what is LHC...

Large Hadron Collider Experiment - The Purpose
The Large Hadron Collider (LHC) just outside Geneva, Switzerland, is one of the most profound scientific projects ever conceived. It is located between France and Switzerland and operated by the European Organization for Nuclear Research (CERN). Scientists from around the world hope it will be fully operational in September 2009. 

The ultimate goal of the LHC is to answer huge scientific questions about the sub-atomic world, the massive cosmos, and their finely-tuned relationship. Initially, it’s an attempt to observe theoretical particles that scientists hypothesize should be there. Ultimately, it’s an attempt to understand the creation of the cosmos and the powerful complexity and design that permeates the particle realm.

Large Hadron Collider Experiment - What is Large?
The Large Hadron Collider is the largest machine in the world. The two accelerator rings are five miles in diameter and nearly 17 miles in circumference. It is the world’s largest refrigeration system with 9,600 magnets cooled to -271 degrees centigrade. It has four large detectors weighing from eleven to 25 million pounds each, and two smaller detectors.

Large Hadron Collider Experiment - What is a Hadron?
Hadrons are sub-atomic particles interacting with the Strong Nuclear Force. What is the Strong Nuclear Force? It is the strongest force in the universe, yet only operates within the nucleus of an atom. It is the force mediated by fundamental particles called gluons, which hold together three fundamental particles called quarks, which make up a proton or a neutron. The Strong Nuclear Force diminishes in strength as quarks get closer and increases in strength as they get further apart. There is no known natural phenomenon strong enough to separate the three quarks. The second order effect for the Strong Nuclear Force is to hold protons and neutrons together in the nucleus of an atom. This strong interaction is liberated during a nuclear reaction, such as what takes place in the sun, a nuclear bomb, or a nuclear reactor.

Large Hadron Collider Experiment - What is a Collider?
A collider is an underground, nearly circular, vacuum tube accelerator, in which charged particles move in opposite directions close to the speed of light. The particles are accelerated and kept at a constant energy by electromagnetic resonators. The particle beams are focused by quadrupole magnets and maintained in their orbit by dipole magnets. When the computers and detectors are ready, proton or lead ion beams are collided at four points where the two rings intersect. The two beams colliding from opposite directions doubles the energy released to an equivalent of 100,000 times the heat at the center of the sun! The detectors capture the moment of particle collision and the computers analyze the data for months and years to come.

What is the Intent?
The ultimate intent of the LHC is to help scientists understand the nature of matter at the moment the cosmos was created. Why did matter remain when matter and anti-matter annihilated each other in an energy transformation during the creation of the cosmos? What happened to the anti-matter? What makes up the 96% of the cosmos we now call “dark matter” and “dark energy?” Does the “Higgs field” (aka, “God’s boson force carrier”) that mysteriously gives mass to particles really exist? What about hidden, extra dimensions of space that quantum models show exist? 

In a nutshell, the Large Hadron Collider experiment is a huge scientific effort to sneak a glimpse into the Mind of God at the moment of creation… Stay tuned!

God particle glimpsed?

Nothing makes my ears prick up more than a rumour that the Higgs boson has been found. For years physicists have been searching for this fleeting speck of matter using the most powerful colliders they have to hand at CERN and Fermilab. The Higgs boson tops the list of physicists? most-wanted discoveries - some have even dubbed it the God particle.

So when I stumbled across a blog by Tommaso Dorigosuggesting that his experiment might just have found the Higgs, I avidly read on.

Dorigo is in the know. He is a particle physicist at the University of Padova in Italy and works on the CDF experiment (pictured), one of two vast detectors built to analyse collisions between protons and antiprotons at Fermilab?s Tevatron accelerator.

The rumour that CDF has seen the Higgs is already spreading.

So why the fuss? Our best theory of matter and the forces that glue it together predicts that the Higgs is what gives other particles their mass.

You?re made up of atoms - some of us more than others. And atoms get their mass from the protons, neutrons and electrons inside. But start asking where electrons and the quarks that reside inside protons and neutrons get their mass from and you?ve hit one of the biggest unknowns in physics.

In the 1960s, theorist Peter Higgs at the University of Edinburgh worked out a mechanism to do it, involving a particle later named after him. It?s our best stab at an answer, so finding the Higgs is a really big deal.

In the CDF experiment, the energy created when protons and antiprotons smash together transforms itself via the equation E=mc² into massive particles, including (physicists hope) the Higgs. In fact, recent results from CDF showed in a roundabout way that the Higgs should probably weigh no more than about 153 GeV, or 160 times heavier than a proton and well within reach of the Tevatron.

According to theory, the Higgs boson lives for less than the blink of an eye before decaying into other particles. Among the easiest to spot amid all the detritus in the detector should be the decay to two heavy electron-like particles called taus. From the momentum and energy of the tau pairs, the CDF team can work out the mass of the mother particle.

CDF found a small bump in their mass plot near 160 GeV ? on the fringes of the allowed range. Dorigo is careful to point out that the statistical significance of the result is not yet strong enough to claim a discovery. The measurement lies only two standard deviations outside the theory.

?We?d need 3 standard deviations before we claimed we?d seen a hint of the Higgs,? says Mark Lancaster, a particle physicist at University College London and a CDF team member, ?and we?d need 5 standard deviations before we said anything officially.?

My guess is that when the experiment collects more data, this enigmatic signal will disappear. Which would be a shame. I?d love the Tevatron to find the Higgs before the next big atom smasher, the Large Hadron Collider (LHC) at CERN, gets into its stride.

Though the LHC is due to turn on later this year, it will take months or years to get enough collisions to claim a discovery.

So there still a chance that the Tevatron could pip the LHC to one of the biggest prizes in physics. It?s just what particle physics, especially in the US, needs to maintain the public?s interest and government funding.

Dorigo?s blog raises another interesting point. Particle physics is big science and its collaborations are getting bigger. More than 400 physicists are members of the CDF team. At the LHC, the teams are 1800 strong. With so many team members and the ever fattening blogosphere, how will the teams stop news of their results from leaking out before they are ready to publish? And should they even try to stop it?

Valerie Jamieson, features editor (Image of Central Detector at CDF: Fermilab)

'God' particle not a heavyweight, studies suggest

The possibility of a high-mass Higgs boson may have just evaporated with new data released today by the Fermi National Accelerator Laboratory in Batavia, Illinois. The result could mean a tougher, more protracted search for a welterweight version of the Higgs, the much-sought-after subatomic particle whose discovery would be a major triumph for particle physics and bring fame to the team who finds it first.

At the heart of the new result is a more precise measurement of the W boson. This is a well known particle, a mediator of the weak force, whose mass is theoretically linked to the Higgs.

The improved measurement will undoubtedly narrow the range of allowable values for the Higgs mass, and may well close off a narrow window on the upper end of that range where direct searches have not yet penetrated.

Prior to last summer, the Higgs was known to reside somewhere in an energy range between 114 Gev and 185 Gev (assuming it exists at all). This is near the limit of where Fermilab's Tevatron can reliably search, but over time researchers have steadily amassed data that could reveal or rule out the Higgs at various energies.

In August, researchers announced they had excluded a value near 170 GeV, the energy where it would be statistically easiest to separate the Higgs signal from background noise. Since then, the possibility that the Higgs might be seen first by the Tevatron, rather than by its successor, the Large Hadron Collider in Europe, has added incentive and drama to the search.

The improved W boson measurement released today was performed by DZero, one of the Tevatrons's two key detectors. The new value, which researchers kept hidden even from themselves until last week, to avoid bias, is 80.401 +/- .044 GeV. This is remarkably close to the current world average of 80.398 GeV.

The chief impact of the measurement is not its value but how much it will reduce the overall uncertainty in the W boson mass. According to Heidi Schellman of Northwestern University, that error could shrink by as much as 10% once it is combined with other measurements. This, in turn, could drop the upper limit on the Higgs mass by 5 GeV or more, making the remaining space between 170 and 180 GeV uncomfortably tight, even for a tiny particle like the Higgs.

"If someone is trying to sell you a 175 GeV Higgs, I wouldn't buy it," Schellman told me.

The news comes just ahead of a widely anticipated announcement on Friday from DZero and its counterpart, CDF, that a wider swath of values around 170 GeV have now been excluded. In other words, a heavy Higgs could be gone by the weekend.

If so, attention will shift to a region below 160 GeV where it is somewhat harder for both the Tevatron and the LHC to see the Higgs. Tevatron seems to be at an advantage, however, because it is working steadily and gradually building up data, while the LHC is on the sidelines following a liquid helium spill last fall.

Earlier this week, researchers at Fermilab also announced they've spotted collisions that produce single top quarks. Such collisions are easily concealed by background noise. Their discovery reinforces predictions that Fermilab should be able to spot a Higgs boson as light as 120 GeV by late 2010.

The Higgs boson is the last undiscovered particle in the so-called Standard Model of particle physics. A first discovery of the Higgs at Fermilab would be electrifying for a facility that is perceived as having long passed its heyday and a shot in the arm for US experimental physicists who have felt that the momentum in their field has shifted to Europe. Researchers agree that even if the Higgs is spotted first at Fermilab, the LHC will still be needed to confirm the find and to explore the new physics that lies beyond, as researchers move into a high-energy domain where the Tevatron cannot follow. 

Illustration: The green shading in the graphs above shows the masses that seem to be ruled out for the Higgs boson. Today's new W boson result lowers the upper limit to an estimated 180 GeV or less. Friday's result is expected to significantly grow the excluded range around 170 GeV, which could seal off the right-hand window of possible values completely. (Courtesy of Dmitri Denisov, DZero)