The rare decay of the Higgs boson may point to physics beyond the standard model

Particle physicists have detected for the first time a new decay of the Higgs boson, revealing subtle differences predicted by the standard model and potentially pointing to new physics beyond it. The research results are published in the journal Physical Review Letters.

The theoretically predicted Higgs boson since the 1960s was finally discovered in the European CERN laboratory in 2012. As a quantum field, it permeates the entire space and other particles move through it, gaining mass through their interaction with the Higgs field, which can be roughly imagined as a resistance to their motion.
Many properties of the Higgs boson, including how it interacts with other particles and their associated fields, have been measured to be consistent with the predictions of the standard model.

However, an unexplored mode of Higgs decay is theoretically predicted, where Higgs bosons occasionally decay and produce photons, namely photoquanta and Z-bosons, which are uncharged particles that transmit weak forces with two W-bosons.

Scientists from the European Center for Nuclear Research ATLAS and CMS collaborated to search for this particular Z+photon Higgs decay using proton proton collision data obtained from Run 2 from 2015 to 2018. The Large Hadron Collider at the European Center for Nuclear Research is a high-energy particle accelerator located near Geneva, Switzerland. It circulates protons in opposite directions while causing collisions at specific detector points, occurring millions of times per second.

In this operation, the energy of the collision between two protons was 13 trillion electron volts, slightly lower than the current maximum value of the machine, which is 2.1 microjoules in more relevant units. This is approximately the kinetic energy of an ordinary mosquito, or a grain of salt, traveling one meter per second.

Theoretical predictions suggest that every 10000 decays, the Higgs boson should decay into the Z boson and photon, which is the rarest decay in the standard model. It first produces a pair of top quarks or a pair of W bosons, and then they decay into Z and photons themselves.

Atlas/CMS collaboration, with the work of over 9000 scientists, has discovered the "branching ratio", which is the decay fraction of 34 decays per 10000 cycles, plus or minus 11 decays per 10000 cycles -2.2 times the theoretical value.
The measured score is too large -3.4 standard deviations higher than the theoretical value, but this number is still too small to rule out statistical luck. However, the relatively large differences suggest the possibility of meaningful differences from theory, which may be due to the fact that new particles outside the standard model are mediators beyond top quarks and W bosons.

One possibility of physics that goes beyond the standard model is supersymmetry, which assumes a symmetric relationship between half spin particles and integer spins, with each known particle having a partner with a spin difference of half an integer.

Many theoretical physicists have long been advocates of supersymmetry because it can solve many of the challenges that plague the standard model, such as the huge difference between the strength of weak forces and gravity, or why the mass of the Higgs boson, about 125 gigahertertons per volt, is much smaller than the large unified energy scale of about 1016.

Source: Laser Net