Experimental investigation of the Landau-Pomeranchuk-Migdal effect in low-Z targets

Andersen, K.K.; Mikkelsen, R.E.; Ketel, T.J.; Esberg, J.; Sona, P.; Mangiarotti, A.; Andersen, S.L.; Uggerhøj, U.I.; Wistisen, T.N.; Knudsen, H.

doi:10.1103/PhysRevD.88.072007

Article
Report number	arXiv:1309.5765
Title	Experimental investigation of the Landau-Pomeranchuk-Migdal effect in low-Z targets
Author(s)	Andersen, K.K. (Aarhus U.) ; Andersen, S.L. (Aarhus U.) ; Esberg, J. (CERN) ; Knudsen, H. (Aarhus U.) ; Mikkelsen, R.E. (Aarhus U.) ; Uggerhøj, U.I. (Aarhus U.) ; Wistisen, T.N. (Aarhus U.) ; Sona, P. (Florence U.) ; Mangiarotti, A. (Sao Paulo U.) ; Ketel, T.J. (Vrije U., Amsterdam)
Collaboration	CERN NA63 Collaboration
Publication	2013-10-15
Imprint	23 Sep 2013
Number of pages	8
Note	Comments: 8 pages, 13 figures 8 pages, 13 figures
In:	Phys. Rev. D 88 (2013) 072007
DOI	10.1103/PhysRevD.88.072007
Subject category	Detectors and Experimental Techniques
Accelerator/Facility, Experiment	CERN SPS ; NA63 CERN SPS
Test beam	H4
Abstract	In the CERN NA63 collaboration we have addressed the question of the potential inadequacy of the commonly used Migdal formulation of the Landau-Pomeranchuk-Migdal (LPM) effect by measuring the photon emission by 20 and 178 GeV electrons in the range 100 MeV - 4 GeV, in targets of LowDensityPolyEthylene (LDPE), C, Al, Ti, Fe, Cu, Mo and, as a reference target, Ta. For each target and energy, a comparison between simulated values based on the LPM suppression of incoherent bremsstrahlung is shown, taking multi-photon effects into account. For these targets and energies, we find that Migdal's theoretical formulation is adequate to a precision of better than about 5%, irrespective of the target substance.
Copyright/License	arXiv nonexclusive-distrib. 1.0

$A schematical drawing of the setup used in the experiment. Two magnetic dipoles, each 2 meters along the beam, are used at a low field, $B\simeq0.16$ T, to reduce the influence of synchrotron radiation in the MeV region. This, combined with the necessity of deflecting the electrons outside the BGO calorimeter, into the lead glass calorimeter, forces a long lever arm. Right in front of the BGO, a veto scintillator, \texttt{ScV}, was mounted to reject events where the photon has converted or events where an electron may have interacted with the vacuum chamber, generating a shower. The total length of the setup was about 70 m.$ $noimgSpecifications of the targets used. From left to right the columns correspond to the material, the number of foils used, the atomic number of the material, the measured thickness of a single foil, the radiation length \cite{PDG12} and the total target thickness in units of radiation length. Notice that $\radl$ for carbon is scaled, since the measured density is significantly different from the tabulated density of PDG \cite{PDG12}.$