Fundamentals of Nature

Researchers from the Paul Scherrer Institute have observed for the first time the extremely rare decay of the B_s meson into two muons. They have determined its decay frequency with sufficient accuracy using data collected by the CMS detector at CERN. Their result agrees with the predictions of the standard model of particle physics.

A very rare process in nature should best decide on how we should describe our universe in the future. It is the particular decay of a particular type of elementary particle: the muon. These particles are short-lived and decay into a variety of other particles. According to one theoretical model, a very particular decay process is practically forbidden, whereas according to another it should be allowed. Which theory is correct? By observing many hundreds of trillions of muon decays very precisely, physicists at the Paul Scherrer Institut have come a step closer to solving this puzzle. They have now published their results in the journal Physical Review Letters.

“Higgs Particle Found” announced the media triumphantly in July 2012. But for Roland Horisberger, particle physicist at PSI, this was a premature conclusion: “It will take at least another five years before we can be sure of that”. Whatever the findings à whether this is the original Higgs boson, or only one of the theoretical “Higgs-like” particles à one can surely put a tag on them that reads “PSI inside.”

An international team of scientists confirmed the surprisingly small value of the proton radius with laser spectroscopy of exotic hydrogen. The experiments were carried out at PSI which is the only research institute in the world providing the necessary amount of muons for the production of the exotic hydrogen atoms made up of a muon and a proton.

An international research team has determined with a high level of accuracy, how the proton participates in the weak interaction à one of the fundamental forces of nature. Their results confirm the predictions of the Standard Model of particle physics. The experiment observed the probability of muon capture by protons à a process governed by the weak interaction. The experiment was conducted at the Paul Scherrer Institute, the only institute in the world with an accelerator capable of generating enough muons for carrying out this project in a realistic timeframe.

In a joint seminar today at CERN and the ICHEP 2012 conference in Melbourne, researchers of the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) presented their preliminary results on the search for the standard model (SM) Higgs boson in their data recorded up to June 2012.

Zwei Experimente mit massgeblicher Beteiligung von Forschern des Paul Scherrer Instituts PSI liefern wichtige Ergebnisse bei der Suche nach der richtigen Beschreibung der Welt der kleinsten Teilchen. In den Experimenten haben die Physiker nach sehr seltenen Teilchenzerfällen gesucht. In beiden Fällen konnte der gesuchte Zerfall nicht beobachtet werden wodurch bestimmte Modelle der Teilchenphysik ausgeschlossen werden konnten.This news release is only available in German.

A new measurement of the muon lifetime à the most precise determination of any lifetime à provides a high-accuracy value for a crucial parameter determining the strength of weak nuclear force. The experiments were performed by an international research team at the accelerator facility of the Paul Scherrer Institute.

The proton à one of the smallest building-blocks of all matter à is even smaller than had previously been assumed. This discovery is the result of experiments carried out at the Paul Scherrer Institute (PSI) in Villigen, Switzerland, by an international research team.

CERN has been able to take the first measurements of collisions between the highest-energy particles ever generated. These collisions were performed at CERN's new LHC accelerator and recorded with the CMS Experiment, which involved a key component (the barrel pixel detector) contributed by the Paul Scherrer Institute in collaboration with Swiss Universities. The first LHC operation in Dezember 2009 has now resulted in a first particle physics publications of the CMS experiment. This is after a remarkable short time , given the compexity and the size of this gigantic experiment with over 3000 physicists and engineers from close to 40 countries.

Neutrons, synchrotron light and muons are very useful for researchers in a variety of disciplines. Using these probes, we can determine the structure of crystals, they help us understand magnetic processes, or they can reveal the structures of biological materials. However, producing these probes is so difficult that most research groups will not have a neutron, muon or synchrotron light at their own scientific centre.