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| Landau–Pomeranchuk–Migdal effect | |
|---|---|
| Name | Landau–Pomeranchuk–Migdal effect |
| Discovered | 1953–1956 |
| Discoverer | Lev Landau, Isaak Pomeranchuk, Arkady Migdal |
| Field | Quantum electrodynamics, High-energy physics, Condensed matter physics |
Landau–Pomeranchuk–Migdal effect is a quantum electrodynamic suppression of bremsstrahlung and pair production in dense media at high energies, arising when formation lengths exceed interatomic spacings; it modifies classical predictions by Lev Landau and Isaak Pomeranchuk and was quantified by Arkady Migdal. The effect plays a pivotal role in cosmic ray shower development, influences measurements in CERN experiments, and connects to coherent radiation phenomena in condensed matter physics and astrophysics. Its study bridges work by figures and institutions such as Enrico Fermi, Paul Dirac, Stanford University, Brookhaven National Laboratory, and Fermilab.
The Landau–Pomeranchuk–Migdal effect describes reduced emission rates for high-energy bremsstrahlung photons and suppressed electron–positron pair production when the quantum formation length, tied to particle energy and photon frequency, becomes comparable to or longer than the mean free path in materials such as lead, tungsten, or silicon. This suppression departs from classical Bethe–Heitler predictions developed by Hans Bethe and Walter Heitler and must be accounted for in analyses by collaborations including ATLAS, CMS, and experiments at DESY. The phenomenon is relevant for detectors designed at Lawrence Berkeley National Laboratory and for modeling cascades in Pierre Auger Observatory and IceCube Neutrino Observatory.
The original theoretical inconsistency prompting this work emerged in postwar discussions between Lev Landau and Isaak Pomeranchuk in the early 1950s, motivated by discrepancies involving scattering calculations related to research at Kurchatov Institute and conceptual foundations advanced by Paul Dirac. Their 1953–1954 papers proposed that multiple scattering in media could reduce radiation emission; subsequent quantitative treatment by Arkady Migdal in 1956 provided a rigorous quantum electrodynamics formalism analogous in ambition to treatments by Richard Feynman and Julian Schwinger. Early experimental hints appeared in accelerator experiments at CERN and Brookhaven National Laboratory during the 1960s, with decisive measurements later performed at SLAC National Accelerator Laboratory under programs involving scientists affiliated with Stanford University and MIT.
Migdal’s formulation uses perturbative quantum field theory methods to compute radiation amplitudes with multiple scattering effects treated via transport equations comparable to approaches of Lev Landau and Lev Pitaevskii in kinetic theory; it employs the concept of formation length originally implicit in work by Enrico Fermi. The formalism contrasts with the Bethe–Heitler cross section derived by Hans Bethe and integrates scattering potentials modeled after atomic screening described in the Thomas–Fermi model and approaches related to Niels Bohr’s concepts. Modern treatments utilize path-integral techniques influenced by Richard Feynman and incorporate medium-modified propagators similar to those used by Andrei Sakharov and Soviet Academy of Sciences theorists. Renormalization insights from Gerard 't Hooft and Murray Gell-Mann underpin higher-order corrections, while connections to coherent radiation link to research by Claude Cohen-Tannoudji and Serge Haroche.
Precision confirmation of the Landau–Pomeranchuk–Migdal effect was achieved in dedicated experiments at SLAC using high-energy electron beams and thin targets such as gold and tungsten; teams including scientists from Stanford Linear Accelerator Center, Princeton University, and University of California, Berkeley employed calorimeters and spectrometers similar to instrumentation developed at CERN and Fermilab. Measurements compared photon spectra against Bethe–Heitler baselines and matched Migdal’s suppression at energies probed by collaborations related to Brookhaven National Laboratory and DESY. More recent studies at CERN and at SPring-8 examined analogous suppression for coherent bremsstrahlung in crystals investigated by researchers affiliated with University of Oxford and Max Planck Society. Observational implications have been assessed in Pierre Auger Observatory cosmic-ray data analysis groups and in instrumentation work at IceCube.
Accounting for the Landau–Pomeranchuk–Migdal effect is essential for accurate modeling in cosmic ray air-shower simulations used by Pierre Auger Observatory and Telescope Array Project, and it influences calorimeter design at facilities such as CERN and Fermilab where collaborations like ATLAS and CMS rely on correct electromagnetic shower modeling. The effect also informs radiation length estimates in medical and industrial accelerators developed by teams at Karolinska Institutet and Siemens Healthineers spin-offs, and it connects to high-energy astrophysical source modeling by researchers at NASA and European Space Agency. Theoretical implications intersect with studies of quark–gluon plasma in Relativistic Heavy Ion Collider experiments and with coherent-medium effects examined at Lawrence Livermore National Laboratory.
Extensions of the original theory address non-Abelian analogues relevant to quantum chromodynamics studies by groups at Brookhaven National Laboratory and CERN (notably impacting heavy-ion collision jet quenching analyses), while related coherent-radiation phenomena include the Ter-Mikaelian effect investigated by Soviet theorists and experiments at IHEP (Protvino). Connections exist to the Landau damping concept from plasma physics developed by Lev Landau and to coherence effects in channeling radiation studied in CERN and DESY experiments. Contemporary research explores analogues in condensed matter physics laboratories at Max Planck Institute and ETH Zurich focusing on Dirac and Weyl materials where medium-induced suppression echoes trends first articulated by Landau, Pomeranchuk, and Migdal.
Category:Quantum electrodynamics Category:High-energy physics Category:Condensed matter physics