Of Particular Significance

Blog – Of Particular Significance

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 article would have naively suggested, there are KK partners only for very specific masses.  Also, you can learn why the pattern of KK partners’ masses, if any were discovered, would reveal the shape, size and number of the extra dimensions.

The next step in the extra dimensions series will be to tell you what we already know from experiments about extra dimensions, and how people are looking for them.  I’ll get to that eventually, maybe next month.

Meanwhile I’m still absorbed in some very pressing work concerning this year’s run of the Large Hadron Collider [LHC], so posts are going to be rare for a bit longer.  But over the coming week or two I do have some more things to tell you about the search for the Higgs particle, and about searches for other speculative phenomena going on at the LHC.

Picture of POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON January 20, 2012

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 how to think about them (including some examples) and newer articles on how extra dimensions might reveal themselves to us — already know that for any type of particle that can travel in one or more extra dimensions that are unknown to us, nature will exhibit heavier versions of this particle, called Kaluza-Klein (KK) partner particles.  But I haven’t yet told you why this is the case.

Today, Step 1: why the KK partner particles exist at all, and why they are heavier than the original one.  But today’s argument is a bit too simple, and only partially correct: it gets the masses of the KK partners wrong.  In Step 2 I’ll fix this problem by adding a little bit of quantum mechanics.

Picture of POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON January 16, 2012

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 to the planet hunters!

I hope there are some good articles out there outlining the diverse array of methods being used in these discoveries; there’s a lot of good physics and astrophysics being exploited.  Since this isn’t my area of expertise I’m inclined for the moment to leave this to others… especially since I have some very urgent research going on, which is why posts have been sparse since the New Year.  (I’ll describe that research later; it’s nothing earth-shaking or exciting, but I feel it is very important for LHC operations in 2012.)  If any readers have found an article of this type, please leave a comment.

Meanwhile I’m continuing to develop the Extra Dimensions series of articles, and I’ve now followed up my examples of extra dimensions with a next installment, a first discussion of what scientists would look for in trying to identify that our world actually has one or more extra dimensions .  The new article describes one of the key clues that would indicate their presence.  But this is far from the end of the story: I owe you more articles, explaining why extra dimensions would generate this clue, outlining how we try to search for this clue experimentally, and mentioning other possible clues that might arise.  All in due course…

Picture of POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON January 13, 2012

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 you find a line in red that says “New additions begin here.”  If you haven’t read about extra dimensions at all, you should read some of the other introductory articles first; you can find links to them at the top of today’s article.

What will come next, perhaps in the coming week, is a discussion of the scientific techniques used to look for signs of extra dimensions.  Later I’ll add another example or two to today’s article.

Picture of POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON January 10, 2012

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 to non-experts, so I’ve been trying to find a way to make them seem a little less strange.  We’ll see if I’ve succeeded.  Building on my articles describing some types of worlds of 1 spatial dimension and of 2 spatial dimensions, I’ve now written an article giving one type of example of an “extra” dimension.   Other articles to follow over coming weeks will provide other examples of extra dimensions, as well as an attempt to explain how scientists can potentially look for evidence of an extra dimension.

Picture of POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON January 6, 2012

Well, 2011 was certainly an interesting and exciting year for particle physics. And 2012 promises to be even better.

LHC and the Higgs search

At the Large Hadron Collider [LHC], the accelerator physics team did a fantastic job of assuring the collider worked effectively, and provided significantly more proton-proton collisions than were originally expected. Meanwhile the experimental teams found clever ways to dig more information out of the collision data than was initially anticipated. And thanks to this, the search for the Higgs particle (or Higgs particles, or whatever replaces the Higgs particle) is  most of the way through Phase 1 — the search for the simplest possible form of Higgs particle, known as the “Standard Model Higgs”. We started 2011 knowing that the mass of the Standard Model Higgs particle might lie almost anywhere between 115 GeV/c2 and 800 GeV/c2 (where GeV, a measure of energy, is described here, and c is the speed of light, as in E = m c2.) The exception was a narrow gap around 160-170, excluded by the Tevatron experiments.  We ended the year, thanks to the great work at the ATLAS and CMS experiments, with the Standard Model Higgs excluded everywhere except above 600 GeV/c2 (where it is disfavored for other reasons) and in a window between 115 and about 128 GeV/c2. Even more exciting, there is a serious hint of a Higgs particle signal at around 124–126 GeV/c2. (more…)

Picture of POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON January 2, 2012

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