http://home.cern/about/updates/2015/09/atlas-and-cms-experiments-shed-light-higgs-properties

OK, slightly old news, but I find it shocking in that scientists from the CMS and ATLAS experiments at the LHC have actually collaborated! At the announcement of the Higgs, and before, no scientific paper had been published that combined the results of the two instruments. The two instruments measure the same things, to almost identical accuracy. So putting the two independent results together improves the statistical significance enormously. Anyway, back to the news item.

“The Brout-Englert-Higgs mechanism gives mass to elementary particles. ATLAS and CMS Collaborations present for the first time combined measurements of many of its properties, at the third annual Large Hadron Collider Physics Conference (LHCP 2015). ATLAS and CMS together draw the sharpest picture yet of this novel boson. All of the measured properties are in agreement with the predictions of the Standard Model (see following picture, in the standard model kappa _v and kappa _f are both equal to 1.). There are different ways to produce a Higgs boson, and different ways for a Higgs boson to decay to other particles. For example, according to the Standard Model, the theory that describes best forces and particles, when a Higgs boson is produced, it should decay immediately in about 58% of cases into a bottom quark and a bottom antiquark.”

mollwollfumble said:

http://home.cern/about/updates/2015/09/atlas-and-cms-experiments-shed-light-higgs-properties

OK, slightly old news, but I find it shocking in that scientists from the CMS and ATLAS experiments at the LHC have actually collaborated! At the announcement of the Higgs, and before, no scientific paper had been published that combined the results of the two instruments. The two instruments measure the same things, to almost identical accuracy. So putting the two independent results together improves the statistical significance enormously. Anyway, back to the news item.

“The Brout-Englert-Higgs mechanism gives mass to elementary particles. ATLAS and CMS Collaborations present for the first time combined measurements of many of its properties, at the third annual Large Hadron Collider Physics Conference (LHCP 2015). ATLAS and CMS together draw the sharpest picture yet of this novel boson. All of the measured properties are in agreement with the predictions of the Standard Model (see following picture, in the standard model kappa _v and kappa _f are both equal to 1.). There are different ways to produce a Higgs boson, and different ways for a Higgs boson to decay to other particles. For example, according to the Standard Model, the theory that describes best forces and particles, when a Higgs boson is produced, it should decay immediately in about 58% of cases into a bottom quark and a bottom antiquark.”

The technical article is http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.114.191803
(Click on Albert Einstein’s head if the link asks you to).
A sign of the times. The article is 7 pages long. The list of authors and their affiliations is 14 pages long.

Mass of the Higgs boson is 125.09 +-0.21 (statistical) +-0.11 (systematic) GeV.

The two main decay mechanisms are decay to 4 gamma rays, and decay to two Z particles (carrier of the weak force) that together decay to four leptons.

The technical paper doesn’t really contain much information, being solely a summary of how errors in calculating the mass of the Higgs were minimised. Nothing there about branching ratios or coupling constants.

Very Interesting.

Especially since I am currently reading Fantastic Realities by Frank Wilczeck, which has a lot about Higgs particles, and how they might appear when the LHC came into operation (written late 1990’s and early 2000’s).

One thing he says quite a lot is that there might be more than one Higgs. Any news on that?

Tangentially related to the thread (but I didn’t think it worth starting a new one), I’ve just been exploring the online 24/7 shift log for the LHCb control center.

Hopefully others here find it interesting.

http://lblogbook.cern.ch/Shift/

esselte said:

Tangentially related to the thread (but I didn’t think it worth starting a new one), I’ve just been exploring the online 24/7 shift log for the LHCb control center.

Hopefully others here find it interesting.

http://lblogbook.cern.ch/Shift/

Thanks for that. Rather a shocking number of minor problems that they’re having, wouldn’t you say? Four pages of operating notes just from 1 Nov 2015.

For CERN on twitter see https://twitter.com/CERN
eg. contains links to
http://home.cern/about/updates/2015/10/lhc-luminosity-upgrade-project-moving-next-phase
“This week more than 230 scientists and engineers from around the world met at CERN to discuss a major upgrade to the Large Hadron Collider (LHC) that will increase its discovery potential from 2025. The High-Luminosity LHC will increase the luminosity by a factor of 10. The High-Luminosity LHC will produce 15 million Higgs bosons per year compared to the 1.2 million in total created at the LHC between 2011 and 2012.”

and
CERN Courier November 202015 (Volume 55 Issue 8).pdf
The CERN Courier is well worth browsing through, includes latest results from LHC, other CERN equipment such as the Daya Bay Reactor Neutrino Experiment, the Borexino detection of Neutrinos produced by the Earth, the new CALorimetric Electron Telescope on the ISS. As well as a general science watch, new furthest galaxy, libration of Enceladus, “A stable atomic narrow-band X-ray laser has reached the shortest wavelength ever: 1.5 Å, about 10 times shorter than had been previously achieved.” Also includes an article on the continuing search for new physics beyond the Standard Model.

> One thing he says quite a lot is that there might be more than one Higgs. Any news on that?

Um, I was present at the conference when the Higgs was announced. Trying to dredge memory.

First of all, multiple Higgs particles come out of both Technicolor and Supersymmetry theories, but both Technicolor and Supersymmetry were shot down in flames. Secondly, multiple Higgs is predicted if the Higgs is a composite rather than elementary particle. My memory here is more hazy, but the evidence certainly didn’t support the theory that it is a composite particle. Thirdly,. if there were multiple Higgs particles, then the one that has been found is certainly the lightest of them, from vague memory if there were multiple Higgs particles then the one that we found ought to have been lighter? Fourthly, multiple Higgs would have some influence on the metastability of the Universe, make it worse?