Stephen Sekula

Dallas, TX, USA

Husband; Associate Professor of Physics; I teach at SMU in Dallas, TX; I study the Higgs Particle with the ATLAS Experiment at the Large Hadron Collider at CERN; writer and blogger; drummer; programmer; teacher; scientist; traveler; runner; gardener; open-source aficionado.

  • JanKusanagi at 2020-01-11T15:33:55Z

    Snow!!! 🌨☃🏔

    Haven't personally seen it in a long time, either.

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  • Astronomy Picture of the Day for 2019-12-04 12:30:02.204057

    Astronomy Picture of the Day (Unofficial) at 2019-12-04T18:30:03Z

    Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

    2019 December 4
    See Explanation.  Clicking on the picture will download
the highest resolution version available.

    Electric Night
    Image Credit & Copyright: Ivan Pedretti

    Explanation: It may appear, at first, like the Galaxy is producing the lightning, but really it's the Earth. The featured nighttime landscape was taken from a southern tip of the Italian Island of Sardinia in early June. The foreground rocks and shrubs are near the famous Capo Spartivento Lighthouse, and the camera is pointed south toward Algeria in Africa. In the distance, across the Mediterranean Sea, a thunderstorm is threatening, with several electric lightning strokes caught together during this 25-second wide-angle exposure. Much farther in the distance, strewn about the sky, are hundreds of stars in the neighborhood of our Sun in the Milky Way Galaxy. Farthest away, and slanting down from the upper left, are billions of stars that together compose the central band of our Milky Way.

    Free Lecture: APOD editor to speak in NYC on January 3
    Tomorrow's picture: open space

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  • Astronomy Picture of the Day for 2019-11-24 12:30:01.993143

    Astronomy Picture of the Day (Unofficial) at 2019-11-24T18:30:02Z

    Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

    2019 November 24
    See Explanation.  Clicking on the picture will download
the highest resolution version available.

    Apollo 12: Self-Portrait
    Image Credit: NASA, Apollo 12, Charles Conrad

    Explanation: Is this image art? 50 years ago, Apollo 12 astronaut-photographer Charles "Pete" Conrad recorded this masterpiece while documenting colleague Alan Bean's lunar soil collection activities on Oceanus Procellarum. The featured image is dramatic and stark. The harsh environment of the Moon's Ocean of Storms is echoed in Bean's helmet, a perfectly composed reflection of Conrad and the lunar horizon. Works of photojournalists originally intent on recording the human condition on planet Earth, such as Lewis W. Hine's images from New York City in the early 20th century, or Margaret Bourke-White's magazine photography are widely regarded as art. Similarly many documentary astronomy and space images might also be appreciated for their artistic and esthetic appeal.

    Tomorrow's picture: a bat glow

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  • Alexandre Oliva at 2019-11-01T13:18:03Z

    I object to such smearing labeling!
    we are the 99%, and we are no ordinary matter! </joke>

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  • Multimessenger Diversity Network welcomes new members, discusses future efforts in July meeting

    ParticleNews at 2019-08-07T22:28:54Z

    "Multimessenger Diversity Network welcomes new members, discusses future efforts in July meeting"

    From July 22-24, the Multimessenger Diversity Network (MDN) met at the Wisconsin IceCube Particle Astrophysics Center, located at the University of Wisconsin–Madison, the lead institution of the IceCube Neutrino Observatory.

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  • HPR2872: Shoe Lace Tips

    PumpCast at 2019-08-06T00:13:43Z

    "HPR2872: Shoe Lace Tips"

    In this episode I give some shoe lace tips

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  • LZ Time Projection Chamber assembly completed

    ParticleNews at 2019-08-06T17:28:38Z

    "LZ Time Projection Chamber assembly completed"

    LZ Time Projection Chamber assembly completedPress ReleaseLauren Tue, 08/06/2019 - 08:473219

    Collaboration puts together the 'heart' of LUX-ZEPLIN dark matter detector

    The recently assembled LUX-ZEPLIN xenon detector in the Surface Assembly Lab cleanroom at Sanford Underground Research Facility on July 26, 2019.

    Photo by Matthew Kapust Sanford Underground Research Facility.

    On July 26, researchers working in the Surface Assembly Lab (SAL) at the Sanford Underground Research Facility (Sanford Lab) had quite an audience. Nearly a dozen onlookers, including researchers, technicians and one very curious writer, peered through two windows into the cleanroom. From this vantage point, they watched researchers carefully peel back a protective layer of foil to reveal—for perhaps the last time in half a decade—the innermost piece of the LUX-ZEPLIN (LZ) dark matter experiment. 

    LZ Completes TPC Assembly from Sanford Lab on Vimeo.

    What they revealed was LZ’s xenon detector, called a Time Projection Chamber, or TPC. Researchers recently completed the assembly of this impressive structure, a gleaming white column standing nearly nine-feet tall, that houses key components needed for LZ’s dark matter search. 

    “This xenon detector will be at the heart of the LZ dark matter experiment,” said Henrique Araújo, Imperial College London, who leads the LZ collaboration efforts in the UK and co-led the development of the TPC with Tom Shutt from SLAC National Accelerator Laboratory (SLAC). The U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) is leading the LZ project.

    “The TPC is a complex system and it's a major achievement to have it fully assembled,” Shutt said.  “It takes us one important step closer to being able to look for dark matter. It is also gratifying because it involved assembling a large number of sub-systems designed and built by groups across the US and the UK over a number of years. So, it’s a coming together of sorts for the collaboration.”

    While it was unwrapped, researchers in full-body cleanroom suits took final measurements and ran tests on the instrument, which will soon be sealed inside a cryostat vessel and transported to the 4850 Level of Sanford Lab. Once installed underground, the TPC will be hidden within layers of protective shielding until the experiment has finished taking data.

    “We have some things in common with a space program,” said Araújo. “Before you launch, you do all of your work on the ground for years, perfecting the engineering so your instrument will work no matter what. LZ is a bit like a space experiment, just headed the opposite direction. We cannot expose it to underground air—that would compromise its performance. Once you deploy it underground, that's it. It has to work.”

    Piecing together the detector

    The assembly of the TPC began in December 2018, when components first began arriving at Sanford Lab. Dozens of institutions across the globe had been fabricating components since 2015 or participating in the assembly. 

    “In creating these components, we paid a lot of attention to selecting and screening materials with low radioactive contamination and low radon emission to lessen any potential background interference within the detector,” said Tomasz Biesiadzinski, a project scientist with SLAC who has led the assembly effort at Sanford Lab. In all, tens of thousands of specially designed components were integrated into the detector."

    Since December 2018, the assembly team tallied 13,500 working hours at the SAL and drew from a broad reserve of expertise to properly address the mechanical, optical, electrical, cleanliness and background requirements of each component. With 250 members from 37 institutions around the globe and support from Sanford Lab’s support scientists and engineers, expertise covering all these areas was readily available. 

    “This type of experiment is still done the old-fashioned way—where the principal investigators, students, postdocs, engineers and technicians all work together to build it,” said Araújo. “The expertise that you need in order to assemble the experiment is so vast that you have to have a diverse group onsite. And working alongside people from these different backgrounds adds great joy to our time here.”

    Cleanliness campaign

    One researcher who contributed a substantial number of those hours was Nicolas Angelides, LZ collaboration member and graduate student at University College London, who presided over much of the cleanliness program for the TPC assembly. 

    “Dust particles can disrupt the detector signals,” said Angelides. “Dust also contains trace amounts of radioactivity, creating a background we need to control ahead of time.” 

    To protect against stray dust particles and radon—an atmospheric gas that could contaminate the detector—the entire assembly process took place within the Surface Assembly Lab, a laboratory space with a radon-reduction system and a class-100 clean room outfitted specifically for the TPC assembly. Within the clean space, strict cleanliness protocols are followed.

    “All walls and floors are vacuumed and wiped down at least every week. Anything that can’t be wiped is put in an ultra-sonic bath, where sound waves are sent through a solvent to dislodge all small particles from every nook and cranny,” said Angelides. 

    High-efficiency air filters remove dust particles, some smaller than a single organic cell. If the air-particle concentration inside the room gets too high, an alarm will sound, alerting researchers to cover the detector. Because static electricity attracts dust, the assembly area is surrounded by neutralizing fans that quickly dissipate static charge. A total of twenty-six of these fans were pointed at the TPC alone.

    Workers themselves pose a contamination risk to the experiment, as humans are a major source of dust. “We wear full-coverage cleanroom suits and follow a two-stage gowning procedure,” said Angelides. “Every step closer to entering the cleanroom is held to higher cleanliness standards and requires additional levels of gear. It takes a good quarter of an hour just to get to work!” 

    “What LZ has done more than any other project in the field is control the cleanliness of the materials and the assembly process,” said Araújo. “At the end of the day, nothing goes into the cleanroom or touches the detector that is not extremely clean.” 

    Generations of design

    The design of LZ’s detector has been developed over decades of experimentation, including multiple iterations of the ZEPLIN program and the Large Underground Xenon (LUX) detector, from which LZ derives its name. The ZEPLIN program was the first to develop the liquid xenon TPC concept employed by LZ. In 2013, LUX had been declared the most sensitive dark matter detector in the world and retained that status until 2017—one year after it had been decommissioned. 

    “LZ sits on the shoulders of a number of smaller experiments,” said Araújo. “Each experiment solved their own issues at their own scale. By getting larger one step at a time, we have been able to search for new physics with ever larger experiments, and we are confident that LZ will work as it is designed to.” 

    Once underground, the detector will be cooled down and filled with ten tons of liquid xenon. This very dense liquid is an ideal medium for dark matter detection. 

    Researchers believe that if a dark matter particle interacts with a xenon atom, it will produce two flashes of light. The first flash occurs when the particle collides with the xenon atom; from this interaction some electrons are shaken off the xenon too. Then, guided by an imposed electric field, the electrons drift toward the top of the detector and are accelerated through a layer of gaseous xenon above the liquid, producing a second flash of light. 

    Although these flashes would be imperceptible to the human eye, the detector is lined with hundreds of photomultiplier tubes. These ultrasensitive sensors are capable of amplifying a signal from even a single photon of light. 

    “This TPC concept in which a single interaction produces two signals—the primary and secondary scintillations—is a powerful way to detect radiation,” Araújo said. “This is the technology that has been leading these dark matter searches because it allows us to say, with the precision of a few millimeters, where each interaction happens, and whether it is signal-like or background-like, which we can tell by the relative sizes of the two flashes of light.”

    Direct detection of dark matter

    Rigorous cleanliness standards, meticulous engineering and decades of experience all push LZ closer to its goal: detecting dark matter.

    “A leading candidate for dark matter is the weakly interacting massive particle,” said Araújo. Different experiments world-wide are looking for this particle, endearingly nicknamed the WIMP (weakly interacting massive particle), within different regions of mass. LZ is designed to search for a particle within a mass region of a few protons to a few tens of thousands of protons. 

    “If there are particles in that mass range, we should have the world-leading sensitivity to spot them first,” said Araújo.

    Major support for LZ comes from the DOE Office of Science, the South Dakota Science and Technology Authority, the UK’s Science & Technology Facilities Council and by collaboration members in South Korea and Portugal.

    Researchers peel back a protective layer of aluminum foil, revealing the recently assembled LUX-ZEPLIN xenon detector in the Surface Assembly Lab cleanroom at Sanford Underground Research Facility on July 26, 2019. Photo by Matthew Kapust, Sanford Underground Research Facility.

    Researchers examine the foil-wrapped LUX-ZEPLIN xenon detector that was recently assembled in the Surface Assembly Lab cleanroom at Sanford Underground Research Facility on July 26, 2019. Photo by Matthew Kapust, Sanford Underground Research Facility.



    The recently assembled LUX-ZEPLIN xenon detector stands nearly 9 feet tall in the Surface Assembly Lab cleanroom at Sanford Underground Research Facility on July 26, 2019. Photo by Nick Hubbard, Sanford Underground Research Facility.

    A researcher takes measurements of the recently assembled LUX-ZEPLIN xenon detector in the Surface Assembly Lab cleanroom at Sanford Underground Research Facility on July 26, 2019. Photo by Nick Hubbard, Sanford Underground Research Facility.


    A researcher snaps a photograph of the recently assembled LUX-ZEPLIN xenon detector in the Surface Assembly Lab cleanroom at Sanford Underground Research Facility on July 26, 2019. Photo by Nick Hubbard, Sanford Underground Research Facility.

    The recently assembled LUX-ZEPLIN xenon detector in the Surface Assembly Lab cleanroom at Sanford Underground Research Facility on July 26, 2019. Photo by Matthew Kapust, Sanford Underground Research Facility.

    A close-up of the top of the recently assembled LUX-ZEPLIN xenon detector in the Surface Assembly Lab cleanroom at Sanford Underground Research Facility on July 26, 2019. White PTFE reflective paneling lines much of the detector. From the outside, a viewer can see the stainless-steel outer rings of the electric grids, the back of the PMT array and some of the PMT cabling. Photo by Nick Hubbard, Sanford Underground Research Facility.


    Under ultraviolet light, research check for dust on the detector. Photo By: Nicolas Angelides, LZ Collaboration.

    Sanford Underground Research Facility


    The Sanford Underground Research Facility (SURF) houses world-leading physics experiments that could give us a better understanding of the universe. Located at the former Homestake Gold Mine in Lead, S.D., SURF provides significant depth and rock stability—a near-perfect environment for experiments that need to escape cosmic radiation that can interfere with the detection of rare physics events.

    Sanford Underground Research Facility
    630 E. Summit Street
    Lead, SD57774
    United States

    (605) 722-8650

    Constance Walter
    Communications Director

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  • Stephen Sekula at 2019-08-03T15:00:55Z

    Ah. Hello there, rain... I missed you. My rain barrels also missed you.

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  • Powered by pixels

    ParticleNews at 2019-08-01T16:28:10Z

    "Powered by pixels"

    An innovative use of pixel technology is making liquid-argon neutrino detectors even better. 

    Pixel electronics

    It’s 2019. We want our cell phones fast, our computers faster and screens so crisp they rival a morning in the mountains. We’re a digital society, and blurry photos from potato-cameras won’t cut it for the masses. Physicists, it turns out, aren’t any different — and they want that same sharp snap from their neutrino detectors.

    Cue ArgonCube: a prototype detector under development that’s taking a still-burgeoning technology to new heights with a plan to capture particle tracks worthy of that 4K TV. The secret at its heart? It’s all about the pixels.

    But let’s take two steps back. Argon is an element that makes up about 1 percent of that sweet air you’re breathing. Over the past several decades, the liquid form of argon has grown into the medium of choice for neutrino detectors. Neutrinos are those pesky fundamental particles that rarely interact with anything but could be the key to understanding why there’s so much matter in the universe.

    Big detectors full of cold, dense argon provide lots of atomic nuclei for neutrinos to bump into and interact with — especially when accelerator operators are sending beams containing trillions of the little things. When the neutrinos interact, they create showers of other particles and lights that the electronics in the detector capture and transform into images.

    Each image is a snapshot that captures an interaction by one of the most mysterious, flighty, elusive particles out there; a particle that caused Wolfgang Pauli, upon proposing it in 1930, to lament that he thought experimenters would never be able to detect it.

    View from above of the ArgonCube testing facility

    Scientists are testing the ArgonCube technology in a prototype constructed at the University of Bern in Switzerland.

    James Sinclair

    Current state-of-the-art liquid-argon neutrino detectors — big players like MicroBooNE, ICARUS and ProtoDUNE — use wires to capture the electrons knocked loose by neutrino interactions. Vast planes of thousands of wires crisscross the detectors, each set collecting coordinates that are combined by algorithms into 3-D reconstructions of a neutrino’s interaction.

    These setups are effective, well-understood and a great choice for big projects — and you don’t get much bigger than the international Deep Underground Neutrino Experiment hosted by Fermilab.

    DUNE will examine how the three known types of neutrinos change as they travel long distances, further exploring a phenomenon called neutrino oscillations. Scientists will send trillions of neutrinos from Fermilab every second on a 1,300-kilometer journey through the earth — no tunnel needed — to South Dakota. DUNE will use wire chambers in some of the four enormous far detector modules, each one holding more than 17,000 tons of liquid argon.

    But scientists also need to measure the beam of neutrinos as it leaves Fermilab, where the DUNE near detector will be close to the neutrino source and see more interactions.

    “We expect the beam to be so intense that you will have a dozen neutrino interactions per beam pulse, and these will all overlap within your detector,” says Dan Dwyer, a scientist at Lawrence Berkeley National Laboratory who works on ArgonCube. Trying to disentangle a huge number of events using the 2-D wire imaging is a challenge. “The near detector will be a new range of complexity.”

    And new complexity, in this case, means developing a new kind of liquid-argon detector.

    A blackboard drawing of an ArgonCube module

    This rough diagram of an ArgonCube detector module was drawn by Knut Skarpaas. 

    James Sinclair

    Pixel me this

    People had thought about making a pixelated detector before, but it never got off the ground. 

    "This was a dream," says Antonio Ereditato, father of the ArgonCube collaboration and a scientist at the University of Bern in Switzerland. "We developed this original idea in Bern, and it was clear that it could fly only with the proper electronics. Without it, this would have been just wishful thinking. Our colleagues from Berkeley had just what was required."

    Pixels are small, and neutrino detectors aren’t. You can fit roughly 100,000 pixels per square meter. Each one is a unique channel that — once it is outfitted with electronics — can provide information about what’s happening in the detector. To be sensitive enough, the tiny electronics need to sit right next to the pixels inside the liquid argon. But that poses a challenge.

    “If they used even the power from your standard electronics, your detector would just boil,” Dwyer says. And a liquid-argon detector only works when the argon remains … well, liquid.

    Dan Dwyer points at electronics on a computer screen

    Dan Dwyer points out features of the pixelated electronics. 

    Roman Berner

    So Dwyer and ASIC engineer Carl Grace at Berkeley Lab proposed a new approach: What if they left each pixel dormant?

    “When the signal arrives at the pixel, it wakes up and says, ‘Hey, there’s a signal here,’” Dwyer explains. “Then it records the signal, sends it out and goes back to sleep. We were able to drastically reduce the amount of power.”

    At less than 100 microwatts per pixel, this solution seemed like a promising design that wouldn’t turn the detector into a tower of gas. They pulled together a custom prototype circuit and started testing. The new electronics design worked.

    The first test was a mere 128 pixels, but things scaled quickly. The team started working on the pixel challenge in December 2016. By January 2018 they had traveled with their chips to Switzerland, installed them in the liquid-argon test detector built by the Bern scientists and collected their first 3-D images of cosmic rays.

    “It was shock and joy,” Dwyer says.

    For the upcoming installation at Fermilab, collaborators will need even more electronics. The next step is to work with manufacturers in industry to commercially fabricate the chips and readout boards that will sustain around half a million pixels. And Dwyer has received a Department of Energy Early Career Award to continue his research on the pixel electronics, complementing the Swiss SNSF grant for the Bern group.

    “We’re trying to do this on a very aggressive schedule — it’s another mad dash,” Dwyer says. “We’ve put together a really great team on ArgonCube and done a great job of showing we can make this technology work for the DUNE near detector. And that’s important for the physics, at the end of the day.”

    Samuel Kohn, Gael Flores, and Dan Dwyer work on ArgonCube technology at Lawrence Berkeley National Laboratory.

    Samuel Kohn, Gael Flores, and Dan Dwyer work on ArgonCube technology at Lawrence Berkeley National Laboratory.

    Marilyn Chung, LBNL

    More innovations ahead

    While the pixel-centered electronics of ArgonCube stand out, they aren’t the only technological innovations that scientists are planning to implement for the upcoming near detector of DUNE. There’s research and development on a new kind of light detection system and new technology to shape the electric field that draws the signal to the electronics. And, of course, there are the modules.

    Most liquid-argon detectors use a large container filled with the argon and not too much else. The signals drift long distances through the fluid to the long wires strung across one side of the detector. But ArgonCube is going for something much more modular, breaking the detector up into smaller units still contained within the surrounding cryostat. This has certain perks: The signal doesn’t have to travel as far, the argon doesn’t have to be as pure for the signal to reach its destination, and scientists could potentially retrieve and repair individual modules if required.

    “It’s a little more complicated than the typical, wire-based detector,” says Min Jeong Kim, who leads the team at Fermilab working on the cryogenics and will be involved with the mechanical integration of the ArgonCube prototype test stand. “We have to figure out how these modules will interface with the cryogenic system.”

    That means figuring out everything from filling the detector with liquid argon and maintaining the right pressure during operation to properly filtering impurities from the argon and circulating the fluid around (and through) the modules to maintain an even temperature distribution.

    Researchers assemble components in the test detector at the University of Bern.

    Researchers assemble components in the test detector at the University of Bern.

    James Sinclair

    The ArgonCube prototype under assembly at the University of Bern will run until the end of the year before being shipped to Fermilab and installed 100 meters underground, making it the first large prototype for DUNE sent to Fermilab and tested with neutrinos. After working out its kinks, researchers can finalize the design and build the full ArgonCube detector. 

    Additional instrumentation and components such as a gas-argon chamber and a beam spectrometer will round out the near detector.

    It’s an exciting time for the 100-some physicists from 23 institutions working on ArgonCube — and for the more than 1,000 neutrino physicists from over 30 countries working on DUNE. What started as wishful thinking has become a reality — and no one knows how far the pixel technology might go. 

    Ereditato even dreams of replacing the design of one of the four massive DUNE far detector modules with a pixelated version. But one thing at a time, he says.

    “Right now we’re concentrating on building the best possible near detector for DUNE,” Ereditato says. “It’s been a long path, with many people involved, but the liquid-argon technology is still young. ArgonCube technology is the proof that the technique has the potential to perform even better in the future.”

    Editor's note: This article is adapted from an article published by Fermilab.

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  • n_TOF facility explores neutron imaging

    ParticleNews at 2019-07-29T12:27:58Z

    "n_TOF facility explores neutron imaging"

    n_TOF facility explores neutron imaging

    abelchio Mon, 07/29/2019 - 12:56
    n_TOF EAR2
    n_TOF Neutron Time of Flight at the PS at CERN (Image: CERN)

    X-ray imaging is a widely used technique to image the interior of materials – anyone who has had their teeth or another part of their body X-rayed will be familiar with the images it produces. Less used is neutron imaging, which is better than X-ray imaging in some cases, for example imaging the interior of dense metals. The reason is that neutron beams that are intense enough for imaging are not easy to produce and are available at only a few facilities worldwide.

    The n_TOF facility at CERN has two intense neutron beams and normally uses them to study interactions between neutrons and atomic nuclei. However, the facility has recently started to explore the feasibility of also using one of its beams for imaging. And the first results from this exploration look good: imaging of particle-producing targets that have been used or are designed to be used at the neighbouring Antiproton Decelerator (AD) to produce antiprotons (the antiparticles of protons) has shown that the beam can reveal the samples’ internal structure.

    Neutron imaging is based on recording the attenuation of a neutron beam as it passes through a sample. The quality of the resulting image depends on several factors, including the energy of the neutrons at the sample’s position and the distance between the sample and the collimator that focuses the beam. Using a commercially available neutron-imaging camera, the n_TOF researchers set up a neutron-imaging station at n_TOF and analysed some of these factors. They then set out to test the imaging station with five antiproton-producing targets: two targets from the AD, which produces antiprotons by taking an intense proton beam from the Proton Synchrotron accelerator and firing it into a target made of dense metal; and three potential new targets for the AD that had previously been tested at the HiRadMat facility.

    One of the two AD targets was a spare, never used, whereas the other AD target and the three HiRadMat targets had been subjected to intense proton beams that could have damaged them. The n_TOF imaging of the targets showed their internal structure with good contrast and, in the case of the targets that had been exposed to proton beams, revealed deformation, bending or cracking of their interior. For two of the targets, the damage observed was confirmed by opening the target, and for one of these targets the damage was also confirmed by imaging at a neutron-imaging station at the Paul Scherrer Institute.,Experiments and Tracks
    Neutron image of one of the AD targets studied, showing damage to the target’s core (uneven boundaries of the thin black strip). Neither the damage nor the core itself can be seen with X-ray imaging (Image: n_TOF collaboration)

    The results served two purposes: they demonstrated the feasibility of using n_TOF’s neutron beam for imaging and they offered two-dimensional images of the inside of the antiproton-producing targets that would otherwise have been more difficult to obtain. Conventional imaging techniques such as X-ray imaging cannot penetrate the dense metals from which the targets are made to reveal their internal state and, if they were to be imaged with specialised imaging facilities outside of CERN, the targets would need to be transported and subjected to inspection before being handled.

    The next steps towards developing a full-fledged imaging station at n_TOF include improving the collimation system, which would lead to higher-resolution images, and adding equipment that would allow three-dimensional rather than two-dimensional images to be obtained.

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  • JanKusanagi at 2019-07-22T23:02:24Z

    🏃 🌪 !!!!!!!!!!!!!!!!!!!!!!!

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  • LHC experiments present new Higgs results at 2019 EPS-HEP conference

    ParticleNews at 2019-07-15T16:28:23Z

    "LHC experiments present new Higgs results at 2019 EPS-HEP conference"

    LHC experiments present new Higgs results at 2019 EPS-HEP conference achintya Mon, 07/15/2019 - 15:18

    Combined image showing Higgs candidates from ATLAS (left) and CMS (right)
    (Image: CERN)

    Geneva and Ghent. At the 2019 European Physical Society’s High-Energy Physics conference (EPS-HEP) taking place in Ghent, Belgium, the ATLAS and CMS collaborations presented a suite of new results. These include several analyses using the full dataset from the second run of CERN’s Large Hadron Collider (LHC), recorded at a collision energy of 13 TeV between 2015 and 2018. Among the highlights are the latest precision measurements involving the Higgs boson. In only seven years since its discovery, scientists have carefully studied several of the properties of this unique particle, which is increasingly becoming a powerful tool in the search for new physics.

    The results include new searches for transformations (or “decays”) of the Higgs boson into pairs of muons and into pairs of charm quarks. Both ATLAS and CMS also measured previously unexplored properties of decays of the Higgs boson that involve electroweak bosons (the W, the Z and the photon) and compared these with the predictions of the Standard Model (SM) of particle physics. ATLAS and CMS will continue these studies over the course of the LHC’s Run 3 (2021 to 2023) and in the era of the High-Luminosity LHC (from 2026 onwards).

    The Higgs boson is the quantum manifestation of the all-pervading Higgs field, which gives mass to elementary particles it interacts with, via the Brout-Englert-Higgs mechanism. Scientists look for such interactions between the Higgs boson and elementary particles, either by studying specific decays of the Higgs boson or by searching for instances where the Higgs boson is produced along with other particles. The Higgs boson decays almost instantly after being produced in the LHC and it is by looking through its decay products that scientists can probe its behaviour.

    In the LHC’s Run 1 (2010 to 2012), decays of the Higgs boson involving pairs of electroweak bosons were observed. Now, the complete Run 2 dataset – around 140 inverse femtobarns each, the equivalent of over 10 000 trillion collisions – provides a much larger sample of Higgs bosons to study, allowing measurements of the particle’s properties to be made with unprecedented precision. ATLAS and CMS have measured the so-called “differential cross-sections” of the bosonic decay processes, which look at not just the production rate of Higgs bosons but also the distribution and orientation of the decay products relative to the colliding proton beams. These measurements provide insight into the underlying mechanism that produces the Higgs bosons. Both collaborations determined that the observed rates and distributions are compatible with those predicted by the Standard Model, at the current rate of statistical uncertainty.

    Higgs Candidates,Proton Collisions,Event Displays,Physics,ATLAS
    An event recorded by ATLAS showing a candidate for a Higgs boson produced in association with two top quarks. The Higgs boson decays to four muons (red tracks). There is an additional electron (green track) and four particle jets (yellow cones) (Image: ATLAS/CERN)

    Since the strength of the Higgs boson’s interaction is proportional to the mass of elementary particles, it interacts most strongly with the heaviest generation of fermions, the third. Previously, ATLAS and CMS had each observed these interactions. However, interactions with the lighter second-generation fermions – muons, charm quarks and strange quarks – are considerably rarer. At EPS-HEP, both collaborations reported on their searches for the elusive second-generation interactions.

    ATLAS presented their first result from searches for Higgs bosons decaying to pairs of muons (H→μμ) with the full Run 2 dataset. This search is complicated by the large background of more typical SM processes that produce pairs of muons. “This result shows that we are now close to the sensitivity required to test the Standard Model’s predictions for this very rare decay of the Higgs boson,” says Karl Jakobs, the ATLAS spokesperson. “However, a definitive statement on the second generation will require the larger datasets that will be provided by the LHC in Run 3 and by the High-Luminosity LHC.”

    CMS presented their first result on searches for decays of Higgs bosons to pairs of charm quarks (H→cc). When a Higgs boson decays into quarks, these elementary particles immediately produce jets of particles. “Identifying jets formed by charm quarks and isolating them from other types of jets is a huge challenge,” says Roberto Carlin, spokesperson for CMS. “We’re very happy to have shown that we can tackle this difficult decay channel. We have developed novel machine-learning techniques to help with this task.”

    Real Events,For Press
    An event recorded by CMS showing a candidate for a Higgs boson produced in association with two top quarks. The Higgs boson and top quarks decay leading to a final state with seven jets (orange cones), an electron (green line), a muon (red line) and missing transverse energy (pink line) (Image: CMS/CERN)

    The Higgs boson also acts as a mediator of physics processes in which electroweak bosons scatter or bounce off each other. Studies of these processes with very high statistics serve as powerful tests of the Standard Model. ATLAS presented the first-ever measurement of the scattering of two Z bosons. Observing this scattering completes the picture for the W and Z bosons as ATLAS has previously observed the WZ scattering process and both collaborations the WW processes. CMS presented the first observation of electroweak-boson scattering that results in the production of a Z boson and a photon.

    “The experiments are making big strides in the monumental task of understanding the Higgs boson,” says Eckhard Elsen, CERN’s Director of Research and Computing. “After observation of its coupling to the third-generation fermions, the experiments have now shown that they have the tools at hand to address the even more challenging second generation. The LHC’s precision physics programme is in full swing.”

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  • at 2019-07-15T23:00:06Z

    Congratulations to Dr. Dan Jardin for the successful defense of his PhD thesis! #SuperCDMS

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  • Alexandre Oliva at 2019-07-03T17:51:30Z

    hacker!  tinkerer!
    awesome! :-)

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  • Astronomy Picture of the Day for 2019-07-02 12:30:02.403922

    Astronomy Picture of the Day (Unofficial) at 2019-07-02T17:30:03Z

    Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

    2019 July 2
    See Explanation.  Clicking on the picture will download
 the highest resolution version available.

    NGC 1566: The Spanish Dancer Spiral Galaxy
    Image Credit: NASA, ESA, Hubble; Processing & Copyright: Leo Shatz

    Explanation: If not perfect, then this spiral galaxy is at least one of the most photogenic. An island universe containing billions of stars and situated about 40 million light-years away toward the constellation of the Dolphinfish (Dorado), NGC 1566 presents a gorgeous face-on view. Classified as a grand design spiral, NGC 1566's shows two prominent and graceful spiral arms that are traced by bright blue star clusters and dark cosmic dust lanes. Numerous Hubble Space Telescope images of NGC 1566 have been taken to study star formation, supernovas, and the spiral's unusually active center. Some of these images, stored online in the Hubble Legacy Archive, were freely downloaded, combined, and digitally processed by an industrious amateur to create the featured image. NGC 1566's flaring center makes the spiral one of the closest and brightest Seyfert galaxies, likely housing a central supermassive black hole wreaking havoc on surrounding stars and gas.

    Today: Total solar eclipse visible in parts of South America
    Tomorrow's picture: titanian moon copter

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    Sort of like: 💃

    JanKusanagi at 2019-07-02T22:35:35Z

  • JanKusanagi at 2019-06-22T14:27:00Z

    You're off to a good start 😁

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  • The proton, a century on

    ParticleNews at 2019-06-13T13:28:14Z

    "The proton, a century on"

    The proton, a century on abelchio Thu, 06/13/2019 - 10:11

    It is 100 years since Ernest Rutherford published his results proving the existence of the proton. For decades, the proton was considered an elementary particle. But ever since researchers at the SLAC and DESY laboratories began firing electrons into protons, beginning in the 1960s, experiments have revealed that the proton has a complex internal structure, one that depends on how you look at it, or rather on how hard you hit it. A century on, however, much remains to be learnt about the proton. Check out the latest edition of the CERN Courier and read in-depth articles about what we know and don’t know about the proton.

    In “Rutherford, transmutation and the proton”, you’ll find an account of the historical events leading to Ernest Rutherford’s discovery of the proton, published in 1919. In “The proton laid bare”, you can read about scientists’ evolving knowledge of the proton, how a deeper understanding may be key to the search for new physics phenomena, and what remains to be learnt – including the origin of the proton’s spin, whether or not the proton decays on long timescales, and the puzzling, although soon-to-be resolved, value of its radius.

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  • Lock the Planck: the kilogram has a new definition

    ParticleNews at 2019-05-20T12:27:55Z

    "Lock the Planck: the kilogram has a new definition"

    Lock the Planck: the kilogram has a new definition

    achintya Mon, 05/20/2019 - 14:01
    METAS Kibble balance (BWM II)
    The Kibble balance (a.k.a. watt balance) built by the Swiss Federal Institute of Metrology (METAS) to measure the Planck constant with ultra-high precision (Image: CERN)

    Until today, a kilogram was defined as the mass of the International Prototype Kilogram (IPK), a platinum–iridium cylinder located in Paris, France. While all the other base units of the International System of Units (SI) had been redefined over the years based on fundamental constants of nature or atomic properties, the kilogram had remained since the late 19th century the only one to rely on a human-made artefact.

    This changes today, and metrologists – those who study measurement – are excited. On the occasion of World Metrology Day, which commemorates the signing of the Metre Convention back in 1875, the kilogram has been given a new definition. From now on, it will be defined based on the most precise measurement ever made of the Planck constant, which can be expressed in terms of the SI units kilogram, metre and second. Since the latter two units are already defined by constants of nature, the value of a kilogram can be obtained without relying on comparing it with a physical reference block.

    But measuring the Planck constant to a suitably high precision of ten parts per billion required decades of work by international teams across continents, and CERN played a small part in the endeavour.

    In 1975, British physicist Bryan Kibble proposed a device, then known as a watt balance and now called the Kibble balance in his honour, which would allow the Planck constant to be measured precisely based on the IPK. Once the precision was achieved, the Planck constant’s value could be fixed and the definitions inverted, removing the kilogram’s dependence on the IPK. Several Kibble balances around the world were constructed to compare measurements, including one in Switzerland. METAS, the Swiss Federal Institute of Metrology, has been working on their Kibble balance project for almost two decades, the activity being led by Ali Eichenberger and Henri Baumann. Knowing CERN’s expertise in magnet systems, Eichenberger and Baumann reached out to the Laboratory to help prepare the required magnets.

    “I am extremely proud to have participated in this adventure,” says Davide Tommasini from CERN’s Magnets, Superconductors and Cryostats group, who was directly involved in the project. “I do not know if the redefinition of the kilogram has a direct impact on the experiments at CERN, but the past teaches us that there are many new advancements which, at their initial moment, may not appear in their whole potential.”

    In 2018, the Kibble balance in Canada measured the Planck constant with necessary ultrahigh precision, allowing a combination of measurements from around the world to help fix its value. But does it affect the value of the kilogram itself? Not really. “The Plank constant has been fixed at 6.626070150 × 10−34 kg⋅m2/s using the IPK as standard,” explains Eichenberger. “So from today, one kilogram will stay the same. If the IPK drifts further with time then its value will change, but any mass calibration will have an uncertainty of the order of 20 parts per billion.”

    So while it is a momentous occasion worthy of celebration, you won’t have to recalibrate your bathroom scales just yet.

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    Ah, so I still weight the same? 😌

    JanKusanagi at 2019-05-20T14:08:33Z

  • LS2 report: The Proton Synchrotron’s magnets prepare for higher energies

    ParticleNews at 2019-02-13T11:27:36Z

    "LS2 report: The Proton Synchrotron’s magnets prepare for higher energies"

    LS2 report: The Proton Synchrotron’s magnets prepare for higher energies

    achintya Wed, 02/13/2019 - 09:35
    PS Magnets consolidation during LS2
    PS Magnets consolidation during LS2 (Image: CERN)

    The Proton Synchrotron (PS), which was CERN’s first synchrotron and which turns 60 this year, once held the record for the particle accelerator with the highest energy. Today, it forms a key link in CERN’s accelerator complex, mainly accelerating protons to 26 GeV before sending them to the Super Proton Synchrotron (SPS), but also delivering particles to several experimental areas such as the Antiproton Decelerator (AD). Over the course of Long Shutdown 2 (LS2), the PS will undergo a major overhaul to prepare it for the higher injection and beam intensities of the LHC’s Run 3 as well as for the High-Luminosity LHC.

    One major component of the PS that will be consolidated is the magnet system. The synchrotron has a total of 100 main magnets within it (plus one reference magnet unit outside the ring), which bend and focus the particle beams as they whizz around it gaining energy. “During the last long shutdown (LS1) and at the beginning of LS2, the TE-MSC team performed various tests to identify weak points in the magnets,” explains Fernando Pedrosa, who is coordinating the LS2 work on the PS. The team identified 50 magnets needing refurbishment, of which seven were repaired during LS1 itself. “The remaining 43 magnets that need attention will be refurbished this year.”

    Specifically, one of the elements, known as the pole-face windings, which is located between the beam pipe and the magnet yoke, needs replacing. In order to reach into the magnet innards to replace these elements, the magnet units have to be transferred to a workshop in building 151. Once disconnected, each magnet is placed onto a small locomotive system that drives them to the workshops. The locomotives themselves are over 50 years old, and their movement must be delicately managed. It takes ten hours to extract one magnet. So far, six magnets have been taken to the workshop and this work will last until 18 October 2019.

    The workshop where the magnets are being treated is divided into two sections. In the first room, the vacuum chamber of the magnets is cut so as to access the pole-face windings. The magnet units are then taken to the second room, where prefabricated replacements are installed.

    As mentioned in the previous LS2 Report, the PS Booster will see an increase in the energy it imparts to accelerating protons, from 1.4 GeV to 2 GeV. A new set of quadrupole magnets will be installed along the Booster-to-PS injection line, to increase the focusing strength required for the higher-energy beams. Higher-energy beams require higher-energy injection elements; therefore some elements will be replaced in the PS injection region as part of the LHC Injectors Upgrade (LIU) project, namely septum 42, kicker 45 and five bumper magnets.

    Other improvements as part of the LIU project include the new cooling systems being installed to increase the cooling capacity of the PS. A new cooling station is being built at building 355, while one cooling tower in building 255 is being upgraded. The TT2 line, which is involved in the transfer from the PS to the SPS, will have its cooling system decoupled from the Booster’s, to allow the PS to operate independent of the Booster schedule. “The internal dumps of the PS, which are used in case the beam needs to be stopped, are also being changed, as are some other intercepting devices,” explains Pedrosa.

    The LS2 operations are on a tight schedule,” notes Pedrosa, pointing out that works being performed on several interconnected systems create constraints for what can be done concurrently. As LS2 proceeds, we will bring you more news about the PS, including the installation of new instrumentation in wire scanners that help with beam-size measurement, an upgraded transverse-feedback system to stabilise the beam and more.

    More pictures of the PS magnets are available on CDS:

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  • Build The Peach!

    Jason Self at 2019-02-01T14:37:58Z

    Build the peach! Build the peach!

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