News

Bikes

If your lab is far and if you stay for the summer (which I highly recommend by the way!), you need to follow a few tricks for keeping your CERN bike past the 3 month loan period.  After the first 3 months, the bike shop will let you renew the loan for another month one or two times but towards the summertime, the bike suddenly becomes highly coveted for summer students. So beware and keep your bike away from the bike shop and out of plain view (i.e. don’t even park it outside main buildings because people will come around to check the racks for bikes that are past their loan period and confiscate them).  Even if something is wrong with your bike do NOT bring it to the bike shop or it’s doomed.  I had my bike taken away when I tried to get the gears on it fixed and other people (including Larry himself) had their bikes taken right from their racks.

P.S. if all this seems too much of a hassle, just try to buy a used bike off the CERN market or through local friends as soon as possible.  If you manage to sell it by the end of the summer, it might not even cost you anything.

UNIGE Classes

Do:

-Research the European University system before you come to Geneva.  It’s very, very different than what you’re used to. Teachers will not coddle you at all, homeworks don’t count for much, and your entire grade will likely depend on a grueling 4 hour final exam (possibly an oral exam too).

-Attend most, if not all the lectures.  It’s the best way to keep up with all the material and know exactly what you’re expected to know.  You WILL be tempted to skip classes especially if the French phases you but try to at least follow along in the textbook during lecture.  Chances are the lecture will follow the book pretty closely.

-Ask the professors and TF’s as many questions as you need.  The professors don’t hold office hours but you can meet with TF’s outside of classes and talk to professors during the 15 minute breaks in the middle of class or before and after class.  They are happy to clarify concepts in English.

-Talk to your classmates. They know how the system works and can give you some pretty helpful tips.

Don’t:

-Put off or not do homework.  Attempt ALL of it even if you don’t need to.  It’s the best practice for the final, I promise.

- Underestimate the final. Keep up with the work through out the semester or you WILL panic for an entire three weeks before the final.

Goodluck!

Research at CERN

Just because most people’s minds immediately go to the Large Hadron Collider when they think of CERN, doesn’t mean that’s the only project at CERN.  It’s true that the main focus of CERN is LHC particle physics but an amalgam of smaller and larger labs also research things like medical physics, clean energy, and antimatter.  If you have any particular interests, do your research!  Larry has crazy connections and can probably get you into any lab at CERN if you want it badly enough.  Thanks to that, I now work in a medical physics lab developing medical imaging systems to work with cancer radiotherapy.

Hope this helps!

-housing in Geneva is expensive. the best deal is with the CERN hostel in St. Genis, however it gets fill rather quick and a few months before summer they reserve the spaces for the summer students so, as soon as you get your CERN IDs  book it if you know your staying. this will save you hassle and money.

-Also there will probably be a lot of drama with the flights. BU pays for a group flight which leaves June 30th-ish. if you plan to say longer many people found that it was cheaper to get the refund for the flight and book it your self. However, if you know you want to stay during the summer then as soon as you get your study abroad package that has the info for the flight, call up the travel agency that BU has the deal with and have them immediately change the return date. also when you are accepting your flight there is a option to request later return date that makes this process easier.  you can always change  the return date of for a price of course and it gets ridiculous quickly.

The Experiment:

NA62 is attempting to measure the branching ratio of the positive Kaon to positive Pion plus neutrino/anti-neutrino pair decay (meaning that the positive Kaon turns into a positive Pion and a neutrino/anti-neutrino pair). A branching ratio essentially tells us the frequency with which such a decay will occur. These can be measured or predicted by the standard model. For the Kaon decay NA62 is looking at, the branching ratio is about one in ten billion. This means that, one in every ten billion decays of a positive Kaon particle will produce a positive Pion and a neutrino/anti-neutrino pair, very rare.

The experiment consists of 8 modules, each module has 224 straws, half of which run perpendicular to the other half. The modules look like this:

One view of the module with 112 straws showing.

There will be 8 of the these modules lined up along the beam line, each one represents an individual tracker. The straws in each module, that’s 224 straws, represents both an X and a Y coordinate. One set of 112, is aligned in the way shown in the picture and the other 112 are aligned perpendicularly, above the first set. This arrangement allows for the X-Y plane to be drawn, which is important for performing track reconstruction on the incoming particles.

The detector, as I’ve said, has 8 modules, but each 2 modules creates a view, so the detector has a total of 4 views. This is to provide more robust and accurate data; each view consists of 2 modules rotated forty five degrees from one another. So if one module represents X-Y then the rotated module represents a new set of coordinates, called U-V. With another set of coordinates, we can achieve much more accurate measurements of the particles position and therefore our track reconstruction becomes considerably more accurate.

The detector is of the gaseous breed; we use an Argon/CO2 mixture with a high voltage tungsten wire running down the center of each straw. In general, charged particle will enter the gas region of the straw; this will cause electrons to be knocked off in a statistical pattern. The wire running down the straw is set at a certain voltage (with the edge of the straw set to ground), so the electrons will accelerate under the incident electric field. This acceleration will cause more electrons to be knocked off, causing an electron cascade. This will then be read off by the electronics connected to the center wire.

Each straw then represents either an X or a Y coordinate (depending upon the orientation of the chamber relative to the path of the particle). Since the straws in the X direction are going to be in front of the straws in the Y direction, any particle that enters an X straw will also, inevitably, also hit a Y straw, thus giving us our X,Y position. The same logic holds true for the U-V set of coordinates.

That’s the gist of the experiment; there are, of course, many more intricacies that I haven’t relayed in this post. Below you’ll find a link to more documentation and my email address if you have any further questions.

My Contribution:

So up until now, I’ve been explaining the whole of the NA62 experiment, but I haven’t mentioned what my actual contribution is. I have been working with the prototype of the NA62 straw tracker (the modules) and of an independent tracker called the MicroMegas detector.

• Straw Prototype:

A prototype of the main detector; using the same technology and principles.

Here’s the prototype:

The Prototype (cylindrical object).

The straws in the prototype run parallel to that length of it, each one also filled with the aforementioned Ar/CO2 gas mixture. The straws in this prototype operate exactly like the straws in the main detector. Each one has a wire running through which reads off the electron cascades, giving us a coordinate. Although we do want to test this prototype, the physics behind it are fairly well understood (the creation and implementation of the software is where all the work went into the prototype).

However, we have the MicroMegas independent tracker:

• MicroMegas Detector:

The MicroMegas (herein, MM) is a detector that operates completely outside of the prototype straw detector. It has two stations each comprised of two chambers; the stations sit on either side of the prototype (in the picture above you can see them below and above the cylinder). Each chamber consists of four major components: the stainless steel drift, the gas chamber, the mesh and the read-out strips. The drift is set to a certain potential (-900V) and the mesh is set to a different potential (-500V); in between these is the gas chamber. So, like in the straw detector, the particle enters the gas chamber and knocks off some electrons. These electrons are accelerated toward the mesh. The mesh, being permeable, allows the electrons to pass through into the another gas region, but this region is tiny compared to the main gas chamber, but the potential difference (since the strips are at ground) is 500 volts. This causes a fairly large electric field which massively accelerates the electrons, again causing an electron cascade. These electron cascades (as there are multiple for each particle) are then read off by the electronics (the strips).

Here’s one chamber:

One MicroMegas Chamber

The description I gave works best if you visualize the chamber in the transverse direction; that is to say not top down but rather a side-on view.

At this point, some of you may be wondering how we know to collect data. We can’t see the particles. Even if we could, they’re traveling at close to the speed of light, so every time we’d notice one, the particle would be halfway across the world before we could hit the button to try to record it. So we need something that can automatically trigger the data collection when it senses a particle, and it has to do it fast.

The black box you see on top of the chamber is the solution, it is called a scintillator and essentially what it does is wait for a particle and when one enters it, it emits an amount of light. That light is then read into a bunch of electronics which tell the computer to start collecting data and all of this happens before the particle enters the gas chamber (which is directly below the scintillator). We call this process the trigger (since it triggers the data collection).

Each MM chamber is either an X or a Y coordinate, depending upon it’s orientation, the green boards in the picture are oriented parallel to the strips, when a strip is hit, it reads out and that would be considered an X or a Y. Then the particle enters the second chamber (below the first) which is oriented 90 degrees from the first chamber. The same thing happens and we get our Y coordinate. Putting these together, we have an X-Y plane with the coordinate of the particle. Two of the chambers, separated by a meter or so will give us two X-Y planes. So, we have a particle that hits the top two chambers (producing an X-Y coordinate) and then the bottom two (another X-Y coordinate) and a separation distance. We can use this information to recreate the track the particle took. It is possible for a particle to hit the first station and miss the second, but in the lab we used cosmic rays (charge particles from space) which, for the most part, are relatively orthogonal to the planet’s surface.

• Software:

For both the MicroMegas and for the Straw Prototype, we had the daunting task of developing the software that takes the collected data and expresses it in a form that we can actually use. This entailed decoding the data so that instead of having just counts of electrons (since that’s really all we get), we have things like millimeters or charge units. We have to take the raw data and turn it into something useful. Then we take that data, calibrate the the chambers (essentially find out how the software reads some of the dimensions of the chambers) and perform track reconstruction. This means that we construct the path the particle takes to travel through the detectors. All the software is written in C++ and ROOT.

Test Beam:

In order to test the prototype more effectively, we ran the detector in the test beam and collected data from there. Here is our prototype set-up in the test beam area:

The Prototype in the Test Beam Area. My fellow BU student, Kevin Merenda is on the left left and my friend, Tan Hong-Qi, a student from Singapore is on the right.

The test beam is a particle (hadron) beam which we have some control over and runs at 120 GeV. This beam is taken from the SPS (Super Proton Synchrotron). Having the beam is incredibly useful because it allows us to get hundreds of events in mere seconds whereas when using the cosmic rays, we’d have to collect data for days in order to get a couple of thousands of events. Also, with the beam, we get particles streaming into the chamber that are collimated (meaning the beams of particles are parallel) which allows our software to be more accurate and thus our results are considerably more robust.

Once we’ve tested the detectors, our software will become apart of the full NA62 software package and will run alongside many of the other pieces of software produced for the main experiment. If you wish to know any more about the experiment, you can go here and you’ll find more documentation or you can ask me directly at redcoat@bu.edu.

-Bertie Wright

Again, upon Larry’s request, and for those who want a pdf of their unofficial transcript:
Go to https://my.unige.ch/
Click “Proces-verbal examen”
Under “Faculté des sciences,” you can check your Unige grade on “PV Examens” link.

Here is also the grade conversion scale:

Dasom

In reference to UniGe classes:

-Look at the curriculums of the courses and choose what you want to take as soon as you get accepted. I go to Williams College and we have a different curriculum than BU. I ended up taking Quantum Mechanics at UniGe and my school and repeating a class is one of the most frustrating experiences one can have academically. If I had spoken up earlier (ie in September) about wanting to take another course in place of QM, I think I would have gotten a lot more out of my classes this semester. That being said, anyone who doesn’t go to BU shouldn’t be deterred from applying to this program – I think it has a lot to offer for a physics student from any university.

-The TAs are there to help you and are a lot more approachable than you think. I didn’t meet with them until the very end of the semester and wish I had met with them more to discuss homework questions during the semester. It’s their job to help you and make sure you understand everything, so use their knowledge to your benefit.

-Study during the semester – don’t slack off on your homework just because it’s not due and doesn’t have a grade. I was really focused on research and prioritized that over my classes, which is a decision I definitely don’t regret. However, studying for finals was extremely stressful (your entire grade depends on the final) because I had managed to do most of my hw in one class but only about half in the other class. If I had been studying harder for my classes during the semester, even just a couple more hrs per week, I wouldn’t have had a miserable 9 am to midnight in the library for two weeks finals period. I did do well in my courses but I would have felt a lot more comfortable going into the test if I had been studying all semester.

-Talk to the UniGe students. It’s wonderful to meet people from different countries and nice to have friends outside of the program as well. I didn’t get to know them until near the end of the semester and wish I had reached out to them sooner.

-When you do end up studying for finals, outlining the book and going over problem sets/past exams/practice exams was one of the best ways to study, for me at least. For orals, talking over the main concepts of the class and anything your professor asked you to focus on is really helpful – get two or three people together and teach each other things on the blackboard. In the oral exam, act confident, although steer away from cocky, and you’re likely to do well.

In reference to research:

-Choose an adviser who does something that you’re interested in but also try to choose an adviser who will have time to speak with you and help you out. My mentor was always available if I had questions and his graduate student was very helpful when I had questions about my code, which made research so much more enjoyable and productive.

-Don’t be afraid to talk to a bunch of people about what research you want to do in the beginning. After a couple weeks at CERN, you’ll have a couple contacts. Email them, set up meetings, or if you don’t know many people just ask for recommendations of who would make a good mentor. The experience of looking for a mentor is definitely part of your time at CERN, so take full advantage and don’t choose someone just because you don’t want to spend time exploring all of your options.

-Don’t be afraid to ask questions – you’re not expected to know everything about high energy physics, coding, hardware, etc and the easiest way to learn is to ask when you don’t understand.

-Attend meetings, go to conferences (I went to a high energy physics conference in Warsaw, Poland – one of my best trips the whole semester), do as much as you can while here. This program offers you the opportunity to immerse yourself in high energy physics in a way you can’t arguably anywhere else so you should take advantage of that as much as possible.

In reference to life here:

-Travel around Switzerland if you don’t have time/money to travel around Europe – it’s cheaper, you can take day trips, and Switzerland contains a lot of diverse areas from the Alps to the Italian part to the capital etc. Also take advantage of program planned trips – they’re much less expensive!

-Before you leave to come here, reflect on what you want to get out of the program. It helps to know what you expect to come out with and to revise that as you go along. I wish I had spent more time doing that – I dived into the program and didn’t really think too hard about it until a month or two in, when time had already passed.

-One of the easiest ways to cope with the change of moving here/meeting a bunch of new people is to find a way to do an activity that you normally participate in at home. CERN and UniGe offer many clubs – I joined the CERN Jazz Club because they granted me access to a piano, which allowed me to play whenever I wanted. I know other people who did a lot of outdoors activities, found a dance school to take classes at, found a church they enjoyed going to in the area, etc. It provides some sense of consistency with what you were previously used to and a venue to meet new people as well.

I couldn’t be happier with my time here – whether good or bad I learned something from every experience I’ve had this semester. If anyone has any questions about the program  I’d be more than happy to answer them – just email me at aas1@williams.edu

-Alice

Upon Larry’s request, and for the future reference:
the following was our exam schedule for this semester.

6/6 EMII written exam: 8:30am to 12:30pm, 4hrs, at Science I 306
6/8 EMII oral exam: 8:30am to 15:30pm, 25min/each student, at Prof. Buttiker’s office
6/14 QMI: 8:30am to 12:30pm, 4hrs, at Science II 300

Hi all,

I’m an alum of the program from the first year it started (2010), so bear in mind that it’s completely possible that my advice concerning this is outdated. However, here are my thoughts on it now looking back:

1) The level of required preparation beforehand will obviously depend on the structure of the exam. For our EM class (Prof. Pohl), the list of possible topics was given to us ahead of time, but the material we could bring was limited (could be wrong on that…feel free to correct me, older folks). For our QM class (Prof. Blondel), the topics were not given, but we could bring any material we wanted to prepare. We were given 20-30 min prep time for both classes (don’t remember precisely). In any case, obviously use what you’re allowed to your advantage.

2) You don’t need to memorize the book. Give a “spark notes” style outline. You don’t need to provide anything fancy. The professor wants to see how well YOU know the material, not how much the author of the book knows the material. I would suggest first to imagine you are explaining it to your parents (assuming they aren’t experts in the fields themselves) and build up the level of detail for your personal understanding from there. Use further detail to answer questions that the professor asks. You don’t need to give an all-inclusive lecture!

3) In your oral exam, I recommend you maintain composure and go at a slow and comfortable pace. It’s a very informal setting; you will get interrupted and asked questions in the middle of your presentation! They likely will not try to intentionally derail you (at least they didn’t to me). The questions will likely be more of a clarification than anything else. In any case, if you proceed at too fast of a pace, you will likely lose yourself when you are interrupted. This was a mistake I personally made. Stay relaxed, you’ll think more clearly.

4) We all passed! I know I personally tripped up a little bit like I said before, but none of us failed and most did very well. I promise you will survive. We were all nervous and scared of it too.

I hope that helps some. Good luck!

-Michael Hedges

P.S. If you have more questions, feel free to email me at mhedges@hawaii.edu Just keep in mind that the time change is 12 hours, so I probably won’t get back to you until the next day.

If you are looking for summer housing, check out the following links :

http://www.unige.ch/dase/bulog/form/bourse.php     (the UNIGE housing- I found this to be the most useful!)

https://espace.cern.ch/hostel-service/Wiki%20Pages/Hostels.aspx   (the CERN hostels- they are expensive!)

https://espace.cern.ch/cern-market/default.aspx      (click on housing on the left and login with your cern account)

Best of luck!

The names and emails of our professors for this semester are:

* Markus Buttiker Markus.Buttiker@unige.ch for electrodynamics II

* Corina Kollath Corinna.Kollath@physics.unige.ch for Quantum Mechanics I

This post will be further updated to include Group Theory and Particle Physics professors later.