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[1402.5382] Pathways of History of Elementary Particle Physics

“RT @PhysicsPaper: Pathways of History of Elementary Particle Physics. http://t.co/ljZGi4zJLW”
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Einstein’s lost theory uncovered

Einstein’s lost theory uncovered | Theoretical Physics | Scoop.it
“Physicist explored the idea of a steady-state Universe in 1931.”The Big Bang theory had found observational support in the 1920s, when US astronomer Edwin Hubble and others discovered that distant galaxies are moving away and that space itself is expanding. This seemed to imply that, in the past, the contents of the observable Universe had been a very dense and hot ‘primordial broth’.But, from the late 1940s, Hoyle argued that space could be expanding eternally and keeping a roughly constant density. It could do this by continually adding new matter, with elementary particles spontaneously popping up from space, Hoyle said. Particles would then coalesce to form galaxies and stars, and these would appear at just the right rate to take up the extra room created by the expansion of space. Hoyle’s Universe was always infinite, so its size did not change as it expanded. It was in a ‘steady state’.The newly uncovered document shows that Einstein had described essentially the same idea much earlier. “For the density to remain constant new particles of matter must be continually formed,” he writes. The manuscript is thought to have been produced during a trip to California in 1931 — in part because it was written on American note paper.It had been stored in plain sight at the Albert Einstein Archives in Jerusalem — and is freely available to view on its website — but had been mistakenly classified as a first draft of another Einstein paper. Cormac O’Raifeartaigh, a physicist at the Waterford Institute of Technology in Ireland, says that he “almost fell out of his chair” when he realized what the manuscript was about. He and his collaborators have posted their findings, together with an English translation of Einstein’s original German manuscript, on the arXiv preprint server (C. O’Raifeartaigh et al. Preprint at http://arxiv.org/abs/1402.0132; 2014) and have submitted their paper to the European Physical Journal.“This finding confirms that Hoyle was not a crank,” says study co-author Simon Mitton, a science historian at the University of Cambridge, UK, who wrote the 2005 biography Fred Hoyle: A Life in Science. The mere fact that Einstein had toyed with a steady-state model could have lent Hoyle more credibility as he engaged the physics community in a debate on the subject. “If only Hoyle had known, he would certainly have used it to punch his opponents,” O’Raifeartaigh says.Although Hoyle’s model was eventually ruled out by astronomical observations, it was at least mathematically consistent, tweaking the equations of Einstein’s general theory of relativity to provide a possible mechanism for the spontaneous generation of matter. Einstein’s unpublished manuscript suggests that, at first, he believed that such a mechanism could arise from his original theory without modification. But then he realized that he had made a mistake in his calculations, O’Raifeartaigh and his team suggest. When he corrected it — crossing out a number with a pen of a different colour — he probably decided that the idea would not work and set it aside.
Via Dr. Stefan Gruenwald
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Understanding Our Universe at Levels Too Small to See

Understanding Our Universe at Levels Too Small to See | Theoretical Physics | Scoop.it
“ Among potential evidence that would further support the Big Bang theory is the cosmic gravitational wave background.”
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Quantum Mechanics May Be Proven by Distant Quasars - The Escapist

Quantum Mechanics May Be Proven by Distant Quasars - The Escapist | Theoretical Physics | Scoop.it
“ MIT News Quantum Mechanics May Be Proven by Distant Quasars The Escapist MIT researchers have proposed an experiment involving the observation of distant quasars that could close a final loophole and prove our universe is governed by quantum...”
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Cosmic mismatch hints at the existence of a fourth type of neutrino

Cosmic mismatch hints at the existence of a fourth type of neutrino | Theoretical Physics | Scoop.it
Neutrinos, some of the most abundant particles in the universe, are also among the most mysterious. We know they have mass but not how much. We know they come in at least three types, or 'flavors' — but there may be more. A new study found that a mismatch between observations of galaxy clusters and measurements of the cosmic background radiation could be explained if neutrinos are more massive than is usually thought. It also offers tantalizing hints that a fourth type of hitherto unseen neutrino exists.The tension between galaxy clusters and the cosmic microwave background (CMB) has been a brewing problem, albeit one that might be resolved simply by getting better measurements in the coming years (see 'Missing galaxy mass found'). The background radiation shows the small density variations in the early universe that would eventually cause matter to clump in some places and form voids in others. We can see the end product of this clumping in the recent universe by observing the spread of galaxy clusters across space.Theorists have long suggested that a fourth type of neutrino might exist, but so far proof of them has been elusive. Hints at some particle accelerator experiments2 lately have begun to suggest they are out there, however. "What's really interesting is that the mass of this sterile neutrino, is consistent with what the other experiments see," says physicist Joseph Formaggio of the Massachusetts Institute of Technology in Cambridge. "I think people are starting to look at the data and say maybe there's something there." And coincidentally another study3 supporting the idea of a sterile neutrino as well as heavier neutrino masses was also published in the same issue of PRL.For many years neutrinos were thought to be completely massless, but the discovery that they can swap flavors also proved that they have at least a little bit of mass. Each flavor’s state is thought to be a mixture of the three unknown neutrino masses — called mass 1, mass 2 and mass 3 for the time being — and this mixing is why any flavor has a chance of turning into one of the other flavors over time. The transformation is only possible if the mass states are different from one another, and such a difference is only possible if neutrinos' mass is nonzero, Formaggio explains.Experiments aiming to catch neutrinos in the act of switching flavours could help pin down the differences between the neutrino masses and tell us which weighs more—the so-called neutrino-mass hierarchy. One such experiment, called NuMI Off-Axis νe Appearance (NOvA), measured its first neutrinos last week. The experiment creates a beam of neutrinos at the Fermi National Accelerator Laboratory (Fermilab) near Chicago and sends them to two detectors — one near Fermilab and another 800 kilometres away in Ash River, Minnesota. All of the particles start as muon neutrinos but some precious few arrive at the distant detector having turned into electron neutrinos, which create a different signature. The frequency at which this happens is related to the difference between electron and muon neutrinos' masses.Another experiment based in Japan called the Japanese Tokai to Kamioka (T2K) project also looks for these transformations. The collaboration announced last week that it had observed a record total of 28 candidate mutations from muon into electron neutrinos, with only about five of the events predicted to be other processes masquerading as the real thing. It is the strongest evidence to date for this type of neutrino oscillation, although much more data will be needed to answer questions about neutrinos' masses. "It's sort of like a big mile marker in a long race," says Formaggio, who wrote an essay accompanying the publication of the result on 10 February in PRL. The two experiments are complementary, says NOvA deputy project leader Rick Tesarek. "There are some capabilities that NOvA has that T2K doesn’t have" and vice versa. The experiments use different detector technology that is sensitive to different effects, and the NOvA project has a longer distance between its neutrino beam and the far detectors.As these experiments gather more data the secrets of neutrino masses may be revealed. The coming years should also clarify whether galaxy cluster measurements are truly incompatible with the cosmic background radiation data, and hence whether they point toward heavier neutrino masses and/or a sterile neutrino.
Via Dr. Stefan Gruenwald
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Quarks Know Their Left From Their Right

Quarks Know Their Left From Their Right | Theoretical Physics | Scoop.it
Matter interacts through four fundamental forces: the electromagnetic force that creates light and chemical bonds, the strong nuclear force that binds quarks and nuclei, the weak nuclear force that produces a type of radioactive decay called beta decay, and gravity. There could be other forces – some theorists have speculated that a second version of the weak force may also exist. At one time, physicists assumed that all the forces obeyed a handful of symmetries. So, for example, a physical system should behave exactly like its mirror image, a symmetry known as parity.In 1957, physicists discovered that parity does not hold in particle interactions mediated by the weak force. For example, suppose you aim right-spinning electrons at nuclei and watch them bounce off. If you look at the tiny shooting gallery in a mirror, you'll see left-spinning electrons bouncing off the target. So if the interaction between electron and nucleus were mirror-symmetric, then the scattering of right- and left-spinning electrons should be the same. And, indeed, that’s exactly what would happen if the negatively charged electrons interacted with the positively charged nuclei only through the electromagnetic force.But the electrons also interact with the nuclei through the weak force, which violates parity and is not mirror symmetric. As a result, right-spinning and left-spinning electrons ricochet off the target differently, creating a slight asymmetry in their scattering pattern. That effect was seen at SLAC National Accelerator Laboratory in Menlo Park, California, in 1978 in an experiment called E122 that helped cement physicists' then-emerging standard model. A second weak force, if it exists, ought to give similarly lopsided results.But what about the quarks? Like electrons, they can spin one way or the other as they zip around inside protons and neutrons. And, according to the standard model, the right- and left-spinning quarks should interact slightly differently with an incoming electron, producing an additional asymmetry, or parity violation, when the spin of the incoming electrons is flipped. Now, Xiaochao Zheng, a nuclear physicist at the University of Virginia in Charlottesville, and colleagues have observed that smaller contribution, as they recently reported in Nature.That was no mean feat. To see the extra asymmetry, the incoming electron must strike the nucleus hard enough to blast out a single quark, setting off a shower of particles, as was done in E122 but not in subsequent experiments. Researchers must take great care to ensure that they alternately shine equally intense beams of right- and left-spinning electrons on the target. Using the electron accelerator at Thomas Jefferson National Accelerator Facility in Newport News, Virginia, the researchers shined 170 billion electrons on a target of liquid deuterium over 2 months in 2009. After crunching the data, they were able to measure the part-in-10,000 scattering asymmetry precisely enough to pull out the contribution from the quarks, albeit with a large uncertainty. The result agrees with the standard model prediction."They've measured something fundamental at the quark level that wasn't measured before," says William Marciano, a theorist at Brookhaven National Laboratory in Upton, New York. Maas notes that the result is not as exciting as it could have been, however. "They have not observed any new physics at the level of their precision," he says. The new result does place tighter limits on models that assume a second weak force exists, Maas says.The measurement is not the end of the road. The 101 members in the experimental team intend to repeat their measurement and hope to improve their precision by at least a factor of 5, Zheng says. That should enable them to test for new forces with far more sensitivity, she says. Marciano agrees that "this is just the first step." He notes that it might be beneficial that the asymmetry from the quarks is so small in the standard model, as that will make any deviation look relatively large.
Via Dr. Stefan Gruenwald
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