# Is spin one still possible for the Higgs?

1. Feb 22, 2013

### John le Roy

I seem remember hearing that spin-1 was ruled out but since reading this paper I am unable to find any info on spin-1 Higgs. Has there been any further developments on this? Honestly, I am not a particle guy so I'm not sure on the details... can someone explain why Higgs' particle has to have spin zero?

The Need to Fairly Confront Spin-1 for the New Higgs-like Particle
http://arxiv.org/abs/1211.2288
John P. Ralston

Spin-1 was ruled out early in LHC reports of a new particle with mass near 125 GeV. Actually the spin-1 possibility was dismissed on false premises, and remains open. Model-independent classification based on Lorentz invariance permits nearly two dozen independent amplitudes for spin-1 to two vector particles, of which two remain with on-shell photons. The Landau-Yang theorems are inadequate to eliminate spin-1. Theoretical prejudice to close the gaps is unreliable, and a fair consideration based on experiment is needed. A spin-1 field can produce the resonance structure observed in invariant mass distributions, and also produce the same angular distribution of photons and $ZZ$ decays as spin-0. However spin-0 cannot produce the variety of distributions made by spin-1. The Higgs-like pattern of decay also cannot rule out spin-1 without more analysis. Upcoming data will add information, which should be analyzed giving spin-1 full and unbiased consideration that has not appeared before.

2. Feb 22, 2013

### Staff: Mentor

I expect new spin analyses presented at Moriond.

I cannot follow the argument given in the arXiv paper there, so I have no idea how convincing the decay to two photons is in that respect. I would be surprised if you get roughly the SM expectation for signal strength if both spin and the decay mechanism are completely different from the SM Higgs.

Last edited: Feb 22, 2013
3. Feb 22, 2013

### Bill_K

Ralston doesn't believe in the Landau-Yang Theorem, which says a spin 1 particle can't decay into two photons. Generally, I'd have to say the odds favor Landau and Yang.

Spin is a 3-dimensional concept, and proofs of the Landau-Yang Theorem use 3-vector arguments. Ralston constructs his interaction vertex out of 4-vectors, and he may be forgetting that a 4-vector contains both spin 1 and spin 0.

EDIT: Should point out that this refers to "the LHC's particle at 125 GeV." If it turns out to have spin 1 it would not be the Higgs, rather something else.

Last edited: Feb 22, 2013