II.3 Beyond the Standard Model
Despite its undeniable success, the Standard Model has many obvious deficiencies, such as the origin of mass, the strong CP problem, neutrino oscillations, matter antimatter asymmetry, and the nature of dark matter and dark energy. Therefore, some new fundamental theory is required to explain these problems and reconcile Particle Physics with General Relativity. Some suggestions along this line include super symmetry and string theory, in addition to the various theories of Quantum Gravity.
The Large Hadron Collider at CERN produced incredible results with unprecedented precision. All elementary particles of the Standard Model have been observed, and their creation and decaying properties have been measured exactly as anticipated by the model. The Higgs boson has been also found and its mass of about has been determined as the Standard Model predicted. Nevertheless, there are many observations that confirms the existence of more particles beyond the quarks, leptons and bosons. For example, the way galaxies cluster together is impossible to achieve in a Universe without dark matter. All types of independent cosmological observations, based on various principles, such as gravitational lensing, nucleo-synthesis and the cosmic microwave background radiation, confirm that normal matter is no more than 15% of the total mass in the Universe. The remaining unknown type of matter is called dark because it must be made of particles not described by the Standard Model.
Moreover, noting the fundamental equivalence between mass and energy, many observations confirm that both the both the visible and dark types of matter are about 30% of the total energy present in the Universe, while the remaining 70% is called dark energy, having a constant energy density for the vacuum. The problem is that attempting to explain this dark energy in terms of vacuum energy of the standard model leads to a mismatch of 120 orders of magnitude. These two particular problems are explained by the Duality of Time Theory in terms of the super fluid and super gas states, as we described in section III.3.2.
Additionally, according to the Standard Model, the mass of particles are determined by their coupling to the Higgs field, which may range from particles as light as the electron to as heavy as the top quark. Therefore, the neutrino was originally thought to be massless, but then its oscillation was discovered, as we explained in the previous chapter, which clearly imply that it must have some mass. In the last decade, neutrino masses were found to be extremely low, though definitively non-zero. The Strong CP problem is also another firm indication for physics beyond the Standard Model, in addition to the main problem of Quantum Gravity. Even in principle, the Standard Model is widely considered to be incompatible with General Relativity, which is the most successful theory of gravity.
The standard model has three gauge symmetries: the color , the weak iso-spin , and the weak hyper charge , corresponding to the three fundamental forces excluding gravity. Due to re-normalization the coupling constants of each of these symmetries vary with the energy at which they are measured. Around these couplings become approximately equal, which led to speculation that above this energy these three gauge symmetries are unified in one single gauge symmetry with a simple gauge group, and just one coupling constant. Popular choices for the unifying group are the special unitary group in five dimensions and the special orthogonal group in ten dimensions . Such theories that unify these symmetries in this way are called Grand Unified Theories. However, these theories predict the creation of magnetic monopoles in the early universe and the instability of the proton; neither of which have been observed.
In addition to all these problems, the problem of matter antimatter asymmetry is also not explained in the Standard Model, as it is obvious that the universe is made out of mostly matter, whereas matter and antimatter should have been created in almost equal amounts. The Standard Model does not provide any mechanism sufficient to explain this asymmetry.
There are also some unexplained experimental results, such as the proton radius puzzle and anomalous magnetic dipole moment of muon. The Standard Model makes precise theoretical predictions regarding the atomic radius size of ordinary hydrogen and that of muonic hydrogen that consists of a proton-muon system in which a muon is behaving as a heavy variant of an electron. However, the measured atomic radius of muonic hydrogen differs significantly from that of the radius predicted by the Standard Model using existing physical constant measurements by what appears to be as many as seven standard deviations. Also, the experimentally measured value of muon s anomalous magnetic dipole moment is significantly different from the predicted value.
It must be also noted that some fundamental features of the Standard Model are added in anad hocway, since it depends on 19 numerical parameters whose values are only known from experiments.
Various models beyond the Standard Model have been constructed so far in search for acceptable solutions to these problems, but none has been proved to be fully consistent with all the available experimental data, and there are yet no credible suggestion that can be tested experimentally. After discovering the Higgs boson, researchers at the Large Hadron Collider have done many experiments and analysis in trying to discover any hints of physics beyond the Standard Model, but tantalizing glimpses of new physics have been harder to spot than many physicists had been expecting. Many quadrillions of particle collisions did not bring any significant insights beyond the discovery of the Higgs boson.