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.

  • Stephen Michael Kellat at 2020-07-06T13:18:32Z

    The responsible thing the Ohio General Assembly could do would be to shutter campuses now.  Unfortunately we are going half speed ahead on re-opening with plans to fall down to online-only if things get bad.School districts are insisting on “local control” and Ashtabula Area City Schools is horrifyingly insisting on 5 days a week back in the classroom for every child.

    There are procedures for removing elected officials in Ohio for malfeasance, misfeasance, nonfeasance, and drunkenness that don’t require recall elections.  I’m not sure I’m ready to dig into those.  Too many people think locally that coronavirus doesn’t really exist and won’t impact them so I might not get the support needed to push for removing the school board’s membership. 

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  • Covid-19: why R is a lot more complicated than you think

    PumpCast at 2020-06-30T04:13:40Z

    "Covid-19: why R is a lot more complicated than you think"

    Over the last few months, we’ve all had to come to terms with R, the ‘effective reproduction number’, as a measure of how well we are dealing with the coronavirus outbreak. But, as Nicola Davis finds out from Dr Adam Kucharski, R is a complicated statistical concept that relies on many factors and, under some conditions, can be misleading. Help support our independent journalism at

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  • Astronomy Picture of the Day for 2020-06-27 12:30:02.231108

    Astronomy Picture of the Day (Unofficial) at 2020-06-27T17:30:03Z

    Astronomy Picture of the Day

    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.

    2020 June 27
    See Explanation.  Clicking on the picture will download
the highest resolution version available.

    Eclipse under the ISS
    Image Credit: NASA ISS Expedition 63

    Explanation: The dark shadow of the New Moon reached out and touched planet Earth on June 21. A high definition camera outside the International Space Station captured its passing in this snapshot from low Earth orbit near the border of Kazakhstan and China. Of course those along the Moon's central shadow track below could watch the much anticipated annular eclipse of the Sun. In the foreground a cargo spacecraft is docked with the orbital outpost. It's the H-II Transfer Vehicle-9 from JAXA the Japan Aerospace Exploration Agency.

    Gallery: Notable images of the Annular Solar Eclipse of 2020 June submitted to APOD
    Tomorrow's picture: moons and shadows

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  • SuperKEKB collider achieves the world's highest luminosity

    ParticleNews at 2020-06-26T14:28:48Z

    "SuperKEKB collider achieves the world's highest luminosity"

    SuperKEKB collider achieves the world's highest luminosityPress Releasexeno Fri, 06/26/2020 - 08:252920

    Fig. 1 The instantaneous luminosity of SuperKEKB measured at 5-minute intervals from Fall 2019 to June 22, 2020. Values are on-line measurements and contain an approximate 1% error.

    Fig. 1 The instantaneous luminosity of SuperKEKB measured at 5-minute intervals from Fall 2019 to June 22, 2020. Values are on-line measurements and contain an approximate 1% error.

    Japan’s High Energy Accelerator Research Organization (KEK) has been steadily improving the performance of its flagship electron-positron collider, SuperKEKB, since it produced its first electron-positron collisions in April 2018. At 20:34 on 15th June 2020, SuperKEKB achieved the world’s highest instantaneous luminosity for a colliding-beam accelerator, setting a record of 2.22×1034cm-2s-1. Previously, the KEKB collider, which was SuperKEKB’s predecessor and was operated by KEK from 1999 to 2010, had achieved the world’s highest luminosity, reaching 2.11×1034cm-2s-1. KEKB’s record was surpassed in 2018, when the LHC proton-proton collider at the European Organization for Nuclear Research (CERN) overtook the KEKB luminosity at 2.14×1034cm-2s-1. SuperKEKB’s recent achievement returns the title of world’s highest luminosity colliding-beam accelerator to KEK.(*)

    (*)The current record is 2.40×1034cm-2s-1, obtained at 00:53 JST on June 21st.

    In the coming years, the luminosity of SuperKEKB will be increased to approximately 40 times the new record. This exceptionally high luminosity is to be achieved mainly by using a beam collision method called the “nano-beam scheme”, developed by Italian physicist Pantaleo Raimondi. Raimondi’s innovation enables significant increases in luminosity by using powerful magnets to squeeze the two beams in both the horizontal and vertical directions. Substantially decreasing the beam sizes increases the luminosity, which varies inversely with the cross-sectional area of the colliding beams.

    SuperKEKB is the first collider in the world to realize the nano-beam scheme. In the beam operation of SuperKEKB, we keep increasing the luminosity by squeezing the beams ever harder, while solving various problems associated with the squeezing. Currently, the vertical height of the beams at the collision point is about 220 nanometers, and this will decrease to approximately 50 nanometers (about 1/1000 the width of a human hair) in the future.

    Another factor that determines luminosity is the product of the two beam currents, which is proportional to the product of the numbers of electrons and positrons stored in the collider. KEK physicists and accelerator operators continue to increase the beam currents, while mitigating various high-current problems, such as stray background particles that introduce noise in the Belle II detector. SuperKEKB achieved the new luminosity record with a product of beam currents that was less than 25% that of KEKB. This demonstrates the superiority of the SuperKEKB design. In the future, we aim to increase the beam current product to about four times the value achieved by KEKB.

    In order to adopt the nano-beam scheme and increase the beam current, KEKB underwent significant upgrades that turned it into SuperKEKB. These included a new beam pipe, new superconducting final-focusing magnets, a positron damping ring, and an advanced injector. The most recent improvement was completed in April 2020, with the introduction of the “crab waist”, first used at the DAΦNE accelerator in Frascati, Italy, in 2010, and which reduces the beam size and stabilizes collisions.

    The success of SuperKEKB relies also on contributions from overseas. As an example, the superconducting final-focusing magnets were built in cooperation with Brookhaven National Laboratory and Fermi National Accelerator Laboratory in the U.S. under the U.S.-Japan Science and Technology Cooperation Program. Other major contributions under this program were the development of a collision-point orbit feedback system (SLAC National Accelerator Laboratory) and an X-ray beam size monitor (University of Hawaii and SLAC National Accelerator Laboratory). Researchers from CERN (Switzerland), IJCLab (France), IHEP (China)as well as SLAC(U.S.) have participated in accelerator research and operation under KEK’s Multinational Partnership Project (MNPP-01).There are also contributions from many other foreign research institutes. Other important contributions have come through the Belle II experiment collaboration, such as the diamond-based radiation monitor and beam abort system (INFN and University of Trieste, Italy), and the luminosity monitoring system developed at BINP (Russia).

    SuperKEKB brings its electron and positron beams into collision at the center of the Belle II particle detector. The detector has been built and is operated by the Belle II collaboration, an international group of approximately 1,000 physicists and engineers from 119 universities and laboratories located in 26 countries and regions around the world. Belle II physicists use the detector to explore fundamental physics phenomena, by studying the production and decay processes of particles produced in the collisions, primarily B mesons, D mesons, and tau leptons. To within the precision of current measurements, the behavior of particles such as these is well described by the theory known as the Standard Model. However, the Standard Model fails to address key questions, such as the mystery of the matter-dominated universe and the existence of dark matter. Therefore, new physical laws are needed to explain these observations. Signals of such “new physics” may arise in decay processes that are very rarely observed. Maximizing the discovery potential of Belle II for such signals requires a large number of electron-positron collisions, necessitating a very high-luminosity collider, such as SuperKEKB.

    Collecting data for about 10 years, the Belle II experiment will accumulate 50 times more particle collisions than its predecessor, the Belle experiment. The large data set, containing about 50 billion B-meson pairs and similar numbers of charm mesons and tau leptons, will enable Belle II physicists to explore nature at a much deeper level than was previously possible. The data will also be used in sensitive searches for very weakly interacting particles that may help answer some of the outstanding mysteries of the universe.


    Collaborators rejoicing over the world record (Image Credit: KEK)

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    High Energy Accelerator Research Organization (KEK)

    Render of International Linear Collider - Next-generation particle accelerator (Courtesy: Rey.Hori/KEK)

    KEK was established in 1997 in a reorganization of the Institute of Nuclear Study, University of Tokyo (established in 1955), the National Laboratory for High Energy Physics (established in 1971), and the Meson Science Laboratory of the University of Tokyo (established in 1988).

    Scientists at KEK use accelerators and perform research in high-energy physics to answer the most basic questions about the universe as a whole, and the matter and the life it contains.


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  • Astronomy Picture of the Day for 2020-06-26 12:30:02.216158

    Astronomy Picture of the Day (Unofficial) at 2020-06-26T17:30:02Z

    Astronomy Picture of the Day

    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.

    2020 June 26
    See Explanation.  Clicking on the picture will download
the highest resolution version available.

    Eclipse under the Bamboo
    Image Credit & Copyright: Somak Raychaudhury (Inter-University Centre for Astronomy & Astrophysics)

    Explanation: Want to watch a solar eclipse safely? Try looking down instead of up, though you might discover you have a plethora of images to choose from. For example, during the June 21st solar eclipse this confusing display appeared under a shady bamboo grove in Pune, India. Small gaps between close knit leaves on the tall plants effectively created a network of randomly placed pinholes. Each one projected a separate image of the eclipsed Sun. The snapshot was taken close to the time of maximum eclipse in Pune when the Moon covered about 60 percent of the Sun's diameter. But an annular eclipse, the Moon in silhouette completely surrounded by a bright solar disk at maximum, could be seen along a narrow path where the Moon's dark shadow crossed central Africa, south Asia, and China.

    Gallery: Notable images of the Annular Solar Eclipse of 2020 June submitted to APOD
    Tomorrow's picture: pixels in space

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    Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
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  • DUNE moves to the next stage with a blast

    ParticleNews at 2020-06-24T21:29:00Z

    "DUNE moves to the next stage with a blast"

    Construction workers have carried out the first underground blasting for the Long-Baseline Neutrino Facility, which will provide the space, infrastructure and particle beam for the international Deep Underground Neutrino Experiment. 

    Two construction workers in a tunnel below ground

    It started with a blast.

    On June 23, construction company Kiewit Alberici Joint Venture set off explosives 3,650 feet beneath the surface in Lead, South Dakota, to begin creating space for the international Deep Underground Neutrino Experiment, hosted by the Department of Energy’s Fermilab.

    The blast is the start of underground excavation activity for the experiment, known as DUNE, and the infrastructure that powers and houses it, called the Long-Baseline Neutrino Facility, or LBNF.

    Situated a mile deep in South Dakota rock at the Sanford Underground Research Facility, DUNE’s giant particle detector will track the behavior of fleeting particles called neutrinos. The plan for the next three years, is that workers will blast and drill to remove 800,000 tons of rock to make a home for the gigantic detector and its support systems.

    “The start of underground blasting for these early excavation activities marks not only the initiation of the next major phase of this work, but significant progress on the construction already under way to prepare the site for the experiment,” says Fermilab Deputy Director for LBNF/DUNE-US Chris Mossey.

    The excavation work begins with removing 3,000 tons of rock 3,650 feet below ground. This initial step carves out a station for a massive drill whose bore is as wide as a car is long, about four meters.

    The machine will help create a 1,200-foot ventilation shaft down to what will be the much larger cavern for the DUNE particle detector and associated infrastructure. There, 4,850 feet below the surface—about 1.5 kilometers deep—the LBNF project will remove hundreds of thousands of tons of rock, roughly the weight of eight aircraft carriers.

    The emptied space will eventually be filled with DUNE’s enormous and sophisticated detector, a neutrino hunter looking for interactions from one of the universe’s most elusive particles. Researchers will send an intense beam of neutrinos from Fermilab in Illinois to the underground detector in South Dakota—straight through the earth, no tunnel necessary—and measure how the particles change their identities. What they learn may answer one of the biggest questions in physics: Why does matter exist instead of nothing at all?

    “The worldwide particle physics community is preparing in various ways for the day DUNE comes online, and this week, we take the material step of excavating rock to support the detector,” says DUNE co-spokesperson Stefan Söldner-Rembold of the University of Manchester. “It’s a wonderful example of collaboration: While excavation takes place in South Dakota, DUNE partners around the globe are designing and building the parts for the DUNE detector.”

    A number of science experiments already take data at Sanford Underground Research Facility, but no activity takes place at the 3650 level. With nothing and no one in the vicinity, the initial excavation stage to create the cavern for the drill proceeds in an isolated environment. It’s also an opportunity for the LBNF construction project to gather information about matters such as air flow and the rock’s particular response to the drill-and-blast technique before moving on to the larger excavation at the 4850 level, where the experiment will be built.

    “It was important for us to develop a plan that would allow the LBNF excavation to go forward without disrupting the experiments already going on in other parts of the 4850 level,” says Fermilab Long-Baseline Neutrino Facility Far-Site Conventional Facilities Manager Joshua Willhite. Following a period of excavation at the 3650 level, the project will initiate excavation at the 4850 level.

    Every bit of the 800,000 tons of rock dislodged by the underground drill-and-blast operation must eventually be transported a mile back up to the surface. There, a conveyor is being built to transport the crushed rock over a stretch of 4,200 feet for final deposit in the Open Cut, an enormous open pit mining area excavated in the 1980s. As large as the LBNF excavation will be, the rock moved to the surface and deposited in the Open Cut will only fill less than one percent of it.

    Excavation at the 3650 level will be completed over the next few months, with blasting at the 4850 level planned to begin immediately after.

    Editor's note: A version of this article was originally published by Fermilab.

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  • Astronomy Picture of the Day for 2020-06-20 12:30:02.209075

    Astronomy Picture of the Day (Unofficial) at 2020-06-20T17:30:02Z

    Astronomy Picture of the Day

    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.

    2020 June 20
    See Explanation.  Clicking on the picture will download
the highest resolution version available.

    Northern Summer on Titan
    Image Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA

    Explanation: Today's solstice brings summer to planet Earth's northern hemisphere. But the northern summer solstice arrived for ringed planet Saturn over three years ago on May 24, 2017. Orbiting the gas giant, Saturn's moon Titan experiences the Saturnian seasons that are about 7 Earth-years long. Larger than inner planet Mercury, Titan was captured in this Cassini spacecraft image about two weeks after its northern summer began. The near-infrared view finds bright methane clouds drifting through Titan's dense, hazy atmosphere as seen from a distance of about 507,000 kilometers. Below the clouds, dark hydrocarbon lakes sprawl near its fully illuminated north pole.

    Tomorrow's picture: Venus by moonlight

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  • Astronomy Picture of the Day for 2020-06-17 12:30:01.518292

    Astronomy Picture of the Day (Unofficial) at 2020-06-17T17:30:02Z

    Astronomy Picture of the Day

    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.

    2020 June 17
    See Explanation.  Clicking on the picture will download
the highest resolution version available.

    Magnetic Streamlines of the Milky Way
    Image Credit: ESA, Planck; Text: Joan Schmelz (USRA)

    Explanation: What role do magnetic fields play in interstellar physics? Analyses of observations by ESA's Planck satellite of emission by small magnetically-aligned dust grains reveal previously unknown magnetic field structures in our Milky Way Galaxy -- as shown by the curvy lines in the featured full-sky image. The dark red shows the plane of the Milky Way, where the concentration of dust is the highest. The huge arches above the plane are likely remnants of past explosive events from our Galaxy's core, conceptually similar to magnetic loop-like structures seen in our Sun's atmosphere. The curvy streamlines align with interstellar filaments of neutral hydrogen gas and provide tantalizing evidence that magnetic fields may supplement gravity in not only in shaping the interstellar medium, but in forming stars. How magnetism affected our Galaxy's evolution will likely remain a topic of research for years to come.

    Tomorrow's picture: open space

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    Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
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  • The stories a muon could tell

    ParticleNews at 2020-06-16T20:28:06Z

    "The stories a muon could tell"

    The discovery of the muon originally confounded physicists. Today international experiments are using the previously perplexing particle to gain a new understanding of our world.

    Illustration of the earth taking a shower

    At the beginning of the 20th century, physicists were aware of a pervasive shower of particles that seemed to rain down from space. By filling glass chambers with highly condensed vapor, they could indirectly see tracks left by these highly energetic particles now known as cosmic rays. In doing so, they quickly discovered the subatomic world was more complex than initially suspected. 

    The first new matter particle they discovered was the muon. It was a lot like an electron, just more massive. At first, no one knew what to make of it. 

    Some thought it might be a particle theorized to hold protons and neutrons together in an atom. But a pair of Italians conducting experiments in Rome during World War II proved otherwise. 

    After discarding a few alternative theories—including one that posited that this particle might be a new kind of electron—physicists were left with one conclusion: They had discovered a particle that nobody had predicted. As Nobel Laureate I.I. Rabi famously quipped, “Who ordered that?”

    Although scientists hadn’t realized muons would be on the menu, the discovery of muons eventually led to a discovery about how that menu was set up: Particles can come in different versions, each alike in charge, spin and interactions but different in mass. The muon, for example, has the same charge, spin and electroweak interactions as the electron, but is about 200 times heavier, and there’s an even heavier version of the electron and muon, called the tau.  

    Physicists built on this principle to predict the existence of generations of other particles, such as neutrinos, which with electrons, muons and taus round out the set of particles called leptons. Eventually, scientists would find that all of the matter particles in the Standard Model, including quarks, could be organized into three generations, though only the lightest are stable. 

    Muons continue to be useful tools for discovery to this day. Two international experiments, one currently underway and the other slated to begin in the early 2020s, are using the previously perplexing particles to push the boundaries of physics.

    Flavor physics and the Mu2e experiment

    Each of the three generations is called a different “flavor” of particle. 

    At first, scientists assumed that flavor was a property that, like mass or energy, had to be conserved when particles interacted with each other. That wasn’t quite right, but in their defense, they did find this to be true almost all of the time.

    “When you have some kind of an interaction that involves charged leptons, such as nuclear or particle decay or some type of high-energy particle interaction, the number of a given flavor of charged leptons remains the same,” says Jim Miller, a professor of physics at Boston University. 

    When muons decay, for example, they transform into an electron, an anti-electron neutrino, and a muon neutrino. The electron and anti-electron neutrino cancel each other out, flavor-wise, leaving just the muon neutrino, which has the same flavor as the original muon.

    Flavor conservation was useful; it allowed physicists to predict the interactions they would observe in particle accelerators and nuclear reactions. And those predictions proved to be correct. 

    But then physicists discovered that the group of (uncharged lepton) particles called neutrinos are unaware they are expected to follow the rules. On their long journey to Earth from the center of the sun, where they are created in fusion reactions, neutrinos freely oscillate between generations, transforming from electron neutrinos to muon neutrinos to tau neutrinos and back without releasing any additional particles.

    This phenomenon, which won researchers Takaaki Kajita and Arthur B. McDonald the Nobel Prize for Physics in 2015, left scientists with a question: If neutrinos could violate flavor conservation, could other particles do it, too?

    Physicists hope to answer that exact question with Mu2e, an experiment scheduled to start generating data in the next few years at the US Department of Energy’s Fermi National Accelerator Laboratory. The experiment is supported by funding from DOE’s Office of Science. 

    Mu2e will search for muons converting into electrons without releasing other particles, a process that would clearly violate flavor conservation. 

    But why use muons? It’s because they’re the just-right middle of the lepton family. Not too big or too small, muons are a sort of Goldilocks particle that are perfectly suited to aid physicists in their search for new physics.

    Electrons, the least massive charged leptons, are small and stable. Taus, the most massive ones, are so massive and short-lived that they decay far too quickly for physicists to effectively study. Muons, however, are massive enough to decay but not massive enough to decay too quickly, making them the perfect tool in the search for new physics.

    In the Mu2e experiment, physicists will accelerate a beam of low-energy muons toward a target made of aluminum. In the resulting collisions, muons will knock electrons out of their orbits around the aluminum nuclei and take their place, creating muonic atoms for a brief moment in time.

    “Since the mass of the muon is 200 times greater than the mass of the electron, and its average distance from the nucleus is 200 times smaller, there’s an overlap between the muon’s position and the position of the aluminum nucleus, allowing them to interact,” Miller says.

    As the muon decays into an electron, physicists predict that the extra energy that usually goes into creating two neutrinos in a typical muon decay will instead be transferred to the atom’s nucleus. This would allow the conversion from one flavor to another, muon to electron, without any neutrinos or antineutrinos to provide balance. If observed, this direct transition of a muon into an electron would be the hoped-for discovery of flavor violation among charged leptons.

    Magnetic moment of fame

    Mu2e is not the only experiment that will use muons to test our understanding of physics.

    Eight years before the discovery of muons, physicist Paul Dirac was developing a theory to describe the motion of electrons. In a single, elegant equation, Dirac successfully described that motion—while simultaneously merging Albert Einstein’s special theory of relativity with quantum mechanics and predicting the existence of antimatter. 

    It’s hard to overstate how important and incredibly accurate Dirac’s equation turned out to be. Physicists still act giddy whenever it’s mentioned. 

    To understand why it’s important, take a look at the electron.

    Dirac’s equation correctly described exactly how the electromagnetic force worked and gave the correct estimate for how an electron’s spin would shift—or “precess”—if placed in a magnetic field, a measurement known as g. (That prediction was later refined through calculations from the field of quantum electrodynamics.)

    When muons were discovered in 1936, Dirac’s equation was used to calculate what their precession rate would be as well. The value g for muons was predicted to be equal to 2. 

    But when physicists began generating muons in accelerators at CERN in the 1950s to test his predictions, the results were not quite what they expected. Had they found a discrepancy between observation and theory? Although physicists worked hard for the next 20 years, they couldn’t generate enough energy with their accelerators to obtain a conclusive answer.

    Scientists at Brookhaven National Laboratory were able to test Dirac’s prediction at higher energies between 1999 and 2001 with an experiment meant to directly determine the anomalous part of the magnetic moment called Muon g-2 (pronounced “Muon g minus 2”). They found hints of the same anomalous measurement, but even with their improved technology, they lacked sufficient precision to prove a disagreement with theory.

    Could Dirac’s equation turn out to be wrong? Physicists think it could be that their findings in muons are actually hinting at a deeper structure in physics that has yet to be discovered and that studying muons could once again lead to new revelations.

    “The g-2 factor has been measured for other particles,” says Fermilab physicist Tammy Walton.  “It’s been very precisely measured for the electron. It’s also been measured for composite particles, like the proton and neutron. But the large mass of muons make them more sensitive to new physics.”

    Fermilab recently began the next generation Muon g-2 experiment, which physicists hope along with J-PARC in Japan will unequivocally confirm whether or not theory agrees with nature. Funded by the DOE's Office of Science, the experiment at Fermilab has been taking data since 2017.

    “We hope to get 20 times the number of muons, giving us a fourfold reduction in statistical uncertainty,” says Erik Swanson, a research engineer at the University of Washington. “If our central value stays the same as that generated at Brookhaven, then we will have confirmed without a doubt the discrepancy between theory and observation. Otherwise it might just be that theory was right all along.”

    If the theory is broken, physicists will have a lot of explaining to do, which could lead them to a new understanding of the particles and forces that make up our universe and the forces that govern them. Not bad work for a particle nobody ordered.

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  • Search for new physics through multiboson production

    ParticleNews at 2020-06-11T14:28:35Z

    "Search for new physics through multiboson production"

    Search for new physics through multiboson production cagrigor Wed, 06/10/2020 - 12:21

    Search for new physics through multiboson production
    (Image: CERN)

    This media update is part of a series related to the 2020 Large Hadron Collider Physics conference, which took place from 25 to 30 May 2020. Originally planned to take place in Paris, the conference was held entirely online due to the COVID-19 pandemic.

    At the LHCP conference this year, the ATLAS and CMS collaborations presented new results relating to a physics process called vector boson scattering. CMS also reported the first observation of the so-called “massive triboson production. Studying these processes to test the Standard Model is important as it could shed light on new physics. The results were presented online at the virtual LHCP conference, originally due to be held in Paris.

    During proton collisions at the LHC, many particles, including the carriers of the electroweak force – photons and W and Z bosons – are produced. These bosons are often referred to simply as vector bosons, in the Standard Model, and one of the processes that leads to their pair production is called vector boson scattering.

    Vector boson processes are an excellent probe to seek deviation from theoretical predictions. Two rare processes that are of particular interest as they probe the self-interactions of four vector bosons are diboson production via vector boson scattering and triboson production”. The observation and measurement of these processes are important as they test the electroweak symmetry breaking mechanism, whereby the unified electroweak force separates into electromagnetic and weak forces in the Standard Model, and are complementary to the measurements of Higgs boson production and decay.

    In a vector boson scattering process, a vector boson is radiated from a quark in each proton and these vector bosons scatter off one another to produce a diboson final state. Triboson production refers instead to the production of three massive vector bosons.

    At the LHCP conference, physicists from the ATLAS and CMS collaborations presented new searches for the production of a pair of Z bosons via electroweak production including the vector boson scattering mechanism. ATLAS observed this process at 5.5 sigma and CMS reported strong evidence. CMS also reported the first observation of a W boson produced in association with a photon through the vector boson scattering process, as well as more precise measurements of the same-sign WW production, and an observation of the vector boson scattering production of a W and a Z boson, complementing earlier ATLAS observations.

    Another way to probe four-boson interaction is to study the very rare production of three massive bosons or tribosons. This April, the CMS experiment released a 5.7 sigma result of the triboson phenomenon, establishing it as a firm observation, following the first evidence of this process seen by the ATLAS experiment last year.

    Most physics processes of fundamental particles involve two or more individual particles that interact with each other via an intermediary particle that is emitted or absorbed in the process.

    “The more bosons produced, the rarer the event. This new observation of tribosons was very difficult because it is a much rarer process than the one that led to the Higgs boson discovery, and very interesting because it may reveal signs of new particles and anomalous interactions,” says Roberto Carlin, CMS spokesperson.

    In the triboson and vector boson scattering processes, W and Z can interact with themselves to create more W and Z particles, producing two or three bosons. W and Z being highly unstable particles, they quickly decay into leptons (electrons, muons, taus and their corresponding neutrinos) or quarks. But such processes are extremely rare and the diboson and triboson events that physicists look for are mimicked by background processes, making them even more difficult for physicists to analyse.

    “To separate signal from background, physicists have to be ingenious and employ advanced machine learning algorithms. This is a challenging task for such rare processes, and requires meticulous and thorough studies,” says Karl Jakobs, ATLAS spokesperson.

    The measurements of vector boson scattering and triboson production presented at LHCP 2020 are consistent with the predictions made by the Standard Model, which remains our best understanding of fundamental particles and their interactions. The above observations also provide physicists with tools to probe quartic self-interaction between massive electroweak bosons. The current measurements place constraints on the strength at which these quartic interactions take place and increased precision from the use of new datasets could open up horizons for new physics at higher energy scales in the LHC and lead to possible discoveries of new particles.

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  • JanKusanagi at 2020-06-10T17:36:56Z


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  • Stephen Michael Kellat at 2020-06-03T03:45:56Z

    » Stephen Sekula:

    “Did you get this up and available for reading and/or purchase?”

    @Stephen Sekula Yes, I did:

    I tried to keep it as close to the limits of current tech as I could before hitting fantasy. It counts as an "alternate history" of how history could have played out.

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  • Neutron stars show their cores

    ParticleNews at 2020-06-02T08:29:01Z

    "Neutron stars show their cores"

    Neutron stars show their cores

    abelchio Tue, 06/02/2020 - 09:43
    Artist’s impression of a neutron star’s interior. The deeper the layer, the denser it is.
    Shows an illustration of neutron star. (Image: CERN)

    Dive into the interior of neutron stars and you’ll find, guess what, neutrons. But it’s not as simple as that. The deeper the dive, the fuzzier and denser the interior gets. There’s no shortage of theories as to what might make up the centre of these cosmic objects. One hypothesis is that it’s filled with free quarks, not confined inside neutrons. Another is that it’s made of hyperons, particles that contain at least one quark of the “strange” type. Another still is that it consists of an exotic state of matter called a kaon condensate.

    In a paper published today in the journal Nature Physics, a quintet of researchers including Aleksi Kurkela from CERN’s Theory department provides evidence that massive neutron stars can contain cores filled with free quarks. Such quark matter resembles the dense state of free quarks and gluons that is thought to have existed shortly after the Big Bang and can be recreated at particle colliders on Earth, such as the Large Hadron Collider.

    To reach this evidence, the researchers combined information from astronomical observations of neutron stars with theoretical calculations. While astronomical observations provide some information about the stars’ interior, they don’t reveal their exact make-up.

    The theoretical calculations involved describing the state of matter inside a neutron star from the crust all the way down to the centre. To do this, the researchers used so-called equations of state, which relate the pressure of a state of matter to the energy density – the amount of energy packed into a system or region of space per unit volume.

    The team then plugged two pieces of information from astronomical data into these calculations: the observation that neutron stars can have masses equivalent to two Suns; and the possible values of a property called tidal deformability for a neutron star with a mass of about 1.4 times that of the Sun. The tidal deformability describes the stiffness of a star in response to stresses caused by the gravitational pull of a companion star, and was previously derived from observations of gravitational waves (ripples in the fabric of spacetime) emitted by the merger of two neutron stars.

    From this combination of theory and data, the researchers find that the cores of neutron stars with a mass 1.4 times that of the Sun should be filled with neutrons. By contrast, more massive stars can contain large quark-matter cores. For example, a 2-solar-mass neutron star with a radius of about 12 km could have a quark-matter core with a radius of about 6.5 km – about half of the star’s radius.

    “Our analysis does not completely rule out the existence of massive stars with neutron cores but it demonstrates that quark-matter cores are not an exotic alternative,” says Kurkela. “We can’t wait to incorporate new neutron-star data into our analysis and see how they will affect this conclusion.”

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  • JanKusanagi at 2020-05-26T18:35:33Z

    So... C+17 then? 😆

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  • Explaining Coronavirus Misinformation

    Assessment of U.S. Politics at 2020-02-07T19:14:37Z

    "Explaining Coronavirus Misinformation" writers Jessica McDonald and Angelo Fishera were interviewed by a South Korean radio program about their work combating misinformation related to the new coronavirus.

    The post Explaining Coronavirus Misinformation appeared first on

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  • MICE brings muon collider closer to reality

    ParticleNews at 2020-02-05T23:28:10Z

    "MICE brings muon collider closer to reality"

    The Muon Ionization Cooling Experiment has achieved its goal of squeezing a beam of muons before they decay.

    Scientist working on a new particle collider

    Scientists have announced a breakthrough that could be key to the creation of a powerful new kind of particle collider. 

    As reported in the journal Nature, the Muon Ionization Cooling Experiment, or MICE, has for the first time demonstrated the successful taming of a beam of particles called muons through a process called transverse ionization cooling. 

    MICE began at the UK’s Rutherford Appleton Laboratory two decades ago, but the technique the experiment tested was first proposed in the 1970s, with some significant developments in the 1990s. If scientists could make the technique work, it could allow them to one day accelerate and collide beams of muons. 

    Muons—which are heavy relatives of electrons—are interesting to accelerator scientists for a number of reasons. For one, they are more massive than the particles they have traditionally used in colliders. The more massive the particles you collide, the higher the energies you can reach with your collisions, and the more potential you have to make discoveries as that energy converts into new particles. 

    Muons are about 200 times heavier than electrons. The large muon mass suppresses synchrotron radiation—the process through which particles lose energy as they are bent around a circular particle accelerator. That means that scientists building a muon collider could send the particles around a tighter loop than the 17-mile-long tunnel used at CERN to house first the Large Electron-Positron collider and now the Large Hadron Collider.

    It’s also beneficial that muons, like electrons, seem to be fundamental particles, not made up of smaller constituent parts. In contrast, the protons in the LHC are made up of quarks and gluons. Proton-proton collisions are actually collisions between those smaller particles, which carry only a portion of the proton’s total energy.

    Scientists have thus far stuck to colliding particles like protons, antiprotons, electrons, positrons and ions. One reason for this is the difficulty of producing a sufficient amount of muons and funneling them into an organized beam for an accelerator to propel and collide. 

    Scientists create a beam of muons by smashing a beam of protons into a target. The muons released in the collision take the form of a diffuse cloud of particles that are not all traveling in the right direction. Scientists can use magnetic lenses to steer the muons in one of two ways—either condensing them into a tight bunch, ready to collide, or sending them the right way, toward whatever they want them to collide with. But they can’t do both at once.

    On top of that, there’s the issue of the muon’s lifetime. At rest, a muon decays on average after a mere 2 millionths of a second. After that, there’s no muon to collide. However, if you can accelerate a muon close to the speed of light before that deadline, its lifetime will stretch longer thanks to special relativity. 

    What MICE scientists needed to do was to show that they could organize a muon beam in preparation for acceleration before their time was up. 

    MICE scientists passed a beam of muons through an absorber, slowing down their momentum perpendicular to the beam direction and focusing them into a tight beam. They then used radio-frequency cavities to speed up the momentum of the beam in the forward direction. They repeated this until they were left with a focused, well-behaved beam of muons traveling the right way. 

    The scientists undertook the difficult task of measuring each particle one-by-one to evaluate their efforts. They found that they had achieved what they set out to do, bringing scientists a step closer to potentially making a muon collider a reality.

    The MICE experiment received funding from the UK’s Science and Technology Facilities Council, the US Department of Energy, the US National Science Foundation and institutions around the world.

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  • So, we're back?

    Stephen Michael Kellat at 2020-01-31T00:57:05Z

    Related work: Kellat, S. M. (2020, January 28). A Disappearance. Coyote Works.

    Beware falling anvils, comrades. I don't like when this site makes extended disappearances. I'm most certainly not visible in the Mastodon/Pleroma/GNU Social/whatever realms nowadays. If I am present on Twitter then that presence can't be acknowledged at this time. If Identica takes an extended nap you should look for me on the Coyote Works blog. It runs ikiwiki and so far hasn't gone kablooey on me.

    Then again, much like a tree falling in a forest with nobody around I feel pretty sure nobody will see this post let alone the blog.

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    Somebody did 😅

    JanKusanagi at 2020-01-31T09:17:10Z

  • The beta of Plasma Desktop 5.18 is out!!

    at 2020-01-22T23:50:18Z

    “This new version of your favorite desktop environment adds neat new features that make your life easier, including clearer notifications, streamlined settings for your system and the desktop layout, much improved GTK integration, and more. ” 😎

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