Landau-Pomeranchuk-Migdal effect for multihundred GeV electrons

Hansen, H.; Uggerhøj, U. I.; Biino, C.; Ballestrero, S.; Mangiarotti, A.; Sona, P.; Ketel, T.; Vilakazi, Z.

doi:10.1103/physrevd.69.032001

Cited by 42 publications

(54 citation statements)

References 43 publications

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“…A similar reduction may apply in the case of vacuum-assisted photoionization [7], where the created pair that knocks out the electron may suffer internal screening, leading to a lower photoionization cross section. Finally, the radiation emission from relativistic positronium may be influenced by similar screening effects, depending on emission frequency [8].As for the Landau-Pomeranchuk-Migdal effect -a disturbance of the projectile within the formation length that leads to a reduced cross section; see [9,10], and references therein -the Chudakov effect has color transparency as an analogue in QCD [11].Under the assumption that the created pair moves in a straight line after creation, the only angle that contributes to the separation is the emission angle ' 1= p , resulting in an opening angle of the pair ' 4mc 2 =@!. A pair from a photon of energy @!…”

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confidence: 99%

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Direct Measurement of the Chudakov Effect

Virkus

Thomsen²,

Uggerhøj³

et al. 2008

Phys. Rev. Lett.

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Experimental results for the restricted energy loss of pairs created from 1-178 GeV photons in a thin Au target and subsequently passing a CCD detector are presented. It is shown that pairs-when detected close to the creation vertex-suffer a reduced energy loss due to the internal screening of the charges constituting the pair. Furthermore, the ability to measure directly the energy of the pair by calorimetry enables a comparison with theory as a function of energy. The observed phenomenon is in good qualitative agreement with general expectations from the Chudakov effect but indicates a quantitative disagreement with either of two mutually disagreeing theories. DOI: 10.1103/PhysRevLett.100.164802 PACS numbers: 41.60.ÿm, 07.85.Fv, 29.40.Vj, 95.30.Gv In the preparatory phase of the CERN NA63 experiment, we have investigated the reduced energy deposition from a positron-electron pair in the vicinity of their creation point. This reduction is due to the internal screening of charges, the so-called Chudakov (or King-Perkins-Chudakov) effect [1,2].By taking into account the density effect, a considerable contribution to the ionization energy loss originates from transverse distances b q ' v=! p , where v is the particle speed through the medium with plasma frequency ! p . If a penetrating assembly of separate charges is internally spaced less than this distance, the ionization is influenced by interference terms. This can be the case, e.g., for an energetic hydrogen molecule that is stripped upon entry to the substance, but it can also be an effect present for an electron-positron pair where each participating charge screens the charge of the other as seen from the relevant distance b q in the medium. Because of the Lorentz transformation of angles to the laboratory system, the electron and positron emitted in the pair creation process from a photon of energy @! appear with an approximate angle of 1= mc 2 =E e ' 2mc 2 =@! to the photon momentum @k in the frame of the laboratory. Thus, by defining E e =@! and p @!=mc 2 , we get an opening angle of the pairthe so-called Borsellino angle [3]. The energy loss thus diminishes close to the creation point if the created pair is sufficiently energetic and therefore forward directed. This is the so-called Chudakov effect. In a sense, the Chudakov effect is the pair production analogue of the more familiar density effect in radiation emission.A closely related effect -to both the density effect ([4], Chap. 13.5) and the Chudakov effect-has recently been calculated for Cherenkov radiation emission from e e ÿ pairs in the vicinity of the creation point [5,6]. This internal screening effect may affect decisively the behavior of the Cherenkov emission in neutrino-induced electromagnetic showers. A similar reduction may apply in the case of vacuum-assisted photoionization [7], where the created pair that knocks out the electron may suffer internal screening, leading to a lower photoionization cross section. Finally, the radiation emission from relativistic positronium may be in...

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confidence: 99%

“…As for the Landau-Pomeranchuk-Migdal effect -a disturbance of the projectile within the formation length that leads to a reduced cross section; see [9,10], and references therein -the Chudakov effect has color transparency as an analogue in QCD [11].…”

mentioning

confidence: 99%

Direct Measurement of the Chudakov Effect

Virkus

Thomsen²,

Uggerhøj³

et al. 2008

Phys. Rev. Lett.

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“…A prominent example is the LandauPomeranchuk-Migdal (LPM) effect. It has been predicted already some time ago [8], but only in the past decade it was verified by experiment [9], [10].…”

Section: Introductionmentioning

confidence: 90%

“…We confront the results of a simulation, including the new implementation of the Bremsstrahlung process, with data from recent experiments at the SPS at CERN [10], and at SLAC [9]. The experiments differ in the choice of beam energy and materials, as well as in the range of the observed Bremsstrahlung photon spectrum.…”

Section: Validationmentioning

confidence: 99%

Improved description of Bremsstrahlung for high-energy electrons in Geant4

Schälicke

Ivanchenko

Maire

et al. 2008

2008 IEEE Nuclear Science Symposium Conference Record

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Abstract-Geant4[1] provides a software toolkit for the simulation of particles through matter. It has wide range of applicability, ranging from high-energy particle physics to space science.The physics description of Geant4 is in a constant process of improvement and validation. In this work a new relativistic Bremsstrahlung model is introduced. The key feature is a consistent description of matter effects, esp. the Landau-PomeranchukMigdal (LPM) effect. The LPM effect will be of paramount importance for experiments at modern high-energy colliders, esp. the LHC, as well as in astroparticle physics applications.

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“…The density effect suppression has been refined according to the classical approach [9] and a new ultrarelativistic model with updated LMP effect has been created, which fit the experimental results [10] much better than the previous Geant4 model (Fig.1). The ultra-relativistic model is applicable for electrons and positrons above 1 GeV.…”

Section: Bremsstrahlungmentioning

confidence: 99%