On 4/21/2013 6:15 PM, David Roberson wrote:
> It is important that the "Higgs" appears to have the correct spin.
This apparently is required to get to the starting gate. Are you aware
of any recent measurements of this interaction with other particles
which can only occur in this manner?
I can point you again to Matt Strassler's blog. Beyond that, it's hard
to discuss this matter unless you understand QFT.
If you have questions with his line of argument, I can try to clarify.
- Joe
http://profmattstrassler.com/2013/03/12/the-spin-of-the-higgs-like-particle/
"A quick note: I’ve had a number of questions from commenters about
whether the new Higgs-like particle really has spin 0 (as it must if it
is truly a Higgs particle) or whether it might have spin 2. Well, spin 2
(with positive parity) is now strongly disfavored, as a result of new
results from the ATLAS and CMS experiments at the Large Hadron Collider.
CMS has disfavored it at the 98.5-99.9% confidence level (the number
depending on assumptions about whether the particle is produced in
collisions of gluons or in collisions of a quark and anti-quark) using
their data from the particle’s decays to two lepton/anti-lepton pairs.
ATLAS has disfavored it at the 95%-99% confidence level (similarly
depending on assumptions) using their data from decays of the new
particle to a lepton, anti-lepton, neutrino and anti-neutrino.
Meanwhile, there is no reason for a spin-2 particle (especially with
negative parity) to have the relative decay probabilities that are
observed in the data, so the fact that all these probabilities are
similar to those of a simple Higgs particle disfavors spin 2 and favors
spin 0. And there’s simply no theory of a spin-2 particle (with either
parity) that doesn’t have other observable particles rather nearby in
mass. No one of these arguments is definitive, but in combination they
are pretty convincing.
"Meanwhile all the data is consistent with a spin 0 particle with decay
probabilities roughly similar to that of a Standard Model Higgs (the
simplest type of Higgs particle.)
"So let’s stop spending much bandwidth on spin 2: it is disfavored by
both ATLAS and CMS — directly by measurement of the particle’s spin, and
indirectly via its relative probabilities to decay to various types of
particles — and it is disfavored theoretically. The more important
measurement is to check whether this apparently spin-0 particle really
has positive parity, or whether it has a mix of positive and negative
parity."
