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Archive for October, 2009

End of summer sailing trip

Friday, October 30th, 2009
Slide1

50-mile water route from Chicago to Racine, WI

The weather in Chicago has been pretty crummy for weeks now, but winter seems fast approaching when I finally give up on the possibility of more nice days and return the boat to its winter hibernation spot, Racine, WI.

Racine is about 50 miles north of Chicago and one immediately wonders why pick such a spot to return it to every winter. Coincidentally, I think the answer is a physics term:

inertia: a property of matter by which it continues in its existing state of rest or uniform motion in a straight line, unless that state is changed by an external force.

The sunrise over Lake Michigan on a chilly October morning.

The sunrise over Lake Michigan on a chilly October morning.

The view back as we say goodbye to Chicago for the summer.

The view back as we say goodbye to Chicago for the summer.

Basically, that’s where I found her six years ago and it seems easier to take it back each off season than to find a new location and transport the trailer which is far from road ready. Also, the marina there is very nice and extremely affordable compared to around the Chicago area. Finally, there is the matter of the 50 mile trip at the beginning and end of each season which is actually quite fun. In the spring we stopped over at Waukeegan Harbor on the way down and I wrote about it here on QD. On the return trip we usually barrel through in one 8-11 hour day on the water.

This time of year that typically means leaving before sunrise to get in to Racine well before dark. And I can assure you that it is freezing on the lake that early in the morning in October. I look relatively content in the photo to the left, but it did take six or seven layers of clothing, a winter hat and gloves, two pairs of wools socks, hot coffee, and that gorgeous sunrise to get me so cheery.

It ended up being a beautiful day, although it never really warmed up out on the water. We did make record time with a very strong tail wind the entire day, but eight hours after leaving Chicago the Main Street draw bridge as we entered the river in Racine was a welcome sight.

Bright and early tomorrow morning we’ll go up by car and take her out of the water, thus bringing summer of 2009 officially to a close 🙁

State Street draw bridge in Racine, WI

Main Street draw bridge in Racine, WI

Main Street bridge from Main Street.

Main Street bridge from Main Street.

Safely back in the Racine river.

Safely back in the Racine river.

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The Naked Die!

Friday, October 30th, 2009

This is for sure true here at the conference. As Frank already pointed out, it is very cold in the conference centre while we have a beautiful summer day outside. I am also wearing a long sleeve shirt and regret very much that I left my fleece jacket in my room.
So I am also in Florida, at the IEEE NSS/MIC conference. This conference exists since more than 50 years and was established when instrumentation for the detection of particles and ionising radiation became a necessity. They started out with a rather small group of people. Many years this conference was held one year in San Francisco and the other year in Norfolk, the largest Navy base in the US. Only in 1998 they decided to go with this conference outside of the US and held the conference in Toronto, Canada. That was actually the first time I came to this event. Since then this conference changed into a travelling meeting. We were in Seattle, Lyon, San Diego, Norfolk, Portland, Rome, Puerto Rico, Hawaii, Dresden and now Orlando in Florida.
What does NSS/MIC mean? It stands for Nuclear Science Symposium and Medical Imaging Conference. Yes, Nuclear! When asked at the US border what conference I would be attending while being in the US, I usually say “Medical Imaging Conference” as the word “nuclear” always makes this guys nervous and might result in a lot of questions. Medical sounds really harmless.
But by nuclear one means everything related to detection of particles. And it is a large field. Here one meets not only particle physicists, but also people working at nuclear plants, in hospitals or people from the army. And this makes it even more interesting, to learn from completely different communities.
Yesterday for example I talked some time to a medical physicist and learned why they build this tiny little PETs*. Those small-animal PETs are for clinical studies at rats. For example when a cancer medication is tested, the rat can be placed in such a device and the impact of the medicine can be studied live using this device. Developing such a mini device is not as easy one would think. This conference is, besides many other topics, the place where experts on these devices meet and exchange their experience.
Important are also the evenings here. The last couple of days we were sitting outside close to the pool and met people from all over the world. As I attend this conference since 10 years, I have a lot of friends who I meet only once a year. But then we always have a nice time and exchange a lot of different view on science in the different fields.

By the way, the title of this blog was actually driven by a scientific talk. On one slide in a presentation on silicon detectors we (Frank and I) saw a picture of a silicon chip after dicing
and before it is attached to any other electronics – the speaker labeled that picture with “the naked die” …. our association was more in the direction of freezing in this building when not dressed sufficiently.

* PET positron emission tomography is a nuclear medicine imaging technique which produces a three-dimensional image or picture of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide (tracer), which is introduced into the body on a biologically active molecule.

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India-based Neutrino Observatory

Thursday, October 29th, 2009

News about India-based Neutrino Observatory

Several days ago I occasionally glanced at a rolling news on CCTV News Channel “…… will build the largest neutrino observatory”. I was shocked by my ignorance. Then I stood there for almost 10 minutes to wait it showing up again. Actually it is “India plans to build the largest fundamental scientific project —— neutrino observatory”. Many Chinese media reported this news. Generally it reads: “Indian scientist Mondal told media on Oct. 10 that India plans to start the construction of the Neutrino Observatory in 2012. The location is in Tamil Nadu in south India. He said, Indian scientists hope to collaborate with western countries, make neutrino beam with the accelerator in US or Europe and aim at the planned neutrino observatory in India.”

There was a workshop on neutrino factory on Oct. 12 in India. Prof. Mondal said above to media right before this workshop. The India-based Neutrino Observatory (INO) was proposed around 2000. The laboratory will be built 1300 meters underground. It uses 50 kton iron as target, interlaced with glass resistance plate chamber (RPC) as active detectors. It can be used to study atmospheric neutrinos as Super-K does, and can also serve as the far detector of a long baseline accelerator neutrino experiment.

There are many proposals and R&D on the next generation long baseline neutrino beam, such as beta beam and muon accelerator. It is generally believed that we need wait reactor neutrino experiment, such as Daya Bay, to give a clue on the mixing angle theta13, before determining which way we should go.

 

前几天偶然从CCTV新闻频道看到一行滚动新闻“… … 将建造最大的中微子观测站”。我被自己的孤陋寡闻吓了一跳,硬是站在电视前等了十分钟,等它再次滚出来,原来是“印度计划建造全国最大的基础科学工程——中微子观测站”。网上各大媒体也纷纷转载,原文大致是:

印度科学家蒙达尔教授10日对媒体说,印度计划于2012年开始建造中微子观测站,地址初步定在南部泰米尔纳德邦。他说,印度科学家希望与西方国家展开合作,使美国或欧洲有关国家的粒子加速器产生的中微子束穿透地球、抵达印度计划建造的中微子观测站,以便观测。

印度大约在2000年的时候提出了这个实验计划(INO),在地下1300米建立一个地下实验室,采用5万吨铁做介质,用玻璃阻性板探测器(RPC)与铁板一层一层交错叠起来,并加磁场,用以探测中微子反应产生的带电粒子。其探测器类似于美国正在进行的MINOS实验。MINOS实验的探测器是塑料闪烁体,将塑料闪烁体换成RPC,造价可便宜不少,同样的经费可以做得比较大,但是RPC需要通气体,维护比塑料闪烁体难,噪声也比较大。这样的观测站可以研究大气中微子,也可以做为加速器中微子实验的远端探测器。如果用来测量大气中微子,MINOS已经比较大地提高了日本超级神岗实验的精度,Nova和T2K也可以做,INO的精度跟它们差不多。如果做加速器中微子实验,则需要有人愿意把束流对准它,探测器的朝向也不同。出现这个报道的起因是10月12日要在印度开一个关于中微子工厂的国际研讨会。印度希望在CERN建中微子工厂,然后把束流送过来。

2005年我在意大利开会时碰到这个蒙达尔,盛情地邀请中国参加INO。我说我们首先要做大亚湾实验,大亚湾实验做好以前不会谈任何其它中微子计划。实际上,等MINOS,Nova,T2K做完,INO探测大气中微子已经没有太大的意义,探测长基线中微子则是没谱的事。beta beam和muon加速器(中微子工厂)不仅造价昂贵,远远高于INO的造价,关键技术也还没有解决,值不值得修建还要看theta13的大小,要等大亚湾实验的物理结果出来以后才知道。

趁此机会到维基百科上查了一下INO的介绍,很有意思的是大部分篇幅都在讲环保问题。INO选的点在动物保护区内,环评仍在争论中。

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ATLAS control room

Thursday, October 29th, 2009

In reply to Zoe’s post on pre-beam shifts at ALICE, I will tell you about these shifts in ATLAS. You can watch the shifters in the ATLAS control room live using the ATLAS web cam:

You can see me: thrird from the left, right in front

You can see me: thrird from the left, right in front

This is my first week of doing shifts and it is very exciting to be controlling a 50 million CHF device from a 100 meter distance. I mean: the thing is really down there, and if we push the button it really shuts down. It should be noted here that I am no shift leader (yet). I am trained to be an SCT shifter. The SCT is the silicon strip detector, a part of ATLAS’ inner detector. The SCT needs to be controlled all the time: the high voltages, its cooling, whether the strips are still active and configured and if its data are written to the database properly. We keep an eye on that.

In these pre-beam times, we take cosmic data, but as if the LHC is actually running. At some point the shift leader will ask us “are you ready for beam?” and we need to check that our detector is configured and pass over the data taking monitoring to the shift leader. Then we put the detector in a Stand-By status. This is the status it should be in when the beam is going to be injected later this year. When the shift leader tell us “Stable beam!” we can switch our detector from stand-by to ready-for-data.

This is me keeping an eye on the SCT together with the DCS-ducks

This is me keeping an eye on the SCT together with the DCS-ducks

Next thing you know, the cosmics start to appear on the big screen in front of us. It is really great. I am not sure if it sounds too exciting, but it really is. When the detectors are running we can perform all sorts of test to see if the SCT is still OK. Today, we have to run with a very high threshold, so we need to make sure the high threshold is not only set in system but also implemented down in the pit.

The eight hour shifts are now mostly used to see how the different detector parts start up and to train the shifters. By the time the LHC is running 24 hours a day, I don’t think an eight hour shift will be long.

The SCT is measuring cosmics.

The SCT is measuring cosmics.

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I am holding back on my Strangeness in Quark Matter conference blog, to take some time to tell you about what it’s like to do a shift for a high energy physics experiment that is weeks from start-up.  This is an experience that not too many people get in a lifetime, so it really should be documented! My shifts for ALICE started on Sunday, and I have been a shift leader for two days now.

DSC03662

That's me, highlighted in blue! 😀

The Birmingham group work on the Central Trigger Processor (CTP), which is a sort of nerve-centre at the centre of everything in ALICE. There are many sub-detectors that make up our experiment, and some of them can trigger on events. This means that when they see something that they like, they send a signal to the CTP saying so. The CTP then tells all of the sub-detectors that the event is interesting, tells the Data AQcuisition (DAQ), that the event will be taken, and sends it to a higher level trigger (HLT) for more a scrutinising selection process. The CTP’s job is a quite important one. Whenever the subdetectors want to run together to look for events (for now they are looking for cosmic rays passing through ALICE), a CTP shifter has to be around to set them up together and make sure the right detector is ready to trigger events. For the next few weeks, for eight hours out of 24, that shifter is me. And it’s rather fun!

My day-shift starts in the Alice Control Room (ACR), after a quick trip to the bakers at 7.30 and a brisk walk from my flat in St Genis. This is where most of the action happens. I arrive at 7.45am, catching up on the night’s progress and relieving the night shifter of their 8 hours. A run of (cosmic ray) data-taking from the night stops at around 8.30, ready for what we call “Happy hour” – a period for all subdetectors to play around individually, fixing bugs, checking their software works properly, making a few updates and so on. As a shift leader, it is part of my job to offer encouragement and/or fingerwag at people to make sure happy hour only lasts for an hour – there are many important tests that need to be done at a time like this, and “five more minutes” can easily turn into an hour and ruin the schedule if you aren’t careful! At around 9 I also need to make sure that everyone who is meant to be on shift is actually here. This has been a great way for me to get to know people on the experiment that I don’t see in my usual circles. It is especially useful for finding out who the experts are!

DSC03660

Beam updates, subdetector status, and important information are posted on big screens to keep everyone informed

For the past two days, there has been access to the ALICE pit (around 50 metres underground) so that various sub-detectors could be fixed, moved, have things installed, tested etc. It is also in preparation for switching on the L3 solenoid magnet (0.5 Tesla) that most of our subdetectors sit inside of. It is very important that any debris, metal or otherwise, is cleaned out and removed before switching on something as large and powerful as our detector’s solenoid and dipole magnets – you can probably imagine that our detector could be quite seriously damaged by a stray spanner or a metal pipe lying around!

As for the tests above ground, at the moment the main concern is to make sure that the subdetectors we need for early data (currently expected before the end of the year!) are able to trigger/read the events that will happen then. As well as setting up the triggering detectors for data-taking, the CTP can also send an artificial signals too, if a triggering detector isn’t available, or, like today, we want to recreate event rates similar to collisions and check that all our detectors can handle it. These are called Early Physics Running (EPR) tests.

cosmicsALICE

A busy looking ALICE event, reconstructed beautifully by the HLT, thanks to Jochen Thaeder for the pic!

Another exciting occurence this week was ALICE’s involvement in some LHC injection tests. I remember these tests taking place in August last year – I still have the photos. This time around, we are a much more prepared experiment. And I am a much more prepared student. I am almost grateful for the delays! The tests themselves have nothing to do with ALICE – they involve injecting high energy protons (and at one point, ions! YAY!) from SPS into the LHC tunnel. On the way, LHC dumps the beam into beam-dumps (essentially thick concrete blocks), forcing the protons to shower in the material, losing energy. These dumps are in place for safety, so that if control of the beam is lost during running, within 3 circuits it can be ejected into one of these concrete absorbers. Luckily (or unluckily, depending on how prepared we are), we are downstream from the injection point from SPS, and two of these absorbers. Earlier this week we were able to observe the shower. Hundreds of thousands of tracks. This is orders of magnitude more than what we expect even in heavy ion collisions! However, if the beam energy is not absorbed enough it can do great damage to detectors. Tests like this are very useful for us, but take alot of preparation.

DSC03658

A typical cosmic ray event, this time selected using the Time of Flight (TOF) trigger

Another responsibility as a CTP shifter is to train people. Because our group is small, and we need to cover 24 hours a day 100% of the time, we are rather short on numbers. It is quite fun going through the possible situations that a shifter could need to deal with, because once you’ve dealt with it you know what they are supposed to do. When you have to deal with a brand new problem first hand, it is a different, rather scary, story. You have to think on your feet and know when to give in and call an expert.  The main part of being a shift leader is being aware of what is going on, and knowing who to call in a crisis you can’t solve. This is easy on quiet days, but can be quite confusing on busy ones! I have very much enjoyed the experience, and hope that over the coming weeks it continues to be as exciting as it has been.

DSC03661

The LHC ring and status updates

I have many shifts still to come, and I now predict that I will be on nights (midnight to 8am) when we first get collisions. I am crossing every digit I own that I get to see it live (which makes typing tricky!) but even if not, I will be a very real part of the first collisions we take, and I can’t wait.

Heavy Ions in ALICE!

Heavy Ions in ALICE!

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Today is already the last day of the IEEE/NSS conference, at least for me. And contrary to what I promised, there has not been a blog entry on the conference yet. That is not really a bad sign, though: The conference is very interesting, with quite a few exciting new developments that are being presented here. And of course meeting colleagues is always fun, one of the main reasons to go to a conference after all.

Personally, the presentation I found most exciting was the development of a digital silicon photomultiplier by Philips… I think I have already written something about silicon photomultipliers (SiPMs) here at some point: Small silicon devices, that can detect single photons, and which are used in thousands in the CALICE prototype hadron calorimeter, and will be used in millions in a complete ILC detector. Now, the exciting thing about the new device is that it has a lot of intelligence already built in: It does not send out an analog signal that is proportional to the number of photons it saw, but a truly digital number. It can also provide information on the  timing of the individual photons, which might also be very useful for us. Now, the present first prototype the engineer from Philips presented is not yet fit to use in a calorimeter, but I had a quite long and very informative discussion with him about the prospects… Lets see where this is going, I’m definitely very interested to try out one of these new devices at some point! And I was not the only one interested in the talk: SiPMs are one of the hottest (if not THE hottest) topic at the conference: Apart from their application in highly granular calorimeters, which was actually the first large-scale use of these things, they are the coming thing in PET medical imaging. And that is of course a field where a lot of money is, consequently leading to a lot of interest. The room where the session was held was way to small, so mid-session the room had to be expanded, doubling its size, while disturbing one of the speakers in the session… And still people where standing in the doors.

Ingrid and me during lunch at the pool... Nice to be outside in the warm air!

Ingrid and me during lunch at the pool... Nice to be outside in the warm air!

Of course it’s not all work here… I met fellow Quantum Diarist Ingrid, and we just had lunch at the pool… The sunshine was a fantastic opportunity to warm up from the way over-airconditioned meeting rooms, the picture shows me with one sleeve rolled up, the other one still down to ward of the chill inside the rooms. That is something I never understand about conference centers in the US: I know AC is important to keep the humidity out, but if it is 30 degrees outside, sitting in a room at 18 degrees is just crazy. The fact that you have to bring winter clothes to survive a conference is just plain ridiculous. A large fraction of the attendees already has a cold… Another thing I don’t understand is why the conference is not able to provide a reasonable bandwidth for the internet connection. The reason I’m typing this post right now is that I’m waiting to download an important document I need to prepare a talk… A 10 MB pdf. Nowadays, this should be a matter of seconds, but here it takes 15 Minutes… IEEE conferences are notoriously bad with this for some reason, while most conferences I attended in the last years have provided excellent internet connectivity. Everybody here has a laptop, and we all need to check email from time to time… The slow network just leads to a lot of wasted time, I’ve already missed some talks because of this.

Still, the scientific quality, and of course the many interesting discussions, far outweigh these problems… Definitely a worthwhile event!

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Random encounters

Thursday, October 29th, 2009

Not trying to open up a quantum diarists “travel off”, particular given some of the posts Ingrid and Frank have put up in recent months regarding their away from home shenanigans I wanted to mention a peculiarity I realised yesterday. During the last week I was back in the bay area visiting SLAC, which is always a great pleasure as I have many old friends and colleagues there, and spending a couple of days at LBL, starting to learn some new hardware I hope to work on as part of the inner detector upgrade for ATLAS. A very productive trip. On my way back I flew on United. As a US department of energy employee I have to fly on a US carrier whenever there is a chance to do so and United is usually a safe bet, given they now have a flight from Geneva to Washington-Dulles. So, while strolling through Dulles (that I have now taken to calling “Dullest” due to it’s lack of flair and general drab decor) I saw a fellow physicist who was on her way to a meeting in the US. She was as surprised as I when I interrupted her and said hello. We chatted about physics, unsurprisingly, and the state of our mutual endeavours for a few minutes and then parted ways, off to catch our respective flights. While walking away I then bumped into another physicist I know, this time only exchanging a brief hello as it’s fair to say it seemed a bit weird to me to bump into two people I know in a large airport within seconds of each other.

This happens often when people are leaving Geneva or all going to or from the same conference, but it’s much less common to just happen across someone while traversing the globe. If it wasn’t for physics I could pretty safely say that I would not be bumping into people I know in Washington airport, one of the many quirks of the quarks.

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Back to school

Thursday, October 29th, 2009

I made a trip ‘home’ a couple of weeks ago for a less than pleasing family related reason (my mother was in hospital for an operation). Although I haven’t lived in the same country I grew up in for well over a decade now, a trip back to England is always exciting to me. I landed in Manchester and after visiting the hospital there for a few days I took advantage of being close to where I grew up, and went back to my old school. Not for any sinister reason like putting a brick through a window or writing graffiti on the walls, quite the contrary in fact. I contacted one of the teacher’s at the school who has recently been pushing teaching particle physics to year 12 and 13 students ( a new terminology for me, but apparently it means they are between 16 and 18 years old) and he was delighted to have me drop by and chat with them a bit.
In fact the school have arranged for some of the students to visit CERN later this month and so my timing, although inadvertent, could not have been better. I met a teacher at the reception (which felt more like ‘security’), signed in and was immediately whisked away into a class of adolescents. I was then plonked in front of them and apparently expected to inspire them to take up a career in physics. During those first few moments a strange feeling came over me: I was nervous. Actually really quite a bit bloody nervous if truth be told. I’m a good public speaker, confident in front of people and have no trouble standing in front of a room and speaking about, well, anything actually. But in front of this room of students, without the comfortable sofa of a well-prepared set of powerpoint slides to fall back onto, I was a bit shaky. In hindsight it was because I really felt that this mattered. Nobody came in and talked to us about opportunities like this when I was at school there. Nobody told me I could get a job in another country, do research into something I thought was interesting, work the hours I choose to and with people who stimulate my thoughts on things. So there I stood, growing back my confidence as I went on about my own career and the work at CERN to the ever eager students. At some point, I shut up, and sort of smiled at them and asked if they had any questions. Occasionally a death knell I was welcomed by the raising of many hands and a few chuckles. So, one-by-one we went through what they did and didn’t understand. If they said that the thought they shouldn’t ask a question because it was stupid I convinced them to ask it. None of the questions were stupid. In fact they were a well informed group of young people who have already been taught some useful concepts in quantum mechanics and particle physics. I took the often asked question of “How much money do you earn?” to be a thinly disguised version of “I’m kind of into this whole working in physics thing, but want to know what I will get paid before I decide whether to do it or not.”

The whole ‘outreach’ thing can comes in many guises but for me, none could be more satisfying than going back to your old school to help them out a bit. Maybe one day a future particle physics will go back and reminisce about the day they were inspired into the field by a former student.

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Wow, what a terrible trip to CERN I’ve been having. I’m here for the semi-annual CMS computing and offline software workshop week, but I took ill while here and have been confined to my room in the hostel for the past two days. That and my jet lag have totally put me off my game. I am definitely on the mend now and expect to be out and about today, and that will be a great relief. Thanks to all of our modern devices, I could keep up with what was going on in official meetings from my room, but I could have done that from my office in Lincoln too — the point of coming here is to see my friends and colleagues face to face and for us all to talk about what is really going on and what we should be doing about it. You don’t always learn that from the talks in the meetings; it’s all about the hallway conversations and the extended lunches (and those long periods of watching other people drink coffee that I’ve written about before).

But what I can see, even from inside, is the growing level of intensity as it becomes clear that the LHC restart is upon us. Seth of course mentioned earlier this week that particles were injected into the LHC over this past weekend, for the first time since last September. He didn’t mention that it wasn’t just protons injected, but also lead ions, and I think this was the first-ever injection of heavier nuclei into the LHC. With that done, fully circulating beam (making a complete circuit of the machine) could come as soon as next weekend, and that means that the detectors must be totally operational now. Even with only one proton beam (not colliding with another beam) there is a lot to learn, as we saw last year — you can see particles from the “beam halo” streaming through the detector, and also “beam splash” events. All indications are that we will have some kind of collisions, although probably at relatively low energies, before the Christmas shutdown. Then the pressure will be on the experiments (not the accelerator!) to quickly turn around and show that they can do something sensible even with the small number of collisions that we will probably get at first. Well, this is what we’ve spent twenty years preparing for — we must be ready.

It’s hard to believe that it’s really happening.  Let’s hope it seems as real after I finally get home, tomorrow night, and get some proper sleep.

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What is a Grid?

Wednesday, October 28th, 2009

In a previous post, I mentioned that ATLAS will be collecting enormous amounts of data, approximately 6 Petabytes/year (i.e., 6,000,000 Gigabytes). How in the world are we going to handle it, and how do we make it available to all physicists on ATLAS? I spoke to one of my colleagues at Indiana University, Fred Luehring, who has major responsibilities for the US part of the Grid, to get some details.

First, let me mention some ATLAS jargon; if you wish, you can skip this paragraph for now, and come back to it when you run into strange acronyms.

The raw data that we collect is called ByteStream, basically, it is a stream of 1’s and 0’s, and is approximately 3-6 Megabytes/event. This gets “massaged” into Raw Data Objects (RDO); the only difference is that the data now has a “structure” that can be analyzed with software written in C++; it is now about 1 Megabyte/event. At this point, the ATLAS reconstruction software (written in C++) runs over these RDOs and produces tracks in the inner detector, electron and muon candidates, jets, etc., and outputs two other structured formats, ESD (Event Summary Data), AOD (Analysis Object Data), which contain different levels of detail; they are approximately 500 Kilobytes and 100 Kilobytes/event. As you can tell by the name, most physicists will run on AOD’s; there are other smaller formats, but I will skip them.

In a “normal” year, we expect to collect about 2 billion events. How do we handle all this data? To do this, physicists and computer scientists have been working on the Grid. It is basically a whole lot of computers spread all over the world that are networked with very fast connections; typical data transfer rates are 1-10 Gigabits/sec (in contrast, broadband connections to your home are about a thousand times slower).

You may ask why we need the Grid. Why can’t all the collaborating institutes just buy computers and send them to CERN, and let them set up a gigantic processing center? That is one approach. However, funding agencies don’t like this mode of operation. They would much rather keep the hardware in their respective countries, and build upon existing infrastructure at universities and laboratories, which includes people, hardware, buildings, etc. Another advantage of the Grid approach is the built-in redundancy; if one site goes down, jobs can be steered to others. Also, if a Grid site is appropriately configured, then if ATLAS is not using the computers, other scientists can use them (in an opportunistic manner); although, we keep the system pretty busy. In the US, each LHC experiment has its own grid sites, whereas in Europe, they tend to share them.

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