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Branz, T. "Two-photon decay of heavy hadron molecules." Physical review. D. Particles, fields, gravitation, and cosmology 82.5 (2010):054010.

The Paper

The .pdf file can be found here (Note you need to be logged in to use this link)

An external link to the paper is here.

The DOI is 10.1103/PhysRevD.82.054010.


Traditionally when a new particle say a meson or baryon made up of two or three or more quarks is discovered,people are interested in the mass and Quantum numbers J^(PC)(I^G) of this particle. In this article the authors take a rather theoretical approach to investigate the properties of heavy hadron molecules- a “bound state of Mesons” called Heavy Hadrons such as the highly celebrated “ Mystery Meson” X(3872)- during their decay to a pair of photons. In order to understand the behavior of these heavy hadron molecules; the question posed here is, how will the “structure” of this Heavy Hadron influence

1) This decay Rate ( or Amplitude if you like) 2) Coupling ( of the molecular state to its constituent mesons).

In other words how will parameters like binding energy and constituent meson masses influence the above quantities?.

They Considered two scenarios: First in which these constituent mesons have point-particle-like interaction with the parent Heavy Hadron- a local theory of interaction and Second with non-point-particle-like interaction ( of course this seems Physical) with parent Heavy hadron- non-Local theory of interaction.

They claim that this non-local interaction is common with these Heavy Hadron Molecules compared to some what local interaction of their sister light hadrons like f_0(980).

Another bold claim is that, as you decrease the “size” of these heavy Hadron Molecules, the interaction asymptotically approaches a local interaction (between the heavy Hadron and its constituent mesons) depending on the mass of these constituent mesons. In other words, radiative decay width of Heavy Hadron molecule is very sensitive to finite size effects while that of Light Hadron Molecules is not sensitive to the cut off or finite size-effects provided the size is above 0.5GeV.

It is not very clear how the binding energy will affect this convergence into a local theory of interaction.

Q: Do hadronic molecules really exist, or is this more on a speculative side of “what if some of those weird particles that we see were hadronic molecules?” sort of paper? –Evil

A: I think the most highly celebrated experimentally observe Heavy Hadron is the X(3872) but calling it a molecule is rather only a theoretical way of interpreting its structure I think.Indeed the Light Hadron f_0(980) is highly thought of as a molecule because models interpreting it as a bound state of the K-K-bar meson have been somewhat quite successful in explaining its radiative decay properties.

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groups/journal_club/2010fall/branz_two_photon.txt · Last modified: 2010/11/07 21:10 by norbert