Why A Lightweight Higgs Particle is a Sensitive Creature — Part 1

In a post from January 27, 2012, concerning the possibility that the Higgs particle might have exotic decays (i.e. decays of a sort not expected if the Higgs is of the “ simplest [i.e. “Standard Model”] type), I described a lightweight Higgs particle as a sensitive creature.  We might think of it as the canary in the accelerator tunnel, easily affected by new … Read more

Exotic Decays of the Higgs: A High Priority for 2012

2012 may well turn out to be The Year of The Higgs.  Right now we have very little knowledge about this particle, but that may change dramatically over the year. As I described in my previous post, we’re coming toward the end of Phase 1 of the Higgs search (where the ATLAS and CMS experiments at the Large Hadron Collider [LHC] search for the simplest possible form of the Higgs particle, the Standard Model Higgs, or SM Higgs for short.) And we’re also starting up Phase 2 of the Higgs search. As discussed in my Cosmic Variance guest post, and in more detail in my most recent post, if a particle resembling the SM Higgs is found, Phase 2 involves checking its details and determining as well as possible whether it is or isn’t precisely what is predicted by the Standard Model. If no such particle is found, Phase 2 involves searching widely for the many other types of Higgs particles that nature might or might not possess. Fortunately, despite these apparently divergent aims, the two possible branches of Phase 2 involve asking some of the same experimental questions (see Figure 3 of the most recent post), and so we can start on Phase 2 before even finishing Phase 1. And that is happening now.

One of the things that has to be done in Phase 2 is to search for decays of the Higgs particle that are not among the decays predicted to occur in the Standard Model.  [“Decay” = “a disintegration of one particle into two or more”. Click here for an introduction.]  Such “exotic” decays are thought of as particularly plausible, because a lightweight Higgs (below about 150 GeV/c2 or so) is a very sensitive creature. It is very easy for new particles and/or forces to alter the Higgs’ properties, perhaps causing changes in how (or how often) it is produced, and to what (and with what probability) it may decay.  As shown in a large number of papers, written by  quite a variety of particle physics theorists, there are many, many types of possible exotic decays, and they can arise for many reasons.  If you’re curious what kind of exotic decays might occur, I gave a few examples in my now somewhat out-of-date analysis of what the summer’s Higgs searches imply. The basic logic of how unusual Higgs decays might arise is still correct in the cases described, but there are many, many more possibilities too. I’ll have to write a long article about the options in the coming month or so.

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Reviewing the Search for the Higgs

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

Why Extra Dimensions Lead to Kaluza-Klein Particles — Part 2 (of 2)

The end of the story: if you’ve read through all the articles linked from Monday’s post — which explain why extra dimensions manifest themselves through heavier versions of known particles, called Kaluza-Klein (KK) partners — you can now read the punch-line in today’s article: why, instead of there being a KK partner for every possible mass, as Monday’s … Read more

Why Extra Dimensions Lead to Kaluza-Klein Partner Particles – Part 1

Ok, the answer you’ve all been waiting for — the first half of it, anyway.   Even though it is not the full story yet, you’ll find it is both self-contained and instructive. Those of you who have been following my recent series of articles on extra dimensions of space —  which include some articles on … Read more

The Smoking Gun for Extra Dimensions

We’re in the midst of a turning point in scientific history, with many different types of discoveries reported of planets around other stars. It certainly is starting to appear that planets around stars are the rule, not the exception.  This is an enormously important development in our understanding of our universe… so a hearty congratulations … Read more

Another Type of Extra Dimension

I’ve updated the article on extra dimensions that I announced last week.  In the original version of the article, I gave you one example of an extra dimension; now I’ve extended it to include another example, of a very different type.   You can find all the new stuff by scanning down the article until … Read more

A Bit More About “Extra Dimensions”

A while ago I was writing a sequence of articles — interrupted for some weeks by all the hullabaloo over Higgs particles and all the noise about neutrinos — concerning the possibility that the world has more than the three spatial dimensions that are obvious to us.  These “extra” dimensions seem to be very confusing … Read more