Particle physicists have ruled out one of the possible remaining hiding places of the Higgs boson, bringing them one step closer to finding the slippery subatomic particle–or, conceivably, to ruling out its existence.
Physicists believe that the Higgs particle interacts with some other particles, like the W and Z bosons, to give them mass. The standard quip about the Higgs is that it is the “God Particle” — it is everywhere but remains frustratingly elusive. Confirming the Higgs would fill a huge gap in the so-called Standard Model, the theory that summarizes our present knowledge of particles [AFP].
The new results, from the Tevatron particle accelerator at the Fermi National Accelerator Laboratory, narrow down the range of masses where the Higgs boson may be found. Physicist Craig Blocker explains that particle accelerators smash particles together and then sift through the debris produced, looking for particles with certain masses. Previous collider experiments had placed a lower bound of 114 giga-electron volts (GeV), a measure that can be used for particle mass, on the Higgs, and theoretical calculations require it to be less than 185 GeV. The new Fermilab results, from its Tevatron collider, rule out a Higgs mass between 160 and 170 GeV…. “If the Higgs had a mass in this fairly narrow range” of 160 to 170 GeV, he says, “we should have seen it, we had a good chance to see it” [Scientific American].
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After all the excitement and anticipation surrounding the Large Hadron Collider’s launch last September, its first few months have been an anticlimactic cascade of disappointments. When a fault shut down the subatomic particle collider just nine days after the first beam of protons whizzed around its 17-mile track, officials at first said it would take several weeks to repair. Then they revised that estimate, saying it wouldn’t be fixed until spring of 2009–and then that changed to summer of 2009. Now, officials say that repairs won’t be finished before September, at the earliest.
To appease impatient high-energy physicists, the laboratory will probably run the machine (albeit at reduced powers) for a ten-month stretch from November until the autumn of 2010 [Nature News]. Officials at CERN, the European agency that runs the collider, hadn’t planned to run it through the winters when electricity costs are higher; they estimate that this appeasement will cost them an extra $10.5 million for electricity.
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The standard model of physics got it right when it predicted where the mass of ordinary matter comes from, according to a massive new computational effort. Particle physics explains that the bulk of atoms is made up of protons and neutrons, which are themselves composed of smaller particles known as quarks, which in turn are bound by gluons. The odd thing is this: the mass of gluons is zero and the mass of quarks [accounts for] only five percent. Where, therefore, is the missing 95 percent? [AFP]
The answer, according to theory, is that the energy from the interactions between quarks and gluons accounts for the excess mass (because as Einstein’s famous E=mc² equation proved, energy and mass are equivalent). Gluons are the carriers of the strong nuclear force that binds three quarks together to form one proton or neutron; these gluons are constantly popping into existence and disappearing again. The energy of these vacuum fluctuations has to be included in the total mass of the proton and neutron [New Scientist]. The new study finally crunched the numbers on how much energy is created in these fluctuations and confirmed the theory, but it took a supercomputer over a year to do so.
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Today at 10 a.m. Swiss time, researchers fired up the Large Hadron Collider (LHC), successfully sending a stream of protons all the way around a 17-mile track for the first time. The enormous collider has been eagerly anticipated by physicists, who hope the device will answer questions about the behavior of subatomic particles and reveal secrets of the universe, but some people have also worried (needlessly, physicists say) that its unprecedented experiments will cause the world to end. For all that hype, the action today was somewhat anticlimatic: Two white dots flashed on a computer screen indicating that the protons reached the final point of the world’s largest particle collider [AP].
As many scientists have pointed out, today’s test run didn’t involve any actual collisions; those will come later when particles shoot around the track in both directions and smash into each other. Therefore today’s event could never have produced any breathtaking results, it was simply intended to test the equipment.
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After 15 years of construction, the world’s largest particle accelerator is warmed up, fully tested, and ready to rumble. The Large Hadron Collider will go into operation on September 10th, and researchers are celebrating every step towards that momentous day. Last weekend, physicists popped champagne to toast the results of a test in which beams of protons were sent barreling into a massive block of concrete, causing the protons to fragment into smaller particles. Researchers have also successfully sent test batches of protons part-way around the collider’s 17-mile circular track.
The Large Hadron Collider represents the science world’s latest, greatest attempt to smash its way into the mysteries of the universe: Beams of protons will eventually collide with the energy of two bullet trains – spawning sprays of subatomic debris that are certain to lead to new discoveries…. One experiment at the LHC, known as ALICE, seeks to re-create the conditions that existed just an instant after the big bang that gave rise to the universe as we know it. [The collider's] researchers want to understand why matter won out over antimatter after the creation of the cosmos [MSNBC].
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