The Holy Grail of high-energy physics — the predicted but elusive Higgs boson — is almost within reach, and the Brandeis high-energy physics group, along with other particle physicists around the world collaborating on making the finding, is almost giddy with excitement.
The Brandeis group has contributed since 1994 to collaborative experiments to detect the Higgs particle in the world’s largest particle accelerator, the Large Hadron Collider (LHC). CERN, the international agency in Geneva that oversees experiments in the LHC, announced Dec. 13 in a progress report the news of mounting experimental evidence for the existence of this critically important speck of nature.
“It’s very exciting,” says Brandeis physics Professor Craig Blocker, explaining that experiments in the LHC’s two detectors have amassed enough evidence of the Higgs particle to suggest much more than an unexplained blip in the data produced by trillions of protons smashing into each other at almost the speed of light.
“The data look very tantalizing but we’re not there yet,” says Blocker. “We don’t have quite enough evidence to claim a discovery but it looks promising — there’s a good indication that this particle is there, so we’ll probably be able to announce the discovery next year with more data.”
What makes the prospect of finding the Higgs particle so electrifying for physicists is that its discovery could put in place the final piece of the puzzle that describes the fundamental building blocks of matter and their interactions — hence its description as the “God Particle.” Higgs particles are thought to interact with other subatomic particles to give them mass through a phenomenon known as the Higgs mechanism.
The Higgs mechanism was first described in the 1960s by Scottish physicist Peter Higgs. A few years later, physicist Steven Weinberg applied Higgs’ ideas to weak interactions and predicted the Higgs particle. It is the only elementary particle in the Standard Model — the description of the fundamental particles and the forces that hold them together — that has not been observed experimentally yet.
Blocker says detecting the Higgs is challenging because the strength with which it interacts with other particles depends on the mass of those other particles. The Higgs itself is quite massive (for something on the subatomic level); it interacts well with other massive particles, but very poorly with lightweight particles. However, massive particles generally require higher-energy conditions than lightweight particles to record experimentally — energy levels difficult to obtain even inside the mind-boggling fast Large Hadron Collider. Consequently, says Blocker, physicists don’t obtain the signature energy decay of a Higgs boson often in the supercollider.
The growing anticipation surrounding the Higgs particle seems almost overshadowed by a gathering anxiety that physicists might actually get what they wish for — a perfectly realized prediction that completes the Standard Model. If that happens says Blocker, “we’d be unhappy — the quest is what’s interesting.”
Higgs or no Higgs, the chances of particle physicists actually arriving at what Einstein called a “theory of everything” anytime soon seem infinitesimally remote. When it comes to particle physics, says Blocker, it is much more likely that new theories will be generated with each experimental advance

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Physicists say they are near epic Higgs boson discovery

MIT researchers have created a new imaging system that can acquire visual data at a rate of one trillion exposures per second. That’s fast enough to produce a slow-motion video of a burst of light traveling the length of a one-liter bottle, bouncing off the cap and reflecting back to the bottle’s bottom.
Media Lab postdoc Andreas Velten, one of the system’s developers, calls it the “ultimate” in slow motion: “There’s nothing in the universe that looks fast to this camera,” he says.
The system relies on a recent technology called a streak camera, deployed in a totally unexpected way. The aperture of the streak camera is a narrow slit. Particles of light — photons — enter the camera through the slit and pass through an electric field that deflects them in a direction perpendicular to the slit. Because the electric field is changing very rapidly, it deflects late-arriving photons more than it does early-arriving ones.
The image produced by the camera is thus two-dimensional, but only one of the dimensions — the one corresponding to the direction of the slit — is spatial. The other dimension, corresponding to the degree of deflection, is time. The image thus represents the time of arrival of photons passing through a one-dimensional slice of space.
The camera was intended for use in experiments where light passes through or is emitted by a chemical sample. Since chemists are chiefly interested in the wavelengths of light that a sample absorbs, or in how the intensity of the emitted light changes over time, the fact that the camera registers only one spatial dimension is irrelevant.
But it’s a serious drawback in a video camera. To produce their super-slow-mo videos, Velten, Media Lab Associate Professor Ramesh Raskar and Moungi Bawendi, the Lester Wolfe Professor of Chemistry, must perform the same experiment — such as passing a light pulse through a bottle — over and over, continually repositioning the streak camera to gradually build up a two-dimensional image. Synchronizing the camera and the laser that generates the pulse, so that the timing of every exposure is the same, requires a battery of sophisticated optical equipment and exquisite mechanical control. It takes only a nanosecond — a billionth of a second — for light to scatter through a bottle, but it takes about an hour to collect all the data necessary for the final video. For that reason, Raskar calls the new system “the world’s slowest fastest camera.”
Doing the math
After an hour, the researchers accumulate hundreds of thousands of data sets, each of which plots the one-dimensional positions of photons against their times of arrival. Raskar, Velten and other members of Raskar’s Camera Culture group at the Media Lab developed algorithms that can stitch that raw data into a set of sequential two-dimensional images.
The streak camera and the laser that generates the light pulses — both cutting-edge devices with a cumulative price tag of $250,000 — were provided by Bawendi, a pioneer in research on quantum dots: tiny, light-emitting clusters of semiconductor particles that have potential applications in quantum computing, video-display technology, biological imaging, solar cells and a host of other areas.
The trillion-frame-per-second imaging system, which the researchers have presented both at the Optical Society’s Computational Optical Sensing and Imaging conference and at Siggraph, is a spinoff of another Camera Culture project, a camera that can see around corners. That camera works by bouncing light off a reflective surface — say, the wall opposite a doorway — and measuring the time it takes different photons to return. But while both systems use ultrashort bursts of laser light and streak cameras, the arrangement of their other optical components and their reconstruction algorithms are tailored to their disparate tasks.
Because the ultrafast-imaging system requires multiple passes to produce its videos, it can’t record events that aren’t exactly repeatable. Any practical applications will probably involve cases where the way in which light scatters — or bounces around as it strikes different surfaces — is itself a source of useful information. Those cases may, however, include analyses of the physical structure of both manufactured materials and biological tissues — “like ultrasound with light,” as Raskar puts it.
As a longtime camera researcher, Raskar also sees a potential application in the development of better camera flashes. “An ultimate dream is, how do you create studio-like lighting from a compact flash? How can I take a portable camera that has a tiny flash and create the illusion that I have all these umbrellas, and sport lights, and so on?” asks Raskar, the NEC Career Development Associate Professor of Media Arts and Sciences. “With our ultrafast imaging, we can actually analyze how the photons are traveling through the world. And then we can recreate a new photo by creating the illusion that the photons started somewhere else.”
“It’s very interesting work. I am very impressed,” says Nils Abramson, a professor of applied holography at Sweden’s Royal Institute of Technology. In the late 1970s, Abramson pioneered a technique called light-in-flight holography, which ultimately proved able to capture images of light waves at a rate of 100 billion frames per second.
But as Abramson points out, his technique requires so-called coherent light, meaning that the troughs and crests of the light waves that produce the image have to line up with each other. “If you happen to destroy the coherence when the light is passing through different objects, then it doesn’t work,” Abramson says. “So I think it’s much better if you can use ordinary light, which Ramesh does.”
Indeed, Velten says, “As photons bounce around in the scene or inside objects, they lose coherence. Only an incoherent detection method like ours can see those photons.” And those photons, Velten says, could let researchers “learn more about the material properties of the objects, about what is under their surface and about the layout of the scene. Because we can see those photons, we could use them to look inside objects — for example, for medical imaging, or to identify materials.”
“I’m surprised that the method I’ve been using has not been more popular,” Abramson adds. “I’ve felt rather alone. I’m very glad that someone else is doing something similar. Because I think there are many interesting things to find when you can do this sort of study of the light itself.”

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Trillion-frame-per-second video: Researchers have created an imaging system that makes light look slow