Physics

The mass of the Higgs boson reported at the Large Hadron Collider in 2012, 125 GeV, looked lighter than the expected energy scale, about 1 TeV, say researchers at Aalto University in Finland, who now propose that there is more than one Higgs boson, and they are much heavier than the consensus.

New CERN experiments at 0.75 TeV suggested evidence of a second Higgs in that region and some scrambled to embrace it. Dr. Tommaso Dorigo of Science 2.0 dismissed it as a spurious 750 GeV signal observed by ATLAS and CMS in their mass spectra of photon pairs, no different than other spurious signals that ATLAS and CMS have seen in the past.
As a follow-up of yesterday's post on the very opportune Pomeranchuk prize given to Stan Brodsky, I would like to report here on a funny anecdote Stan related to me today. The anecdote is interesting to all of us who believe the world of physics research is fully trans-national - well, it is, but there is apparently some more work to do to improve the situation further.
I was quite happy to hear today that Stan Brodsky, a professor of particle physics and astrophysics at Stanford University, has received together with Victor Fadin the 2015 Pomeranchuk Prize from the Russian Institute for Theoretical and Experimental Physics (ITEP) of Moscow. Stan is a great guy and his contributions to QCD  are of wide range. 

Two weeks have passed since the CERN Jamboree of December 15th, which will be always remembered for the spurious 750 GeV signal observed by ATLAS and CMS in their mass spectra of photon pairs. It is unfortunate, as dozens of very important new measurements and search results were shown by the experiments on that occasion, but they all got overshadowed by a fluctuation.
Here is my holiday card for 2015, a tradition of mine going back to 1990.  Enjoy.






On the back...



I also include a summary of the year.  Here is the stuff on my research efforts:

Hello:

[The article below is courtesy  Eilam Gross. Eilam is a physicist from the ATLAS experiment and has been convener of the Higgs group there. I am very happy to host a guest post from him on the exciting topic below...]


Marumi Kado started his talk by saying he will only present new results based on the full 2015 13 TeV pp collision dataset.
For Run 2 there have been a large number of improvements to the detector.

Also the trigger has been improved, with a new central trigger processor. Reconstruction software also was improved significantly. 

Marumi spent a long time describing the retuning of the detector and the performance in reconstruction of impact parameters, physics objects, and the like. The physics modellinghas been verified in several control samples of dibosons, top pairs, etcetera.

Marumi shows that the Higgs signals in ATLAS are wanting. 0.7 sigma observed in 4-lepton mode, expected 2.8 sigma. Similar story in diphotons.
Jim Olsen is giving the CMS talk on 13 TeV results. CMS recorded 90% of the 4 inverse femtobarns delivered by the LHC, but only 2.8/fb were taken with the magnet at 3.8 Tesla (for the rest of the time the magnet was off due to a problem with the helium purity).
A plot of the dimuon invariant mass of 60,000,000 events collected by dimuon triggers was shown, which is a pleasure to watch. I will attach it here later.

CMS has 18 new searches for beyond-the-standard model effects. For objects with masses above 1 TeV the sensitivity of 2.2/fb of analyzed data may be larger than the sensitivity of 2012 data.

The diboson bump at 2 TeV is almost completely ruled out; so is the edge signal of SUSY that was seen in run 1 (a 2.6 sigma excess back then).

As most of you already know, today at 3PM two back-to-back talks by Jim Olsen (CMS) and Marumi Kado (ATLAS) at CERN will disclose the latest results of physics analyses performed on 13 TeV proton-proton collisions recorded this year by the two experiments. (To follow the talks see here).

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