Direct X(3872) production in e+e- collisions

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.Comment: LaTeX2e, 11 pages, 1 figure, version published in Phys.Lett.

Exact characterization of O(n) tricriticality in two dimensions

We propose exact expressions for the conformal anomaly and for three critical exponents of the tricritical O(n) loop model as a function of n in the range $-2 \leq n \leq 3/2$. These findings are based on an analogy with known relations between Potts and O(n) models, and on an exact solution of a 'tri-tricritical' Potts model described in the literature. We verify the exact expressions for the tricritical O(n) model by means of a finite-size scaling analysis based on numerical transfer-matrix calculations.Comment: submitted to Phys. Rev. Let

A Storage-Efficient and Robust Private Information Retrieval Scheme Allowing Few Servers

Since the concept of locally decodable codes was introduced by Katz and Trevisan in 2000, it is well-known that information the-oretically secure private information retrieval schemes can be built using locally decodable codes. In this paper, we construct a Byzantine ro-bust PIR scheme using the multiplicity codes introduced by Kopparty et al. Our main contributions are on the one hand to avoid full replica-tion of the database on each server; this significantly reduces the global redundancy. On the other hand, to have a much lower locality in the PIR context than in the LDC context. This shows that there exists two different notions: LDC-locality and PIR-locality. This is made possible by exploiting geometric properties of multiplicity codes

Implications of heavy quark spin symmetry on heavy meson hadronic molecules

In recent years, many heavy mesons and charmonia were observed which do not fit in the conventional quark model expectations. Some of them are proposed to be hadronic molecules. Here we investigate the consequences of heavy quark spin symmetry on these heavy meson hadronic molecules. Heavy quark spin symmetry enables us to predict new heavy meson molecules and provides us with a method to test heavy meson molecule assumptions of some newly observed states. In particular, we predict an \eta_c'f_0(980) bound state as the spin-doublet partner of the Y(4660) proposed as a \psi'f_0(980) bound state with a mass of 4616^{+5}_{-6} MeV and the prominent decay mode \eta_c'\pi \pi. The width is predicted to be \Gamma(\eta_c'\pi\pi)=60\pm30 MeV. The pi^+\pi^- invariant mass spectrum and the line shape are calculated. We suggest to search for this state in B^{\pm}-->\eta_c'K^{\pm}\pi^+\pi^-, whose branching fraction is expected to be large.Comment: 4 pages, 2 figure

Parametrizations of the Dark Energy Density and Scalar Potentials

We develop a theoretical method of constructing the scalar (quintessence or phantom) potential directly from the dimensionless dark energy function X(z), the dark energy density in units of its present value. We apply our method to two parametrizations of the dark energy density, the quiessence-Lambda ansatz and the generalized Chaplygin gas model, and discuss some features of the constructed potentials.Comment: 8 pages, 2 figures, ws-mpla.cls, Accepted for publication in Mod. Phys. Lett.

Search for excited charmonium states in e+e−e^+e^- Annihilation at s=10.6\sqrt{s}=10.6 GeV

We suggest searching for excited charmonium states in $e^+e^-$ annihilation via double charmonium production at $\sqrt{s}=10.6$ GeV with $B$ factories, based on a more complete leading order calculation including both QCD and QED contributions for various processes. In particular, for the C=+ states, the $\chi_{c0}(nP)$ (n=2,3) and $\eta_c(mS)$ (m=3,4) may have appreciable potentials to be observed; while for the C=- states, the $\eta_ch_c$ production and especially the $\chi_{c1}h_c$ production might provide opportunities for observing the $h_c$ with higher statistics in the future. A brief discussion for the X(3940) observed in the double charmonium production is included.Comment: 13 pages and 8 figures in PRD version; QED contribution added; experimental and theoretical developments since 2004 summarized; references adde

Parametrization of Quintessence and Its Potential

We develop a theoretical method of constructing the quintessence potential directly from the effective equation of state function $w(z)$, which describes the properties of the dark energy. We apply our method to four parametrizations of equation of state parameter and discuss the general features of the resulting potentials. In particular, it is shown that the constructed quintessence potentials are all in the form of a runaway type.Comment: 6 pages, 2 figures, LaTeX2

Remarks on the study of the X(3872) from Effective Field Theory with Pion-Exchange Interaction

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.Comment: LaTeX2e, 7 pages, 2 figures, to appear in Phys.Rev.