Bottomonium Spectroscopy at Belle: Studies of Radiative and Hadronic Transitions

The large constituent quark mass of bottomonium, the bottom quark/anti-quark bound state $(bbbar)$, affords a rich spectroscopy in which the perturbative (non-relativistic) limit of Quantum Chromodynamics may be theoretically described and experimentally investigated. The radial excitations of bottomonia---with radial quantum number $n$, one unit of total angular momentum $(J=1)$, and orbital angular momentum $L=0$, labeled $Upsilon(nS)$---are copiously produced in electron--positron $(epem)$ collisions. The Belle Collaboration is a high energy physics experiment located at the KEKB B-Factory epem collider, based at KEK in Tsukuba, Japan. Belle has accumulated a large dataset near the FourS and ThreeS resonances, collectively containing more than 28 million ThreeS and 556 million FourS. Some of these decay to other bbbar states---with one unit of orbital angular momentum and total angular momentum $J=0,1,2$, labeled cbj{n} ---via the emission of a photon, with subsequent transition to the OneS with the emission of one or more gluons, which hadronize to form an om meson. This dissertation presents an analysis of the hadronic transitions chi_bJ(nP) rightarrow omega Upsilon(1S), where Upsilon(1S) rightarrow ell⁺ell^- with $ell=e,mu$, at Belle. The transitions of the $n=2$ triplet states provide a unique laboratory in which to study nonrelativistic quantum chromodynamics (NRQCD), as the kinematic threshold for production of an $omega$ and $Upsilon(1S)$ lies between the $J=0$ and $J=1$ states. The results presented herein constitute the first confirmation measurement of the $omega$ transitions of the chi_bJ(2P) states since their discovery in 2004, with evidence---in excess of three standard deviations---for the sub-threshold transition of the $J=0$ state. The branching fraction mathcal{B}big( chi_b0(2P) rightarrow omega Upsilon(1S) big) is found to be as large as the corresponding rate for the $J=2$ transition. The ratio of the $J=2$ to $J=1$ transitions is also measured and compared with the expectation from NRQCD, which we compute, revealing a $3.3sigma$ tension between experiment and theory. This work is leveraged to perform a search for radiative transitions of the $Upsilon(4S)$ to the chi_bJ(2P) and chi_bJ(3P) states, which are reconstructed in an inclusive $omega Upsilon(1S)$ final state. With no significant signal seen, limits are set on the corresponding branching fractions.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Physics

Department dc:contributor.department

Physics

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2022

Author dc:creator

• Stottler, Zachary Shaun

Chair dc:contributor.committeechair

• Piilonen, Leo E.

Committee members dc:contributor.committeemember

• Pitt, Mark L.
• Barnes, Edwin Fleming
• Mariani, Camillo

• Belle
• Particle Physics
• Heavy Quarkonium
• Bottomonium Spectroscopy
• Bottom Quarks

Statement dc:rights

• Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International

Licence dc:rights.uri

• http://creativecommons.org/licenses/by-nc-nd/4.0/

Language dc:language.iso

en

Dc Identifier Other

vt_gsexam:34300

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/109723