Observation of J/psi p resonances consistent with pentaquark states in Lambda_b^0 to J/psi K^- p decays

<p>The observation of structures consistent with charmonium-pentaquark states decaying to $J/\psi p$ in \Lambda_b⁰ \rightarrow J/\psi K^- p decays is presented. The data sample analyzed corresponds to an integrated luminosity of 3 fb^-1 acquired with the LHCb detector from 7 and 8 TeV $pp$ collisions. An amplitude analysis was performed which utilized all six kinematic degrees of freedom in the decay. It was shown that adequate descriptions of the data are unattainable with only K^- p resonances in the amplitude model. For satisfactory fits of the data, it was found to be necessary to include two $J/\psi p$ resonances, with each having significances of over 9 standard deviations. One has a mass of $4449.8\pm1.7\pm2.2$ MeV and a width of $39\pm5\pm16$ MeV, while the second is broader, with a mass of $4380\pm8\pm29$ MeV and a width of $205\pm18\pm87$ MeV. The J^P assignments could not be uniquely determined, though there is a preference for one to have spin $3/2$ and the other spin $5/2$ with an opposite parity to the first. The data sample was also inspected in a model-independent way for the presence of $J/\psi p$ or J/\psi K^- contributions. It was demonstrated at more than 9 standard deviations that the data cannot be described with K^- p contributions alone, and that $J/\psi p$ contributions play a dominant role in this incompatibility. These model-independent results support the model-dependent evidence for P_c⁺\rightarrow J/\psi p charmonium-pentaquark states provided by the amplitude analysis.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Year

2016

Author dc:creator

• Jurik, Nathan Philip

Contributors dc:contributor

• Tomasz Skwarnicki

• Hadrons
• LHC
• LHCb
• Pentaquarks
• Physical Sciences and Mathematics

Repository record dc:identifier

https://surface.syr.edu/etd/640

OAI identifier oai:identifier

oai:surface.syr.edu:etd-1640