Feynman Diagrams and the CMS

 Bonjour! Bonjour!

Louis came back today to talk to us about Feynman diagrams.  It really is amazing how useful they really are.  You see, Feynman diagrams are more than just pictures that represent particle interactions, they are actually the terms of the equations that  help determine the probabilities of each possible outcome of the interaction going forward in time.  Each kind of vertex, like the ones up on the screen in the image, carries with it a unique term that represents that interaction.  So if you draw every possible interaction to get from the starting constituents to the ending constituents, you can just add up the terms to find the equation that represents that interaction.  You might say, "but what if I make a super long random chain that eventually gives the things that I want?" Well that would be one of the possibilities but each vertex added makes the term that is a factor of 37 times smaller, so adding more and more vertices, although possible would eventually make the process so unlikely as to be negligible and also, probably impossible to find in the first place.

It was for the reason of turning a complex mathematical process into a graphical and manipulatable format that Richard Feynman was awarded the Nobel Prize.  His advancement allows for rapid advancement of both ideas and the science behind them. 

This is me with my colleague from Bhutan where I am wearing a shirt that has a Feynman diagram representing an electron and a positron interacting through a photon and then moving on as a positron and an electron.  The positive time direction is upward, so the the arrow on the bottom left is an electron, but notice that the arrow on the bottom right is aimed backward in time, showing that it is an antiparticle (in this case a positron). The photon acts in no time, hence why it is horizontal, then the photon creates a positron on the top left and an electron on the top right.  If you were trying to figure out all the way an electron and a positron could become a different electron and positron you could draw a million versions of this, but each time you add a vertex it become less and less likely (although not impossible).  To find the probability of getting this outcome, you would add up all of the possible solutions. 

 I know that is not the easiest thing to understand, but this is the basis for more complicated interactions like ones where you start with 2 protons and end with two photons.  This is one of the ways in which you could find a Higgs, because a Higgs could decay into two photons with the same energy as the mass of the Higgs (around 125 GeV). So if I find two photons, I could look for every possible way and many different amounts of Energy are possible.  The random distribution should look like the blue dotted line in the graph below:

However, notice that there is an extra peak at 125GeV.  THIS is the evidence for the Higgs.  It was confirmed by both the CMS and the ATLAS experiments independently and at a 5σ significance!!  

So this leads us to the CMS, which was the second part of the day. I'm going to photo dump here to show you some amazing things I saw and did at the CMS.

LED showing from where and to where the PETAbytes of data is traveling and at what speed the data travels.

Behind this 7.5 meters of door is the CMS detector.

This is me in front of a life sized image of the CMS experiment

87.9 meter below the Earth's surface

We took some data on the pressure difference from the top to the bottom of the elevator. 

This is the crane that dropped some of  the pieces of CMS

Cool image superimposing model into an image of the CMS

When the LHC stops next July, the CMS will be modified to a hexagonal sensor on the end caps.

CMS sign off

We ended the night watching a movie about the discovery of the Higgs so here is me sitting in the chair Peter Higgs was when her heard the news that he was likely going to be awarded the Nobel Prize.

Medical Applications of Particle Physics, Some Teaching Pedagogy and a Field Trip

 Bonjour tout le monde!  

Today was another long but beautiful day.  It was full of particle physics, and colleagues and views of Mont Blanc.  So much to be excited about.  

The day started off with a lecture on the medical applications of particle physics.  Dr. Marjit Dosanjh brought her expertise to us in a lecture spanning the history of the medical practices routed in the use of particles which began with Wilhelm Rontgen in 1895.  He was responsible for taking the first x-ray image of his wife's hand and earned the Nobel Prize for his discovery of imaging under the skin without invasive surgery.  

The story continues with Henri Becquerel in 1896 who discovered natural radioactivity and Marie and Henri Curie who discovered radium in 1898, all three of whom were awarded the Nobel Prize for their work.  Radium was immediately put into use as a treatment in brachytherapy (therapy close or inside to the tumor).  From there the story moves to both treatment and detection of cancers and other disease.  

The use of PET scans for example are the process by which a positron emitter (like flourine-18) is attached to a glucose molecule and set into the body.  It runs to where the body is metabolizing the most.  Cancer is basically a group of cells that refuse to die or stop splitting and so the tumor needs lots of sugar, so the glucose goes there.  Now because flourine-18 emits a positron and a positron is a positive electron (Antimatter. More on this later.), it will annihilate when it comes in contact with an electron.  In this interaction, two photons are emitted and are detected by the machine around it, their trajectories pointing out where the sugar was consumed (the tumor).  This particle-particle interaction and the technology used to detect it were started in particle research centers like CERN.

In fact, as cancer treatments go, many radiology techniques use x-ray technology, but what is found by particle physics researchers is that x-rays tend to affect healthy cells as well and need to be placed into a rotating emitter that sends beams in multiple directions to increase destructive interference (areas where the x-ray waves can essentially be reduced to zero magnitude) and therefor have nearly zero affect on cells away from the tumor.  This is good, but the other findings show that if hadrons are used nearly the entirety of the energy of the hadron is dropped at the level it is stopped.  

A hadron is a composite subatomic particles made up of quarks i.e. protons, neutrons, carbon ion, etc. and the strong nuclear force (through a gluon, the  boson that carries that force). This means that hadron therapy is the current based outcome radiotherapy and the first hospital to implement it was Loma Linda University Medical Center, CA in 1991.  There are now a few others, but the new findings are that carbon ions accelerated in linear accelerators delivered in high intensity for a short time called FLASH may be the new best treatment in some cases reducing tumors resistant to all other treatment in just a few weeks or months.  This all stems from the idea that the energy from accelerated particles can be used to force cancer cells into apoptosis which is when normal cells trigger their self-destruct button.  When the FLASH is applied to healthy cells, they seem to hibernate a bit to withstand the radiation while cancers cells don't seem to have that reaction and have to blow up.  

All this to say, linear accelerators, (Linacs) are being used in the medical field so hospitals will need physicists.  There needs to be communication and understanding between biology and physics professionals so yet another reason for students to learn to be great communicators and to learn more about all sciences so that they can discuss the work done by each other.

After our lecture, we discussed some strategies for bring particle physics into classrooms successfully.  Talking mostly about student prior conceptions and how to affectively reduce the creation of problematic conceptions.

Lastly, we went to Science Gateway across the street from CERN.  A museum and exhibition hall maintained and run by CERN professionals, students and staff.  There were exhibits on Quantum Physics, Cosmology and Particle detectors.  It was really a very cool place with tons of things to see and do.  

There was the first server on the World Wide Web.

There were life-size displays of a thin slice of the CMS particle detectors.

There was an exhibit that allowed you to pretend to be an electron, so you walked around as a cloud of possible locations, and your cloud changed shape based on your proximity to protons on the ground, or if you tried to walk through a wall.

I liked this one about light.  Here is how I look in Infrared with sunglasses on.

And ultraviolet (look at all those freckles under the visible color of my skin.

The day ended with a lab where we build a particle detector called a cloud chamber.  

A cloud chamber was first created by Charles Thomson Rees Wilson, a Scottish physicist and he was awarded the Nobel prize.  It led to the discovery of the positron (that's the first antimatter particle remember) in 1932 by Carl David Anderson, who also was awarded the Nobel.  The cloud chamber allows a charged particle, like an electron, positron, proton or helium nucleus to name a few, to pass through a cloud of floating molecules suspended in a cloud.  As the particle passes through, it ionizes the suspended molecules causing them to attract to each other and coalescing in lines to form tracks in the direction of the path of the original charged particle. Take a look at this time lapse.

 

CERN Control Center, Cryogenic Test Facility and some lectures....and Jazz

 

Over the last few days, I talked about lots of magnets, like dipoles, quadrapoles and sextapoles.  Here are some cross sections of those magnets on display at the Cryogenic Test Facility where we talked  about the magnets are fabricated, what technology and what material is used, and then were able to walk into a facsimile of the LHC tunnel and get an idea of how things appear in it.

 

quadrapole (used to correct the particles into a more laminar beam as they are the same charge and generally do not want to be near each other )and with two vacuum tubes

 

quadrapole (used to correct the particles into a more laminar beam as they are the same charge and generally do not want to be near each other)and with one vacuum tubes for the Phase du pantalon (bringing two beams into one near the experiments)

sextapole (used to correct for chromaticity cause when you try to focus a beam of particles with multiple momenta)

A new superconductor being introduced in the next iteration of the LHC, the HL-LHC, Niobium-Tin

The quadrapole is the red magnet in the LHC.  This one has an American flag since many of the parts came from American Partners.

Our tour guide was a PHD student named Toby and he was able to tell us all about how the superconducting wires used in the LHC greatly reduce the size of the copper wires that would needed to operate the magnets with a 19,000A current as seen in the photo below held by my colleague Phebe from Australia and Suman from India.  

That same current can be carried through this Niobium-Titanium superconducting braided wire as long at the temperature is dropped to 1.9 K just a very short way above absolute zero and almost -457 degrees F.  This means that the magnets need to be supercooled in a bath of liquid helium.  Something you may not know about helium is that new helium is not created very often on Earth, it is a byproduct of radioactive decay and is found in underground pockets, so it is very hard to get and will only get harder in the future.  This makes it extremely expensive and therefor not lightly wasted.  An attempt is made everywhere in CERN to capture and redirect the any used helium back to the reservoir to be used in cooling baths after it is properly cooled.

The magnets placed into the LHC have to be built in room temperatures, which means they have to be trained in order to make sure that it is able to work in cryogenic situations.  First they are supercooled, then they are slowly brought up to 30,000A.  Each time the temperature starts to spike, current is stopped and then the magnet cooled again and current is restarted again.   In this way they can be more sure the magnet will not heat up and blow up 100 meters underground.  This is the testing facility where the magnets are trained, the blue dipole on the back left is made using Chinese and Italian parts.

After this visit, we went to the CCC, the CERN Control Center, and saw from where all of the accelerators in CERN are run.  

After lunch we met with the director, Bettina Mikulec (the woman in pink) and she told us all about how the accelerators communicate through the CCC, whereas before they used to talk to each other and had a terrible time of keeping each other abreast of changes.  Now they use this site where they and you or I could check on the current status of any of the accelerators and get real life updates.

There are lots of bottles along the edges marking celebrations for supplied beams for discoveries made. 

A demo wire beam test.  The wire sweeps through the beam causing particles to be scattered and counted.  This can be used to check the strength and suitability of the beam before or during its trip in the LHC, or the other target areas.

We met with a senior engineer today as well named Raymond Veness.  This was a great time to just sit and listen to a guy tell an awesome story from the point of view of the engineer trying to meet the impossible specifications made by the theorists.  The physicist didn't want anything in the way of the detectors, but the beam had to stay in a vacuum and the vacuum needed to be contained in something.  The request was that they wanted the particles to travel through nothing surrounded by nothing.  So they started looking at nearly transparent atoms.  You start with hydrogen and helium but they are both gases, and lithium explodes in contact with air so they tried Beryllium.  The beryllium vacuum tube is nearly transparent since it has so few particles in the nucleus and, like all atoms, is mostly empty space, so the physicists got nearly nothing to surround their nothing.  The engineering efforts that go into this place are insane.  At the end, he left us with a request to send their enthusiasm to our students and bring the diversity to engineering.  I asked how he thought diversity helped in the engineering at CERN and he said that anecdotally he has seen that since CERN has started to equalize the hiring of men and women, the communication between all stakeholders has improved.  I think communication is bound to improve when you need to express the thoughts in your head.  Being with likeminded and similarly backgrounded people can lead to lazy communication and mistakes and shortcuts being made.

To end the night we took in a short concert in Geneva and rode in a Ferris Wheel!  It was a wonderful evening!

Particle Accelerators and Particle Detectors

 Good Morning to Beautiful Geneva and CERN!

Today was a very information heavy kind of day where we learned a lot about how particle accelerators work and how they don't work.  Simon Albright gave us a talk about how each of the particle accelerators work in CERN and also about the processes in general.  It shouldn't surprise you to learn that a particle accelerator's job is to add energy to a particle.  This could be the 27km loop of the LHC that gradually speeds up already ridiculously fast particles, or it could be your microwave at home that accelerates the particles inside the cavity while making your food warm.  The interesting thing we took away from this talk was that CERN's job is not to make measurements or detect particles really.  CERN is in the particle accelerating business.  Experimenters will ask for certain things to be accelerated and CERN will start accelerating!

Very briefly, a particle accelerator using a combination of electromagnetic forces to accelerate the particle in either velocity or direction.  The Electric side referred to as RF energy, or radiofrequency energy is required to bring the particles to higher speeds.  Meanwhile, if you are going to change the direction or focus a beam of particles you would need to use magnets.  In the case of a linear collider, you are just speeding the particles up in a straight line, hence linear.  In the case of a circular collider you would need to do both.  There needs to be parts that turn the beam, parts that focus the beam and parts that push the beam.  They can't be in the same point, so you need an area (called an RF cavity) where the particles are pushed (think pushing a kid every time the swing comes back to you, the kid goes higher each time).

The Synchrocyclotron we visited before is an example of a circular collider.  What is interesting about this is that as you increase the speed of the particles, you are causing the particles to take bigger and bigger circles.  Think of spinning around holding a ball on a string.  As you spin faster, the ball flies farther away from you.  However, what we see is that as the speed increases, eventually, you reach a point that the particle can't get any faster at that frequency, so you must increase the RF.  This is because the faster you go, the more special relativity matters and you need more force to accelerate something. So you need to change the RF to keep the particle in synch with the changing field so it can keep getting pushed by the electric field. In a synchrocyclotron, that is exactly what happens, the RF and the Magnetic field are increasing together.  This is what most but not all of the accelerators at CERN are. 

Many are linear accelerators: line LINAC3 (Linear Accelerator 3), LINAC4, CLEAR (CERN Linear Accelerator for Research), and ISOLDE (Isotope Separator Online).  While others are circular like LEIR (Low Energy Ion Ring), BOOSTER, SPS (Super Proton Synchrotron), and LHC.

Jacob talked to us about how as beams are created and made, they need to be controlled and so you end up with lots of components like inputs, outputs (dumps), focusing magnets (dipoles, quadrapoles, sextapoles, etc), feedback measures, Vacuums, instrumentations, RF cavities, etc...

After that, we learned about Particle detectors from a doctoral student at CERN, Veronika Kraus, studying how to make better silicon detectors in the center of the CMS machine to withstand the high radiation that is present while making 600 Million collisions/second give or take.  

She told us about how we can measure different particles and really hit home the amount of different measuring devices needed to find all of the particles and work to find which collisions created which particles.  Very briefly:

Particle identification based (almost always) on their distinct interactions with matter:

• Charged particles (z, B, e- , μ+ , p, π+ )

– Ionization & excitation, Bremsstrahlung, Cherenkov radiation, Transition radiation, Multiple scattering

• Photons (γ)

– Photoelectric effect, Compton scattering, Pair production, Rayleigh & Thomson scattering

• Hadrons (π, p, n)

        – Hadronic interactions: Elastic/inelastic scattering with nuclei, Neutron capture, Spallation, Nuclear reactions

        – Neutrons: interact only via the strong force

• Neutrinos (ν)

– Detected indirectly via “missing energy” 

I won't go into all of this; it's very dense, but trust to say it is amazing the number of detectors needed to measure each or even some of these.  

Detectors are built like onions and each layer measures something new.  The inner chambers trace the paths of particles using silicon chips, the green measures electromagnetic particles (photons, positrons,  and electrons) the yellow measures hadrons (neutron, protons, antiprotons) and the kind of brownish is for measuring muons which are much harder to catch so you need more material.  the grey bit in the midst of all of this is the solenoid that give the CMS its name, Compact Muon Solenoid.  It provides the magnetic field that causes the charged particles to turn in the detector, similar to how the magnets in the accelerator do the same.

Lastly came Louis Roberto Flores Castillo who came and talked about the finding of the Higgs.  It was an amazing talk.  Louis had a way of breaking down incredibly difficult topics like why measurements are fundamental like charge and spin, but others like mass become break down the math.  If particles had mass themselves, none of the math of particle physics would work.  It turns out that mass must be a process of interaction with something else in order to keep the particles safe in these equations, so that was where the Higgs field came in and if there is a field, in physics, there must be a force carrier; in this case, the Higgs boson.  

Dr. Castillo gave us so many more explanations ranging from why photons and gluons are both mass zero but only photons are long range carriers while gluons break away after only a ridiculously small space. He talked about how impossible it was to get funding for the LHC and how even though it was impossible, it was done.  Phew....what a day.

We finished with Pizza and bowling!  I scored highest at 118! Next highest in the program was 116.  

Good night from Switzerland!

Intro to Particle Physics and a Couple of Field Trips

 

Bonjour!

Aujourd'hui we started the day with some insights into what CERN is.  Let's start with the name: Conseil Européen pour la Recherche Nucléaire.  Now this name is in English says the Council of European Nuclear research.  When it was first conceived in 1949 after the Second World War, groups of scientists from around Europe recognized that many bright minds had been lost of emigrated to the US.  This left them with a problem to solve.  How to bring science back to a war torn continent and how to get things started knowing that there was brand new science to be developed and learned from.  As nuclear science was demonstrated in a big way at the end of the war. To quote Olivander, "Terrible, yes, but great."  

Well the group worked together to find a spot and got some strong backers including Werner Heisenberg who signed the agreement for Germany.  Scientists from the twelve founding member states all signed in 1953 but it wasn't until 1954 that the countries from which they were sent accented to the concord and the group originally known as the Council became the Organization. However, the name CERN stays because OERN sounds stupid (according to Heisenberg himself).  

Throughout the next few years CERN worked to develop a working relationship with those original 12 nations but are now composed of 25 member states (the newest is Slovenia, where my new colleague Lenka is from and fun fact, where part of my family emigrated from as well) who pay yearly to cover more than 98% of the $1.4 billion budget.  There are other 12 other Associate member states and then the Observer states that include the US, Japan, the EU and UNESCO.  Russia was an observer, but was politely asked to get themselves in order before recommencing relationships.  Observer states tend to be ones that paid a large sum at one point to help build or contribute to a massive undertaking.  The US paid nearly $50 million to help build the LHC and the Russians had been helping since the beginning, at one point using refurbished Naval shells to supply the type of brass needed for an experiment here in Geneva.  

 Me and Lenka

After learning about CERN, we went for a trip to the Synchrocyclotron which was the first particle accelerator build in CERN.  The Synchrocyclotron was built in 1957, the very same year the Russians launched Sputnik and just 6 years after the first color TV.  If you look the personal calculator didn't show up until 1972 so all calculations were being performed by people or with calculators the size of buildings.

Timeline of CERN events and world events

 Here is the Synchrocyclotron in all its Glory! 

Enjoy the video showing how it works

Recognize here that only 3 years after the CERN organization was formed to do nuclear research, it has now moved on to smashing atoms into subnuclear pieces.  This is huge because at this point we have entered particle physics and left nuclear way, way behind.  So a rebrand of CERN might be:

International Collaboration

Education

Fundamental Research

New Technology

There we fixed OERN with something monstrous that vaguely uses the letters.

So on to our next adventure; we went to visit the ATLAS control room.  ATLAS is one of the experiments that live at CERN and use the LHC and the protons traveling at 99.9999991% the speed of light (c) to perform experiments and it...is...massive.  Here is a 1/3 scale model of the toroidal magnets that are in the ground at ATLAS.  This model had to be made to see if a magnet like this (which had never been made) would work 100 meters underground, so they build a model and it worked as expected, so they built the real ones.

For reference the blue bar is about one human tall (5'6'')

Because the beam is currently on and the experiment is running we were able to see the room but not much else, except this scale model made of Lego.

Control Room, manned 24/7 even when not functioning.

We will talk more about the make up of particle detectors tomorrow, but this entire set up fits INSIDE a set of toroidal magnets represented by the purple and orange tube looking things in the image behind me in this picture.  The magnets are there to keep the charged particles moving.  As charged particles enter the magnetic field, their path curves and then they hit detectors all around the experiment.  Where they hit and how hard tell the physicists what particles they caught.

We finished the day by meeting and listening to John Ellis who was a pioneer in the particle physics world.  He has done some great theorizing around supersymmetry which may help explain the missing matter in the universe (dark matter) which makes up nearly 27% of everything in the universe.  His work has been extensive here and he was able to give us a brief introduction to the ideas in particle physics. Mainly these points:

1. The standard model is the best thing we have right now, it looks like this:

The quarks are the purple bits, the leptons the green bits and the bosons the blue bits.  Quarks are held together and altered by gluons.  Photons control interactions between leptons and things called hadrons (made up of quarks) and W and Z is responsible for radioactivity.  That fancy orange one is called the Higgs boson and it's job is to give mass to matter.   He talked about how we started with just finding  that first elementary particle (the electron), then the first force carrier (the photon) and then little by little the table was filled from 1897 to 2012 when we confirmed the Higgs particle.

2. John gave us this analogy for how the Higgs works: 

Think of a Snowfield.  If a skier moves fast this is like particle without mass because the skier doesn't interact with the snow much, just slides right on by (e.g., photon or a particle of light it doesn't interact with the field of Higgs). 

Now consider a snowshoer who sinks into snow a bit so he moves slower and this is like a particle with mass who interacts weakly with the snow and it slows them a bit (e.g., electron or neutrino that interacts very weakly with the Higgs field).  

Lastly, a hiker sinks deep in the snow and so moves very slowly reacting with a whole bunch of snow and this is like a particle with large mass. (the top quark is the heaviest of the particles so it reacts most strongly with the Higgs).  

The Higgs is a snowflake in this scenario and the blanket of snow is the Higgs field.  This is the best analogy for this phenomenon that I have yet heard.

3. We don't know what is coming next.  The Higgs helps us understand where the mass comes from, but we don't know what is playing with the Higgs but not with photons (dark matter).  So now we look to the future and try to increase the energy in the LHC or maybe even build a new one, the FCC (Future Circular Collider which would increase the 27km ring of LHC to 91km and pass under lake Geneva and into  Annecy, France.

Bonne nuit!