LHC Researchers Still Can't Find Higgs Boson, Settle for New "Chi" Particle
December 22, 2011 7:30 PM
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The LHC does what every good particle smasher does -- find a new type of subatomic particle
The Large Hadron Collider has finally began to fulfill its potential. After a
string of early malfunctions
, the world's largest collider has
set records for the highest energy particle collisions
. Now, even as
the smashing continues
, the hard part begins -- combing through the mountains of data looking for interesting discoveries.
At the top of their wish list
is the legendary Higgs boson
, nicknamed the "God Particle", by the more colorful media establishment. The Higgs boson is a theoretically predicted particle that would confirm the standard model of particle physics, explaining why some particles have mass and others don't. Alternatively if the supersymmetry model holds true, up to five Higgs boson variants could be observed, disproving some of the standard model's theory.
I. LHC Finds a New Particle -- but not the Higgs Boson, Yet
Well, some of the data collected thus far has been scoured through, and disappointingly no conclusive evidence of the Higgs boson emerged (some readings indicate the possible existence of the particle, but were inconclusive). Instead researchers
a new kind of Chi (X
The Chi (X
particle is composed of a bottom quark (also known as a "beauty" quark) and its anti-particle equivalent, the anti-bottom quark.
A computer visualization of one the LHC's collisions. Scientists must sift through the individual sea of particles (trails shown here), hunting for new ones. [Image Source: CERN/LHC]
Quarks are tiny subatomic particles, which make up the constituents of atoms -- like electrons, protons, and neutrons. Any particle made up of quarks is called a hadron. Their are two kinds of hadrons -- those made up of three quarks (baryons) and those made up a quark/anti-quark pair (meson). Since the new Chi particle is composed of a quark/anti-quark combination, it belongs to the meson subclass of the greater hadron family.
Mesons have integer spins, meaning that they are bosons (like the Higgs boson!). Boson particles obey Bose-Einstein statistics.
Chi mesons have a isospin of 0 (which dictates their strong interactions) and a positive G-parity on that isospin. Together this is represented in shorthand as 0
. The previously discovered chi particles had positive (P) parity and C-parity, and angular momentum values ranging from 0 to 2. The previously known Chi mesons are --
The new particle is a "higher energy" Chi particle, in that it has a higher angular momentum number of 3. It's been dubbed
(3P) -- (0
). Given the mass of the bottom quark -- over four times the mass of a proton -- it is unlikely that the LHC would have enough energy to create higher energy Chi particles.
II. LHC Passes a Time-Honored Accelerator Rite of Passage
Andy Chisholm, a PhD student from Birmingham, England, who worked on the project
that the location of the new Chi particle was a lucky find. He comments, "Analysing the billions of particle collisions at the LHC is fascinating. There are potentially all kinds of interesting things buried in the data, and we were lucky to look in the right place at the right time."
Finding its first particle is sort of a right of passage in the particle collider world. Past accelerators like FermiLab's Tevatron (America's largest particle accelerator,
as the American government does not like to
spend even a fraction
of its immense budget funding important scientific research)
labored for years or more before finding their first particle, then went on to find many more particles over a fruitful run.
The first one is always the hardest. [Image Source: Universal Studios]
University of Birmingham physicist, Professor Paul Newman comments on this right of passage, stating, "This is the first time such a new particle has been found at the LHC. Its discovery is a testament to the very successful running of the collider in 2011 and to the superb understanding of our detector which has been achieved by the Atlas collaboration already."
Thus far at least 175 mesons have been discovered.
With each new meson discovered physicists creep a bit closer to understanding the strong force. This understanding helps them better known what to look for when trying to find the kind/kinds of Higgs boson(s) predicted by the standard and supersymmetry theories of particle physics. In that sense the discover of the new Chi quark may not be a "pay dirt" hit so to speak, but it's also not entirely a wash in the Higgs boson chase.
It also provides a bit of validation and good publicity, desperately needed to help the public appreciate the value of the accelerator -- which cost approximately $4.4B USD to build, and another billion or so to operate. Keeping the 17 mile, 28 km (circumference) accelerator productive will help it avoid a fate similar to America's Tevatron. If they can do that, physicists can continue their merry hunt for the Higgs boson and a better understanding of how our universe works on the most fundamental level.
Arxiv [Printserver; CERN]
This article is over a month old, voting and posting comments is disabled
12/23/2011 3:53:58 AM
Didn't they say there were evidence for Higgs when a spike occured in around 122GeV?
It was just that the result was 3 sigma standard deviation significance, not enough to announce a discovery (5 sigma required)
12/23/2011 6:37:19 PM
Yes they did, and here is Daily Tech's write-up.
Try to keep up, Jason.
"I modded down, down, down, and the flames went higher." -- Sven Olsen
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