How hadrons are born at the LHC?

Thanks to data collected at the Large Hadron Collider, scientists at the Institute of Nuclear Physics of the Polish Academy of Sciences in Krakow have obtained new information on hadronization. This is the process by which quarks and gluons bind together, resulting in the birth of hadrons – particles that are conglomerates of two or three quarks.

The world around us consists overwhelmingly of particles made of three quarksoin interconnected gluons. The process of quark binding itselfow is poorly understood. At the Large Hadron Colliderow (LHC) physicists have been prob are to expand the knowledge of this subject. Within the framework of the international co-ohe researchers from the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Cracow (IFJ PAN) are also conducting research there, whichoers have obtained new information on the course of hadronization in proton collisionsow.

In the LHC gas pedal protons accelerated to the highest energies collide. During such collisions, their constituent particles, quarks and gluons, form an intermediate state, whichory exhibits the properties of a liquid. Scientists have made observations from whichowhich show that in collisions of relatively simple particles such as protons, ointo an intermediate state exhibits properties, typical of collisions of heavy ionsow – much more complex objectow. This indicates the existence of a new state of matter: a quark-gluon plasma, in which theoIn other experiments, quarks and gluons behave almost like free particles. This liquid instantly cools and, as a result, quarks and gluons re-bond with each other in the process of hadronization.

The results of the Krakow researchers’ research were published in the „Journal of High Energy Physics”.

– GloThe important role in proton collisionsow plays the strong interaction, described by quantum chromodynamics. However, the phenomena occurring during the cooling of quark-gluon plasma are so computationally complex that so far it has not been possible to know and understand well the detailedołoin hadronization. And yet this is a process of crucial importance! It is due to it that in the first moments after the Big Bang from the quarkow and gluonoin formed the dominant majority of particles that make up our everyday environment – explains on the website of IFJ PAN dr hab. Eng. Marcin Kucharczyk.

The hadronization process occurs rapidly. For this happens in a very small area (its size reaches only femtometerow, i.e. millionths of one billionth of a meter) wokoł point of proton collisionow. All this makes direct observation of hadronization impossible. But physicists have a wayob. Thanks to the rotion of intermediate methods, in whichohe key role is played by the basic tool of quantum mechanics: the wave function, whichowhich properties map the characteristics of particles of a given type.

– The wave functions of identical particles will effectively overlap, i.e. interfering. If interference results in their amplification, moWe are talking about Bose-Einstein correlations, if to suppress the – about Fermi-Dirac correlations. In our analyses, we were interested in amplifications, thus Bose-Einstein correlations. We searched for them between pi mesons flying out of the hadronization region in directions close to the original direction of colliding proton beamsow – explains Bartosz Małecki, a PhD student at the IFJ PAN website.

Krakow physicists in their research used a method thatora has been developed for radio astronomy. This is the so-called. HBT interferometry (from the names of its twoochorcow: Robert Hanbury'Brown and Richard Twiss).

This method for particles allows you to determine the size of the hadronization area and its evolution in time. With its help, you can get information, for example, whether the area is roThe data from the LHCb detector have made it possible to study hadronization in the area of the so-called Large Hadron CollideroThe process of hadronization occurs instantaneously in other experiments in hadronizationoThe quarks and gluons are in the process of hadronizationow.

„Data from the LHCb detector have made it possible to study the process of hadronization in the area of the so-called “hadron”. small anglesow, that is, for hadronsow produced in directions close to those of the original proton beamsow. The analysis performed by the group from the IFJ PAN provided indicationsowek that the parameters describing the source of theoThe hadronization bed in the as yet unexplored region of small anglesow, and available from the LHCb experiment, roare the result ofoIn similar analyses performed for larger anglesoin other experiments” – we read on IFJ PAN website.

Research conducted by Krakow scientistsow will be continued in the LHCb experiment for rofor different collision energies and roof a kindoin colliding objectsow. – This will make it possible to verify someore of models describing hadronization, and consequently better understand the course of the process itself – emphasizes prof. Dr. hab. Mariusz Witek.

Sourceobackground: IFJ PAN, PAP, fot. CERN/ LHCb. Pictured are particles produced during one of the collisions dwoch protonow with energies of 7 TeV each, recorded by the detectors of the LHCb experiment in 2011.