317 research outputs found
The Exotic XYZ Charmonium-like Mesons
Charmonium, the spectroscopy of c\bar{c} mesons, has recently enjoyed a
renaissance with the discovery of several missing states and a number of
unexpected charmonium-like resonances. The discovery of these new states has
been made possible by the extremely large data samples made available by the
B-factories at the Stanford Linear Accelerator Center and at KEK in Japan, and
at the CESR e^+e^- collider at Cornell. Conventional c\bar{c} states are well
described by quark potential models. However, many of these newly discovered
charmonium-like mesons do not seem to fit into the conventional c\bar{c}
spectrum. There is growing evidence that at least some of these new states are
exotic, i.e. new forms of hadronic matter such as mesonic-molecules,
tetraquarks, and/or hybrid mesons. In this review we describe expectations for
the properties of conventional charmonium states and the predictions for
molecules, tetraquarks and hybrids and the various processes that can be used
to produce them. We examine the evidence for the new candidate exotic mesons,
possible explanations, and experimental measurements that might shed further
light on the nature these states.Comment: 28 pages, 7 figures. Review for Ann Rev Nucl & Part Sc
Nonleptonic Decays and Lifetimes of b-quark and c-quark Hadrons
We review recent experimental results on lifetimes and hadronic decays of
hadrons that contain and quarks. The theoretical implications of these
results are also considered. An understanding of hadronic decays of heavy
quarks is required to interpret the CP violating asymmetries in decays that
will be observed in experiments planned for the near future.Comment: 74 pages, LATEX format with 12 figures. To appear in Annual Review of
Nuclear and Particle Science, Vol. 46. Also available at
http://www-physics.mps.ohio-state.edu/~phys111/b-physics/bphysics.html and by
anonymous ftp from ftp://pacific.mps.ohio-state.edu/pub/hepex/kh A serious
typographical error on p. 8 is corrected. Other errors and typos are also
correcte
On the elliptical flow in asymmetric collisions and nuclear equation of state
We here present the results of elliptical flow for the collision of different
asymmetric nuclei (10Ne20 +13 Al27, 18Ar40 +21 Sc45, 30Zn64 +28 Ni58, 36Kr86
+41 Nb93) by using the Quantum Molecular Dynamics (QMD) model. General features
of elliptical flow are investigated with the help of theoretical simulations.
The simulations are performed at different beam energies between 40 and 105
MeV/nucleon. A significant change can be seen from in-plane to out-of-plane
elliptical flow of different fragments with incident energy. A comparison with
experimental data is also made. Further, we predict, for the first time that,
elliptical flow for different kind of fragments follow power law dependence ?
C(Atot)? for asymmetric systems
Detecting the long-distance structure of the X(3872)
We study the decay within a molecular picture for the state. This decay mode is more sensitive to the long-distance structure of the resonance than its and decays, which are mainly controlled by the details of the wave function at short distances. We show that the final state interaction can be important, and that a precise measurement of this partial decay width can provide valuable information on the interaction strength between the charm mesons
Effective Field Theories for Heavy Quarkonium
We briefly review how nonrelativistic effective field theories give us a
definition of the QCD potentials and a coherent field theory derived quantum
mechanical scheme to calculate the properties of bound states made by two or
more heavy quarks. In this framework heavy quarkonium properties depend only on
the QCD parameters (quark masses and \als) and nonpotential corrections are
systematically accounted for. The relation between the form of the
nonperturbative potentials and the low energy QCD dynamics is also discussed.Comment: Invited Plenary talk at The 20th European Conference on Few-Body
Problems in Physics. September 10-14 2007. Pisa, Italy. To be published on
Few-Body System
Hidden charm and bottom molecular states
We investigate heavy quark symmetries for heavy light meson-antimeson systems in a contact-range effective field theory. In the SU(3) light flavor limit, the leading order Lagrangian respecting heavy quark spin symmetry contains four independent counter-terms. Neglecting 1/mQ corrections, three of these low energy constants can be determ1ined by theorizing a molecular description of the X(3872) and Zb(10610) states. Thus, we can predict new hadronic molecules, in particular the isovector charmonium partners of the Zb(10610) and the Zb(10650) states. We also discuss hadron molecules composed of a heavy meson and a doubly-heavy baryon, which would be related to the heavy meson-antimeson molecules thanks to the heavy antiquark-diquark symmetry. Finally, we also study the X(3872)→D0D¯0π0 decay, which is not only sensitive to the short distance part of the X(3872) molecular wave function, as the J/ψππ and J/ψ3π X(3872) decay modes are, but it is also affected by the long-distance structure of the resonance. Furthermore, this decay might provide some information on the interaction between the DD¯ charm mesons
Form factors of tetraquarks
The electromagnetic form factors of tetraquarks are calculated in the
framework of relativistic quark model at small and intermediate momentum
transfers Q^2 < 1 GeV^2. The charge radii of X(3872) and X(3940) tetraquarks
are determined.Comment: 15 pages, 2 figure
What two models may teach us about duality violations in QCD
Though the operator product expansion is applicable in the calculation of
current correlation functions in the Euclidean region, when approaching the
Minkowskian domain, violations of quark-hadron duality are expected to occur,
due to the presence of bound-state or resonance poles. In QCD finite-energy sum
rules, contour integrals in the complex energy plane down to the Minkowskian
axis have to be performed, and thus the question arises what the impact of
duality violations may be. The structure and possible relevance of duality
violations is investigated on the basis of two models: the Coulomb system and a
model for light-quark correlators which has already been studied previously. As
might yet be naively expected, duality violations are in some sense "maximal"
for zero-width bound states and they become weaker for broader resonances whose
poles lie further away from the physical axis. Furthermore, to a certain
extent, they can be suppressed by choosing appropriate weight functions in the
finite-energy sum rules. A simplified Ansatz for including effects of duality
violations in phenomenological QCD sum rule analyses is discussed as well.Comment: 17 pages, 6 figures; version to appear in JHE
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