Particles collide at an exhibit at CERN, whose scientists hope to discover the Higgs boson, a theoretical particle that could explain how the universe is built.
Clues From Geneva's Collider Suggest Existence of Higgs Boson, Fabled Particle Key to Presence of Stars, Planets, People
Scientists are making tantalizing progress in the hunt for the elusive Higgs boson, a theoretical particle that could explain how the universe is built, though their data aren't robust enough yet to claim a conclusive discovery.
On Tuesday, physicists at the Large Hadron Collider, or LHC, near Geneva, Switzerland, said that data from two independent experiments had narrowed the range of the would-be particle's likely mass.
The Higgs boson is the only particle that the standard model of physics says should be there but hasn't been observed in an experiment. The model describes how matter is built and particles interact.
Scientists claimed progress in the search for the Higgs boson - colloquially known as the 'God particle' - which is considered the basic building block of the universe, Gautam Naik reports on digits. Photo: Getty Images.
Proof that the particle exists would help explain a big puzzle: why some objects in the universe—such as the quark, a constituent of protons—have mass, while other objects—such as photons, the constituent of light—possess only energy.
By extension, its discovery would help explain the presence of stars, planets and humans, and thus rank as one of the biggest coups for modern-day physics.
"The Higgs is the missing piece" in the current theory of matter, said Stefan Soldner-Rembold of the University of Manchester, England, who has been on a decade-long quest for the particle, though he wasn't involved in the recent LHC experiments. The latest data may be far from definitive, but "we're going in the direction that it is there," he added.
In 1964, three groups of physicists independently proposed the existence of the Higgs boson. It was named after one of the scientists, Peter Higgs, now an emeritus professor at the University of Edinburgh, Scotland. Thousands of scientists have since tried to chase down the fabled subatomic particle.
Because nobody knows what the mass of a Higgs boson might be, the particle must be hunted indirectly, typically in giant machines that propel particles to near-light speed, then smash them together and generate an array of other subatomic particles.
The hope is that one such particle would be the Higgs itself, though it would almost instantly decay into different combinations of other particles. Finding it would then involve looking for statistically significant "excesses" of those particles.
The latest experiments at LHC, which is overseen by the European particle-physics laboratory CERN, found modest excesses of this sort in the data, a promising sign. One of the experiments, known as Atlas, suggests that Higgs could have a tiny mass, in the range of 116 to 130 gigaelectronvolts, or GeV. The other experiment pegged the particle's mass at 115 to 127 GeV.
On an individual basis, none of these excesses is any more statistically significant than tossing a die and ending up with two sixes in a row. However, physicists are encouraged, because multiple independent measurements indicate that the Higgs may be lurking in the region of 124 to 126 GeV.
CERN researcher Fabiola Gianotti of the Atlas experiment, suggesting a mass about 125 times that of a proton, said.
"Over the last few weeks, we have started to see an intriguing excess of events around 125 GeV. This excess may be due to a fluctuation, but it could also be something more interesting. We cannot conclude anything at this stage. We need more study and more data."
How might the Higgs boson confer mass to particles? Physicists have suggested that as the universe cooled after the Big Bang, about 13.7 billion years ago, a force known as the Higgs field formed, along with the particle.
The video "The ATLAS Experiment - Mapping the Secrets of the Universe," was produced by ATLAS in two parts and describes the creation of the Universe beginning with the Big Bang, the Standard Model of Elementary Particles and forces making up matter, and the idea behind the creation of the ATLAS Experiment:
Under this scenario, the Higgs field permeates the universe, and any particles that interact with it are given a mass through the Higgs boson. The more they interact, the heavier they become. Particles that don't interact with the Higgs field are left with no mass at all.
CERN scientists say they plan to refine their analysis and won't be able to offer a definitive conclusion until sometime next year.
It's been an eventful year for the esoteric field of particle physics, especially at CERN. In September, for example, an experiment there reported ghostlike particles known as neutrinos apparently traveling a tiny bit faster than light, an apparent breach of the cosmic speed limit set down by Albert Einstein.
Yet, like many physicists, Dr. Soldner-Rembold of the University of Manchester isn't necessarily eager for the Higgs to be found.
"It would perhaps be even more exciting if it isn't where it's supposed to be. Then we'd have to come up with something else."
COMMENTARY: BREAKING NEWS: CERN physicists held a seminar on December 13, 2011 providing the latest update on the findings of research being done by the ATLAS Experiment to find the Higgs boson particle. The seminar was in two videos:
The ATLAS Experiment
The ATLAS Experiment is a particle physics experiment that is exploring the fundamental nature of matter and the basic forces that shape our universe. ATLAS has begun the search for new discoveries in the head-on collisions of protons of extraordinarily high energy. ATLAS is one of the largest collaborative efforts ever attempted in the physical sciences. There are 3000 physicists (Including 1000 students) participating from 174 universities and laboratories in 38 countries. Visit http://atlas.ch
The ATLAS Detector
ATLAS is one of two general-purpose particle detectors at the Large Hadron Collider (LHC) in CERN.
The job of ATLAS is to record and visualise the explosions of particles that result from the collisions at LHC. The information obtained on a particle includes its speed, mass, and electric charge, and this information helps physicists to work out the identity of the particle.
ATLAS will investigate a wide range of physics, including the search for the Higgs boson, extra-dimensions, and particles that could make up dark matter. ATLAS will record sets of measurements on the particles created in collisions - their paths, energies, and their identities.
The following view shows ATLAS under construction beginning in 2003 through animations and time lapse images and video clips:
The following two-part video series (a must view) of The ATLAS Experiment explains the inner workings of the ATLAS Detector, how CERN physicists using the LHC collide protons together to create the sub-atomic particles of matter (See The Standard Model of Elementary Particles below) and how those sub-atomic particles are detected, tracked and measured:
This is accomplished in ATLAS through six different detecting subsystems (Innter Detector, Electromagnetic Calorimeters, Hadronic Clorimeters, Muon Detectors, and Particle Identification Detectors) that identify particles and measure their momentum and energy.
Another vital element of ATLAS is the huge magnet system that bends the paths of charged particles for momentum measurement.
The interactions in the ATLAS detectors will create an enormous dataflow. To digest these data, ATLAS needs a very advanced trigger and data acquisition system, and a large computing system.
ATLAS is about 45 meters long, more than 25 meters high, and weighs about 7,000 tons. It is about half as big as the Notre Dame Cathedral in Paris and weighs the same as the Eiffel Tower or a hundred 747 jets (empty).
To view a comprehensive list of images of the ATLAS Detector through its various phases of construction click HERE.
To view the videos produced for the ATLAS Experiment YouTube channel click HERE.
If you would like a more thorough and technical description of the ATLAS Detector, Columbia University has published the following technical paper. You can download it by clicking HERE.
- Late 2009 -- Startup of LHC and first event collisions at a total energy of 0.9 TeV and later at 2.36 TeV (above the previous world record).
- March 2010 -- Event collisions at a total energy of 7 TeV. This led to about eight months of data taking before a few weeks of heavy ion collisions and the usual winter shutdown. Many papers with early results have come as a result of the 2010 run.
- March 2011 -- Event collisions at a total energy of 7 TeV. Two years of much more intensive data taking. There will also be a few weeks of heavy ion collisions and a winter shutdown (Dec. 2011 - Feb. 2012).
- 2013 -- A long shutdown to prepare for an increase of the total energy towards 14 TeV.
- Next 15-20 years -- Continued data taking with publication of results on an ongoing basis.
Make-Up of ATLAS Scientists
ATLAS is a virtual United Nations of 38 countries. In this troubled world, it is inspiring to see people from many lands working together in harmony. International collaboration has been essential to this success. These physicists come from more than 174 universities and laboratories and include 1000 students. ATLAS is one of the largest collaborative efforts ever attempted in the physical sciences.
Large Hadron Collider (LHC)
The protons are accelerated in opposite directions in the Large Hadron Collider, an underground accelerator ring 27 kilometres in circumference at the CERN Laboratory in Geneva, Switzerland. Crashing together in the center of ATLAS, the particles will produce tiny fireballs of primordial energy. LHC recreates the conditions at the birth of the Universe -- 30 million times a second. Relics of the early Universe not seen since the Universe cooled after the Big Bang 14 billion years ago will spring fleetingly to life again. The LHC is in effect a Big Bang Machine. (Portions of this text are paraphrased from an article written by Dennis Overbye in the New York Times on May 15, 2007, with permission.)
The Large Hadron Collider (LHC) is the world's largest and highest energy particle accelerator (17 miles in circumference) located at the CERN facility in Switzerland (Click Image To Enlarge)
The Standard Model of Elementary Particles
The Standard Model of Elementary Particles (simplified version) classifies sub-atomic particles into three familes:
- Quarks, coming in six flavors (u, c, t, d, s and b) and three colors (red, green and blue)
- Leptons, of the charged (electron-like: e, u and t) and uncharged (neutrino-like: Ve, Vu, Vt) variety.
- Force-carrying particles: the photon (y), the eight gluons (g), and the very heavy weak bosons (responsible for radioactive decay: W± and the Z0).
All told, these particles and the way they interplay with one another fundamentally and successfully explains every phenomenon ever observed, with the sole exception of gravitation.
The Higgs boson (H) is the last particle predicted by the Standard Model that has yet to have been found. The Higgs is predicted to be the reason everything in the universe has mass. It is also supposed to break the Electro Weak symmetry: the fact that the EM boson is massless while the Weak bosons have mass.
The following Standard Model of Fundamental Particles and Interactions (expanded version) chart was prepared by the Contemporary Physics Education Project (CPEP) by Lawrence Berkeley National Laboratory Livermore in 2000 and provides more detailed descriptions of each sub-atomic family and the individual particles within each family. This chart does not make reference to the Higgs boson particle which according to theoretical physicists is predicted to exist, but is yet to be discovered.
I hope you have enjoyed this blog post as much as I have enjoyed putting it together for you.