Wednesday, September 12, 2012

PLB publishes Higgs discovery papers

Thanks for all the kind words and advices.

On July 4th, 2012, CERN announced the discovery of a new particle whose properties universally indicated it was the Higgs boson. (Those of us who rationally followed the published results knew that there was a new particle and what its mass was since mid December 2011.) They also promised to send the paper to a classical paper journal at the end of July. That's exactly what happened: ATLAS and CMS submitted their texts to Physics Letters B around July 31st.

Within two weeks, the two papers were accepted and they will appear in the September 17th, 2012 issue of PLB (Volume 716 Issue 1). A cute fact is that this "commercial" (although funded primarily by taxpayers' mandatory contributions to research and education) journal made the papers freely available and they're already out.

So you may open:
Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC (abstract, PDF)

Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC (abstract, PDF)
If the abstract, PDF links don't work, the PDF is available as a link in the upper infobar at the PLB pages and the abstract can be obtained by clicking at "abstract" in the left sidebar.

ATLAS sees a 5.9-sigma-strong signal at\[

m_h = (126.0\pm 0.4\pm 0.4) \GeV

\] The first error is statistical and the second is systematic. CMS' 5.0-sigma-strong signal is at\[

m_h=(125.3 \pm 0.4 \pm 0.5)\GeV.

\] You see that their statistical errors are equal, within the accuracy used to write them down, and their systematic errors differ by 20% only. More importantly, the mean values differ by \(0.7\GeV\) which makes the two collaborations' results, within 1 standard deviation, comfortably compatible with one another – recall that in the past at various points, some people had doubts about the compatibility, I was never among them.

One may combine the two detectors' results and we get something like\[

m_h=(125.7\pm 0.3\pm 0.4)\GeV

\] I chose a number closer to ATLAS because its signal is stronger. The statistical error decreased roughly \(\sqrt{2}\) times but I conservatively decided to keep the systematic error close to the original ones – instead of reducing it \(\sqrt{2}\) times – because some of the sources of the systematic error may be shared by ATLAS and CMS in which case there is no reduction.

If you remember the 3-4-5 Pythagorean triangle, you may see that the total error of the measured Higgs mass remains at \(0.5\GeV\). We're really 90% certain that the Higgs mass is between \(125\) and \(126.5\GeV\).

Back to some sociology. I really think it's helpful that the journals made these important papers free and such decisions should become more common.


  1. And the Intrade Higgs markets just closed, netting TRF readers a healthy profit :)

  2. Too bad it couldn't have been billions! ;-)

  3. Dear Lumo,

    thanks for this nice introduction and the links to the higgs papers :-)

    I hope it is a good sign that you are able to write new articles.

  4. You mean PRL or PLB?

  5. You mean PLB: Phyics Letters B, that's where they have been submitted.

  6. Selective mistake of a mistake :-) fixed. ;-)