Photons do not interact with each other? And yet! Light was scattered on the light
The first observation of light scattering on light was made by m.in. AGH scientists at the ATLAS experiment at the LHC at CERN. It is not ruled out that the observations will open the door to the so-called “new” technology. new physics. However, the results still need to be confirmed.
Measuring light scattering on light – or more ogólnie photonóin on photons – was performed by an international team ofó³, in whichórego consists of m.in. AGH researchers and nuclear physicists from the Institute of Nuclear Physics of the Polish Academy of Sciences in Krakow. The research was announced by AGH in a message sent to PAP.
It took as long as 80 years to wait for experimental verification of this theory. – In classical theory, two photons do not interact with each other. This phenomenon is impossible if we consider the classical theories in physics. Classical electrodynamics prohibits the occurrence of this type of processów. If these photons interacted willingly with each other, we would not be able to each other in ogóle see . Looking at the sky at night, we would not see stars,” comments Dr. hab. Eng. Iwona Grabowska-Bołd of the AGH University of Science and Technology (WFIiS AGH), whoóra took part in the measurements.
However, the physicist tells us that in the 1930s. In the 1970s, Werner Heisenberg and his doctoral student Leonhard Euler proposed within the framework of quantum theory that two photons, could interact with each other. – That is, if they meet, they can scatter, i.e., change the directions of their motion – just like two colliding billiard balls,” explains a researcher from AGH.
However, this is an extremely rare phenomenon. It took as long as 80 years to verify this theory.
– At the time, próto measure this phenomenon m.in. using indirect measurements, but so far no direct scattering has been measured dwóch photonów – says Dr. Grabowska-Bołd.
The amount of data thatóre could be collected in late 2015 from the Large Hadron Colliderów (LHC) at CERN, for the first time allowed direct observation of photon scatteringów on photons.
Looking for signalsóin the new physics
The idea was born from another experiment. At the LHC, protons collide with each other for most of the year, while one month is reserved for collisions of heavier objectsóin, which are lead nuclei. Physicists are studying what happens when such objects collide with each other. Amongód productóIn collisions they are looking for m.in. of the famous Higgs boson. On the other hand, in the experiment conducted with the scattering of photonów the scientists were looking for a situation when the two lead nuclei would not collide, but would pass close enough to sense each other’s presence through the electromagnetic field.
In research conducted by the group in 2015. lead nuclei were collided. During the intersection of the beams reached 200 thousand. collisions per second. Spośród such a huge number of collisions can be selected for analysis ok. 700. So 99.6 percent. chanceów had to be rejected.
– The ATLAS experiment was designed and optimized for the search for the Higgs particle. The Higgs boson has the characteristic that it lives very krótko and disintegrates quickly after it is created, m.in. for two photons. And the two photons are exactly the signal thatórego we were looking for in our experiment – mówi researcher from AGH. The difficulty was that the two scattered photons had much lower energies, it was harder to measure them.
– We finally managed to observe 13 casesóin whichórych we saw two scattered photons. Physicists announce a discovery when they have a score of at least 5 sigma – that is, 5 standard deviations from a possible background fluctuation – for which theórego probability of error is only 1 to 3.5 millionów. Due to the rather limited number of casesów, we estimated our discovery at 4.4 sigma – mówi researcher from AGH. He announces that in the future, scientists will want to repeat theótion this experiment and see even more pairs of scattered photonsów, so that móc confirm their discovery.
– The process of scattering photonów on photons, from the point of view of theory, opens up interesting possibilities, m.in. searching for the signalóin the so-called. new physics,” comments Iwona Grabowska-Bołd.
The final result of our research was presented in February at the most important conference in the physics of heavy ion collisionsów „Quark Matter” in Chicago. He was received with great enthusiasm by the scientific community.