Physicists measured the temperature of the universe in the first moments of its life
Physicists from Brookhaven National Laboratory (USA) claim that they managed to obtain data on the temperature of matter arising from the collision of gold ions in the RHIC collider – it reaches four trillion degrees Celsius, hundreds of thousands of times higher than the temperature in the center of the Sun, the press said. release of the laboratory.
If these data are confirmed, this would mean that quark-gluon matter was obtained at the collider, which, as scientists believe, filled the universe in the first microseconds after its origin 13.7 billion years ago.
“The temperature obtained from the analysis of measurements at the RHIC is significantly higher than the previously established maximum temperature attainable without the release of quarks and gluons from their normal state – confinement (confinement) in protons and neutrons,” says Steven Vigdor, deputy laboratory director in charge of experiments at the Relativistic Heavy Ion Collider (RHIC).
The research results will be published in the journal Physical Review Letters.
“Direct photons” caught?
The RHIC team, by colliding gold ions at speeds close to light, received a very hot substance that existed in this form for less than a billionth of one trillionth of a second – in about this time, light travels a distance equal to the diameter of a proton.
Scientists measured the temperature of this “quark soup” from the spectrum of photons it emitted using the PHENIX detector installed at the collider. However, to isolate in the multitude of particles that arise in the collision, precisely those photons that carry information about the temperature in the first moments – the so-called “direct photons” – is a very difficult task. Brookhaven physicists claim to have solved it.
“In such collisions, photons are generated in a variety of ways. We were able to ‘remove’ the influence of other sources … degrees, “says Barbara Jacak, head of the PHENIX collaboration.
Back in 2005, experiments at the RHIC collider showed that quark-gluon matter, which was formerly called quark-gluon plasma, is closer in properties to a liquid than to a gas: particles in it interact very strongly with each other. Quark-gluon matter is an almost ideal liquid with zero viscosity, there is almost no internal friction in it. Measuring its temperature is one of the most important tasks in the study of the process of evolution of matter.
Bubbles with broken symmetry
Scientists from Brookhaven also claim that they were able to detect in the “quark soup” they created signs of the existence of “bubbles” with broken symmetry, which, in particular, may explain the predominance of matter over antimatter.
Previously, physicists predicted that there is a possibility of the existence of such “bubbles” or regions with broken symmetry. In such areas, according to the predictions of the theory, matter behaves differently during space-time transformations or changes in the type of particles than matter “outside”.
The data from the STAR detector at the RHIC collider, according to scientists, showed that there are signs of parity violation or mirror symmetry, which implies that physical processes proceed in the same way in direct and mirror images, as well as charge symmetry breaking – the same probability of particle production and antiparticles.
Russian physicists are ready to go further
Scientists from the Joint Institute for Nuclear Research (JINR) in Dubna near Moscow, commenting on the Brookhaven study for RIA Novosti, congratulate their colleagues on the interesting results, and believe that further research is needed in this direction.
“Since there are several possible sources of photons, the estimation of the spectrum of direct photons is rather nontrivial,” noted JINR Director Academician Alexei Sissakian, JINR Vice-Director Professor Richard Lednitski and Deputy Director of the N.N. Bogolyubov JINR Professor Alexander Sorin.
“If the very difficult assessment made at RHIC is really correct and the existing ideas about the structure of the phase diagram of nuclear matter are true, this may indicate that ordinary matter, consisting of protons and neutrons, turns into quark-gluon matter at the RHIC energy “, scientists say.
Recently, they say, model-theoretical predictions have appeared that in bubbles of a quark-gluon liquid a violation of fundamental discrete symmetries of nature – mirror and charge ones – can occur. And in the first half of 2009, in the STAR experiment, some preliminary indirect indications of local breaking of mirror and charge symmetries in collisions of gold ions at the maximum possible RHIC energy were obtained, in which ultrahigh magnetic fields are generated that allow observing these effects.
“Unfortunately, there are a number of alternative explanations for the effects observed at RHIC,” the scientists note. “To obtain more definite and reliable conclusions, it is necessary to conduct a series of additional experiments at lower collision energies of relativistic heavy ions.”
Already this year, RHIC plans to start a program of low-energy energy scanning, which will allow changing the macroscopic characteristics of the excited matter formed as a result of collisions – its temperature, baryon density, magnetic field and other parameters. This will make it possible to advance in understanding the nature of the observed effects, as well as in the search and study of new states of matter – their phase transformations, mixed phase, critical phenomena and a critical point on the phase diagram, in the vicinity of which an anomalous increase in fluctuations is expected.
At the same time, lowering the RHIC energy will inevitably lead to a significant loss of luminosity, since the RHIC has not been optimized for these energies, which will become a serious obstacle to the collection of the necessary statistics, preventing the achievement of the set goal, physicists say.
That is why, scientists say, the heavy ion collider NICA being created in Dubna, which will be launched in the next six years, is of great importance for world science.
In the experiments at NICA, it is planned, in particular, to measure the mirror and charge asymmetries, as well as other important parameters, by event.
“Unlike RHIC, the NICA complex was initially optimized for the region of comparatively low energies of 4 – 11 gigaelectronvolts in the center-of-mass system of colliding nucleons of nuclei, at which, according to theoretical predictions, it is possible to obtain the maximum attainable in laboratory conditions baryon density of matter that could arise in natural conditions at certain stages of the evolution of the Universe and, possibly, exists now in the depths of neutron stars, “the scientists emphasize.
According to them, it is in this energy range that the most dramatic changes in the properties of matter are expected as a result of phase transformations.
“The planned average luminosity for heavy ion collisions at NICA – about 10 to 27 collisions per second per square centimeter – is several orders of magnitude higher than the expected luminosity of RHIC in this energy range, which will allow NICA to move to a qualitatively new level of understanding of the fundamental foundations of the structure of the universe”, – the researchers are sure.
“The main work is still ahead,” say the scientists from JINR.