Experiments at CERN announce preliminary evidence of rare disintegration of Higgs boson into muons


The problem with detecting this disintegration is that pairs of muons are also formed in other ways and it is difficult to separate the noise from the signal, explains Prof. Eliezer Rabinowitz of the Institute of Physics at the Hebrew University and chairman of the High Energy Committee of the Academy of Sciences and the Ministry of Science

An event of the disintegration of a Higgs boson into two muons. Photo: Atlas Partnership, CERN

Experiments at CERN announce early indications of a rare disintegration of Higgs boson into muons. The problem with detecting this disintegration is that pairs of muons are also formed in other ways and it is difficult to separate the noise from the signal, explains Prof. Eliezer Rabinowitz of the Institute of Physics at the Hebrew University, chairman of the Higher Energy Committee of the National Academy of Sciences and Israel. On behalf of Israel for the regional cooperation in the SESAMI Accelerator in Jordan.

Recently, the 40th ICHEP High Energy Physics Conference was held (by digital means, as was customary in the days of the Corona AB). One of the important announcements at the conference was of new findings by researchers working on the accelerator that evidence had first been discovered that the Higgs boson disintegrates into two muons. A muon is a heavier double of the electron, one of the elementary particles that make up matter in the universe. While electrons are classified as first-generation particles, muons belong to the second generation. The physics process of a Higgs boson disintegrating into a pair of muons (muon and anti-muon) is a rare phenomenon as only about one in a Higgs boson disintegrates into muons. These findings are crucial to basic physics because they indicate for the first time that the Higgs boson interacts with second-generation elementary particles.

Physicists at CERN have been studying the Higgs boson since it was discovered in 2012 in order to study the properties of this particular particle. The Higgs boson, produced from proton collisions in the Great Hadron Accelerator, fades almost instantly into other particles. One of the main methods for studying the properties of Higgs boson is to analyze the way it breaks down into the various elementary particles and the rate of decomposition.

As is well known, the captain operates two different experiments – large facilities full of equipment that contains many sensors – CMS and Atlas (where the Israeli scientists are also concentrated and where the detectors manufactured in Israel also operate). A CMS experiment obtained evidence of this decline with 3 sigma, which means that the chance of seeing Higgs boson crumble into a pair of muons is less than one in every 700. In the Atlas facility, which according to Prof. Giora Mickenberg of the Weizmann Institute at CERN It only reached Sigma-2. However, when you take the data from the two experiments over the years and combine them into one Big Data array, you get a 1:40 chance, a combination that gives Sigma much larger than three, and provides strong evidence of Higgs boson fading to two muons.

The Higgs boson is the quantum expression of the Higgs field, which gives mass to the elementary particles with which it communicates, through the Brut-Anglet-Higgs mechanism. By measuring the rate at which Higgs boson decays into different particles, physicists can deduce the strength of their interaction with a Higgs field: the higher the rate of decay into a given particle, the stronger its interaction with the field. So far the Atlas and CMS experiments have observed the breakdown of Higgs boson into different types of bosons like W and Z, and heavier fermions like Lepton Tao. The interaction of the Higgs boson with the heaviest quarks, upper and lower, was measured in 2018. Mionons are much lighter in comparison and their interaction with the Higgs field is weaker. Thus, no interactions have been seen in the past between Higgs boson and moons in the LHC.

What makes the studies even more challenging is that in the LHC, for every Higgs predicted boson that crumbles into two muons, there are thousands of pairs of muons produced using other processes that mimic the expected experiment signature. The characteristic characteristic of the fading of the Higgs boson to muons is a small excess of events that accumulate near the mass of a pair of muons around 125 GeV, which is the mass of the Higgs boson. Isolating the interaction between the Higgs boson and two muons is not an easy feat. To this end, the two experiments measure the energy, momentum and angles of the particles nominated for the pair of muons from the Higgs boson decay. In addition, the sensitivity of the surgeries through machine learning was improved. Atlas scientists divided these events into 20 categories that focused on the possible products of the Higgs disintegration.

The results, which so far are consistent with the standard model predictions, used the full data set collected from the LHC’s second session. With more data to be recorded from the next launch of the particle accelerator and with the LHC High-Luminosity, the Atlas-CMS collaborations expect scientists to reach the Sigma 5 sensitivity needed to establish the discovery of Higgs’ boson decay into two classifications and limit the possibility of beyond-model physics The standard that will affect this state of disintegration of the Higgs boson.

“According to the standard model the Higgs particle plays a key role in imparting a non-zero mass to many particles including the protons and neutrons (and the quarks that make them up). In doing so it largely determines the nature of the atoms from which we are made.” Explains Prof. Rabinowitz. Sometimes it can be found in the articles that Higgs is responsible for all the mass in the universe. That is not accurate. Even if the Higgs particle was striking from its work or simply did not exist, many particles would acquire a mass other than zero. Without the Higgs, however, the mass would have been much smaller and the nature of the atoms would have been very different from what we see in nature. In the standard model there is an explicit quantitative expression for this qualitative diagnosis. The larger the mass particle, the more strongly the Higgs particle adheres to it. One of the experimental ways to confirm this claim is to measure the rate at which the Higgs particle decomposes into lighter particles from it. The stronger the Higgs adheres to a particle, the greater its tendency to disintegrate. If the degree of attachment is indeed patterned to the mass of the particle, then it can be predicted that the Higgs will disintegrate directly into a particle called the Tao, which is the heaviest in the electron-matched family, than into the Moon, which is lighter than the Tao but heavier than the electron. From this it can also be deduced that the number of direct decays to the electron, the lightest of all in his family, will be the smallest.

When the huge accelerator and the various detectors were designed it was expected that the number of decays of the Higgs to the Tao would be large enough so that with supreme experimental effort this decay could be expected. The decline was indeed observed and at the rate predicted by the standard model. Only the most optimistic thought that the experimenters would be able to isolate and watch the decline of the Higgs directly to the Moons. Thanks to the creativity of the experimental physicists the evidence for this was indeed probably found and indeed at the expected rate of a lighter particle. “The possibility of detecting an even rarer decay of the Higgs into the lightest particle of the electron family, which is the electron itself, has remained very small in the current accelerator.”

Alongside the successes, Prof. Rabinovich added that “we would be happy to discover phenomena that do not conform to the standard model to find a thread tip for new physics, but the validation of the model is also of great importance and a symbol of the victory of human knowledge.”

The Israelis in the field

And Prof. Giora Mickenberg adds: This is a preliminary finding, which still needs to be verified, but if it is true, it strengthens the proof of the connection between the Higgs boson and the mass of the particles. Previously they were able to prove this on very heavy particles, and now also on lighter particles such as the muons. The problem with the experiment is that the background noise is very loud. It therefore took a long time until they were able to separate the two. We succeeded in this because we collected data from a huge number of collisions, which allowed us to see it. Both CMS and Atlas are very sophisticated experiments. In the atlas the device that detects the muonos is a facility I was in charge of for nine years. The experiments examine slightly different things. In CMS for example there is a double magnetic field in strength compared to that of Atlas so the emphasis is on meons that have medium energy. Atlases show meons that have very high energy and therefore Atlas is less good when it comes to Higgs boson. In the case of the spectrometer used to detect Iuan in the atlas we are talking about a monster of 45 by 25 by 25 meters with 24 magnets on conductors (parts of which were built in Israel AB). We know where each detector and detector is located to the accuracy of its hair. The parts of the machine that are constantly exposed to high energies, function at a level of 99%. This is thanks to engineers who dedicate their entire lives to maintaining them. ”

The Technion holds a Postdoctoral Fellow whose job is to repair defective detectors made in Israel. Prof. Ehud Duchovny of the Technion adds: “The Technion team led by Prof. Shlomit has not yet made a significant contribution to the identification and reconstruction of the muons. The sensors transmit an electrical signal when a particle hits them. According to the heat map and other clues, Next: Detecting the momentum of the particle is much more challenging. ”

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