| Scientific Committee Paper | |
| Report number | CERN-SPSC-2009-038 ; SPSC-P-327-ADD-1 |
| Title | Electromagnetic processes in strong crystalline fields |
| Project Manager/Technical Coordinator | Uggerhoj, Ulrik |
| Author(s) |
Uggerhoj, U I ; Andersen, K K (Aarhus U.) ; Esberg, J (Aarhus U.) ; Knudsen, H (Aarhus U.) ; Lund, M (Aarhus U.) ; Møller, S P (Aarhus U.) ; Sørensen, A H (Aarhus U.) ; Thomsen, A H (Aarhus U.) ; Uggerhøj, U I (Aarhus U.) ; Geissel, H (Darmstadt, GSI) ; Scheidenberger, C (Darmstadt, GSI) ; Weick, H (Darmstadt, GSI) ; Winfield, J (Darmstadt, GSI) ; Sona, P (Florence U.) ; Connell S (Johannesburg U.) ; Ballestrero, S (Johannesburg U.) ; Ketel, T (Free U.) ; Dizdar, A (Istanbul U.) ; Mangiarotti, A (Coimbra U.) |
| Corporate author(s) | CERN. Geneva. SPS and PS Experiments Committee ; SPSC |
| Series | (Addendum (Proposal)) |
| Submitted by | [email protected] on 07 Dec 2009 |
| Subject category | Detectors and Experimental Techniques |
| Accelerator/Facility, Experiment | CERN SPS ; NA63 |
| Abstract | As an addendum to the NA63 proposal cite{Ande05}, we propose to measure 1) the Landau-Pomeranchuk-Migdal (LPM) effect in low-$Z$ targets, 2) Magnetic suppression of incoherent bremsstrahlung resulting from exposure to an external field during the emission event, and 3) the bremsstrahlung emission from relativistic ($gamma=170$), fully stripped Pb nuclei penetrating various amorphous targets. Concerning the LPM effect, both the 'traditional' Migdal approach and the modern treatment by Baier and Katkov display inaccuracies, i.e. a possible lack of applicability in low-$Z$ targets. Moreover, the LPM effect has been shown to have a significant impact on giant air showers for energies in the EeV range - evidently processes in a low-$Z$ material. A measurement of magnetic suppression is demanding in terms of necessary accuracy (an expected $lesssim$15% effect), but would prove the existence of a basic interplay between coherent and incoherent processes, also believed to be significant in beamstrahlung emission. For bremsstrahlung from Pb$^{82+}$: In contrast to earlier expectations, recent investigations have shown that the bremsstrahlung emission from heavy, relativistic particles does not appear with constant power for all photon energies up to the end-point given by the energy of the incident ion, but instead the spectrum has a peaked shape, due to the finite size of the nucleus. Beyond an energy of about $2gammahbaromega_1$, wher e $hbaromega_1$ corresponds to the energy transfer above which the $Z$ protons in the nucleus can be considered quasi-free, the power-spectrum falls off quite steeply, eventually leaving pair production as the dominant energy loss mechanism for sufficiently high values of the Lorentz-factor. |
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Záznam vytvorený 2009-12-07, zmenený 2018-03-16
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