Hiding in the Higgs data: hints of physics beyond the standard model

The good folks at the LHC have not been shy about sharing their results. Indeed, at the end of last year, the bigwigs at CERN called a press conference to announce that they hadn't found the Higgs boson yet, but they were starting to see some signals that might be the Higgs. If only all of us in research could get away with progress reports like that.

OK, that was a very cynical opening to a story that shows the benefits of such openness. The signal seen by the LHC's CMS and ATLAS detectors hinted at a Higgs Boson with a mass in the range of 124-126GeV. But buried in the details are some numbers that, if they hold up, will be impossible to accommodate in the standard model of physics. What does any good theoretical physicist do in these circumstances? Plug the numbers into their favorite model to see if it is still in the running. Something that could not be done had CERN not been so open about its preliminary results.

Read the comments on this post

New detector weighs in: neutrinos don’t exceed light speed

We now have yet another indication that neutrinos cannot travel faster than the speed of light after all, provided by a neighbor of the OPERA detector that set off the fuss in the first place. OPERA's detector sits deep underground at Gran Sasso in Italy, where it receives neutrinos from a beam generated at CERN, 730km away on the French-Swiss border. Because the neutrino beam spreads out over the intervening distance, it's possible to run multiple detectors at the same site, all listening in on the same beam. The team running one of Gran Sasso's other detectors (called ICARUS) has now performed time-of-flight measurements on neutrinos and determined that they don't seem to be moving faster than light.

These results are significant because they largely took advantage of precisely the same infrastructure used to generate the OPERA results. ICARUS used the short, widely spaced bunches of neutrinos produced by CERN to help narrow down potential errors in the earlier results (read our discussion of these errors). The ICARUS team also used the same timing and position infrastructure used by OPERA, which gives them uncertainties of only nanoseconds and centimeters, respectively. WIth all that in place, the ICARUS team captured data from the arrival of seven neutrinos.

With just about everything but the detector itself identical between the two tests, the ICARUS team concluded, "The result is compatible with the simultaneous arrival of all events with equal speed, the one of light." (Neutrinos have such a small mass that it's relatively easy to accelerate them to a speed that is only marginally slower than light.)

One difference between the two detectors is the technology used to detect the arrival of neutrinos—OPERA uses a photographic emulsion, while ICARUS uses liquid argon. It's possible that this difference may provide an indication of why the results differed.

Read the comments on this post

Neutrinos shot through 780 feet of stone, spell out their name

A group of researchers communicated a message through 780 feet of solid stone using a beam of neutrinos, the University of Rochester announced Wednesday. When the message came out the other side, the scientists were able to read it perfectly: it said, perhaps unimaginatively, "Neutrino."

Neutrinos are nearly massless and travel very close to the speed of light. Because they only interact with matter via gravity and the weak force, they can pass through substances, including entire planets, with little disruption. Scientists have talked about using the particles as a messaging alternative to cables or satellites, sending messages to the other side of the earth by going through the earth, rather than going around the long way or sending messages into space and back again.

The equipment to send neutrino messages is still wildly expensive. The researchers who sent the "Neutrino" message used a particle accelerator at Fermilab with a 2.5-mile-circumference track and the 5-ton particle detector named MINERvA. To signal the message, the scientists used binary code, with a group of neutrinos fired corresponding to a 1 and no neutrinos fired corresponding to a 0. Even MINERvA can only detect about one in 10 billion neutrinos, so the particles had to be fired in very large numbers to register.

Because the equipment is so expensive, actual communication with neutrinos is still a long way off. Still, the authors note that the particles are barely affected by gravity and not affected at all by magnetism; eventually, they could provide a stable alternative to the electromagnetic waves we use now.

Read the comments on this post

Updates from the LHC and Tevatron keep the door open for the Higgs

We're only about a week away from restarting the LHC, but the physics community is still analyzing data generated by earlier runs of that collider and the Tevatron. Their latest results were presented at a physics meeting in Italy this week. The biggest news is probably the fact that the full analysis of Tevatron data turns out to be consistent with the presence of the Higgs where early indications from the LHC say it's likely to be. The LHC data, however, shows a slightly reduced signal, and the two detectors are still placing it at slightly different masses.

Read the comments on this post

High-precision weigh-in for W boson means fewer hiding places for Higgs

Fermilab's Tevatron particle collider may have shut down last year, but it left behind massive amounts of data for scientists to sift through—physicists I've talked to suggest that papers should keep flowing at the same pace as when it was running for well over a year. Thursday, the CDF detector team released a new estimate of the mass of the W boson, derived from Tevatron data, that provides the most precise value for this particle yet. Thanks to relationships among the particles of the Standard Model, this also places a limit on the mass of the Higgs boson, a limit that's consistent with the data coming out of the LHC.

The W boson helps mediate the weak nuclear force, which drives radioactive decays. It was first detected back in the 1980s at CERN's SPS accelerator, which now forms part of the accelerator chain that feeds the LHC. Since then, various accelerators have produced enough Ws to provide an estimate of its mass, with all of them placing it at just above 80GeV, at an error range of about 100MeV. The new estimate from Fermi's CDF detector provides the smallest error bars yet, and places it at 80.387GeV, ±0.02. That's within the error bars of all previous measurements but one (the odd one out was the LEP's L3 detector).

Read the comments on this post

Faster-than-light neutrino result reportedly a mistake caused by loose cable – UPDATED

Since September, scientists have been scratching their head over results that appear to show neutrinos traveling between Switzerland and Italy faster than light would. As far as anyone could tell, the team behind the results had done everything they could to eliminate errors, and had even released some preliminary data that had strengthened their results. But the results remained difficult to square with everything else we know about how the Universe operates.

But now, ScienceInsider is reporting that there was a good reason the measurements and reality weren't lining up: a loose fiber optic cable was causing one of the atomic clocks used to time the neutrinos' flight to produce spurious results. If the report is confirmed (right now, there's only one source), then it provides a simple explanation for the fascinating-yet-difficult-to-accept results. According to the new report, researchers are preparing to gather new data with the clocks properly hooked into computers, which should definitively indicate whether the loose connection was at fault.

It's somewhat ironic that ScienceInsider, which is part of the American Association for the Advancement of Science, broke the news now. Over the weekend, the AAAS held its annual meeting, which included a discussion of the biggest news in physics, where the neutrino results were highlighted. The session indicated that five different neutrino experiments were upgrading their hardware in order to check timing, and some would have data before the year is out. So even if this report doesn't pan out, we should know more soon.

At the AAAS meeting's discussion, CERN's director of research, Sergio Bertolucci, placed his bet on what the results would be: "I have difficulty to believe it, because nothing in Italy arrives ahead of time."

UPDATE: Nature News has apparently received a statement from the Opera researchers. It indicates they have found two potential issues (one of them the optical cabling). The two issues would skew the results in opposite directions, which is why they will need new measurements to better understand whether both influence the results and, if so, what the net impact is.

Read the comments on this post

LHC set to up collision rate, energy in attempt to pin down Higgs boson

Last week, the people running the LHC laid out plans for its 2012 schedule. In announcing the results of the 2011 run, physicists indicated that they would have enough data by the end of this year to know whether the Higgs boson exists at around 125GeV, where a tantalizing signal had been spotted. To make sure this comes to pass, the people running the LHC have laid out a schedule that will see the machine pump out three times as many collisions this year as it did in the one just passed. They'll also boost the energy slightly before sending the collider into an extended shutdown that will start next winter.

A catastrophic failure early in the LHC's history revealed a flaw in some of the superconducting hardware that helps keep the protons on track as they circle the accelerator. To compensate, the accelerator has been running with each beam at 3.5TeV (for a combined energy of 7TeV), half its design energy; an extended break would be required to replace the faulty hardware. At the reduced energy, however, the LHC has outperformed most people's expectations, placing a definitive answer on the Higgs within reach. That prospect has caused the LHC management to revise some of its plans in the expectation that the Higgs can be discovered or ruled out before the extended shutdown.

Read the comments on this post

Possible Higgs boson signals, but we won’t know for sure until next year

This morning, the spokespeople for the two main detectors at the Large Hadron Collider, ATLAS and CMS, gave talks on their teams' latest results in the search for the Higgs boson. As expected, the results were a bit ambiguous, as the signals that are consistent with the presence of the Higgs didn't rise much above two standard deviations away from background noise. But the details were even more confusing. Although both teams see signals in roughly the same area, CMS sees two of them, and appears to exclude the area where ATLAS' signal peaks.

The Higgs boson is predicted to be the last undetected particle of the Standard Model. It's a necessary outcome of the Higgs field, which provides the other particles mass. There are other ways of producing a Higgs field (and other ways of having a Higgs-like particle), but all of these require extensive modification of the Standard Model. Since the Standard Model works extremely well, researchers have been searching for the expected Higgs particle; the LHC was designed in part to be able to find it.

Read the comments on this post

Rolling the dice: understanding how physicists hunt for the Higgs

Tomorrow, CERN will be webcasting a talk on the latest results in its search for the Higgs boson, a particle that is theorized to provide other particles with mass. The director of CERN has gone on record as saying there won't be any announcement that we've definitively discovered the Higgs, nor will there be any statement indicating that we've completely ruled out its existence. Still, expectations are high that we'll find some signal indicating the Higgs is probably at a specific mass—rumors have it near either 120 or 140GeV.

Even as the webcast proceeds, science writers everywhere will be scrambling to explain the results. We thought we'd get a jump on things and give you an explanation of what exactly the scientists at the LHC's two general-purpose detectors, ATLAS and CMS, are looking for, and why it's so hard to be certain about what they've seen.

Read the comments on this post

Fast neutrinos, C-P violations, and the shrinking space for the Higgs

It has been a busy week in the world of particle physics, with attention focused on the home of the LHC: CERN. This year, the LHC generated five inverse femtobarns worth of data—nearly half the amount generated during the entire lifetime of the Tevatron—before shutting down the proton program a few weeks ago. From now until its scheduled winter shutdown, the LHC will be doing lead ion collisions to examine the quark-gluon interactions that dominated the Universe immediately after the Big Bang.

In the mean time, analysis of the data has continued, and some significant news has come out this week. A further dissection of last year's data has placed tighter limits on where the Higgs boson, which provides mass to other particles, might be hiding (assuming it exists). Meanwhile, the LHCb detector, which studies particles that contain heavy quarks, has found an anomalous behavior that might hint at physics beyond the Standard Model. And the LHC accelerator chain has sent some more neutrinos to detectors at Italy's Gran Sasso, which has helped them eliminate some potential sources of error in their faster-than-light findings. We'll take a look at each of these in turn.

Read the comments on this post