As part of the CERN Council activities this week, there will be a session held with a live webcast tomorrow on Status of the LHC and Experiments. I’m hearing that there will be news about the Higgs from ATLAS: new results for the high statistics gamma-gamma and ZZ channels. These were expected for HCP2012 last month but not ready then.
If you can’t watch the CERN talks, the KITP tomorrow at 11:15 am has scheduled a talk on “New (!!) ATLAS Diphoton and ZZ Results”.
Update: This promises to be quite interesting. ATLAS is seeing a 3 sigma difference between the Higgs mass seen in the gamma-gamma channel and in the ZZ channel. They’ve been trying hard to check all possible systematic effects that could explain this, but it won’t go away, so they’ve decided to go ahead and report the results tomorrow. Probably nothing, but if CMS is seeing anything similar and it is still there in their analysis of the rest of this year’s data, that would be huge. I don’t know of any sensible model that would lead to a real effect like this, but who knows…
Update: The new ATLAS results don’t seem to be available online anywhere, but Jester and Matt Strassler report the details from today’s webcast. ATLAS has the Higgs at 126.6 GeV in gamma-gamma, at 123.5 in ZZ, difference is 2.7 sigma. The ZZ signal strength is right in line with SM predictions, the gamma-gamma signal strength is about 2 sigma high. Odd parity or spin two strongly disfavored.
Nothing news about this from CMS. What they have released doesn’t at all confirm the ATLAS mass difference, with them seeing the ZZ peak at 126.2 +/- .6 GeV, gamma gamma around 125. So their masses are compatible and in the middle between the two extreme ATLAS values.
All in all, still looking like a garden-variety SM Higgs. Next update with lots more data likely to be in March at Moriond.
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Can you tell me if this scenario is remotely plausible:
1) Astrophysicists are seeing evidence of a dark matter particle at 130 GeV, which is close to 125 GeV.
2) It’s very rarely produced in the LHC, it hasn’t been explicitly caught because there’s no search algorithm that would find it.
3) When it is created, it decays into photons.
4) 130 GeV is close to 125 Gev, and the resolution is not sharp, so it looks like a single bump at 127 GeV with higher-than-expected normalization.
You need someone more expert on dark matter than me to address that. If it is sensible there should be half a dozen preprints on the arXiv about it tomorrow night…
if the 130 GeV particle decays to two photons, it can not be dark matter, since the latter must be stable on cosmological timescales.
Peter—It was rumored last month that ATLAS is seeing the ZZ signal at about 123 and the gamma gamma at 126. But CMS clearly shows ZZ at 126, with over 4 sigma. So they can’t agree. Still, wouldn’t it be fun if CMS sees gamma gamma at 123 🙂
The 130-135 GeV Fermi line is still controversial, and possibly spurious since it’s also seen in the Earth limb data. cf http://fermi.gsfc.nasa.gov/science/mtgs/symposia/2012/program/fri/AAlbert.pdf
I’m no particle physicist, but from what I understand, the putative DM particle at 130 (actually 135 based on updated official Fermi analysis) annihilates to two photons, not decays. The particle itself is (presumably) stable.
Peter, are you saying the cross-section is larger by 3sigma, or that the best fit higgs values are different in the 2channels? What are the central values of each channel? It seems crazy to have bumps at different energies in different channels. Something seems fishy…
The best fit mass values differ by 3 sigma in the two channels, and the numbers Marc mentions above are about right.
Not as hard to believe as superluminal neutrinos, but still seems almost certain to be something that will go away.
Could they be seeing different higgs in each channel? multiple higgs?
FTL neutrinos reloaded? i hope they go “public” with less hype surrounding it.
What are the models that might produce something like this?
Nabil—you could horrendously fine-tune a two-Higgs doublet model (with some additional particles, perhaps) to explain a gam gam peak at 126 and a ZZ peak at 123. However, CMS sees ZZ at 126, so the experiments themselves are contradictory (if you take the < 3 sigma effect seriously). Of course, if the Higgs mass itself gradually changes as one gets closer to Paris……
Yes marc, your idea that the higgs eats crossaints as it get closer to paris is currently the leading explanation
Marc: sounds like Henri IV was more correct than we knew.