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Particle physics question for Kelsey or anyone else that can answer.... Answered

I am finishing up the book I am reading on Dark matter, and Mr. Krauss mentions "spontaneous symmetry breaking" (not a hard concept) creating or producing  spin-0 particles or scaler particles  (Higgs Boson?).   My question is, have any of these particles, as yet, been observed?  The book I am reading is slighty dated, and so I am not even sure it is up to date on the vacuum energy  postion towards dark matter and a flat universe.


Yes and no. The Higgs boson (spin-0, hence "scalar" as opposed to "vector", not to be confused with "scaler") has not been observed, though the mass range where we expect to find it has been narrowed recently by Fermilab results.

Spontaneous symmetry breaking, and the particles which result from it, have certainly been observed -- the massless photon and the massive weak vector bosons (W+, W-, Z0). In the Standard Model, the unified electroweak interaction is described by an SU(2)×U(1) symmetry, in which four massless vector bosons interact, a triplet of W's (0, -, and +) from the SU(2) weak isospin group, and a neutral B from the U(1) hypercharge group.

Spontaneous symmetry breaking, in a manner similar to the Zeeman splitting of atomic energy levels, forces the degenerate (both massless) pair W0 and B to split, one staying massless (the photon) and the other acquiring a large (and predicted!) mass around 90 GeV (the Z0). The same symmetry breaking gives mass to the charged W's, around 83 GeV.

All of this was predicted by Weinberg, Salam, and Glashow in the late 1960s, nearly two decades before the Z0 and W's were experimentally observed (by the UA1 and UA2 collaborations at CERN).

Thank you Kelseymh for that, although I will need to look up a few terms, as the book had not dealt with them, I grasp the overall concept and appreciate your taking time to explain it to me. Helping me bring the book a little more up to date.


The Wikipedia articles on physics are a good place to start. Use any of the keywords from my post and that should get you started.

Well, I finally knuckled under and finished Krauss' book Quintessence: The mystery of the missing mass of the universe.

I must say, either Krauss has a hidden talent for making the weird, and unconventional seem normal and understandable, or I have a penchent for this subject  LOL

Anyways, had I waited to finish the book before asking the questions, I would have gotten my answer, albeit in a bit less technical explanation ;-)   Not that I am faulting yours,  because his was much more wordy (took up the last 3 chapters and the epilog and the appendix  (yeah, it interested me that much that I read them too).  

I can understand one's wanting to get into said field of particle physics....it is indeed fascinating all around. 

Thank you for your patience with my former ignorance on the subject (not that I am now any kind of expert, but I am discussing the subject on a science forum in FB with a fellow that can not understand the difference between weight and mass *sigh*  (I do believe my "example" of weight being dependant on the gravitational field one is in (say on the moon, the earth or on Jupiter)  helped him sort it out however. 

Thanks again for all your help.

:-D I'm glad you both enjoyed the book and got something out of it. Krauss is an excellent physics writer (and by "excellent" I mean "I agree with his approach" :-), unlike the "ooh aren't we mysterious" Weinbergs and Hawkings...

Indeed, he seems like someone you could have tea with and he'd discuss the subject on what ever level the other person was capable of. Another physicist I'd like to meet ;-)

BTW: I enjoyed reading the book, the other fellow I was chatting with, hasn't a clue, and was just making things up as he went......

Yes, I will have to take this a little more slowly as it a lot more detailed then Krauss gets for the general public. I do have a few more questions for later, if the last part of his book doesn't answer of hint at an answer to them, to fill in or at least point me in the right direction towards my search for, the answers. Thanks again.

Fascinating....the book, near the end deals with symmetries, and left/right handedness problem (and pct) etc. this is all really cool stuff...

For the lay person, is there a cookie analogy to explain this? i.e. if we bombard an oreo cookie with sufficient force to split it, we can observe how the cookie crumbles and the resultant particulates?

No - the scientists eat them within fractions of a nanosecond and they disappear before they can be observed.

Are you theorizing the existence of dark matter chocolate milk to counterbalance the effects of the creamy white center?

2 days and you didn't mention the nuts you were going to....LOL

Snickers? Mounds !

Hey ! I've been busy trying to figure out what dark matter is, and building my 3 way light and shadow display case......

Almond Joy? No, we don't speak of such things in mixed company.....Butterfingers? Well, I don't drop things ALL the time.....still waiting on my special LEDs *sigh*

" to counterbalance the effects of the creamy white center? "

Oh you mean the Milky way?

Hmmm, but I am a lay person.....anyways, as far as spontaneous symmetry breaking is concerned, on it's simplest level think about how all the threads of a shirt weave go in either one direction or another, if a "snag" occurrs, where a thread or threads "spontaneously" head in another direction or turn in another fashion, you have spontaneous symmetry breaking (it is no longer symmetrical even though all the forces involved would be expected to keep it so).

I now hope that any inaccuracies in my over simplistic analogy, Kelsey will correct LOL

Here's an even better analogy. Take a sharp pencil, or a heavy nail, and carefully balance it right on the point. Gravity points straight down, and the center of mass is right over the tip (because it's balanced), so the equations are radially symmetric. But when the pencil falls, it picks out some specific direction, which breaks the symmetry.


7 years ago

Im not even in full understanding of HOW dark-matter is
indirectly being mapped...     Alex...

Mostly through "weak lensing." By definition, dark matter interacts through gravity (it was hypothesized in the first place to explain the anomalous rotation curves of galaxies and clusters). As we know from GR, gravity bends (lenses) light.

Strong lensing is what we observe when we see a far distant object aligned with a larger mass in the foreground: the distant object will be "replicated" with multiple, often magnified, images. In the case of perfect alignment, the background object will be distorted into a ring centered on the lensing mass.

Weak lensing is a stastical analysis. If you look at a field of distant galaxies (e.g., the Hubble "deep field"), you'll find that some (many) of them don't have the exact shapes we see in more nearby galaxies. They may be elongated, or banana shaped, and so on. A quantitative analysis of the distortions, in shape, magnitude, and position, can allow you to compute the intervening mass (dark matter) which is casusing them.

Thank you for the comment.
I gather DM is identified by algorithmic calculation of physical observations.


Yes, that's exactly right, and it's been true since Zwicky hypothesized it in the 1930s. That's why there's such interest in having a direct detection, in order to confirm the hypothesis (or show that there's something else going on!).

Interesting man Zwicky he hand-carried the Schmidt observatory lens from Germany and was the first to measure ( calculate )  dark mass.

Do you think DM could one day, be put in a bottle on a shelf like other
elements ??    Alex...

Doubtful. First, its density must be extraordinarily low (something like 10 particles or so per cubic meter), so collecting anything like a macroscopic amount would be "impossible" (read, impractical).

Second, by definition it doesn't interact electromagnetically, so how do you store it? We can store antimatter for minutes at a time, because the charged positrons and antiprotons (and even the overall neutral antihydrogen atoms) respond to electromagnetic fields.

Understanding the words...
Still doesn't help in wrapping ones mind around It.


:-) Yeah, that comes from being in the field for twenty years. I do try to use accurate terminology, so you can do a Wikipedia or Google search and end up with some sensible/useful information.

If you want a more focused discussion, either send a PM (crappy formatting and no quoting, though), or start a thread here. I'm sure Goodhart won't mind a bit :-)

Tis ok, I am one of they weirdo's that likes to read stuff that so many others find either boring or uninteresting. I have a whole other "study" I am doing in the field of genetics that has fascinated me for a number of years now (ever since the beginning of the Human Genome project). :-)