Meson properties in the quark model; a look at some outstanding problems.

Abstract

This thesis examines three problems of the quark model, split between two general areas.The first area involves models of meson decay. The calculations of decay widths in two such models, the 3 P 0 model and the flux-tube breaking model, were automated so that they could be easily done for any decay. The models were then used to investigate two particular problems. The first is the nature of the f 4 (2220) -although tentatively identified as the 3 F 4 ss meson by the Particle Data Group, its identity has been uncertain since its discovery in 1983. An exhaustive calculation of the strong decay modes of the 3 F 2 and 3 F 4 ss mesons was performed in order to examine the possibility that the state is a meson. It was found that the f 4 (2220) cannot be the 3 F 2 ss meson, and is unlikely to be the 3 F 4 , although given the uncertainties of the models the latter possibility cannot be ruled out. Instead the following explanation is proposed: that the broad state seen in hadron beam experiments is the 3 F 4 ss meson, and the narrow state seen in J/ψ radiative decay is a glueball. Further experimental data is needed to finally identify the f 4 (2220).The second problem investigated using meson decay models is the determination of the mixing angle between the K 1 (1270) and K 1 (1400) mesons. This was done by comparing predictions of the meson decay models for five partial decay widths and two ratios of D to S amplitudes to experimental data. A mixing angle of approximately 44 • was extracted, and the implications to the quark model Hamiltonian are discussed.The third problem falls in the second general area: final state interactions (FSI's).The effect of the strong interactions between the outgoing pions was examined for the reaction γγ → ππ near threshold. For charged pions, the experimental data agrees with the results calculated both with and without the effects of FSI's -better iii data is need to distinguish between the two. However, agreement was not obtained for neutral pions. It is believed that the discrepancy may be due to the effects of resonance production. If this proves to be the case, then the techniques used in this work could be extended to try to understand a long-standing puzzle: the nature of the unexplained structures seen in the cross sections of γγ → two vector mesons. iv AcknowledgmentsThis work was made possible by the support of a large number of people. I would especially like to thank my supervisor Stephen Godfrey, for doing those things that supervisors do. Also our collaborator (on the γγ → ππ work) Eric Swanson. A large number of other people answered physics questions (or tried to) -in particular Peter Watson and Mike Doncheski (Mike also read this thesis for me). A number of people answered computer questions -in particular Mike Boyce, Matthew Jones, Alan Barney and Wade Xiong. The theory post-docs and my fellow grad students in physics kept life interesting -in particular

Possibility of charmoniumlike state X(3915) as χc0(2P)Duan1, Luo2, Liu3 et al. 2020Phys. Rev. D382250View full textAdd to dashboardCite

“…E B and E C are energies of B and C mesons, which can be represented as E B/C = P 2 + m 2 B/C . The amplitude M LS can be given by the quark pair creation (QPC) model [55][56][57][58], which will be explicitly introduced later.…”

Strong decays of the higher isovector scalar mesons

“…The 3 P 0 model, also known as the quark-pair creation model, was originally introduced by Micu [19] and further developed by Le Yaouanc et al [20][21][22]. The 3 P 0 model has been widely applied to study strong decays of hadrons with considerable success [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. The main assumption of the 3 P 0 model is that the strong decay occurs through a quark-antiquark pair with the vacuum quantum number.…”

Combined study of2Sand1Dopen-charm mesons with natural spin-parity

“…According to the results in Ref [68],. we adopt a universal β value for the mesons involved in the discussed transitions.…”