Last week I attended the Eighth Harvard-Smithsonian Conference on Theoretical Astrophysics, entitled “Debates on the Nature of Dark Matter”, which brought together leading figures in astronomy, astrophysics, cosmology and particle physics. Although there wasn’t much that was particularly new, it was a very useful conference for taking stock of where we are. I thought I’d bring you a few selected highlights that particularly caught my eye.
The rumors about the Higgs particle at the Large Hadron Collider [LHC] have begun again, and since that’s all anyone is going to want to talk about until we actually get the news for real, at the ICHEP conference in Melbourne in a couple of weeks, we may as well get started. [This is especially … Read more
Posts have been a bit rare due to overwork and travel, but I have a few things to say about the search for the Standard Model Higgs particle (the simplest possible form of the Higgs) at CMS, one of the two major Large Hadron Collider [LHC] experiments. Last week I focused on the big news from the Tevatron and from ATLAS (the other major LHC experiment involved in the Higgs search), because the changes in their results were much larger than those from CMS, partly because CMS had already analyzed all their data for all of the different types of Higgs decays, and also the changes at CMS were, on the face of it, rather small.
However, the results at CMS have a significant effect on the overall picture, both negative and positive, and so deserve comment.
The main change from the December and January CMS two-photon Higgs search is that a more powerful and sophisticated technique has been applied to the same data. The results are roughly consistent with the previous search, but show important differences (which tells you how sensitive the current evidence is to how you slice the data.) Here are the consequences of the new result compared to the old, illustrated in the two figures late in the post:
Today, we got new information at the Moriond conference on the search for the Higgs particle (in particular, Phase 1 of the search, which involves the search for the simplest possible Higgs particle, called the “Standard Model Higgs”) from the Tevatron and the Large Hadron Collider [LHC], the Tevatron’s successor. With those results in hand, and … Read more
The search for the Higgs particle has been dominated recently by the new kids on the block, the ATLAS and CMS experiments at the Large Hadron Collider [LHC], who benefit from the LHC’s record high energy per collision. But at its predecessor, the now-closed Tevatron, the CDF and DZero experiments still have a few tricks up their sleeves. Though the energy per collision in recent years at the Tevatron was 3.5 times smaller than was the LHC’s in 2011, CDF and DZero have twice as much data as do ATLAS and CMS right now. And there’s one more thing going for them. In contrast to the LHC, where protons collide with protons, at the Tevatron protons collided with antiprotons. That gives the Tevatron a little edge in one particular search mode for the Higgs. It won’t be enough to beat the LHC at the game for which it was designed, but it’s enough that the Tevatron experiments can at least play. And we’ll see results from the two experiments tomorrow (Wednesday) — with a preview already publicly available, as you’ll see below.
We’ve been expecting this: the ATLAS and CMS experiments at the Large Hadron Collider [LHC]
are going to be making public shortly have made public the publishable form of their papers (preprints, which one submits to a journal for the purpose of peer review) on the search for the Standard Model Higgs particle (the simplest possible type of Higgs particle.) These papers are based on the preliminary results that we heard about on December 13th, which I discussed in some detail here. Here is a page where you can get all the ATLAS and CMS papers. I’ll report after reading them. There will probably be I see no major changes from December 13th, though there will be are interesting minor ones. That’s because the measurements are very sensitive and precise. [UPDATE 1: The two-photon measurement from CMS includes something new: they separate the small number of events that have two additional jets out from the rest. This subset of the data is sensitive to both the g g –> Higgs and q q –> q q Higgs production processes, and it shows an excess at 124 GeV/c2, consistent with the existence of a Standard Model-like Higgs at that mass.] [UPDATE 2: See below]
Since we’re now approaching the time when the preliminary results from December on the search for the Higgs particle at the Large Hadron Collider (LHC) will be presented in final form, possibly with small but important adjustments, and since there will be additional results based on the fall’s data in the next few weeks, it would … Read more
On Tuesday, the New York Times had an article on the Higgs particle search. Not bad, and does quote relevant people, but just a little bit thin on content. If you want some actual content, try my article on the hints of the Higgs particle. Also, the article falls into the common mistake of not … Read more