Sitting here on graveyard shift monitoring an experiment makes for a decent opportunity to start this thread. I’ve thought about doing one of these “Ask the…” threads in the past, but I’ve never had the time that such a thread might require. However, I can’t get any useful work done on the tail end of shift anyway (too tired), so I figured why not now?
So, let 'er rip! (I’m half expecting crickets, though.)
What’s the next step if the LHC doesn’t find evidence of the Higgs Boson?
First of all - thanks!
Secondly - what can you tell us about what you are working on?
Which books would you recommend for civilians to get to know your subject(s) better? Either from a generalist viewpoint or more specific to the area of research you are focused on?
What are the top few things being worked on in your field and what’s your take from an Insider’s perspective - any big developments seemingly imminent on the horizon?
What’s one thing that most folks don’t realize about working particle physicists?
Where do you guys think you rank in the pecking order of geek-cool, relative to billionaire software/internet developers, astronomers, and other similar folks?
I’m exhausted and finally heading to bed, but I look forward to answering these (and any new questions) after I get some sleep.
Back in a few hours…
What exactly is a “magnetic bottle” ?
Where are you working, and on what experiment?
I’d love to ask you something more sophistcated, but I just confused the heck out of my feeble brain trying to understand the “double-slit” electron as particle and wave experiment …
Oh, sure - tease us and then walk away…
Someone left a box on my desk yesterday that’s hooked up to a canister of cyanide. I keep hearing meowing from inside it, but when I shake it, all I get is a “thump thump” sound and nothing seems to be moving. I considered slicing two slits into the side of it and shining a light in there to see what’s what. But ultimately I decided not to risk it. I’ve attached a bomb to the side of the box, which I’m hopeful will kill anything not already dead inside this thing (assuming I’ve grabbed a live bomb). But now i need to figure out how to detonate the sucker.
Question: Is there a five day waiting period for an electron gun?
What is spin and how is it measured?
I know the math behind it, and can (or perhaps: used to be able to) do fairly simple liner algebra calculations (e.g., work with eigenstates/eigenvectors and whatnot) to get a rudimentary grasp of superposition, the measurement problem, etc.
But what’s physically going on during the measurement process? I don’t mean what’s happens to collapse the wave (though if you have a definitive answer, do share!), I mean how do you detect spin and how do you know when a particle has been spun once, twice, or halfway around?
How much stock do you put in Super Symmetry (I just finished reading Frank Wilczek’s The Lightness of Being, and he makes a rather convincing case)?
Do you tinker with Super String Theory at all?
Besides the Higgs boson, what other things of interest might the LHC find?
If you could be any atomic or subatomic particle, which particle would you be?
Just how deep do you think this rabbit hole goes, that is, do you think there are more layers to fundamental reality then we currently have theories on (what does your gut tell you)?
Do you have to buy your own crowbar, or is one company issued?
Ooohhh, I can’t wait for the o.p.'s answer to this question. It is going to make your brain hurt.
To the o.p.: what made you decide to go into physics, how did you get interested in your current field, and what kept you motivated through the years of graduate school, warnings from others as to the modest compensation you were likely to obtain from your degree, and the high amount of competition for the relatively few research jobs in the field?
Stranger
What does your work consist of, and was it what you had in mind when you were in college?
How do you get a job in physics? Is it just a matter of going to school, connecting with the existing physics community, and then being part of the social network, working with existing physicists while a student, or even being groomed for a position as you progress through school? Can someone from outside who has the necessary technical skills (electronics or machining, say) but knows nothing of high-energy physics get a job at a Famous Lab?
Are there many women in physics? There was at least one female Doper who was in physics and who was hot. It’s that combination of brains and beauty… I’m thinking of Angua? (Astrophysics, female, and South Asian. Man, what a combination. 
)
Did they laugh at you when you presented your theory? Are you going to show them all?
They probably did. I know they laughed when i presented my therory of cold fusion.
Pasta, what’s the status of the string theory today? Out of favor, still in, or what?
If you manage to open up that black hole, would you be a pal and see if I left my car keys and umpteen multiple lost socks in there?
It’s the only place left I haven’t looked.
Wow, thanks for the questions!
- What are the top few things being worked on in your field and what’s your take from an Insider’s perspective- any big developments seemingly imminent on the horizon?
I’ll start with this one, as it might provide background for other answers.
Large Hadron Collider
The last century of particle physics research (though it certainly wasn’t called that the whole time) had led us to a predictive framework – the Standard Model of particle physics – that works extremely well and is even rather elegant in certain respects. Two points about the Standard Model (SM): (1) it predicts the existence of a particle, or set of closely related particles, that hasn’t been seen yet (namely, the Higgs) and (2) the parts of the model that are not elegant are really not elegant.
The Large Hadron Collider (LHC) is targeting both of these issues. In the SM, the Higgs mass is related to many quantities we have already observed (e.g., quark masses), and you can reverse engineer what the Higgs mass has to be, given all the measured numbers. The answer: somewhere between 110 GeV and 250 GeV, give or take, and definitely light enough to be seen by the LHC.
As for the inelegance: the model has a lot of “fine-tuning” in it. That is, certain parameters that are nominally on equal footing are observed to be vastly different in value (like, 1-part-in-10[sup]30[/sup] different in some cases.) The model still works, but these features are suggestive of new physics that we are missing. One attractive explanation is called “supersymmetry”, which actually predicts such ugly discrepancies. Supersymmetry requires a new class of particles that the LHC experiments will search for.
(Aside: I’m happy to hold sidebars on jargon like GeV or whatever. After all, answering questions is what this thread is all about!)
Cosmology
About a quarter of the universe seems to be made up of matter that we cannot see and whose nature we are unsure of. This “dark matter” could be new fundamental particles, and many experiments are searching for them. Supersymmetry (above) offers good candidates, and you can look for these directly at the LHC. On the other hand, you can try to detect dark matter particles just floating around in free space. There are many groups doing this latter type of experiment. The set up is physically rather small – you could put it on a table top, if it weren’t for all the secondary systems like shielding and cryogenics.
The universe also seems to made up of matter, not antimatter. We’ve got to explain that.
Neutrinos
Most neutrino experiments these days relate in some way to the fact that neutrinos have mass, a relatively modern revelation. When you give them mass, the quark side of the SM and the neutrino side have similar structure, but the measured parameters don’t come out similar at all. Neutrinos are way less massive than quarks (factor of 10[sup]7[/sup] or more) and they much more easily change identities with one another. (Detail for advanced readers: the unitary transformation that maps the free-Hamiltonian quark eigenstates to the weak-interaction quark eigenstates is nearly diagonal. This transformation for neutrinos, in contrast, is nowhere near diagonal, with some mixings near maximal.)
A variety of novel phenomena become possible when you give neutrinos mass, and lots of folks are probing these. One example is a new mode of nuclear decay (“neutrinoless double beta decay”), which would be rare (if it happens at all) but which would tell us some deep things about the nature of neutrinos. It could also be the case that neutrinos have the properties needed to explain the matter/antimatter imbalance of the universe.
Precision tests
More groups than you might imagine are doing precision particle physics. The idea is simple enough: if you can get a huge gain in precision on some measured quantity, and that more precise number deviates from prediction, profit! (Of course, if the prediction itself is the limiting factor, better measurements don’t help.) These are often (but not always) smaller and cheaper experiments with clever designs. Some areas: strength of gravity, antimatter properties, magnetic moments of fundamental particles, violation of parity or charge*parity symmetry, rare process searches.
This is certainly a partial list, but I’ll move on…
How much did the LHC cost, and who paid for it?
A follow-up: lemme 'splain the difference between theoretical and experimental particle physics. It’s pretty fundamental to the field.
There are essentially two parallel worlds of particle physics. In broad strokes, theorists formulate the models that explain new observations and predict future ones, while experimentalists conduct experiments to test existing theories or probe unexplored areas. Developments happen from both ends. Theorists can have a breakthough that leads to new, testable predictions. Experimentalists can uncover something that no one expected. Both sides have been vital throughout humankind’s march to today. It is expected that the next big step will come from the experimental side, in particular that the LHC will show us a bunch of new stuff that we will have to explain. (Of course, theorists have had a huge lead-up period to “pre-design” theories for tons of possible LHC observations. Many of these will die once data is available.)
While theorists must understand how experimentalists get things done, and vice versa, a given physicists can usually be cleanly labeled one or the other. Within the field, the two sides hold a mutual respect for what the other does.