Guide to the Cosmos

    Making the Wonders of our Universe Accessible to everyone

A Deafening Silence

The Large Hadronic Collider (LHC) is the largest “atom smasher” and most complex scientific instrument ever built. The LHC is the culmination of more than half a century of ever more capable particle accelerators, mankind’s finest microscopes that probe dimensions a billion times smaller than a single atom. With such machines, particle physicists strive to discover what we and everything else are ultimately made of.


The LHC was built by CERN, the European nuclear research consortium near Geneva, Switzerland, at a cost of over $10 billion, which doesn’t include the salaries of the army of scientists who have worked on this program for decades. There are over 7000 physicists in the ATLAS and CMS collaborations alone. Last July, with considerable fanfare, these groups announced strong evidence for the discovery of the Higgs boson, which had eluded physicists for four decades.


With the champagne bubbles long gone, the physics world is now asking: “What have you done for us lately?”


Physicists expected much more from the LHC than just one new particle, and they promised much more to justify their governments’ investments. If the price of discovery becomes $10 billion per particle, the LHC may become the last particle accelerator ever built.


The LHC’s deafening silence suggests a terrifying answer: there is no new physics. After recording more particle collisions, at higher energies, than all prior physics experiments combined, LHC has found nothing noteworthy, at least so far.


Many physicists deem this the “nightmare scenario” — just the same ole, same ole, without any of the hoped-for discoveries, and providing nothing new to work on.


String Theory took a hit from this absence of new physics. An LHC experiment searching for additional spatial dimensions, the backbone of String Theory, turned up nothing.


The biggest disappointment is the conspicuous absence of supersymmetric particles. For the last 30 years, the theory of supersymmetry (SUSY) proclaimed that every known particle type has a yet-undiscovered partner of the opposite spin. Each known fermion should have a supersymmetric boson, and each known boson should have a supersymmetric fermion. (Spin ½ fermions are the particles of matter, while spin 1 bosons are the particles that carry forces.) Once the LHC was built, so the mantra went, the 17 known fundamental particles would be joined by 17 new particles that were presumably too massive for prior accelerators to produce, as indicated in the following image:



SUSY was proposed to explain why gravity is so much weaker than the other forces and to plug some embarrassing holes in particle theories. Theorists’ calculations of the W and Z boson masses from Higgs interactions were drastically higher than the measured masses — supersymmetric partners were invoked to reduce the interaction and fix this glaring error. Inventing something new that is currently undetectable is a common approach theorists use to explain what they don’t understand — sometimes, it actually works.


SUSY proponents claimed it would eventually fix the most glaring theoretical physics error of all time: quantum field theory calculations of dark energy (aka vacuum energy) are up to 120 orders of magnitude higher than the value measured by cosmologists! It’s almost impossible to be more wrong than that.


Supersymmetric partners were also the leading guess in resolving the mystery of dark matter, the invisible stuff that accounts for over 80% of all matter in our universe. Supersymmetric particles were thought to be massive enough, abundant enough, and elusive enough to fit the bill.


Finally, SUSY is a prerequisite for String Theory. SUSY could be true even if String Theory isn’t, but without SUSY, String Theory is dead.


It’s fair to say that the vast majority of all theoretical particle physicists’ efforts for the last 30 years would be worthless if SUSY isn’t a true property of nature. Theorist Mikhail Shifman has devoted almost his entire career to SUSY. Commenting on how so many theorists could have been so wrong for so long he said: “Of course, it is disappointing. We’re not gods.” I don’t think anyone was under that delusion.


At this time, LHC has stopped generating this type of data, and will be shut down for repairs and upgrading. It will probably be running again and have more definitive data in 2016 (such schedules often slip). Unfortunately, particle physics can’t be advanced in North America; the U.S. doesn’t have a competitive machine and our two major accelerators have been closed.


If the renovated LHC continues to see no evidence of supersymmetric particles, theorists might say: “SUSY particles must be heavier than LHC can produce, so we need a bigger accelerator.” But heavier SUSY particles wouldn’t cancel the calculational discrepancies properly, making the theory more contrived and much less appealing. And who is likely to fund a next generation accelerator for $100 billion?


No one said this was going to be easy — nature jealously guards her secrets. Physicists aren’t going to give up, the LHC has many more years of life ahead, and despite current signs they may eventually make remarkable discoveries.


A modest silver lining is that if SUSY isn’t correct, we won’t have to deal with the awful names given to the supersymmetric particles, such as squarks, sleptons, and winos.


Best Regards,
February 11, 2013
Note: Previous newsletters can be found on my website.


Author of "Everyone's Guide to Atoms, Einstein, and the Universe",
"Can Life Be Merely An Accident?"

& "A World Without Einstein"