#### In 2012 a new elementary particle, called the Higgs particle, has been discovered at CERN (Geneve) at the Large Hadron Collider (LHC). The discovery became a media event - why?

Elementary interactions, structure of matter and the history of the universe are a very old branch of physics. One can see the fascinating continuity and evolution in time of its questions and goals. But its basic purpose remains unchanged over centuries: to understand the structure of matter and its interactions at shorter and shorter distances.

Izaac Newton has codified gravitational interactions by formulating the general law of gravitation and introduced the notion of mass as the measure of inertia of a body changing its motion.

But the primordial origin of mass remained unknown! What is the origin of the mass of the electron?

There is a surprising link between Newton and the LHC!

In the 19th century the electromagnetic interactions have been discovered and the concept of the electromagnetic field has appeared. A new chapter in the physics of elementary interactions has been opened by the discovery of radioactivity at the turn of the 19th and 20th century by Henri Becquerel and with further fundamental contributions by Maria Skłodowska-Curie, Pierre Curie and Ernest Rutherford.

As later understood, that was the discovery of two new types of interactions called weak and strong interactions, which exist only at the quantum level.

After one century of research, the chapter opened by the discovery of radioactivity is now closed. The last missing link was the Higgs particle. We understand electromagnetic, weak and strong interactions in a fantastic theory termed the Standard Model of elementary interactions.

The discovery of the Higgs particle has fundamental significance for at least three reasons:

it confirms the fundamental role of symmetries as the basis for understanding the quantum world, it explains the origin of mass of the elementary particles and finally, we see once again that we can understand nature in steps, thanks to the approximate laws of physics which describe well certain range of phenomena. This was the case with the Newton theory which appeared to be a good approximation to the Einstein theory of gravity and with quantum electrodynamics, which we understand now as an approximation to the Standard Model. And, most likely, this will also be the fate of the Standard Model which will be embeded into an even more fundamental theory covering an even larger range of phenomena.

There are very strong arguments in favour of a need for such an embedding. On the theoretical side, there are certain puzzles of the Standard Model itself. On the empirical side, some astrophysical observations cannot be explained by the Standard Model.

We are at a turning point of the physics of elementary interactions – one chapter is closed but…

We are convinced the structure of matter has still a deeper layer going beyond the SM.

But how does it look like? There are many ideas. A supersymmetric world? More than three dimensions of space? (Newton’s and Einstein’s gravity has to be „corrected”?) Something else?

At present the main challenge for particle physics and astrophysics, both on the experimental and theoretical side, is to find that deeper theory. It is a pleasure to stress that the Polish scientists have been giving a very significant, highly recognized by the international community, contribution to the final establishment of the Standard Model and to the searches for its extension.

#### Stefan Pokorski is a theoretician physicist, a specialist in particle theory and elementary interactions.

He is a professor at the Institute of Theoretical Physics of the University of Warsaw, a full member of the Polish Academy of Sciences and the Polish Academy of Arts and Sciences.

He has created the Warsaw school of the theory of elementary interactions.

He is the author of 200 scientific publications on the Standard Model and the search for its extension. His works have been cited about 12,000 times. He is the author of the monograph "Gauge Field Theories" (Cambridge University Press, 1987, 2000, 2009). In 2003 he received the Polish Physical Society Marian Smoluchowski Medal. In 2013, he was awarded the Prime Minister's Award "For scientific or artistic achievements, including for outstanding scientific or artistic achievements". He is a laureate of the Alexander von Humboldt Foundation Research Award (2004).

Credits:

Photo by Stefan Pokorski, Fermi National Accelerator Laboratory (Fermi Lab)