Cargando…

Status and plans for 2015, CERN NA63

We summarize the status and plans for the future for the CERN NA63 collaboration. A systematic study of the structured target 'resonance' appearing from radiation emission by electrons passing two amorphous foils positioned with separations in the range $10-20000~\mu$m was performed in our...

Descripción completa

Detalles Bibliográficos
Autores principales: Mikkelsen, RE, Uggerhoj, UI, Wistisen, TN
Publicado: 2014
Materias:
Acceso en línea:http://cds.cern.ch/record/1707380
Descripción
Sumario:We summarize the status and plans for the future for the CERN NA63 collaboration. A systematic study of the structured target 'resonance' appearing from radiation emission by electrons passing two amorphous foils positioned with separations in the range $10-20000~\mu$m was performed in our latest run. The recently published results \cite{Ande14} confirm a previously obtained result \cite{Ande12a} that by this method, the formation length - of macroscopic dimensions up to 0.5 mm - for the generation of MeV-GeV radiation from multi-hundred GeV electrons can be \emph{directly} measured. In fact the results obtained now allow a distinction between competing theories \cite{Blan97a,Baie99b}, showing that it is unlikely that the correction-term introduced by Blankenbecler holds true \cite{Blan97b}. Our investigations of the LPM effect in low-$Z$ targets have been completed and published \cite{Ande13}. The overall conclusion for these studies is that the formalism of Migdal is sufficient to describe the experimental data - for any $Z$ - within the statistical uncertainty. Preparing for beam time in 2015, we have refined and updated our theoretical analyses of bremsstrahlung and delta-electron emission from heavy, and medium-heavy, ultrarelativistic nuclei. We can thus conclude that - although not quite as interesting as for Pb projectiles - projectiles of Ar and/or Xe are suitable for the investigation, and for establishing the method to eventually measure the charge distribution of short-lived ($ct\gtrsim3$m) fragments \cite{Mikk14}. Furthermore, we have prepared a new simulation code to determine the theoretically expected number of positrons produced by electrons traversing an aligned diamond target. This code, in a previous version, compares very well to radiation emission observed from sub-GeV electrons passing a crystalline undulator \cite{Wist14} - previously also the subject of investigations by CERN NA63.