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UW aids in the global hunt for the Higgs boson

Henry Lubatti

Henry Lubatti -

Physics professor Henry Lubatti stands in front of a diagram explaining the “valleys” between which the Higgs particles can travel.

Photo by Joshua Bessex

What's a Higgs boson

What's a Higgs boson

Gordon Watts

Gordon Watts

For particle physicists, discovering the secret of the universe means going on a never-ending quest.

When UW physicists gathered at a bar in Queen Anne on July 4, 2012, they saw the result of more than 20 years of hard work: evidence of the Higgs boson, a particle famously predicted to be a key element to understanding the mechanism of the universe. The principle source of every object’s mass, the Higgs field, is comprised of an unfathomable number of these infamous particles.

Physicists at CERN, the European Council for Nuclear Research, tentatively confirmed March 14 that the widely-celebrated particle discovered last summer is indeed the Higgs boson. For UW researchers, this confirmation only meant more secrets to unlock.

“One of the beauties about this field … is you answer one question and [it] brings up another five or six,” said Gordon Watts, physics professor and one of the UW researchers involved in making the discovery last summer.

The new question in this case, what the Higgs boson means to the universe, may be answered by observing the particle’s properties such as its spin or decay channels: various probabilities of ways that massive unstable particles such as the Higgs can decay, usually into lighter particles.

The Higgs boson, which British theoretical physicist Peter Higgs and his colleagues predicted in 1964, is central to the understanding of the Standard Model, the reigning (though incomplete) theory in physics that explains how the universe works at the smallest dimensions. The discovery confirms the Higgs Field, a theoretical invisible field of energy that gives mass into elementary particles using the Higgs particle.

“From the point of view of understanding how the universe works … how is it that the universe got to where it is now, this [discovery] is one of the major pieces,” Watts said.

Physicists around the world are currently gathering data to examine whether the discovered particle is the Standard Model Higgs boson or if it is one of a whole other set of Higgs bosons, as is predicted by unverified physical theories that attempt to explain more of the fundamental aspects of the structure of the universe.

Since last summer, the UW team has moved on to research beyond the Higgs particle discovery to solve the new puzzles.

Anna Goussiou, UW physics professor and researcher, has set forth to verify whether or not the discovered Higgs boson is that of a Standard Model by searching for and examining a specific decay channel of the Higgs boson. Her team is also looking for evidence of physics beyond the Standard Model by searching specifically for other Higgs bosons predicted by Supersymmetry, an extension theory from the Standard Model that can not only resolve the shortcomings of the Standard Model but also provide a candidate particle for Dark Matter.

“The Higgs makes the Standard Model complete, but almost all of us believe that the Standard Model is not all that there is, because there are unanswered questions,” Goussiou said.

Watts, alongside Henry Lubatti, UW physics professor and researcher, is looking for evidence of physics beyond the Standard Model by searching for hidden sectors, a collection of yet-unobserved quantum fields and the corresponding hypothetical particles that do not interact through gauge boson forces of the Standard Model ­— a force-carrier particle that carries fundamental interactions of nature such as gravity and electromagnetism. According to Lubatti, the Higgs boson can be a doorway to finding these hidden sectors.

“[What] Gordon and I are doing is saying, ‘OK, we believe that the Higgs is there, but now we know that the Higgs model is incomplete,’” Lubatti said. “So we know that there’s got to be some new physics, this is not the end of the story, there’s some new physics somewhere — the question is, where is it? One possibility is that there are hidden sectors.”

Despite the new directions in which their research has gone, the researchers are still excited about the discovery of the Higgs boson itself. For more than 20 years, the UW team worked on A Toroidal LHC Apparatus (ATLAS), one of the two particle-detector experiments constructed at CERN’s Large Hadron Collider (LHC) that specifically investigates the Higgs. The ATLAS detector comprises various systems. The UW team played an important role in designing and building the Muon Spectrometer, one of the systems central to the Higgs boson discovery.

The LHC, located outside of Geneva, Switzerland, is now down for two years of repairs. The researchers have compiled their own to-do lists for when the LHC reopens in 2015, and all are looking forward to uncovering more secrets of the universe.

“I would expect that there would be more surprises,” Lubatti said. “I wish I knew what they would be because then I could go right there and look for them, but that’s one of the fun parts of doing this; you don’t know, and you go look.”

 

Reach reporter Imana Gunawan at science@dailyuw.com. Twitter: @imanafg

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