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Vector particlesVector

Some terms in particle physics can seem a bit daunting at first—including “vector particles.” Here, two Quantum Diarists explain.

The particle with two names: J/ψ

By Richard Ruiz | August 6, 2014
The J/ψ (or J/psi) is a very special particle. Its discovery was announced in 1974 independently by two groups: one lead by Samuel Ting at Brookhaven National Laboratory (BNL) in New York and the second lead by Burton Richter at Standford Linear Accelerator Center (SLAC) in California.

Higgs to light video comes to light

By Flip Tanedo | August 23, 2011
Particles have an inherent spin. We explored the case of fermions (“spin-1/2″) in a recent post on helicity and chirality. Now we’ll extend this to the case of vector (“spin-1″) particles which describe gauge bosons—force particles.
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Last week I was at a family reunion where I had the chance to talk to one of my more distant relations, Calvin. At 10 years old he seems to know more about particle physics and cosmology than most adults I know. We spent a couple of hours talking about the LHC, the big bang, trying to solve the energy crisis, and even the role of women in science . It turns out that Calvin had wanted to speak with a real scientist for quite a while, so I agreed to have a chat next time I was in the area. To be honest when I first agreed I was rolling my eyes at the prospect. I’ve had so many parents tell me about their children who are “into science” only to find out that they merely watch Mythbusters, or enjoyed reading a book about dinosaurs. However when I spoke to Calvin I found he had huge concentration and insight for someone of his age, and that he was enthusiastically curious about physics to the point where I felt he would never tire of the subject. Each question would lead to another, in the meantime he’d wait patiently for the answer, giving the discussion his full attention. He seemed content with the idea that we don’t have answers to some of these questions yet, or that it can take decades for someone to understand just one of the answers properly. The road to being a scientist is a long one and you’ve got to really want it and work hard to get there, and Calvin has what it takes.

Real scientists don't merely observe, they don't merely interact, they create.  (Child at the Science Museum London, studying an optical exhibit.  Nevit Dilmen 2008)

Real scientists don’t merely observe, they don’t merely interact, they create. (Child at the Science Museum London, studying an optical exhibit. Nevit Dilmen 2008)

Next month Calvin will start his final year in primary school and his teacher will be the same teacher I had at that age, Mark (a great name for a teacher!) From an early age I was fascinated by mathematics and computation, and without Mark I would not have discovered how much fun it was to play with numbers and shapes, something I’ve enjoyed ever since. Without his influence I probably would not have chosen to be a scientist. So once I found out Mark was going to teach Calvin I got in touch and told him that Calvin had the spark within him to get to university, but only if he had the right help along the way. In the area we are from, an industrial town in the North West of England, it is not usual for children to go to university, and there’s often strong peer pressure to not study hard. In this kind of environment it’s important to give encouragement to the children who can do well in academia. (Of course it would be better to change the environments in schools, but changing attitudes and cultures takes decades.)

All this made me think about my own experiences on the way to university, and I’m sure everyone had their own memories of the teachers who inspired them, and the frustrations of how much of high school focuses on learning facts instead of critical thinking. At primary school I had exhausted the mathematics textbooks very early on, under the guidance of Maggie Miller. From there Mark took over and taught me puzzles that went beyond anything I was taught in maths classes at high school. It was unfortunate that I was assigned a rather uninspiring maths teacher who would struggle to understand what I said at times, and it took the school about four years to organise classes that stretched its top students. This was mostly a matter of finding the resources than anything else; the school was caught in the middle of a regional educational crisis, and five small schools were fighting to stay open in a region that could only support four larger schools. One of the schools had to close and that would mean a huge upheaval for everyone. Challenging the brightest students became one of the ways that the school could show its worth and boost its statistics, so the pupils and school worked together to improve both their prospects. Since then the school has encouraged pupils to on extra subjects and exams if they want to, and I’m glad to stay that not only has it stayed open but it’s now going from strength to strength, and I’m glad to have played a very small part in that success.

By the time I was at college there was a whole new level of possibilities, as they had teams dedicated to helping students get to university, and some classes were arranged to fit around the few students that needed them, rather than the other way around. Some of the support still depended on individuals putting in extra effort though, including staff pulling strings to arrange a visit to Oxford where we met with tutors and professors who could give us practice interviews. I realised there was quite a coincidence, because one of the people who gave a practice interview, Bobbie Miller, was the son of Maggie Miller, one of my primary school teachers. At the same time one of my older and more dedicated tutors, Lance, had to take time off for ill health. He invited me and two others over to his house in the evenings for extra maths lessons, some of which went far beyond the scope of the syllabus and instead explored critical and creative mathematical thinking to give us a much deeper understanding of what we were studying. After one of my exams I heard the sad news that he’d passed away, but we knew that he was confident of our success and all three of us got the university positions we wanted, largely thanks to his help.

Unable to thank Lance, I went to visit Maggie Miller and thanked her. It was a surreal experience to go into her classroom and see how small the tables and chairs were, but it brings me back to the main point. Finding tomorrow’s scientists means identifying and encouraging them from an early age. The journey from primary school to university is long, hard, full of distractions and it’s easy to become unmotivated. It’s only through the help of dozens of people putting in extra effort that I got to where I am today, and I’m going to do what I can to help Calvin have the same opportunities. Looking back I am of course very grateful for this, but I also shudder to think of all the pupils who weren’t so lucky, and never got a chance to stretch their intellectual muscles. It doesn’t benefit anyone to let these children fall through the cracks of the educational system simply because it’s difficult to identify those who have the drive to be scientists, or because it’s hard work to give them the support they need. Once we link them up to the right people it’s a pleasure to give them the support they need.

There have always been scientists who have come from impoverished or unlikely backgrounds, from Michael Faraday to Sophie Germaine, who fought hard to find their own way, often educating themselves. Who knows how many more advances we would have today if more of their contemporaries had access to a university education? In many cases the knowledge of children quickly outpaces that of their parents, and since parents can’t be expected to find the right resources the support must come from the schools. On the other hand there are many parents who desperately want their children to do well at school and encourage them to excel in as many subjects as possible (hence my initial skepticism when I first heard Calvin was “into science”.) This means that we also need to be wary of imposing our own biases on children. I can talk about particle physics with Calvin all day, but if he wants to study acoustic engineering then nobody should try to dissuade him from that. Nobody has a crystal ball that can tell them what path Calvin will choose to take, not even Calvin, so he needs the freedom to explore his interests in his own way.

Michael Faraday, a self-taught physicist from a poor background, giving a Royal Society Christmas Lecture, perhaps inspiring aspiring scientists in the audience. (Alexander Blaikley)

Michael Faraday, a self-taught physicist from a poor background, giving a Royal Society Christmas Lecture, perhaps inspiring aspiring scientists in the audience. (Alexander Blaikley)

So how can we encourage young scientists-in-the-making? It can be a daunting task, but from my own experience the key is to find the right people to help encourage the child. Finding someone who can share their joy and experiences of science is not easy, and it may mean second or third hand acquaintances. At the same time, there are many resources online you can use. Give a child a computer, a book of mathematical puzzles, and some very simple programming knowledge, and see them find their own solutions. Take them to museums, labs, and universities where they can meet real scientists who love to talk about their work. The key is to engage them and allow them to take part in the process. They can watch all the documentaries and read all the science books in the world, but that’s a passive exercise, and being a scientist is never passive. If a child wants to be an actor it’s not enough to ask them to read plays, they want to perform them. You’ll soon find out if your child is interested in science because they won’t be able to stop themselves being interested. The drive to solve problems and seek answers is not something that can be taught or taken away, but it can be encouraged or frustrated. Encouraging these interests is a long term investment, but one that is well worth the effort in every sense. Hopefully Calvin will be one of tomorrow’s scientists. He certainly has the ability, but more importantly he has the drive, and that means given the right support he’ll do great things.


“Girls aren’t good at science!”, Calvin said. So I told him that some of the best physicists I know are women. I explained how Marie Curie migrated from Poland to France about a century ago to study the new science of radioactivity, how she faced fierce sexism, and despite all that still became the first person in history to win two Nobel Prizes, for chemistry and physics. If a 10 year old thinks that only men can be good scientists then either the message isn’t getting through properly, or as science advocates we’re failing in our role to make it accessible to everyone. We need to move beyond the images of Einstein, Feynman, Cox, and Tyson in the public image of science.

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Coffee and Code (Part Deux)

Friday, August 29th, 2014

Further to my entry on the CERN Summer Student Webfest 2014 posted a few weeks ago (here), there is a short video about the event available to view HERE. Enjoy!

Youtube

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Do we live in a 2-D hologram?

Tuesday, August 26th, 2014

This Fermilab press release was published on Aug. 26, 2014.

A Fermilab scientist works on the laser beams at the heart of the Holometer experiment. The Holometer will use twin laser interferometers to test whether the universe is a 2-D hologram. Photo: Fermilab

A Fermilab scientist works on the laser beams at the heart of the Holometer experiment. The Holometer will use twin laser interferometers to test whether the universe is a 2-D hologram. Photo: Fermilab

A unique experiment at the U.S. Department of Energy’s Fermi National Accelerator Laboratory called the Holometer has started collecting data that will answer some mind-bending questions about our universe – including whether we live in a hologram.

Much like characters on a television show would not know that their seemingly 3-D world exists only on a 2-D screen, we could be clueless that our 3-D space is just an illusion. The information about everything in our universe could actually be encoded in tiny packets in two dimensions.

Get close enough to your TV screen and you’ll see pixels, small points of data that make a seamless image if you stand back. Scientists think that the universe’s information may be contained in the same way and that the natural “pixel size” of space is roughly 10 trillion trillion times smaller than an atom, a distance that physicists refer to as the Planck scale.

“We want to find out whether space-time is a quantum system just like matter is,” said Craig Hogan, director of Fermilab’s Center for Particle Astrophysics and the developer of the holographic noise theory. “If we see something, it will completely change ideas about space we’ve used for thousands of years.”

Quantum theory suggests that it is impossible to know both the exact location and the exact speed of subatomic particles. If space comes in 2-D bits with limited information about the precise location of objects, then space itself would fall under the same theory of uncertainty. The same way that matter continues to jiggle (as quantum waves) even when cooled to absolute zero, this digitized space should have built-in vibrations even in its lowest energy state.

Essentially, the experiment probes the limits of the universe’s ability to store information. If there is a set number of bits that tell you where something is, it eventually becomes impossible to find more specific information about the location – even in principle. The instrument testing these limits is Fermilab’s Holometer, or holographic interferometer, the most sensitive device ever created to measure the quantum jitter of space itself.

Now operating at full power, the Holometer uses a pair of interferometers placed close to one another. Each one sends a one-kilowatt laser beam (the equivalent of 200,000 laser pointers) at a beam splitter and down two perpendicular 40-meter arms. The light is then reflected back to the beam splitter where the two beams recombine, creating fluctuations in brightness if there is motion. Researchers analyze these fluctuations in the returning light to see if the beam splitter is moving in a certain way – being carried along on a jitter of space itself.

“Holographic noise” is expected to be present at all frequencies, but the scientists’ challenge is not to be fooled by other sources of vibrations. The Holometer is testing a frequency so high – millions of cycles per second – that motions of normal matter are not likely to cause problems. Rather, the dominant background noise is more often due to radio waves emitted by nearby electronics. The Holometer experiment is designed to identify and eliminate noise from such conventional sources.

“If we find a noise we can’t get rid of, we might be detecting something fundamental about nature – a noise that is intrinsic to space-time,” said Fermilab physicist Aaron Chou, lead scientist and project manager for the Holometer. “It’s an exciting moment for physics. A positive result will open a whole new avenue of questioning about how space works.”

The Holometer experiment, funded by the U.S. Department of Energy Office of Science and other sources, is expected to gather data over the coming year.

The Holometer team comprises 21 scientists and students from Fermilab, the Massachusetts Institute of Technology, the University of Chicago and the University of Michigan. For more information about the experiment, visit http://holometer.fnal.gov/.

Fermilab is America’s premier national laboratory for particle physics and accelerator research. A U.S. Department of Energy Office of Science laboratory, Fermilab is located near Chicago, Illinois, and operated under contract by the Fermi Research Alliance, LLC. Visit Fermilab’s website at www.fnal.gov and follow us on Twitter at @FermilabToday.

The DOE Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

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This Fermilab press release came out on Aug. 18, 2014.

This image of the NGC 1398 galaxy was taken with the Dark Energy Camera. This galaxy lives in the Fornax cluster, roughly 65 million light-years from Earth. It is 135,000 light-years in diameter, just slightly larger than our own Milky Way galaxy, and contains more than 100 billion stars. Credit: Dark Energy Survey

This image of the NGC 1398 galaxy was taken with the Dark Energy Camera. This galaxy lives in the Fornax cluster, roughly 65 million light-years from Earth. It is 135,000 light-years in diameter, just slightly larger than our own Milky Way galaxy, and contains more than 100 billion stars. Credit: Dark Energy Survey

On Aug. 15, with its successful first season behind it, the Dark Energy Survey (DES) collaboration began its second year of mapping the southern sky in unprecedented detail. Using the Dark Energy Camera, a 570-megapixel imaging device built by the collaboration and mounted on the Victor M. Blanco Telescope in Chile, the survey’s five-year mission is to unravel the fundamental mystery of dark energy and its impact on our universe.

Along the way, the survey will take some of the most breathtaking pictures of the cosmos ever captured. The survey team has announced two ways the public can see the images from the first year.

Today, the Dark Energy Survey relaunched Dark Energy Detectives, its successful photo blog. Once every two weeks during the survey’s second season, a new image or video will be posted to www.darkenergydetectives.org, with an explanation provided by a scientist. During its first year, Dark Energy Detectives drew thousands of readers and followers, including more than 46,000 followers on its Tumblr site.

Starting on Sept. 1, the one-year anniversary of the start of the survey, the data collected by DES in its first season will become freely available to researchers worldwide. The data will be hosted by the National Optical Astronomy Observatory. The Blanco Telescope is hosted at the National Science Foundation’s Cerro Tololo Inter-American Observatory, the southern branch of NOAO.

In addition, the hundreds of thousands of individual images of the sky taken during the first season are being analyzed by thousands of computers at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, Fermi National Accelerator Laboratory (Fermilab), and Lawrence Berkeley National Laboratory. The processed data will also be released in coming months.

Scientists on the survey will use these images to unravel the secrets of dark energy, the mysterious substance that makes up 70 percent of the mass and energy of the universe. Scientists have theorized that dark energy works in opposition to gravity and is responsible for the accelerating expansion of the universe.

“The first season was a resounding success, and we’ve already captured reams of data that will improve our understanding of the cosmos,” said DES Director Josh Frieman of the U.S. Department of Energy’s Fermi National Accelerator Laboratory and the University of Chicago. “We’re very excited to get the second season under way and continue to probe the mystery of dark energy.”

While results on the survey’s probe of dark energy are still more than a year away, a number of scientific results have already been published based on data collected with the Dark Energy Camera.

The first scientific paper based on Dark Energy Survey data was published in May by a team led by Ohio State University’s Peter Melchior. Using data that the survey team acquired while putting the Dark Energy Camera through its paces, they used a technique called gravitational lensing to determine the masses of clusters of galaxies.

In June, Dark Energy Survey researchers from the University of Portsmouth and their colleagues discovered a rare superluminous supernova in a galaxy 7.8 billion light years away. A group of students from the University of Michigan discovered five new objects in the Kuiper Belt, a region in the outer reaches of our solar system, including one that takes over a thousand years to orbit the Sun.

In February, Dark Energy Survey scientists used the camera to track a potentially hazardous asteroid that approached Earth. The data was used to show that the newly discovered Apollo-class asteroid 2014 BE63 would pose no risk.

Several more results are expected in the coming months, said Gary Bernstein of the University of Pennsylvania, project scientist for the Dark Energy Survey.

The Dark Energy Camera was built and tested at Fermilab. The camera can see light from more than 100,000 galaxies up to 8 billion light-years away in each crystal-clear digital snapshot.

“The Dark Energy Camera has proven to be a tremendous tool, not only for the Dark Energy Survey, but also for other important observations conducted year-round,” said Tom Diehl of Fermilab, operations scientist for the Dark Energy Survey. “The data collected during the survey’s first year — and its next four — will greatly improve our understanding of the way our universe works.”

The Dark Energy Survey Collaboration comprises more than 300 researchers from 25 institutions in six countries. For more information, visit http://www.darkenergysurvey.org.

Fermilab is America’s premier national laboratory for particle physics and accelerator research. A U.S. Department of Energy Office of Science laboratory, Fermilab is located near Chicago, Illinois, and operated under contract by the Fermi Research Alliance, LLC. Visit Fermilab’s website at www.fnal.gov and follow us on Twitter at @FermilabToday.

The DOE Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

The National Optical Astronomy Observatory (NOAO) is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under cooperative agreement with the National Science Foundation.

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The Particle Clicker team working late into the night.

The Particle Clicker team working late into the night.

This article was also published here on CERN’s website.

This weekend CERN hosted its third Summer Student Webfest, a three-day caffeine-fuelled coding event at which participants worked in small teams to build innovative projects using open-source web technologies.

There were a host of projects to inspire the public to learn about CERN and particle physics, and others to encourage people to explore web-based solutions to humanitarian disasters with CERN’s partner UNOSAT.

The event opened with a session of three-minute pitches: participants with project ideas tried to recruit team members with particular skills, from software development and design expertise to acumen in physics. Projects crystallised, merged or floundered as 14 pitches resulted in the formation of eight teams. Coffee was brewed and the hacking commenced…

Run Broton Run

Members of the Run Broton Run team help each other out at the CERN Summer Student Webfest 2014 (Image: James Doherty)

The weekend was interspersed with mentor-led workshops introducing participants to web technologies. CERN’s James Devine detailed how Arduino products can be used to build cosmic-ray detectors or monitor LHC operation, while developers from PyBossa provided an introduction to building crowdsourced citizen science projects on crowdcrafting.org. (See a full list of workshops).

After three days of hard work and two largely sleepless nights, the eight teams were faced with the daunting task of presenting their projects to a panel of experts, with a trip to the Mozilla Festival in London up for grabs for one member of the overall winning team. The teams presented a remarkable range of applications built from scratch in under 48 hours.

Students had the opportunity to with Ben Segal, an inductee of the Internet Hall of Fame.

Students had the opportunity to collaborate with Ben Segal (middle), inductee of the Internet Hall of Fame.

Prizes were awarded as follows:

Best Innovative Project: Terrain Elevation

A mobile phone application that accurately measures elevation. Designed as an economical method of choosing sites with a low risk of flooding for refugee camps.

Find out more.

Best Technology Project: Blindstore

A private query database with real potential for improving online privacy.

Find out more here.

Best Design Project: GeotagX and PyBossa

An easy-to-use crowdsourcing platform for NGOs to use in responding to humanitarian disasters.

Find out more here and here.

Best Educational Project: Run Broton Run

An educational 3D game that uses Kinect technology.

Find out more here.

Overall Winning Project: Particle Clicker

Particle Clicker is an elegantly designed detector-simulation game for web.

Play here.

“It’s been an amazing weekend where we’ve seen many impressive projects from different branches of technology,” says Kevin Dungs, captain of this year’s winning team. “I’m really looking forward to next year’s Webfest.”

Participants of the CERN Summer Student Webfest 2014 in the CERN Auditorium after three busy days' coding.

Participants of the CERN Summer Student Webfest 2014 in the CERN Auditorium after three busy days’ coding.

The CERN Summer Student Webfest was organised by François Grey, Ben Segal and SP Mohanty, and sponsored by the Citizen Cyberlab, Citizen Cyberscience Centre, Mozilla Foundation and The Port. Event mentors were from CERN, PyBossa and UNITAR/UNOSTAT. The judges were Antonella del Rosso (CERN Communications), Bilge Demirkoz (CERN Researcher) and Fons Rademakers (CTO of CERN Openlab).

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The World’s Largest Detector?

Wednesday, August 13th, 2014

This morning, the @CERN_JOBS twitter feed tells us that the ATLAS experiment is the world’s largest detector:

CERN_JOBS Tweet Largest Detector

Weighing over 7,000 tons, 46 meters long, and 25 meters high, ATLAS is without a doubt the particle detector with the greatest volume ever built at a collider. I should point out, though, that my experiment, the Compact Muon Solenoid, is almost twice as heavy at over 12,000 tons:

CMS

CMS is smaller but heavier — which may be why we call it “compact.” What’s the difference? Well, it’s tough to tell from the pictures, in which CMS is open for tours and ATLAS is under construction, but the big difference is in the muon systems. CMS has short gaps between muon-detecting chambers, while ATLAS has a lot of space in order to allow muons to travel further and get a better measurement. That means that a lot of the volume of ATLAS is actually empty air! ATLAS folks often say that if you could somehow make it watertight, it would float; as a CMS member, I heartily recommend attempting to do this and seeing if it works. ;)

But the truth is that all this cross-LHC rivalry is small potatoes compared to another sort of detector: the ones that search for neutrinos require absolutely enormous volumes of material to get those ghostlike particles to interact even occasionally! For example, here’s IceCube:

"Icecube-architecture-diagram2009" by Nasa-verve - IceCube Science Team - Francis Halzen, Department of Physics, University of Wisconsin. Licensed under Creative Commons Attribution 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Icecube-architecture-diagram2009.PNG#mediaviewer/File:Icecube-architecture-diagram2009.PNG

Most of its detecting volume is actually antarctic ice! Does that count? If it does, there may be a far bigger detector still. To follow that story, check out this 2012 post by Michael Duvernois: The Largest Neutrino Detector.

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Watch Fermilab Deputy Director Joe Lykken in the latest entry in Huffington Post's "Talk Nerdy To Me" video series.

Watch Fermilab Deputy Director Joe Lykken in the latest entry in Huffington Post’s “Talk Nerdy To Me” video series.


What’s the smallest thing in the universe? Check out the latest entry in Huffington Post‘s Talk Nerdy to Me video series. Host Jacqueline Howard takes the viewer inside Fermilab and explains how scientists look for the smallest components that make up our world. Fermilab Deputy Director Joe Lykken talks about the new discoveries we hope to make in exploring the the subatomic realm.

View the 3-minute video at Huffington Post.

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This article appeared in Fermilab Today on Aug. 6, 2014.

Yale University astrophysicist Meg Urry spoke about gender bias in science at the July 30 Fermilab Colloquium. Photo: Lauren Biron

Yale University astrophysicist Meg Urry spoke about gender bias in science at the July 30 Fermilab Colloquium. Photo: Lauren Biron

Both men and women need to improve how they evaluate women in the sciences to help eliminate bias, says Meg Urry, who spoke at last week’s Fermilab Colloquium. People of either gender fall victim to unconscious prejudices that affect who succeeds, particularly in physics.

“Less than 20 percent of the Ph.D.s in physics go to women,” Urry noted, a figure that has barely crept up even while fields such as medicine have approached parity.

Urry, a professor at Yale University and president of the American Astronomical Society, unleashed a torrent of studies demonstrating bias during her talk, “Women in Physics: Why So Few? And How to Move Toward Normal.”

In one example, letters of recommendation for men were more likely to include powerful adjectives and contain specifics, while those for women were often shorter, included hints of doubt or made explicit mention of gender.

Another study found that in jobs that were perceived as masculine, both men and women tended to award the position to the man even when the woman was the qualified individual.

Other data showed that women are less likely to be perceived as the leader in mixed-gender scenarios, Urry said. When small numbers of women are present, they can become an “other” that stands in for the whole gender, magnifying perceived mistakes and potentially confirming a bias that women are less proficient in physics.

“You need a large enough group that people stop thinking of them as the woman and start thinking of them as the scientist,” Urry said.

Urry advised the many young women in the audience to own their ambition, prep their elevator speeches, get male allies who will stand up if female voices are ignored, practice confidence and network. Above all, she said, work hard, do interesting work, and don’t be discouraged if things get rough.

Meanwhile, Urry said, leaders need to learn about bias, actively look for diverse candidates rather than wait for applications, mentor and prevalidate women, such as when introducing a speaker.

Urry worked hard to debunk the myth that hiring more women means lowering the bar for diversity’s sake.

“When you hire a diverse group of scientists, you are improving your quality, not lowering your standards,” Urry said, echoing sentiments from her lunchtime talk with 40 women. “We should be aspiring to diversity of thought to enrich science.”

Lauren Biron

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J/ψ

Wednesday, August 6th, 2014

The particle with two names: The J/ψ Vector Meson. Again, under 500 words.

jpsi_NOVA

Trident decay of J/Psi Credit: SLAC/NOVA

Hi All,

The J/ψ (or J/psi) is a very special particle. Its discovery was announced in 1974 independently by two groups: one lead by Samuel Ting at Brookhaven National Laboratory (BNL) in New York and the second lead by Burton Richter at Standford Linear Accelerator Center (SLAC) in California. J/ψ is special because it established the quark model as a credible description of nature. Having been invented by Gell-Man and Zweig as a bookkeeping tool, it was not until Glashow, Iliopoulos and Maiani (GIM) that the concept of quarks as real particles was taken seriously. GIM predicted that if quarks were real, then they should come in pairs, like the  up and down quarks. Candidates for the up, down, and strange were identified, but there was no partner for the strange quark. J/ψ was the key.

ting-group-335px_BNL

Samuel Ting and his BNL team. Credit: BNL

Like the proton or an atom, the J/ψ is a composite particle. This means that J/ψ is made of smaller, more elementary particles. Specifically, it is a bound state of  one charm quark and one anticharm quark. Since it is made of quarks, it is a “hadron“. But since it is made of exactly one quark and one antiquark, it is specifically a “meson.” Experimentally, we have learned that the  J/ψ has an intrinsic angular momentum (spin) of 1ħ (same as the photon), and call it a “vector meson.” We infer that the charm and anticharm, which are both spin ½ħ, are aligned in the same direction (½ħ + ½ħ = 1ħ). The J/ψ must also be electrically neutral because charm and anticharm quarks have equal but opposite electric charges.

richter_SLAC

Burton Richter following the announcement of co-winning the 1976 Nobel Prize. Credit: SLAC

At 3.1 GeV/c², the J/ψ is a about three times heavier than the proton and about three-quarters the mass of the bottom quark. However, because so few hadrons are lighter than it, the J/ψ possesses a remarkable feature: it decays 10% of the time to charged leptons, like an electron-positron pair. By conservation of energy, it is forbidden to decay to heavier hadrons. Because there are so few  J/ψ decay modes, it is appears as a very narrow peak in experiments. In fact, the particle’s mass and width are so well-known that experiments like ATLAS and CMS use them as calibration markers.

Credit: CMS

Drell-Yan spectrum data at 7 TeV LHC Credit: CMS

The J/ψ meson is one of the coolest things in the particle zoo. It is a hadronic bound state that decays into charged leptons. It shares the same quantum numbers as the photon and Z boson, so it appears as a Drell-Yan processes. It established the quark model, and is critical to new discoveries because of its use as a calibration tool. In my opinion, not too shabby.

Happy colliding.

Richard (@BraveLittleMuon)

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Super Fracking and Physics

Tuesday, August 5th, 2014

The cover story of the latest issue of Physics Today is part explanation, part discussion of the use of fracking techniques in the oil and natural gas industries in America. As this topic gained traction in the news and online, I was always admittedly ignorant when it came to the actual science and details of these methods. I vaguely knew that fracking could be seen as beneficial in that many US power plants now burn cleaner natural gas instead of coal, but it also seemed obvious that pumping high pressure liquid (which isn’t pure water) into the ground was bound to cause other environmental problems. Still, I neither consider myself strongly for nor against these practices, but I did greatly appreciate the explanations and discussions provided in this article. Below I’ll highlight the parts I found interesting, but I do recommend that the interested reader take a look at the article.

Fractures in siltstone and black shale in the Utica shale, near Fort Plain, New York. (Photograph by Michael C. Rygel.)

The article begins with an explanation of black shale itself. At left is a picture of some black shale, part of the Utica shale in upstate New York. So what is black shale? Well, to quote the article: “Just as sandstones are a rock equivalent of sand, shales are a rock equivalent of mud.” Organic material, oil and/or gas, trapped in the shale gives it the darker color and name, black shale. The oil and gas will only remain in the shale under anoxic conditions. No need to open that extra browser tab, I had to look up what anoxic meant too. Anoxic water is water depleted of much of the dissolved oxygen that is typically in water, this usually happens when water is left stagnant. The dissolved oxygen in normal water would tend to oxidize the carbon in the sediment, destroying the organic material. Under the right conditions, roughly 2-4 km beneath the Earth’s surface, the heat and pressure will convert the organic material into oil. Go a bit further down, roughly 3-6 km, and the temperature and pressure rises, breaking the oil down into gas.

As most people are now aware, the general idea of fracking is to pump liquid into the black shale, causing fractures in the rock which allows the oil and gas to escape its confines and be collected. Three categories of fracking can be distinguished. The first is natural fracking, which is to say, the normal fracturing of shale due to the internal pressure of oil and gas, the fractures in the picture above are due to natural fracturing. Sometimes natural fractures allow oil and gas to escape the shale, the largest such natural seepage area can be found off the coast of Santa Barbara, California. The other methods of fracking are described in the figure below. The main differences pointed out in the article were the volume and viscosity of the water used to carry out the hydraulic fracking. In traditional fracking, water is made viscous by adding guar gum or hydroxyethyl cellulose. Typically about 75-1000 cubic meters of water are used to create a single fracture though which the oil and/or gas may be extracted. High-voulme (or super) fracking, on the other hand, uses a low viscosity water based liquid pumped at a high rate to create many smaller fracture networks along a horizontal well that is periodically plugged to create a number of fracking sites. The water usage is typically 100 times greater in high-volume fracking as compared to traditional fracking. The benefit, of course, is that high-volume fracking is capable of extracting oil and gas from tight shale formations where either few natural fractures exist for the oil and gas to migrate though, or the natural fractures have been sealed over time by the deposition of silica and/or carbonates. For a detailed layout of the environmental concerns surrounding high-volume fracking, see the insert within the main article. 

Traditional and high-volume fracking. (a) In traditional fracking treatments, a high-viscosity fluid creates a single hydraulic fracture through which oil or gas (or both) migrates to the production well. (b) In high-volume fracking, or super fracking, large volumes of a low-viscosity liquid create a wide distribution of hydraulic fractures. Fossil fuels can then migrate through the fracture network to the production well. The sketch here shows the result of a sequence of four high-volume fracking injections. Such sequential injections would not be possible without directional drilling, which creates a horizontal production well in the target stratum.

The authors of this article found their way to studying fracking because of the occurrence of small earthquakes associated with high-volume fracking. Some production wells now monitor the seismic activity of the fracking with a series of seismometers distributed along the length of a monitoring well. Better earthquake prediction models would allow for better emergency preparedness by governments, more robust risk analysis by insurers, and possibly even save lives of those living in earthquake prone areas. So, from a research perspective, the earthquakes induced by fracking can provided a useful testbed for earthquake modeling. Below is a map of microseismicity associated with the Barnett shale in Texas. The monitoring well is situated at the origin, and each dot (or I guess + mark) represents a unique seismic event.

Small earthquakes associated with four high-volume frackings of the Barnett shale in Texas. Each tiny “+” symbol on this microseismicity map shows the epicenter of a microearthquake. Collectively, the symbols reveal the distribution of fractures induced by the injected water. The monitoring well is at the origin of the coordinate system shown. The injection well is off to the right; the thin line shows its horizontal extent. (Adapted from: S.Maxwell, Leading Edge 30, 340 (2011))

These small earthquakes are typically very weak and can not be felt on the surface. The frequency of natural earthquakes of a certain magnitude or greater follows a well defined function where the logarithm of the number of earthquakes with magnitude m or greater decreases linearly with m. This is just to say that small earthquakes are common and big earthquakes are rare. Studying both natural and fracking induced earthquakes, the distribution of earthquake magnitudes from high-volume fracking have a steeper fall off than natural earthquakes, meaning that a large earthquake would be extremely rare, but not ruled out. The authors quote that the probability of seeing a magnitude 4 earthquake (minimally damaging) from high-volume fracking is less than on in a billion. An effort has been made by an old acquaintance of mine, J. Quinn Norris at UC Davis to model the fracking earthquakes using “a type of graph-theory analysis called invasion percolation from a point source.” See his paper here.

The last part of the article that I found particularly interesting was the estimates from the Department of Energy in 2011 on the availability of recoverable oil in the 48 contiguous states. The total estimated volume of recoverable oil was 24 billion barrels. Of this, 3.6 billion barrels are attributed to the Bakken shale, mostly in North Dakota, and 15.4 billion barrels are expected from the Monterey shale along the coast of California. As a California native this was surprising to me, and is probably so because efforts to use high volume fracking on this shale have so far proved unfruitful because of the natural fractures which already exist. Maybe think of it like trying to fracture a sponge by pushing water through it, where the water will happily fill every nook and cranny instead of build up any pressure. Still, this source is likely to play some part in future energy discussions as other sources are depleted. Of course, just because this material exists does not mean we must burn it to satisfy our energy needs. Most of this oil and gas has been locked away for hundreds of millions of years and it would gladly remain so if we allowed it to. I for one am optimistic that fossil fuel consumption will significantly decrease within my lifetime and we can get on with solar powered hovercrafts and the like.

 

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