‘The Higgs boson has underpinned the standard model, and this is a problem because this theory is so perfect, spherical and seamless that we have no clue as to what the next layer might look like. And this is a challenge because so far we have managed to advance thanks to the fact that we have been able to see flaws in our theories. You can only intrude into the dark areas that your theory has not entered when you find a hole in it through which you can enter. ‘
This reflection shared with me by physicist and scientific communicator Javier Santaolalla during the conversation we had at the beginning of 2019 illustrates wonderfully how one of the greatest scientific successes of the 20th century represents at the same time a challenge in the search for new physics that does not easy to beat. The standard model of particle physics It was developed in several stages during the second half of the last century thanks to the joint efforts of hundreds of scientists, and has brought us huge milestones.
One of them is undoubtedly the discovery of the Higgs boson, a finding in which Javier participated while preparing his doctoral thesis at CERN. The existence of this particle had been predicted in the mid-1960s by various physicists using the best weapon they had at their disposal, the standard model still in full development, so, as Javier assures, experimentally corroborate that a new prediction, And besides, so important, it was correct, it definitely underpinned a theory of particle physics that seemed very difficult to overcome.
Going beyond the standard model is a challenge, but we already glimpse its first fissure
The Standard Model reconciles three of the four fundamental forces of nature: electromagnetism, the weak nuclear interaction, and the strong nuclear interaction. The fourth force, gravity, is out of their reach, which has caused thousands of scientists around the planet to put all their ingenuity at the disposal of science to try to find a theory that manages to unify the four fundamental forces.
Of all the candidates for the theory of everything, the one that is receiving the most support from the scientific community is the formulation of string theory known as M-theory.
Of all the candidates for the theory of everything The one that is receiving the most support from the scientific community (although there are also physicists who do not support it) is the formulation of string theory known as M-theory. Among its main promoters are highly reputed theorists, such as Juan Martín Maldacena or Michio Kaku, but there is still a lot of work to do until researchers understand all the implications of M-theory and it can be demonstrated experimentally. Right now it seems very difficult to achieve it.
The outlook does not invite us to be too optimistic, but, fortunately, a few days ago what many physicists had been anxiously awaiting happened for many years happened: during an experiment at Fermilab, the US high-energy physics laboratory that has the second most advanced particle accelerator after CERN, has appeared a possible crack in the standard model. Something that the most solid and so far infallible theory that we have fails to explain correctly.
It is still too early to take it for granted because physicists are analyzing a huge volume of data, and everything seems to indicate that they have several years of work ahead of them to draw definitive conclusions, but, as we explained last week, they are managing very strong evidence that allow us to glimpse a crack in the standard model.
In his experiment, the muons, particles with a negative electrical charge, like electrons, but with a significantly higher mass, did not behave as our strongest theory predicted. The measurements that the Fermilab physicists have obtained experimentally are so precise that they are reasonably convinced that the muon is being influenced by something that does not explain the standard model.
In this context, it is not at all unreasonable to accept that this deviation could be caused by the presence of an unknown particle, or by the existence of a fundamental force that we do not yet know, and that it could join the catalog of the four forces with which we work.
Álvaro de Rújula, a renowned Spanish theoretical physicist who develops his research at CERN and the Institute of Theoretical Physics of the Autonomous University of Madrid, has confirmed to us in an interview that we will publish soon how hopeful he and his colleagues are about the possibilities that raises the result obtained by the Fermilab physicists. There is no doubt that to develop new physics it is essential to find cracks on the standard model. And it seems that we have already found the first one.
CERN also has a plan to develop new physics
In mid-February we published an article in which we discussed the two strategies that CERN has opted for, precisely to find a way to go beyond the standard model. One of them is to increase the brightness of the accelerator, and the other requires working with a higher energy level. Much higher. But they both have something in common: they require fine-tuning new technology.
Currently the LHC, the main particle accelerator that CERN has, is in a shutdown phase because it is being modified to increase its luminosity. This parameter measures how many potential particle collisions they are produced per unit area and time. Luminosity is measured in inverse femtobarns, each of which equates to 100 million million collisions between protons.
Since the accelerator experiments began in 2010, until the end of 2018, which was the moment when its activity ceased, 150 reverse femtobarns were produced inside. According to the current planning of CERN technicians, the modifications required by the LHC to increase its luminosity will be ready from 2026, so the high luminosity accelerator should be able to produce 250 inverse femtobarns every year until reaching 4,000 during the entire period of activity.
This new high luminosity accelerator seeks to establish itself as a very valuable tool in the search for new physics, so that it could be very useful for corroborate the results obtained by the Fermilab laboratory with new experiments. However, this is not the only ambitious project that CERN has on its hands.
CERN is remodeling the LHC to increase its luminosity. And then a new 100 TeV throttle will arrive
On June 19, 2020, the CERN management unanimously approved the construction project of a new particle accelerator circular that will have no less than a circumference of 100 km (the current LHC measures 27 km). The first stage will begin, according to its initial plans, in 2038, and will require excavating a circular tunnel with a circumference of 100 km very close to the location of the current LHC.
Inside that tunnel they will build an electron and positron accelerator that will have the energy necessary to maximize the production of Higgs bosons at the moment in which these particles collide. Physicists hope that this experiment will help us to better understand the structure of matter, so that when we pass the equator of this century that accelerator will be dismantled and replaced by another circular accelerator capable of working at no less than 100 TeV (teraelectronvoltios).
Physicists are convinced that working with such a high energy level will help them find even more fissures on the standard model. And this will invite you to ask more questions. To formulate more hypotheses. To plan new experiments. And, ultimately, to develop new physics. That is the goal. We can be sure of one thing: the next few decades are going to be exciting for all of us who love science.
Images | CERN