Physicists on the verge of confirming gravity in the quantum world

There is a chance to confirm the effect of gravity on the smallest particles of matter, believe researchers at the National Centre for Nuclear Research in ?wierk and the Institute of Physics of the Jagiellonian University.   This would be the first experimental evidence that gravity acts in the quantum world. So far, no experiment allowed to observe the effect of gravity on the mass of elementary particles. So there is no experimental confirmation that gravity indeed works in the quantum world. The answer may be in the interpreted data from the International KLOE-2 experiment, carried out in Frascati, Italy. The at the National Centre for Nuclear Research in ?wierk and the Institute of Physics of the Jagiellonian University took on tracking down gravity in the collected data.       Gravity is the most powerful force on the cosmic scale. However, on distances characteristic for the world of elementary particles its effect is so small that it is very difficult to observe. In December 2011, the Italian National Institute of Nuclear Physics began collecting data in the KLOE-2 experiment, designed, among other thing, to study the physics of particle called kaons. One of the objectives of this experiment is to try to detect gravity in the quantum world. Involved in the project is a Polish team, headed by Prof. Wojciech Wi?licki of the National Centre for Nuclear Research in ?wierk and Prof. Pawe? Moskal of the Institute of Physics, Jagiellonian University. To observe the effect of gravity on elementary particles, the researchers will use one of the most fundamental phenomena of quantum mechanics - quantum interference.       KLOE-2 experiment at the National Institute of Nuclear Physics in Frascati near Rome consists in colliding electron beams with their antimatter partners, positrons. Collision energy is adjusted to induce the creation of mesons Fi zero. Mesons are unstable particles, consisting of one quark and one antiquark. Fi zero mesons generated in collisions almost immediately decay into two K zero (kaons) mesons with no electric charge, that fan out along a straight line in opposite directions. After travelling a short path, kaons decay into pi mesons (pions), which are recorded by the measurement equipment in the KLOE-2 experiment.       Neutral kaons occur in two varieties: short-lived and long-lived. Due to little difference in the masses of these particles, characteristic oscillation spectrum can be observed during decay times. It is this of particular interest to scientists because it is associated with one of the most fundamental phenomena of nature: quantum interference.       In quantum mechanics, states of a particles are described with a function called wave. The wave function is used, for example, to calculate the probability of finding a particle in one or another state. If more than one quantum object of the same type exists in a system, their wave functions overlap and are strengthened in a way typical for the phenomenon of interference. This also occurs in the case of kaons. Scientists believe that this phenomenon will allow them to catch gravity in the act.       "Quantum interference is a phenomenon sensitive to disturbance. Imagine a cleverly designed experiment, just like the KLOE-2. In a vacuum chamber isolated from the environment we study two elementary particles with no electric charge such as kaons, interfering with each other. Interactions with the electromagnetic field and air particles can then be reduced to a small, insignificant values. The only external factor that may not be eliminated and could lead to the disappearance of interference is gravity" - explained Prof. Wi?licki of the National Centre for Nuclear Research.       The researcher argues that this allows to detect even very weak gravity effects. "Calculations suggest that even if graviton (quanta of the gravitational interaction) interaction energy with a kaon is several hundred billion billions times smaller than the of energy nuclear interactions, we will still be able to observe this effect" - he said.       The first particle collisions in the KLOE-2 experiment are already being registered. According to eight-person group of Polish physicists, who work on data analysis and their theoretical interpretation, within a year the amount of collected information should be sufficient to prepare preliminary estimates.       "It would be great if we could see decoherence (disruption of interfencce - PAP), and perhaps even its dependence on the direction of gravity. But even if we do not see it, that will also be a valuable result. We will learn the upper, most accurate to date, experimental limit of the quantum gravitational effects" - said Prof. Pawe? Moskal of the Jagiellonian University.