University of Coimbra

About: University of Coimbra is a education organization based out in Coimbra, Portugal. It is known for research contribution in the topics: Population & Context (language use). The organization has 14318 authors who have published 43067 publications receiving 994733 citations. The organization is also known as: UC & Universidade dos Estudos Gerais.

X(3872) and Other Possible Heavy Molecular States

Abstract: We perform a systematic study of the possible molecular states composed of a pair of heavy mesons such as $D\bar{D}$ , $D^{\ast}\bar{D}$ , $D^{\ast}\bar{D}^{\ast}$ in the framework of the meson exchange model. The exchanged mesons include the pseudoscalar, scalar and vector mesons. Through our investigation, we find the following results. (1) The structure X(3764) is not a molecular state. (2) There exists strong attraction in the range r<1 fm for the $D^{*}\bar{D}^{*}$ system with J=0,1. If future experiments confirm Z +(4051) as a loosely bound molecular state, its quantum number is probably J P =0+. Its partner state Φ **0 may be searched for in the π 0 χ c1 channel. (3) Vector meson exchange provides strong attraction in the $D^{\ast}\bar{D}$ channel together with pion exchange. A bound state solution may exist with a reasonable cutoff parameter Λ∼1.4 GeV. X(3872) may be accommodated as a molecular state dynamically although drawing a very definite conclusion needs further investigation. (4) The $B^{\ast}\bar{B}$ molecular state may exist.

Trapping light in open plasmonic nanostructures

Abstract: In open resonators the energy associated with a localized photonic excitation is lost in the form of a radiated wave, in the same manner that a classical charged particle in a curved orbit loses energy in the form of electromagnetic radiation. As a consequence, photonic modes in conventional spatially bounded open resonators have finite decay times. Here, we theoretically show that, surprisingly, in the limit of vanishing material loss, plasmons give the opportunity to have light localization in open spatially bounded systems with infinitely large lifetimes.