Tel Aviv University researchers have discovered fresh insights into the Higgs boson particle’s behavior (often referred to as the “God Particle”) in a new study, the university revealed on Sunday.
The Higgs boson is a particle that, according to theory, is responsible for particles colliding to produce stars, planets, and other bodies. The researchers are examining the Higgs boson’s decay into a pair of basic particles known as charm quarks.
Prof. Erez Etzion and doctoral students Guy Koren, Hadar Cohen, and David Reikher from Tel Aviv University’s Raymond and Beverly Sackler School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, conducted the study as part of the ATLAS experiment at the Large Hadron Collider (LHC) at the CERN research center. The study team was assisted by Prof. Eilam Gross of the Weizmann Institute of Science.
The “charm” is one of the Standard Model’s six “flavors” or sorts of quarks. Three distinct “generations” of quarks exist. The first generation is composed of the lightest quarks: “up” and “down.” The second generation contains the “charm” and “strange” quarks due to their increased masses. The third generation is composed of the most massive quarks, the “top” (truth) and “bottom” (beauty) quarks.
The Higgs boson is a moderately heavy elementary particle that can be generated in proton collisions with sufficient energy in the accelerator. “It’s fascinating to examine which types of particles the Higgs decays into and at what rate,” Koren stated in a press statement. “To elucidate this question, our group is attempting to determine the rate at which the Higgs boson decays into particles known as ‘charm quarks.’”
Koren emphasized that this is not a straightforward mission. “It is an extremely rare process — just one out of every billion collisions results in the formation of Higgs bosons, and only 3% of the Higgs bosons that do form decay into charm quarks “Koren stated. “Additionally, there are five additional quark kinds, and the issue is that they all leave similar traces in our detectors. As a result, even if this process occurs, it is exceedingly difficult for us to identify it.”
The researchers have not yet detected enough decays of Higgs bosons into charm quarks to determine the process’s rate with the needed statistical precision, but they have discovered enough evidence to determine the process’s maximum rate in comparison to theoretical expectations.
Five standard deviations, often known as five sigma, are the gold standard in particle physics, indicating a roughly 1 in 3.5 million probability that the measurement is a statistical coincidence.
If the rate of decay is found to be greater than predicted, this might be a significant indicator for “new” physics or Standard Model expansions. The researchers determined with a high degree of statistical certainty that there is “no probability” that the decay rate is greater than 8.5 times theoretical expectations, as sufficient decays would have been detected to determine this.
“This may not sound like an exciting proclamation, but this is the first time anyone has ever succeeded in directly measuring the rate of this specific decay, and hence it is a really significant and crucial statement in our field,” Koren explained.
According to Etzion’s press release, the Higgs boson’s decay rate is projected to be proportional to the mass (squared) of the particles it decays into. “As a result, we assume that it will decay into heavier particles (those that are lighter than the Higgs boson) in the majority of circumstances, and only very rarely into light particles.”
According to Etzion, the team’s findings confirm this prediction, with sufficient Higgs decays into heavy third-generation quarks observed to establish their existence and rate.
“While the rate does match theoretical predictions, the game is not yet over because Higgs decays into second (or first) generation quarks have not been detected. Thus, we cannot be certain that the same ‘laws’ apply to quarks from those generations,” Etzion noted.
“If we unexpectedly discover that the Higgs boson decays into them at a rate that is not proportional to their mass squared, this might have far-reaching ramifications for our understanding of the cosmos, and in particular for how elementary particles acquire their mass “Etzion stated. “This is also why we are devoting so much work to characterizing the decay of Higgs bosons into charm quarks — the heaviest quark whose decay rate has not yet been determined.”
The new study is the latest in a recent spate of ground-breaking research released at CERN.
In July, the Large Hadron Collider beauty (LHCb) experiment at CERN announced the discovery of a new particle, Tcc+, a tetraquark, an unusual hadron composed of two quarks and two antiquarks. Additionally, this is the first particle known to possess two heavy quarks and two light antiquarks.
Hadrons are created when quarks collide. Tcc+ is composed of two charm quarks and two antiquarks, one up and one down. The weight of charm quarks (second-generation quarks) is greater than that of up and down quarks (first generation quarks). This is referred to as a “double open charm.” While particles containing a charm quark and a charm antiquark have a charm quantum number equal to zero (referred to as “concealed charm), this particle has a charm quantum number equal to two.
The finding of the new particle opens the door to the hunt for heavier particles of the same type, with one or two charm quarks replaced by bottom quarks, which might have a significantly longer lifetime than any previously known unusual hadron.
In March, physicists from Cambridge, Bristol, and Imperial College London who were participating in the LHCb experiment at CERN published a report indicating that data from the LHC revealed a violation of the Standard Model, which might indicate the existence of new particles or a new force of nature. The article has not been peer-reviewed yet.
The researchers discovered evidence that “beauty” quarks do not decay in the manner predicted by the Standard Model.
Because beauty quarks, which are identical to but heavier than electrons, interact with all forces in the same way as muons and electrons, they should decay at the same pace.
However, the data acquired by the LHCb appear to indicate that these quarks decay into muons at a lower rate than they decay into electrons, which should be feasible only if undiscovered particles are interfering and causing them to decay into electrons at a higher rate.
While the Standard Model does not account for around 95% of the matter in the universe, it is the dominant explanation of particle physics at the moment. If the findings are confirmed further, they may pave the way for discovering an entirely new field of physics.
The LHC, which is 27 kilometers in length, is the world’s largest and most powerful particle accelerator. Two high-energy particle beams smash inside the accelerator, generating new particles and allowing researchers to investigate unstable particles and cannot be viewed directly.