effects of the continuum channels interplay.
Publication Stats
1k  Citations  
234.47  Total Impact Points  
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Institutions

2015

Moscow Institute of Physics and Technology
Moskva, Moscow, Russia


20122015

National Research Nuclear University MEPHI
Moskva, Moscow, Russia


19972013

Institute for Theoretical and Experimental Physics
Moskva, Moscow, Russia


2001

Instituto Superior de Contabilidade e Administração de Lisboa
Lisboa, Lisbon, Portugal
