[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 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.
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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.
Physical Review D 01/2015; 91(3). DOI:10.1103/PhysRevD.91.034002 · 4.64 Impact Factor
[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 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.
Physics Letters B 10/2014; 742. DOI:10.1016/j.physletb.2015.02.013 · 6.13 Impact Factor
[Show abstract][Hide abstract] 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.
Physics Letters B 05/2014; 736. DOI:10.1016/j.physletb.2014.07.027 · 6.13 Impact Factor
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] ABSTRACT: The 1 D 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 0 J/ψ decay mode. It is demonstrated that established properties of the X(3872) are in a drastic conflict with the 1 D 2 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++.
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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.
Physics Letters B 06/2013; 726(1). DOI:10.1016/j.physletb.2013.08.073 · 6.13 Impact Factor
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] ABSTRACT: We point out the physics opportunities of future high-luminosity B-factories
at the Upsilon(5S) resonance and above. In this paper we discuss numerous
interesting investigations, which can be performed in the e+e- centre-of-mass
energy region from the Upsilon(5S) and up to 11.5 GeV, 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 Upsilon(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 Upsilon(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 B_J 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 Q^2 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 12.5 GeV, 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.
European Physical Journal A 10/2012; 49(1). DOI:10.1140/epja/i2013-13007-x · 2.74 Impact Factor
[Show abstract][Hide abstract] 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.
International Journal of Modern Physics E 01/2012; 18(03). DOI:10.1142/S0218301309012768 · 1.34 Impact Factor
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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.
European Physical Journal A 08/2011; 47(8):1-10. DOI:10.1140/epja/i2011-11101-9 · 2.74 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A possibility is suggested for the formation in the Universe of domains occupied by coherent‐like states of strongly correlated quark‐antiquark pairs. Only domains of the radius larger than 5 fm had a chance to survive over the entire history of the Universe, while the requirement of stability against the gravitational collapse restricts the maximum domain’s radius to 14 km. Within the Generalised Nambu–Jona‐Lasinio model, an exponential suppression with the domain’s volume is found for the overlap between the macroscopic ground‐state wavefunction of the quark‐antiquark pairs and the QCD vacuum. This finding supports, at the microscopic level, the above arguments in favour of the stability of the domains.
[Show abstract][Hide abstract] ABSTRACT: A theoretical analysis of the recent experimental data from the Belle and BABAR Collaborations on the charmonium state X(3872) is performed. The analysis takes into account the proximity of an S-wave mesonic threshold and a possible presence of molecule component in the resonance wave function, finite width of the molecule constituents, and a possible interference in the final state. In particular, a model-independent approach is formulated, based on the Flatte parametrisation of near-threshold observables as well as on the Weinberg analysis of the nature of weakly bound systems generalised to the case of unstable constituents. Conclusion is made that the X(3872) is generated dynamically by a strong coupling of the bare chic1 charmonium to the DD* hadronic channel, with a large admixture of the DD* molecular component.
[Show abstract][Hide abstract] ABSTRACT: Formation of stable domains filled with strongly correlated coherent quark
matter is discussed in general terms and is exemplified further in the
framework of the Generalised Nambu-Jona-Lasinio model. It is argued that such
domains, if exist in the Universe, appear dark to an external observer.
[Show abstract][Hide abstract] ABSTRACT: The D21 charmonium assignment for the X(3872) meson is considered, as prompted by a recent result from the BABAR Collaboration, favoring 2-+ quantum numbers for X. It is shown that established properties of X(3872) are in a drastic conflict with the D21 cc¯ assignment.