Tuesday, July 5, 2011

Fermilab Collider’s ‘Last Smash’ May Have Found Unknown Particle

Slated to be shuttered indefinitely (or sold for parts) later this year, the nation’s largest particle collider — the Tevatron – may have detected traces of a previously unknown specie of particle that could potentially alter Quantum Theory.

Located at Fermi National Accelerator Laboratory (Fermilab) at the University of Chicago in Batavia, IL, the Tevatron has been pivotal in finding evidence of several particles* formerly only predicted by Quantum Theory. These discoveries have buttressed the validity of what’s known as the Standard Model of particle physics. It is the second most powerful particle collider in the world, just behind the Large Hadron Coliider (LHC) located at CERN in Switzerland.

There has been a slight hope that before the collider was finally shut down it might uncover evidence of the mighty Higgs Boson — the so-called “god particle” that that confers mass onto most other particles in the quantum universe.

But in what may be a quantum “last hurrah”, with a twist, one of the collider’s two detectors has recently detected a mysterious signal that, so far, neither The Standard Model, nor the collaborating team of physicists pouring over the data, can explain. All that they can say, so far, is that it is definitely not the Higgs.

An image showing 6 quarks, 6 leptons and the interacting particles, according to the Standard Model

While scanning the aftermath of certain proton – anti-proton collisions inside the machine’s CDF detector, physicists (Aaltonen et al) noticed a strange “blip” that could be explained by (positing) a previously unknown particle. If validated, this would be the first time that a particle was discovered that had not been intentionally sought after.

Specifically, the physicists were looking at the invariant mass distribution following a series of collisions in which a large particle called a W boson, and one even heavier, unknown particle, were produced. The observed distribution of the putative, unknown particle (measured in terms of its energy-mass content) was in excess of 120 – 160 GeV/c² (that’s 160 billion electron volts).

According to the report** published ahead of print earlier this month, “This mass range is not described by current theoretical predictions within the statistical and systematic uncertainties.”

Of course, there is a chance that the detector’ s results are in error, but, if the results are validated, there is only a tiny chance that it’s just a statistical aberration. The “gold standard” in particle physics for statistical validation is referred to as ’5-Sigma’ (5 standard deviations) which, if achieved, would mean that the the results are real.

Aerial photo of the Tevatron at Fermilab, which resembles a figure eight. The main accelerator is the ring above; the one below (about one-third the diameter, despite appearances) is for preliminary acceleration, beam cooling and storage, etc.

Meanwhile, Aaltonen’s team continues to study the properties of this unaccounted for “excess” and will be using the Tevatron’s other detector, the DZero, to try and duplicate the results. Results are expected soon.

As reported here on PS earlier this year, the famed “atom smasher” is falling victim to cost-cutting measures that are roiling “big science” budgets these days. My previous post on the collider actually garnered a rather touching homage (comment) to the mighty Tevatron — so dear is it to the hearts and minds of particle physics fans.

Let’s hope that the mystery is solved before the great atom smasher’s demise — or better, that the mysterious new particle offers justification for keeping the Tevatron alive just a bit longer.

Just a few months ago, no one could have guess at this development.

Sometimes the Universe throws a curve ball at you (or, a curve particle, in this case).

* For example, the last particle discovered by the Tevatron was the tau neutrino, in 2000

** The preliminary report Invariant Mass Distribution…

Top Image: (Higgs Boson) Lucas Taylor, CERN

Chart: (Standard Model of Particle Physics) MissMJ ; CC – By 3.0

Fermilab: DOE

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