High-Energy Photoproduction of the $$\rho$$ and $$\rho^{\prime}$$ Vector Mesons

Thesis/Dissertation · Sat Jan 01 04:00:00 EST 1977

DOI:https://doi.org/10.2172/1406598· OSTI ID:1406598

Bronstein, John Michael ^[1]

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1. Univ. of Illinois, Urbana, IL (United States)

In an experiment in the broad band photon beam at Fermilab we observe diffractive production of 2$$\pi^{\pm}$$ and 4$$\pi^{\pm}$$ states from Be, Al. Cu and Pb target~. The 2$$\pi^{\pm}$$data is dominated by the $$\rho$$(770) and the 4$$\pi^{\pm}$$is dominated by the $$\rho^{\prime}$$(1500). We measure the energy dependence of $$\rho$$ photo production from Be and see no evidence for energy variation of the forward cross section in the range 30 to 160 GeV. The forward cross section is consistent with its average value $$d\sigma$$/dt$$\mid_{0}$$= 3.42 $$\pm$$ 0.28 $$\mu b$$/$$GeV^2$ over the entire range. We obtain for the p' a mass of 1487± 20 MeV and a width of 675 $$\pm$$ 60 MeV. All quoted errors are statistical. A standard optical model analysis of the A dependence of the $$\rho$$ and $$\rho^{\prime}$$ photoproduction yields the following results. $$f^2_{\rho^{\prime}}$$ = 3.7 $$\pm$$ 0.7 $$\sigma_{\rho^{\prime}}$$/$$\sigma_{\rho}$$ = 1. 05 $$\pm$$ 0.18 Our results for the photon coupling constants are in good agreement with GVMD and with the $e^+e^-$ storage ring results. The approximate equality of the $$\rho$$-nucleon and $$\rho^{\prime}$$-nucleon total cross sections is inconsistent with the diagonal version of GVMD and provides strong motivation for including transitions between different vector mesons in GVMD.

• Research Organization: Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
• DOE Contract Number: AC02-07CH11359
• OSTI ID: 1406598
• Report Number(s): FERMILAB-THESIS--1977-06; COO--1195-412; UMI--78-03944; 123424
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS