Tag Archives: Higgs

CDM: Cosmic Discovery Machine

We think CDM sounds much more fun than LHC, a rather dry acronym for Large Hadron Collider.

Researchers at the LHC are set to announce the latest findings in early July from the record-breaking particle smasher buried below the French and Swiss borders. Rumors point towards the discovery of the so-called Higgs boson, the particle theorized to give mass to all the other fundamental building blocks of matter. So, while this would be another exciting discovery from CERN and yet another confirmation of the fundamental and elegant Standard Model of particle physics, perhaps there is yet more to uncover, such as the exotically named “inflaton”.

[div class=attrib]From Scientific American:[end-div]

Within a sliver of a second after it was born, our universe expanded staggeringly in size, by a factor of at least 10^26. That’s what most cosmologists maintain, although it remains a mystery as to what might have begun and ended this wild expansion. Now scientists are increasingly wondering if the most powerful particle collider in history, the Large Hadron Collider (LHC) in Europe, could shed light on this mysterious growth, called inflation, by catching a glimpse of the particle behind it. It could be that the main target of the collider’s current experiments, the Higgs boson, which is thought to endow all matter with mass, could also be this inflationary agent.

During inflation, spacetime is thought to have swelled in volume at an accelerating rate, from about a quadrillionth the size of an atom to the size of a dime. This rapid expansion would help explain why the cosmos today is as extraordinarily uniform as it is, with only very tiny variations in the distribution of matter and energy. The expansion would also help explain why the universe on a large scale appears geometrically flat, meaning that the fabric of space is not curved in a way that bends the paths of light beams and objects traveling within it.

The particle or field behind inflation, referred to as the “inflaton,” is thought to possess a very unusual property: it generates a repulsive gravitational field. To cause space to inflate as profoundly and temporarily as it did, the field’s energy throughout space must have varied in strength over time, from very high to very low, with inflation ending once the energy sunk low enough, according to theoretical physicists.

Much remains unknown about inflation, and some prominent critics of the idea wonder if it happened at all. Scientists have looked at the cosmic microwave background radiation—the afterglow of the big bang—to rule out some inflationary scenarios. “But it cannot tell us much about the nature of the inflaton itself,” says particle cosmologist Anupam Mazumdar at Lancaster University in England, such as its mass or the specific ways it might interact with other particles.

A number of research teams have suggested competing ideas about how the LHC might discover the inflaton. Skeptics think it highly unlikely that any earthly particle collider could shed light on inflation, because the uppermost energy densities one could imagine with inflation would be about 10^50 times above the LHC’s capabilities. However, because inflation varied with strength over time, scientists have argued the LHC may have at least enough energy to re-create inflation’s final stages.

It could be that the principal particle ongoing collider runs aim to detect, the Higgs boson, could also underlie inflation.

“The idea of the Higgs driving inflation can only take place if the Higgs’s mass lies within a particular interval, the kind which the LHC can see,” says theoretical physicist Mikhail Shaposhnikov at the École Polytechnique Fédérale de Lausanne in Switzerland. Indeed, evidence of the Higgs boson was reported at the LHC in December at a mass of about 125 billion electron volts, roughly the mass of 125 hydrogen atoms.

Also intriguing: the Higgs as well as the inflaton are thought to have varied with strength over time. In fact, the inventor of inflation theory, cosmologist Alan Guth at the Massachusetts Institute of Technology, originally assumed inflation was driven by the Higgs field of a conjectured grand unified theory.

[div class=attrib]Read the entire article after the jump.[end-div]

[div class=attrib]Image courtesy of Physics World.[end-div]

Higgs Particle Collides with Modern Art

Jonathan Jones over at the Guardian puts an creative spin (pun intended) on the latest developments in the world of particle physics. He suggests that we might borrow from the world of modern and contemporary art to help us take the vast imaginative leaps necessary to understand our physical world and its underlying quantum mechanical nature bound up in uncertainty and paradox.

Jones makes a good point that many leading artists of recent times broke new ground by presenting us with an alternate reality that demanded a fresh perspective of the world and what lies beneath. Think Picasso and Dali and Miro and Twombly.

[div class=attrib]From Jonathan Jones for the Guardian:[end-div]

The experiments currently being performed in the LHC are enigmatic, mind-boggling and imaginative. But are they science – or art? In his renowned television series The Ascent of Man, the polymath Jacob Bronowski called the discovery of the invisible world within the atom the great collective achievement of science in the 20th century. Then he went further. “No – it is a great, collective work of art.”

Niels Bohr, who was at the heart of the new sub-atomic physics in the early 20th century, put the mystery of what he and others were finding into provocative sayings. He was very quotable, and every quote stresses the ambiguity of the new realm he was opening up, the realm of the smallest conceivable things in the universe. “If quantum mechanics hasn’t profoundly shocked you, you haven’t understood it yet,” ran one of his remarks. According to Bronowski, Bohr also said that to think about the paradoxical truths of quantum mechanics is to think in images, because the only way to know anything about the invisible is to create an image of it that is by definition a human construct, a model, a half-truth trying to hint at the real truth.

. . .

We won’t understand what those guys at Cern are up to until our idea of science catches up with the greatest minds of the 20th century who blew apart all previous conventions of thought. One guide offers itself to those of us who are not physicists: modern art. Bohr, explained Bronowski, collected Cubist paintings. Cubism was invented by Pablo Picasso and Georges Braque at the same time modern physics was being created: its crystalline structures and opaque surfaces suggest the astonishment of a reality whose every microcosmic particle is sublimely complex.

[div class=attrib]More from theSource here.[end-div]

[div class=attrib]Image courtesy of Wikipedia / CERN / Creative Commons.[end-div]

Tour de France and the Higgs Particle

Two exciting races tracked through Grenoble, France this passed week. First, the Tour de France held one of the definitive stages of the 2011 race in Grenoble, the individual time trial. Second, Grenoble hosted the European Physical Society conference on High-Energy Physics. Fans of professional cycling and high energy physics would not be disappointed.

In cycling, Cadel Evans set a blistering pace in his solo effort on stage 20 to ensure the Yellow Jersey and an overall win in this year’s Tour.

In the world of high energy physics, physicists from Fermilab and CERN presented updates on their competing searches to discover (or not) the Higgs boson. The two main experiments at Fermilab, CDF and DZero, are looking for traces of the Higgs particle in the debris of Tevatron collider’s proton-antiproton collisions. At CERN’s Large Hadron Collider scientists working at the two massive detectors, Atlas and CMS, are sifting through vast mountains of data accumulated from proton-proton collisions.

Both colliders have been smashing particles together in their ongoing quest to refine our understanding of the building blocks of matter, and to determine the existence of the Higgs particle. The Higgs is believed to convey mass to other particles, and remains one of the remaining undiscovered components of the Standard Model of physics.

The latest results presented in Grenoble show excess particle events, above a chance distribution, across the search range where the Higgs particle is predicted to be found. There is a surplus of unusual events at a mass of 140-145 GeV (gigaelectronvolts), which is at the low end of the range allowed for the particle. Tantalizingly, physicists’ theories predict that this is the most likely region where the Higgs is to be found.

[div class=attrib]Further details from Symmetry Breaking:[end-div]

Physicists could be on their way to discovering the Higgs boson, if it exists, by next year. Scientists in two experiments at the Large Hadron Collider pleasantly surprised attendees at the European Physical Society conference this afternoon by both showing small hints of what could be the prized particle in the same area.

“This is what we expect to find on the road to the Higgs,” said Gigi Rolandi, physics coordinator for the CMS experiment.

Both experiments found excesses in the 130-150 GeV mass region. But the excesses did not have enough statistical significance to count as evidence of the Higgs.

If the Higgs really is lurking in this region, it is still in reach of experiments at Fermilab’s Tevatron. Although the accelerator will shut down for good at the end of September, Fermilab’s CDF and DZero experiments will continue to collect data up until that point and to improve their analyses.

“This should give us the sensitivity to make a new statement about the 114-180 mass range,” said Rob Roser, CDF spokesperson. Read more about the differences between Higgs searches at the Tevatron and at the LHC here.

The CDF and DZero experiments announced expanded exclusions in the search for their specialty, the low-mass Higgs, this morning. On Wednesday, the two experiments will announce their combined Higgs results.

Scientists measure statistical significance in units called sigma, written as the Greek letter ?. These high-energy experiments usually require 3?  level of confidence, about 99.7 percent certainty, to claim they’ve seen evidence of something. They need 5? to claim a discovery. The ATLAS experiment reported excesses at confidence levels between 2 and 2.8?, and the CMS experiment found similar excesses at close to 3?.

After the two experiments combine their results — a mathematical process much more arduous than simple addition — they could find themselves on new ground. They hope to do this in the next few months, at the latest by the winter conferences, said Kyle Cranmer, an assistant professor at New York University who presented the results for the ATLAS collaboration.

“The fact that these two experiments with different issues, different approaches and different modeling found similar results leads you to believe it might not be just a fluke,” Cranmer said. “This is what it would look like if it were real.”

[div class=attrib]More from theSource here.[end-div]

[div class=attrib]CERN photograph courtesy Fabrice Coffrini/AFP/Getty Images. Tour de France image courtesy of NBCSports.[end-div]