Category Archives: Dark Matter

Upgraded LHC pushes physics into the unknown

There’s a certain degree of anticipation and anxiety among scientists at CERN and beyond as the Large Hadron Collider prepares to roar back into life after a two-year break.

Upgraded with more powerful magnets to smash particles together with almost twice its previous energy, this will bring with it the opportunity to discover new, even more massive particles – just as with the Higgs boson – that will signpost the way beyond our current understanding of particle physics, the Standard Model. Why do we think this? Because Einstein’s equation of energy-mass equivalence – more familiar to people as E=mc2 – tells us that in order to make more massive particles we need more energy – even more than the LHC has been capable of delivering so far.

Listen harder, hear more

But energy is only part of the story; what’s also needed is greater precision, more sensitive detectors that allow for more nuanced data, which reveals rare events or subtle effects not previously observed. To this end, the detectors have been upgraded too.

ATLAS, one of the four main experiments built around the 27km of the LHC complex, has gained the capacity to measure the paths of the charged particles produced in the collisions. This has improved the accuracy with which we can measure the lifetimes of these ephemeral particles that in some cases exist only for a tiny fraction of time.

Filter more noise

The experiments have also increased the rate and selectivity with which they record collisions in the LHC. As a great deal of subatomic particle physics is already known, the more unusual, exciting events are hidden within a huge torrent of data representing more mundane particle interactions. The sheer volume of raw data – about a petabyte, or around 210,000 DVDs per second – from the experiments requires algorithms to rapidly filter and select the new and unusual events for further study while discarding the rest.

Particle collissions in the LHC have taken us to the edge of physics.

Better selectivity is not the end of the problem, however. To cope with the volume of data produced by the experiments due to the more energetic collisions and more sensitive detectors means new software and storage procedures must be written. These will also transmit the data across the worldwide distributed computing system, which allows not just an accurate reconstruction of each collision from the traces recorded in the detectors, but also more rapid access for scientists to the records.

Unanswered questions

It’s a lot of hard work under tight budget constraints, but the effort is worth it. There are many open questions that the Standard Model simply cannot answer.

Is the recently discovered Higgs boson the particle the Standard Model predicts, or is it the first of a family of undiscovered, even more rare Higgs particles that are predicted by more complete but speculative theories such as Supersymmetry? What is the nature of the dark matter that astronomy tells us is far more abundant than the ordinary matter we’ve come to understand so well? How did a Big Bang that produced a balance of matter and antimatter result in the world of matter that we know today?

The Standard Model of quarks and other particles, including the Higgs boson.

My own principle interest in these questions is being addressed through studying the decays of particles containing quarks, the fundamental particles found inside the protons and neutrons that constitute an atomic nucleus. Of the six types of quarks it is the bottom quark (also known as the beauty quark) that is particularly interesting as the way it decays displays a small bias for matter over antimatter, but not enough so far to explain the world we know.

However, through an odd but well understood quirk of quantum mechanics, new and massive particles even bigger than we can produce in the LHC can affect these particles’ decays and leave a trail to the new physics we need to develop to better explain the universe. Some of these studies are already underway at dedicated experiments like LHCb, which has already proved several hypothesied supermassive particles within the Standard Model, but for others general purpose experiments like ATLAS can be better.

Unlike the first season of experiments with the LHC, once the first proton beam fires up on March 23 we will not have such a clear roadmap of what to expect, or what to aim for. The first run was led by the knowledge that we would either find the Higgs and add to the Standard Model, or not find it and break the Standard Model in an act of creative destruction pushing us on to find better theories.

This time, there is a clear programme of work around the Standard Model, including the Higgs, but we have many guides that point towards new physics. Most analyses will advance science through excluding possibilities, but the new discoveries will be all the more enlightening. In a sense, we have entered a mode of more pure scientific discovery – and I for one cannot wait.

The Conversation

This article was originally published on The Conversation.
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Could Dark Matter Be Behind Earth’s Extinction Events?

Earth’s orbit along the Galactic Disc, is a long yet predictable journey that lasts for eons, but not without consequence, as Michael Rampino, a professor of biology at New York University recently observed. Rampino’s newest research, published in the Monthly Notices of the Royal Astronomical Society, believes that these infrequent rotations have coincided with the state of life on Earth.

While we often think of the comet that brought a rather dramatic end to the dinosaurs 65 million years ago when we hear of extinction, it was hardly the first time that many species died out together. Nor was it even remotely the worst. That distinction belongs to the Permian-Triassic extinction event, which occurred 252 million years ago, coinciding with the Galactic Disc rotation, in which 83 percent of all life became extinct – owing to not only volcanic events but ocean acidification and the impact of several meteors. It took approximately 10 million years for much of the life left on Earth to replenish itself. While it took more than one event to make things hostile for life on Earth, Rampino has attributed the increased number of meteoric impacts to a buildup of dark matter, which may upset the orbits of comets and also increase heating at the Earth’s core – igniting volcanic activity, a trend currently being seen in Iceland.

Even the era that paleontologists purport to be the golden age of Dinosaurs – the Jurassic period – in which some of the largest species of sauropods thrived, was preceded by another violent extinction event – the Triassic-Jurassic extinction – taking place 201.3 million years ago. It took about 10,000 years, partially because of increased activity at a massive underwater volcano known as the Central Atlantic Magmatic Province, as well as several meteoric events which took place in Europe. Today, these periods are known by the rock layers they left behind, yet it is clear that each are caused by the same violent reactions in nature and the resulting change in climate.

The Galactic Disc is a region of the Milky Way Galaxy that defines its shape and contains our solar system, amidst a heavy clutter of stars and clouds of cosmic dust and reactive gasses. Yet, surrounding the cluster, is the elusive dark matter, particles which are primarily known because of the remarkable gravity they release, impervious to light and other forms of electromagnetic radiation.

According to prior studies, the Earth makes a rotation around the Galactic Disc once every 250 million years. However, the path is not always circular but wavy, as the Sun and other planets weave their way in and out of the crowded disc at intervals of approximately 30 million years or so. The Cretaceous-Paleocene event also coincides with these patterns.

So why does dark matter in particular seem like the culprit in these occurrences? When comets move through the disc, concentrations of dark matter can sometimes intensify to the point that they begin to throw comets off course, sometimes this instability causes them to collide with the planet, acts that have defined the shape of Earth throughout its history, and also perhaps supplying it with the very amino acids necessary to sustain life. But dark matter has another somewhat more pernicious impact on our planet in a different way, too.

As the Earth is exposed to dark matter on its rotations, Rampino learned that dark matter could essentially build up within the planetary core, producing an intense heat as its particles collide with each other inside. Eventually the heat builds up considerable pressure, leading to mountain building, volcanic eruptions, and even reversals in the planet’s magnetic field. The history of rises and falls in sea levels also shows a peak happening every 30 million years.

The new model of dark matter and its interactions with planets as they move across the Galaxy could significantly impact how we perceive geological and biological development. Already, our current understanding of the Earth’s natural history is one of violent and destructive events. Dark matter could be a critical cause behind it all. Already, in what geologists have petitioned to refer to as the Anthropocene Era (the Age of Humans – due to our species’ shaping of the planet for better or for worse), many other researchers believe we are in the midst of a sixth extinction event – with climbing levels of CO2 adding to the acidification of the ocean each year. Like dark matter, humans have the power to impact the universe too.

To put this all in perspective, Rampino said in his paper: “We are fortunate enough to live on a planet that is ideal for the development of complex life. But the history of Earth is punctuated by large scale extinction events, some of which we struggle to explain. It may be that dark matter — the nature of which is still unclear but which makes up around a quarter of the universe — holds the answer. As well as being important on the largest scales, dark matter may have a direct influence on life on Earth.”

James Sullivan
James Sullivan is the assistant editor of Brain World Magazine and a contributor to Truth Is Cool and OMNI Reboot. He can usually be found on TVTropes or RationalWiki when not exploiting life and science stories for another blog article.