Professor , a particle physicist in the Faculty of Science & Engineering, who joined the faculty this past summer, and graduate student Hiro Sato are co-authors with Andrea De Simone, PhD candidate at the Center for Theoretical Physics, Massachusetts Institute of Technology, in Cambridge, Mass. of a paper published in the American Physical Society’s Physical Review Letters, one of the world's foremost scientific journals.

Above: Veronica Sanz, professor of particle physics in 91ŃÇÉ«'s Faculty of Science & Engineering, with graduate student Hiro Sato

The article, “Pseudo-Dirac Dark Matter Leaves a Trace”, suggests a method for detecting traces of a dark matter particle that are produced in a collider. Normally, dark matter can only be detected by inference – by “not seeing” it in experiments designed to observe the missing energy that was carried away by the dark matter particle. The method described in the paper would allow experimentalists to see evidence of dark matter, thought to make up 23 per cent of the observable universe, for the first time.

“Everybody wants to get this piece of the cake, they want to explain this 23-per-cent part of the universe,” says Sanz, who began her studies of dark matter during graduate studies at Harvard University and MIT, and continued them in her post-doctoral research at Boston University.

Dark matter was first postulated by Swiss astronomer Fritz Zwicky in 1934 to help explain anomalies in the orbital velocities of galaxies in clusters.

What led Sanz to the idea that she and her co-authors have described was a growing lack of confidence in WIMPS.

No, not weaklings on the beach – these WIMPS are the hypothetical “weakly interacting massive particles” that represent one theory about dark matter. In a technique used by the cryogenic dark matter search (CDMS) detector at Minnesota’s Soudan Underground Laboratory, scientists thought they would be able to detect dark matter, but found nothing.

“This is very worrisome,” says Sanz, “because our WIMP idea of dark matter doesn’t explain why CDMS didn’t see anything. So, we sat down and tried to think of another way of leading to dark matter.”

Experimentalists will now test the 91ŃÇÉ« team’s theory in a collider by smashing protons and watching for the observable remnants. “We are asking them to look at particles displaced from the collision point. This is not what they were going to do, they were going to look for [evidence of ] nothing.”

These questions are the subject of a larger debate about the fundamental concept of gravity and the make-up of the universe, says Sato, a master’s student who came to 91ŃÇÉ« from the University of Toronto so he could work on dark matter with Sanz.

“People thought maybe something’s wrong with gravity theory – that there’s some fundamental problem with how Einstein or Newton thought about what gravity was. The other way of thinking about it is, no, there is matter, it’s just invisible. There’s nothing wrong with our gravity theory, it’s actually some kind of matter.”

“Pseudo-Dirac Dark Matter Leaves a Trace” was published in the Sept. 16 edition of the Letters and is available as a at the website for those with access, which is included on many 91ŃÇÉ« computers via 91ŃÇÉ« Libraries.

By David Fuller, YFile contributing writer

Republished courtesy of YFile– 91ŃÇɫ’s daily e-bulletin

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91ŃÇÉ« particle physicist Sampa Bhadra (below right) has already figured out how she intends to spend her next sabbatical leave when it comes in 2013 – she's hoping to visit British Columbia so she can spend some quality time at a subatomic research facility that’s larger than two city blocks and houses the biggest cyclotron in the world. It will be the ultimate busman’s holiday as she takes part in research into the tiniest secrets of the universe along with scientific colleagues at TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics.

While there, Bhadra, a professor in 91ŃÇɫ’s Faculty of Science & Engineering, will also visit with 91ŃÇÉ« alumnus Nigel Lockyer (BSc Spec. Hons. ’75), director of TRIUMF, in which 91ŃÇÉ« became a partner July 1 (see YFile, July 2). The two met 22 years ago at another subatomic research facility, Fermilab, near Chicago, and established a networking connection that made 91ŃÇɫ’s eventual partnership in TRIUMF possible.

When Lockyer became director in 2007 (see YFile, March 20, 2007), he accepted an invitation from then president Lorna Marsden to visit 91ŃÇÉ«'s Keele campus and meet the University’s growing team of particle physicists. When he arrived, Lockyer was in the early stages of a campaign to promote membership in TRIUMF to Canadian universities. He quickly recruited Bhadra to champion the idea at 91ŃÇÉ«, along with Stan Shapson, 91ŃÇɫ’s vice-president research & innovation, and Michael Siu, associate vice-president research, science & technology, and she is now 91ŃÇɫ’s representative on TRIUMF’s Policy & Planning Advisory Committee. 91ŃÇÉ« became an associate member of the consortium in September 2008 (see YFile, Sept. 16, 2008).

Taylor	Menary

The Faculty of Science & Engineering has seven researchers, members of 91ŃÇɫ’s group, who will benefit from the association with TRIUMF, says Bhadra. She and fellow experimentalists Scott Menary and Wendy Taylor are the 91ŃÇÉ« principal investigators for several projects around the world and the Canadian leaders of these experiments reside at TRIUMF.

91ŃÇÉ« theorists Roman Koniuk, Randy Lewis and Kim Maltman have also collaborated closely with TRIUMF physicists, either as staff and/or on sabbatical. The newest member of 91ŃÇɫ’s particle physics group is theorist Veronica Sanz-Gonzalez, who joined 91ŃÇÉ« this year from Boston University.

Koniuk	Lewis	Maltman	Sanz-Gonzalez

“Our connection to TRIUMF is long overdue,” says Bhadra. “It’s a great meeting place for scientific discussions; it’s a concentration of experts. The synergy is fantastic right now.”

The benefits of 91ŃÇɫ’s membership will soon be felt at the Keele campus when Lia Merminga, director of TRIUMF’s accelerator division, makes a visit to 91ŃÇÉ« in November. “91ŃÇÉ« and TRIUMF will be exploring joint intitiatives that will have long-reaching benefits for both institutions,” says Bhadra.

TRIUMF “is a value statement by Canada about the long-term importance of strategic investments in science, technology and innovation,” said Lockyer in a director’s message. “TRIUMF’s accomplishments in basic research (particle and nuclear physics, molecular and materials science, nuclear medicine and information technology), international partnerships and commercial successes with Canadian companies are the proof behind this statement.”

Right: Nigel Lockyer

TRIUMF’s Isotope Separator and Accelerator Complex is recognized as the world’s most advanced laboratory for the production of exotic or “medical” isotopes. While not using the accelerator complex itself, Bhadra and her colleagues have access to the excellent resources provided by TRIUMF in terms of expertise in electronics, computing and engineering support.

TRIUMF's accelerator division has long been recognized as one of the world's best and has contributed hardware and expertise to CERN, the international consortium based in Switzerland that is home to the world's largest particle accelerator.

For more information about TRIUMF, visit its Web site.

Republished with files courtesy of YFile – 91ŃÇɫ’s daily e-bulletin.

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