Simple analytical representation for Delbrück scattering amplitudes at high energies

We use a new representation for the semiclassical Green’s function of the Dirac equation in the Coulomb field to find an exact (in the parameter Zα) expression for the amplitudes of small-angle Delbru ck scattering of high-energy photons. The values of these amplitudes agree with those obtained in earlier calculations, but the structure of the expressions is much simpler than that of previously known representations, which makes numerical calculations much easier. Zh. éksp. Teor. Fiz. 116, 78–84 (July 1999)     

Electroweak radiative corrections to polarized Møller scattering at high energies

The cross section for with arbitrary electron polarizations is calculated within the Electroweak Standard Model for energies large compared to the electron mass, including the complete virtual and soft-photonic radiative corrections. The relevant analytical results are listed, and a numerical evaluation is presented for the unpolarized and polarized cross sections as well as for polarization asymmetries. The relative weak corrections are typically of the order of 10%. At low energies, the bulk of the corrections is due to the running of the electromagnetic coupling constant. For left-handed electrons, at high energies the vertex and box corrections involving virtual W bosons become very important. The polarization asymmetry is considerably reduced by the weak radiative corrections. Received: 22 July 1998 / Published online: 8 September 1998     

Delbrück-Streuung von 17 MeV-Photonen

Differential cross sections have been measured for the small angle scattering ofγ-rays by iron, silver, tantalum, lead and uranium with 17 MeV photons from Li⁷ (p, γ) Be⁸ at mean four momentum transfersq of 0·5mc and 1·3mc and with 7 MeV photons from F¹⁹(p, αγ)O¹⁶ at mean four momentum transfer of 0·5mc. Under these experimental conditions only Compton, Rayleigh and possibly Delbrück scattering are of importance. Extrapolation of known theoretical results to higher energies shows, that Rayleigh and Compton scattering from bound electrons should depend only onq for small angles, smallq and fixedZ. Using this it follows, that at 17 MeV andq≈0·5mc an additional scattering process must be present, which increases with growingZ and which is negligible in the measurements at 17 MeV withq≈1·3mc and at 7 MeV withq≈0·5mc. These results are in qualitative agreement with the approximate theory for Delbrück scattering ofBethe andRohrlich, however experimental cross sections at 17 MeV andq≈0·5mc are about a factor of 1·6 lower than those predicted by this theory. This discrepancy is not unexpected, since exact calculations of Delbrück scattering amplitude fromKessler andZernik at 2·62 MeV and 6·14 MeV show even greater deviations in the same sense.     

Weak and electromagnetic corrections to sin2 θ w in deep inelastic neutrino-nucleon scattering

The weak and electromagnetic corrections to deep inelastic neutrino scattering experiments are calculated. The results are used to determineθ _w from the ratios $$R_v = \frac{{\sigma _{nc} }}{{\sigma _{cc} }} and D_ - = \frac{{\sigma _{nc} - \bar \sigma _{nc} }}{{\sigma _{cc} - \bar \sigma _{nc} }}$$ It is found that the effect of the weak corrections is less than 1% and that electromagnetic corrections decrease the angle by about 3%.     

Coulomb wave function corrections for n-particle Bose–Einstein correlations

The effect of multi-particle Coulomb final state interactions on higher-order intensity correlations is determined in general, based on a scattering wave function which is a solution of the n-body Coulomb Schr?dinger equation in (a large part of) the asymptotic region of n-body configuration space. In particular, we study Coulomb effects on the n-particle Bose–Einstein correlation functions of similarly charged particles and remove a systematic error as big as 100% from higher-order multi-particle Bose–Einstein correlation functions. Received: 24 November 1999 / Published online: 17 March 2000     

Long-range Coulomb forces in DIS: missed radiative corrections?

The Born approximation, one photon exchange, used for DIS (deep inelastic scattering) is subject to virtual radiative corrections which are related to the long-range Coulomb forces. They may be sizeable for heavy nuclei since Zα is not a small parameter. So far, these corrections are known only for two processes, elastic scattering and bremsstrahlung on the Coulomb field of a point-like target. While the former amplitude acquires only a phase, in the latter case also the cross-section is modified. Although the problem of Coulomb corrections for DIS on nuclei is extremely difficult, it should be challenged rather than “swept under the carpet”. The importance of these radiative corrections is questioned in the present paper. We show that, in the simplest case of a constant hadronic current, the Coulomb corrections provide a phase to the Born amplitude, therefore the cross-section remains the same. Inclusion of more realistic hadronic dynamics changes this conclusion. The example of coherent production of vector mesons off nuclei reveals large effects. So far a little progress has been made deriving lepton wave functions in the Coulomb field of an extended target. Employing available results based on the first-order approximation in Zα, we conclude that the Coulomb corrections are still important for heavy nuclei. We also consider an alternative approach for extended nuclear targets, the eikonal approximation, which we demonstrate to reproduce the known exact results for Coulomb corrections. Calculating electroproduction of vector mesons, we again arrive at a large deviation from the Born approximation. We conclude that one should accept with caution the experimental results for nuclear effects in DIS based on analyses done in the Born approximation. Received: 16 May 2001 / Accepted: 4 July 2001     

Isospin-breaking corrections in the pion–deuteron scattering length

It is shown that isospin-breaking corrections to the pion–deuteron scattering length can be very large, because of the vanishing of the isospin-symmetric contribution to this scattering length at leading order in chiral perturbation theory. We further demonstrate that these corrections can explain the bulk of the discrepancy between the recent experimental data on pionic hydrogen and pionic deuterium. We also give the first determination of the electromagnetic low-energy constant f₁$f_1$.     

Two-loop electroweak vertex corrections for polarized Møller scattering

The contributions to the electron-electron-photon vertex of two-loop electroweak corrections are calculated. The relative correction to the parity-violating asymmetry of Møller scattering for the case of 11 GeV electron scattered off the electron at rest is found to be about–0.0034 and should be taken into account at future experiment MOLLER at JLab.     

Nonperturbative corrections to the cross section ratio R=σL/σT for deep-inelastic scattering

The contribution of nonperturbative corrections, proportional to the quark and gluon vacuum condensates, to the ratio R=_L/_T, where _L and _T are the cross sections for longitudinal and transversal photon scattering by nucleons, is calculated. It is shown that these condensate corrections amount to 30% in the range 0.1相似文献   

德耳布吕克（Delbrück，Max，1906-1981）德国-美国微生物学家（Microbiologist，Germany-America）

德耳布吕克1930年在格廷根大学获博士学位，在哥本哈根玻尔手下做博士后研究工作，后到柏林和哈恩及迈特纳一起工作。希特勒上台后，他离开德国，于1937年到达美国。当他还在柏林时，兴趣就开始从核物理转到了遗传学。在加利福尼亚理工学院，他又开始为噬菌体所吸引。噬菌体是以细菌细胞为食的较大的病毒。他发现，一个细菌细胞一旦被一个噬菌体所感染，这个细胞经过半个小时就会分裂，并产生100个噬菌体，每个噬菌体又随时会感染另一个细菌细胞。     

Entropic Corrections to Coulomb’s Law

Two well-known quantum corrections to the area law have been introduced in the literatures, namely, logarithmic and power-law corrections. Logarithmic corrections, arises from loop quantum gravity due to thermal equilibrium fluctuations and quantum fluctuations, while, power-law correction appears in dealing with the entanglement of quantum fields in and out the horizon. Inspired by Verlinde’s argument on the entropic force, and assuming the quantum corrected relation for the entropy, we propose the entropic origin for the Coulomb’s law in this note. Also we investigate the Uehling potential as a radiative correction to Coulomb potential in 1-loop order and show that for some value of distance the entropic corrections of the Coulomb’s law is compatible with the vacuum-polarization correction in QED. So, we derive modified Coulomb’s law as well as the entropy corrected Poisson’s equation which governing the evolution of the scalar potential ϕ. Our study further supports the unification of gravity and electromagnetic interactions based on the holographic principle.     

Superstring loop corrections to σ-model ß-functions

We present an algorithm for string one-loop corrections to σ-model ß-functions in closed superstring theories, by identifying the massless poles in string one-loop amplitudes with the ultraviolet divergences in the corresponding two-dimensional σ-model. The string one-loop corrected ß-functions for the type-II superstring are given.     

Complete calculation of electroweak corrections for polarized Møller scattering at high energies

A complete calculation of electroweak radiative corrections to observables of polarized Møller scattering at high energies was performed. This calculation took explicitly into account contributions caused by hard bremsstrahlung. A FORTRAN code that permitted including radiative corrections to high-energy Møller scattering under arbitrary electron-detection conditions was written. It was shown that the electroweak corrections caused by hard bremsstrahlung were rather strongly dependent on the choice of experimental cuts and changed substantially the polarization asymmetry in the region of high energies and over a broad interval of scattering angles.     

Herstellung des Arzneimittels Hexamethylmelamin mit deuteriertem Seitenstück

Treatment of N,N,N′,N′,N″-Pentamethyl-1,3,5-triazin-2,4,6-triamin with butyllithium and trideuteroiodomethane give N,N,N′,N′,N″-Pentamethyl-N″-(trideuteromethyl)-1,3,5-triazin-2,4,6-triamin, a deuterated analogue of the anticancer drug hexamethylmelamine, in high yield.