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Burton DeWilde | USLHC | USA

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Communicating Science and Its Value, pt. 2

Thursday, August 2nd, 2012

About three months ago, I wrote a blog post about science communication in which I bemoaned the disconnect between the American public and scientific consensus on many fundamental principles (such as evolution); suggested that Americans are exposed to science in a variety of media (movies, television news, online), but that much of this exposure contains inaccurate, partisan, and/or sensationalized information; and noted (without surprise) that science education has a positive impact on scientific literacy, so we should continue encouraging it — in a rational manner. Although I’ll be the first to admit that the post bordered on rant, it was based on a fair amount of personal experience and research, and seemed pretty reasonable overall. (I hope.) I had meant to quickly follow it up with a more pointed critique of the overall inability of scientists to effectively communicate with the public, as well as proffer some ways to improve the status quo.

Evidently, I was much delayed… for two reasons: 1) I realized that I was wading out into deep and choppy intellectual waters, so I should really do more research before opening my big mouth again, and 2) I finished writing my dissertation, defended it, and graduated with a PhD in Physics. So, after a line of research that led me far afield (into science education, cognition, social sciences, …), I am back. 🙂

First of all, I’d like to clear up some common misconceptions:

Gross domestic expenditures on R&D by the United States, EU, and selected other countries: 1981–2009. (NSF S&E Indicators 2012)

  • Americans are anti-science. Consistently, scientists are held in very high esteem (falling just behind firefighters and just above doctors) and are considered the most trusted sources of information (above religious institutions, news organizations, etc.). Public interest in science is high, as reflected most recently by the wide media coverage of the Higgs (sorry, “new”) boson discovery last month, not to mention all the friends and family who went out of their way to tell me how totally cool that was. Investment in scientific research and development has consistently increased over the last fifty years, and in total dollar amounts is higher than any other country in the world. Yes, the U.S. is pro-science!
  • Distrust of scientific findings stems from a lack of knowledge, so reducing that knowledge deficit will shift public opinion in favor of the science. This is the basic premise of the classic “deficit model” of science communication, which appeals to people trained to base their conclusions on evidence alone (i.e. scientists). However, research has proven it false. People aren’t just blank slates, waiting to be imprinted with scientific knowledge; they filter new information through cultural/religious/political perspectives, and when making decisions, these other considerations often trump pure facts. Counterintuitively, more knowledge may result in less support, and the hardening of opposition to the science. Take, for example, what happened in March when a bevy of distinguished climatologists presented overwhelming scientific evidence on climate change before Congress. No… it didn’t go well.
  • Scientists should be more assertive in public about advocating policy prescriptions based on scientific results. To me, this seems like a good idea, and it’s one that I have long supported. Unfortunately, research shows that when scientists talk about policy rather than just science, there are negative consequences: reductions in the percentage of people trusting what the scientist said, in the overall percentage of scientists that can be trusted, in the perception of the science itself, and so on. While Americans strongly believe that science should inform policy, they seem to prefer that scientists stick to the science, about which they have a credible voice. Note that I’m talking specifically in the context of communicating with the public, and not about the very good work that many science advocacy organizations do in collaboration with the public and the government. They key word, it turns out, is collaboration.

When Science Meets Politics: A Tale of Three Nations. ("In Science We Trust," Scientific American)

Science and technology are increasingly important in America, affecting aspects of our lives both small (morning routines, making social plans) and large (long-term economic prospects, health care), as well as the development and leadership of the entire country. The aforementioned disconnect with the public on both established and emerging scientific issues is problematic for a number of reasons, not least of which because it facilitates poor personal and national decisions (if memory serves, the Founding Fathers had quite a bit to say about the necessity of “a well-informed citizenry”). Of course, most people aren’t scientists, so they must rely on someone else to share salient and useful scientific knowledge with them, and in turn, make better-informed decisions. This is the role of science communication.

The problem that science communication currently faces is not a prevailing anti-science sentiment, nor a lack of activism on the part of scientists, nor insufficient knowledge of the public alone. I’ll explain next time.

Yes, I’m ending on a cliffhanger. 🙂

— Burton


Communicating Science and Its Value, pt. 1

Monday, April 16th, 2012

In the past I’ve made it known that I’m a politically-engaged person — and not without some commentator controversy. While I generally prefer to keep my science and politics separate, they inevitably intersect in the matter of governmental funding of scientific research and conflicts between groups driving the national dialogue on science policy. Unfortunately, scientists are often left behind in this conversation, resulting in a serious disconnect with the public.

It’s not hard to find embarrassing stories about how Americans are ignorant of basic scientific knowledge: roughly half believe dinosaurs and humans coexisted, 1 in 5 adults believes the Sun revolves around the Earth, and when it comes to acceptance of evolution, we’re out of step with much of the world. On many topical issues — global climate change, nuclear energy, genetically-modified foods, vaccination, cell phones — an abundance of misinformation drowns out the science, or at least muddies the waters. And even worse, many Americans don’t understand how scientists draw their conclusions, i.e. the scientific method, nor do they apply it in their daily lives. A much-quoted survey from 2007 found that 70% of Americans are “scientifically illiterate” (though that distinction, as well as the statistic, is misleading: scientific literacy is not on a binary scale).

I realize that I’m probably preaching to the choir here: You all have made the effort to read a physics blog written by physicists about highly technical topics, which suggests to me that you are either totally awesome science enthusiasts or… scientists. Thanks for reading! 🙂 But from whom does the rest of the country not following Quantum Diaries get its science information?

Well, for starters, there’s Hollywood and the entertainment industry, where scientists are commonly portrayed as mad/evil or awkward geniuses — people to fear or mock, perhaps, but not befriend or idolize — and scientific accuracy is typically thrown out the window in favor of more explosions. There’s also the Internet, where people can and do say pretty much whatever they want without the need for peer review or, you know, facts. Do you remember when unfounded fears that CERN was going to create an Earth-devouring black hole ricocheted around the web? Although the Internet is an incredible resource for information and personal research, it’s treacherously inconsistent. The public also learns about science from the news/media, where sensationalism is routine and “fair and balanced” reporting means giving equal time to scientific fact and wild speculation. Recently, a chemistry publication entitled “Evidence for the Likely Origin of Homochirality in Amino Acids, Sugars, and Nucleosides on Prebiotic Earth” made headlines when, in its final two sentences, the author suggests that advanced, potentially dangerous, dinosaurs could exist elsewhere in the universe. Take a guess on how the media covered it. Unfortunately, most Americans don’t learn about science from scientists, and given the abject mess of these other sources, it’s a wonder that a quarter of the population is “scientifically savvy and alert.”

Well, an explainable wonder: America is the only country in the world that requires undergraduates to take a year of general education — and it makes a difference! Education works, who would’ve guessed? 😀 However, there is serious cause for concern, particularly with regards to K-12 education. One of the great legacies of the Bush Administration, the “No Child Left Behind Act” of 2001, tied federal funding of public schools to student performance on annual, standardized tests in math and reading (laughably, the law stipulates that all children are to perform above average). Perhaps not surprisingly, educators under pressure are more likely to “teach to the test” to improve scores at the expense of other subjects and skills, such as science and critical thinking. Should we worry about what will happen when the NCLB generation makes it to Physics 101…?

It’s worth pointing out that a post-secondary education in physics, for instance, is also subject to distorted priorities: Our training is extremely focused on skills needed to continue in Academia and fundamental research, while statistics show that a significant fraction of us go on to careers in industry immediately after grad school, and that the most-used skills are not properly developed in the curriculum. Furthermore, in the long term, most of us end up working outside of Academia. Are we better off learning electrodynamics from a glorified textbook on special topics in mathematical methods? I think not.

More to come!

— Burton 🙂


Conference-going for the almost-graduated

Monday, April 2nd, 2012

I’m currently writing you from Atlanta, GA, where I’ve been attending the APS April Meeting on particle, nuclear, and astro physics (this year’s theme is “100 Years of Cosmic Ray Physics”). Officially I’m here to give a talk on my thesis research (the leptoquark search I’ve been alluding to for some time but still haven’t fully explained — patience, it’s coming!), but really I’m here to network and interact with other physicists re: getting a job post-PhD.

Self-promotion comes naturally to some people… Not me. I prefer to casually undersell, which is a bit of a problem given that resumes are crafted to formally oversell a person. Still working on my elevator pitch.

At any rate, the conference has provided a number of opportunities for an almost-graduated job-hunter to explore interesting intellectual avenues and make connections with advice-givers and potential employers. I was fortunate to attend a panel discussion held specifically for grad students on the topic of careers, networking, and carrying out a job search. In addition to providing an occasion for free food, the panel also imparted some very useful wisdom:

  • Create individualized resumes and cover letters for each position you apply to. Whoever reads your application will know if you’ve done your homework or, alternatively, if you’re trying to catch a bunch of different fish with the same net. Heads-up: Most fish will slip through.
  • Communication is essential. You can’t expect employers to infer why it is that they should hire you, you have to tell them, in clear, understandable terms.
  • Networking is also essential. People often get jobs because they “know somebody who knows somebody,” so it is beneficial to your job search to talk about your qualifications and what you’re looking for with as many people as possible. If that sounds obnoxious, well… indeed it is, but don’t let that stop you! 🙂
  • Maintain interests and passions outside of those in your particular sub-field. Physicsts are “all-arounders” that perform well in a variety of tasks; a surprisingly large fraction of physics PhDs get jobs totally unrelated to their thesis research or, in fact, physics. Being well-rounded is a strength to be valued and emphasized.

Tonight is the last night of the conference. Earlier today I nailed my talk, even getting a couple general laughs from a room full of physicists (not easy!) so now I just have to find myself an interested future employer or somebody who knows him. I’ll be in the hotel bar, working on my pitch and resumes — let’s chat!

— Burton


Greetings, from Thesis Limbo

Tuesday, February 28th, 2012

Hello, hello, hello! After a hiatus of unexpected duration, I’m back — with stories to share, topics to discuss, and photos to tag. 🙂

When last I wrote, I was preparing for a big life transition: from research, analysis approval, and wine at CERN to thesis-writing, job-hunting, and micro-brews in NYC. I felt ready to move on, but it proved… more difficult than anticipated. Of course. I spent my first six weeks as a guy on my very generous friend’s couch, working 14-hour days to fix a stubbornly problematic final result that wasn’t ready for approval, or publication. In the process I learned quite a bit about limit-setting and statistical inference (totally thrilling topics that I’ll regale you with next time, I promise), but before long I was at wits’ end.

In all seriousness, folks, I considered dropping out of my PhD program to join the disillusioned ranks of “all but dissertation” grad students seeking work in a tough job market. Scary stuff! From what I’m told, an MS in Physics is about as useful as a BA in English… (Just kidding, English majors!) Fortunately, we were able to work out a solid and defensible result, I took a much-needed break for the holidays, moved off the couch and into my own apartment, and pursuant to a number of New Years resolutions, I began to write my thesis. Crisis averted.


An office with a view...

Of course, writing a thesis isn’t easy, either. I solicited a lot of advice, but nobody thought to mention a useful and obvious starting point: an outline. It helps to have a plan! Especially one divided up into convenient and manageable chunks. After that, all that remains is filling in the blanks… which I’ve been doing for the past two months. 🙂

That’s not all I’ve been doing, though. The analysis I’ve worked on is a day away from its final ATLAS approval, but that’s after a seemingly endless series of comments, revisions, and approval meetings. (Anna recently wrote about LHCb’s publication procedure — yes, ATLAS requires a similar number of hoops to jump through. UGH.) My advisor has obliged me to re-do a study I did three years ago and stuff it in an appendix to my thesis, do a couple of future sensitivity studies for the main analysis itself, continue giving talks, reading papers, and attending meetings, present my results at an upcoming APS conference, and even change the title of my thesis. Dammit! What was wrong with “Leptoquarks: the Particles That Go Both Ways“? At the same time, I’m dealing with graduation logistics, updating my CV, thinking about (and training for!) a job and career post-PhD, and generally trying to become a real, non-student adult.

This is Thesis Limbo, less favorably known as Dissertation Hell. It’s a strange point in one’s life. But I’m working through it.

I’m lucky to have many friends around to keep me sane. Here are two of particular relevance: Daisy, who coordinates this ragtag group of physics bloggers, and Flip, whose ongoing saga of Electroweak Symmetry Breaking has enthralled us all.


Daisy at the Audubon Society, with Joe Physicist


Flip in my apartment, borrowing my books


– Burton 😛



Tuesday, November 1st, 2011

I’ve lived and worked at CERN for two years, and now I’m going away. This is a common story.

When I first moved here from Stony Brook, NY, I was a fresh PhD Candidate who had just finished up a hardware project, acquired a young new advisor, and started learning C++ in a serious way. I had no idea what research I would be doing at CERN.

I spent a couple of months thoroughly lost: in red tape and French bureaucracy; in a labyrinthine, nonsensically-numbered hodge-podge of office buildings and industrial warehouses; in a social scene dominated by physics and physicists; in supermarkets that close at 7pm, roads that go roundabout-to-roundabout, and conversations that start in one language and inevitably end in another.

With the return of beam in the LHC (after a well-publicized accident) came a new sense of urgency and purpose, for both CERN and myself. I remember how the pace of life on-site noticeably picked up, all of us marveling at the screens showing the beams’ status as we sped by on the way to a meeting, or a coffee. I got involved in the ATLAS 3D Pixel Collaboration. I took midnight shifts to help with data-taking on the prototype silicon sensors, jumped into software development on particle track reconstruction, and got started on a short-term analysis project to determine the hit resolution of the sensors, complete with smart, Swedish-made post-doc.

As with most “short-term” projects at CERN, mine became long-term, hindered by unforeseen complications in the data and, at all steps along the way, the analysis framework in which many of us do our work: ROOT. Complaining about this distinctly sadistic piece of software became a favorite pastime! And still is. In the end, my analysis was somewhat inconclusive — so it goes.

Fortunately, my group at Stony Brook was in the process of initiating a more cohesive, aggressive research program, and I got drafted by my advisor into an Exotics search for second-generation leptoquarks. I was able to help build our analysis framework from the ground up, and in the process learned how to code in Python. It was a revelation. Meanwhile, the LHC had begun its 2010 run, and it seemed like our dataset was doubling every other day! These were very exciting times. Nobody knew what we might find in all this data, be it supersymmetry or a Higgs Boson or, maybe maybe maybe, some sort of leptoquark.

The analysis went roughly as expected: An endless series of incremental changes, talks in weekly meetings, unanticipated crises, deadlines, plots, emails, interpersonal conflicts, and soul-crushing hoops to jump through on the way to publication. It was an awful lot of work and stress, all for the best null result in the world. Huzzah. To be honest, it was a bit disheartening that the LHC experiments hadn’t dropped a bombshell on the scientific community, like OPERA’s super-liminal neutrinos measurement or the discovery of a true “goldilocks” planet, but it certainly felt like something was just around the corner.

I went to Cambridge for a conference and Stanford for summer school, dated a native Genevois, visited Paris and Berlin and Rome, got trained as an ATLAS Pixel shifter, celebrated the holidays with friends and family back home, and had the chance to visit the ATLAS detector down in its pit during the annual winter shutdown.

For the LHC’s 2011 run, I basically picked up where I left off with my leptoquark search; it was meant to be a straightforward update. But, of course, nothing is ever as easy as we expect: the beams’ increased luminosity meant much more data but also challenges in simulating and effectively filtering out all the extra events; new software releases fixed some bugs but introduced others; new collaborators meant new interpersonal conflicts (or is it just me?!); and improvements to the analysis itself seldom worked out as nicely, or quickly, as we would have liked. Deadlines have a way of flying by… but that’s research! Or so I’m told.

Meanwhile, I visited New Orleans, Helsinki, and Zurich, got involved with LGBT CERN, filmed, edited, and co-produced a particle-physics-themed zombie movie, and started writing my thesis. ATLAS kept taking more and more data — until just a few days ago.

And that’s it! Two years at CERN. In less than a week, I’m going away — back to New York, to write my thesis full-time, hunt for jobs (decide what sort of job I’m hunting for…), and graduate. It’s hard looking back on a chapter in your life and assessing it for lessons learned and enduring connections made, accomplishments and moments of zen. While I have my share of regrets and what-ifs (why, why did I never finish learning French?!), I feel like I’ve come a long way these past two years. From slightly jaded, I-can’t-wait-to-start-my-analysis junior grad student to thoroughly jaded, I-can’t-wait-to-finish-my-analysis-and-get-out-of-here senior grad student. All these gray hairs must count for something.

Heads-up: This blog is about to get hardcore, thesis-style. But first… an international move, and a long series of good-byes.



Thesis Advice

Wednesday, September 7th, 2011

Well, I’ve finally started thinking about starting to start writing my PhD thesis. I’m told this is a big deal.

It is known that asking a grad student about the status of his or her thesis, or when he or she plans to graduate, is bad form — practically taboo — and until recently, I applied this golden rule equally to myself as well as people whom I didn’t want to aggravate. Alas, those care-free days are over! The harsh onset of fall (I see the clouds gathering for their annual, six-month layover), the obvious absence of summer students (CERN is notable for many reasons, not least of which is that, at the start of September, all the undergrads leave), and the near-completion of what I consider a polished analysis (my advisor would probably disagree) have all conspired to get me thinking more long-term. And this brought me, kicking and screaming, to my non-existent thesis.

Over the years, and particularly in the last week or so, I’ve accumulated a fair amount of “thesis advice” from more senior grad students and post-docs. Fun fact: Nobody wants to talk about their thesis while they’re writing it (unless to complain about how totally unfair life is), but once they finish, they suddenly become very eager to share their experience with others. This is what I have learned so far:

– Don’t start writing your thesis until you’ve completely finished your analysis and, ideally, published a paper on it. Then start with the analysis section, using your paper as a guide. Try not to plagiarize yourself.
– Write the experimental section of your thesis in the second year of grad school. What you learn about your detector will serve you well in your analysis. Try not to plagiarize others, as there are only so many ways to say “The LHC is a proton-proton collider with a center-of-mass energy of 7 TeV.”
– Why not dance it out?
– The hardest part of your thesis is just getting started. (CHECK!)
– The hardest part of your thesis is writing the introduction, so save it for last.
– The hardest part of your thesis is getting your committee to agree on a date for you to finish.
– Hide “Easter eggs” throughout your thesis, such as figures with dinosaurs used for scale, or phrases not normally seen in scientific writing. Find out how closely your advisor is reading.
– You can write a thesis in about six months.
– You can write a thesis in about three months.
– “I wrote my thesis in two months.”
– “I have to write my thesis in the next five weeks.”
– Start applying for jobs while you write your thesis, so by the time you’re done, you’ll have something to move on to. Don’t graduate before you have a job lined up — you can always delay! Some people do this for years…
– Your thesis title is important! Choose with care.

Okay. So what I’ve learned so far is this: Every thesis, and every person writing a thesis, is unique. What works for one doesn’t work for all. Inevitably, necessarily, you have to find a way through it that works for you, and doesn’t drive you (completely) crazy in the process. Talking to others — perhaps blogging about it? — can help, but in the end, your thesis is what you yourself make out of it.

Whew. The good news is, I have a working title! Leptoquarks: The Particles That Go Both Ways.

— Burton


The Sound of CERN (Now, with sound!)

Monday, August 1st, 2011

Hi, All!

I’ve been absent for a bit, competing in the twice-annual Race to a Conference Publication. It’s a full-out sprint that lasts for… five months. No comment on how I did,  but hey, here’s a fun quotation that is totally not at all in any way related:

I love deadlines. I like the whooshing sound they make as they fly by.

— Douglas Adams

Anywho! Last time I wrote about “The Sound of CERN,” as inspired by a reporter on the hunt for it, but I wasn’t able to share anything more than a description of those sounds. Well, I went out and did some field recordings of my own! So put on your headphones, and listen closely: This is what CERN sounds like. 🙂


In order: The ATLAS cooling towers, the CERN computing center, high-voltage power lines outside Building 40, a computer that’s working too hard, coffee machines at Restaurant 1, a conversation in French. Alas, I wasn’t able to track down the flock of sheep with bells on their necks — they have a few different grazing fields, and we only cross paths when I’m without a microphone. Better luck next time… when I’ll include video with the audio?

Burton 😀


The Sound of CERN

Monday, June 27th, 2011

I recently had an encounter with an unusual reporter. He had been roaming about CERN in search of a story, and by chance that brought him far afield to the test beam control room at CERN’s SPS North Area where I was spending the day on shift with a colleague. Because of technical difficulties (or was it a worker’s strike?), the beam was off, and our devices under test weren’t taking any data, so when the reporter came by and asked to speak with us, it was an emphatic “Yes, but I need coffee first.”

Now, to be fair, it wasn’t the reporter himself that was unusual, it was the story he sought: “The Sound of CERN.” Um, what? This gentleman had been taking field recordings all over in hopes of piecing together an aural representation of the world’s largest particle physics laboratory, and now he wished to speak with us. After seeing — hearing! — so much of CERN’s infrastructure and equipment, all of it humming whirring beeping pulsing clicking, he had decided to widen the scope of his project to include the scientists inhabiting this soundscape. Sounded reasonable to me.

After my colleague rather eloquently explained the work we were doing at the test beam and why it mattered in the grander scheme of things, our conversation moved on to the reporter’s work. Why sound? Well, it’s awfully difficult for people to relate to fundamental physics on a visceral level, and intellectually isn’t much easier — there’s a reason we spend so much time in grad school! But understanding is facilitated whenever you can associate a concrete bit of sensory information with an abstract concept. What sound does a Higgs boson make when it decays into two W bosons? What color is an electron? (No, I’m not talking quantum chromodynamics…) If you could reach out and touch a proton, would it be soft like a plushy, or hard like a billiard, or squishy like a hard-boiled egg?

Or, in this reporter’s case, What does CERN sound like? Well, I will give you some hints — in words, until I acquire the means to record the audio myself:

  • like a room full of computers, fans blowing hard while merciless physicsts bang on their keyboards
  • like a 1.6 Tesla Morpugo magnet thrumming softly while a beam of 180 GeV pions passes through it at close to the speed of light
  • like a flock of sheep grazing in a field 100 m directly above the low-energy end of CERN’s accelerator complex, the bells on their necks chiming pleasantly
  • like the coffee machines in R1 dispensing liquid energy to tired grad students
  • like the electronic tone emanating from television screens once every forty seconds, indicating when the SPS is spilling beam your way
  • like water cascading down the inside of the ATLAS cooling towers at Point 1 on the LHC
  • like two people chatting excitedly as you pass them by, “… saw good agreement in the high-pT tails, but something strange …”
  • like this, maybe

Until next time — keep your eyes open and your ears tuned!



So You Want to Discover a New Particle (Pt. 2)

Sunday, May 22nd, 2011

Editor’s note: For those who missed it, here’s “So You Want to Discover a New Particle (Pt. 1)

Hi, Readers!

I went away for a bit to pursue some other extra-curriculars, but now I’m back — and the blog has a new home! Perhaps a new audience as well. Since this (my first) Quantum Diaries post is actually the second part in a series, and I am a shamefully sporadic poster, I suppose I owe you a synopsis:

• The Standard Model is boring, but new particles are not.
• If you’d like to discover a new particle, theorists have conveniently provided you with an expansive menu of possibilities.
• Choose your particle with great care. This involves physics-, politics-, and plushy-based considerations.

So, let’s assume you’ve done some research, sent some emails, formed (or joined) a research group, and selected the new particle you’d like to discover. Congrats. Now what? Well, your particle hasn’t been found yet probably because… it isn’t easy to find. 🙂 There could be multiple reasons for this:

• It has a tiny production cross-section (the LHC produces it only once in a blue moon, as opposed to millions of times per second).
• It looks like other, already-discovered particles, so it blends right in with the (so boring!) Standard Model.
• It is produced and/or decays in such a way that our particle detectors have a tough time seeing it and measuring its properties.
• It is shielded from present detection by a future version of itself, traveling back in time to thwart your research plans (see here or here).

With the notable exception of that last one, the practical consequence is that you’re essentially looking for a needle in a haystack. Only sometimes the needle looks an awful lot like hay. And in some cases, the needle could actually be lying outside the haystack, in a place you aren’t even looking. We call this hay “background”; the needle, “signal.” Before you can even think about looking for your needle of interest, you first have to get to know the hay.

In general, the bulk of your background is made up of Standard Model processes that resemble your signal but are produced far more copiously. As an added complication, this can be split into two groups: “physics” backgrounds, which actually involve the same “final state” particles as your signal  — that is, those that are measured by the detector and then used to reconstruct the event; and “instrumental” backgrounds, which involve a different final state that is mis-measured by the detector such that it “fakes” looking like your signal. To make matters worse, it’s possible that non-Standard Model (new!) particles similar to your own could interfere with your analysis, adding an entirely theoretical component to your total background. Insidious! You must be aware that yours isn’t necessarily the only needle in this haystack.

(… As is often the case, one person’s trash is another person’s treasure. :))

Assuming you did the research before choosing your particle, you already know the main backgrounds for your signal. Great! Now to study these background processes in a systematic, controlled manner, we use what are called “Monte Carlo” (MC) simulations, aka “fake data.” Although I won’t go into detail about how the MC is generated, I will say that it’s a sophisticated simulation representing our best guess at how the data should look based on both theoretical and experimental constraints. It involves random numbers, probability distributions, lots of computing power, and magic.

Most likely your backgrounds have already been simulated, and all you need to do is get them. Do so. Practically speaking, this is person- and experiment-specific, so I offer no details, but let’s just assume that you now have access to the MC simulated datasets for your main backgrounds — and so the fun can begin! Except it is now 2am, and my workweek is about to start. Nuts!

Next time: Examining your simulated haystack, comparing it to your simulated needle, and finding ways to effectively separate the two with an algorithmic baler.

– Burton


So You Want to Discover A New Particle (Pt. 1)

Tuesday, April 12th, 2011

Hi All,

Perhaps you’ve heard of the Standard Model of Particle Physics. (If you’ve been following Flip’s ongoing series, you’ve certainly heard a lot.) In a nutshell, the Standard Model is a theory describing the fundamental particles of matter and the forces that mediate their interactions, and it’s the theoretical framework in which we at CERN generally understand our experimental data. In the three decades since its formulation, the Standard Model has been extraordinarily successful and accurate in its predictions, and with the notable exception of the SM Higgs boson, all of the pieces to this particle puzzle are already in place.

The Standard Model is so boring.

However, for a variety of reasons that I’ll keep outside the purview of this post, we believe that there’s physics “beyond” the Standard Model. As with most things in high-energy physics (HEP), this has been given a practical acronym: BSM (Beyond the Standard Model) physics. Many BSM theories predict the existence of one or more new (non-SM) particles. Here’s a scandalously abridged list:

  • Supersymmetry (SUSY) predicts “superpartners” or “sparticles” corresponding to every current SM particle
  • in addition to the three generations of matter particles already observed, there could be a fourth, more massive generation consisting of two quarks and two leptons
  • because the SM Higgs just isn’t enough! Little Higgs, Fat Higgs, Composite Higgs, Hidden Higgs …
  • W’ and Z’
  • Leptoquarks

Theorists are very creative! This list could go on for quite a while… 🙂

Given that I’m an experimentalist, however, I’m more directly interested in how one goes about detecting these hypothetical particles. And as an entirely practical matter, the first thing you have to do is actually choose which of these particles you’ll be searching for. This isn’t as simple as it sounds! Here are some general issues to take into consideration when making your decision:

  • How much data is needed for a discovery? Or, alternatively, How large is the production cross-section? If your particle has a large production cross-section, it will be produced in copious amounts by the LHC, and therefore less data is required for you to find it. Since the LHC is still relatively young, and the number of collisions recorded by the experiments is only a tiny fraction of the expected total, many analyses — BSM searches especially! — are limited by statistics. We hope to have about 1 fb-1 of data by the end of this year. If you expect to be sensitive to your particle only with 100 fb-1, then you will be waiting an awfully long time…
  • Is the particle model-independent? It pays to be general. If your particle is entirely dependent on the viability of a particular BSM model, and that model is subsequently ruled out by experimental data, then where does that leave you? Back at the beginning, looking for a new particle to discover. Furthermore, the more general the particle, the less fine-tuned your analysis will be. Many BSM particles resemble each other, at least in a general sense, so you can imagine a situation where you’re so focused on finding one specific particle that you don’t notice another one lurking in the data.
  • Are other people already looking for your particle? Collaboration is essential in a field like ours, but do make sure that there’s room for you on this search before you barge in. Perhaps the other analysts are very territorial. Maybe there are simply too many of them already. Or could it be that you don’t want to share the Nobel Prize when you discover your new particle…? Ask around ahead of time, even email the folks in charge (“conveners”) to find out who is working on what. Given the aforementioned creativity of theorists, there’s sure to be particles still in need of analysts!
  • Is it available at The Particle Zoo? Just sayin.

In truth, these are only a few of the many considerations that go into choosing a new particle to search for. From pure theory to pure politics, this decision is not one to be taken lightly! Think carefully before setting your heart on (and devoting many months of work to) your new particle — then go for it.

— Burton 🙂