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Posts Tagged ‘culture’

This blog is all about particle physics and particle physicists. We can all agree, I suppose, on the notion of the particle physicist, right? There are even plenty of nice pictures up here! But do we know or are we aware of what a particle really is? This fundamental question tantalized me from the very beginning of my studies and before addressing more involved topics I think it is worth spending some time on this concept. Through the years I probably changed my opinion several times, according to the philosophy underlying the topic that I was investigating. Moreover, there’s probably not a single answer to this question.

  1. The Standard Model: from geometry to detectors

The human mind conceived the Standard Model of Particle Physics to give a shape on the blackboard to the basic ingredients of particle physics: it is a field theory, with quantization rules, namely a quantum field theory and its roots go deep down to differential geometry.
But we know that “particles” like the Higgs boson have been discovered through complex detectors, relying on sophisticated electronic systems, tons of Monte Carlo simulations and data analysis. Quite far away from geometry, isn’t it?
So the question is: how do we fill this gap between theory and experiment? What do theoreticians think about and experimentalists see through the detectors? Furthermore, does a particle’s essence change from its creation to its detection?

  1. Essence and representation: the wavefunction

 Let’s start with simple objects, like an electron. Can we imagine it as a tiny thing floating here and there? Mmm. Quantum mechanics already taught us that it is something more: it does not rotate around an atomic nucleus like the Earth around the Sun (see, e.g., Bohr’s model). The electron is more like a delocalized “presence” around the nucleus quantified by its “wavefunction”, a mathematical function that gives the probability of finding the electron at a certain place and time.
Let’s think about it: I just wrote that the electron is not a localized entity but it is spread in space and time through its wavefunction. Fine, but I still did not say what an electron is.

I have had long and intensive discussions about this question. In particular I remember one with my housemate (another theoretical physicist) that was about to end badly, with the waving of frying pans at each other. It’s not still clear to me if we agreed or not, but we still live together, at least.

Back to the electron, we could agree on considering its essence as its abstract definition, namely being one of the leptons in the Standard Model. But the impossibility of directly accessing it forces me to identify it with its most trustful representation, namely the wavefunction. I know its essence, but I cannot directly (i.e. with my senses) experience it. My human powers stop to the physical manifestation of its mathematical representation: I cannot go further.
Renè Magritte represented the difference between the representation of an object and the object itself in a famous painting “The treachery of images”:

magritte_pipe

“Ceci n’est pas une pipe”, it says, namely “This is not a pipe”. He is right, the picture is its representation. The pipe is defined as “A device for smoking, consisting of a tube of wood, clay, or other material with a small bowl at one end” and we can directly experience it. So its representation is not the pipe itself.

As I explained, this is somehow different in the case of the electron or other particles, where experience stops to the representation. So, according to my “humanity”, the electron is its wavefunction. But, to be consistent with what I just claimed: can we directly feel its wavefunction? Yes, we can. For example we can see its trace in a cloud chamber, or more elaborate detectors. Moreover, electricity and magnetism are (partly) manifestations of electron clouds in matter, and we experience those in everyday life.

bubbleplakat

You may wonder why I go through all these mental wanderings: just write down your formulas, calculate and be happy with (hopefully!) discoveries.

I do it because philosophy matters. And is nice. And now that we are a bit more aware of the essence of things that we are investigating, we can move a step forward and start addressing Quantum Chromo Dynamics (QCD), from its basic foundations to the latest results released by the community. I hope to have sufficiently stimulated your curiosity to follow me during the next steps!

Again, I want to stress that this is my own perspective, and maybe someone else would answer these questions in a different way. For example, what do you think?

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I feel it mine

Tuesday, October 21st, 2014

On Saturday, 4 October, Nikhef – the Dutch National Institute for Subatomic Physics where I spend long days and efforts – opened its doors, labs and facilities to the public. In addition to Nikhef, all the other institutes located in the so-called “Science Park” – the scientific district located in the east part of Amsterdam – welcomed people all day long.

It’s the second “Open Day” that I’ve attended, both as a guest and as guide. Together with my fellow theoreticians we provided answers and explanations to people’s questions and curiosities, standing in the “Big Bang Theory Corner” of the main hall. Each department in Nikhef arranged its own stand and activities, and there were plenty of things to be amazed at to cover the entire day.

The research institutes in Science Park (and outside it) offer a good overview of the concept of research, looking for what is beyond the current status of knowledge. “Verder kijken”, or looking further, is the motto of Vrije Universiteit Amsterdam, my Dutch alma mater.

I deeply like this attitude of research, the willingness to investigating what’s around the corner. As they like to define themselves, Dutch people are “future oriented”: this is manifest in several things, from the way they read the clock (“half past seven” becomes “half before eight” in Dutch) to some peculiarities of the city itself, like the presence of a lot of cultural and research institutes.

This abundance of institutes, museums, exhibitions, public libraries, music festivals, art spaces, and independent cinemas makes me feel this city as cultural place. People interact with culture in its many manifestations and are connected to it in a more dynamic way than if they were only surrounded by historical and artistic.

Back to the Open Day and Nikhef, I was pleased to see lots of people, families with kids running here and there, checking out delicate instruments with their curious hands, and groups of guys and girls (also someone who looked like he had come straight from a skate-park) stopping by and looking around as if it were their own courtyard.

The following pictures give some examples of the ongoing activities:

We had a model of the ATLAS detector built with Legos: amazing!

IMG_0770

Copyright Nikhef

And not only toy-models. We had also true detectors, like a cloud chamber that allowed visitors to see the traces of particles passing by!

ADL_167796

Copyright Nikhef

Weak force and anti-matter are also cool, right?

ADL_167823

Copyright Nikhef

The majority of people here (not me) are blond and/or tall, but not tall enough to see cosmic rays with just their eyes… So, please ask the experts!

ADL_167793

Copyright Nikhef

I think I can summarize the huge impact and the benefit of such a cool day with the words of one man who stopped by one of the experimental setups. He listened to the careful (but a bit fuzzy) explanation provided by one of the students, and said “Thanks. Now I feel it mine too.”

Many more photos are available here: enjoy!

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Why pure research?

Thursday, October 2nd, 2014

With my first post on Quantum Diaries I will not address a technical topic; instead, I would like to talk about the act (or art) of “studying” itself. In particular, why do we care about fundamental research, pure knowledge without any practical purpose or immediate application?

A. Flexner in 1939 authored a contribution to Harper’s Magazine (issue 179) named “The usefulness of useless knowledge”. He opens the discussion with an interesting question: “Is it not a curios fact that in a world steeped in irrational hatreds which threaten civilization itself, men and women – old and young – detach themselves wholly or partly from the angry current of daily life to devote themselves to the cultivation of beauty, to the extension of knowledge […] ?”

Nowadays this interrogative is still present, and probably the need for a satisfactory answer is even stronger.

From a pragmatic point of view, we can argue that there are many important applications and spin-offs of theoretical investigations into the deep structure of Nature that did not arise immediately after the scientific discoveries. This is, for example, the case of QED and antimatter, the theories for which date back to the 1920s and are nowadays exploited in hospitals for imaging purposes (like in PET, positron emission tomography). The most important discoveries affecting our everyday life, from electricity to the energy bounded in the atom, came from completely pure and theoretical studies: electricity and magnetism, summarized in Maxwell’s equations, and quantum mechanics are shining examples.

It may seem that it is just a matter of time: “Wait enough, and something useful will eventually pop out of these abstract studies!” True. But that would not be the most important answer. To me this is: “Pure research is important because it generates knowledge and education”. It is our own contribution to the understanding of Nature, a short but important step in a marvelous challenge set up by the human mind.

Personally, I find that research into the yet unknown aspects of Nature responds to some partly conscious and partly unconscious desires. Intellectual achievements provide a genuine ‘spiritual’ satisfaction, peculiar to the art of studying. For sake of truth I must say that there are also a lot of dark sides: frustration, stress, graduate-depression effects, geographical and economic instability and so on. But leaving for a while all these troubles aside, I think I am pretty lucky in doing this job.

source_of_knowledge

Books, the source of my knowledge

During difficult times from the economic point of view, it is legitimate to ask also “Why spend a lot of money on expensive experiments like the Large Hadron Collider?” or “Why fund abstract research in labs and universities instead of investing in more socially useful studies?”

We could answer by stressing again the fact that many of the best innovations came from the fuzziest studies. But in my mind the ultimate answer, once for all, relies in the power of generating culture, and education through its diffusion. Everything occurs within our possibilities and limitations. A willingness to learn, a passion for teaching, blackboards, books and (super)computers: these are our tools.

Citing again Flexner’s paper: “The mere fact spiritual and intellectual freedoms bring satisfaction to an individual soul bent upon its own purification and elevation is all the justification that they need. […] A poem, a symphony, a painting, a mathematical truth, a new scientific fact, all bear in themselves all the justification that universities, colleges and institutes of research need or require.”

Last but not least, it is remarkable to think about how many people from different parts of the world may have met and collaborated while questing together after knowledge. This may seem a drop in the ocean, but research daily contributes in generating a culture of peace and cooperation among people with different cultural backgrounds. And that is for sure one of the more important practical spin-offs.

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It’s Saturday, so I’m at the coffee shop working on my thesis again. It’s become a tradition over the last year that I meet a writer friend each week, we catch up, have something to drink, and sit down for a few hours of good-quality writing time.

photo09

The work desk at the coffee shop: laptop, steamed pork bun, and rosebud latte.

We’ve gotten to know the coffee shop really well over the course of this year. It’s pretty new in the neighborhood, but dark and hidden enough that business is slow, and we don’t feel bad keeping a table for several hours. We have our favorite menu items, but we’ve tried most everything by now. Some mornings, the owner’s family comes in, and the kids watch cartoons at another table.

I work on my thesis mostly, or sometimes I’ll work on analysis that spills over from the week, or I’ll check on some scheduled jobs running on the computing cluster.

My friend Jason writes short stories, works on revising his novel (magical realism in ancient Egypt in the reign of Rameses XI), or drafts posts for his blog about the puzzles of the British constitution. We trade tips on how to organize notes and citations, and how to stay motivated. So I’ve been hearing a lot about the cultural difference between academic work in the humanities and the sciences. One of the big differences is the level of citation that’s expected.

As a particle physicist, when I write a paper it’s very clear which experiment I’m writing about. I only write about one experiment at a time, and I typically focus on a very small topic. Because of that, I’ve learned that the standard for making new claims is that you usually make one new claim per paper, and it’s highlighted in the abstract, introduction, and conclusion with a clear phrase like “the new contribution of this work is…” It’s easy to separate which work you claim as your own and which work is from others, because anything outside “the new contribution of this work” belongs to others. A single citation for each external experiment should suffice.

For academic work in history, the standard is much different: the writing itself is much closer to the original research. As a start, you’ll need a citation for each quote, going to sources that are as primary as you can get your hands on. The stranger idea for me is that you also need a citation for each and every idea of analysis that someone else has come up with, and that a statement without a citation is automatically claimed as original work. This shows up in the difference between Jason’s posts about modern constitutional issues and historical ones: the historical ones have huge source lists, while the modern ones are content with a few hyperlinks.

In both cases, things that are “common knowledge” doesn’t need to be cited, like the fact that TeV cosmic rays exist (they do) or the year that Elizabeth I ascended the throne (1558).

There’s a difference in the number of citations between modern physics research and history research. Is that because of the timing (historical versus modern) or the subject matter? Do they have different amounts of common knowledge? For modern topics in physics and in history, the sources are available online, so a hyperlink is a perfect reference, even in formal post. By that standard, all Quantum Diaries posts should be ok with the hyperlink citation model. But even in those cases, Jason puts footnoted citations to modern articles in the JSTOR database, and uses more citations overall.

Another cool aspect of our coffee shop is that the music is sometimes ridiculous, and it interrupts my thoughts if I get stuck in some esoteric bog. There’s an oddly large sample of German covers of 30s and 40s showtunes. You haven’t lived until you’ve heard “The Lady is a Tramp” in German while calculating oscillation probabilities. I’m kidding. Mostly.

Jason has shown me a different way of handling citations, and I’ve taught him some of the basics of HTML, so now his citations can appear as hyperlinks to the references list!

As habits go, I’m proud of this social coffee shop habit. I default to getting stuff done, even if I’m feeling slightly off or uninspired.  The social reward of hanging out makes up for the slight activation energy of getting off my couch, and once I’m out of the house, it’s always easier to focus.  I miss prime Farmers’ Market time, but I could go before we meet. The friendship has been a wonderful supportive certainty over the last year, plus I get some perspective on my field compared to others.

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Welcome to Thesisland

Tuesday, July 22nd, 2014

When I joined Quantum Diaries, I did so with trepidation: while it was an exciting opportunity, I was worried that all I could write about was the process of writing a thesis and looking for postdoc jobs. I ended up telling the site admin exactly that: I only had time to work on a thesis and job hunt. I thought I was turning down the offer. But the reply I got was along the lines of “It’s great to know what topics you’ll write about! When can we expect a post?”. So, despite the fact that this is a very different topic from any recent QD posts, I’m starting a series about the process of writing a physics PhD thesis. Welcome.

The main thesis editing desk: laptop, external monitor keyboard mouse; coffee, water; notes; and lots of encouragement.

The main thesis editing desk: laptop, external monitor keyboard mouse; coffee, water; notes; and lots of encouragement.

There are as many approaches to writing a PhD thesis as there are PhDs, but they can be broadly described along a spectrum.

On one end is the “constant documentation” approach: spend some fixed fraction of your time on documenting every project you work on. In this approach, the writing phase is completely integrated with the research work, and it’s easy to remember the things you’re writing about. There is a big disadvantage: it’s really easy to write too much, to spend too much time writing and not enough doing, or otherwise un-balance your time. If you keep a constant fraction of your schedule dedicated to writing, and that fraction is (in retrospect) too big, you’ve lost a lot of time. But you have documented everything, which everyone who comes after will be grateful for. If they ever see your work.

The other end of the spectrum is the “write like hell” approach (that is, write as fast as you can), where all the research is completed and approved before writing starts. This has the advantage that if you (and your committee) decide you’ve written enough, you immediately get a PhD! The disadvantage is that if you have to write about old projects, you’ll probably have forgotten a lot. So this approach typically leads to shorter theses.

These two extremes were first described to me (see the effect of thesis writing? It’s making my blog voice go all weird and passive) by two professors who were in grad school together and still work together. Each took one approach, and they both did fine, but the “constant documentation” thesis was at least twice (or was it three times?) as long as the “write like hell” thesis.

Somewhere between those extremes is the funny phenomenon of the “staple thesis”: a thesis primarily composed of all the papers you wrote in grad school, stapled together. A few of my friends have done this, but it’s not common in my research group because our collaboration is so large. I’ll discuss that in more detail later.

I’m going for something in the middle: as soon as I saw a light at the end of the tunnel, I wanted to start writing, so I downloaded the UW latex template for PhD theses and started filling it in. It’s been about 14 months since then, with huge variations in the writing/research balance. To help balance between the two approaches, I’ve found it helpful to keep at least some notes about all the physics I do, but nothing too polished: it’s always easier to start from some notes, however minimal, than to start from nothing.

When I started writing, there were lots of topics available that needed some discussion: history and theory, my detector, all the calibration work I did for my master’s project–I could have gone full-time writing at that point and had plenty to do. But my main research project wasn’t done yet. So for me, it’s not just a matter of balancing “doing” with “documenting”; it’s also a question of balancing old documentation with current documentation. I’ve almost, *almost* finished writing the parts that don’t depend on my work from the last year or so. In the meantime, I’m still finishing the last bits of analysis work.

It’s all a very long process. How many readers are looking towards writing a thesis later on? How many have gone through this and found a method that served them well? If it was fast and relatively low-stress, would you tell me about it?

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What Went on My Research Page

Sunday, December 30th, 2012

Remember when I was wondering, “What Goes on My Research Page?” Well, I finally decided what to put on it and got it posted:

Seth Zenz – Princeton University Department of Physics

Let me know what you think!

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Particles of the Day

Tuesday, November 20th, 2012
My copy of the 2012 PDG booklet

My copy of the 2012 PDG booklet

Last week, I got my copy of the 2012 Particle Data Group Review of Particle Physics booklet — which, along with its heavy, 1000-page full-length counterpart, we simply call “the PDG.” My very first copy, during my first months at CERN in the summer of 2003, is a vivid memory for me. Here was a book with almost everything you want to know, about every particle ever discovered! It was like the book of dinosaurs I had when I was a kid, and I read it in exactly the same way: flipping to a random page and reading a few facts about, say, the charged kaon.

My new copy of the PDG has inspired me to adapt this fun for non-experts. So each day, I’ll feature a new particle on Twitter; I’m @sethzenz, and the hashtag will be #ParticleOfTheDay. Since starting last week, I’ve featured the B0s meson, the pion, the kaon, the electron, and the Higgs.

How long can I keep this up? That is, how many particles are there? Well, that depends on how you count. The Standard Model has 3 charged leptons, 3 neutrinos, 6 quarks, the photon, and the W, Z, and Higgs bosons. But then there’s all the antiparticles. Dark matter candidates. The graviton. I could even argue for taking 8 days covering all the gluon colors! (Don’t worry, I won’t.) But most of all, there’s all the composite particles — those that are made from a combination of quarks. There are a very large number of those, and there will always be more to find too, because you can always add more energy to the same combination of quarks.

The point isn’t to be systematic. I might go back and be more specific. I might repeat. What I really want to do is find a particle each day that’s in the news or I can say something interesting about.

Flipping at random through a book of particles turns out not to be the best way to learn particle physics; ultimately, I needed to learn the principles by which those particles are organized. But it is an interesting way to tell the story of particle physics: its history and how it’s done today. After all, the particles do come out of accelerators in a random jumble; it’s our job to organize them.

Have an idea for the Particle of the Day, and what to say about it? Let me know!

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Are the Higgs Rumors True?

Monday, October 22nd, 2012

What Higgs rumors, you may ask? Well, there aren’t any that I know of, yet. But there might be soon…

There might be rumors soon because we are about to do another round of updates, for the 2012 Hadron Collider Physics Symposium (HCP). There aren’t any yet because our results (at least on CMS) are still “blinded,” which means that we haven’t actually looked at the “places” in the data where we see signs of our new boson. What we’re doing instead is looking at simulated data to see how much our results might improve when we add in the collisions we’ve recorded since ICHEP. We’re also putting in a few new analysis techniques, and checking them in the same way. And of course we are looking at data in other “places,” and we’re comparing it to simulations to make sure they’re doing a good job.

There will be several weeks between the moment we “unblind” — that is, look for the first time at what our signal looks like with the new data — and when results are shown at HCP. This is just as things were at ICHEP, and during those few weeks there were a lot of rumors around. It’s not possible to confirm or deny rumors when you know the status of ongoing work but haven’t yet agreed with your colleagues that it’s finished and ready to talk about publicly. So this time, I’m going to get in some general comments about rumors before I know anything at all about actual results. These comments will apply just as well to future updates.

What are we doing during the gap between unblinding and the conference? We’re checking our results, and putting them in a final presentable form. This is already compressed into a very short, hectic time, as I’ve written about before.

Are the rumors true? They are definitely not our official results, but they might turn out to be close. Or they might not. Specifically, the possibilities are:

  • A rumor is pretty much right. It’s no secret that particle physicists are bad at keeping secrets, and we really don’t want to be good at it. If one in 3,000 physicists decides to tell the Internet what our first-pass internal results look like, we can’t really stop them. Of course they’re breaking the rules, and we wish they wouldn’t, because it’s a collaborative effort and we’d prefer to agree together that we’re finished before announcing our results — because we want to make sure we did everything as well as we can. But still, our first-pass results are usually pretty close to final.
  • A rumor isn’t quite right. This could happen if we do find small mistakes or make refinements in the last few weeks of analyzing the data. This changes the answer by a bit, so the rumor is out of date. You could also make up a “not-quite-right” rumor just by making an educated guess based on our last results and how much new data we’ve taken!
  • A rumor is just plain wrong. Nobody says rumors have to be based on anything. Or they could be based on a misunderstanding of far-from-complete internal results.

We physicists working on this stuff don’t find it easy to wait for the answers either, and as Jon Butterworth has pointed out, rumors of other experiments’ results are actually dangerous for our work! For everybody else who’s tempted to indulge in rumors, just remember: you might be getting part of the picture early, or you might not. The only way to be sure is to wait for the next real update.

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What Goes on My Research Page?

Thursday, August 30th, 2012

It is time, it seems, for me to put up my first real departmental research page. This is a place to put up a picture, describe my research interests, and maybe link to some papers. It shouldn’t really be too difficult to write something up, as I have seem to have acquired a disturbing amount of practice in rambling about my research and putting up web pages about myself. But looking at others’ research pages has left me with a nagging question: what, really, are my research interests?

“CMS and ATLAS are two of a kind: they’re both looking for whatever new particles they can find.” — Kate McAlpine, Large Hadron Rap

In most fields, I would talk about a very specific set of problems I was interested in, and say what sort of experiments I was doing to figure things out. But the big detectors at the LHC try to look for everything, and I work on them because I’m interested in finding anything new that’s there. Am I especially interested in electroweak symmetry breaking because I work on the Higgs boson? Am I a precision tracking enthusiast because I’ve worked on pixel detectors? Well, yes, to some degree both those things are true — but the fundamental motivation for my research is to contribute to the overall program of understanding what the universe is made of, by whatever means my skills and the available opportunities allow.

Still, I suppose I had better be a bit more specific. Anyone have any suggestions?

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DPF 2011, tweet tweet!

Friday, August 5th, 2011

I know, I know, everyone has been focusing on the EPS and Lepton-Photon conferences (not to mention repeatedly putting in hyperlinks to their Web sites), but let’s not forget that the 2011 Meeting of the Division of Particles and Fields of the American Physical Society (DPF 2011, for short) starts this coming Tuesday. This will be the largest conference exclusively focused on particle physics in the United States this year, and it’s organized by the nation’s grass-roots membership organization of physicists, the APS. There are currently more than 450 people registered, so a large slice of the US particle-physics community will be there. This will be the fourth time that I’ve been to a DPF meeting, and I really do enjoy them — they are large enough to cover a broad range of topics, yet still small enough that you don’t get lost in the crowd.

For the first time ever, I find myself giving two presentations at the same conference — one on behalf of the CMS Collaboration (on the status of our distributed computing operation) and one on behalf of the D0 Collaboration at the Tevatron (on measurements of spin correlations in top-antitop production). On top of that, I’m also co-organizing a lunchtime panel discussion on “physics and the modern media.” What you are reading right now is a form of modern media, of course. We’re going to be talking with science journalists, communicators and bloggers about where communication about science is going…and what these sorts of people think of each other!

Since we’re going to talk about modern media, we figured that we should jump in with both feet, and that means Twitter. I must admit that I haven’t done much Twitter (although I do now have an account), but it seems to be all the rage. So, we’re encouraging Twitter users who will be attending the conference, and those who aren’t but want to keep up with what’s going on, to tweet away using the hash tag #DPF2011. If you are interested in the modern-media panel, feel free to tweet to us on Tuesday at 12:30 PM Eastern time; we’ll be keeping an eye on the feed and relaying interesting comments and questions to the panel.

More next week from fabulous Providence, Rhode Island!

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