Transpositions [TP]: Case Study 2

deep inelastic scattering

Common Muon and Proton Apparatus for Structure and Spectroscopy (COMPASS) experiment at the European Organization for Nuclear Research (CERN), Geneva.

Scattering describes the process in which a particle with high energy called a beam collides with another, the target. In the deep inelastic scattering the energy of the beam is so high that the target breaks apart, revealing its constitutive elements. Usually, in physics, the collection of the smaller, potentially simpler, parts that something can be broken into is said to be its "spectrum". This is very much like speaking of the spectrum of a sound when we calculate which sum of single frequencies it is equal to.

At the COMPASS project at CERN, physicists are interested in observing and understanding the characteristics of the spectrum of the proton, a primary building block of atoms and of all the matter with which we can interact. A very high energy beam of elementary particles called muons (a type of heavier electron) collides with the target protons that breaks into its spectrum, the quarks. These spray into the 50 meter long spectrometer, where they cause effects which can be detected.

In opposition to the somewhat childish but seemingly effective strategy of analysing something by breaking it into pieces to see 'how it works', in this case the products of this breaking apart actually remain ineffable. This touches the very essence of the problematic mode of existence of the quantistic world, bound to remain in a state of spatial and temporal uncertainty. To illuminate how the indeterminacy of these processes seems to infect the whole apparatus of the COMPASS experiment is the focus of this case study. We intend as 'apparatus' not only the spectrometer as a measuring device, but the whole aggregate of scientific theories, technical tools and social interactions in which the experiment is embedded. In particular we observe how the "reconstruction" process, mediated by multiple steps of re-interpretation and interpolation of the data, is not only a necessary step of analysis, but also a generative transformation which produces new forms.


We are provided with data containing approximate time and position of detected particle passages through the detector. These space-time positions are called hits. A set of hits is contained in every detected collision event, recording the passage of the fragments of the broken proton. Our data set contains thousands of these events.

We are left alone with this material, a collection of points placed in a four dimensional space that is mostly void. To bridge the gaps and navigate through the emptiness, a rule of relationship is inferred; a rule of "causality" defining which points are interdependent with each other. This rule is an assertion, emerging from of the uncomfortable situation of not knowing where and when things are. It results in a function which joins points, interpolating between them, structuring a space: its reiterated application is a generating function that produces coherence and form. 

The transposition constructs figures as well as finding them in the material to which it is applied. Therefore, even if it is an isomorphism, its action is not neutral: this characteristic —which affects all transformative functions — becomes evident when it departs from canonical i.e. accepted interpretations of what lies "behind" the data, or how it should be read.

Each hit is connected with a line to the nearest other along each of the 8 directions in the four dimensional space-time. The process is repeated for each event. 

Eventually a series of thousands of figures are drawn which collect the traces of the application of this function of the data. 

This is the projection of the x-t plane of the figure generated for the event 5252 in spill 198.


Our experience of working together with CERN's researchers bears some particularities. 

The utter specialisation and compartmentalisation of the research causes an extreme fragmentation. As with the fragments produced by the collision events, it is difficult to get a hold on concrete and definitive statements. In conjunction with the marked competition between the different research groups and even within the same group, the reconstruction of how analysis and interpretation processes are used, and what significance these have on the data, is too complex a task. Most data conditioning and analysis algorithms are used as black boxed functions by the researchers.

The spatial and temporal sensibility of the instruments, which are almost required reach into Heisenberg's uncertainty regions of space-time, seem to drag not only the instruments' themselves but also the research more generally into a grey zone of existence: it seems impossible to know exactly the wheres and whens of things. Included are, for example, the positions in space and time of the particle collisions passages, the positioning of same detectors within the spectrometer as well as the organisation of the research.

Uncertainty and abstractness are not only a quality of quantistic processes, they permeates every dialogue. Extreme caution is taken in order to avoid formulations which might reveal too much confidence. 

Only a statistic of inquiries will produce a measurable response.

The impression one gets is that the qualities of the phenomena effect the ways of thinking and working of the researchers studying them.


COMPASS (Common Muon Proton Apparatus for Structure and Spectroscopy) transverse data taken in 2004 at CERN, 160 GeV polarized muon beam coming from SPS and scattered off a 6LiD target, first 100 scattering events with a total of 119.591 detector hits. Inscribe a model of the COMPASS spectrometer in the large basement room of the DA TA rush research event at the Angewandte Innovation Lab (Vienna, May 2016). Focus on the temporal signatures of detector hits. Complicate situation through conceptual and acoustic means. Create a situation in which the temporal aspects of the scattering events taking place in the spectrometer can be made sensually accessible and explorable, referring to some aspects of the detectors' physical materiality. The main materials of the spectrometer (iron for structural components and copper for electrical components) are reflected in the installation. The complications of the physics created with the spectrometer are reflected in the convoluted acoustical situation.

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