BATAVIA, Illinois (Usa) – Researchers of the Cdf (Collider Detector at Fermilab) experiment, which involves many Italian physicists from Infn and that is currently taking data at the Department of Energy’s Fermi National Accelerator Laboratory, in Chicago, announced today the precision measurement of an extremely rapid transition between matter and anti-matter.
As amazing as it may seem, it has been known for many years that very special species of subatomic particles can make spontaneous transitions between matter and anti-matter. In this exciting new result, Cdf physicists have been able to measure the rate of these transitions for a particle which is comprised of a bottom quark and a strange quark and referred to as a Bs meson. The Cdf result indicates that the transition from a Bs meson into its counterpart anti Bs meson can occur at a rate of 200 billion times per second.
Physicists have been aware of the existence of the phenomena of transition from matter into anti-matter in the bottom/strange quark system for almost 20 years, but they have been unable to measure it directly up to now, because of the incredibly rapid rate of its transformation. The Cdf collaboration, which includes 700 physicists from 61 institutions in 13 different countries, has constructed an incredibly ambitious detector - connected with a particle accelerator called Tevatron - that was in part designed exactly to measure this effect. “It is an extremely important result. The most confirmed theory to describe the behaviour of elementary particles and their interactions is the so-called Standard Model. Nevertheless there are many other theories that attempt to provide a more complete description of the Universe, for instance the so-called supersymmetric theories. According to these theories every known particle must have a partner differing primarily for its rotation speed around itself. The alternative theories to the Standard Model can be characterized by different parameters, but the measurement of the Bs meson transition frequency into its antiparticle obtained by Cdf experiment is not consistent with some of them. So, the Fermilab result helps us to limit these innovative theories, excluding some of their possible configurations” explains Franco Bedeschi, mixing analysis coordinator of the meson Bs experiment.
The results announced today are based on the analysis of data acquired by the Cdf detector between February 2002 and January 2006, where tens of trillion of proton-antiproton collisions produced at the Tevatron, a running period known as “Tevatron Run II”.
“Beyond this remarkable result there is a great effort of the accelerator teams and the detector teams,” said Pier Oddone, Fermilab Director. “It is one of the signature measurements for Run II. As we collect several times the data already on hand, I have great expectations for future discoveries.”
Luciano Ristori, Cdf national coordinator in charge for Italy and researcher of Infn-Pisa, is one of the primary architects of the novel electronics (the so-called Silicon Vertrex trigger) required to identify events with Bs mesons from the billions that collided. He looked upon this result with great pride. “This is a very important result that required many years of hard work by a large number of very talented people”, Ristori said.
Fermilab laboratory is a Department of Energy (Doe). Its director, Dr. Raymond Orbach, congratulated the Cdf collaboration on “this important and exciting new result. Exploration of the anti-world’s mysteries is a crucial step towards our understanding of the early Universe, and how we came to be. Discoveries as important as transitions to and from the anti-world have been made possible by the remarkable, record-breaking Run II performance of the Tevatron, a tribute to the skill of the Fermilab family”.
The Cdf collaboration was formed in the early 80’s and has included a large contingent of Italian researchers of Infn led by Giorgio Bellettini. For over twenty years the Italian group of Cdf has given important contributions both to the design and construction of the detector and to the analysis of the data collected, often holding positions of responsibility within the collaboration. In the context of this specific work, Italian physicists have participated in the development and construction, of key parts of the Cdf detector, and have provided essential contributions to the realisation of this measurement.