Relativistic Vlasov approach to normal modes of nuclear matter.
A description of small amplitude oscillations around a stationary state in nuclear matter is formulated in the context of the relativistic Vlasov equation. We obtain a set of stationary linear modes of excitation satisfying orthogonality and completeness relations. For longitudinal modes it is explicitly shown that the system, which is made up of relativistic particles in interaction with an external scalar meson field, behaves like a system of fermions very weakly coupled to the scalar meson field, even if the coupling constant is large.

title: CHARM 2013: X(4260) as a Mixed Charmonium-Tetraquark State
abstract: Using the QCD sum rule approach we study the X(4260) state assuming that it can be described by a mixed charmonium-tetraquark current with $J^{PC}=1^{--}$ quantum numbers. For the mixing angle around $\theta=(53.0 \pm 0.5)^0$, we obtain a value for the mass which is in good agreement with the experimental mass of the X(4260). For the decay width into the channel $X \to J/\psi \pi \pi$, we find the value $\Gamma_{X \to J/\psi\pi\pi}=(4.1 \pm 0.6)$ MeV, which is much smaller than the total experimental width $\Gamma = (108\pm 12)$ MeV. However, considering the experimental upper limits for the decay of the X(4260) into open charm, we conclude that we cannot rule out the possibility of describing this state as a mixed charmonium-tetraquark state.

title: Width of exotics from QCD sum rules : Tetraquarks or molecules?
abstract: (4250) using QCD sum rules. Extending previous analyses regarding these states as diquark-antiquark states or molecules of D mesons, we introduce the Breit-Wigner function in the pole term.We ﬁnd that introducing the width increases the mass at small Borel window region. Using theoperator-product expansion up to dimension 8, we ﬁnd that the sum rules based on interpolatingcurrent with molecular components give a stable Borel curve from which both the masses andwidths of these resonances can be well obtained. Thus the QCD sum rule approach strongly favorsthe molecular description of these states.

title: MESONIC EXCITATIONS IN THE LINEAR SIGMA MODEL
abstract: A semiclassical version of the linear sigma model is studied in a variational approach. Specifically we study the bosonic spectroscopy for both bound states and resonances. We give a quantitative description of the pion and its two observed resonances.

title: Investigating the tetraquark structure of the new mesons
abstract: D ⁄0 0 (2308) reported by BELLE Collaboration, we can not discard the possibility that the BELLE’s resonance can be interpreted as the four-quark state studied here.

title: The J / psi D D* vertex
abstract: We employ QCD sum rules to calculate the J/yDD* form factors and coupling constant by studying the threepoint J/yD*D correlation function. We find that the momentum dependence of the form factor depends on the off-shell meson. We get a value for the coupling which is in agreement with estimates based on constituent quark model.

title: Comparison of low-PT photon production in high- and low-multiplicity collisions at the CERN ISR.
abstract: Low-transverse-momentum photon production at the CERN ISR is compared in high- and low-multiplicity events. High-transverse-energy pp collisions and low-multiplicity ..cap alpha cap alpha.. and pp collisions are studied. Relative photon-to-charged-track production is found to be the same in pp minimum bias, ..cap alpha cap alpha.. minimum bias, and pp high-transverse-energy collisions, to within 15%. No low-P/sub T/ excess is seen; the limits are dominated by systematic uncertainties.

title: Casimir energy for a three-piece relativistic string.
abstract: The Casimir energy for the transverse oscillations of a piecewise uniform closed string is calculated. The string consists of three pieces I, II, III of equal length, endowed with different tensions and mass densities, but adjusted in such a way that the velocity of sound always equals the velocity of light. In this sense the string forms a relativistic mechanical system. In the present paper the string is subjected to the following analysis: the dispersion function is derived and the zero-point energy is regularized using (i) a contour integration technique, being most convenient for the generalization of the theory to the case of finite temperatures, and (ii) the Hurwitz {zeta}-function technique, being usually the most compact method when the purpose is to calculate the Casimir energy numerically at {ital T}=0. The energy, being always nonpositive, is shown graphically in some cases as functions of the tension ratios I/II and II/III. The generalization to finite temperature theory is also given.

title: Casimir energy for a piecewise uniform string.
abstract: The Casimir energy for the transverse oscillations of a piecewise uniform closed string is calculated. The string consists of two parts I and II, endowed in general with different tensions and mass densities, although adjusted in such a way that the velocity of sound always equals the velocity of light. The dispersion equation is worked out under general conditions and the frequency spectrum is determined in special cases. When the ratio {ital L}{sub II}/L{sub I} between the string lengths is an integer, it is in principle possible to determine the frequency spectrum through solving algebraic equations of increasingly high degree. The Casimir energy relative to the uniform string is in general found to be negative, although in the special case {ital L}{sub I}=L{sub II} the energy is equal to zero. Delicate points in the regularization procedure are discussed; in particular, it turns out that a straightforward use of the Riemann {zeta}-function regularization method leads to an incorrect expression for the Casimir energy.

title: Casimir theory for the piecewise uniform string: Division into 2N pieces.
abstract: The Casimir energy for the transverse oscillations of a piecewise uniform string in Minkowski space is calculated. The string consists in general of 2[ital N] pieces of equal length, of alternating type I and type II material, endowed with different tensions [ital T][sub I], [ital T][sub II] and mass densities [rho][sub I], [rho][sub II] but adjusted in such a way that the velocity of sound always equals the velocity of light. This string model (with [ital N]=1) was introduced by the present authors in 1990. In the present paper, the governing equations are formulated in the case of arbitrary integers [ital N], although detailed calculations are restricted to the case [ital N]=2, i.e., a four-piece string. The Casimir energy is regularized using (i) the contour integration technique introduced by van Kampen, Nijboer, and Schram, and (ii) the Hurwitz [zeta]-function technique introduced by Li, Shi, and Zhang. The energy is found as a function of the tension ratio [ital x]=[ital T][sub I]/[ital T][sub II]. The finite temperature version of the theory is also given.

title: Rapidity and charge correlations of centrally produced charged particles in events with a high-momentum pi 0 near 11 degrees.