Perturbative QCD. II. OZI Decays; Drell—Yan Processes; Jets; Corrections to Weak Decays; SVZ Sum Rules; Exclusive Processes
The Zweig (1964) or 0ZI1 rule states that decays of heavy resonances which involve disconnected quark graphs (i.e., graphs that can be connected only via gluons) are suppressed. The rule works well for resonances like the ø or f’ and very well for the ψ or γ: in fact, the heavier the quarks and the resonance, the better the rule works. Consider, for example, the ψ particles made up of \( \bar cc \) quarks.
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- 1.Okubo (1963); Iizuka, Okada, and Shito (1966).Google Scholar
- 2.Altarelli, Ellis and Martinelli, (1978,1979); Kubar—Andre and•Paige (1979). See also Humpert and Van Neerven (1981), and Harada and Muta (1980).Google Scholar
- 3.Note that a derivation based on the ultraviolet behaviour of the form factor, as given by Sudakov (1959) f( — q Google Scholar
- 4.) expl — C F log2 q-2- /u2 = p2(quark) 2ir is incorrect; it would yield an enhancement different from the infrared one (actually its square).Google Scholar
- 5.Or more than three partons. We will here consider only 0(as) corrections, so only processes with three partons have to be taken into account.Google Scholar
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- 7.Of course this scattering is also present at small p„ but, because there as( <P,2 >)~ 1, it is masked by rescat tering corrections which will, presumably, be responsible for diffractive/Regge scattering.Google Scholar
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- 9.The situation is a bit marginal for c quarks as 4mic 2. 8 GeV2, i.e., Q0 2/4mc 2 is only 0.25. This implies large corrections of some 25 percent, that are taken into account in a detailed analysis.Google Scholar
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- 11.Cf. Section 4.3 for definitions concerning weak interactions.Google Scholar
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