Part 5

This Monday at the Institute was busier than anytime in the previous week, tripling the traffic in the hallways and the length of the line to the espresso machine, in preparation for the four-day conference nestled within the larger month-long workshop.  My talk had been snuck in just before this conference, producing an auditorium comfortably filled with physicists, and the first time I had presented to an overwhelming majority with research interests outside of my own area of burgeoning expertise.  Nevertheless, lacking the requisite discoveries for interpretation, discussions had pivoted to introduction of new analysis techniques motivated both by the unmatched volume of data to be collected by the experiments at the LHC and their exquisite highly-granular resolution that captured the most detailed images of the subatomic world in history.  Though speaking a rather different language than the fluency of others in new physics signatures from supersymmetry, say, there was interest in my subfield far and wide in particle physics, with what seemed like everyone hitching themselves onto some collaboration to explore novel ways of looking at collider events from this lens that was now just over three years old.  Riding this wave of enthusiasm, I stepped up to the desk brandishing a laser pointer and owning the next hour to persuade the audience that the bounty of phenomena that could be studied was ever richer.

Given just a bit of intellectual stimulation from, say, a course on quantum field theory, graduate students think that they soon know everything but also that everyone else knows everything that they do.  Presentations relatively early along one’s journey to the Ph.D. typically lack motivation as everyone knows why something is interesting and dive much too quickly and too deep into jargon, which is anyway often misapplied by the student who only heard of the terms a month ago and could still not define them to non-physicist family members, let alone their fellow students. A rather large part of one’s education in graduate school is in the wading through and crawling out of this morass, to develop a broader understanding of what is known, who knows it, and how to communicate it to a broader audience, all of which cumulates of course in the thesis defense.  Now in my fifth year, I had at least acquired a healthy collection of humbling experiences, whether or not I learned from them, but this would be my first real test.

From the third row came a question about the feasibility of calculations, first-principles predictions of these strange new quantities that I was describing, and if such calculations could be compared to experimental data.  We had only done a study on simulated data which, while impressively accurately reproducing the physics in honest data collected by experimentalists, is not the same as a calculation, something that you the theorist completely control and understand all approximations that are employed in producing a result.  So all I could do was mumble that yes, these observable quantities are calculable and that their performance on simulation motivated doing so, which was met with curt nod, a contemplative frown, and an extended whispered comment to their neighbor while I continued.  After the final slide, there were a few more questions here and there from people who wanted to know how this hammer would work with their nail, to which all I could respond was a reiteration of the points made in the talk, that this technique was designed to isolate the physics of the background and that the physics of their signal sounded rather distinct.  Over espressos, my seated neighbor, a senior theorist just arrived in Florence from his home institution of Fermilab, noticed who I was enough to thank me for the nice talk, and back in our office, my collaborator and roommate for these two weeks picked apart the answers to the fielded questions, but remained silent about my presentation.  That seemed good enough to give myself a passing grade.

400 years ago, the data were there, Tycho Brahe’s unrivaled astrophysical records, Johannes Kepler’s first quantitative relationships of planetary motion, and Galileo’s direct observation of new heavenly bodies that neither orbited the Earth nor the Sun, and the problem was to establish the simple, organizing principle to describe all of it logically, to cast off millennia of magic and mysticism.  The centuries that followed definitively transformed these enlightened, humanist endeavors from the nebulous realm of natural philosophy to rigorous, empirical physics. Increasingly, predictions required revolutions in pure mathematics for their formulation, from the Hookeian and Newtonian inverse square law of universal gravitation, to giant leaps away from forces and toward Lagrangians and Hamiltonians that marked baby steps to quantum mechanics, to finally Einsteinian relativity which is and has remained the most wide-reaching and powerful language of the universe’s dynamics at large.  This unbroken scientific lineage, from the early apostles to its contemporary priesthood, still plumbs its depths for riches and ever draws up surprises preventing stagnation and dogma, producing new paradigms from black holes, to dark matter, to accelerated cosmic expansion, the new mysteries to be understood.

This week as representing a selected sample of particle physics was nearly a perfect mirror image, inverted left to right, with opposite problems of data and theory.  The theory of particle physics as encapsulated in the Standard Model was effectively complete in the 1970s, and since some details have been added, masses of discovered particles and the like, or its predictions shored up with increasing precision.  Simply knowing the equations of nature does not mean that one knows all of its solutions, so many surprises have popped up along the way, though only, again and again, to be observed in experiment exactly as predicted.  Naturally, some gaps have been identified between observations and theory, though our increasingly sophisticated mathematical formulation enables an immediate remedy or patch that is sufficient for current experiments and can be improved in the future.  The lynchpin of the Standard Model was the Higgs boson, now approaching its 50th theoretical birthday though yet to be delivered in the data, but this was merely a matter of time, as its gestation in the LHC was surely to complete soon and already there was gossip that telling bumps had been seen in the most important plots.

Theorists, instead of called on to unify an embarrassment of experimental riches, were set to questioning the mathematical edifice of the entire field, seeking in the cracks and crevices for something, anything, that seemed awry, that had not been sufficiently tested and validated in the past.  The focus had turned most narrowly on the Higgs itself, not if it existed which was a given, but rather on if it actually was consistently described within the Standard Model.  The Higgs is an outlier out of all the known fundamental particles, the sole particle that has no spin, completely featureless under rotations, and for those with a predilection to pessimism can be seen as an unassailable complication.  The optimist’s natural solution was then to look beyond the Standard Model, for more and more exotic fields and particles and mechanisms that left experimental signatures, things like extra dimensions of space or symmetries that inextricably connected the known to a novel unknown, which gave experimentalists an ever increasing list of theorist’s laundry to search for.  The experimental update talks this week were more and more bounds, 95% confidence that nothing like the theorists’ collective imaginings existed, but ever onward went theorists, countering with talks of their own with another theory beyond the Standard Model that just, conveniently, technically, evaded these bounds.

This miniature conference’s banquet was a kilometer further up and into the hills south of Florence, a short pilgrimage along the serpentine roads that were by now late in the day devoid of traffic except for our dozens-numbered group, utilizing the entire space that lay between the stone walls.  Mid-week, the trattoria was empty too, and we ducked under salami, fuzzy white with penicillin and suspended from the ceiling by thin ropes, and passed into the dining room, half of which was usual four-tops sprinkled about and in the other half was set two rows of tables extending from the entrance stairs to the broad windows.  Wine was poured and mingling continued with most gathered around the twilit view, set at the top of an olive orchard, and far to the left and right, the arms of the ridge-top framed the scene, with its fingertips capped with sandstone villas hidden amongst the cypress and crowned with terracotta tiles.  Gently encouraged to both find a seat and to top off our neighbor’s glass in preparation for the antipasto, our hosts had gathered at the far end of the table to lead us in a toast, a secular, scientific prayer, to be sent forth from the week of conversations and arguments and insights and out into the world.