New Experiments to Probe the Intensity Frontier

By Calla Cofield

In 2009, high energy particle physics grabbed the world’s attention as the Large Hadron Collider smashed through the previous record for energetic particle collisions, and the next few years hold promise for great new discoveries. While it may not be grabbing headlines, the intensity frontier is heating up as well, with the start up of T2K in Japan, construction underway for the NOvA project, and plans for Project X gaining momentum.

From the J-PARC facility in Tokai, to the Super Kamiokande detector in Kamioka, the T2K (Tokai to Kamioka) experiment sends a beam of neutrinos 295 kilometers east to west across Japan. The T2K detectors are now part of the 50,000 tons of water and 11,200 photomultiplier tubes that make up the Super-K water Cherenkov detector. Super-K is used primarily to study neutrino oscillations, although this type of detector was originally intended to search for proton decay. Eventually, physicists hope that studying neutrino oscillations will reveal the mechanisms behind the universal matter-antimatter asymmetry. If equal amounts of matter and antimatter were created after the big bang, they should have annihilated each other; and yet, we see that enough matter survived to form stars, planets and people. T2K began operations in early 2009 and in February 2010 announced that its detectors observed their first neutrino event at Super-K.

In the US, another long baseline neutrino experiment, the Main Injector Neutrino Oscillation Search, MINOS, continues to run strong as construction began last year on it successor, NOvA (NuMI Off axis νe Appearance). NOvA will occupy a new facility not far from the Soudan Mine and the site of MINOS. The new facility will continue to utilize Fermilab’s NUMI neutrino beam, but will extend the baseline distance to 810 kilometers. MINOS currently uses a steel-scintillated detector consisting of planes of magnetized steel and plastic scintillators, while NOvA will use a 15,000 ton liquid scintillator.

Early plans and discussions are on the table for an even longer neutrino experiment that would send the Fermilab beam over 1300 kilometers to the Deep Underground Science and Engineering Lab, DUSEL, in South Dakota. That project–tentatively called the Long Baseline Neutrino Experiment–could be greatly enhanced if Fermilab gets the green light for a proposed high-intensity proton accelerator complex, currently called Project X.

Project X would build on Fermilab’s current accelerator infrastructure, and provide beam for a variety of physics projects, including an increase in the intensity of the beam to NOvA, and experiments to explore rare decays of muons and kaons. Project X Fermilab Associate Director for Accelerators Stephen Holmes spoke on the status of Project X at a press conference at the APS “April” Meeting in Washington DC.

“Project X is currently in a R&D phase. We have a fairly advanced concept for the facility that is forming the basis for the R&D program,” said Holmes in an email. “This concept would provide capabilities beyond what anyone else in the world has today and/or is planning for the future… What needs to happen next is the formal recognition of the need for this facility to support the DOE mission.” That formal support would come in the form of a Critical Decision 0, which Holmes says he hopes the project will achieve in the next year.

The investment in the intensity frontier is not only for the study of rare decays and neutrinos, although those studies present the potential for major advances in physics. In addition, high intensity instruments will prove crucial in confirming and understanding new phenomena uncovered at high energy experiments, like those at the LHC.

“The things that we learn in the energy frontier have to be consistent with the things that we learn in the intensity frontier,” said Duke University physicist and T2K collaboration member Chris Walter, who also spoke at the press conference. Walter explained in an interview that many theories that scientists at the LHC hope to test, such as Super Symmetry, can be confirmed through rare processes that occur at lower energies, but only with very intense sources.

“This will be our first step using these new high intensity accelerators,” said Walter. “We hope to make some exciting discoveries and then continue on towards our future ultimate goals.”