Safety at CMS

Though you are allowed to go down and see CMS on a guided tour, you have to go through a long process to be down there for any length of time or go near to the detector. This is because it is an extremely dangerous machine in an extremely dangerous environment.

CMS has a number of very fragile pieces, including the beam line. You wouldn’t think that a steel pipe, even though it is narrow, would be in danger of being damaged, but here’s the problem: the beam of particles in the LHC is so precisely aligned, that if the beam pipe gets shifted by a millimeter or less, that can cause particle in the beam to hit the pipe, which creates a lot of stray, unwanted radiation.

That square tube in the middle is a casing for the beam pipe. They really don’t want anyone to bump it on accident! Original picture.

In addition to being careful of the mechanical pieces, one must look out for high voltages and magnetic fields. There are voltages of over 10,000V present when CMS is turned on, which won’t necessarily kill you (but it could), but it would certainly hurt, regardless.

Original picture.

The 4 tesla magnetic field, when it is turned on, is enough to destroy phones, credit cards, etc. if you get too close.

And that’s only the detector itself! The collisions create lots of radiation, which contaminates the cavern. While the beam is on, it is enough to make your death extremely probable. When the beam is off, there is still residual radiation that gets absorbed by the material in the experimental cavern.

The LHC is cooled with liquid helium and nitrogen, so if there were ever a leak, you would suffocate because the liquid will turn into gas, which displaces the oxygen in the air.

That cloud on top is helium gas.

All of these dangers means that you need to be sufficiently trained to avoid or deal with them before you are allowed to work in the experimental hall. You have to take a handful of online courses going over a number of safety measures, as well as attend training sessions in person. I had to take a class to lean how to use a self-rescue mask in the case of oxygen deficiency. To pass the class, I had to put on my mask in under 40 seconds in a realistic setting inside a mock-up of the LHC tunnel. I also have to attend a full-day course on radiation safety. In the near future, I will be going to a class to learn how to operate various different kinds of fire extinguishers. Valuable life skills, right?

Yes, I got to look that dorky too.

It is not until you have passed all relevant classes that you can then obtain the necessary equipment to enter the cavern. You need a hard hat, steel-toed shoes, and your CERN ID card.

Original picture.

You also need your personal dosimeter. This is a device that tracks how much radiation you have received, to make sure you haven’t gotten too high of a dose.

Original picture.

Finally, you get a biometric scan, so that you can get through the security doors.

Original picture.

But it is quite a reward when you get to see all of it!

Original picture!

What is CMS?

Hello everyone! I am so happy that you are interested in particle detectors, and CMS in particular. If you are very new, I would recommend reading up on particle physics and the LHC first.

Otherwise, if you’re ready, we can continue!

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What is a particle detector?

A particle detector, on its most basic level, is exactly what it sounds like: it is a machine designed to detect high-energy particles which pass through it. Particles are far too small to ever actually see them with our eyes, so we need to use machines to alert us to their presence. The particles pass through material in the detector and interact with it. We then can observe the changes of the detector material, which gives us information about the particle itself.

The materials used in these detectors varies widely, because different materials interact differently with different particles and so can tell us what type of particle is passing through. Some detectors use gas, while others use liquids. Crystals (below, bottom) and semi-conductors (below, top) are also common materials.

These materials can also be used in a number of different ways in order to tell us different things about the particles. For example, calorimeters can tell us the energy of a particle while trackers are better at telling us the position.

Due to all these differences, it is very important to select the proper type of particle detector in order to achieve the goals of your experiment. Many projects may use multiple types within one experiment.

There are some detectors that are small, basic, and cheap enough to build in your own home! There are others that are small, but very precise. There are also some the size of houses, while still others are miles long (like the IceCube project, pictured below).

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What is CMS?

CMS, which stands for Compact Muon Solenoid (I’ll explain the name in a bit), is one of the four main particle detectors which runs at the LHC. The other are ATLAS, LHCb, and ALICE.

What does it do?

I have often heard the purpose of CMS compared to smashing a watch. Imagine you have a watch, and you would like to know how it works. First, you would likely observe the watch an see how it behaves over time. Then you might make predictions about how the watch will continue to act in the future. This is what theoretical physicists do. But if you really want to find out about how the watch works at the deepest level, you can shatter the watch and then examine the pieces that come out. By examining the pieces and seeing how they might have fit together, you can deduce how it works.

CMS does much the same thing, except that instead of watches, it uses particles. It detects all of the particles that come out of collisions at the LHC, so that we can learn about the fundamental constituents of the universe.

Some scientists don’t like that analogy, because we are really more interested in what the pieces of the watch can (and do) combine to make. One physicist puts it, “It is more as though we smash watches together in hopes that a cellphone will appear out of the collision energy.”

What does CMS mean?

So that sounds and looks like a huge machine! Why is it called compact? That is easily answered when it is compared to its sister experiment, ATLAS.

Photo credit to Piotr Traczyk.

As I mentioned in the previous section, some detectors are better at finding specific particles. The ‘M’ in CMS stands for muon, which is a type of particle that CMS is particularly good at finding.

Finally, the ‘S’ in CMS stands for solenoid, which is a particular type of magnet. Now this magnet is truly ridiculous. It is the largest super conducting magnet ever built, and weighs over 12,000 tonnes. It operates at a temperature that is one degree warmer than outer space, and produces a magnetic field of 4 Tesla, which is 100,000 times stronger than the earth’s magnetic field. It has to be built strong enough so that its own magnetic field does not rip it apart, so it contains almost twice as much iron as the Eiffel Tower!

The magnetic field curves the path of the particles that pass through it, and has a stronger effect on particles with more momentum. So based on the curvature of the particle’s path, we can deduce the particle’s momentum.

How was it built?

Construction of CMS actually began back in 1998, and it was ‘finished’ in 2008. Of course upgrades of the detector will never really be finished, so it is still under construction now, in a sense. The whole thing is 70 feet long and 52 feet tall. It weighs almost 14,000 tons! Over 3,000 scientists from about 200 institutions in 39 different countries collaborated to design and construct it.

Note the person in the bottom center, for scale.

One of the most difficult and expensive parts of the project was digging a cavern in the mountainside, so that CMS could be placed underground. Once the cavern had been built, CMS was lowered 300ft in to the ground, piece by piece.

The project cost was around $1 billion dollars. Now that sounds like a lot, but let’s put it in perspective: you could build two of these detectors for the same amount that the U.S. spends on one B-2 stealth bomber.

The layers of CMS

CMS is kind of like an onion – there are lots of layers! The goal is for no particle to pass through this series of layers without being detected. Since different detectors are good at seeing different things, many different layers are needed. They are, from the inside out: the tracker, electromagnetic calorimeter, hadronic calorimeter, and muon system. A schematic can be seen below. There are a large number of other, smaller subdetectors, but these are the main ones.

Tracker:

• Material: Silicon pixels and strips
• Purpose: Precisely reconstruct the tracks of muons, electrons, and charged hadrons

Electromagnetic Calorimeter:

• Material: Lead tungstate crystals
• Purpose: Measure the energy of electrons and photons

Hadronic Calorimeter:

• Material: Brass, steel, and scintillating plastic
• Purpose: Measure the energy of hadrons
• Fun fact: Much of the brass used in this detector comes from old Russian artillery shells

Muon System:

• Material: Metal tubes, filled with gas
• Purpose: Track and measure the energy of muons

So here’s the tricky part: getting all of it hooked up! I have found that it is difficult to determine just how many cables went in to CMS. The best estimate that I can come up with comes from a technician who worked on the cabling of the muon system, which I am going to say is about one fifth of the whole detector. He calculated that there are approximately 1400 kilometers of cables in that section. That means that there are about 7500 kilometers, or approximately 4500 miles, of cables in the detector! When you see things like the picture below, you start to believe it…

You may notice that all these cables are held together with zip ties. Some quick math will tell us that a zip tie is placed about once every 30 centimeters (1 foot), but that it usually holds more than one cable. We can say this averages to one zip tie for every meter of cable. This leads to the realization that there must be around 7.5 million zip ties in the experiment! I once heard it said that the person who had made the single largest contribution to physics was the person who invented zip ties. Now I am starting to believe it!

How do you deal with all that data?

Particles collide in the center of CMS 40 million times per second. This means that the electronics on the detectors have to be able to read out data once every 25 nanosecond (or 25 billionths of a second). That’s fast! Getting everything to work so quickly and so precisely is quite the challenge.

Usually, there is actually more than one collision at a time since it is actually bunches of protons being accelerated towards one another. So there are typically around 600 million ‘events’ happening per second. The raw data for one event is about one megabyte, so that comes out to be around 600 terabytes of data that the electronics have to read out every single second.

However much we would like to be able to save all of that data, it just isn’t possible. To cut down on the volume we use something called a trigger, which is basically a process which tells us which events are interesting enough to keep and analyze and which are not.

This process actually happens twice. The first time, the data is cut down from the 600 million events per second that the detectors pick up, to around 100,000 events per second that are actually reconstructed. Then, more advanced algorithms are used to pick out 100-200 interesting events per second. These events are then written to servers at the CERN Data Centre at a rate of 1 gigabyte per second.

All of this amounts to about 5 petabytes of data a year. To analyze all this data, a worldwide computing network is used, and then the data can be accessed by scientists all over the world.

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So that’s about it! If you have any further questions, please let me know!

The City of Geneva – Part 1

Last weekend, we spent a few hours in Geneva on Saturday afternoon. Geneva has a lot to offer, and that’s why this post is titled ‘Part 1’! We barely scratched the surface, so I know we will be going back.

We got there and parked in an underground parking lot very close to the lake. That was nerve-wracking. Cars here are much smaller on average. That means that the roads are very narrow, and the parking spots are tiny. I wasn’t good at parking to begin with, and now I have to do it in a manual?? I just usually make sure to park faaaaar away from everyone else…

But we got out of the car and made our way towards Old Town. It is a similar concept to Old Town in Annecy – older buildings, winding streets, surrounded by Geneva’s original wall that defended from invaders.

One of the main attractions in Old Town is St. Peter’s cathedral, so that was our first stop.

The cathedral was built between 1160 – 1252. The interior has been restored a number of times, but some original things remain – like the pulpit.

Geneva was the center of the religious movement called the Reformation, while it was going on during 1517-1648. The Reformation represented the divergence of Protestantism with the Roman Catholic Church. Behind Martin Luther, John Calvin is probably one of the most well-recognized leaders of this movement, and his chair is on display in the church.

The main body of the cathedral is free for everyone to visit, but you can also climb their towers for the small fee of 5 Swiss Francs (CHF). The towers are very narrow, and very tall. That means stairs all the way up! And they were just the most narrow stairs you have ever seen!! They were so narrow that there was a stoplight at the top that told you when you could go, because two people would not be able to pass each other!

I learned from my professor that the stairs always curve upwards to the right, so that you can defend yourself with you sword hand as you are going up the stairs. Who knew?

On the way, we got to see the bells of the tower. There were five of them, and some were impressively large! They were behind bars though, and didn’t make for any good pictures.

Up on the higher tiers of the towers, we were treated to 360° views of the city of Geneva and the lake. It was quite beautiful!

The steeples of the church were also very impressive. I learned that nothing in Geneva is allowed to be built taller than the cathedral. It’s tall, but not THAT tall, so you won’t find any skyscrapers in Geneva.

The church was actually built on the site of another church, which was built in the 6th century. So beneath the church, you can actually visit the archaeological site, and see some of the old church. We didn’t have time for that, so it’ll have to be next time!

Nearby to the cathedral was some artwork depicting the history of Geneva, as well as some ancient cannons.

After that, we made our way to a monument dedicated to the history of the Reformation. Lots of statues of the leaders, quotes and paragraphs describing important events. To me, it just looked like a fun thing to climb on!

It was a chilly afternoon, so stopped at a cafe for some vin chaud, in order to warm ourselves up. After that, we decided to take the long way back to the car, and walked through parts of downtown Geneva. We stopped off in one store that really caught our attention, because they had “perpetual motion” devices in the window. As physicists, we couldn’t pass that up.

The store was very much like a combination of a museum and art studio, except that everything was for sale! They had navigational devices from centuries ago, one of the first cameras used to take pictures of the alps, disks covered in watch parts that floated in mid-air, etc. The most expensive item I took note of was 70,000 CHF! But the salesman challenged us to figure out how the devices worked, which was a good time. Very cool place!

We continued on through downtown Geneva, which is probably one of the most up-scale places I have ever been. Any luxury item or high fashion brand that you can imagine was present. Gucci, Michael Kors, Doir, Rolex, etc. Gems the size of your eyeballs sparkled in the windows. As my professor noted, “If there is no price tag, you can’t afford it.” Most of the stores had body guards just inside the doors. The juxtaposition of the Old Town and the modern downtown area was very interesting.

And that concluded our trip! There is still so many places I’d like to go in Geneva, like the UN, the Reformation museum, the Red Cross museum, and the natural history museum. It will definitely be worth another trip!

My Europe Reading List

While I am here in Europe, I have been doing a lot of reading in my down time. I have read some truly wonderful books, and wanted to spread the word. I’ll give a vague summary, so as not to give anything away, as well as my recommendations. So here they are, in chronological order:

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Never Let Me Go, Kazuo Ishiguro, 2005

Genre: Dystopian, Brushes the edge of science fiction

Set in the near future, this is a story about a group of friends coming to terms with their own unique reality that has already been laid out for them. It is technically classified as science fiction, but it is more a coming-of-age novel which tackles aspects of the human condition. Very good, would recommend to nearly all readers over the age of 13 or so.

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The Stars, Like Dust, Isaac Asimov, 1951

Genre: Fairly tame science fiction

A prequel to the Foundation series. If you have read those, then read this one! Apparently it is not as good as the others, but I still liked it. Doesn’t really resolve any major conflicts in the Foundation universe, but an interesting read nonetheless. If you haven’t read the Foundation series, you should! They are very solidly in the realm of science fiction, being set in the far future when mankind has expanded throughout the galaxy. Very well written, and an excellent story. Highly recommended for anyone, as long as you can handle a little space travel. Great for teenagers!

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Left Hand of Darkness, Ursula K. Le Guin, 1969

Genre: Pretty hardcore science fiction

This one was good, but not my favorite. Set on a distant planet in the far future, it is really more of a political novel than anything else. If you love science fiction and immersing yourself in different, complex cultures, then go for it! If not, then there are better things for you to read.

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The Hobbit, J. R. R. Tolkien, 1937

Genre: Fantasy, Adventure

A classic. I wanted to re-read it after seeing all of the movies. Some people complained that they modified the story too heavily from the book, but I thought they did a good job of staying true to the overall feeling and tone of the book, while adding some elements to make the adaptation to the modern screen work well. But the book is still an excellent tale of epic adventure and bravery. If you haven’t read it, regardless of whether or not you have seen the movies, I would recommend it. This is another one that is a great read for middle and high schoolers.

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Speed of Dark, Elizabeth Moon, 2002

Genre: Sort of science fiction?

Not what I was expecting when I picked it up, but I really enjoyed it. Technically science fiction, but it is really more about austism and how society views it. This book lends some much-needed perspective to the issue. I think everyone should read this novel. I recommend it whole-heartedly.

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The Alchemist, Paulo Coelho, 1988

Genre: Fiction

I’ll admit, this one was a little different – but I loved it. An inspiring story that reminds us all to seek out and pursue our own destiny, no matter the cost. Very short, quick read. I liked it so much I am considering reading it again, and I am sure I will get even more out of it the second time. Highly recommended!

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Spin, Robert Charles Wilson, 2005

Genre: Science fiction

I don’t want to say much about this one in case I give it away. I have never read a book quite like this one. It is set on Earth in the near future, and humanity has to deal with its imminent demise. There was enough plausible science to keep me very interested, and the way the book is written kept me reading late in to the night, too eager to find out what would happen next. As long as you can deal with a little bit of ‘science’, I would highly recommend this one. Really, really good.

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Childhood’s End, Arthur C. Clarke, 1953

Genre: Science fiction

I was hesitant about this one at first, because it started off a little slow. It starts off as an alien invasion story, which is a well-worn theme in science fiction by this point. Over the course of the book, things really picked up. I thought that there were some very powerful moments towards the end that really make you think about the potential mortality of humankind. Not my favorite of ones that I’ve read here, but still very good!

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Blindsight, Peter Watts, 2006

Genre: Hardcore science fiction

There are some books where you don’t know what exactly is going on, but you are anxious to keep reading because you know that the answers will become clear. I kept waiting for the answers to become clear in this book, but they never did. Honestly, there were many passages that I had to read several times and still couldn’t quite figure out what had happened. The book does raise some very interesting questions about what it means to be sentient and why we have evolved to be so (and at what cost?), but I still don’t quite think it is worth it. I give this one a solid “Meh”.

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A Collection of Essays, George Orwell, 1954

Genre: Essays

This one was…long. Not that the book itself was long, but it took a long time for me to get through it all. The writing style is just foreign enough and just out-dated enough that it took me a while to process what he was trying to say at times. That being said, I enjoyed some of the essays very much. Some were boring, but there were also some gems that were either comical or moving. He has some interesting things to say about the Spanish Civil War, Mahatma Gandhi, and vulgar postcards. I wouldn’t necessarily recommend it, except to a literature fan.

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A Ph.D. is Not Enough: A Guide to Survival in Science, Peter J. Feibelman, 2011

Genre: Non-fiction?

This book offers some helpful advice to those thinking about pursuing a career in physics. Though aimed at senior graduate students, I think it could be helpful to a physics student of any age. Though most of what is covered is common sense, it serves as an excellent reminder of what is really important.

Raclette – A (delicious) Swiss tradition

Last Thursday night, a colleague invited us over to her house to experience a very traditional Swiss meal called raclette. I had never heard of such a thing before, and so I am assuming that many of you have not either!

Raclette is technically a type of cheese. It is fairly mild, and the flavor actually reminds me a little bit of cheese curds. It is a firm (but not hard) cheese that comes from cows.

Now the dish called raclette gets its name since it uses that specific type of cheese. You start with a potato – but not a big russet potato like we have in the US. It’s a smaller, yellow potato, and the texture is similar to red potatoes. So you smash or cut the potato on your plate. While you have been doing this, the top part of a wheel of raclette cheese is being melted by some sort of heating element.

Me, waiting patiently for my turn!

A close up of the heating element.

After a sufficient amount of time, the top of the cheese begins to barely get brown. That is your cue to move the cheese and tilt it so that you can scrape the melted cheese off of the wheel and on to your potato. Then it is the next person’s turn. More than one serving is traditional!

Sufficiently brown!

My prepared potato!

This dish is typically served with dried meats and gherkins, both of which we had! White wine is the only acceptable beverage to accompany this dish. The story is that anything else will gum up your digestion, since it will cause the cheese to harden in your stomach.

Such a nice warm meal seems perfect for the cold winter months, but apparently it is more traditionally served in the summer. Farmers would ask their friends, family, and neighbors to come out and help them for the day. Then they would of course feed their guests, and raclette is a nice meal for a large group setting like that.

It was a truly delicious meal! I would be lying if I said I didn’t feel a little greasy afterwards, but it was worth it. And we had some great company! A large part of the Minnesota CERN collaboration was present. We don’t photograph very well… and some even avoided being in the picture! Not picture are Nicole (the hostess) and Professor Roger Rusack (the picture-taker).

Left to right: Gideon (Nicole’s husband), Shervin (UMN post-doc), me, Sean (UMN grad student), Jeremy (UMN professor)

A Day in Annecy

This past Sunday (now over a week ago), Sean and I made a trip to Annecy, France. Everyone we asked was very fond of Annecy, and they told us that it would make an excellent day trip. We often heard it described a quaint, French town. It did not disappoint!

We got on a bus to Geneva at about 7:15am. I was very surprised when we drove right by the United Nations! Call me ignorant, but I had no idea they were in Geneva. We’ll definitely have to go for a tour! Once in Geneva, we met up with our ride, who we found using a ride share website. This was definitely the way to go, since it was a third of the price and took half as long as the bus to Annecy. It was an hour drive, so we got dropped off in Annecy at about 9am.

When we got there, we went straight to the tourism office. That is usually your best bet when entering a new area here. Almost every town has one. Unfortunately, the office is Annecy is closed on Sundays. Thankfully, there were maps located in various locations around the town, so we were still able to pick out the local attractions.

So first, we set off across the lakefront, towards the Imperial Palace. Looking back at the main part of Annecy, we were treated to some lovely views.

The town is apparently known for its population of swans. In the summer. In the spring and summer, you can walk out on to an artificial island created especially for these majestic birds. Even in the winter, they still hang around!

As we were walking, I noted the number of runners we encountered. Even though it was snowing, and quite cold, a large number of people were still out running or walking. This has actually been the case everywhere I have been in France so far – people seem very active on the whole. And there are so many dogs! Lots of people walk their dogs without a leash, and all the dogs are really friendly. One time, I even saw a man’s dog carrying his owner’s phone in his mouth while the phone was playing music. I definitely did a double-take there.

We continued walking, and came to a public park area. I am sure it would be beautiful in the spring and summer. There was what looked to be a fairly extensive garden, a park, a restaurant, and even an aviary!

The apiary. There was also a fenced in region with ducks, geese, and other birds, but I couldn’t get a good picture of it.

The public walking area along the lake.

It looked as though this area also serves as a beach in the summer. The water was clear, the bottom was sandy, and there were large pillars that looked like a slide and a diving platform out in the water.

Then we came to the Imperial Palace. What a building! It is enormous, and beautifully built. We learned that it was actually a hotel. Can you imagine staying here?

After ample admiration, we walked back along the lakefront and into what is called ‘Old Town’. It is differentiated by its narrow, cobblestone stone streets and different architectural style.

I learned later that there are a number of notable buildings in Old Town, and that Annecy has a long and fascinating history. The one in the middle of the above picture is a picture of the Palais de l’Isle. It was built in the 12th century, and served as administrative headquarters, a mint, and finally as a jail through the middle ages. It is now a museum!

Old Town was very memorable for me. I was so absorbed in what I was seeing that I forgot to take pictures! It had a very small town feel. I was particularly impressed with all of the ironwork – fences, windows, balconies, etc.

We walked through the market, which happens every Sunday morning. The smells of dried meats, cheeses, and fresh bread came from various shops. My favorites were the bakeries. Their selection is amazing, and it is all so fresh! One item that really struck me was the enormous meringues, pictured on the top shelf, below.

Then we wandered through the streets a bit more, and took some winding turns…

…and ended up in front of the city’s Chateau! (Or castle). They informed us that they were closed between 12 and 2pm, and that we should come back later. So we decided to walk towards the church we could see up on the hill.

So first we took a wrong turn. Then…. we took yet another wrong turn! We ended up on the opposite side of the church’s wall.

This turned out to be a happy accident. Behind the church, we stumbled upon the trail head for a number of different trials going up in to the mountains. We still had plenty of time before the chateau would close, so we decided to go for it. We had no idea what we were in store for…

We stopped for lunch so we could continue to admire the view, and then continued up. We finally got to a place where the snow seemed too deep for our hiking boots to handle. Not wanting to end up with wet feet, we turned around. To the best of our calculations, we gained almost 1,000 feet in altitude!

We finally found the entrance to the church after continuing to follow the wall. What a beautiful building! It is called La Basilique de la Visitation (the Visitation Basilica), and was built in the early 1900’s.

We saw some nuns working outside, so it was obviously still very much in use. Unfortunately, it seemed that no one spoke English, so we didn’t figure out if we could go inside. Maybe next time!

We then walked down to go back to the Chateau (or Castle). Construction began in the 12th century, and continued through the 17th. It was the home of the Counts of Geneva. It is a sprawling property – I can’t imagine anybody ever being able to fill the whole space! It now serves as a museum. There was art, both old and new, as well as exhibits on the history of Annecy and the lake.

At this point, we were exhausted. We had been walking around all day and our legs would like a break. We looked in to a restaurant recommended to us by an employee at the chateau, but it was not open. Everything happens later here, especially dinner. So most dinner places do not even open until 7pm. One place that was open was a creperie! We decided that this type of traditional, French food sounded delicious, so we went inside.

We were very pleased to find that they spoke English, and that they even had some spare English menus! The menu was extensive, and it was very difficult to decide what to get. If this list isn’t tempting, I don’t know what is…

Even though I wanted to only order dessert crepes, my better judgement told me I should get a savory one as well. So I decided on the ‘Complete Lard Oignons” (egg, cheese, bacon, onions, tomatoes) and the ‘Ballon d’Alsace’ (pear sorbet, hot fudge, pear brandy, and set one fire!). They were both delicious!

At that point, it was almost time to leave, so we wandered around the more modern, downtown area for a little bit, and then headed to where we were supposed to meet our ride. We were so tired, and very happy to get home. I slept very soundly that night!

Overall, it was a wonderful experience! Annecy is a very nice little town, with a lot to offer. I think I would like to go back in the spring or summer, so that I can see the gardens. Maybe even take another hike! But this was just the tip of the iceberg, so I am very excited for our next weekend excursion!

Particle Physics – The Basics

Hello everyone! Prepare yourselves for some knowledge.

This post, while originally intended to be the first part of ‘All About CERN‘, sort of took on a life of its own and became worthy of an entire post to itself!

Physics is a difficult subject, but I tried to make it approachable. So if you are new to particle physics, then this is a good place to start! I highly encourage you to follow some links, watch the videos, or maybe even do some research on your own!

I’ll start from the very beginning:

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What is physics?

Physics is the science of matter and energy. It is also the science of forces (interactions between energy and matter) and motion (the result of a force). Four simple concepts.

To learn about these four concepts, we ask questions. We develop theories to answer these questions, and then test the theories through observation and experimentation. Through this process, our knowledge about the world around us grows, allowing us to ask deeper, more specific questions.

Physics really came to be what it is today in the early 1900’s, when the theories of quantum mechanics and special relativity were introduced. Special relativity deals with matter that is moving near the speed of light, while quantum mechanics deals with the strange things that happen at the smallest of scales (ex: particle behaving like waves, the quantization of energy, etc.).

For the curious, some videos: A Brief History of Quantum Mechanics, Special Relativity

What is particle physics?

Most, if not all, people know that everything around us is made up of molecules. Further, molecules are made up of atoms, and atoms are made up of protons, neutrons, and electrons. Maybe less commonly known is that protons and neutrons are made up of things called quarks.

So far, we don’t think that quarks and electrons are made up of anything else – meaning that they are fundamental constituents of the universe.

There are some particles (specific types of quarks and heavier versions of the electron) that exist, but do not make up the matter we see around us because they decay quickly into lighter particles. There are still others that don’t make up matter because they do not interact with other particles very much (neutrinos). And finally, there are types of particles called gauge bosons, which also don’t make up matter, because they are responsible for carrying the forces through which particles interact. And remember, all these things are unimaginably small.

All of these particles make up the Standard Model of particle physics, which has been developed in the second half of the 20th century.

The Standard Model

Scientists continue to study the Standard Model even today.

In 2012, a particle called the Higgs Boson (known to the media as the ‘God particle’) was discovered at CERN.

In a sense, it was the last piece of the Standard Model, and it fit perfectly in place. Though this was a large step forward, there are still a number of open questions, and CERN is one of the scientific laboratories leading the world in finding the answers. Check out my next post to learn all about it!

All About CERN

It occurs to me that many (if not most) of you are unfamiliar with the lab I am working at and what they are working on. I’m going to try to change that! If you aren’t usually one for a big dose of science, I ask that you stick with me. I am going to do my best to explain things in a way that everyone can understand. And it’ll be worth it, because scientists are doing completely mind-blowing things here.

If you are more curious and would like to learn more, I encourage you to follow some of the links I include! They will provide more detailed information. There is also a list of interesting links at the end, so you have that to look forward to.

New to particle physics? Brush up here!

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What is CERN?

CERN, or the European Organization for Nuclear Research, was founded in 1954. This multi-national endeavor is the world’s largest particle physics lab. It sits on the border between France and Switzerland, just outside of Geneva. It has about 2,500 permanent staff members, and annually hosts well over an additional 10,000 other visiting scientists and students.

CERN is in no way connected to military research of any kind. Any experiments that take place there pursue answers to questions in fundamental physics, and all records are 100% public.

CERN is home to a large number of experiments that focus on topics such as antimatter, dark matter, the composition of hadrons, supersymmetry, etc.

Who knows what they do here…

Many of these experiments require high energy subatomic particles to study, so CERN maintains a large accelerator complex which accelerates different types of particles to supply to the various experiments, including protons, antiprotons, and lead ions. If you have heard the name CERN in the news over the past years, it is most likely due to the Large Hadron Collider (LHC) – the largest and most powerful particle accelerator and collider in the world.

What is the LHC?

Before going in to specifics on the LHC, I’ll address what exactly a particle accelerator is and why we need them.

You may not be aware, but only about 1% of particle accelerators world-wide are used for research. The other 99% are used for things like radiotherapy and industrial processing. Accelerators are used to scan cargo containers coming into the US for nuclear weapons. They are used to harden steel, toughen asphalt, sterilize food, kill cancer, seal chip bags, create computer chips… the list goes on. This amazing technology also allows us to delve down to the very deepest level of matter in order to study the universe around us.

Particle accelerators actually accelerate particles by subjecting them to high electrical voltages. For the curious, many accelerators today use radio frequency caverns, but studies to develop a technique using plasma are on-going. If the particles are moving quickly enough (and therefore have a high enough energy), they can interact with other particles and change the physical properties of matter that it comes in contact with. They also have to steer these particles with giant magnets!

Now particle colliders do exactly what you think they would – they collide particles. Very high energy particles. When these high energy particles smash in to each other, they actually come apart. The pieces then either decay or combine in to other particles. We then detect and study what comes out of these collisions in order to learn about the fundamental structure of the universe.

So why is the LHC such a big deal? After being switched on in 2008, it is the largest particle accelerator in the world and truly an amazing feat of physics, engineering, and technology.

This is what the beamline looks like, except underground.

It takes protons from regular old hydrogen gas, speeds them up to 99.9999991% the speed of light, and smashes them together. Here are some facts that I hope will blow your mind:

• It is a circular accelerator, which has a 27km (17mi) circumference

• The protons circulate the ring over 11,000 times every single second
• The operational temperature is -456°F
• The air inside the beam line is thinner than the air in outer space

To put this in perspective, it takes about 20 minutes for me to drive from one side of the ring to the other, while it takes the protons .09 milliseconds. That’s crazy!

Here’s a great little video series put out by Fermilab, explaining things quite nicely:

The LHC is currently switched off for upgrades, and will be turned back on in late March. Last time, we discovered the Higgs boson lurking in the data we took. Who knows what will show up this time!

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Why is any of this important?

I often get questioned about the usefulness of fundamental physics research. Many see it as so far removed from their everyday life – so far that they are unsure why they should care or why we should be funding these ventures. To those people, I usually have one of two responses.

First is the answer for the practical folks: that most of the technology developed in pursuit of particle physics has been seamlessly integrated in to their everyday lives, but they don’t even realize it. In order to do all of this big science, physicists have pushed the boundaries on modern technology and taken it further than ever before. Examples include superconducting wires to carry more electricity to homes, better ways to transmit and store data, more advanced computer and electrical chips, computing grids, advances in parallel processing and machine learning, the internet… Wait, what? That’s right! CERN invented the internet. So you have particle physics to thank for that.

The first ever proposal for the internet.

Second is the answer that I like better, and the reason that I am in particle physics. It is pure curiosity. We live in this amazing, mysterious, magnificent universe which holds so many secrets just waiting to be discovered. How can you not feel the allure of that knowledge just beyond your grasp? It is too much for me to stand idly by and let the universe run its course. I want to know how the world around us works, down to every last detail. I want to see more.

If I may make an analogy: It’s always nice to see a beautiful mountain off in the distance, but it’s even better to go and climb it.

So I hope I have at least piqued your interest in what is going on in the world of physics! If you have ANY questions or feel I have left something out, please contact me! But I have said enough for one post. Next time, I will talk about the CMS experiment: one of the large detectors at the LHC.

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Further science links:

• Take a virtual tour of the LHC!
• Someone has already explained all of this much better than I have. Check out this CERN publication about physics and the LHC. Written for beginners!
• Very extensive blog about the LHC and physics. Can answer a lot of your questions!
• Feynman is a truly amazing scientist, as well as a teacher. His talks about science in general are inspiring. Found here and here.
• Tons of great 1-2 minute videos on particle physics!
• Check some physics-related TED talks!