Life as a Physicist

Well, if there is one thing to be said about the DZERO workshop, it is that the recent breaking of the Higgs SM limit line by CDF and DZERO has certainly injected excitement into the experiment. On the other hand, the LHC startup is right around the corner (officially, Sept. 10). Many of the talks given were infused with both of these themes. The theme of the workshop isn’t hard to guess: the Tevatron is schedule to give another 4 fb-1 of data or so — doubling our current dataset — is the experiment ready to absorb that? Especially as people drain away from the Tevatron experiments to the LHC experiments.

On one hand, many of the future talks would split the physics they discussed into physics that only the Tevatron could do vs physics that both the Tevatron and the LHC could do. The implication being, of course, that the LHC would quickly produce better results once it was up and running.

For the Higgs searches, it was the opposite — there is a small window of opportunity that must be grabbed while the grabbing is good. Indeed, I think it is safe to say that most of the experiment is focused on getting the Higgs signal.

At the last minute I was asked to give a talk on my daqAI work. This is artificial intelligence for the data acquisition system at DZERO. Actually, there is nothing “AI” about it - it is just a bunch of if-then-else statements that recognize a problem and either tell the shifter or attempt to fix it themselves. The up shot is better up time. Actually, DZERO’s data taking efficiency is amazing. Above 90%. When we hit 80% we claim we’ve had a bad week. Our competition, CDF, is not doing so well. While I’d like to think that daqAI helps towards this (and I suppose it does a bit) the real reason is the people we have working on this. CDF - if the Tevatron is going to say anything about the Higgs then you guys need every drop of data… Get to work!

Another really interesting session I went to was the b-tagging one. I used to co-run the b-tagging group at DZERO. It was especially satisfying to see some large projects that I attempted to get going while I was the co-convener actually completed. They weren’t completed because they continued using myself - people mostly started from scratch - bit still… And the fact that ex-students of mine had a hand in getting those things done. Very cool! And, of course, there is all the ongoing work - some of it rather interesting.

Lots of other interesting stuff, but I can’t talk about it of course.

Finally, our Prague hosts did a great job. That picture above is Julia dancing to traditional Czech music.

I’m on vacation now, in Cyprus. My wife was full time Mom last week while I was attending the DZERO workshop. This week it is her turn - she gets to keynote at the physics education conference here in Cyprus while I’m a full time Dad. After that we will be busy moving back to the USA. In this hotel they charge 20 euros a day for internet… so I’m not sure if my blog will be updated much! But we’ll see…

There was an unspoken theme at the DZERO workshop this week. Stick with the Tevatron for a huge, but iffy, payoff. Or switch to the LHC now because it is a “sure” bet (as sure as anything gets in research).

This is all about the Standard Model Higgs search at the two accelerators. If such a Higgs does exist the LHC is bound to discover it. The LHC has some “difficulty” at low mass Higgs (below about 125 or so). Difficulty for the LHC means it could take up to 3 years for a single experiment to declare a 5 sigma discovery, the gold standard of “discovery”.

At the Tevatron the Higgs analysis is all about difficulty. Each new Higgs result you hear or read about is a tour-de-force of new techniques and new methods of extracting every last bit of signal out of the experiments. As a graduate student I never remember techniques this sophisticated. And the LHC pre-trial analyses are not as sophisticated either (on the other hand, they don’t need to be).

Global fits to the Standard Model currently predict the Higgs to be low mass - between 114 GeV and 120 or 125 GeV. The Tevatron is currently x2 away from being sensitive to this mass range. By doubling our dataset to 6 fb-1 of data and making a number of improvements to our analyses, we expect that we should be there. These improvements are not easy - it will require a lot of work and a lot of people. Nor are they assured. At best, if the Higgs is there, and we aren’t unlucky, we should be able to see it at the 3 sigma level. But never the 5 sigma discovery level. That will have to be left to the LHC in any case.

So is it worth sticking with the Tevatron? Well… the payoff would be huge to see something at the 3 sigma level. So it is like a lottery with high stakes. The chance of winning is not all that sure, but the jackpot is big!

Me? Well, I’m working on both the LHC and the Tevatron (as are many US physicists). I have a student working on the Higgs search at Fermilab, for example. I’m deeply involved in a number of topics at the LHC as well.

What will happen? Hard to tell. Things to watch? Well, that is easy. There are only two things that really matter here - the performance of the Tevatron and the performance of the LHC. Each physicist who is on both collaborations is performing some complex calculus to optimize their time on the two experiments depending on the chances of success.

I wish us all luck.

A few posts back some folks were wondering where to watch for LHC news as the startup nears. The “LHC First Beam” website seems like a pretty good place to start. For example, recently posted:

After a period of optimization, one bunch was kicked up from the transfer line into the LHC beam pipe and steered about 3 kilometres around the LHC itself on the first attempt. On Saturday, the test was repeated several times to optimize the transfer before the operations group handed the machine back for hardware commissioning to resume on Sunday.

Hey! There has been beam in the LHC!! The website contains a “count-down” clock too. 28 days…

Now I have a stupid question for the folks putting this website together: Why isn’t there a RSS feed!?!?! So old-skool!

That isn’t what you think. “WTF” is abbreviated as “Welcome to France!” — but is basically the same. My wife discovered this coined on David Lebovitz’s blog. He is an American who moved to Paris back in 2002 - a pastry chef. And he frequently writes about how strange France can seem to an American (see his post on 5 great business to open in France - we have have experienced all of them).

Our building here in Marseille is about 100 years old. It has a spiral stairway that accesses all five floors. A very small elevator is installed in the middle of the spiral and carries people up and own. Much to the consternation of us occupants, it has a tendency to stop between floors. Since it does get stuck every now and then, the few moments when the doors open between floors and you aren’t sure they will close again can be a bit nerve wracking. Last time the stuck thing happen the elevator guy came by. I explained, in my broken English, the problem. He fixed it apparently. That was several months ago. Last week, however, he ran our buzzer and came up to talk to Paula. He explained why the elevator keeps getting stuck: the workers in the business that occupies the 3rd floor apartment smoke too much. Hmm… My wife finally worked it out that they use the elevator so much that some key bit overheats, expands, and causes it to stop between floors. Not that he would replace it, but he did come all the way out to the building to inform us…

Banks are weird here. In the USA they are much more consumer oriented. For example, our ATM cards all have a limit: no more than 350 euros per 7 days. France is much more of a cash society than is the USA, so 350 in a week can sometimes be cramped — but no problem, we have two cards, and we can each withdraw. So unless we are traveling this has never been a problem. But… it turns out… lets say you try to withdraw 200 euros. It fails. So you try again and you manage to get out 150. The next day you try to get out another 50. Nope — you are over the limit! You go to the bank and complain! They look at the ATM record and tell you that you’ve withdrawn more than your allowed 350. After you direct them to look at your bank account they agree that the first 200 euros wasn’t real. Will they fix the ATM card so you can withdraw? Nope - sorry — you have to wait until Saturday!!

WTF!

That is Pork’s Knee (or Pork’s knuckle as it was labeled on the menu). And it was good. Big enough to search two, and J-mo ate a little too. Somehow I don’t think you would ever find a dish quite like this in France. And the beer along with it - I’ve not tasted beer that good in months! I love French food and wine, but there are some things done better elsewhere…

I’m in Prague this week, along with the family, attending D0’s yearly workshop. I don’t know how much posting will occur (probably not much). And the week after I’m on vacation being a Dad and Paula attends a big conference. I’m pretty sure almost not posting will occur then.

In the mean time I’m going to enjoy as much Czech beer as I can!

There is a book review in the NYTimes right now by Overbye titled “Inside Story of the Telescope That Nearly Wasn’t Built” - about the Hubble.

The space agency wanted to make sure its  long-awaited and astronomically expensive telescope — soon to be launched into orbit above the turbulent fog of the atmosphere — made an appropriately cosmic splash. The advice from those of us in the press peanut gallery was always the same and simple: pictures — cosmic postcards like the live pictures of other planets being transmitted from the Viking and Voyager spacecraft — early and often.

This is PR 101 — everyone, including us scientists, is easily captured by pictures. Especially stunning ones. Sure — they may not be the best way to convey accurate scientific measurements - but they are very easy to relate to. Are we doing the right thing for the start of the LHC? Do we know what pictures - science pictures - we are going to be pushing to the public?

ATLAS has a whole outreach group (as does CMS, I’m sure). We have the ATLAS Book. We have a movie. But what cool picture are we going to give the press when the science starts? Another picture of our detector - like the one attached to this blog posting? Surely we can do better. Our event displays - most are tuned for us to look at as scientists, not for the press or the public. Do we have anything?

Enough of my ideas. What should we have ready when science starts to roll out? At the Tevatron we write these plain-English-summaries. They aren’t totally plain, unfortunately. But perhaps we should get someone from the PR office to work with every analysis that is published to work on something like that?

Other ideas?

This is August (I still claim June never happened). In most of Europe, and definitely in France, this is vacation time. Literally - things shut down for a whole month. Restaurants are closed. Even the beaches we hang out at are more empty. The tourist beaches are more full, of course. The halls of the lab here in Marseille are just long stretches of closed doorways.

But you know how I really know it is vacation time? They have stopped filling up the soda machine here. Can you imagine in the USA a Coke or Pepsi machine being allowed to stand empty for 2 or 3 weeks? I think not. But even more telling here in France… the coffee vending machine was broken for four days straight!

Any what am I doing going to the office every day!?

Yesterday I mentioned that the Tevatron experiments had finally started to rule out the Higgs. I thought I’d post another plot that shows exactly how hard it will be - and so gives you an idea of how much hope the Tevatron has of actually catching the Higgs. Click on the plot to get an enlarged version of the jpeg (here for details).

The most important lines in that plot are the black one (1-CLs Observed) and and the 95% CL thick blue line. The thick blue line is the point at which, in our best statistical estimate, we are 95% confident that we have not observed anything. While the blue line is the “goal”, the black line is where we are now - the current observation. A lot goes into that black line - many different physics analysis contribute (from both D0 and CDF), the physics of the Higgs decay, the physics of how the Higgs boson is supposedly made, and how good our detector is at seeing the Higgs. As you can see, we have just peaked above the 95% level near 170. And that is what allows us to say that we’ve excluded the Higgs around 170 GeV.

Now, the future. You’ll note that the curve is pretty flat near where it peaks above 170. That says to me that when we add more data and minor analysis improvements we will be able to quickly broaden the amount of the observed line is above the 95% CL line. Where the black line is steeply falling, however, it require a huge amount of work (even if it is possible at the Tevatron).

Finally, in yesterday’s post the plot started at 114 GeV. This one starts at 155. What about everything from 114 to 155? Yes — we are working on that. For example, at D0 we have individual results already (and if you look at this plot, given the discussion, you can see that how we are doing as far as getting towards ruling things out at low mass - though the plot is a very different type of plot - but you can guess what is going on if you are not familiar with it). I couldn’t find the recent update of the CDF combined results. But the low mass combination between the experiments was not completed in time for ICHEP. I’m hopeful that we will see it soon - but as they say, it ain’t out until it is ready to be out!

See that little red blob around 170? That is the Tevatron starting to seriously tackle the final big physics problem left on its plate. Where is the Higgs? The question is — will it finish the job before the LHC starts producing real physics?

The numbers on that plot are the mass of Higgs boson, the final bit of the Standard Model we physicists haven’t directly observed. The last experiment to search for the Higgs were the LEP experiments. As you can see, they searched up to 114 GeV. The Tevatron is searching from 114 up as high as it can go — it so happens the first bit it was able to exclude was around 170 GeV in mass.

The Higgs mechanism is what gives most particles mass. If it was absent from our theory then many masses (and other things) we have already measured would be wrong. That does not mean, by the way, that the Higgs has to exist - but something like it does have to exist. The Standard Model Higgs is just the simplest explanation that we came up with fix the masses. If that whole range is searched and nothing is found - that would be huge news. And very puzzling!

Press Release Here. And combined CDF and D0 note describing the analysis here.

A bunch of us are trying to finish up a paper and get it past internal referees in ATLAS. Time scales are extremely short. In order to make sure we beat a deadline we have had to respond to comments from the referees on extremely short timescales (like a day or two). I am located in Marseille, and my student is located at CERN, in Geneva. It really isn’t possible for either one of us to answer the questions and update the paper on our own.

We’ve hardly used email for this process. Two tools we’ve used rather intensely: IM and cvs and LaTeX. IM is exactly what it sounds like - instant messaging. I’m using Pidgin and I think my student, who is on a Mac, is using AOL’s IM client. cvs is a source control system. We have all of the papers’ files hosted by the central cvs system, along with a local copy on each of our machines. When we want to update a file, we edit it, and once we are satisfied, we up load it to the central cvs system, and then the other person downloads the updated file. TeX is a typesetting tool designed for the sciences. It is quite old and while many people swear by it, I don’t think so much of it in today’s modern world of WYSIWYG editors. The central system keeps track of all the changes we make. Finally, we posted the questions from the referees on a twiki. A twiki is basically the same software that is used by Wikipedia - it allows you to edit a web page on the web. As we moved along the document we would update the response to the referees. Occasionally the issue was too complex for IM and we’d resort to Skype.

This worked very well. There were a few places it could have been better. For example, when working on the wording there would often be fights… errr, discussions… between me and my student over wording. So we’d end up putting the paragraph in IM and sending it back and forth. It would have been very cool if I could have just typed something in my editor and he could have seen the update in context where he was working. The other thing that would have been nice was if we didn’t have to worry about which file we were modifying. Because of the way cvs works, if two people modify the same file at the same time, there is a chance that it won’t be able to resolve the conflicting edits. The result is it is often simpler to just communicate which file is being edited and the other person stays out. I have to say that I don’t care much for the editing experience on the twiki. There is a WSIWIG web editor, but it just feels very awkward. It would be cool if I could suck the page into Word, modify it, and then spit it back out again.

The other thing that would have been nice is if Pidgin didn’t keep crashing. And also it would have been nice if we could have sent files or pictures back and forth. For whatever reason this did not work with my students AOL client.

Other novel ways to solve this set of problems?