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Byron Jennings | TRIUMF | Canada

View Blog | Read Bio

The Trouble with Particle Physics*

Ya got trouble, my friend, right here,
I say, trouble right here in River City.[1]

What is the current trouble with particle physics? That’s an easy one: a paucity of new experimental results that challenge the status quo. In contrast, in the past twenty years, cosmology has surged ahead, fueled by the new results from COBE, WMAP, Hubble, and other novel devices. Yet that field may now also be reaching the point of diminishing returns. Without new experimental results any field stagnates. But before addressing this in more detail let’s look at some other suggested problems with particle physics.

One of the criticisms of particle physics is the large size of the collaborations. Well that is just the nature of beast. To probe short distances we need large machines. They are expensive and require large collaborations to build, operate and maintain. Being a successful member of a large collaboration requires, in part, a different skill set from that for tabletop science.  It relies much more on social skills and no one is required to be a jack-of-all-trades as different members of the collaboration can specialize in different areas. While the skills required may be different they are still as useful to society. The World Wide Web grew out the need for particle physics to collaborate widely. While particle physics still has the largest collaborations, other fields are also moving in that direction. The collaborations need to build and launch satellite observatories are also large. Even nuclear physics is moving towards large, long time span facilities. While still not in the same league as the ATLAS detector at the LHC, the TIGRESS detector at ISAC (TRIUMF) took seven years to build.

Other problems were suggested in Lee Smolin’s book The Trouble with Physics. (It should have been called The Trouble with Particle Physics since it only dealt with that rather small – important but small – part of the totality of physics.) One of his points was that there is too much herd mentality in the field with too many people working on, for example, string theory. To some extent this is a valid objection. Science works best when a variety of different approaches are explored.  However, science is self-correcting and trying to impose diversity from the outside is doomed to failure.  When there are too many people in one area they sooner or later realize this and some move on. People moving on is the only sure sign that there are too many people in a field. Indeed, this is starting to happen in string theory and will probably turn into a stampede when (hopefully not if) the LHC finds surprising new results. He also suggested that particle physics needs more theorists thinking deep thoughts. In my humble opinion, that is the last thing we need – more navel-gazing theoretical particle physicists and this from a long time navel-gazing theorist. What we need are more experimental results so the theorists have something more interesting to gaze at.

Why the shortage data? Two reasons: The first is not really a shortage of data but a shortage of challenging data. The standard model of particle physics is just too damn (am I allowed to say that?) successful. The detectors at the Large Hadron Collider (LHC) are starting to churn out data but to date nothing earth shaking. Essentially all tests of the standard model have failed to find anything new, at least at a convincing level. The one possible exception to this is neutrino physics with the underground detector systems. Whether this is an exception depends on how you define the standard model. Independent of that, the neutrino mass and mixing measurements have added excitement to the field with a number of new results, for example the neutrino mixing angle, θ13, from T2K and Double Chooz.

The second reason is the size and time scale of particle-physics projects. For example the LHC has taken more than 15 years from conception until it will produce it first interesting results. T2K has taken a shorter time but it is still many years. The long time scales mean that the exciting new results tend to happen infrequently and the large size also precludes doing things in parallel. This is worrying as it makes independent replication difficult. We have only one large hadron collider. A second was planned but cancelled due to the cost.

A new accelerator, the International Linear Collider (ILC), has been planned and worked on for some time. In 2000, I was assured that by 2006 the construction would have started. The best-laid schemes o’ mice an’ men. Gang aft agley[2].  It has not happened. When it will happen is anyone’s guess. Funding a large accelerator project in the current financial situation is going to be tricky.

So LHC, we are relying on you – no pressure or anything. If the LHC finds the Higgs and nothing unexpected, particle physics will be in tough shape; the dark comedy referred to in the footnote. We have the standard model, which is widely believed to be incomplete, and without unexpected results we have no clue how to go beyond that model – maybe the universe really is fined tuned to many decimal places. Theorists are doing their creative best, but are spinning their wheels. What we need is data to reign in their imaginations.

Not finding the Higgs would be better (except for the public relations disaster) but even then we would need further experimental indications for what went wrong in order to progress. The best result would be herds of unexpected new particles; barring that, finding particles moving faster than the speed of light would do just fine. Then the trouble with particle physics would be over.

Additional posts in this series will appear most Friday afternoons at 3:30 pm Vancouver time. To receive a reminder follow me on Twitter: @musquod

* Not be confused with Hitchcock’s 1955 black comedy: The Trouble with Harry. However, depending on how it turns out, it may indeed be a black comedy.


[1] From the 1963 movie The Music Man.

[2] To a Mouse by Robert Burns

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9 Responses to “The Trouble with Particle Physics*”

  1. Kea says:

    Wow, you don’t know much, do you …

  2. Mitchell Porter says:

    Theorists have plenty to do already. There is the Koide relation and its various generalizations. T2K seems to have confirmed quark-lepton complementarity for all three mixing angles. None of this is getting remotely adequate theoretical attention.

    • Byron says:

      The orignal Higgs paper was almost 50 years ago and the upending of SU(5) was about 25 years ago. No amount of theoretical deep thinking has confirmed the existance of the Higgs boson nor told us what the replacment, if any, for SU(5) is. We need experimental data and I will stick by my claim that particle physics is suffering from a lack of challaging data. There are certainly some hints of physics beyond the standard model, the most notable being the matter – antimatter asymetry in the universe and dark matter. Both of these issue will require more experimental data to elucidate. The matter – antimatter asymetry may be resolved by neutrino experiments; dark matter by the LHC and underground detectors.

      As for the Koide relation it may be profound or it may be numerology. Only more data will tell.

  3. Walter says:

    One can’t see something if he is not looking for it. Not with the detectors around the LHC.
    Those detectors have clear defined conditions which particles have to do what for an event to be considered worthy the logging and later analysis.
    Those conditions are based on the standard model, they are tailored to check some small facets of this model.
    If something unexpected (“new physics”) happens, nobody will ever see it because those events are not recorded.

    There could be a dragon walking through the detector, it would not be seen because nobody told the detector to look for dragons.

  4. Bee says:

    Leaving aside the issue of the “deep thinkers” (I strongly doubt “navel-gazing” is what Lee had in mind), the book isn’t really about physics, and certainly not specifically about particle physics, that’s just an example that the author is for obvious reasons familiar with. The main point is that the current mechanism of resource allocation in academia is strongly affected by sociological effects, which leads to an inefficient use of resources.

    That’s the case not only in physics, but even more pressingly so in medicine, chemistry, economics, and that’s only to mention those areas where I’ve talked to people. The problem is that scientific opinions are skewed by external pressures, and scientists are hindered in changing a research topic after a once promising field has run out of steam. You’ll know for yourself it is virtually impossible to change even a subfield after the first postdoc because nobody will give you a job where you have to spend time learning the basics and you don’t have any publications to show up when you apply.

    I have written about these problems many times. Maybe best here.

    • Byron says:

      Lee unfrotunately did not have navel-gazing in mind but that is what kept coming to my mind as I read about his “solution”. Science is ultimately observational and Lee discounted that too much. He also had an unfortunate tendency to use science, physics and particle physics interchangably in places where it was inappropriate.

      Herd mentality is a problem since people are social animals. The tradeoff in funding decisions is between too much herd mentality and too much crackpottery. Every crackpot claims to be the victum of herd mentality. Getting the balance right is indeed a problem and getting it correct all the time is probably impossible. But let us be clear, crackpots do exist and have the potential to do a lot of damage.

    • Byron says:

      A few more thoughts. I have changed sub-fields several times in my career. First on completion of my Ph.D, second after four years of post-docing and again when I obtained a permanent job. I have changed sub-fields several times since then and most recently, I have changed fields and went from research to administration. So I do not know that it is impossible to change sub-fields. In my case it has been rather easy.

  5. Mitchell Porter says:

    I should add that I first heard about Koide and QLC on Kea’s blog. So as a theorist currently receiving zero financial support, she especially has reason to scorn the view that there is “a shortage of challenging data”.

    • Kea says:

      Yeah, shortage of challenging data my ass … how about we start with (all to do with particle physics) LHCb CP violation, no fairies or sparticles or positive results from LIGO, non-WIMP like scenarios for DAMA/CoGent (eg. neutrinos), primoridal BH confirmed predictions for the WMAP omega parameters, coincidence with quark-gluon plasma parameters via AdS/CFT, MAGIC etc, a host of anomalies in neutrino oscillation data, HE cosmic ray results, PAMELA positron excesses, FTL neutrinos, …

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