
So What Is It? The bump on the two-photon plots - brian-armstrong
http://profmattstrassler.com/2015/12/18/so-what-is-it/
======
deepnet
The constraints on the signal are:

    
    
      decays into 2 photons, so must be a boson, integer spin, probably 0, 1 or 2
      both signals are 45Gev wide and look like the Higgs signal.
      ATLAS has a 1.6TeV bump at 2.5 Sigma, potentially a resonance.
      ATLAS has 747 GeV at 3.6 Sigma, CMS 766 GeV at 2.6 Sigma - combines to 4 Sigma although the Look Elsewhere Effect is disputed.
      ATLAS run1 at 8TeV did not see the signal.
      ATLAS has a 2.2 sigma for the 2 TeV excess that CMS saw in Run1, potentially indicating the 750GeV is a composite particle.
    

4 Sigma diPhoton excesses have turned out to be random fluctuations before.

[http://resonaances.blogspot.fr/2015/12/a-new-boson-
at-750-ge...](http://resonaances.blogspot.fr/2015/12/a-new-boson-
at-750-gev.html)

[http://motls.blogspot.co.uk/2015/12/first-batch-
of-9-pheno-p...](http://motls.blogspot.co.uk/2015/12/first-batch-of-9-pheno-
papers-on-new.html)

[http://www.math.columbia.edu/~woit/wordpress/?p=8174](http://www.math.columbia.edu/~woit/wordpress/?p=8174)

~~~
qrendel
> _integer spin, probably 0, 1 or 2_

So really 0 or 1. If it had spin 2 that would make it a graviton, which
seems... unlikely, to say the least.

~~~
panic
This article: [http://motls.blogspot.co.uk/2015/12/first-batch-
of-9-pheno-p...](http://motls.blogspot.co.uk/2015/12/first-batch-of-9-pheno-
papers-on-new.html) also mentions that spin 1 is disallowed by the Landau-Yang
Theorem. So it's most likely spin 0.

~~~
qrendel
It seems this theorem only applies to massive spin 1 particles, though:
[https://physics.stackexchange.com/questions/38427/proof-
of-y...](https://physics.stackexchange.com/questions/38427/proof-of-yangs-
theorem)

------
zzalpha
tl;dr we don't know what it is, or even if its a real signal.

But glad to see more content-free coverage of this news...

~~~
qrendel
I wouldn't call it "content-free," since it gives arguments for why it can't
be a heavier version of the Higgs, describes multiple hypotheses that will be
tested, as well as a timeframe for testing them.

~~~
zzalpha
Or it could be literally nothing at all because the signal isn't strong enough
to conclude anything is actually there to begin with. Which at this point is
pretty likely, especially for any hypothesis that doesn't fit with the
standard model.

The coverage of this has been absurdly breathless given the nature of the
"result". The bandwagon jumping (or as the author themselves so elegantly put
it, ambulance chasing) is truly something to behold...

~~~
panic
You should take up Luboš Motl on his bet:
[http://motls.blogspot.lu/2015/12/a-new-750-gev-boson-is-
very...](http://motls.blogspot.lu/2015/12/a-new-750-gev-boson-is-very-likely-
there.html)

