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Can you help with particle physics?

  1. Mar 19, 2003 #1
    I'd really appreciate any help you can give me with the following questions:

    Use lepton universality and lepton-quark symmetry (ignore quark mixing) to estimate the branching ratios for:

    a) b -> c + e- + anti-electronneutrino
    b) tau -> e- + anti-electronneutrino + tauneutrino

    Surely (a) is not possible without quark mixing? Isn't it true that without quark mixing, quarks can change flavour but only within their generation, e.g. can have u -> d but not u -> s?

    b) I think for this question I just need to look at the ratio of the masses of the mu and the e-, since all differences in their interactions are due to their difference in mass, is this correct? So the answer I would give would be mass(e-)/mass(mu).

    Why does observation of the process
    antimuneutrino + e- -> antimuneutrino + e-
    constitute unambiguous evidence for weak neutral currents, whereas the observation of
    antielectronneutrino + e- -> antielectronneutrino + e-
    does not?

    I've no idea about this, I'd have thought either scattering process could be an electromagnetic interaction; doesn't any interaction involving the Z have an equivalent involving photons?
  2. jcsd
  3. Mar 19, 2003 #2

    Tom Mattson

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    Staff Emeritus
    Science Advisor
    Gold Member

    This one's a little advanced for Homework Help. We typically get inclined planes and calculus problems. It will be more likely to get noticed here, in Theoretical Physics.

    I'll take a stab at it later.
  4. Mar 22, 2003 #3
    shouldn t it be the ratio of the tau to the electron for this reaction?

    photons cannot couple to neutral particles. so photons cannot interact with neutrinos.

    but i d say the nu_e reaction is not unambiguous evidence for weak neutral currents, because it this reaction could procede with a W boson. not so in the nu_mu case.
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