Questions and Answers About Dark Matter post-LUX

Since the mainstream news media, in their reporting on the new result from the LUX experiment I wrote about Wednesday, insists on confusing the public with their articles and headlines, I thought I’d better write a short post reminding my readers what we do and don’t know about dark matter. Do we know dark matter … Read more

Some Weird Twists and Turns

In my last post, I promised you some comments on a couple of other news stories you may have seen.  Promise kept! see below.

But before I go there, I should mention (after questions from readers) an important distinction.  Wednesday’s post was about the simple process by which a Bs meson (a hadron containing a bottom quark and a down[typo] strange anti-quark, or vice versa, along with the usual crowd of gluons and quark/antiquark pairs) decays to a muon and an anti-muon.  The data currently shows nothing out of the ordinary there.  This is not to be confused with another story, loosely related but with crucially different details. There are some apparent discrepancies (as much as 3.7 standard deviations, but only 2.8 after accounting for the look-elsewhere effect) cropping up in details of the intricate process by which a Bd meson (a hadron containing a bottom quark and a down antiquark, or vice versa, plus the usual crowd) decays to a muon, an anti-muon, and a spin-one Kaon (a hadron containing a strange quark and a down anti-quark, or vice versa, plus the usual crowd). The measurements made by the LHCb experiment at the Large Hadron Collider disagree, in some but not all features, with the (technically difficult) predictions made using the Standard Model (the equations used to describe the known particles and forces.)

Don't confuse these two processes!  (Top) The process B_s --> muon + anti-muon, covered in Wednesday's post, agrees with Standard Model predictions.   (Bottom) The process B_d --> muon + anti-muon + K* is claimed to deviate by nearly 3 standard deviations from the Standard Model, but (as far as I am aware) the prediction and associated claim has not yet been verified by multiple groups of people, nor has the measurement been repeated.
Don’t confuse these two processes! (Top) The process B_s –> muon + anti-muon, covered in Wednesday’s post, agrees with Standard Model predictions. (Bottom) The process B_d –> muon + anti-muon + K* is claimed to deviate by nearly 3 standard deviations from the Standard Model, but (as far as I am aware) the prediction and associated claim has not yet been verified by multiple groups of people, nor has the measurement been repeated.

A few theorists have even gone so far as to claim this discrepancy is clearly a new phenomenon — the end of the Standard Model’s hegemony — and have gotten some press people to write (very poorly and inaccurately) about their claim.  Well, aside from the fact that every year we see several 3 standard deviation discrepancies turn out to be nothing, let’s remember to be cautious when a few scientists try to convince journalists before they’ve convinced their colleagues… (remember this example that went nowhere? …) And in this case we have them serving as judge and jury as well as press office: these same theorists did the calculation which disagrees with the data.  So maybe the Standard Model is wrong, or maybe their calculation is wrong.  In any case, you certainly musn’t believe the news article as currently written, because it has so many misleading statements and overstatements as to be completely beyond repair. [For one thing, it’s a case study in how to misuse the word “prove”.] I’ll try to get you the real story, but I have to study the data and the various Standard Model predictions more carefully first before I can do that with complete confidence.

Ok, back to the promised comments: on twists and turns for neutrinos and for muons…  

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A Couple of Rare Events

Did you know that another name for Minneapolis, Minnesota is “Snowmass”?  Just ask a large number of my colleagues, who are in the midst of a once-every-few-years exercise aimed at figuring out what should be the direction of the U.S. particle physics program.  I quote:

  • The American Physical Society’s Division of Particles and Fields is pursuing a long-term planning exercise for the high-energy physics community. Its goal is to develop the community’s long-term physics aspirations. Its narrative will communicate the opportunities for discovery in high-energy physics to the broader scientific community and to the government.

They are doing so in perhaps the worst of times, when political attacks on science are growing, government cuts to science research are severe, budgets to fund the research programs of particle physicists like me have been chopped by jaw-dropping amounts (think 25% or worse, from last year’s budget to this year’s — you can thank the sequester).. and all this at a moment when the data from the Large Hadron Collider and other experiments are not yet able to point us in an obvious direction for our future research program.  Intelligent particle physicists disagree on what to do next, there’s no easy way to come to consensus, and in any case Congress is likely to ignore anything we suggest.  But at least I hear Minneapolis is lovely in July and August!  This is the first Snowmass workshop that I have missed in a very long time, especially embarrassing since my Ph.D. thesis advisor is one of the conveners.  What can I say?  I wish my colleagues well…!

Meanwhile, I’d like to comment briefly on a few particle physics stories that you’ve perhaps seen in the press over recent days. I’ll cover one of them today — a measurement of a rare process which has now been officially “discovered”, though evidence for it was quite strong already last fall — and address a couple of others later in the week.  After that I’ll tell you about a couple of other stories that haven’t made the popular press…

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Courses, Forces, and (w)Einstein

This week and next, I’m very busy preparing and delivering a new class (four lectures, 1.5 hours each), for a non-technical audience, on the importance of and the discovery of the Higgs particle.  I’ll be giving it in Western Massachusetts (my old stomping grounds).  If it goes well I may try to give these lectures elsewhere (and please let me know if you know of an institution that might be interested to host them.)   Teaching a new class for a non-technical audience requires a lot of concentration, so I probably won’t get too much writing in over that period.

Still, as many of you requested, I do hope soon to follow up last week’s article (on how particle physicists talk about the strength of the different forces) with an article explaining how both particles and forces arise from fields — a topic I already addressed to some extent in this article, which you may find useful.

Now — a few words on the flap over the suggestion that math Ph.D. and finance expert Eric Weinstein, in his mid-40s, may be the new Albert Einstein.  I’ve kept my mouth shut about this because, simply, how can I comment usefully on something I know absolutely nothing about?  (Admittedly, the modern media, blogosphere and Twitter seem to encourage people to make such comments. Not On This Blog.) There’s no scientific paper for me to read.  There’s no technical scientific talk for me to listen to.  I know nothing about this person’s research.  All I know so far is hearsay.  That’s all almost anyone knows, except for a few of my colleagues at Oxford — trustworthy and experienced physicists, who sound quite skeptical, and certainly asked questions that Weinstein couldn’t answer... which doesn’t mean Weinstein is necessarily wrong, only that his theory clearly isn’t finished yet.  (However, I must admit my expert eye is worried that he didn’t have ready answers to such basic questions.)

What I do know is that the probability that Weinstein is the new Einstein is very low.  Why?  Because I do know a lot about how very smart people with very good ideas fail to be Einstein.  It’s not because they’re dumb or foolish.

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Not As Painless As They’d Have You Believe

I’m still seeing articles in the news media (here’s one) that say that the majority of Americans think the recent sequester in the US federal budget isn’t affecting them. These articles implicitly suggest that maybe the sequester’s across-the-board cuts aren’t really doing any serious damage. Well, talk to scientists, and to research universities and government … Read more

Cosmic Conflation: The Higgs, The Inflaton, and Spin

Over the past week or so, there has been unnecessary confusion created about whether or not there’s some relationship between (a) the Higgs particle, recently discovered at the Large Hadron Collider, and (b) the Big Bang, perhaps specifically having to do with the period of “Cosmic Inflation” which is believed by many scientists to explain why the universe is so uniform, relatively speaking. This blurring of the lines between logically separate subjects — let’s call it “Cosmic Conflation” — makes it harder for the public to understand the science, and I don’t think it serves society well.

For the current round of confusion, we may thank professor Michio Kaku, and before him professor Leon Lederman (who may or may not have invented the term “God Particle” but blames it on his publisher), helpfully carried into the wider world by various reporters, as Sean Carroll observed here.

[Aside: in this post I’ll be writing about the Higgs field and the Higgs particle. To learn about the relationship between the field and the particle, you can click here, here, here, or here (listed from shortest to most detailed).]

Let’s start with the bottom line. At the present time, there is no established connection, direct or indirect, between (a) the Higgs field and its particle, on the one hand, and (b) cosmic inflation and the Big Bang on the other hand. Period. Any such connection is highly speculative — not crazy to think about, but without current support from data. Yes, the Higgs field, responsible for the mass of many elementary particles, and without which you and I wouldn’t be here, is a spin-zero field (which means the Higgs particle has zero spin). And yes, the “inflaton field” (the name given to the hypothetical field that, by giving the universe a lot of extra “dark energy” in the early universe, is supposed to have caused the universe to expand at a spectacular rate) is also probably a spin-zero field (in which case the inflaton particle also has zero spin). Well, fish and whales both have tails, and both swim in the sea; yet that doesn’t make them closely related.

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Why the Higgs Matters, In A Few Sentences

One of the big challenges facing journalists writing about science is to summarize a scientific subject accurately, clearly and succinctly. Sometimes one of the three requirements is sacrificed, and sadly, it is often the first one.

So here is my latest (but surely not last) attempt at an accurate, succinct, and maybe even clear summary of why the Higgs business matters so much.

`True’ Statements about the Higgs

True means “as true as anything compressed into four sentences can possibly be” — i.e., very close to true.  For those who want to know where I’m cutting important corners, a list of caveats will follow at the end of the article.

  • Our very existence depends upon the Higgs field, which pervades the universe and gives elementary particles, including electrons, their masses.  Without mass, electrons could not form atoms, the building blocks of our bodies and of all ordinary matter.
  • Last July’s discovery of the Higgs particle is exciting because it confirms that the Higgs field really exists.  Scientists hope to learn much more about this still-mysterious field through further study of the Higgs particle.

Is that so bad? These lines are almost 100% accurate… I’m sure an experienced journalist can cut and adjust and amend them to make them sound better and more exciting, but are they really too long and unclear to be useable?

Some False Statements about the Higgs

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Can You Find The Higgs-Like Particle?

Ok, everyone; by now you’ve all learned that the ATLAS experiment at the Large Hadron Collider [LHC] announced recently their measurement of the mass of the Higgs particle, in its decay to two photons, is at 126.6±0.3±0.7 GeV/c²; and meanwhile they measure the mass for apparently the same particle, in its decay to two lepton/anti-lepton pairs, … Read more

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