Will Supersymmetry Save or Ruin Physics?

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One of the biggest challenges today lies on the frontiers of particle physics. Despite what many people believe about the Higgs Boson, not only did it resolve a missing part of particle physics but it also opened the door for other particles to be found. Refinements at the Large Hallidron Collider (LHC) at CERN will be able to test for some of these new particles. One set of these fall into the domain of supersymmetry (SUSY), a 45-year-old theory that would also solve many open-ended ideas in physics such as dark matter. But if the Raza team at CERN, led by Maurizio Pierini with scientists Joseph Lykken and Maria Spiropulu a part of the team, fails to find these "exotic collisions” then SUSY may be dead – and possibly much of nearly half a century’s worth of work (Lykken 36).

What the Heck is the Problem?

The Standard Model, which has held up to countless experiments, talks about the world of subatomic physics which also deals with quantum mechanics and special relativity. This realm is made up of fermions (quarks and leptons that make up protons, neutrons, and electrons) which are held together by forces which also act on bosons, another type of particle. What scientists still don’t understand despite all the headway the Standard Model has made is why this force even exists and how it acts. Other mysteries include where dark matter arises from, how three of the four forces are united, why there are three leptons (electrons, muons, and taus) and where their mass comes from (Ibid).

The biggest issue at hand though is known as the hierarchy problem, or why gravity and the weak nuclear force act so differently. The weak force is nearly 10^32 times stronger and works on the atomic scale, something that gravity doesn’t (very well). W and Z bosons are weak force carriers that move through the Higgs field, an energy layer that gives particles mass, but it is unclear why movement through this doesn’t give Z or W more mass courtesy of quantum fluctuations and therefore weakens the weak force (Wolchover).

Several theories attempt to address these conundrums. One of which is string theory, an amazing work of mathematics that could describe our entire reality – and beyond. However, a big problem of string theory is that it is nearly impossible to test, and some of the experimental items have come up negative. For example, string theory predicts new particles, which are not only beyond the reach of the LHC, but quantum mechanics predicts that we would have seen them by now anyway courtesy of virtual particles created by them and interacting with normal matter. But SUSY could save the idea of the new particles. And these particles, known as superpartners, would cause the formation of the virtual particles to be difficult if not impossible, thus saving the idea (Lykken 37).

String theory to the rescue?
String theory to the rescue? | Source

Supersymmetry Explained

SUSY can be difficult to explain because it is an accumulation of many theories rolled together. Scientists noticed that nature seems to have lots of symmetry to it, with many known forces and particles exhibiting behavior that can translate mathematically and therefore can help explain each other’s properties regardless of the frame of reference. It is what led to conservation laws and special relativity. This idea also applies to quantum mechanics. Paul Dirac predicted antimatter when he extended relativity to quantum mechanics (Ibid).

And even relativity can have an extension known as superspace, which doesn’t relate to up/down/left/right directions but instead has “extra fermionic dimensions.” Movement through these dimensions is difficult to describe because of this, which each type of particle requiring a dimensional step. To go to a fermion, you would go a step from a boson, and likewise to go backward. In fact, a net transformation like that would register as a small amount of movement in space time aka our dimensions. It is because of this complicated maneuvering through those dimensions that certain particle interactions would be highly unlikely, such as those virtual particles mentioned earlier (Ibid).

Superpartners in superspace.
Superpartners in superspace. | Source

And if superspace exists, then it would help stabilize the Higgs Field, which should be constant, for otherwise any instability would cause the destruction of reality courtesy of a quantum mechanical drop to the lowest energy state. Scientists know for sure that the Higgs Field is metastable and close to 100% stability based on comparative studies of the top quark mass versus the Higgs Boson mass. What SUSY would do is offer superspace as a way to prevent that energy drop from likely happening, lowering the chances significantly to the point of near 100% stability. It also resolves the hierarchy problem by having a superpartner to Z and W, which lowers the energy of the Higgs Field and therefore reduced those fluctuations so that the weak force acts as witnessed. Finally, SUSY shows that in the early universe supersymmetry partners were abundant but over time decayed into dark matter, quarks, and leptons, providing an explanation for where the heck all that invisible mass comes from (Lykken 38, Wolchover, Moskvitch).

The LHC has thus far found no evidence.
The LHC has thus far found no evidence. | Source

The Hunt So Far

Thus, each particle has a superpartner that is fermionic in nature and exists in superspace. Quarks have squarks, leptons have sleptons, and force-carrying particles have SUSY counterparts as well. Or so the theory goes, for none have ever been detected. But if superpartners do exist, they would be just slightly heavier than the Higgs Boson and therefore possibly within reach of the LHC. Scientists would look for a deflection of particles from somewhere that was highly unstable (Lykken 38).

Gluino vs. Squark mass possibilities plotted out.
Gluino vs. Squark mass possibilities plotted out. | Source
Gluino vs. Squark mass possibilities plotted out for natural SUSY.
Gluino vs. Squark mass possibilities plotted out for natural SUSY. | Source

Unfortunately, no evidence has been found to prove that superpartners exist. The expected signal of missing momentum from hadrons arising from a proton-proton collision has not been seen. What is that missing component actually? A supersymmetric neutralino aka dark matter. But so far, no dice. In fact, the first round at LHC killed off a majority of SUSY theories! Other theories besides SUSY could still help explain these unresolved mysteries. Amongst the heavy weights are a multiverse, other extra dimensions, or dimensional transmutations. What does help SUSY is that it has many variants and over 100 variables, meaning that testing and finding what works and what hasn’t is narrowing the field down and making it easier to refine the theory. Scientists such as John Ellis (from CERN), Ben Allanach (from Cambridge University) and Paris Sphicas (from University of Athens) remain hopeful but acknowledge the diminishing chances for SUSY (Lykken 36, 39; Wolchover, Moskvitch, Ross).

Works Cited

Lykken, Joseph and Maria Spiropulu. “Supersymmetry and the Crisis in Physics.” Scientific American May 2014: 36-9. Print.

Moskvitch, Katia. “Supersymmetric Particles May Lurk In Universe, Physicist Says.” HuffingtonPost.com. Huffington Post, 25 Jan. 2014. Web. 25 Mar. 2016.

Ross, Mike. “Natural SUSY’s Last Stand.” Symmetrymagazine.org. Fermilab/SLAC, 29 Apr. 2015. Web. 25 Mar. 2016.

Wolchover, Natalie. “Physicists Debate Future of Supersymmetry.” Quantamagazine.org. Simon Foundation, 20 Nov. 2012. Web. 20 Mar. 2016.

© 2016 Leonard Kelley

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