Feature - Beauty to unlock the mystery of asymmetry
Particles and their companion antiparticles differ only in the sign of their electric charge (positive or negative), and in other respects behave identically in most situations. Physicists were therefore stunned in 1964 to discover that some antiparticles behave differently from their particles.
An experiment at CERN called LHCb, for “Large Hadron Collider beauty” (where “beauty”, also known as “bottom”, is the second heaviest of the six known quarks), will study this difference in behavior, referred to as “asymmetry.” The scientists expect to process 700 Terabytes of data a year at several Enabling Grids for E-scienceE (EGEE) sites. In preparation, they’ve recently been running 10-20 thousand simulation jobs a day on the grid. The yearly processing power required for the simulations is equivalent to roughly 3,600 Dell Precision T7400 processors running continuously. Once data starts flowing, they'll need to add 50% more computing power.
Universe out of balance
Scientists refer to the identical, or symmetric, behavior of particles and antiparticles as Charge Parity (CP) symmetry. The unexpected asymmetry that violates it is known as “CP violation”. This asymmetry helps explain why the current Universe seems almost entirely made of particles with virtually no antiparticles. Although the standard model of particle physics does provide a source of CP violation—in weak interactions, for example, nuclear decay—it is not enough to explain the huge imbalance.
“We have a very strong indication that there are other fundamental interactions in the Universe not yet discovered that provide additional CP violation,” says Syracuse University physicist and LHCb collaborator Tomasz Skwarnicki. LHCb will look at rare processes in which heavy particles containing a beauty quark decay, or change, into lighter particles.
Big is beautiful
LHCb chose the beauty quark because of its large mass. The heavier the quark, the better the chances of producing new types of fundamental interactions that are believed to hide at high energies, Skwarnicki explains. Although the top quark is heavier yet, it is much more difficult to produce and is less stable.
Beauty particles have been produced and studied for many years. However, the higher energy beam at the LHC will produce them at a much higher rate than previously possible, and will allow a much more detailed study.
“LHCb will reach a new level of sensitivity which will either lead to discovery of new forces in nature or provide new constraints on theories beyond our Standard Model,” says Skwarnicki. “In some channels we will quickly reach sensitivity beyond the previous experiments, and therefore may discover something new and important quickly. Grid computing is crucial for the LHCb experiment because of the amount of data to be processed and the amount of CPU needed for both processing real data and generating simulations.”