Tag archives: dark matter
By Tushna Commissariat
A final mystery that was mentioned at the Neutrino 2016 I attended in London this week was yet another unexpected “bump” in data at 5 MeV, measured while monitoring the neutrino flux from nuclear power plants. Starting with the RENO experiment in 2012, it was spotted by the Double Chooz experiment in 2014 and finally by the Daya Bay neutrino experiment earlier this year. While the initial signal was not of high enough statistical significance, it has now held up over time and more measurements.
By Tushna Commissariat
More data are definitely needed in the quest for the sought-after sterile neutrino. That much was clear as more than 10 different global neutrino detectors announced at the Neutrino 2016 conference in London that they have found no evidence for the slippery particle’s existence. The sterile neutrino is a hypothetical and much-debated fourth type of neutrino that would contribute mass, but only interact with the other three “active neutrinos”, making it that much more difficult to detect. In the video above, Physics World features editor Louise Mayor explains why researchers are so keen to nail down this particle, should it exist, as it may single-handedly explain some of the biggest mysteries in physics today, including dark matter.
By Tushna Commissariat
As you may have read, earlier this week I was at Neutrino 2016 – the 27th International Conference on Neutrino Physics and Astrophysics – in London. Although I was only at two days of the week-long conference, I still have neutrinos on my mind. A whole host of experiments presented various data and updates. Indeed, the researchers presenting the latest results from the Tokai to Kamioka (T2K) experiment in Japan and the NOvA Neutrino Experiment at Fermilab in the US had some interesting things to say.
T2K collaborator Hirohisa Tanaka, from the University of Toronto in Canada, revealed that the experiment’s most recent data seem to support earlier hints that there may be different oscillation probabilities for neutrinos and antineutrinos. If these data hold up, then it would have big consequences – the standard model of neutrino physics says that these two oscillation rates should be the same so as not to violate charge–parity (CP) symmetry. According to the collaboration, their observed “electron antineutrino appearance event rate is lower than would be expected based on the electron neutrino appearance event rate, assuming that CP symmetry is conserved”.
By Tushna Commissariat at the Royal Geographical Society in London
“There are still many things to be studied in neutrinos,” said 2015 Nobel laureate Takaaki Kajita at the first talk of the Neutrino 2016 conference that began in London today. I couldn’t help but notice that his statement rang very true, as the day’s talks touched on everything from high-energy neutrinos to dark-matter searches to monitoring nuclear reactors. This year, more than 700 physicists from all over the world are attending the week-long conference, which is taking place at the historic Royal Geographical Society in London.
By Louise Mayor in Waterloo, Canada
Right now, top physicists from around the world are arriving in Waterloo, Canada, to attend a unique conference. Christened Convergence, the meeting is the brainchild of Neil Turok, director of the Perimeter Institute for Theoretical Physics (PI) in Waterloo, where the event will be based. I spoke to Turok to find out what motivated him to set up this conference, what makes it so special, and what he hopes it will achieve.
By Hamish Johnston at the CAP Congress in Edmonton, Alberta
I’m a bit of a DIY enthusiast and one thing that I know about drilling into a masonry wall is that you should hold a vacuum-cleaner hose to the hole or you will end up with dust all over the wall and the floor below. Believe it or not, that is exactly what workers at SNOLAB in Canada do in order to keep background levels of radiation from affecting their dark-matter and neutrino detectors.
By Matin Durrani
A couple of years back, I had the pleasure of travelling 1100 metres below ground to visit a dark-matter laboratory at the bottom of the Boulby Mine on the north-east coast of England. The journey was certainly memorable – it involved plunging down in a rattling lift cage for several minutes with a group of miners setting off on their morning shift. Once in the lab – housed inside a souped-up set of trailers – I interviewed physicist Sean Paling about the experimental projects going on there.
Setting up an underground lab, like that at Boulby, certainly doesn’t come cheap and in recent years, many have started to diversify into new areas. In the May issue of Physics World, which is now out in print and digital formats, Paling and his colleague Stephen Sadler – who is director at DURRIDGE UK Radon Instrumentation – describe the renaissance in the science taking place far beneath our feet. Studies in underground labs now range from Mars rovers to muon tomography and from radioactive dating to astrobiology.
By Hamish Johnston
Cosmic rays, dark matter and other astrophysical mysteries are being debated with much vigour at a three-day conference that began this morning at CERN in Geneva. Called “AMS Days at CERN”, the meeting will include presentations of the latest results from the Alpha Magnetic Spectrometer (AMS).
Located on the International Space Station, the AMS measures the energy of high-energy charged particles from the cosmos – otherwise known as cosmic rays. These particles are of great interest because they offer us a window into some of the most violent processes in the universe. Some cosmic rays have probably been accelerated during supernova explosions while others could be produced as matter is sucked into the supermassive black holes that lie at the centres of many galaxies.
By Matin Durrani
Unless you’re prepared to modify our understanding of gravity – and most physicists are not – the blunt fact is that we know almost nothing about 95% of the universe. According to our best estimates, ordinary, visible matter accounts for just 5% of everything, with 27% being dark matter and the rest dark energy.
The July issue of Physics World, which is out now in print and digital formats, examines some of the mysteries surrounding “the dark universe”. As I allude to in the video above, the difficulty with dark matter is that, if it’s not ordinary matter that’s too dim to see, how can we possibly find it? As for dark energy, we know even less about it other than it’s what is causing the expansion of the universe to accelerate and hence making certain supernovae dimmer (because they are further away) than we’d expect if the cosmos were growing uniformly in size.
By Calla Cofield at the APS April Meeting in Savannah, Georgia
Scientists looking at data from the Baryon Oscillation Spectroscopic Survey (BOSS), the largest programme in the third Sloan Digital Sky Survey, have measured the expansion rate of the universe 10.8 billion years ago — a time prior to the onset of accelerated expansion caused by dark energy. The measurement is also the most precise measurement of a universal expansion rate ever made, with only 2% uncertainty. The results were announced at a press conference at the APS’s April meeting on Monday, at the same time that the results were posted on the arXiv preprint server.
The rate of universal expansion has changed over the course of the universe’s lifetime. It is believed to have gradually slowed down after the Big Bang, but mysteriously began accelerating again about 7 billion years ago (by rippstein). BOSS and other observatories have previously measured expansion rates going back 6 billion years.