D Meson Production in e⁺e^- Annihilation [Thesis]

Technical Report · Fri Jun 01 00:00:00 EDT 2018

DOI:https://doi.org/10.2172/1453963· OSTI ID:1453963

Rapidis, Petros-Afentoulis ^[1]

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1. SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Stanford Univ., CA (United States)

The production of D mesons in e⁺e^- annihilation for the center-of-mass energy range 3.7 to 7.0 GeV has been studied with the MARK I magnetic detector at the Stanford Positron Electron Accelerating Ring facility. We observed a resonance in the total cross-section for hadron production in e⁺e^- annihilation at an energy just above the threshold for charm production. This resonance, which we name ψ", has a mass of 3772 ± 6 MeV/c², a partial width to electron pairs of 345 ± 85 eV/c², and decays almost exclusively into $$D\overline{D}$$ pairs. The ψ" provides a rich source of background-free and kinematically well defined D mesons for study. From the study of D mesons produced in the decay of the ψ" we have determined the masses of the D^o and D⁺ mesons to be 1863.3 ± 0.9 MeV/c² and 1868.3 ± 0.9 MeV/c² respectively. we also determined the branching fraction for D^o to K^-π⁺, K^-oπ⁺π^- and K^-π⁺π^-π⁺ to be (2.2 ± 0.6)%, (4.0 ± 1.3)%, and (3.2 ± 1.1)% and the branching fractions for D⁺ decay to K^-oπ⁺ and K^-π⁺π⁺ to be (1.5 ± 0.6)% and (3.9 ± 1.0)%. The average number of kaons per D decay was found to be 0.52 ± 0.14 K^o's and 0.42 ± 0.12 K⁺'s. The rate for inclusive production of D mesons at center-of-mass energies above the ψ" has been measured; we find that it can account for most, if not all, of the observed increase in the total hadronic cross-section for center-of-mass energies above 4 GeV. The inclusive momentum and energy spectra for D's have been measured at the highest available center-of-mass energy (7 GeV). The energy spectra are rapidly decreasing functions of energy with a slope similar to the slope of the charged pion spectrum at the same center-of-mass energy. This behaviour suggests that the fragmentation function of the charmed quark into charmed mesons is a decreasing function of the scaling variable z = 2E_D/E_CM.

• Research Organization: SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: AC02-76SF00515
• OSTI ID: 1453963
• Report Number(s): SLAC-R-220; SLAC-220
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS