posted by: Tom Loughran
posted by: Tom Loughran
On July 4, 2012, scientists at CERN from the CMS and Atlas collaborations announced that the evidence they’ve accumulated for the Higgs Boson has finally crossed the “discovery” threshhold of 5 sigma. Huh?
The more you learn about the discovery of the Higgs, the more the news of its discovery seems both old hat and an incredibly big deal. On one hand, the evidence has been long in coming: it better have been, for the $10B investment investment we’ve made in the hunt. So there’s not much new in the discovery announcement. On the other hand, what is unfolding here is an almost unfathomably successful episode in the history of science: a REALLY big deal. Rather than try to sketch the spectrum of reactions myself, I’ll just put down a few contributions that I’ve found useful, below. But first, a small story.
Back in 1999, Notre Dame physicist Randy Ruchti invited a bunch of local physics teachers into a program designed to invite students into particle physics. These invitations–to teachers first, and with them to students–were on the whole pretty well received. Teachers have hung around the Notre Dame QuarkNet Center for 14 years, and brought local students with them…hundreds of them. Seeing these invitations as a pretty good way to conduct science education, these teachers worked together–successfully proposing the Notre Dame extended Research Community (NDeRC) for funding to the National Science Foundation in 2006–to invite hundreds more, not only into particle physics but into many other areas of science and engineering. Working with graduate students and university faculty in university laboratories, these teachers designed experiences to extend the invitation to their students…now approaching tens of thousands of them.
A few handfuls of these local students assembled components now taking data in the CMS detector; others helped design the interface for student analysis of data flowing from CMS; others still are even this summer busy developing components for the next CMS upgrade: these relatively few students and their teachers were closely involved in the particle physics community. But all tens of thousands of them, in a way, owe a major part of their experience of science and engineering to the hunt for the Higgs: no CMS, no NDeRC. So it’s fair to say that the hunt for the Higgs is a pretty big deal around here. We’re better able than many to see the story of the Higgs discovery as our story. It’s entirely common to hear teachers and students talking about the hunt and its success in terms of “we”. And well they should.
So what’s the Higgs? Here’s a useful movie. It’s pretty basic, but it moves fast. Consider watching it twice.
If you want just a little bit more–you can read it slower;)–check out this blog post. Finally, here’s another take on why the discovery of the Higgs is such a big deal, and why it’s such a sad thing that the general public doesn’t appreciate the discovery so well.
I’ve got to say that it’s not quite so sad around here.
posted by: jmferlic
To end the year, Jamie, Derrick, and I started to work on a final project that included a lot of information during our year-long class. We worked with excel and graphical analysis to look at our data of the Z and W particles. Our main focus for the project was to see the mass of the particles, and determine whether or not our gaussian curves were around the established masses that are accepted by physicists.
The first particle we looked at was the Z boson. We decided to look at both electrons and muons to see what the difference was. To start off, we used excel to make the histogram information. Starting off with the bins, we had a common difference of 2 GeV up to 110 GeV. Making the bins too small would make the graph unclear because just having a little leeway between the masses would put the particles in different bins. This would make it harder to find the curve for the average mass of the particle.
After making the bins, we made the number of particles appearing in each bin. For this, we did the equation (=frequency(mass, bins)). This equation made it so that the mass went into a bin according to its GeV, or mass.
After making the two columns, we put the data into graphical analysis so that we could see what the mass was. The pictures above show the electrons and the muons in the Z particle. We were able to just fit the curve to a gaussian, and it gave us four numbers (and letters.) A was the height of the gaussian curve, B (the most important part for our project) was the distance from the y-axis, C was the width of the peak, and D was the bottom of the curve to the x-axis. B is the most important because it gives us the average GeV of the particle, or Z boson. As you can see, the electrons were around 90 (89.88) GeV, and the muons were around 92 (91.82) GeV.
As you can see, the muons have a higher average than the electrons. This is because of where the particles end up in the accelerator. In the CMS, there is many layers. Some of them are the tracker, e-cal, and h-cal. Electrons deposit their energy into the e-cal, which is the second layer in the CMS. Therefore, a lot of other particles might accidentally trigger the detector to think there is an electron when there really isn’t one. Plus, there are a lot more electrons than muons, and so with higher numbers there can be more difference since its harder to find out the energy of the electron compared to a few muons that go all the way through the detector.
So with our programs and data, we made two histograms to see if we came close to the accepted value of the Z boson. 91.2 GeV is what we looked up and found as the normal value with all the data taken. So by looking at both of the graphs, we ended up to surround this number with 90 and 92, showing that our data was correct.
After looking at the Z particle, we then changed course and I used our equations and programs to find the mass of the J/psi particle. With using the same equation and bins as what we used for the Z particle, I was able to make a graph of the J/psi.
We had our “B” around 3.116 GeV, which was very close to the value of the accepted value, 3.097 GeV. This shows how our data set was consistent with particles in showing a very close average to what the actual average is. Also, I found the graph interesting. Because the graph is at such a low GeV, it has a very significant peak, while the line continues to decrease. I think that because the energy is so low, there are more particles with lower energy. The histogram then explains the slow decrease in amount of particles as it gets to a higher GeV (other than the significant peaks where physicists know there are particles.)
The final particle we looked at was the W particle, which was harder than the other two. This is mainly because we had to look at a ratio. Because Z and W can be compared to each other, we could compare two terms. For this, we used the mass, and the transverse mass. Transverse mass is the mass in the x and y direction, perpendicular to where the particles are colliding. It does not include the Z axis, which we found out a lot of energy was not lost with the Z anyways. By using a ratio (W/transverse of W= Z/transverse of Z), we can find out what the mass of the W is.
To find the transverse mass, we used the equation sqrt(x^2+y^2). With the vector known for the transverse mass, we could than compare the two graphs. We did the same thing with the bins and amount of particles in the bins, and then we looked at the graphs.
This is the transverse mass of the W electron with missing neutrino energy.
The graph above shows the peak (around 80 GeV) of where the W’s transverse mass was. The end of the top of the peak is where we know to look for the average because that is the cut off. This graph is much more sloppy than the above graphs because the W has a particle (muon or electron), and than a neutrino, which we can’t see in the detector. The neutrino taking away some of the energy can make the graph uneven. That is why there isn’t a clear peak like the Z particle or J/psi.
The graph below shows the transverse mass of the W particle with muons. The graph seems to be clearer than the electrons, because it is easier for the detector to sense a muon, instead of electrons because there are much more hits closer to where the two particles collided at the beginning. Again, we said that from where the peak looked to be going down (cut off) that it was right at 80 GeV. When I put my cursor on the point at which it looked to be the cut off, the graph said I was on 80.1 GeV. Looking at the actual mass online showed that the mass of the W boson was 80.4! By just using some data and programs, we were able to get within .3 GeV of finding the mass of the Particle. The best way we saw the mass is in the graph at the bottom.
This graph below shows both the Z’s with transverse mass and mass. Because we see the peak to be at the same place, we know that with the W particle it will also be the same. That is how we were able to use the transverse graph of the W to find the total mass of the W. And we came close! Being able to use excel and graphical analysis gave us insight on the ways people can use their own ideas to find the masses of particles, even if they are missing energy in the detector from neutrinos. This project has made me a better particle physicist, and I now have a deeper understanding of how the detector works, along with knowledge on the energies of the Z,W, and even J/psi particles.
posted by: jmferlic
This last semester I have been working with the CMS, (Compact Muon Solenoid), and trying to understand how the detector works, along with the particles that go in and out of it. Before we started looking at different events in the detector, I worked on learning the many parts of the CMS, along with what particles are made of. I learned about up and down quarks that make up the protons and other small particles. Also, I learned about the four fundamental forces in nature. These forces are the strong, weak, electromagnetic, and gravitational. The strong force works with holding the protons and neutrons together with quarks. The weak force is what helps the particles decay into other forms. Electromagnetic forces help make particles by holding the electrons together to the neutrons and protons. The last force, gravity, is the most common force that we see in our daily lives with massive objects. We are still looking for a way to fully understand gravity, and we are looking at a particle to help learn more about some missing ideas. This particle is called the Higgs Boson, and scientists think that it will explain why particles have mass along with other important ideas.
After learning about what makes up the particles, I learned more about the detector and how it works. The first layer is the tracker, which has a magnetic charge. This part of the CMS detects any charge that a particle has. The magnet bends the electron in the way that it is charged, which is one way of helping us know what particle it could be. After the tracker, there is the e-cal. This layer is important because it detects where the electron and photon ends up. We can distinguish between the two when they land in the e-cal by looking at the tracker and noticing whether the particle showed going through there. If it did, we know that it is an electron. If not, we know that the particle did not have a charge and that it is a photon. The H-Cal is the next layer, and this is where both the neutral and charged hadrons stop. Again, you can tell which particle is which by looking at the tracker. The final layers are made of iron, which were made for the muon. The muon is what I have spent most of the semester looking at because it is an important particle in the detector. Below is a picture of what the different parts of the detector look like:
The muon is a negative particle that is in a category under leptons. It is similar to an electron, because it seems to not be made into smaller sub-atomic particles. The big difference that I know from working with the CMS is that the muons can come from outer space, and they come down to the earth. There are so many, and they are so small that they go through us and everything around us all the time and we never realize it. Also, as I said in the paragraph above, muons go all the way through the detector without stopping in any layers. Towards the end of the semester we started working on a final project, which included looking for muons in the detector. Here is a picture of what an event in the CMS looks like. I took out all of the other hits from other particles so that there were just hits from the muons coming out of the collision.
As you can see the muons go through the detector, and that there are two of them. From looking at this event we can see how the particles collided, and the two muons from the collision seem symmetrical to each other. These muons cancel each other out when they go away from each other like this because the momentum never changes from the collision of the two particles going in.
After I looked at the 3D displays of the many different events in the CMS detector, I moved on to looking at many different graphs in many eyes. Looking at scatterplots and histograms helped me to realize different patterns that were happening during collisions with particles. Scatterplots were important with comparing two different ideas. Here is an example of a graph:
This graph is interesting because as you can see, the energy is low. I noticed that there is a steady level of energy moving in a straight line with the mass, and around 90 Gev there is some energy. This shows that there is probably a z particle, because the z particle shows up with a mass around 80 to 90 Gev.
My final project for the semester was to look at cosmic rays and see how they were effecting the detector. Cosmic rays are muons that come down to the earth from outer space. It was what I was talking about when I was contrasting electrons to muons. Because they can come down from outer space, it is sometimes difficult to know if the muons are coming out of the detector, or if it is just coming down from space. Luckily, the CMS is built underground in Switzerland, and so for the most part scientists dont have to worry about determining what is coming from the detector or from outer space. This is because muons have a tough time getting through the ground to the detector. Unfortunately, there are still a few places that needed to looked at. There are holes going down to the detector at some parts because the workers had to be able to drop the parts down to where it was going to be assembled. The entire detector is 17 miles long, and so there had to be a few places where the pieces were brought down. Here is a picture of the size of the CMS.
Since the holes were able to give an opening for the muons to come down into the detector, there are places where scientists have to watch to make sure we are getting the right data. This is where our project starts. We wanted to see if data that we were taking from our events had muons coming down onto the detector. We started with 100,000 events, which gave us a lot data to trim in order for us to see how the muons effected our data. By using histograms in many eyes, we were able to see where the hole was in our detector and we were also able to see where the muons were coming from. To start off with our data, we made cuts to eta and phi. Eta is looking at the detector from the side, and it helps scientists see the angle at which particles are coming out of the detector. Phi is looking straight on, and shows the angle of the particles coming out from this side. This was important for us because we know that muons come almost straight down from space, and that it will come down straight from the top of the detector since it is coming from space. We know that muons can not come through the earth, but we also have to look at the bottom half of the detector as well though because for the particle to be a muon it has to be back to back event. For Eta, we added the two events together, (Eta1+Eta2), because the negative to the positive would give us close to 0. Here is a histogram of the cuts:
For phi, we did the absolute value of phi2-phi1. We did this because we wanted to see the particles that would come around pi, or 3.14. This is because phi is measured by more of a unit circle with 180 degrees is pi. Therefore, we want the muons coming down through the detector and going straight through. Here is another histogram that shows the cuts that we made to phi in order to see the if we had muons from space:
This shows that the particles are coming down from around the top (right shows the positive 1.57, while the negative is coming straight down the bottom at -1.57). This shows that we know that the particles are coming straight up and down. Now that we know that there are muons, we worked on finding out where the hole was coming from. By combining both etas and phis into one column, we were able to see that from eta, the hole was at the left side. Here is a picture of what we saw when combining both of the columns into one for both eta and phi:
This project helped me to become much more familiar with working in particle physics, and I learned more about using different websites and programs such as many eyes and excel. By looking at 100,000 data set and looking for cosmic rays, I learned more about the detector and how it worked, which I thought was very interesting. Now that I have a better understanding of how the detector works, and I can filter data to find out important details in the data, I want to work more on different projects by using the same techniques. Also, I have been working on MATLAB for a while, and I would like to add this skill into maybe working on adding a program that will help see the histograms. I would also like to add things to make a program that will be even more helpful than many eyes. Here is a picture of a histogram I have made with data from one of our sets from particle physics:
So far in computer programming, we have learned basic codes for using the MATLAB program, and we have worked with matrices and other graphs and animations. It will be nice to do more to add the two together later on this next semester. I am very excited about everything that I can do with these two skills.
posted by: Derrick Annis
Particle Physics, although it may seem like a daunting, extremely complex and high minded scientific undertaking, I found it to be very interesting and very reasonable branch of science. And this is coming from a person for whom math is not exactly his strongest suit. One of the biggest reasons I was able to enjoy and understand Particle Physics was because of the fact that if you study up on what is needed and the knowledge, many of the projects and ideas can be reasoned through with common sense, and time. I’m not saying that this project was a cake walk, it most certainly was not.But I am saying that if you use your innate common sense, and actually work towards the answers you will arrive at the correct solution. The second thing that really attracted me and interested me in this field of science is the fact that there are so many new exciting things going on. Just during the time I was working on this project two major shock waves went through the field of science. The first occurred when scientist in Europe supposedly discovered faster than light neutrinos, although that one is being heavily scrutinized, as if it is true it turns conventional physic right on its head. The second, the closing in on discovery of the Higgs has been going on for a while, but recently there were some major strides into finding the God Particle which grants mass unto all that pass through its field.
Above a theoretical Higg’s Boson, I don’t know if it’s scientifically accurate or not.
To really understand what exactly my project is and what it entails, you first need to learn what Cosmic Rays are. Cosmic rays are streams of particles traveling throughout Space and they do this for a very long time. Although these Cosmic Rays sound like the things that gave the Fantastic Four their powers, they aren’t, because if they were then we would all be superheroes (and villains). This is because these Cosmic Rays are everywhere, you’ve probably encountered thousands upon thousands of them already since you’ve woken up this morning. To illustrate this point, in Quarknet we have a small Cosmic Ray Detector that counts how many of these streams of particles have passed through it. One day at four thirty in the afternoon it had counted over seven thousand Cosmic Rays. This detector was inside to, where it’s more difficult for these rays to get inside. And if you are wondering just how complicated it is to measure these rays, it really is pretty simple, at least to my limited technical understanding of the machine. It works by sending a charge through the scintillator tiles on the top and bottom whenever a ray passes through both tiles. That charge then goes to a simple microchip that counts and displays the number of rays that went through it. It’s also a very small machine unlike many of Particle Physics tools of the trade. Here is a picture.
Although it may look futuristic it really is easy to understand.
Speaking of Particle Physic’s tools of the trade you need to know about our biggest and most important ones, the accelerators and the detectors, namely the CMS in my personal experience. The CMS is massive, the accelerators track is 17 miles long which for reference is like running more a little more than two thirds of a marathon, which are 26 miles long. The detector is also very impressive. It weighs as much as 30 jumbo jets, which comes out of necessity as in order to be as accurate as it is. It uses many different materials to be able to as much energy from the particles as possible, and then measure them so that we can examine the results more accurately. A simple explanation of the CMS’s parts follows, the tracker picks up anything that has a charge either + or – and shows it’s direction, the electronic calorimeter and the hadronic calorimeter together pick up anything and detect any charge +, – and no charge. The muon chambers pick up, you guessed it muons. By using the information from these we can piece together what is happening during an event. Lastly there is the magnet which induces curvature into the particles so that their charge can be discovered.The amount of work that went into making all of this is truly impressive, many countries have contributed to the CMS project and the work it took to make it is immense. They even had to make a tunnel and put it underground to block out interference from weather, and other things, namely Cosmic Rays. However to put the CMS into the tunnel they had to have an opening which is how the Cosmic Rays get into the data and interfere with the data. Since that opening allows them in and the Rays are all over the place that causes a problem.
CMS site wiht the 17 mile track
CMS itself look at the guy on the ground for size reference.
Now when we look at the tens of thousands of events and all the many variable we use it is impossible to extract just the Cosmic Rays from the data by looking at it. That’s why Microsoft Excel and a website called Many Eyes have been my two best friends. By using Many Eyes I can visualize the cuts that I am making to be able to actually see what I am doing by manipulating the numbers and variables within Excel. For our purposes in this Cosmic Ray project only a few variables really mattered to me in Excel, eta and phi along with variations on those two. Although it is hard to explain in words Eta is like a variable measuring position in a area that looks like a yo-yo on it’s side while phi is just a circle. The variations are SumEta which is Eta1+ Eta2 and DeltaPhi which is Phi1-Phi2. Using all of these variable in Excel lets me find out what exactly to cut on, and where to cut, along with the Many Eyes visualizations.
Although I would go through all the math and minute details of everything I did, I believe that would just be arduous and lengthier than need be. To go through and summarize the process I’ll explain it as simply and accurately as possible. By using the aforementioned variables SumEta and DeltaPhi we found all the particles that had a straight line relation, as in they are in a single line, and that they were coming from above. Both of those things are properties of Cosmic Rays. Next with that information we whittled down the eta and phi data by putting filters on where we know that there will be Cosmic Rays. Then we to Many Eyes and using the Histogram feature we went in and found the peaks of data where the Cosmic Rays were and then cut down and filtered regular events out. And although we were not able to isolate all of the Rays I believe that we did in the end get most of them. Even though we failed I think it was a challenging, and really a great look into the process of Science, which in this case involved many technological difficulties and arguments with the computer. To really show the process though I think you need to see the pictures of the graphs that came out of me making the cuts into the dataset of the events. Here are the most key graphs.
This graph is the values of SumEta plotted against those of DeltaPhi. through this we see that the data is centered around and peaks at 3.14 or pi. Which in radians measure is 180 degrees or a straight line. This is the graph that showed us the data that matches that property of Cosmic Rays. To capture that data and give it a little leeway,because we know that Cosmic Rays Can come in at slight angles also we made the cuts around that area
This graph came in after we made those cuts, and then combined the eta values into on big column and the same with the phis. From this we see the two peaks that almost mirror each other exactly. From this we once again see that theses events are straight lines because of the back to back on the 0 line. We can also see that they are coming from mostly the 90 degree area which tells us that these are probably Cosmic Rays. From there we moved on to see if the peaks matched up with the other data that we knew to be Cosmic Rays and unfortunately they did not match up that well, meaning we were not able to isolate all of the Rays. However I believe that it was a great process and I definitely have a better understanding what exactly is happening within all of these events. As I said earlier if you work at understanding Particle Physics you will learn it.
posted by: Tom Loughran
The central nervous system coordinates the flow of information from all parts of the bodies of animals (almost all parts, in almost all animals.) Think of it as the information management system of your brain, including especially the nerves running along the spinal cord. It is intimately involved in all of the complex activities of the animal as a whole. We can say that a single cell moves nutrients across its membrane, but we say of the animal as a whole that it eats when it’s hungry. Taking nourishment is an example of an activity of an organism as a whole, not just of any small assembly of parts. The central nervous system enables all the relevant parts to communicate with one another.
Science is an activity of a whole organism. But that whole is not a single individual; the organism is a species, or more precisely, a community. Its various activities are knit together into a complex system which accomplishes tasks…like searching for the Higgs boson. In a complex scientific activity like the search for the Higgs, the work of individuals is involved, in much the way that single cells are involved in taking nourishment. But the central activity is a group activity, by its nature. Members of the scientific community–which at one level are people, and at higher levels of complexity are collaborations (analogous to cells and organs in the body)–communicate with one another using a system much like our central nervous system. We call that system by various names: “network computing”, “the internet”, “the grid”, “the web.” It’s the central nervous system of human kind.
If you have five minutes, watch this 25-year retrospective on ESnet: one specialized portion of the internet dedicated to certain physical sciences, including those dedicated to finding the Higgs boson. It’s a chance to peek under the hood, so to speak, to see how an engine is wired. And when you hear of scientific discoveries, think about the whole organism–the scientific community–doing its work over systems like these.
posted by: Tom Loughran
The search for the Higgs boson has been the primary focus of the Large Hadron Collider and its detectors, the largest science experiment in human history. A recent release of data is edging science closer to a discovery, though we’re not there yet. Great progress has been made toward the elimination of possibilities as to what mass the Higgs might have: this process is known as exclusion, something like a certified non-discovery in a certain range of possible values. In other words, particle physicists are now pretty sure (to a 95% confidence level, or greater) what mass the Higgs does not have. And there are some intriguing hints in the data of what mass the Higgs might actually have, though the level of confidence in these hints is far too low yet to support any claim of discovery. So this is an interesting moment of insight into how particle physicists actually make progress: with painstakingly careful analysis of data accumulated slowly over time.
This November 2011 plot of combined data from the CMS and ATLAS experiments shows the current public state of the search for the Higgs boson. The video below shows a glimpse into the deliberations inside the CMS experiment over whether to release combined data of this sort. Take a few minutes to watch. If you are interested in the history of the Higgs search, this blog archive is a good place to begin.
posted by: krueff
If you haven’t read about the groundbreaking (not yet confirmed) results from the OPERA experiment in Italy READ IT NOW!
Particles (neutrinos) may be traveling FASTER than the speed of light! Which would, sorry Einstein, fundamentally change physics as we know it!
posted by: Tom Loughran
(The following blog post was edited and posted twice, inadvertently. Sorry: access to data visualizations often gets
This is a test of an embedded set of 3d scatterplots of CMS data (1000 dimuon events from 2 to 5 GeV.) With tools like this we can explore the parameter space of the data more efficiently, making sense of the data from a wide variety of perspectives. We hope to spot features of the data which can lead to new physics questions…at least new to us. In principle, and in fact on the home site, we can interact with this data through a java-enabled browser.
Let’s try an experiment in online collaboration. Manipulate the data–just change the parameters for each axis and dot size–until you find some favorite plot, then post the parameters (e.g., eta1, M, eta 2) together with an explanation (since eta zero is the section orthogonal to the beam line in the middle of the detector, it looks like very few collision products produce 2 muons both of which are orthogonal to the beam line.) Or just post a question…something to push our inquiry into the data forward.
Try it…post your favorite graph and some text in the comments box! (Try eta1, M, Pt1!)
For convenience, I’ve added a flickr slideshow of some screengrabs of a few obvious (and one or two not-so-obvious) plots. (I made this set using Jing, explorting to Flickr…all free stuff.) And you can get your own ManyEyes account–and upload your own data for online visualization–here.
For the record, here’s a video introducing ManyEYES.
posted by: Tom Loughran
Embedded here is a set of 3d scatterplots of particle physics data (in this visualization, 1000 CMS dimuon events from 2 to 5 GeV.) With tools like this, regional high school students (from Adams, Elkhart Central, Penn and Lakeshore) and teachers are exploring the parameter space of the data–what variables, or parameters, can you plot against which others–to make sense of the data from a wide variety of perspectives. Working with the I2U2 collaboration, we hope to spot features of the data which can lead to new physics questions…at least new to us. You can play too: just click to interact. (As always, if an embedded widget doesn’t load the first time, just refresh your page.)
Let’s try an experiment in online collaboration. Manipulate the data–just change the parameters for each axis and dot size–until you find some favorite plot, then post the parameters (e.g., eta1, M, eta 2) together with a question or even (if you know a bit of particle physics) an explanation…something to push our inquiry into the data forward.
Try it…post your favorite graph and some text in the comments box! (Try eta1, M, Pt1!)
(Got your own data, and want your own plots? You can upload data and create these visualizations at IBM’s Many Eyes project site.)