Ionization Energy Loss of Relativistic Electrons in Thin Silicon Detectors

Ogle, W.; Goldstone, P. D.; Gruhn, C.R.; Maggiore, C. J.

doi:10.1103/physrevlett.40.1242

Cited by 9 publications

(12 citation statements)

References 4 publications

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“…4 are shown the experimental results (based on 2 10 7 electrons in total) for the ratio of the MPEL for Au1 to that of Au2, compared to three theoretical expectations. We note that, since this is a relative measurement, uncertainties connected to departures from an exact Landau shape [19] or a possible reduced energy deposition at high energies [20,21] are likely to be insignificant. Such departures could-besides the thickness dependence -for instance, result from a smaller suppression at small impact parameters than at large ones, i.e., a smaller suppression at energy losses large compared to the MPEL.…”

Section: Prl 100 164802 (2008) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 99%

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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Section: Prl 100 164802 (2008) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 99%

Direct Measurement of the Chudakov Effect

Virkus

Thomsen²,

Uggerhøj³

et al. 2008

Phys. Rev. Lett.

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show abstract

“…In opposition to the possible extinction of the density effect, Ogle and collaborators [1] found experimentally that the restricted energy loss diminishes for sufficiently high Lorentz factors. They suggested an explanation based on the existence of a 'coherence length' that vanishes for Lorentz factors less than a critical value c ( c c ¼ ax p =2c and for c ( 2mc 2 = hx p the latter of which is ' 3:3 Â 10 4 for Si.…”

Section: Coherence Length Effectmentioning

confidence: 95%

“…Although the mentioned background effects rise strongly in significance with the energy of the primary particle, and with the thickness of the detector used, both effects may have contributed in the measurements performed by Ogle et al [1], who used a tagged electron beam -inevitably subject to synchrotron radiation -and varying thickness of the upstream material for the different Lorentz factors, giving a possible difference in the contribution from transition radiation. This may partly explain their observations, at least for the highest Lorentz factors, 4:8 Â 10 4 and 1:0 Â 10 5 .…”

Section: Background From Synchrotron and Transition Radiationmentioning

confidence: 96%

“…(2) in [1] for targets thicker than ' 270 lm leads to values significantly different from 1 below 2mc 2 = hx p ' 3:3 Â 10 4 where the theory is stated as giving no correction. On the other hand, the physical mechanism suggested -loss of coherence leading to reduced energy loss -might have been correct and its investigation was the main aim for the present study.…”

Section: Coherence Length Effectmentioning

confidence: 97%

“…Previous studies [1,2] have shown effects with trends in opposite directions, giving either an increasing or a decreasing restricted energy loss for sufficiently high Lorentz factors. These studies have been both experimental and theoretical and remarkably -in spite of disagreements on the sign of the slope above the cut-off -they both predict negligible effects for Lorentz factors below c c ¼ ax p =2c, where a is the thickness of the target, x 0 the plasma frequency and c the speed of light.…”

Section: Introductionmentioning

confidence: 98%

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