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Simulation of ηc → γγ at PANDA
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Nuclear and Particle Physics, Nuclear Physics.
Manuscript (Other academic)
URN: urn:nbn:se:uu:diva-95419OAI: oai:DiVA.org:uu-95419DiVA: diva2:169615
Available from: 2007-02-02 Created: 2007-02-02 Last updated: 2010-01-13Bibliographically approved
In thesis
1. The Charm of Excited Glue: Charmonium in e+e and ppbar collisions
Open this publication in new window or tab >>The Charm of Excited Glue: Charmonium in e+e and ppbar collisions
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis treats the mass range of charmonium states and excited gluonic fields in two experiments, BESII and PANDA, and outlines a phenomenological model that connects them.

In BESII, e+e form a charmonium initial state, which is utilised as a source for secondary particles. The analysed channels, ψ´→ γK+K and ψ´→ γπ+π, give access to intermediate scalar states such as the two glueball candidates: f0(1500) and f0(1710). The f0(1710) is indeed observed in decay into both π+π and K+K and the f0(1500) is accepted as a necessary part of the π+π signal at the moderate 5% level. In addition, we observe the two tensor states f2(1270) (in both channels) and f2´(1525) (in K+K), but the need for the f2´(1525) is not firmly established. The region around 2 GeV/c2 is fitted with an f4(2050) and an f0(2200) in π+π. This region is fairly flat in K+K with a slight peak at the f0(2200). Branching ratios for all eight channels are given. A fit to the angular distribution of ψ´→ γ f2(1270) → γ π+πgave two possible solutions for the relative importance of helicity projections zero, one and two.

The future ppbar experiment PANDA is still in the development phase; important physics goals have been defined and we are now taking on the laborious task of constructing a detector that is able to fulfil them. A simulation investigation of a theoretically preferred JPC=1–+ charmonium hybrid (Hc) is presented: ppbarHcπ0/η, Hcχc1 (π0π0)S–wave, χc1J/ψπ0, with a final state of seven photons and a lepton pair. To detect this channel next to full coverage of CM phase space is needed and as little material as possible before the electromagnetic calorimeter.

A second simulation study of ppbar → ηcγγ at PANDA, suggests that the channel should be possible to detect with a signal-to-background ratio of 5±1 and a detection efficiency of at least 10%.

By assuming a constant matrix element we obtain a relation between the decay width for ψppbar+m, which has been measured at BES for several cases, and the cross section for ppbar charmonium production in association with the same light meson, m (at for example PANDA). Cross sections of ~300–3000 pb were predicted for J/ψ production and ~30 pb for ψ' production. Isoscalars seem to be preferred to isovectors in J/ψ production, this might however be an artefact of simplifications within the model. A comparison with the only measured cross section, ppbar → J/ψπ0, suggests that the model is useful as a first estimate.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2007. 156 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 269
Physics, hadron, charmonium, PANDA, antiproton, annihilations, spin-parity exotics, gluonic excitations, BES, hybrid, glueball, resonances, radiative decays, electromagnetic transitions, Fysik
urn:nbn:se:uu:diva-7460 (URN)978-91-554-6788-1 (ISBN)
Public defence
2007-02-23, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Polacksbacken, Uppsala, 13:15
Available from: 2007-02-02 Created: 2007-02-02Bibliographically approved

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