cab1729:

BBC News - Alpha Magnetic Spectrometer zeroes in on dark matter

A $2bn experiment on the space station has made observations that could prove to be the first signs of dark matter, a mysterious component of the Universe.

The Alpha Magnetic Spectrometer (AMS) surveys the sky for high-energy particles, or cosmic rays.

It has seen evidence of what may prove to be dark matter colliding with itself in what is known as “annihilation”.

But scientists stress a precise description of this mysterious cosmic component is still some way off.

“It could take a few more years,” AMS deputy spokesman Roberto Battiston, a professor of physics at the University of Perugia, told BBC News.

Dark matter accounts for most of the mass in the Universe.

It cannot be seen directly with telescopes, but astronomers know it to be out there because of the gravitational effects it has on the matter we can see.

Galaxies, for example, could not rotate the way they do and hold their shape without the presence of dark matter.

The AMS - a kind of particle accelerator and nicknamed the “space LHC” in reference to the Large Hadron Collider here on Earth - has been hunting for some indirect measures of dark matter’s properties.

The AMS counts the numbers of electrons and their anti-matter counterparts - known as positrons - falling on its detectors.

Theory suggests that showers of these particles should be produced when dark-matter particles collide somewhere in space and destroy each other.

In a paper to be published in the journal Physical Review Letters, the AMS team reports the observation of a slight excess of positrons in the positron-electron count - an outcome expected of these dark matter annihilations.

The group also says the positrons fall on the AMS from all directions in the sky with no particular variation over time.

This is important because specific locations or timing variations in the signal could indicate a more conventional source for the particles, such as a pulsar (a type of neutron star) rather than dark matter.

The AMS was placed on the International Space Station in 2011. The longer it operates, the better its statistics will be and the more definitive scientists can be in their statements.

The Physical Review Letters paper reports the positron-electron count in the energy range of 0.5 to 350 gigaelectronvolts (GeV).

The behaviour of the positron excess across this energy spectrum fits with the researchers’ expectations. However, the “smoking gun” signature would be to see a rise in this ratio and then a dramatic fall. This has yet to be observed.

“At the moment, all we can say is that the (dark matter) particles could have a mass of several hundred gigaelectronvolts, but there is much uncertainty,” said Prof Battiston. (By way of comparison, a proton, the particle in the nucleus of every atom, has a mass of about 1 GeV).

An extra dimension for LHCb

The Standard Model of particle physics is like a jigsaw into which physicists are gradually fitting pieces. Though most results fit well and are compatible with Standard Model predictions, there are physicists hoping for results that don’t fit the jigsaw and so could point to new physics.

Jonas Rademacker of the University of Bristol and the Large Hadron Collider beauty (LHCb) collaboration is one of those physicists. “We’re hoping to find the jigsaw piece that looks like it should fit, but when you look very closely, the pattern isn’t quite right,” he says.

Rademacker has developed a new way of analysing data from LHCb that offers an unprecedented level of detail and precision. His technique requires analyzing special scatter plots called Dalitz plots in five dimensions rather than two. These plots represent the strange quantum-mechanical interference effects that happen in particle decays, and Rademacker and his colleagues use them at LHCb as a precision tool to measure CP violation.

Though five-dimensional analysis is a complicated feat, it is worth the effort because it significantly increases the precision of LHCb measurements.

Read More

By: Stephanie Hills

cab1729:

For There We Are Captured—-The Geometry of Spacetime

What does it mean when we say spacetime is “curved” or “flat?”

The answer lies in the interface between differential geometry and physics.

amnhnyc:

Have plans tonight? We’re live streaming the 2013 Isaac Asimov Memorial Debate: The Existence of Nothing, hosted by Hayden Planetarium Director Neil deGrasse Tyson. 

Tune in at amnh.org/live. The fun begins at 7:30 pm EST.

Image (c) AMNH/R. Mickens

thenewenlightenmentage:

Beyond Higgs: 5 Elusive Particles That May Lurk in the Universe

With the recent confirmation of a Higgs Boson discovery, many physicists were at least a little disappointed. That’s because all signs point to it confirming the Standard Model, the nearly 100-year-old theory that explains the tiny bits of matter that make up the universe.

But some physicists still hold out hope for results that could provide a bigger shake-up, looking for the Large Hadron Collider (LHC) and physics experiments at other facilities to reveal other hidden particles lurking in the universe. From gravitons to winos, here are five bizarre things that may exist beyond the Higgs:

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scienceisbeauty:

Experimental set-up of the quantum teleportation device including an entangled light-emitting diode (ELED) and an assortment of beam splitters polarization controllers, detectors, and photodiodes.

Source: Quantum teleportation performed with light from a quantum dot embedded in an LED, Phys.Org