The Production Mechanism Lifetimes of Charmed Particles
- Ottawa U.
The discovery of the $$J/\psi$$; in 1974 [1], a resonance consisting of a charmed quarkantiquark pair was a major turning point in elementary particle physics. Predicted ten years earlier [2] to help explain the absence of strangeness changing neutral currents, the charm quark was expected to decay weakly into a strange quark [3]. The charm quark was also very important in the GW (Glashow, Iliopoulos and Maiani) model [4] of weak interactions. The $$J/\psi$$; provided indirect evidence for the existence of charm. However, it was not until two years later with the discovery [5] of the D0 that a particle with net charm was observed. A number of experiments subsequently looked for and discovered other charmed particles [6], 7J. The main difficulties in studying charmed particles are their short lifetimes ($$\tau \approx 10^{-13}$$ sec.) and low production rates ($$\sigma(pp \to c\bar{c} + X) \approx$$ = 80 $$\pm 60,\mu b$$) [7]. The short lifetimes correspond to very short decay lengths, of the order of a few hundred microns for charmed particles with a few GeV/c momentum. Due to the short decay length, nuclear emulsion with its high spatial resolution is an ideal detector since it is possible to actually see the production and subsequent decay of the charm particle. In 1977 a hybrid emulsion-spectrometer experiment (E-531) was set up in the wide-band neutrino beam at Fermilab. An advantage of the neutrinos is that they do not produce any tracks in the emulsion; therefore the background is very low and it is possible to leave the emulsion target in the beam for several months. Results using data collected from November 1978 to February 1979 (referred to as the first run) have already been published in 'numerous theses [8,9,10,11] and articles [12,13,14,15,16,17]. The exposure time was only about four months while the search for events in the emulsion and their subsequent analysis took several years. This thesis will discuss the data obtained in a second run of the experiment which collected data from November 1980 to May 1981, and will combine the data of the two runs together. This experiment was one of the first to obtain a large enough number of charmed particles to measure the lifetimes accurately. It was also the first experiment able to study the production of charmed particles by neutrinos .
- Research Organization:
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP)
- DOE Contract Number:
- AC02-07CH11359
- OSTI ID:
- 1433229
- Report Number(s):
- FERMILAB-THESIS-1987-22; 259376
- Country of Publication:
- United States
- Language:
- English
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