The Atlas experiment is one of two multi-purpose experiments at the LHC
The Large Hadron Collider (LHC) has picked up tantalising fluctuations
which might - or might not - be hints of the sought-after Higgs boson
particle.
But scientists stress caution over these "excess events", because
similar wrinkles have been detected before only to disappear after
further analysis.
Either way, if the sub-atomic particle exists it is running out of
places to hide, says the head of the European Organization for Nuclear
Research (Cern), which runs the LHC.
He told BBC News the collider had now ruled out more of the "mass
range" where the Higgs might be.
The new results are based on analyses of data, gathered as the vast
machine smashes beams of protons together at close to light speeds.
Primary goals
Scientists from two different experiments (Atlas and CMS) based at the
LHC are scouring the wreckage of these collisions.
One of their primary goals is to search for hints of the Higgs, which
is the last missing piece in the Standard Model - the most widely
accepted theory of particle physics.
Without the Higgs, physicists cannot explain why particles have mass.
But despite the best efforts of scientists working on both sides of
the Atlantic to detect it experimentally, the boson remains a
theoretical sub-atomic particle.
The Standard Model is a framework that explains how the known
sub-atomic particles interact with each other. If the Higgs boson is
not found, physicists would have to find some other mechanism to
explain where particles get their mass from. It would also require
researchers to change the Standard Model.
Rolf-Dieter Heuer, director-general of Cern, said the amount of data
gathered was a factor of 20 greater than had been amassed at the same
time last year.
"With one inverse femtobarn, you cannot cover the entire mass region
which is allowed for the Higgs boson," Professor Heuer told me.
"However, the experiments can now - unfortunately - exclude quite a
large part of this allowed mass region."
Physicists think the Higgs will most probably be found in the low-mass
region - between 114 GeV (gigaelectronvolts) and 140 GeV. While the
gigaelectronvolt is a unit of energy, in particle physics, mass and
energy can be interchanged because of Einstein's equivalence idea
(E=MC2).
Fluctuations
Professor Heuer said that searches at low masses had picked up small
fluctuations "here and there", but that this was expected because
physicists were analysing small numbers across a number of different
"channels".
"The whole thing becomes more interesting the more data we collect,"
he explained.
News of the surplus of interesting events - seen by both the Atlas and
CMS teams - were outlined at the European Physical Society's HEP 2011
conference here in Grenoble, France.
The most significant excess is seen at a mass of 145 GeV and is above
the two-sigma level of certainty. Another fluctuation is seen by the
Atlas experiment at the higher mass of 250 GeV, with a two-sigma level
of certainty.
A three-sigma result means there is roughly a one in 1,000 chance that
the result is attributable to some statistical quirk in the data.
Five sigma means there is about a one in 1,000,000 chance that the
"bump" is just a fluke and is the level generally required for a
formal discovery.
Dave Charlton, who works on the Atlas experiment at the LHC, called
the excess of events "intriguing".
But the particle physicist from the University of Birmingham, UK, told
BBC News these "could go up to three sigma, or they could disappear".
The Large Hadron Collider is a vast machine built in an underground
tunnel that runs in a circle for 27km under the French-Swiss border.
It accelerates two beams of proton particles at near light-speed
around the circular tunnel and smashes them together at selected
collision points around the underground ring. By looking at what is
produced in these particle collisions, physicists should be able to
shed further light on the nature of the cosmos
--
Sateesh.smart
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