## Thursday, March 17, 2016 ... /////

### Rumor: Moriond denied new ATLAS almost 5-sigma evidence of $750\GeV$ cernette

Ms Els Koffeman, a physics professor in Amsterdam, has coined the term "cernette" for the hypothetical object that manifests itself as the diphoton excess of the apparent invariant mass of $750\GeV$. One must be careful: there may be several cernettes.

While these four Les Horribles Cernettes (LHC) surely exist (or existed when the LHC tunnel was filled with some outdated equipment), does the particle of mass $750\GeV$ actually exist? Or are the 285 arXiv preprints (as of today) dedicated to a fairy?

That's almost certainly the #1 question asked by participants of Recontres de Moriond, a famous conference that takes place this week in Aosta Valley, Italy.

ATLAS and CMS have prepared lots of new results for the conference. Some of them were presented and some of them were negative.

For example, ATLAS has shown their search for the $X\to Z\gamma$ and there was no excess seen that would hint at a cernette. This is puzzling for most theories. You know, $Z\gamma$ and $\gamma\gamma$ are very similar channels – they are really rather random combinations of $B^0 B^0$, $B^0 W^0$, $W^0 W^0$, pairs of "basis vectors" of the $SU(2)\times U(1)$ gauge bosons that are more natural at higher energies.

If the diphoton excess results from $B^0 B^0$ which is mostly $\gamma\gamma$, the probability of a $Z\gamma$ may be suppressed but one must look into specific models and numbers whether they predict $Z\gamma$ to be already seen.

On the other hand, Jester (Adam Falkowski) spreads a rumor on his Twitter account that ATLAS has already accumulated almost 5-sigma evidence in favor of the diphoton excess – by better evaluating their already existing data. But ATLAS has "chickened out", the rumor says, and they won't show this result.

This reticence is understandable – it's a big claim, especially if you surpass five sigma. But even five-sigma claims have a chance to be right as well as wrong and people should be aware of that – and I think that they are. To censor your results because you're afraid that the conclusion that your work has forced you to embrace is too "bold" and because you're afraid it could be wrong represents a bias of a sort and I personally find this bias unfortunate.

It's better for others to be informed about all the evidence, even though one has a higher risk that some of the big claims will turn out to be false positives (but lower risk that they will miss true positives). If the experimenters decided about the validity of the emerging hypothesis by their prejudices and feelings ("the cernette just can't exist, can it?"), they wouldn't need the LHC and they could be paid as witches which could be cheaper. But I think it would be less reliable a path to the scientific progress – the progress would probably be zero.

In a talk a few months ago, Nima Arkani-Hamed said that the probability that the cernette exists is about 10%, a high number. My estimate would be higher and perhaps comparable to 50%.

Updates: slides are available for ATLAS as well as CMS. ATLAS says the significance is 3.9 sigma locally, only 2.0 globally. CMS only 2.8-2.9 locally, less than 1 sigma globally. A combo gives about 3.4 sigma. Both detectors have increased the local significance – and, paradoxically, decreased the global one. And they found some more weak evidence even in the 2012 data so the plot has thickened a little bit.

Gravity as the weakest force

By the way, an interesting miniworkshop Weak Gravity Conjecture and Cosmology is taking place in Madrid today and tomorrow. The talks are being streamed. It's cool that cosmologists analyze proposed general principles that could influence the direction that science takes. And I am of course about one-quarter-honored by that event, too.

Note that we didn't mean cosmology to be the primary motivation but already when our paper was being written, similar observations about cosmology – and inflation – were largely known. By stringy T-duality or less sharp tricks (dimensional reduction of a sort), the claim that "gravity is the weakest force among the elementary particles" may be argued to be equivalent to the claim that "large field inflation cannot be consistent" (well, at least at the level of parametric estimates, there are many loopholes). While I was excited about BICEP2's claimed detection of the tensor perturbations, I as a theorist tend to assume that the tensor perturbations are insanely weak and basically undetectable.

But there are other possible implications of WGC to cosmology. You may watch the talks.