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Higgs Properties Micro Workshop January 15, 2009

Posted by gordonwatts in Conference.
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There is a micro workshop going on at the UW this week: Higgs properties. The web site contains links to the talks and we are also uploading video of the formal discussions (sorry, it is in EVO format).

This is the first in a series of Joint Theoretical-Experimental workshops run jointly by the University of Washington Physics Department and the University of Oregon Physics Department. The idea is that everyone has been spending all of their time at the LHC working on the Higgs discovery (as we should be). But once the Higgs is discovered – then what? The most important question, perhaps, is “What kind of Higgs is it?” Is it a Standard Model Higgs? Or is it something more exciting – a Higgs that looks like it better matches a particle in another theory?

Actually, this question is the age old one in particle physics. As soon as a new particle is discovered one must measure everything about it to make sure it is the particle we think it is. We think we have a duck, now, listen to its quack and make sure it is a duck! We did this with the top quark discovery back in 1995. As soon as we had it, we started measuring its properties (for current results see the Other Properties section of our current Top Results).

Of course, if we are do this this properly, we need to know what numbers are expected within the theory of the Standard Model – so we can look for deviations. And with the Higgs this is just getting started. Experimental and Theoretical concerns come together here: some things are hard to measure and others are hard to calculate. The point is to find the numbers that need a bit more calculation or slightly better measurement techniques. This is best done when you have a group of experimenters and theorists sitting around a table hashing things out. We can then all go back to our offices and our experiments and try out our new ideas over the next year. I suppose one can think of these workshops as a jumping off point for new investigations. The biggest surprise for me is how theoretically unstable the jet-veto cut is. I don’t really understand enough of the issues yet to write about it, however.

I really like this format of workshop. I attended something similar in at Davis back in 2007 on really crazy (unexpected) theories. This one is organized around a one or two talks in the morning and afternoon, and the rest of the time is spent in discussion in smaller groups. The result is people like me, who are lucky enough to be local and perhaps don’t know so much about Higgs properties, are learning a lot, and the experts are getting to talk about the things that need to be done for the next year. There is one major downside to this however: it is at my home institution. That means I’m still preparing lecture for classes, attending department meetings, and coming home every evening to be a Dad. The result is the workshop doesn’t get as much time as it should! Or I’m just not getting the sleep I should be getting!

The series is supported by the DOE – they gave us enough money for this idea that we can fly participants to Seattle. This makes a huge difference as to whom we can invite: it is much easier to pull people from Europe, and in a world of tight science budgets this is hugely appreciated!

UPDATE: Ann Heinson pointed out I should really be linking to a much nicer web page with top quark results on it.

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ICHEP Should Be Good! July 31, 2008

Posted by gordonwatts in Conference, D0.
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ICHEP is really getting under way this Sunday — it should be a good conference – with a bunch of interesting results. Some I know about, some I’ve heard rumors about — I’m eager to see what is actually going to make it out there. The only bummer for me is they aren’t using CERN’s agenda system so I can’t just DeepZoom the thing!

Oh — an D0 just passed another milestone in data it has collected — over 4 fb-1 now! The results shown at ICHEP are on the 3 fb-1, however.

Giving a Good Talk May 28, 2008

Posted by gordonwatts in Conference, physics life.
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I watched a practice talk for Top 2008 the other day. The person giving it did a great job. They were way more prepared than I usually am by time I usually give a talk. Unfortunately (or fortunately) there is a lot more to giving a good talk than just a good deck of slides. I think the number one thing for me is “tell a story.”

I started searching the web for other advice out there — there is a lot… Some of it I had never considered before.

  • FONT SIZE. Ok, this one I and I hope everyone else knows well. But feel the need to repeat it because I see so many people doing it. And I’m getting old – so this is becoming more and more important to me! 🙂 While small fonts show up very well on your screen, they are horrible in a talk – no one in the back of the room can read them!
  • Colors. Ok, this is another one. If you have a white background, don’t use yellow text. Similar advice for dark backgrounds. Contrast on your screen makes this sort of thing look great. Not true for projectors — they are horrible low-contrast things. If you even have to think “Hmmm, I wonder if that color will show up well?” then it probably won’t. Kill it. 🙂
  • Use Pictures, not not needlessly. There is plenty of stupid clip-art in the world. If used correctly, it can be funny. The problem is that it is rarely part of the story you are trying to tell – you just put it in to have some fun. Works once. Perhaps twice. On the other hand, don’t fill your slides with text! Dense text is really hard to read. Plots, diagrams – all of these help a lot. Yes, they take longer to put together than just writing some straight text. Tough. 🙂
  • Similar, except more sparing, advice about animation, with a caveat. We really don’t use it in particle physics talks. That is ok — it is very hard to use correctly. The same with pictures: if you are going to use it, then make sure it is telling a story. Perhaps my best use of animation is the decay of a bottom quark. First the hard scatter, then the B hadron, then the hadron’s decay tracks, and finally construction lines. This animation shows how the decay unravels – so it is part of the story. I would call that “good.” The other thing about animation: make sure you don’t have to wait for it. Now, that said, everyone in particle physics likes PDFs – which don’t do animation in the sophisticated way that the various presentation programs do. So, make sure when your animation is done that nothing important has been obscured (I’ve violated this so many times. :().
  • When you walk around, people will follow you. When you stand still, people will look at your slides. Obvious when you think about it, but I guess I never had. You could use this to your advantage, however. Got an important plot? Stand still as you laser it. Lots of text where you are basically saying what is already up there? Take that opportunity to turn and directly engage your audience and walk around.
  • Use a remote slide advancer if you can. Otherwise you are tied to the length of the cable that attaches the computer to the projector. Another bit of advice I saw out there — don’t use those advancers that have a combined laser pointer. You’ll advance your slides accidentally too many times. Ha! I’ve done that multiple times.
  • Sound like you care. I know you do. Usually we are talking about things that we’ve done — spent months and months or perhaps years perfecting. Or nursing to the point it is a published PRL. Hopefully that will come out in your talk!
  • Finally, the old perennial: don’t say “Ummm…” unless it is part of a joke!

I’m sure people have 1000’s of other bits of advice. Pile on!

Top Physics at the Tevatron/D0 and ATLAS October 21, 2007

Posted by gordonwatts in Conference, physics, travel.
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CIMG4622I spent last Thursday, Friday, and Saturday at a really great conference in Grenoble. The topic was top physics, and lessons and techniques at the Tevatron and at ATLAS. I wish I could put my finger on what made it great: it was a small group (less than 50 people, I think), and everyone was willing to talk. The first day we ran about 3 hours over, for example (yes, yes, a good 30 minutes of that was my fault). Both Lorenzo and Harrison gave great talks as well as the others. I took some pictures too.

I have pages of notes from the conference (all stored electronically, of course, despite my busted laptop – which is getting worse). Some tidbits (if you don’t care, skip over to the last paragraph – partly to help me remember):

  • At the Tevatron we produced about 8 tops per day, and 4 single tops per day. LHC will be one per second, and a single top 1 ever two seconds. This is a game changer – top becomes a calibration sample, for example (b-tagging, JES…). I can’t help but wonder if we haven’t explored all of its possible uses as a calibration sample yet. Heck, data for 9 hours at low luminosity (but full luminosity) will give you a top mass peak that you can see! And it is going to be exciting to measure that cross section at 14 TeV!! And they really are are going to do everything without b-tagging at the start of the run!
  • No one yet talks about doing analysis in such a way to make the eventual combination with CMS easy. I really wish we’d start thinking that way from the beginning.
  • I had not fully appreciated the history of the D0 JLIP tagging algorithm — it was nice to see it in action as far back as LEP and also (as I’ve seen) in ATLAS. I’m sure it is in CMS as well.
  • During my talk I made the sarcastic comment that one shouldn’t measure things twice – because you are bound to get different answers. I really did mean that sarcastically — but people kept mentioning that I mentioned it thought out the rest of the talks. Sheesh. 😉
  • There was a big difference between the ALTAS and D0 talks. In general, the D0 talks talked about one method, and then went into all the details and tricks and the general mess than a proton-proton collider causes. The ATLAS talks were often an overview of techniques. For example, for the Jet Energy Scale ATLAS showed results (but not details) from about 4 different methods. I’m sure this will change when data arrives.
  • Harrison made a rather provocative statement fairly early on in the meeting: we spend too much time trying to get the absolute scale of the Jet Energy correct. Instead we should just match the Monte Carlo to the Data and then move on; who cares about the absolute scale. I and others made the obvious point: in order to do the match don’t you end up with the absolute scale. After several goings around (over wine at lunch!), we figured out: he completely agreed that reducing the error on the jet energy was well worth the technique, but he still wonders if we could save time by not developing independent JES for MC and Data.
  • I need to start exploring TMVA.
  • In general, the D0 analyses are quite sophisticated — using multivariate techniques like decision trees. Most of the ATLAS analyses don’t yet. In fact, there was some scientism from the audience about our use of these techniques. M. Mangano came up to me at one point and asked how we knew that our decision tree analysis had actually seen single top and not something else (MC tests, the Matrix Method also sees it and it isn’t a machine learning, etc.). It sounds to me like this battle isn’t done yet.

There was only one thing I didn’t like about the conference: the agenda page is password protected. Unless you are a member of D0 or ATLAS you aren’t supposed to have the password. The reasoning is as follows: they wanted to have D0 people be able to talk about internal matters — really wanted to know the dirt behind what went wrong and what to try to avoid when working on ATLAS. And the ATLAS folks should talk about anything they wanted to as well – regardless of weather or not it had been approved. It didn’t work out that way: the ATLAS top group reacted saying that they didn’t want preliminary results shown. The result was the page was password protected. This is too bad, and I think, in the end, the password was not required. First of all, ATLAS is only showing Monte Carlo results (though the ATLAS philosophy is different than the D0 one – D0 is quite comfortable with MC results going out without nearly the cross-checks that data results get). Second, as one speaker put it, “new versions of these results will be shown shortly in ATLAS and will improve on these old results” — so the results we were seeing weren’t the preliminary ones in most cases. As for D0, I think all of the D0 speakers got an email from the top group reminding us that only publicly approved plots were allowed to be shown at this conference. Fortunately, it did not limit the discussion and all of us were quite frank in our revealing of faults and other problems. I am in general against external conferences being password protected. 🙂

The Joke Marches On: Julia now a member of D0? October 10, 2007

Posted by gordonwatts in Conference, D0, physics life.
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A long long time ago, when I was working for Dave Cutts, a Brown University professor as a post-doc, he lamented that he couldn’t make it out for a D0 collaboration meeting. These collaboration meetings are just shy of a week long and involve lots of meetings but also a chance to get together with your colleagues — they can be a lot of fun. That was back in the day when I was feeling rather full of myself, so I decided to do something about Dave missing the meeting.

The result was this collaboration picture. If you look near the bottom, near the front, you’ll see me (you might want to click on the hi-res link). I’m holding up a poster of Dave. See — Dave was there! Unfortunately for me, that turned into one of the more popular collaboration photos. It is on the title slide of many D0 talks, it is on a few posters… And there I am holding up a picture of Dave. A little embarrassing!

Blow up of AranNeedless to say, I’ve not done that again. And I just missed another collaboration meeting — this one was just last week. And there was a collaboration photo – which is pictured above. I mentioned to Aran that I was sad I’d missed it. So, Aran, my post-doc, had a little fun with me. If you look at the high-res version (which takes a while to load), you’ll find the below picture. It turns out that Aran wasn’t the only one having fun — check out the person several rows back.

CHEP Day 2 September 13, 2007

Posted by gordonwatts in computers, Conference, physics.
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I’m spending this week in Victoria, Canada attending the Computers in High Energy Physics (CHEP) conference. At one time this was my favorite conference (more on that in a later post). These summaries are just things in the talks I found interesting on day 2. [I spent last week there — I’m just getting around to cleaning up these posts!!!]

Plenary: The Future of GRID Computing – Miron Livny

Most people I talked to really liked this talk. Miron’s group at Wisconsin is the author of Condor, one of the more popular GRID aware free batch systems out there. We’ve made heavy usage of it back at UW to process ATLAS events. But I didn’t like his talk all that much – mostly because I don’t like GRID talks all that much. I got made fun of in a plenary session 2 or 3 CHEPs ago for complaining that we were talking about the GRID too much. I didn’t think it could get worse — but it has – even more of CHEP is devoted to computer science problems (getting jobs to run on the GRID) than it is on physics problems that can be solved with computers.

Miron started on a promising note: GRID computing is dead. 😉 What he meant was that you no longer got automatic funding by attaching the word GRID to a proposal. Then he said, “but distributed computing is here to stay. Lets get back to work and away from the hype.”  !!

He also has one slide in his talk where he says that we have to do better in job reliability. I’d like to point you to a NYTimes article that was published today talking about complex systems and how error prone they are. What irks me a bit is that the GRID folks have been stressing reliability for years now and their progress is, well, slow (at least to my eyes). New features and new tool kits seem to appear with alarming frequency — but no one goes back and makes sure that all the layers work well together.

He now helps lead the OSG consortium. This is a loosely affiliated group of labs and universities that have banded together to supply large computing resources to various branches of science (not just HEP). They have some umbrella funding, but its future is not obvious. I wonder if consortiums like OSG will last or will we live in a world of very large facilities like TerraGRID that we buy time on?

He also stated what would be a repeated theme: moving data files around is the single largest weak point of the GRID currently. He is right about that!

Plenary: High Performance Computing at the Petascale and Beyond (Blue Gene!!)– James Sexton (IBM)

James gave another fantastic vendor talk. It was interesting to see the big difference in IBM’s vision vs other company’s visions. Most of the discussion was of Blue Gene and how it fit into the future of computing. IBM positions it as a research machine that they can sell. They expect to develop new technologies here and then slowly feed it down into other product lines.

Blue Gene is a move away from commodity processors: they attempt to put everything on a single chip: memory controller, bus interface, etc. With as many processors as they plan to put in a rack they need absolute reliability. They are using a core based on the PPC (duh) running at only 800 MHz. They put 32 of these cores on a single card along with 10 Gigs of memory. This means each core has about 300 megs to call its own. They then pack these cards into racks — about 4000 cores per rack. They then have high speed interconnects between the cards and racks.

Livermore has 64 racks. Their mean time between failure is 7 days. All I can say is wow! Our L3 system runs about a week before a node fails and we have only about 1400 cores in that (small!) farm. 64 racks is 256,000 cores, or about 180 times bigger than our L3 trigger farm.

Applications that have run on Blue Gene include atomic and material simulations. The comment from the researchers was that these types of problems weren’t each to put into a BG, but it was possible. Protein folding also did some work — but say they need another x3 in compute power. Ouch!!!

James, along with many others, pointed to the fact that the cost of memory is not falling very quickly, so economics is going to force one into the Blue Gene model, or something that looks like it. Further disk storage and getting data in and out of disk storage is also not keeping up, leading one to wonder if it will be cheaper to re-derive results than to store the intermediate results?

His future predictions were pretty guessable: the 2-4 GHz max clock rate was here to stay, but be ready to move to using millions of cores. Memory bandwidth is going to be a problem, and reliability is going to become so much more important in these 1000 core systems.

Plenary: Canadian Cyberinfrastructure – Bill St. Arnaud (CANARIE)

Bill started this by saying that Canada was late to the GRID. This statement surprises me: I remember Canada being one of the first GRID sites to help D0 out with Monte Carlo processing. The CANARIE group is particularly strong in networking. Bill talked about several technologies that allow one to reconfigure networks on the fly. I’m not going to claim I understand this, nor do I understand why this is particularly attractive (except, perhaps, from a security point-of-view), but other talks at the conference made me think this scheme is going to be widely adopted.

One cool project they were working on, Neptune, was a large undersea network of remote sensors. A NYTimes article happened to be published the same day of the talk. Very neat!

Parallel: Booting ROOT with BOOT – Rene Bruin

The idea behind this coming improvement to ROOT is that most ROOT projects use a very small portion of ROOT. So why does all that memory have to be loaded? Why do all those files have to be distributed? Further, there are small bug fixes and it would be nice to distribute them without having to redistribute the whole of ROOT — and allow the user to update on the fly.

In order to reduce ROOT’s memory footprint, the ROOT team is doing what people have been asking it to do for the last 10 years: reduce interdependencies. A rumor has it that the straw that broke the camel’s back was Rene made a minor change to the TClass.h file and discovered that he had to recompile all of ROOT. This is fantastic! Reduced dependencies (and the ROOT team has discovered abstract classes in a big way! Wow!) should make ROOT a more stable product in the long run. Rene showed some data towards the end that had evidence that in the latest versions of ROOT the memory foot print had already been reduced — and, thus, the start up time had also been reduced (they are down from a peak heap size of about 30 megs to 4!). Fantastic!

Parallel: ROOT Graphics: Status and Future – Oliver Couet

Oliver described a bunch of new plots styles (Spider, Parallel, Box, and others). In particular, the Parallel plots looked like they might be interesting in particle physics. The spider and box plots will take me a while to get my head around in how they could be useful.

They have also shifted ROOT over to Open GL now, which has enabled some of the ALICE amazing graphics.

Parallel: ROOT I/O Performance and Functionality – Philippe Canal

Philippe is a very brave man. He spends all of his time down in the I/O sub-layer of ROOT. The ROOT team is usually listed as Fons and Rene — but I think Philippe must be getting close to deserving to be added to that list (if he isn’t already past threshold). The I/O subsystem must be a fairly thankless task, though it does contain some very cool problems that need to be solved without sacrificing speed, but it also has to be some of the most difficult and tedious work!

A lot of work has gone into storing data as compressed values — when you don’t need to save full precision. They are using a technique, it sounds like, that Scott Snyder used for D0’s I/O subsystem when he wrote that many moons ago. They have also improved the asynchronous read-ahead over a network — techniques to keep a data hungry ROOT application well fed despite network latencies. In anticipation of greater PROOF adoption, they have also improved code that concatenates results from several files into a single file. Another very cool thing: they can take an ASCII file and read it into a TTree without a user having to write any code! This will be very helpful for quick-and-dirty TTree building! There was also a cool sounding improvement to the TEventList (use TEntryList now) – a sparse and highly optimized way to store events that pass cuts.

CHEP Summary September 7, 2007

Posted by gordonwatts in computers, Conference.
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I’ve spent this week in Victoria, Canada attending the Computers in High Energy Physics (CHEP) conference. At one time this was my favorite conference (more on that in a later post). I’ve been writing up day summaries, which I’ll post this weekend, but thought I should get my personal conference summary out before the actual conference summary just to see how it compares. 🙂

First, the vendor talks (ibm, sgi, intel) were some of the best talks given. They were given nice long talks in the plenary sessions and all the companies sent excellent speakers. I think these were the best vendor talks I’ve ever seen. It was fascinating to see the different takes each company had on the future of computing: ibm: lots slow cores, little memory, sgi: evolve the current technology to its limits: pack 1000’s of cores into a single rack, intel: 80 cores on a single chip, one or two big cores with all the bells and whistles and lots of little cores that run more slowly.

Computing Hardware

Power, Moore’s law, and Heat dominated the plenary sessions. Every computing facility is feeling the pain. No one has figured out how to solve this. For the near future we will be moving towards tricks — like Sun’s black box computing. Longer term some real change in technology.

Performance & The Multi-Core Future

It seems a given that as we head towards the multi-core future we will need to change the way we write code. The memory bandwidth in and out of a chip will increase more slowly than the number of flops that chip will be capable of — so less data per flop will be a problem! It isn’t obvious we can rewrite our code to run multi-threaded: that is a huge amount of work. Further, I think we don’t have enough data on processor performance to really understand if that would help (though it seems like it would).

To that end there was only one talk (that I saw) that really looked at performance of some of our large reconstruction programs and simulation programs. The result? On a CPU with a 500 GB/sec bus (or was it 50? I can’t remember) the reconstruction program of CMS is using only 40 MB/sec!! If that is true, we will have no trouble scaling up to 80 cores given the current memory bandwidth. Further, the CPU is idle of about 60% of the time (it can process 4 instructions at once, on average it is doing 1.2).

At the start of this conference I was convinced that we were going to have to alter our programming model. But now I think there is a lot of work we can do with our current installed base in the form of optimization. By the next CHEP I expect a lot more studies of this sort. It was sad that so many of us (myself included) talked without really having too much data. We may still have to alter how we approach things — but there is more to be gained in our current frameworks.

I also predict that people working on offline software will be now asked to move away from creating random objects all the time – in some places in the CMS code over 1 million news and deletes were occurring per second! Ack!!

GRID

It is hard for me to tell any difference year to year. But the consensus seems to be funding is “dead” and we need to get on with distributed computing. Oh, and, as in every year, stability is a must (sheesh). I think that with funding drying up organizations like OSG will be disfavored and large installations, centrally and professionally managed, like TerraGRID will become the norm. GRID software will still exist so people can “easily” run on these different large centers.

I also think, give the continuing addition of layers of complexity, that user analysis will not occur on the GRID. ROOT tuples (or something similar) will be produced, downloaded to your local 10 TB cluster, and then run locally.

ROOT

Resistance is no longer an option — we have all been assimilated. It is very nice to see ROOT finally ripping itself apart and putting itself back together in a more modular and separable way. What prompted this? Slow start up times and memory usage. Awesome! Lots of other efficiency improvements and I/O improvements are getting made as well.

I can’t tell how PROOF is coming along. There are now some real installations, but it hasn’t really started to spread. The problem is that at almost every CHEP this has been the case. Unfortunately, from my point of view, PROOF cluster design still is a big iron design. Hopefully it will get simpler as time passes.

Algorithms

There wasn’t enough of this at CHEP. I like CHEP because it straddles Physics and Computer Science. It feels more and more CS like, and less and less physics like. There were some interesting talks — for example integrating advanced separation techniques (like Decision Trees) into ROOT.

There was plenty more going on, but in the few minutes I had to dash this off this is what came to mind. It was a good conference (other than the lousy network access)! Food in Victoria is also really good!