A new measurement of the muon life - the more accurate determination of a lifetime in the world of small particles - provides a very accurate value of a parameter that is critical to determine the intensity of the weak nuclear force. Experiments were carried out by an international team of researchers at the Paul Scherrer Institute. Results will appear shortly in the journal Physical Review Letters.
The weak force is one of the four fundamental forces of nature. Although we are in our daily life difficult operations that are determined by the weak force, is nevertheless essential. Is responsible for about operations that allow sunshine. Now an international research team led by researchers at the University of Illinois, Boston University and the University of Kentucky (all USA) Paul Scherrer Institute carried out experiments, by which a parameter the strength of the weak interaction - as the weak force is also called - is of vital importance, could be measured with exceptional accuracy. This is known as Fermi constant parameter is one of the fundamental constants that are necessary for accurate calculation of the processes in the world of smaller particles.One of the main achievements in the understanding of the subatomic world had existed in the seventies of last century, physicists have shown that weak and electromagnetic interactions - another of the four fundamental forces - actually two aspects of a single interaction. This is known as the electro weak interaction and its strength is determined by three parameters - one of which is the Fermi constant.Lifetime of the muon - the key to the strength of the weak force.
The new value of the Fermi constant is a very precise determination of the muon life - makes - the most accurate measure of a life in the world of atoms and elementary particles. The muon is an elementary unstable particle decays with a lifetime of about 2 microseconds (millionths of a second). This deterioration is determined solely by the weak force and is a fairly simple relationship between the life of the muon and the strength of the weak force. "The determination of the constant life muon Fermi theory requires a precise and elegant. But in 1999 the theory was not as good as Hertzog experiments' said David, who was at the time of measurement, researchers University of Illinois and now at the University of Washington works "since then, most lakes have eliminated virtually all theoretical uncertainties. The biggest uncertainty in determining Fermi constant now depended on how well the measured muon life. "
Measurement, 100 billion times repeated - Accuracy: 2 millionths of a millionth of a second.
The experiment Mulan (Muon Lifetime Analysis) took advantage of muons produced in the accelerator facility at the Paul Scherrer Institute in Villigen (Switzerland) - the largest of muons in the world and the only place that can be done in the most precise experiments. "The heart of the experiment were special targets - -. disc collection, which were always positive groups of incoming muons stopped, " said Bernhard Laussa by PSI, the beginning of the experiment, "The beam was then every off quickly, with about 20 muons are bogged down in the target. Over time, each of these muons was divided and sent as a sign of its rapid decomposition of positron - a positively charged electron -. No "The positrons were detected from 170 detectors surrounded the target in the form of a football giant. Robert Carey of the University of Boston, added: "We repeated the process 100 000 000 000 muons packages, looked at billions of individual decays collected 100 terabytes of data stored for later analysis in the super computer of the U.S. National High Performance Computing Center (NCSA) in Illinois were. From these data, the distribution of the lifetimes of each muon is produced and used to determine the half-life for those who took the value of 2.1969803 ± 0.0000022 microseconds. The uncertainty of this result is 2 millionths of a millionth of a second - this is a real world record. "
Text: Paul Piwnicki/David Hertzog
Collaboration
The experiments were carried out under an international collaboration in the Paul Scherrer Institute, scientists involved in the following institutions:
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, USA
- and Department of Physics and Astronomy, University of Kentucky, Lexington, USA
- and Department of Physics, Boston University, Boston, USA
- and Department of Physics, James Madison University, Harrisonburg, USA
- and Department of Physics and Computer Science, Regis University, Denver, USA
- or Department of Mathematics and Physics, University of Kentucky Wesleyan, Owensboro, USA
- or Paul Scherrer Institute, Villigen PSI, Switzerland
- Kernfysische or Versneller Institute, University of Groningen, Groningen, Netherlands
About the ISP:
The Paul Scherrer Institute, builds and operates major facilities, complex research and provide the scientific community nationally and internationally available. Prepared by the solid-state research and material sciences, elementary particle physics, biology and medicine, energy and environmental research. With 1,400 employees and an annual budget of approximately CHF 300 million, is the largest research institute in Switzerland.
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