# Measurements of the $$\chi$$$$_c$$ and $$\chi$$$$_b$$ quarkonium states in $$\rho$$$$\rho$$ collisions with the ATLAS experiment

Chisholm , Andrew Stephen (2014). Measurements of the $$\chi$$$$_c$$ and $$\chi$$$$_b$$ quarkonium states in $$\rho$$$$\rho$$ collisions with the ATLAS experiment. University of Birmingham. Ph.D.

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## Abstract

The chi_b bottomonium states are observed through the reconstruction of the radiative decays chi_b(nP)→Upsilon(1S) gamma using 4.4/fb of pp collision data collected at sqrt(s) = 7 TeV with the ATLAS experiment. The production of the chi_b(1P) and chi_b(2P) bottomonium states is observed in addition to a candidate for a new bottomonium state, consistent with theoretical expectations for the chi_b(3P) states. The production-averaged mass barycentre for the chi_b(3P) candidate is measured to be 10541$$\pm$$11 (stat.) $$\pm$$ 30 (syst.) MeV. The consequences of this discovery for our understanding of bottomonium production phenomenology in hadronic collisions is reviewed. The production of the chi_c1 and chi_c2 charmonium states has been measured in sqrt(s) = 7 TeV pp collisions with the ATLAS experiment using a data sample representing an integrated luminosity of 4.5/fb. The prompt and non-prompt production cross sections for the chi_c1 and chi_c2 states are measured within the region | y(J/psi)| < 0.75. These measurements suggest that 24-28% of prompt J/psi are produced in feed-down from radiative chi_c1 and chi_c2 decays. The production of the chi_c2 state, relative to the chi_c1 state, is measured for both prompt and non-prompt production processes. This collection of measurements is compared to a number of theoretical predictions for chi_cJ production at the LHC. The branching fraction B(B$$\pm$$→chi_c1 K$$\pm$$) = (4.9$$_pm$$$$\pm$$ (stat.) $$\pm$$0.6 (syst.))x 10^-4 is also measured with the same dataset and chi_c event selection.

Type of Work: Thesis (Doctorates > Ph.D.)
Award Type: Doctorates > Ph.D.
Supervisor(s):
Supervisor(s)EmailORCID
Hawkes, ChrisUNSPECIFIEDUNSPECIFIED
Licence:
College/Faculty: Colleges (2008 onwards) > College of Engineering & Physical Sciences
School or Department: School of Physics and Astronomy
Funders: None/not applicable
Subjects: Q Science > QC Physics
URI: http://etheses.bham.ac.uk/id/eprint/5056

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