I attach a diagram of 4 of the (many) possible decay channels produced by the Higgs boson, and I have read that 57 % of the time, we find a bottom quark, antibottom quark pair resulting from this decay.

This question results from my earlier question and the answers I received.

Resonances and Particles

My question is: are the decay products produced totally probabilistic or can we "tune" an accelerator to increase the probability of a particular decay channel occuring?

My knowledge of particle physics is very limited, but I am guessing that, at higher energy levels this "tuning" (my apologies for the terminology) is less likely.

Decay Channels

  • $\begingroup$ The branching ratios are given by the couplings, so there is nothing to tune. The total "production cross section", which is the most important parameter for an experiment, that changes with beam energy and it can be resonant, but for the Higgs in the LHC it's not: image.slidesharecdn.com/elwmskcc20120420-140207110356-phpapp01/…. If we could control all the kinematic parameters in a collision, the Higgs should be easy to detect, I believe, but then we can't! $\endgroup$ – CuriousOne Jun 6 '15 at 21:46
  • $\begingroup$ But if the coupling constants were dominant, would that not reduce probability and the process would be more deterministic? Again, questions before reading up more is not a good idea. I would need to read up more on it, no doubt about that. What's a branching ratio, guessing it's the proportion you get out of each possible channel? $\endgroup$ – user81619 Jun 6 '15 at 21:52
  • $\begingroup$ The one way we can change the coupling is by changing the particle type for the collision (aka "new accelerator"). Once that's fixed and the beams are colliding head on (I have not seen a large angle collider design, but it might be an interesting question if that would make sense), then the remaining choice is polarizations. I don't know if that changes branching ratios or only the angular distribution of the detected decay particles. The ratios are basically the relative probabilities for decay channels and they are, if I get this right, much better known than the absolute probabilities. $\endgroup$ – CuriousOne Jun 6 '15 at 22:01

are the decay products produced totally probabilistic or can we "tune" an accelerator to increase the probability of a particular decay channel occuring?

Once a particle is produced, it decays completely independently of its production. The only dependence on production occurs when, for instance, a particle is produced in an entangled state and decays to a CP eigenstate; similarly, sometimes time dependence is also affected.

Also, the production affects the polarization for particles with spin, and this in turn affects the decay angular distribution (but not branching fractions).

  • $\begingroup$ Thanks you for that. I have only a slight background in this area. I completely misunderstood CuriousOne's comment about coupling constants determining branching fractions. I have a (good) bit of reading to do before posting a similar, but hopefully more coherent, question in the future. Thanks again. $\endgroup$ – user81619 Jun 10 '15 at 20:38
  • $\begingroup$ You're welcome - feel free to ask another question once you have learned more. Will answer if I can! $\endgroup$ – TimeVariant Jun 11 '15 at 2:06

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