Saturday, July 21, 2012

Relative strength of HEP experiments, phenomenology, theory

A few years ago, the experiments at the LHC were getting started. Decades of thirst for the new experimental data – started especially by the sour 1994 U.S. Congress' decision to abolish the 40 TeV Superconducting Supercollider – were superseded by a new era producing lots of data.

The 126 GeV Higgs boson is the most concrete new result coming from this recent exciting activity. But we shouldn't forget that the LHC's confirmation of hundreds of predictions by the good old Standard Model is incredibly impressive, too.

The first anthem of students of high-energy physics, Russian chanson Marsh fizikov (The March of the Physicists), was composed in 1964 (the year of the Higgs boson papers) and sung by Vladimir Vysotsky, an unofficial yet immensely famous Soviet songwriter with some dissident links. Paradoxically enough, we received a book with his lyrics in 1988, when we were 15, as a gift to guarantee that we would join the Socialist Youth Union, SSM. I took the book but didn't join because I was not obliged to obey unwritten rules of corruption despite its being common in the criminal organization.

The expectation of the meaningful experimental activity was reflected in the job market, too. Experimental groups hired new people and they assured everyone that there was some work for them to do. Among the non-experimenters, almost all the new hires went to phenomenology – they hired people who were able to professionally analyze the data coming from the LHC (and other ongoing experiments).

Just to be sure, people in particle physics or high-energy physics (HEP) may be loosely divided to three groups – experimenters, phenomenologists, theorists. The boundaries are not sharp; you may consider these three labels to be specific colors on a continuous rainbow. But a quantity loosely dividing people into these groups surely exists and the classification above is widely used by the high energy community itself.

The classification was invented in the early 1990s by Paul Ginsparg when he was creating his famous archive of electronic preprints, – today, we use the modern URL, Ginsparg wanted to make fun out of several things. So when he moved his activities to the web around 1994, WWW in the URL was replaced by a funnier acronym XXX. This funny acronym made it impossible for many physicists to access papers from the airports because many airports simply don't allow you to open XXX websites.

Ginsparg, a very well-defined formal theorist or string theorist at that time, also wanted to make fun out of those theorists who wanted to stay away from formal theory and string theory and from very deep and ambitious questions and from unification of all forces and who primarily wanted to remain as close to experiments as possible.

In other disciplines than high-energy physics, people would still use the term "theorist" both for what we call theorists and phenomenologists in high-energy physics. If you're a scientist but you're not the guy who actually performs the experiments, you're a theorist, they would say in other fields. But because the polarization of "theorists" and "phenomenologists" looked rather strong in high-energy physics, Ginsparg simply created two archives, hep-th and hep-ph, and this Velvet Divorce was a wise choice (despite many people working near the boundary and many papers crosslisted to both archives). He also invented the funny name, "phenomenologists", for those theorists who don't really want to develop new theoretical concepts and who are more concerned with the application of existing theoretical concepts to the experiments. Model builders are a subset of phenomenologists who work on the construction of new models (the rest works on not-quite-understood manifestations of well-known theories) – but they're not supposed to be models that are "totally conceptually new" or "theories of everything". They're supposed to be "just another possible step". All phenomenologists work in the framework of quantum field theory; once you really take string theory seriously and use its mathematical framework as well, you're a full-fledged theorist.

If you look at the Wikipedia's definition of phenomenology, you may start to laugh and appreciate how witty Ginsparg's naming scheme was. Why? While the word "phenomenology" is derived from "phenomena" so that particle physicists may naturally imagine that it's connected with tangible, material things, the word "phenomenology" has actually been used exactly with the opposite connotations in many other fields of human activity.

In philosophy, "phenomenology" is linked to Edmund Husserl who thought that the most important thing for philosophers to study are "phenomena". But he didn't mean natural phenomena; instead, what he had in mind were phenomena (as well as "noumena") resulting from consciousness. This stuff is full of occult references to sensibilities, emotions, and their existence that is supposed to be independent of the material carriers.

In theology and psychology, "phenomenology" is all about the subjective perceptions, too. I don't know what all those people study but it's clearly some spiritist flapdoodle whose intersection with scientifically meaningful entities is almost certainly empty. In architecture and archaeology, "phenomenology" is a related weird theory about places' having their own spirits that are correlated with ill-defined mixtures of the physical properties of the places. I won't even try to understand what these people could be talking about. ;-)

But let me return to the main topic.

I believe that the redirection to experiments and phenomenology has already been overdone. It's really great that the Higgs boson has been discovered but one didn't really need 10,000 experimenters for that. Moreover, one must be ready for the possibility that the Higgs boson is the last new thing that the LHC will observe. This scenario surely can't be ruled out. If this scenario turns out to be true, we will quickly see that there are way too many people employed to study certain particular aspects of Nature that are modest or don't exist.

And in this context, I mean both experimenters and phenomenologists. The phenomenologists' preference for questions that may be addressed by contemporary experiments may look very intriguing – many people like tangible things – but it has an obvious flip side. If you're focusing on things that are accessible and hot in 2012, chances are high that they will no longer be hot and important in 2013 or later. Whether you like it or not, most of the work in phenomenology has a lower lasting value. The fact that those ideas are partially "fads" that quickly fade away (at least most of them) is completely inseparable from their being relevant for currently doable experiments.

So a vast majority of the particular models with some preferred choices of parameters that had been proposed as a solution to the hierarchy problem has already been falsified. Almost all others – with at most one exception – will be falsified in the coming months and years. If you assign a price to a model builder's paper, this really means that the price drops to zero once the model is falsified. Unless the person finds the right new model; no one has succeeded in this task after the fathers of the Standard Model.

Only if a paper transcends some particular technicalities that are identified as valid or invalid by experiments, it may have a lasting value. A paper with a lasting value must contain some new and intriguing enough ideas or methods or theorems or new tools or new concepts that are independent of a particular technical implementation of these ideas – implementation that is usually quickly shown not to be relevant for Nature around us.

Needless to say, the concentration of such ideas and insights is much higher in the formal theoretical papers – in papers on string theory and perhaps also some others. The amount and the penetration factor of deep insights with a lasting value that were found by string theorists in recent decades is staggering.

Even though we are in the middle of the exciting LHC era, everyone should start to appreciate the simple and self-evident fact that the LHC won't give us the answers to all open questions in physics. High-energy physics will keep on living after the LHC and a thread of its life that will probably regain its dominance in a few years is firmly rooted in theory.

That's why I think it's important for places not to become giant LHC bubbles and to start to hire many theorists again.

And that's the memo.


  1. You have given me a platform for my favorite observation/proposal as far as research goes, and not only particle physics research.

    I think the way that research is being financed with grants from centralized bureaucratic agencies who have an interest to support their jobs is destroying science as my generation knew it. Climate "science" is a clear case in point, and I have pontificated on that at . But the plight of theorists is also a byproduct from this gross centralization of financing.

    My belief is that until financing returns to the universities and institutes this trend, of people like Mann who can bring grants to universities by personality cults, having power and support, will go on. The money should go to the universities and institutes and internal to each institute peer review should distribute it. Thus theory departments would get a chance at the money and have a possibility of hiring assistants and starting grade professors, as it used to be long ago.

    In the case of HEP the group leaders have to dance a dance of grants, and to get them they need phenomenologists, not theorists as you define them, because the number of papers and the "application" orientation is very important for central financing agencies.

    The whole discipline has been commercialized by this method. Universities instead of hiring excellence in research value excellence in bringing grants, and how much money can a theorist bring?

    A second by product of handing back the financing to universities would be the healthy competition of schools of thought, different in different universities. The climate "science" debacle (the science is settled) would never had happened if it were not for grants and bureaucrats.

  2. Thanks for the arxiv history---I have always thought of Paul Ginsparg as a true hero for setting it up and managing it. He has likely done more for physics and math and other disciplines than he ever will get credit for. When I find an interesting paper somewhere and try to access it in say, Phys Rev, and can only read the abstract, the paper usually (often) has appeared on the arxiv. Also, papers often go up there quickly in order to establish priority.
    I did not realize that he was the originator of "phenomenology" in physics. I remember asking Lubos about this when Lisa Randall referred to herself as a phenomenologist and I thought "WTF does this have to do with Edmund Husserl and philosophy?":)
    As for the LHC, imo it will find more, but it is a noble monument of our civilization much like the Great Pyramids.
    Unfortunately, if , say, the LSS particle isn't found, the usual group of media whore physicists will be saying that therefore supersymmetry is dead, not that it is inaccessible at these energies.
    Lubos: Do I detect some weakening of your belief in supersymmetry reading between the lines, or am I overanalyzing? WRT Nima, he strikes me as an idea generator---sparking all sorts of thoughts and theories---these guys are fun. That must have been what Sidney Coleman was like in his earlier active days.

  3. Dear Gordon, it depends what you compare the current confidence with. Relatively to 2007,

    my confidence that SUSY is right has increased. At that time, I wrote 70% for SUSY at the GUT scale or lower. I don't know if I were serious and thinking. This number seems low to me today. I would answer 95% to this question today.

    Whether SUSY will be found by the LHC was 50% at that time, it is 55% today. My belief has been stronger than that, up to 70% or so, at some points two years ago or so. It has decreased of course primarily as the result of the tighter exclusions - from 70% to 55%. I have explained several times what is the Bayesian logic showing that the tighter exclusions only have a minor impact on the odds.

    So unless you are interested in subjective tiny nuances of a single person, the answer is obviously No, nothing has significantly changed about my confidence in supersymmetry. And I still surely consider people who reject SUSY at any scale, even the Planck scale, to be hopeless cranks.

    Yup, Nima is an idea ventilator. ;-)

  4. Note that besides there was also, paying hommage to spin chains.

  5. Yes thanks for this expose Lubos.

    Your comment about criminal organizations is all you know so you will speak from that experience? What you do in your blog has nothing to do with any criminal organization but more to what benefits you give other people when you explain and bring them forward in their knowledge. That is sharing. That sharing is not communism. That sharing is not the left. That sharing is not a polarization of political attributions?

    When you have "wealth of knowledge" do you discriminate against who shall receive it and who shall not? Do you have certain requirements for people reading what you say?

    Would you say then that a poor man is a lack of knowledge? That you would discriminate him about receiving your knowledge?

    It is no longer feasible for such polarizations to exist. It's time to come of age?:)


  6. Dear Plato, one may be poor or rich in various ways. Not sure what is the best wise reply to these general thoughts of yours.

    Writing a blog is surely a different thing than being a member of SSM (Czechoslovak Komsomol). Just to be sure, my classmates in SSM did lots of innocent fun I missed - like social life while repairing a castle near Pilsen. ;-) Still, SSM was a criminal organization whose goal was to keep teenagers in line and reshape them into obedient adults who will de facto support the totalitarian regime.

  7. Dear Plato, I've just realized why I prefer religion to philosophy : forgiveness is guaranteed ;-)

  8. Nothing better then a good theory, particularly when supported by an experiment. Otherwise it is just a theory, and as we all know there are at least 10^(24) or more of those. From experimental point of view, an interesting paper from CMS - from the latest CMS analysis summary it appears a fermiophobic Higgs boson in diphoton decay mode is excluded with 95% LC between 110-127 Gev, and for the state found near 125 GeV at 99% CL.

  9. Dear Lumo,

    your description of some history of the arxiv is very funny, it made me chuckle a lot :-D

    I just hope that your prediction that HEP (or fundamental physics) will stay alive after the LHC (in particular if nothing else apart from the higgs is seen) and theoretical research will be strenthened is right ... You know, the number of evil sourballs, which are very loud and impertinent already now, would certainly not decrease if such a (from the scientific point of view NOT bad ;-) ...) scenario came true. And they would be not less determined to destroy (theoretical) HEP than they are now ... :-/
    But I hope the best and that decisions about funding science etc will be made by more reasonable people than in the US :-)

    Ginsparg's classification of HEP papers in the arxiv is very useful for me too :-D... :
    Following a TRF link to a HEP-TH paper I usually only dare to read the abstract, in a HEP-PH paper I can look at the figures and read the corresponding captions too, and looking at a HEP-EX paper I can even consider to in addition read the introduction and the summary .. :-P

    (Joking and teasing Lumo a little bit to alleviate the seriousness of the second paragraph of my comment ;-) ...)

  10. My experiments as a siltitarian did not go over as well as originally anticipated. I am converting to Gravolitarianism.

  11. Hi Lubos,

    Thank you for being thoughtful.

    I have share stories with others of similar backgrounds and I kind of understand the oppression one might feel to conform....but you are free.

    Republicans, like factions of my government would seek to portray a genuine irresoponsibility with phrasing of and about the left as an ideology that is reminiscent of your experiences.

    I really think that if we can take care of all parts of the society , those who are sick of equal and endearing rights to the same level without answering to profiteering that goes on with regard to that healthcare, I would call that equal justice under the democratic rights of one's constitution.

    Would it be right that factions of the criminal organization accepting the red, green book, what ever guise it extolled of itself, would allow you special advantages being of the party and a comrade?

    Hardly. Shall I be called the left or right when it comes to seeing society brought forward under the wealth of information at our finger tips. How ignorant I shall remain.


  12. Sorry, I am facing my own kind of hopefully likewise society will have graduated from the "religious experience" and maybe even learn to use philosophy to get on the right track with regard to the science?

    Lubo's whole post here is a good lesson.


  13. Steven Wolfram can make me a sandwich.

  14. Which philosophy though ? Some of them are so different from each others. The main religions do integrate Science and its discoveries into their faith. Philosophy gives an interpretation of Science, but is it the Truth ? :-s (just pondering ;-)...)

  15. Dear Dilaton, the proposition that "HEP will stay alive" wasn't really a prediction. It was an assumption. I couldn't even think of the possibility it would be false. This would mean the beginning of a complete decay of the humanity. I would prefer to declare the civil war against all those who would encourage such a trend.

    Haha, yes, hep-th papers require the deepest expertise...

  16. Yep,
    in such a civil war I`d like to handle the photon torpedos to blow away the sourballs ... !

  17. Jep,
    in such a civil war I`d like to handle the photon torpedos to blow away the trolls ...!