Summary
An experiment is described aiming to measure a possible polarizationP of the protons recoiling in e-p collisions for a four-momentum transferq 2=20 fermi−2. The e-p elastic collisions were detected by observing the scattered electrons and the recoiling protons in coincidence; the polarizationP was deduced by measuring the left-right asymmetry in the scattering of the recoiling protons in the carbon plates of a spark-chamber. The result ofP=0.024±0.050 is consistent with theoretical estimates that the imaginary part of the scattering amplitude arising from the exchange of two photons between the electron and the proton is negligible.
Riassunto
Nel presente lavoro viene descritto un esperimento avente lo scopo di mettere in evidenza una eventuale polarizzazioneP dei protoni di rinculo prodotti nell’urto e-p per un valore del quadrimomento trasferitoq 2=20 fermi−2. Gli urti elastici e-p venivano riconosciuti osservando le coincidenze fra l’elettrone sparpagliato e il protone di rinculo. La polarizzazione dei protoni veniva dedotta dall’asimmetria destra-sinistra dei protoni sparpagliati entro le piastre di grafite di una camera a scintilla. Il risultatoP=0.024±0.050 è compatibile con alcune valutazioni teoriche secondo cui la parte immaginaria dell’ampiezza di « scattering » relativa ai processi in cui due fotoni vengono scambiati fra l’elettrone e il protone è trascurabile.
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supported by the Bundesministerium für wissenschaftliche Forschung.
under a « Government Training Act » assignment and a John Simon Guggenheim Memorial Foundation Followship.
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Di Giorgio, G.V., Ganssauge, E., Gomez, R. et al. Polarization of recoil protons in e-p elastic scattering at 20 fermi−2 . Nuovo Cim 39, 474–485 (1965). https://doi.org/10.1007/BF02735817
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DOI: https://doi.org/10.1007/BF02735817