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Register a new userTouschek with AdA in Orsay and the first direct observation of electron-positron collisions
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Giulia Pancheri Dr.
Publication date
2018
fields
Physics
and research's language is
English
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We describe how the first direct observation of electron-positron collisions took place in 1963-1964 at the Laboratoire de lAccelerateur Lineaire dOrsay, in France, with the storage ring AdA, which had been proposed and constructed in the Italian National Laboratories of Frascati in 1960, under the guidance of Bruno Touschek. The obstacles and successes of the two and a half years during which the feasibility of electron-positron colliders was proved will be illustrated using archival and forgotten documents, in addition to transcripts from interviews with Carlo Bernardini, Peppino Di Giugno, Mario Fascetti, Francois Lacoste, and Jacques Haissinski.
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In the history of the discovery tools of last century particle physics, central stage is taken by elementary particle accelerators and in particular by colliders. In their start and early development, a major role was played by the Austrian born Bruno Touschek, who proposed and built the first electron positron collider, AdA, in Italy, in 1960. In this note, we present a period of Touscheks life barely explored in the literature, namely the five years he spent at University of Glasgow, first to obtain his doctorate in 1949 and then as a lecturer. We shall highlight his formation as a theoretical physicist, his contacts and correspondence with Werner Heisenberg in Gottingen and Max Born in Edinburgh, as well as his close involvement with colleagues intent on building modern particle accelerators in Glasgow, Malvern, Manchester and Birmingham. We shall discuss how the Fuchs affair, which unraveled in early 1950, may have influenced his decision to leave the UK, and how contacts with the Italian physicist Bruno Ferretti led Touschek to join the Guglielmo Marconi Physics Institute of University of Rome in January 1953.
Bruno Touschek was an Austrian born theoretical physicist, who proposed and built the first electron-positron collider in 1960 in the Frascati National Laboratories in Italy. In this note we reconstruct a crucial period of Bruno Touscheks life so far scarcely explored, which runs from Summer 1945 to the end of 1946. We shall describe his university studies in Gottingen, placing them in the context of the reconstruction of German science after 1945. The influence of Werner Heisenberg and other prominent German physicists will be highlighted. In parallel, we shall show how the decisions of the Allied powers towards restructuring science and technology in the UK after the war effort, determined Touscheks move to the University of Glasgow in 1947.
We describe the road which led to the construction and exploitation of electron positron colliders, hightlighting how the young physics student Bruno Touschek met the Norwegian engineer Rolf Wideroe in Germany, during WWII, and collaborated in building the 15 MeV betatron, a secret project directed by Wideroe and financed by the Ministry of Aviation of the Reich. This is how Bruno Touschek learnt the science of making particle accelerators and was ready, many years later, to propose and build AdA, the first electron positron collider, in Frascati, Italy, in 1960. We shall then see how AdA was brought from Frascati to Orsay, in France. Taking advantage of the Orsay Linear Accelerator as injector, the Franco-Italian team was able to prove that collisions had taken place, opening the way to the use of particle colliders as a mean to explore high energy physics.
We present the framework for obtaining precise predictions for the transverse momentum of hadrons with respect to the thrust axis in $e^+e^-$ collisions. This will enable a precise extraction of transverse momentum dependent (TMD) fragmentation functions from a recent measurement by the Belle Collaboration. Our analysis takes into account, for the first time, the nontrivial interplay between the hadron transverse momentum and the cut on the thrust event shape. To this end, we identify three different kinematic regions, derive the corresponding factorization theorems within Soft Collinear Effective Theory, and present all ingredients needed for the joint resummation of the transverse momentum and thrust spectrum at NNLL accuracy. One kinematic region can give rise to non-global logarithms (NGLs), and we describe how to include the leading NGLs. We also discuss alternative measurements in $e^+e^-$ collisions that can be used to access the TMD fragmentation function. Finally, by using crossing symmetry, we obtain a new way to constrain TMD parton distributions, by measuring the displacement of the thrust axis in $ep$ collisions.
Sources of high-energy photons have important applications in almost all areas of research. However, the photon flux and intensity of existing sources is strongly limited for photon energies above a few hundred keV. Here we show that a high-current ultrarelativistic electron beam interacting with multiple submicrometer-thick conducting foils can undergo strong self-focusing accompanied by efficient emission of gamma-ray synchrotron photons. Physically, self-focusing and high-energy photon emission originate from the beam interaction with the near-field transition radiation accompanying the beam-foil collision. This near field radiation is of amplitude comparable with the beam self-field, and can be strong enough that a single emitted photon can carry away a significant fraction of the emitting electron energy. After beam collision with multiple foils, femtosecond collimated electron and photon beams with number density exceeding that of a solid are obtained. The relative simplicity, unique properties, and high efficiency of this gamma-ray source open up new opportunities for both applied and fundamental research including laserless investigations of strong-field QED processes with a single electron beam.
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