In an interview with Grzegorz Jasinski, prof. Agnieszka Zalewska speaks not only of hopes for the launch of the Large Hadron Collider at full planned capacity, but also about his job as president of the CERN Council and the contribution of Polish scientists and engineers in the work of the most powerful scientific instrument on the planet.
Grzegorz Jasinski: The professor, we are behind another important moment in the history of the Large Hadron Collider, and therefore in the history of CERN. Also not without problems, but this time it was much less trouble …
Prof. Agnieszka Zalewska: This time it was a little trouble, and exactly on Easter Sunday was achieved in both the beam vacuum tubes, ie protons circulating in one direction and protons circulating in the opposite direction. I could not even determine how many bunches in each beam was …
Let the tufts that are like a group of protons, because they do not circulate in the pipe in a continuous stream …
Yes, the beam in the accelerator is not only a continuous beam is injected into a portion of the protons. In this single bunch are billions of protons. They then circulate in certain distances from each other. Previously, at the end of the first stage of work Collider, at the end of 2012, these bundles was about 2400. It was the final stage. In contrast, at the beginning starts slowly. I remember when I was the first start, started with two bunches per beam, then zagęszczaliśmy to 1300 has a single bundle. This is achieved gradually. I do not know how many of them now circulated that once tried to create the conditions in which the accelerator is supposed to work, whether it is coming too slowly. You have to remember that you can not effectively accelerate protons from the beginning to the end so as to have all the time in large numbers. This is done with a whole set of accelerators. For these protons in the LHC at the beginning of the linear accelerator, and synchrotrons then there are three such small wheels, it is Booster Proton Synchrotron and the SPS, or Super Proton Synchrotron. So even before we have as many as four LHC accelerator and only at that moment when the protons have the energy of 450 Gev are accelerated in the LHC. The first tests were carried out with this particular energy, even without acceleration, so that you can check all control systems. The CERN cares greatly about the procedure, therefore, everything must be done systematically, step by step, checking out all the stages, every single thing that there were no surprises.
This surprise appeared in 2008 and as you can see, this time from the mistakes of the learned …
Yes, undoubtedly the year 2008 and the false start of the LHC, where we then had to liquidate all year round by the accident has taught us a lot. With the work carried out in the past two years that involved liquid accelerator improvements also concluded that the right decision was to confine itself over the years to work at maximum beam energy to 4 TeV. Here a small digression, electron is such a beloved individual particle physicists, the energy that is obtained particle with a charge such as the electron charge, if the potential difference goes 1 volt. Then we derived units, ie keV, MeV, GeV and TeV is, that teraelektronowolty. And these 4 Tev into the beam, which is the highest energy at which he worked so far is former LHC highest energy ever achieved what former accelerator in the world. The second step is to work at 6.5 TeV per beam, or 13 TeV center of mass system the collision of two protons. The next two months will be served at the investigation of this energy to the final beam luminosity, or planned, the target number of bunches. As everything goes well in June will begin collecting data in the experiments.
Physicists are already rubbing their hands at the times when you will be back to collect data, but as I understand it this time of modernization, which was in terms of experiments dead was used to further developing the data available after the first step of the LHC, including data which helped in 2012 to discover the Higgs particle. or after these two years of analysis, of watching the Higgs particle, which is observed physicists are already unaccustomed to it, in the form in which they found that reconciled, so that she is, and that there were no surprises, which some had hoped …
The surprises there really is not. These two years were needed to actually really well the collected data to develop. In particular, the crowning achievement was announced in March, a joint publication of two experiments: CMS and Atlas. Both teams’ zsypały “their data, and because they had a similar number of good cases, the statistical error was reduced by the square root of two. Such a “chute” results that have different biases also helps in better understanding them. Thanks to the mass of the Higgs particle is now known to within a fraction of Gev. This is a very nice result. All signs indicate that, as expected, this particle is a scalar. Higgs boson is the only part of the scalar …
What does it mean?
This means that you can not distinguish a particular direction of the angular momentum of its own, that is, until momentum. Spatial symmetry is preserved, unlike the particles of matter, which, according to the Standard Model have their own angular momentum 1/2. They are also responsible for the transfer of particle interactions between the particles of matter, they are bosons with Crete own equal 1. Higgs particle is odd, because the angular momentum is equal to 0. The fact that she is a scalar particle is based on the data that exist, almost a foregone conclusion . It’s just that if you want something physicists call discovery, have very high requirements. Therefore, these new data, which is to meet with the higher energy now, when will produce much more Higgs particles, the matter will be measured more accurately, much more accurately determine the angular momentum own. All this to say: yes, we have no doubt, this is a scalar particle, that is exactly the way you expect. Now we can say that we’re pretty sure, but it is not statistically such a value that we can be absolutely sure. Based on these data, which we do not expect it any other way, but you need more of these data. This is definitely one of those things that you will face in the future. Why is this important? Higgs field fills the entire universe, you might ask yourself whether that is a scalar Higgs particle does not have any other consequences. Maybe it’s not the only one scalar particle, may be some other fundamental scalar particles, we do not know? Maybe the Higgs is there a way to understand the structure of the universe? We at this moment, when the Standard Model is complete understand of 5 percent of the mass and energy of the Universe. The remaining 95 percent is something you do not understand. Twenty percent behaves like matter, more than 70 percent behaves as energy. From astronomical measurements, we cosmological evidence for the existence of a material called dark, about which we can not tell you what it is. On the other hand, what is the nature of this matter, we do not know. That it was very natural, if this suit any particles. It is in this case a lot of hypotheses. Everyone expected that the LHC will find these particles …
But I still have not found …
For now, have not been found. Move to higher energies will now expand the search area kinematic these new particles. We’ll deal with it. The fact that they have not found the course a little sad. It would be a great discovery and an important step towards understanding the dark matter. This search at higher energy, the next task facing physicists working at the LHC.
first recall this “clarification” Higgs particles which met in the first step of the LHC, the second is the search for an explanation for this the so-called dark matter, then there is still this dark energy …
The Dark energy is a much more complicated matter. The measurements provide information cosmological. There are a number of such experiments. But some theoretical physicists think that maybe this is the Higgs field is some way towards understanding of the dark energy. This is one of the hypotheses, there is nothing to be particularly attached to it, but you may actually Higgs boson we still learn something else. In particle physics, there are two courses of action. First, increasing energy and thereby increase the mass of particles that can be prepared on the basis of collision in the accelerator. They live very short and it is actually the only way to test them. The second way is to carry out high-precision measurements. Now we begin to explore this area of raised energy, but if there is nothing found, it does not mean that nothing can not be found. Remain the way of collecting much larger number of cases of interactions and be able to much more precisely measure the characteristics of a variety of known particles, including the Higgs. Perhaps acting in this way we find a derogation from the standard model, perhaps these very precise measurements show us that something does not agree that the model does not describe reality, so thoroughly. In the current plans, it is assumed that by 2035 the LHC should earn 100 times more data than today. And it will ne these very precise measurements.
To the layman, physics is one area in which it is hypothesized, then it is confirmed experimentally, or refuting. The creators of the hypothesis rather expect her confirmation. In conversations with researchers involved in the work of the Large Hadron Collider is repeated constantly hope that the standard model, the theory that describes our universe at the moment as best as you can imagine, however, did not confirm, at least not entirely. As I understand this next phase of the LHC activities also are expected surprises. But you have to prepare yourself some variant of the event, when the surprises will not. and Professor imagine a situation in which the discovery of the Higgs in 2012, will be the only discovery collider during its entire business?
I’m trying to imagine myself not. I do not work in the experiment associated with the LHC, so these are my good wishes for colleagues. I am working in neutrino physics, where we have the conviction that we have a fact outside the standard model. But as I say, I try to imagine myself not and I think that if not by direct discovery is through these very precise measurements will be the derogation. Previously I worked in an experiment at the LEP collider last, where we predicted mass of quark t, the heaviest quark. And we were not able to produce, because there was too low energy. Then it was discovered in the experiment at Fermilab in the US and actually had the matter. Anticipate it very carefully. Then, knowing the t quark mass could be predicted mass of the Higgs particle. And she was low, expected even lower weight than is found. LHC was designed to be able to reach for the Higgs boson with a mass of up to several hundred GeV, and in the meantime it turned out that it is about 125-126 GeV. We know that, by very precise measurements, we can reach for new physics particles, even those not directly found. Therefore, the hope here is that a lot of data will give us precise measurements so that we look after it. In contrast, the situation is really difficult, because this low mass Higgs has its consequences. It may be that in the area in which it operates the LHC there are no additional particles that standard model works well for very high energy. But this is speculation until we measure, so it is difficult to predict. We still do not understand some of the facts. In contrast, the theory of such cooperation is a very nice experience. You could ask why physicists are convinced that the standard model does not describe everything. I actually have it answered. Because describes only 5 percent of the mass energy of the universe. And besides, it is characterized in that it has a lot of parameters which do not result from the theory …
This is a very elegant solution, and physics does not like that …
For example, the measurements we know that there are three quark-lepton families and raises the question why the three, not two or four. Normal matter that surrounds us describe using the first family, we do not need the other two. These appear in accelerators and extremely rare in the interactions of cosmic rays, are short-lived, disintegrate.
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