Collider gets set to take on antimatter mystery

Image: Belle II detector
Scientists and technicians insert one of the optical components into the iTOP particle identification detector at the SuperKEKB accelerator in Japan. The “Imaging Time of Propagation” apparatus, or iTOP, is part of SuperKEKB’s Belle II detector. (Credit: PNNL)

What happened to all the antimatter? A particle-smasher in Japan is well on its way to addressing that question and others on the frontier of physics.

The SuperKEKB accelerator is designed to smash together tightly focused beams of electrons and anti-electrons (better known as positrons) and track the subatomic particles that wink in and out of existence as a result.

The collider will follow up on an earlier round of experiments at the KEK laboratory in Tsukuba. Over the past five years, KEK’s 1.9-mile-round (3-kilometer-round) underground ring has been upgraded to produce collisions at a rate 40 times higher than the earlier KEKB experiments did. Europe’s Large Hadron Collider may smash protons together at higher energies, but SuperKEKB will trump the LHC when it comes to the “Intensity Frontier.”

On Feb. 10, scientists circulated a beam of positrons around the SuperKEKB ring at nearly the speed of light. Then, on Feb. 26, they sent a separate beam of electrons at similar velocities, but going in the opposite direction. These “first turns” serve as major milestones on the way to next year’s first physics run, when both beams will circulate simultaneously and smash into each other in SuperKEKB’s upgraded Belle II detector.

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LHC readings intrigue physicists: Stay tuned

Image: Diphoton excess
A computer graphic shows the spray of particles created by a proton collision in the Large Hadron Collider’s CMS detector. The two green lines indicate the emission of two photons. Physicists say that could be part of an intriguing pattern, or merely a coincidence. (Thomas McCauley / CERN / CMS)

The Higgs boson is the biggest find of the century in particle physics, but for the past few weeks, physicists at the Large Hadron Collider have been considering whether there’s a mystery that’s even bigger. Or at least more massive.

The potential mystery has to do with a pattern of particle decay that results in the emission of two photons. The readings collected so far by the teams using the ATLAS and CMS detectors point to a slight “bump” in the expected pattern.

That may hint at the existence of a previously undetected particle with a mass of about 750 billion electron volts – six times heavier than the Higgs, French physicist Adam Falkowski (a.k.a. Jester) writes in his Resonaances blog.

Could it be a second Higgs boson? Evidence for gravitons or extra dimensions? Ever since the findings were made public three weeks ago, theories have been flying around like speeding muons, and with good reason. “If the diphoton excess is really a new particle, we are basically guaranteed to find other phenomena beyond the Standard Model,” Falkowski says.

However, the two-photon excess may be merely a coincidence – the sort of pattern that pops up in an early stage of data collection, but fades away when more readings are factored into the findings.

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LHC milestone re-ignites doomsday talk

Image: ALICE collision
This computer graphic shows one of the first collisions recorded between two lead ions at the Large Hadron Collider’s top energy. The energy in the center-of-mass system is approximately a quadrillion electron-volts. (Credit: CERN / ALICE Collaboration)

The Large Hadron Collider set another record for particle-smashing energy levels this week – which set off another round of hyped-up rumblings about the end of the world.

Before the LHC’s startup in 2008, the Internet was set abuzz with worries that high-energy collisions could create globe-gobbling black holes or cosmos-wrecking strangelets. Protests were mounted, lawsuits were filed, and physicists at Europe’s CERN particle physics center had to explain in depth why the nightmare scenarios were nothing more than nightmares. Once the collider went into operation, the lawsuits were dismissed and the hand-wringing settled down.

Now the world’s largest collider is operating at near its design limits, and this week, CERN reported that lead-ion collisions in the LHC’s ALICE detectorreached energies beyond a quadrillion electron-volts – a level also known as 1 peta-electron-volt, or 1 PeV.

“This energy is that of a bumblebee hitting us on the cheek on a summer day. But the energy is concentrated in a volume that is approximately 10 -27 (a billion-billion-billion) times smaller,” Jens Jørgen Gaardhøje, professor at the Niels Bohr Institute at the University of Copenhagen and head of the Danish research group within the ALICE experiment, said in a news release.

At first blush, a quadrillion electron-volts sounds like a huge ramp-up from 13 trillion to 14 trillion electron-volts, or 13 to 14 TeV, the traditionally quoted figures for the high end of the LHC’s collision energy. That’s what set off the doomsayers. In the weeks leading up to the ALICE collisions, there was a drumbeat of postings claiming that “CERN LIED” and warning that 1-PeV smashups would have catastrophic consequences.

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