cern – Australian Science

New light on dark matter: space station magnet attracts praise

Kevin Orrman-Rossiter — Wed, 10 Apr 2013 00:02:01 +0000

The AMS aboard the ISS. Photo credit NASA.

Nobel prizewinner Samuel Ting, early Thursday morning (March 4, 2:00 AEDT), announced the first results from the Alpha Magnetic Spectrometer (AMS) search for dark matter. The findings, published in Physical Review Letters, provide the most compelling direct evidence to date for the existence of this mysterious matter.

In short, the AMS results have shown an excess of antimatter particles within a certain energy range. The measurements represent 18 months of data from the US$1.5 billion instrument.

The AMS experiment is a collaboration of 56 institutions, across 16 countries, run by the European Organisation for Nuclear Research (CERN). The AMS is a giant magnet and cosmic-ray detector complex fixed to the outside of the International Space Station (ISS).

Dark matter matters

The visible matter in the universe, such as you, me, the stars and planets, adds up to less than 5% of the universe. The other 95% is dark, either dark matter or dark energy. Dark matter can be observed indirectly through its interaction with visible matter but has yet to be directly detected.

Cosmic rays are charged high-energy particles that permeate space. The AMS is designed to study them before they have a chance to interact with Earth’s atmosphere.

Magnet bends in opposite directions charged particles/antiparticles. Transition Radiation Detector (TRD) identifies electrons and positrons among other cosmic-rays. Time-of-Flight System (ToF) warns the sub-detectors of incoming cosmic-rays. Silicon Tracker (Tracker) detects the particle charge sign, separating matter from antimatter. Ring-Imaging Cherenkov Detector (RICH) measures with high precision the velocity of cosmic-rays. Electromagnetic Calorimeter (ECAL) measures energy of incoming electrons, positrons and γ-rays. Anti-Coincidence Counter (ACC) rejects cosmic rays traversing the magnet walls. Tracker Alignment System (TAS) checks the Tracker alignment stability. Star Tracker and GPS defines the position and orientation of the AMS-02 experiment. Electronics transform the signals detected by the various particle detectors into digital information to be analyzed by computers. Diagram credit AMS Collaboration.

An excess of antimatter within the cosmic rays has been observed in two recent experiments – and these were labelled as “tantalising hints

Cite this article:
Orrman-Rossiter K (2013-04-10 00:02:01). New light on dark matter: space station magnet attracts praise. Australian Science. Retrieved: May 04, 2024, from http://australianscience.com.au/physics/new-light-on-dark-matter-space-station-magnet-attracts-praise/

test

The post New light on dark matter: space station magnet attracts praise appeared first on Australian Science.

The Higgs: An Unexpected Boson

Markus — Tue, 01 Jan 2013 00:14:39 +0000

The interesting thing about research is that the most interesting results are always the ones which are unexpected. This is particularly true out in the frontiers of physics where, frequently, no one really knows quite what to expect. While news reporters were swift to leap to the conclusion that the Higgs boson had been discovered back in July, the scientists at the CERN press conference were noticeably hesitant to make any such claims outright. Interestingly, it seems that they were wise to do so – in light of the more recent findings, their apprehension has been proven to be well advised. Simply but confusingly, the CERN experiments seem to have yielded two bosons for the price of one.

A huge experiment like any of those taking place at the Large Hadron Collider (LHC) collects a lot of data, and believe me when I say that analysing and interpreting the data you can collect from any experiment is not an easy task. A lot of effort needs to be made in order to make sure you understand everything you’re seeing. Back in July, there were a few obvious things which were uncertain. For one, the “Higgs-like particles” observed at CERN appeared to be breaking up and decaying into photons more rapidly than predicted. This was the first clue that something unexpected was going on with the LHC data. However, on closer inspection, the results were so unexpected that there was thought to be a fault with the equipment. Everyone was hoping to find a peak for the Higgs boson, but no one expected there to be two! With one signal detected at 123.5 GeV and a second at 126.6 GeV, there’s a statistically significant difference of 3.1 GeV between the two. While the data have been checked and re-checked throughout November, they appear to be perfectly sound. As far as anyone can tell, these are two genuine detections of two particles.

What exactly this means is very much an open question. Assuming these data are correct, aren’t any existing theories which explain why there would be two Higgs-like signals so close together. Some hypotheses predict multiple Higgs bosons, but none predict them to be so close together. What’s more, these two particles seem to fragment into different products – the 123.5 GeV particle decays into two Z-particles (a different, more familiar variety of boson), while the 126.6 GeV particle decays into photons. So what’s going on?

Physicists are interesting folk, and I’m sure some would be fascinated if this turned out to be something new. Fabiola Gianotti, director of the ATLAS experiment at CERN has appeared noticeably excited before by the prospect of new and unknown physics being discovered. However, the other thing about physicists is that by their nature, they need to be highly skeptical, particularly when it comes to their own work. Adam Falkowski, a Paris-based particle physicist, states what most researchers are probably thinking on his blog Résonaances – that the result is most likely due to a “a systematic problem”. In other words, a problem in the apparatus such as a poorly calibrated detector. To date, there is no explanation from CERN for the unusual data. So is it a glitch, or could there really be two particles being detected here?

Whatever is being seen here, it certainly appears to be at least subtly different to what the theories predict. Even if the second detection turns out to be a fault in the detectors at CERN, the fact that the original detection appeared to decay into photons more readily than it should is still unusual – though as noted by Matt Strassler in his blog, Of Particular Significance, “the excess is still not yet 3 standard deviations. Deviations of this size do come and go. And we don’t have confirmation from CMS. So the situation remains tantalizing but unfortunately not yet very convincing.” Right now, we still need to wait for official confirmation from CERN. Personally, I suspect that isn’t likely to happen until they know more about it themselves. A further announcement is currently scheduled for March 2013.

Cite this article:
Hammonds M (2013-01-01 00:14:39). The Higgs: An Unexpected Boson. Australian Science. Retrieved: May 04, 2024, from http://australianscience.com.au/research-2/the-higgs-an-unexpected-boson/

test

The post The Higgs: An Unexpected Boson appeared first on Australian Science.

The Higgs boson does exist: New particle observed at 125 GeV

Editorial Board — Wed, 04 Jul 2012 08:24:50 +0000

Australian researchers helped design and build parts of the ATLAS detector and helped analyse the results.

Researchers using two huge detectors at the Large Hadron Collider announced the results of their searches at a joint scientific seminar in Geneva and Melbourne, where the International Conference on High Energy Physics is being held.

In a joint seminar today at CERN and the “ICHEP 2012

test

The post The Higgs boson does exist: New particle observed at 125 GeV appeared first on Australian Science.

Mr Boson, I presume…?

Charles Ebikeme — Tue, 03 Jul 2012 06:04:25 +0000

When Peter Higgs steps out onto the tarmac at an airport near the franco-swiss border, it will probably be with equal parts trepidation and elation.

CERN, the European Organization for Nuclear Research, and the world’s leading laboratory for particle physics, is to hold a scientific seminar on July 4th, with Peter Higgs in attendance, to deliver the latest update in the search for the Higgs boson — the famed “God Particle

test

The post Mr Boson, I presume…? appeared first on Australian Science.