Feeds

Tevatron refines Higgs boson picture

Fermilab’s final fling brings ‘fuzzy’ picture of God particle

Application security programs and practises

“Unfortunately, this hint is not significant enough to conclude that the Higgs boson exists”, says Fermilab physicist Rob Roser – but the difficult last particle is getting closer to revealing its secrets.

Today’s particle physics excitement comes from Fermilab results presented at a conference in La Thuille in Italy, where researchers think they’ve spotted the Higgs boson in an analysis of 500 trillion collisions. Fermilab says two independent experiments, from the CDF and DZero collaborations, have both spotted hints of the particle that’s thought to have created mass at the beginning of the universe.

The new results have a greater than 2 sigma confidence – a huge improvement over last summers 0.5 sigma results.

In the typically-cautious phraseology of high-energy particle physics, Fermilab says the two teams “found excesses in their data that might be interpreted as coming from a Higgs boson with a mass in the region of 115 to 135 GeV (giga-electron volts).

“In this range, the new result has a probability of being due to a statistical fluctuation at a level of significance known among scientists as 2.2 sigma. This new result also excludes the possibility of the Higgs having a mass in the range from 147 to 179 GeV.”

The 2.2 sigma result means the chance that these experiments have produced a statistical fluke is 1 in 250; at three sigmas (1 in 740), the physicists will upgrade the observation to providing evidence of a new particle, and at five sigmas (1 in 3.5 million), they’ll declare the particle “discovered”.

Even so, the latest announcement is important. Coming from two independent experiments is enough to spark excitement, but the mass range turned up in the DZero and CDF experiments also agrees with last year’s announcements from the Large Hadron Collider at CERN. Agreement between Fermilab and LHC results matters because the two accelerators used different types of beams: Tevatron, until its last run in September 2011, fired protons at antiprotons, while the LHC creates collisions between two beams of protons.

This, as explained by Nature, means that the two colliders produced different kinds of decays. The Tevatron was most sensitive to a Higgs emerging as it decays into a bottom quark/antiquark pair, while the LHC spots decays such as the production of photon pairs.

One of the challenges over the years has been to find result sets in which the Higgs boson could be identified in different decay modes.

Fermilab’s analysts have now used most of the 10 inverse femtobarns of data produced by its now-retired Tevatron beam, with only enough data to support experiment until June.

As CERN scales up the energy of the LHC to 8 TeV this year, its physicists hope to end up with a five sigma result for the Higgs boson – sufficient to declare its discovery.

Differentiating the Higgs

The problem in identifying the Higgs signal is that the trillions of events produced by the particle accelerators are detected by the energy the collisions produce – and particularly by the decay of particles produced in the collisions – and the Higgs isn’t the only particle that produce similar particles.

“The Higgs signal is tiny. It’s buried under an avalanche of backgrounds”, a Fermilab presenter* said in a presentation streamed online. Those backgrounds, she explained, come from collisions that have “the same final state”.

Fermilab’s “needle in a haystack” problem is to find particular signatures predicted for Higgs events, and there aren’t many. In approaching their 10 inverse femtobarns of data, the researchers expected to find just 167 Higgs events, and those still be buried under 200,000 background events. ®

*In trying to get the stream to work on a connection badly affected by a Sydney, Australia, thunderstorm, I missed the early slides in the Fermilab presentation. I believe the researcher I was listening to was Michelle Stancari, but am not certain. ®

Build a business case: developing custom apps

More from The Register

next story
Asteroid's DINO KILLING SPREE just bad luck – boffins
Sauricide WASN'T inevitable, reckon scientists
BEST BATTERY EVER: All lithium, all the time, plus a dash of carbon nano-stuff
We have found the Holy Grail (of batteries) - boffins
The Sun took a day off last week and made NO sunspots
Someone needs to get that lazy star cooking again before things get cold around here
Boffins discuss AI space program at hush-hush IARPA confab
IBM, MIT, plenty of others invited to fill Uncle Sam's spy toolchest, but where's Google?
Famous 'Dish' radio telescope to be emptied in budget crisis: CSIRO
Radio astronomy suffering to protect Square Kilometre Array
Bad back? Show some spine and stop popping paracetamol
Study finds common pain-killer doesn't reduce pain or shorten recovery
prev story

Whitepapers

Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Consolidation: The Foundation for IT Business Transformation
In this whitepaper learn how effective consolidation of IT and business resources can enable multiple, meaningful business benefits.
Application security programs and practises
Follow a few strategies and your organization can gain the full benefits of open source and the cloud without compromising the security of your applications.
How modern custom applications can spur business growth
Learn how to create, deploy and manage custom applications without consuming or expanding the need for scarce, expensive IT resources.
Securing Web Applications Made Simple and Scalable
Learn how automated security testing can provide a simple and scalable way to protect your web applications.