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Fizzle! August 4, 2009

Posted by gordonwatts in ATLAS, Fermilab, LHC, Tenure, university.

The biggest, most expensive physics machine in the world is riddled with thousands of bad electrical connections.


So starts a mostly accurate article in the New York Times about the current state of the LHC. There is good news and bad news in this sentence. To paraphrase a famous politician currently sight-seeing north of South Korea, it really depends on your definition of the word bad. To most people, if someone says that the electrical connection between your light and the wall socket is bad, then that means your light won’t work. That is the normal definition of bad. We High Energy Physicists have a different definition of bad. 🙂

For us, bad means that the connection isn’t going to conduct as much current as it could (I had a blog post about this a while back – but this article contains an excellent explanation – well worth registering if you have to to read it). And this is the reason behind the timing of this article. As I mentioned in that article it would not be until the beginning of August that the LHC group of scientists would have finished measuring all those connections – all those splices – and know exactly how bad they were. Tomorrow the LHC and CERN will announce exactly what energy they will run the LHC at initially.

But scientists say it could be years, if ever, before the collider runs at full strength, stretching out the time it should take to achieve the collider’s main goals…

And that is the bad part of the news. The bad connections mean that we can’t run at the full 14 TeV energy – we will run something short of that (I’m betting it will be 7.5 TeV – if I get it right it isn’t because I have inside information from the accelerator group!). The article is correct that running at this reduced energy won’t give us the access to the science we’d all expected and hoped for if we were running at 14 TeV.

But another thing to keep in mind is: we need data. Any data. And not to discover something new – because we need to tune up and commission our detectors! We’ve never run these things in anything but a simulated collider environment or looking for cosmic rays. We would probably be able to keep ourselves busy for almost a year with two months of data.

Peter Limon, a physicist from Fermilab got it right:

“These are baby problems,” said Peter Limon, a physicist at the Fermi National Accelerator Laboratory in Batavia, Ill., who helped build the collider.

Indeed, these are birthing problems – no one has ever run a machine like this before. Which brings me to the one spot in the article that got my hackles up:

“I’ve waited 15 years,” said Nima Arkani-Hamed, a leading particle theorist at the Institute for Advanced Study in Princeton. “I want it to get up running. We can’t tolerate another disaster. It has to run smoothly from now.”

Nima, whom I also know (and like), is a theorist. If an experimentalist said this we would all make them run outside turn around three times, and spit to the north to cancel the jinx they would have just placed on the machine. I think we can all guarantee that there are going to be other failures and problems that occur. We hope none of them are as bad as this last one. But if they are, we will do exactly what we’ve done up to now: pick up the bits, study them, figure out exactly what we did wrong, and then fix it better than it was originally made, and try again.

There was one last quote in that article I would have liked to have seen more of a back story to:

Some physicists are deserting the European project, at least temporarily, to work at a smaller, rival machine across the ocean.

The story behind this is fascinating because it is where science meets humanity. The machine across the ocean is the Tevatron at Fermilab (I’m on one of the experiments there, DZERO). There is plenty of science still there, and the race for the Higgs is very much alive – more so with each delay in the LHC. So scientifically it is attractive. But, there is also the fact that a graduate student in the USA must use real data in their thesis. Thus the delays in the LHC mean that it will take longer and longer for the graduate students to graduate. In the ATLAS LHC experiment the canonical number of graduate students quoted I hear is about 800. Think of that – 800 Ph.D.’s all getting ready to graduate – about 1/3rd or more of them waiting for the first data (talk about a “big bang”). Unfortunately, you can’t be a graduate student forever – so at some point the LHC is taking long enough and you have to move back to the USA in order to get a timely thesis. Similar pressures exist for post-docs and professors trying to get tenure.

UPDATE: Just announced earlier today: they will start with 3.5×3.5 – that is, 7 TeV center of mass. This is exactly half the design energy of the LHC. The hope is that if all runs well at that energy they can slowly ramp up to 4×5 or 8 TeV. At 8 things start to get interesting as a decent amount of data at 8 will provide access to things that the Fermilab Tevatron can’t. Fingers crossed all goes well!


Is the LHC Doing Physics? March 24, 2008

Posted by gordonwatts in LHC, physics life, Tenure, university.

One one of my lasts posts about computers and HEP, Kevin left a comment.

It would appear to me that the LHC has been for many years “methods development,” yet I’m assuming a couple people already have tenure on it and more than a couple Ph Ds have been awarded for developing the technology.

As far as I know, in the USA, no institutions will give a Ph.D. for an experimentalist if they have not touched data. As far as I know, no one has managed to get an experimental LHC Ph.D. in the USA by just running Monte Carlo or working on a bit of the detector. Now, parts of the LHC have taken data — i.e. the test beam.

The point of the test beam is exactly as it sounds – we put portions of the detector in the test beam to test them out. We fire known particles at known energies into bits of the detector and make sure they react (and readout) as we expect them. If they don’t, we adjust the physics models we use to simulate them or perhaps find something wrong with the detectors and fix them. It is not common to get a Ph.D. in the USA on test beam data, but it has happened. For example, D0’s initial startup (Run I) was so delayed I think a few people did this and then remained on D0 as post-docs to get their hands on real data.

Europe is different – there you can get a Ph.D. on Monte Carlo studies or on building a detector. As far as I know, it isn’t viewed as any different than getting a Ph.D. on data.

But, if you are in the USA, what do you do? This is exactly why most HEP groups maintain a foot in more than one pie. For example, I do a lot of work on ATLAS now – but I also do a lot of work on D0. D0 is a running experiment and produces real results. My tenure decision was on D0. I could have started on ATLAS when I arrived at UW 8 years ago – there was plenty of work to do – but it was correctly seen as suicide. Instead I worked on D0. I only just now have graduate students working on the LHC. I bet if you looked at the number of US graduate students on the LHC it was rather small and is now rapidly increasing. And that is because we are finally in the time frame that these students can get a Ph.D. on LHC data.

Finally, I have heard of programs that offer Ph.D. in detector physics and accelerator physics – which is very different from the work I do. I know less about them than I should, however.

However, Kevin correctly points out, once you are past the tenure bar you can just do what you want. Want to put all your marbles in the LHC basket? Go for it – no problem! Directly addressing the implied question in Kevin’s comment – presumably the person on the LHC who is making these criticisms had to go through the tenure process. And hopefully they are applying the same standards that were applied to them. Sometimes it is hard – I went through the qualifying exam as a student. Hated it, and it wasn’t clear that it offered any net gain for me or my fellow students. I passed, and now, about 15 years later, I sometimes catch myself thinking “it wasn’t that bad…” Some people carry that to an extreme. In the tenure case this is exactly why it is necessary to consult with other people in the department to understand if this is something unique criticism held by one person or is generally shared criticism.

Final installment of this 3-part series next. 🙂

UPDATE: Changed the tone of MC physics paragraph above.

Tenure and Physics March 21, 2008

Posted by gordonwatts in Tenure, university.

One one of my lasts posts about computers and HEP, Kevin left a comment.

After reading your blog (and enjoying it of course) for over two years now, I feel you have discussed a lot of issues in programming, ROOT, C++ vs other languages, computers and other things that are tools to do science but which are not themselves science (or at least not physics). I ask because a physics colleague of mine has recently been warned that he is doing too much methods development (and publishing on these developments).

This is a scary situation. My own tenure decision occurred while the Tevatron was struggling to get itself up off the ground. As a result the physics topics I’d been talking about when I got hired at UW were nowhere near being finished. It was a close scrape (at least, that was how I felt). I had physics in my pocket, but much of it was not yet published. UW, which has had some ridiculously good table-top experimenters – holds everyone to a rather high standard. And even under the best of circumstances a HEP person is already at a disadvantages when those standards are applied.

That said, here is my advice. You have to have the physics results. Most big research universities think developing a new method is cool — especially if it will let you do a whole new set of physics results in the future — but the method itself or the sake of the method isn’t all that interesting. The physics results and potential to do physics results is. I have seen people in HEP, for example, get overly involved in the methods development and lose track of the physics side of things. It does hurt them – and this chestnut is true outside of HEP as well.

Now, it would appear that your colleague is not in particle physics but is in table top physics (or similar). One thing that goes into a tenure judgement is expected performance in their field. For example, a theorist is expected to have n-papers per year (I’m not kidding; I’ve heard this said), a table top experimenter isn’t expected to do much their first two years as they build up their lab, but then a good paper every 6 months or so (depending on the challenge they’re facing, of course). In that sense, the tenure decision depends on what subfield you are working in.

Finally, if only one colleague has made this criticism well, it may be that it can be ignored. 🙂 The first thing to do is ask others in the same sub-field (who have tenure, preferably) if enough work is being done. Often departments will have a formal review process – make sure to have frank discussions during that review process. Make sure to have tenured friends in the faculty that can report on discussions that happen in closed meetings. Finally, look one can look at other people at other institutions in the same field — especially the ones that are perceived as “hot shots.” What are they doing differently? Sometimes it is just a matter of a high wattage bulb burning brightly, other times you can see strategic decisions they made – copy them!! I guess most of this is common sense, but it never hurts to repeat it!

More tomorrow on Kevin’s comment.