• John
  • Felde
  • University of Maryland
  • USA

Latest Posts

  • USA

  • James
  • Doherty
  • Open University
  • United Kingdom

Latest Posts

  • Andrea
  • Signori
  • Nikhef
  • Netherlands

Latest Posts

  • CERN
  • Geneva
  • Switzerland

Latest Posts

  • Aidan
  • Randle-Conde
  • Université Libre de Bruxelles
  • Belgium

Latest Posts

  • Vancouver, BC
  • Canada

Latest Posts

  • Laura
  • Gladstone
  • MIT
  • USA

Latest Posts

  • Steven
  • Goldfarb
  • University of Michigan

Latest Posts

  • Fermilab
  • Batavia, IL
  • USA

Latest Posts

  • Seth
  • Zenz
  • Imperial College London
  • UK

Latest Posts

  • Nhan
  • Tran
  • Fermilab
  • USA

Latest Posts

  • Alex
  • Millar
  • University of Melbourne
  • Australia

Latest Posts

  • Ken
  • Bloom
  • USA

Latest Posts

Warning: file_put_contents(/srv/bindings/215f6720ac674a2d94a96e55caf4a892/code/wp-content/uploads/cache.dat): failed to open stream: No such file or directory in /home/customer/www/quantumdiaries.org/releases/3/web/wp-content/plugins/quantum_diaries_user_pics_header/quantum_diaries_user_pics_header.php on line 170

Archive for January, 2010

Yay! We moved!

Tuesday, January 19th, 2010

The IPMU Building

The IPMU Building

On Monday, I packed all my belongings living in my office desk and bookshelf into boxes, only to unpack them again one hour later. Why would I do such a thing? Because on Monday, finally, everyone could move into the new IPMU building! It’s all brand new, and right now, there’s still a lot of unpacking and putting up of furniture going on.

The Interaction Area

The Interaction Area

Until now, IPMU was a bunch of people dispersed over two prefabs and different floors of the General Research Building of Tokyo University on Kashiwa campus. The cohesion of our institute was only guaranteed by meeting up at tea break every day, and by the enthusiasm to be part of a new endeavor of everyone involved. Now, IPMU has become a place as well. Apart from the offices, a lecture hall, several seminar and conference rooms and a library which promises to come out very nice, the new building features a big interaction area in the center reaching up three stories, a terrace with chairs and tables, and an amphitheater-like structure on the roof. At night, the angled metal structure on the roof is lit up to give off a dark blue, eerie glow.

This is easily the nicest building I’ve ever worked in so far. The office situation during the 15 months I spent in the prefab was less than ideal, but that’s a thing of the past now, and I guess it’s part of the price one has to pay for being a pioneer. Now, postdocs share in two the shiny new offices of the new building. Everyone is very excited to finally be in the new building, and to finally be all together. We can’t wait to see the finished interior and to take possession of everything. This move is a big step forward for IPMU.

A bit like from the Sci-Fi movies...

A bit like from the Sci-Fi movies...


It’s an exciting time for your humble LHC blogger. She may just have a thesis topic… So what does that mean? (I often times wonder that myself).

With the recent success and in anticipation of high energy collisions (and therefore data), it’s time to figure out what can be found and what can’t given the projected amount of data. (We’re going to be running at ~7 TeV for the first part of the year, then ~10 TeV the latter half). Now lots of people are doing cross sections measurements – which is a different beast than searches (see below).  Cross section measurements take a particle that we know – Zs and Ws for example – and check to see if we measure what we predict. This is very important to do and I’m over simplifying but that’s the basic idea. Despite it’s importance, I personally feel like if I’m working on the highest energy accelerator in the world, I’d at least like to try to do a particle search.

The Cross Section Beast

The Cross Section Beast

This isn’t a completely trivial question because ever since the Tevatron turned on, theorists have been making predictions as to what was out of reach to our current experiments.  So what makes for a good early search? Lots of things, I’ll list some here:

  • Of interest…

Maybe this goes without saying, but I’m going to go ahead and say it anyway. A search has to be well defined and predicted. One doesn’t just look for the Higgs, or SUSY or Z’, they look for specific decay products that could come from the predicted particle and can not be explained by sometime else. Although we’re going to be 3.5x and 5x higher energy than the Tevatron, there has been years of data collected at the Fermilab experiments. Now there are some particles that are simply outside of their reach. For example just due to conservation of energy, nothing can be created >2TeV, but due to statistics (need that high fluctuation over the background again…) some limits are in the 100-200 GeV range. Increasing the energy will allow us, even with less data to raise limits.

  • High Signal:Background ratio

Since there is going to be a smaller data set (only 1 year of running), we simply won’t have enough statistics to say with confidence that we discovered certain particles. We need to say that the signal is an actual signal – not just a fluctuation of the background. I elaborate this in my Higgs post. This also means that there would be a distinct signature for example: something that would decay to 2 very high energy electrons and 2 very high energy jets. It could be di-boson production or W/Z+jets, but the electrons would come from a W/Z which was very far off mass shell – which is not impossible, but maybe not as probable.

  • Missing Energy (MET to be more specific)

This is a bit contentious, and maybe more a personal taste than anything. We won’t have a completely calibrated detector initially. The detector is calibrated by taking standard particles (Ws and Zs for example) and reconstructing them. We then convert the electrical signal out of the machine to energy and momentum. To do this, the more Z and W events the better – which like everything takes time. So the energy of the signal can be off. This isn’t a bad thing, but the way we calculate missing energy (say in the form of neutrinos) is by balancing the energy in the detector. For example if there is 40 GeV deposited in 1 part of the xy plane, then there has to be another 40 GeV in another part of the xy plane to balance it out. If we don’t really know if it’s 40 GeV or 45 GeV, then it’s hard to calculate missing energy. (I should also point out, it’s transverse energy, not just energy – which I can elaborate on if anyone is interested).

So these requirements gives us a whole range of particles to search for. I’m involved in a physics group called exotics. Exotics are a generic term for anything beyond the standard model and isn’t the Higgs or SUSY. This isn’t to say that Higgs/SUSY searches aren’t beyond the standard model… I guess they get their own groups since so many people are interested in them. It makes the exotics working group more intimate :-). My interests (and potential thesis) are in particles that would unite quarks and leptons (like how a W unites the family of quarks and the family of leptons). These generically are called leptoquarks.

So what’s wrong with the Higgs? It like the captain of the high school football team and head cheerleader all rolled into one particle to the high energy physics community. I don’t know… I’m just not that into it.



Daily Grind

Monday, January 18th, 2010
Screen shot 2010-01-18 at 1.07.58 PM

The color scheme I enjoy coding in (and my favorite programming language).

What is the main thing that a graduate students in particle physics spends most of their time doing?

Here are the most common activities:

A) Working with pen & paper, staring at equations, using computers to help solve/simplify those equations

B) Building/fixing hardware, Running wires, Connecting cables, Soldering connections

C) Writing computer code, Debugging code written by others, Documenting code

D) Reading/writing papers, Attending meetings, Preparing/giving presentations

This list probably generic enough that it could apply to a grad student in any science field.  (I hope for sanity’s sake that nobody spends most of their time attending meetings.) (more…)


As promised, but maybe a little delayed, I wanted to continue to share with the Quantum Diaries readers some of the buildings, sites, and people that have helped make my experience here at Fermilab amazing. So this entry I thought I would highlight someone whom every CDF’er knows and loves

Dee Hahn

As I mentioned in one of my earlier posts First Collisions there is photographic evidence of Dee being here ever since the beginning.

If you have ever wondered into the collision hall at CDF for any amount of time, then you know Dee. She is the unofficial (but I think most would agree she is the official) mom to CDF. She performs many of the operational duties at CDF, not the least of which is safety coordination and making sure radiation training is done by anyone who needs to be working on the detector.

While her official title may be “Safety/Training/Video Conferencing Coordinator”, I think of her more as the keeper of spirit at CDF. My first exposure to Dee was right before I had to go on for my round of ACE shifts (Data Quality Monitoring at CDF) and I needed to complete my radiation safety training. Even though I’m sure this was her billionth time helping some “green around the gills” graduate student she patiently and encouragingly made sure I knew when and where I needed to be to complete my training.

Dee Hahn "CDF's Heart"

Dee Hahn "CDF's Heart"

The Friday before I was to start my first round of ACE shifts the Operations crew has a going away party for the previous round of ACE’s at the Fermilab Users Center. I was invited to join and so I rode my bicycle there at around 5:30pm. The previous round of ACE’s (Homer Wolfe who is my grandfather ACE and fellow QD blogger) were there along with Dee and her husband Steve (another essential operations person). Some people had brought food and they were exchanging funny stories over a few beers when I struck up a conversation with Dee.

She then regaled me with some of the best stories about the many characters on CDF (a few nuggets about my advisor were especially priceless) and the different things that Dee does to help the quality of life around CDF.

She helps organize the pool schedule at Fermilab so everyone can take full advantage, helps new foreign students find places to go and people to connect with, and organizes trips around the city of Chicago so we can have some fun when we aren’t locked in the control room, and participates/helps organize the Fermilab Triathlon every year.

Her charm and caring were evident at once and through many days in the months that followed I got to know Dee a little and hear about the history of what has become this amazing collaboration. Through good and bad Dee has been a constant looking out for the little guy and improving the quality of life. To some she may seem brash and direct, but it is so evident that it comes out of a passion for her job and the collaboration that I relish in her style.

I heard it once said, “If you don’t know who Dee Hahn is, then you’re not really part of CDF.” After being around her I now understand what that means. If any of the people out in physics land have their own stories about Dee to share I encourage you to comment. If you find yourself touring/passing through Fermilab try to find her and if she isn’t busy see if you can exchange some stories, you won’t regret it. (However, if she is busy best to stay out of her way…you’ll thank me later)



Monday, January 18th, 2010

Currently I translate my own book written in Japanese, to English. This book is on D-branes in string theory, and the Japanese version was published in 2006. The book is for undergraduates, so includes not many equations. I tried to convey a flavor of fronteer researches on string theory and D-branes. Fortunately I got an offer from a publishing company for an English version of the book, so I am translating the book with my wife. I hope we can finish this translation in a month or so, so that the English version is published before the main results of LHC will come out.

As you can easily guess, it is very hard to work on translation. For me, it was much easier to write the book itself. Translation is a kind of tedious work, I need to choose terms which do not spoil the original sentences… So I decided to work on it only in trains. Everyday I commute by trains for almost one hour or so, and I can have a seat in the trains, although I live in the middle of Tokyo city. As you may know, Tokyo is a notorious place for the population, and every train is quite packed with people. However, fortunately, in my trains I can find only few people, as the direction of my commuting is opposite to the direction of most of Tokyo people. So I open my laptop every day in the train and start working on my translation, for at least 30 minutes. I hope you may be interested in the English version of my book in which the notion of D-branes and string theory is given, at the education level of graduate students.

K_short meson

K_short meson

One of the most amazing characteristics of science is reproducibility, i.e., experimental results can be reproduced by independent tests.  So, the first thing to check in any physics experiment is to see if you can reproduce what older, well tested, experiments have found running in similar conditions.  CMS did this very quickly last November when it presented its beautiful di-photon resonance peak, but the story does not end there.

Since December, CMS has taken advantage of the technical stop scheduled for the LHC in order to improve the reliability for the cooling system in the end-caps of the detector and, meanwhile, physicists have put a lot of effort in analyzing the data gathered during those few weeks of operation, mostly at 900 GeV of energy.

The results are quite fantastic.  I mean, ok, we know these particles (resonances) for quite some time now (most of them have been known for more than 40 years) and we can easily “google” them and obtain all their information, but to see them coming alive in our detector is probably only second to experiencing the actual discovery.  To make this succint, we know now that our detector is capable of reconstructing, with an astonishing precision,  the invariant mass of many mesons and baryons [“vintage” Kaon (short) resonance is shown in the plot as an example!!], such as pions, eta mesons, kaons, lambda baryons, etc, that were seen and studied many years ago by different experiments around the world.  Seeing these beloved resonances is not only cool, but they are necessary to calibrate the detector and to be in a much better shape for the next round of operations of the LHC, which will happen most likely in middle February.  Stay tuned, the next big thing will be seeing  Z/W bosons, for example, and from then a plethora (hopefully) of new and exciting physics (particles).

Edgar Carrera (Boston University)


Cosmic rays and everyday life

Saturday, January 16th, 2010

Every physicist, and probably every scientist, is faced at least once in a lifetime with the dreaded frase: “That’s very interesting, but what is that good for?” It doesn’t really matter how much your eyes are sparkling while you talk about your subject of research, it will always come, and you better have an answer for that in your pocket and ready to be used. And it’d better be good, since it can come from anybody: from the person seated right next to you in a long-haul flight, to most of your relatives, to somebody that you’ve just met in a party and that will fire away an innocent “what do you do for a living?”, unleashing the unavoidable chain reaction.

At the beginning, I always aimed high: I started to talk about our adventure as a species in discovering the ultimate mysteries of the cosmos, and how we have evolved from matter to conscience in this vast and beautiful universe. That did not always work. When talking about the Great Purposes of Science I get the feeling that people think we suffer from illusions of grandeur, and that we think that we’ll save humanity by counting light flashes in a block of ice. Getting “real” doesn’t help either, try convincing somebody that investing (their) millions to build an astrophysical observatory is the shortest path to improve the next generation of CAT scanners.

Frankly speaking, spinoffs are very important, and they may be used to highlight some of our collective work, but the reason why we do this is closer to my first attempt to an explanation than the second one. Anyway, let me put my vocational propaganda aside, and present you with this list of things where something as bizarre as cosmic radiation actually plays a role in our daily life, or where it has been found to have some, er, “practical” applications.

National security

Picture 1

A muon tomography scanner (orange structure) inspecting a truck (Photo: Decision Sciences Corp)

It seems like in today’s world everything is linked to this topic, and cosmic rays are no exception. The smuggling of nuclear material has always been an important concern to many countries, and there are some ways in which cosmic radiation can help us in preventing it. Cosmic rays are just plain protons and atomic nuclei that get their extravagant name only from their astrophysical origin. As they get to the upper layers of the Earth’s atmosphere, they interact with the nuclei of atoms that make up air  producing mesons (pions and kaons.) As these mesons decay they produce secondary particles, among them a huge number of muons, which can get to the ground.

This continuous rain of muons from the sky can be used to scan through the contents of, say, a container crossing a border checkpoint. Muons penetrate deeply into matter, but as the absorption length changes with the atomic number of the material, they can be used to spot the presence of heavy elements, something that may indicate the use of some radiation shielding, or fissionable material itself. This technique is called “muon tomography”, and there are companies that are already manufacturing cosmic ray detectors with this purpose.


Picture 8

Prof Luis Alvarez (left) with Egyptologist Ahmed Fakhry (center) and Team Leader Jerry Anderson (right) in 1967 (Photo: LBNL)

The idea of muon tomography is actually more than 40 years old, and it was proposed by Nobel laureate physicist Luis W Alvarez in 1965 for a very different purpose: the identification of hidden chambers inside the Egyptian pyramids. The experiment involved installing spark chambers beneath the pyramids and then, by measuring the cosmic ray flux in different directions, it would be possible to determine if in any part of the the pyramid there was less matter than there should be, revealing the presence of a then unknown chamber. The experiment, unfortunately, got null results.

Muon tomography is still being used today as an archaeological tool to explore other pyramids: a group from the University of Texas at Austin is building detectors to explore Mayan pyramids, while another group from Mexico’s National Autonomous University is using this technique to probe the pyramids in Teotihuacan.

Global warming


The CLOUD experiment chamber (Photo CERN)

What are the hottest buzzwords today after “war on terror”? Oh yes, global warming. And here too cosmic rays may be playing a role. Now, I don’t want to start yet another flame war about global warming causes here, but just point out an interesting possibility.

The charged secondary particles produced by cosmic ray interactions in the atmosphere affect cloud formation, and hence may play an important role in the overall radiation balance of the Earth. Physicists behind the CLOUD experiment at CERN are trying to determine how important this effect is by emulating cosmic rays using the historic Proton Synchrotron accelerator. The accelerated particles are then sent into a reaction chamber (see image) where the pressure and temperature conditions of the atmosphere are recreated. The interaction between these particles and the atmosphere inside the chamber is analyzed to study the significance of cosmic radiation in the formation of clouds and its impact on global warming scenarios.


Your computer just froze? Well, wait before blaming it entirely on Bill Gates, as the the origin of the failure could be thousands of light-years away from Earth. Computers store information in RAM memory chips by charging and uncharging billions of tiny capacitors. The interaction of cosmic rays with these capacitors could turn a binary 0 into a 1 or vice versa with unpredictable consequences. According to Intel:

“Cosmic ray induced computer crashes have occurred and are expected to increase with frequency as devices (for example, transistors) decrease in size in chips. This problem is projected to become a major limiter of computer reliability in the next decade. “

This is not a minor concern for them, and they have a US patent for a cosmic ray detector that goes into every chip!

Most of the times, the glitch produced by a cosmic ray event will go unnoticed, but sometimes they may have drastic consequences. You can check with the passengers of a Qantas flight from 2008 for an example. Apparently, the airplane computers experienced a cosmic ray event causing a malfunction that sent the plane into a series of dives that left several passengers injured.

Solar weather

A huge Coronal Mass Ejection event as seen by the SOHO satellite in October of 2003. The dots and white tracks that you see as noise around 0:44s are the results of the interaction between the charged particles from the Sun and the camera on board the spacecraft. Several instruments had to be turned off as a safety measure.

The closest source of cosmic radiation is a good friend of ours: the Sun. Our star constantly sends into space a stream of charged particles known as the “solar wind”, whose intensity fluctuates according to the 11-year-long solar cycle. During a solar “storm”, satellite electronic boards can be efectively fried due to the high flux of charged particles going trough them, and sometimes satellites are turned off to protect them against these events. The consequences? Communications are interrupted and navigation systems such as GPS devices won’t work. To avoid the loss of expensive satellites, a good “space weather” forecast is necessary, and websites like SpaceWeather.com provide updated information about solar activity. As of now, the solar wind is gently blowing at 479 km/second, with a density of 1.7 protons/cm3

In the most violent of these storms, even entire power grids can be affected. The interaction of the solar wind with the Earth’s magnetic field generates rapidly changing magnetic fields that can induce high electric currents in long power lines. Just as an example, in 1989 a geomagnetic storm (which is how these events are called) caused a huge blackout across Quebec.


Cosmic radiation amounts to about 13% of the total radiation that your body receives throughout the year, although it changes according to the height and latitude of the place where you live. In principle, the higher you get, the more radiation you receive, so the most exposed group of people to this kind of radiation is the crew of long-haul flights. Even for these cases, the exposure is not high enough to have specific risks associated with it. In this respect, the World Health Organization doesn’t link any specific health effects associated with the exposure to cosmic radiation, although in an info sheet it advises frequent flyers to limit travels during pregnancy.


Technology and Growing Older

Friday, January 15th, 2010

Earlier last week I celebrated my 29th birthday. This birthday was especially amazing for numerous reasons and I thought I would share in some of my thoughts on this birthday.

First of all the people I got to share this birthday with helped make it very memorable. My lovely fiancée went to great lengths to plan something of a surprise party for me and this labor of love really is an amazing thing and I count myself lucky to have her in my life.blh

My friend and fellow blogger Homer Wolfe was in on the conspiracy as well as another mutual friend (Hisham). Together they pooled their collective resources to bring me a birthday party that really reflected where I am in my life.

So when I walked in to the local gym where I climb and spend a good portion of my free time (I was lured by the promise of an evening of climbing and relaxing by my fiancée) I was stunned to see a 18X15X15 foot bouncy house (or moonwalk). Then over 20 of my friends were standing there next to the rock wall.

My response was: “Why is there a bouncy house, and what is everyone doing here?”bounce_rental_excaliburcombo

To which my fiancée responded: “This is your birthday party silly!”

I was floored! What followed was nothing short of a 3 hour play-fest. Here I was with fellow particle physics people, climbers, and professional trying to see who could bounce the highest, run up the slide first, and playing Frisbee and climbing on my 29th birthday.

Needless to say, it was perfect. Funny enough there wasn’t a single person that walked away from this party without an injury or scrape of some kind.  (There is a reason they post safety instructions on those things!) But everyone’s response was the same, “That was totally worth it!”

Now I reflect on this birthday because it represents a lot of different things. 1) My last birthday in my twenties. Although, as you may tell from the content of the party, age means very little to me. 2) The last birthday as a graduate student before moving forward in my physics career (I hope!) And 3) The gifts I received helped framed how far technology has come in my brief time on this earth.

It is number three I want to talk about briefly as many readers may appreciate this coming from a field where computers and technology drives our lives. I was given an external hard drive by my fiancée after she heard some of the horror stories shared by Homer and others in physics of their work computer becoming corrupted and losing valuable research, thesis’s, or other such things.

1tbI was shocked when I opened the gift and saw that I held in my hand 1 Terabyte of storage!

My first computer only had 100 megabytes of total memory.  I remember when ZIP drives were a big deal and you could finally have a Gigabyte of data on a single disk.

However, now when we talk about computing at the LHC we speak in terms of petabytes per year. The data set that will hopefully be my thesis is a few Terabytes big (initially, before skimming it down).

Our computers grow faster, smaller, and more powerful. Our projects get larger, our computing demands grow, and our ability to invent new ways of solving our complex mysteries becomes more sophisticated.

I live in the era of grid computing, dark fiber bandwidth, and Terabyte portable storage. 2010 promises already to be an amazing year here at Fermilab, at the LHC, and throughout the particle physics world.

But what I loved most about this birthday is that I combined the sophisticated world of physics and computing with the simple pleasure of bouncing in an inflatable castle with friends!


Radiation Exposure

Thursday, January 14th, 2010

Screen shot 2010-01-14 at 3.55.45 PM

My foray into particle physics began with a summer at the linear accelerator at Stanford in California. It’s the longest accelerator in the world, which makes it easy to find on google maps.  (I also must say that during my time there, the weather there was consistently perfect.)

Warning 01 Aug-3-2005

A welcome sign at the Stanford Linear Accelerator.

One of the first signs you see when you enter the site has a somewhat disconcerting message about chemicals and cancer.

I don’t know what chemicals they were referring to exactly, but one safety topic I learned about when I began taking SLAC’s mandatory safety training courses was related to radiation exposure.

In these safety courses I quickly learned that frequent fliers and airline employees are exposed to far more radiation than any employee at SLAC.

I hadn’t thought about it before then, but it turns out that being at high altitude exposes one to high energy particles produced when even higher-energy particles from sources elsewhere in the universe collide with particles in Earth’s atmosphere.  Being lower to the ground provides more protection than being high up where there is less atmosphere to absorb the radiation.

“A single, long international flight will expose you to a week’s worth of natural background radiation.” (Air & Space Magazine).  But that’s still well below recommended yearly exposure limits.

So in the end, I learned that particle physicists should be more concerned about the radiation they’re exposed to while traveling to their experiment!


Hello, this is the first blog I am putting here.. Hope you enjoy…

In these first working weeks at CERN, as is a bit traditional, not many things happen. People are usually coming back to work, filling up the line in the bank and post office at the Meyrin site and checking the new coffee machines that, recently, are being exchanged a lot. This year, things got especially slower, as a huge amount of snow is falling in a good fraction of Europe. Even in Arles, in the south of France, many centimeters of snow fell. The coldest temperatures reached (around -5°C) are, anyway, much above the -271°C kept in the LHC magnets. To warm up and cool it down again, the LHC would need months, so, the cooling system of the collider was kept working during this whole time.

Most CERN services are kept at a very minimal level during the end of year break. A few winters ago, actually, I remember having to work in the library, one of the few places where heating was still available. Warm coffee was only available in the gas station beside the Globe. This year, at ATLAS, the detector I work on, most of the subsystems were also shut down. The detector cooling system which circulates cold water in the front-end electronics suffered a few interventions in the beginning of the week and the electronics finally started to be turned on by Wednesday. I was supposed to be on shift and take calibration data (important, specially after a long shutdown), but some systems are still not available, and this was not possible. The detector seems like a gigantic animal, waking up after a little nap. A bit lazy to start what will be probably its longest operating period as we will start data taking earlier than ever (in February) and finish much later.

For the moment, I remember the end of Die Hard II : let it snow, let it snow, let it snow.

By Denis Oliveira Damazio (BNL), 2010/01/13