Tag Archives: physics

Physicists look for new alternatives to explain dark matter

The uncertainty of science: Having failed to detect WIMPs, their primary dark matter suspect, physicists are now looking at new and different candidates that might explain dark matter, and the new leading candidate is something called SIMPs.

The intensive, worldwide search for dark matter, the missing mass in the universe, has so far failed to find an abundance of dark, massive stars or scads of strange new weakly interacting particles (WIMPs), but a new candidate is slowly gaining followers and observational support.

Called SIMPs – strongly interacting massive particles – they were proposed three years ago by UC Berkeley theoretical physicist Hitoshi Murayama, a professor of physics and director of the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) in Japan, and former UC Berkeley postdoc Yonit Hochberg, now at Hebrew University in Israel.

Murayama says that recent observations of a nearby galactic pile-up could be evidence for the existence of SIMPs, and he anticipates that future particle physics experiments will discover one of them.

We shall see. The mystery remains, that we do not understand why most galaxies do not fly apart because their outer stars simply move too fast. Since all searches for ordinary matter have come up well short, dark matter remains the simplest explanation, though it still reminds me the theories of ether that once dominated physics, and never existed.

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Physicists shrink their next big accelerator

Because of high costs and a refocus in research goals, physicists have reduced the size of their proposed next big particle accelerator, which they hope will be built in Japan.

On 7 November, the International Committee for Future Accelerators (ICFA), which oversees work on the ILC, endorsed halving the machine’s planned energy from 500 to 250 gigaelectronvolts (GeV), and shortening its proposed 33.5-kilometre-long tunnel by as much as 13 kilometres. The scaled-down version would have to forego some of its planned research such as studies of the ‘top’ flavour of quark, which is produced only at higher energies.

Instead, the collider would focus on studying the particle that endows all others with mass — the Higgs boson, which was detected in 2012 by the Large Hadron Collider (LHC) at CERN, Europe’s particle-physics lab near Geneva, Switzerland.

Part of the reason for these changes is that the Large Hadron Collider has not discovered any new particles, other than the Higgs Boson. The cost to discover any remaining theorized particles was judged as simply too high. Better to focus on studying the Higgs Boson itself.

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Physicists fail to find sterile neutrino

The uncertainty of science: A year’s collection of data using IceCube, a gigantic neutrino telescope built in the icecap of Antarctica, has found no evidence of a theorized fourth type of neutrino.

To search for sterile neutrinos, Halzen’s team looked for the arrival of muon neutrinos that started life on the other side of Earth. These were originally produced by the collision of cosmic rays with air molecules in the atmosphere, and passed through the planet to reach the detector. The IceCube team hoped to find a dearth of muon neutrinos at particular energies. That would have suggested that some muon neutrinos had temporarily mutated into sterile neutrinos during their voyage.

But, after analysing the results of a year’s worth of data, the researchers found no feature suggesting the existence of sterile neutrinos around 1 eV. This is line with results from the European Space Agency’s Planck observatory, which concluded from cosmological evidence that there should only be three families of neutrinos in that mass range. “I hope that with our result and with the Planck result we are slowly walking our way back from this story,” says Halzen. The IceCube team are still taking data in their sterile neutrino hunt, but don’t expect their results to change, he adds.

Despite this null result, there is still a possibility that sterile neutrinos exist, but not at the mass predicted.

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Four elements added to periodic table

Scientists have now officially added four new elements to the periodic table, completing the discovery of all elements through 118.

All of the elements were created in the lab, by smashing lighter atomic nuclei together. The unstable agglomerations of protons and neutrons last mere fractions of a second before they fall apart into smaller, more stable fragments.

The teams that have been given credit for the discoveries can now put forward proposals for the elements’ names and two-letter symbols. Elements can be named after one of their chemical or physical properties, a mythological concept, a mineral, a place or country, or a scientist. Priority for discovering element 113 went to researchers in Japan, who are particularly delighted because it will become the first artificial element to be named in East Asia. When the element was first sighted 12 years ago, ‘Japonium’ was suggested as a name.

While creating element 119 is believed possible, beyond that it is thought unlikely that anything heavier can be produced in the lab.

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The creation in the lab of an as yet unnamed superheavy element adds weight to the theory that there might exist even heavier elements that are stable in nature.

The creation in the lab of an as yet unnamed superheavy element adds weight to the theory that there might exist even heavier elements that are stable in nature.

The scientists did not observe element 117 directly. Instead, they searched for its daughter products after it radioactively decayed by emitting alpha particles—helium nuclei with two protons and two neutrons. “The heavy nuclei makes an alpha decay to produce element 115, and this also decays by alpha decay,” says Jadambaa Khuyagbaatar of GSI, lead author of a paper reporting the results published on 1 May in Physical Review Letters.

After a few more steps in this decay chain, one of the nuclei produced is the isotope lawrencium 266—a nucleus with 103 protons and 163 neutrons that had never been seen before. Previously known isotopes of lawrencium have fewer neutrons, and are less stable. This novel species, however, has an astonishingly long half-life of 11 hours, making it one of the longest-lived superheavy isotopes known to date. “Perhaps we are at the shore of the island of stability,” Düllmann says.

If these superheavy elements could be created, they would be the stuff of science fiction. They might have properties that we would find extremely useful.

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Physicists have managed to create and confirm, for a brief moment, the existence of the 115th element of the periodic table.

Physicists have managed to create and confirm, for a brief moment, the existence of the 115th element of the periodic table.

In experiments in Dubna, Russia about 10 years ago, researchers reported that they created atoms with 115 protons. Their measurements have now been confirmed in experiments at the GSI Helmholtz Centre for Heavy Ion Research in Germany.

To make ununpentium [the new element’s temporary name] in the new study, a group of researchers shot a super-fast beam of calcium (which has 20 protons) at a thin film of americium, the element with 95 protons. When these atomic nuclei collided, some fused together to create short-lived atoms with 115 protons. “We observed 30 in our three-week-long experiment,” study researcher Dirk Rudolph, a professor of atomic physics at Lund University in Sweden, said in an email. Rudolph added that the Russian team had detected 37 atoms of element 115 in their earlier experiments.

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The Higgs boson has once again been confirmed with new data, and the scientists are disappointed!

The Higgs boson has once again been confirmed with new data, and the scientists are disappointed!

Alas, most of the Higgs results being presented this week at the Hadron Collider Physics symposium in Kyoto, Japan, have been well within our standard understanding. Physicists at ATLAS and CMS, the two largest particle detectors at the LHC, have about double the amount of data they did in July; this new data hasn’t dramatically changed the tentative conclusion that the LHC is seeing a plain-old Standard Model Higgs.

In other words, the theories are proving to be just about exactly right. No big surprises, which means no new mysteries to solve.

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How the Higgs boson explains the universe.

How the Higgs boson explains the universe.

And what it can’t explain:

The discovery [by the existence of the Higgs boson] that nature is beautifully symmetric means we have very little choice in how the elementary particles do their dance – the rules simply “come for free”. Why the universe should be built in such an elegant fashion is not understood yet, but it leaves us with a sense of awe and wonder that we should be privileged to live in such a place.

Science discovers how the universe operates. Philosophy and religion try to explain why. Thus, it is perfectly reasonable in a rational world to consider the existence of God, and why musings about the possibility of intelligent design do not contradict pure science.

And I speak not as a religious person, but as a secular humanist.

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From CERN: The experiments have observed a “particle consistent with long-sought Higgs boson.”

From CERN: The experiments there have now observed a “particle consistent with long-sought Higgs boson.”

The press release also emphasizes repeatedly the preliminary nature of this result. More details in this article, including this not unexpected punchline if you know science:

Already, the new boson seems to be decaying slightly more often into pairs of gamma rays than was predicted by theories, says Bill Murray, a physicist on ATLAS, the other experiment involved in making the discovery.

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Chinese physicists have discovered a key measurement that helps explain why and how can neutrinos magically oscillate between three different states.

Chinese physicists have discovered a key measurement that helps explain why and how neutrinos can magically oscillate between three different states. Moreover, the data

implies that there could be a slight asymmetry between neutrinos and antineutrinos—called CP violation—a slight asymmetry that might help explain why the universe evolved to contain so much matter and so little antimatter.

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CERN announces an update on the search for the Higgs Boson

Not there yet: CERN announces an update on the search for the Higgs Boson.

The main conclusion is that the Standard Model Higgs boson, if it exists, is most likely to have a mass constrained to the range 116-130 GeV by the ATLAS experiment, and 115-127 GeV by CMS. Tantalising hints have been seen by both experiments in this mass region, but these are not yet strong enough to claim a discovery.

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Higgs announcement from CERN on December 13

CERN will be making an announcement on the status of its search for the Higgs particle on December 13. From this interview of one of its scientists:

The thing I know for sure is that [CERN Director General] Rolf-Dieter Heuer, who must know the results of both experiments, says that on December 13 we will not have a discovery and we will not have an exclusion.

The inteview is fascinating, as he notes how the Higgs research might also have a bearing on the search for dark matter.

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Recent results from the Fermi Gamma-ray Space Telescope have found no evidence of dark matter, a result in some conflict with data obtained from several underground research detectors.

The uncertainty of science: Recent results from the Fermi Gamma-ray Space Telescope have found no evidence of dark matter, a result in some conflict with data obtained from several underground research detectors.

The mystery here is that there is no doubt that something causes the outer objects in galaxies to move faster than expected. Scientists have labeled this something as dark matter, guessing that some undetected and unknown mass exists in the outer reaches of galaxies, thereby increasing the gravity potential and hence the velocity in which objects move.

The problem is that they have yet to identify what that dark matter is.

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