Tag Archives: physics

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.

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.

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.

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.

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.

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.

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.

Brookhaven Labs has achieved the hottest man-made temperature ever, 4 trillion degrees Celsius.

Brookhaven Labs has achieved the hottest man-made temperature ever, 4 trillion degrees Celsius.

In the process, the scientists have found that matter at these temperatures acts more like a liquid than a gas, something they did not expect.

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.

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.

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.

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.

Has dark matter been identified?

From a paper published today on the Los Alamos astro-ph preprint website, scientists suggest that three different physics experiments might have identified dark matter. From the abstract:

Three dark matter direct detection experiments (DAMA/LIBRA, CoGeNT, and CRESST-II) have each reported signals which are not consistent with known backgrounds, but resemble that predicted for a dark matter particle with a mass of roughly ~10 GeV. . . . In this article, we compare the signals of these experiments and discuss whether they can be explained by a single species of dark matter particle, without conflicting with the constraints of other experiments. We find that the spectrum of events reported by CoGeNT and CRESST-II are consistent with each other and with the constraints from CDMS-II, although some tension with xenon-based experiments remains. Similarly, the modulation signals reported by DAMA/LIBRA and CoGeNT appear to be compatible, although the corresponding amplitude of the observed modulations are a factor of at least a few higher than would be naively expected, based on the event spectra reported by CoGeNT and CRESST-II. This apparent discrepancy could potentially be resolved if tidal streams or other non-Maxwellian structures are present in the local distribution of dark matter.

The last sentence above suggests that the differences between the various experiments might be explained by the motion of dark matter itself as it flows through the solar system.

This conclusion is very tentative. The scientists admit that there remain conflicts between the results of the three experiments, and that there also could be explanations other than dark matter for the results. Furthermore, the results of other experiments raise questions about this conclusion.

Nonetheless, it appears that physicists might be closing in on this most ghostlike of all particles in the universe.

1 2