Beyond the Standard Model — Or Not

Scientists keep trying to disprove the Standard Model that governs modern physics. And they keep failing.

The Standard Model of particle physics, sometimes referred to as the “theory of almost everything,” unites three of the four fundamental forces of the universe. It proposes a zoo of 17 particles to mediate these forces. The last to be found is the celebrated Higgs boson.

According to supersymmetry, every familiar matter particle has a supersymmetric counterpart. Theory predicts most of these counterparts are unstable, so the ones produced in the Big Bang decayed long ago. But the lightest, the neutralino, should be stable and is an ideal dark matter candidate. Click to zoom.
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But the Standard Model has its share of problems. It’s built on the “fundamental constants” of nature, but it doesn’t explain why the constants have the values they do. Nor does it explain dark matter or unite gravity with the other three fundamental forces, a union both physicists and astronomers are convinced must exist.

Physicists’ current favorite of non-Standard theories is supersymmetry, which proposes that each of the 17 particles in the Standard Model zoo has a corresponding “superpartner” with a different spin and probably a heavier mass, too. Supersymmetry solves a lot of problems — most importantly for astronomers, it provides “weakly interactive massive particles” (so-called WIMPs) that might be the dark matter they've been searching for.

But theorists have their work cut out for them. Several teams presenting at the American Astronomical Society (AAS) this week in Long Beach, California, have tried to find non-Standard physics in the distant universe, and failed.

Counting Neutrino Families

The universe created hydrogen and deuterium (a heavy version of hydrogen, with a neutron in its nucleus) in the first 20 minutes of its existence. So measuring how much deuterium and hydrogen there is in distant, pristine gas clouds tells us about the newborn universe, including the number of speedy particles called neutrinos that formed in the chaos. The Standard Model predicts three families of neutrinos, and that’s what particle accelerators have found, too, but some non-Standard theories say that number might have changed over cosmic time.

To measure deuterium and hydrogen abundances some 10-12 billion years ago, astronomers such as Ryan Cooke (University of California, Santa Cruz) examine quasars, beacons radiating from the most distant stretches of the observable universe. That emission carries a message of what lies between the quasars and us, so astronomers have an indirect glimpse of ancient gas clouds as they absorb the quasars’ radiation. Cooke’s team measured the primordial abundance of hydrogen and deuterium in several of these gas clouds, and then they converted that value to the number of neutrino families.

“If we found a value different from standard model, then we could also claim that this could be due to a change in gravitational constant or a whole host of other things,” Cooke said at a press conference at the AAS. But they didn’t. They found the number of neutrino families is 3, with a spread in values of 0.5.

The story’s not over yet, though. The team was surprised by the large spread in values, which couldn’t be explained by error alone. So the researchers are re-analyzing the data in a more consistent way. If the spread is still there when they’re done, they’ll have to come up with an explanation.

Of Protons and Electrons

One of the Standard Model’s fundamental constants is the mass ratio between protons and electrons. This ratio relates to the strong force, the force that holds the subatomic world together by binding quarks together to make protons and neutrons and binding protons and neutrons together to make atomic nuclei.

But if the strong force evolves over the history of the universe, then so will the mass ratio. That’s exactly what some theories attempting to go beyond the Standard Model call for.

Julija Bagdonaite (University of Amsterdam) and her colleagues studied PKS 1830-211, a spiral galaxy seen as it was 7 billion years ago. By comparing molecular transitions with those measured in an Earth-bound laboratory, they found that the mass ratio doesn’t change at all.

“This important new result was like a Christmas present for me,” said Rodger Thompson (University of Arizona), who presented the paper at the AAS. “It presents very serious constraints on current alternative cosmologies.”

Fine Structure Constant

The fine structure constant, another of the fundamental constants of the Standard Model, determines the strength of the electromagnetic force. Some supersymmetry models suggest that this constant should vary too. To measure this constant over time, Jonathan Whitmore (Swinburne University of Technology, Australia) and his colleagues observed absorption lines in distant quasars using the Very Large Telescope in Chile.

At this point, you can probably repeat the refrain with me: their results are consistent with no change in the fine structure constant over cosmic time.

What’s a Theorist to Do?

“All three results simply say that what we’ve found now is consistent with the Standard Model,” Thompson said. “Simplified supersymmetry calculations have not given values that are consistent with what we’re observing.”

But supersymmetry is a wily beast. “There are many different ways supersymmetry can be altered to accommodate these results,” Thompson added.

In other words, the measurements above have put some restraints on the multitude of supersymmetry models that theorists can come up with, but theorists still have plenty of room to play. At least now they are playing with a little reality mixed in.

Observers still have room to play, too. Despite the null results, Cooke, Thompson, Whitmore, and their colleagues remain determined to keep going. Many supersymmetry models predict the fundamental constants varied more in the very young universe, so astronomers will keep pushing to ever-greater distances to see if that prediction’s true.

CATEGORIES
Cosmology, News

About Monica Young

Astronomer turned science writer, Monica Young is web editor of S&T, where she creates, manages, and maintains website content as well as contributes to the magazine.

12 thoughts on “Beyond the Standard Model — Or Not

  1. Peter

    If GR is correct, that is, if gravity is not quantized, and the Standard Model is pretty much complete, I can see why theoretical physicists would start to worry…

  2. Tom Hoffelder

    SUSY physicists aren’t having any luck with the LHC either. As particle physicist Don Lincoln said (before the LHC was operating) in his book Understanding the Universe: From Quarks to the Cosmos, "In fact, it is this property of SUSY theory [the mass of SUSY particles being the same as their counterparts] that makes theorists confident that experiments that will operate within the decade will observe the newly predicted particles. If they are not observed, some serious head scratching will result."

    He has confirmed that they are scratching their heads. And I hope they keep scratching their heads, until they come up with a better idea. (Or better names for SUSY particles. I don’t want to be talking about sleptons, the Wino or – especially – the sup squark.)

  3. Robert L. Oldershaw

    1. The Standard Model is primarily a heuristic model with 26-30 fundamental parameters that have to be “put in by hand”.

    2. The Standard Model did not and cannot predict the masses of the fundamental particles that make up all of the luminous matter that we can observe.

    3. The Standard Model did not and cannot predict the existence of the dark matter that constitutes the overwhelming majority of matter in the cosmos. The Standard Model describes heuristically the "foam on top of the ocean".

    4. The vacuum energy density crisis clearly suggests a fundamental flaw at the very heart of particle physics. The VED crisis involves the fact that the vacuum energy densities predicted by particle physicists (microcosm) and measured by cosmologists (macrocosm) differ by up to 120 orders of magnitude (roughly 1070 to 10120, depending on how one ‘guess-timates’ the particle physics VED).

    5. The conventional Planck mass is highly unnatural, i.e., it bears no relation to any particle observed in nature, and calls into question the foundations of the quantum chromodynamics sector of the Standard Model.

    6. Many of the key particles of the Standard Model have never been directly observed. Rather, their existence is inferred from secondary, or more likely, tertiary decay products. Quantum chromodynamics is entirely built on inference, conjecture and speculation. It is too complex for simple definitive predictions and testing.

    7. The standard model of particle physics cannot include the most fundamental and well-tested interaction of the cosmos: gravitation.

    Robert L. Oldershaw
    http://www3.amherst.edu/~rloldershaw
    Discrete Scale Relativity
    Fractal Cosmology

  4. Peter

    It’s not that the Standard Model cannot predict the masses of fundamental particles. It’s that its practitioners cannot accept the obvious answer, that 26-30 fundamental parameters were put in By Hand. I know, That’s not scientific, but neither are the alternatives. Every effort to dispense with a Designer results in some other "design:" a False Vacuum shaped just-so; colliding "branes" in the right number of extra dimensions; an infinite number of throw-away universes, etc. They are sleight-of-hand with regards to explanation, however, as no explanation is offered for what gives rise to the False Vacuum, the branes, the extra universes, etc. Creation of something from nothing is simply beyond the reach of natural science. You either accept the old-school supernatural, that one God created one universe by Design…and that‘s why it works; or you subscribe to a new supernatural: Eternal Inflation, a Happy Accident, etc. The choices are many. The only requirement for the new supernatural is that it be expressed mathematically. Extra points if the design has elegance.

  5. Robert L. Oldershaw

    There is an alternative that is able to retrodict the masses of subatomic particles at the > 99% level (including the electron) from General Relativity and the basic Kerr solution thereof, which relates the angular momenta and masses of the ultracompact objects.

    Papers: http://arxiv.org/abs/1002.1078
    http://arxiv.org/abs/1002.1078

    Also available at: http://independent.academia.edu/RobertLOldershaw

    Full discussion and resource for the new fractal paradigm called Discrete Scale Relativity:

    http://www3.amherst.edu/~rloldershaw

    No smoke, mirrors or gods required. Just basic physics and a new understanding of nature.

  6. Peter

    Dr. Oldershaw: The first question that comes to mind when reading your paper is, If there is a simple mathematical relation between particle masses, such as found in the Balmer series of emission lines, why hasn’t anyone noticed it before? The answer becomes obvious upon examining your Table 1, which does not go as expected, n=1, 2, 3, 4, etc. To begin with, the first four entries are for “fractional whole numbers” (n<1), and the electron is not included at all, perhaps because the closest “whole number n” corresponding to the electron’s mass is n=0.0278 (1/36). Secondly, there is no known particle for n=1. Thirdly, n=2 is used for more than one particle, as are several other n(s). Lastly, a lot of n(s) go unused, beginning with n=9, and quickly, the gaps between used n(s) become quite large. The reason no one has noticed the “mathematical pattern” you offer is because the pattern includes at least four extreme deviations from itself. There may be some justification for these “complications,” but they appear to be your design to dispense with a Designer, not an explanation of the observed particle masses.

  7. Robert L. Oldershaw

    If you are committed to a God-based paradigm for understanding nature, then I doubt that anything, and I literally mean anything, would persuade you to adopt a different worldview.

    The paper you mention starts with a fairly simplistic model, but in section 5 I show the reader a more sophisticated version of the Kerr-Newman model for particles.

    Did you not make it to section 5?

    This latter model retrodicts the masses of baryons more accurately than does quantum chromodynamics which is orders of magnitude more complicated and arbitrary.

    For those who want a slightly more accessible discussion of particle retrodictions, and one with graphs of the mass data, see New Development #2 at http://www3.amherst.edu/~rloldershaw .

    New Development #1 discusses a very promising retrodiction of the electron mass, which no previous theory has ever even attempted. The standard model of particle physics has no explanation for the value of the electron mass. Discrete Scale Relativity does.

    Fractional values are common in fractal models and common in nature, e.g., pi, the fine structure constant, etc. Fractals are exceedingly common in nature.

    If you are happy with "God made it so" as an explanation, fine. Scientists, on the other hand, want a less supernatural explanation of their cosmos.

    Robert L. Oldershaw
    Discrete Scale Relativity/Fractal Cosmology

  8. Donald E. Flood

    Theists have *other* reasons for believing in the existence of God:

    https://en.wikipedia.org/wiki/Miracle_of_Calanda
    https://en.wikipedia.org/wiki/Miracle_of_the_Sun
    https://en.wikipedia.org/wiki/Miracle_of_Lanciano
    https://en.wikipedia.org/wiki/Our_Lady_of_Zeitoun
    https://en.wikipedia.org/wiki/Pam_Reynolds_case
    https://en.wikipedia.org/wiki/1_Corinthians_15?
    https://en.wikipedia.org/wiki/Januarius#The_Blood_Miracle

    However, the fact that the Standard Model seems "rigged" is consistent with the existence of an Infinite and Perfect Being.

  9. Mario E. de Souza

    THE STANDARD MODEL CANNOT BE THE LAST WORD BECAUSE THERE ARE A NUMBER OF QUESTIONS THAT IT DOES NOT ANSWER. For example, four very important open questions are the proton spin puzzle, the EMC effect, the distributions of electric charges inside the nucleons as found by Hofstadter in 1956, and the ad hoc CKM matrix elements.
    Please, take a look at the following papers for a deeper understanding of the matter (all are available by means of Google):
    1) Weak decays of hadrons reveal compositeness of quarks;
    2) The Higgs-like bosons and quark compositeness;
    3) The Higgs-like bosons couplings to quarks

    Dear Robert L. Oldershaw, the Standard Model Higgs boson is a God-given boson.

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