121398906
Generalized Fermi-Segrè formula
119495662
Direct radiative recombination of electrons with atomic ions: Cross sections and rate coefficients
Simple expressions are obtained which permit systematic estimates of the rate coefficients for direct radiative recombination (DRR) of fast electrons with atomic ions of various ionic species. The analysis utilizes a set of cross sections obtained through numerical calculations combined with the use of an interpolation scheme to smoothly connect reduced cross sections (apart from normalizations) of the bremsstrahlung tip region and the low-lying DRR region. It is shown that these numerical cross sections can be reproduced by the predictions of a modified semiclassical Kramers formula with an appropriate effective charge Z/sub eff/, which is larger than the effective charge which reproduces the energy levels of the states into which capture occurs. In accord with this modified Kramers formula, the numerically obtained total cross sections are shown to scale with Z/sub eff//sup 2//K for each isoelectronic sequence, and with a parameter (n/sub 0/)/sub eff/ which characterizes each isoelectronic sequence. Using these scaling properties, simple analytic expressions are obtained for recombination rate coefficients, for the rate of electron kinetic-energy loss, and for the rate of radiated power loss, assuming a classical Maxwell-Boltzmann thermal distribution of continuum electrons.
123462298
Overlap of shape resonance and Cooper-minimum structure in photoionization
Examples of a Cooper minimum inside the range of a shape-resonance maximum of a photoionization cross section have been found in numerical calculations within a single-electron model in a relativistic Hartree-Fock-Slater potential. In these model calculations for the photoionization of tin and uranium we find relatively broad shape resonances in all the $d$ and $f$ subshells. In addition a Cooper minimum occurs in the outer subshells of these high-angular-momentum states within the region of the shape-resonance maximum. We examine the matrix elements for these subshells and the resulting cross sections and angular distributions.
116481138
Lorentz deformation of the Bethe-Salpeter wave function
Lorentz deformation properties of the covariant Bethe-Salpeter wave function are studied and compared with those of the covariant harmonic oscillator wave function. Space-time and momentum-energy diagrams are constructed and compared with those of the oscillator wave function. It is pointed out that the Lorentz deformation property of the Bethe-Salpeter wave function shown on these diagrams is strikingly similar to that of the oscillator wave function from which a physical interpretation can be derived for the time-separation variable between constituent quarks inside the hadron.
16714272
IS IT POSSIBLE TO CONSTRUCT THE PROTON STRUCTURE FUNCTION BY LORENTZ-BOOSTING THE STATIC QUARK-MODEL WAVE FUNCTION?
The energy-momentum relations for massive and massless particles are E=p2/2m and E=pc respectively. According to Einstein, these two different expressions come from the same formula $E = \sqrt{(cp)^2 + m^2 c^4}$. Quarks and partons are believed to be the same particles, but they have quite different properties. Are they two different manifestations of the same covariant entity as in the case of Einstein's energy-momentum relation? The answer to this question is YES. It is possible to construct harmonic oscillator wave functions which can be Lorentz-boosted. They describe quarks bound together inside hadrons. When they are boosted to an infinite-momentum frame, these wave functions exhibit all the peculiar properties of Feynman's parton picture. This formalism leads to a parton distribution corresponding to the valence quarks, with a good agreement with the experimentally observed distribution.
93080994
Rotations and gauge transformations
The energy-momentum r e l a t i o n for a n o n r e l a t i v i s t i c p a r t i c l e is E : P?/2m, whi le that for a massless p a r t i c l e is E = P. I t was Einstein who un i f i ed these two re la t i ons through his formula E = [p2 + m211/2 In add i t ion to the fourmomentum, a r e l a t i v i s t i c p a r t i c l e has i t s in te rna l space-time degrees o f freedom. When the p a r t i c l e is slow or at res t , the space-time symmetry manifests i t s e l f through by the spin. On the other hand, i f the p a r t i c l e is massless, i t has the h e l i c i t y and gauge degrees of freedom. ~ e question is whether the in te rna l space-time symmetries for massive and massless pa r t i c l es can be un i f i ed . In order to study th i s problem, we use Wigner's l i t t l e groups. I The l i t t l e group is the maximal subgroup o f the Lorentz group which leaves the four-momentum of the p a r t i c l e i nva r i an t . In order to construct a t ransformation which leaves the four-momentum i n v a r i a n t , l e t us consider a p a r t i c l e moving along the z d i r e c t i o n with v e l c i t y parameter m. We can ro ta te th is p a r t i c l e around the y axis by e. We can then make a boost to come back to the o r i g i n a l momentum, me four-momentum is unchanged under th i s boost preceded by the above-mentioned r o t a t i o n . 2 The matr ix which performs th i s t ransformat ion is
124194266
Operation of single GEM, GEM + MWPC, and GEM + MSGC detectors
5119942
Measuring superparticle masses at hadron collider using the transverse mass kink
We present a detailed study of the collider observable mT2 applied for pair-produced superparticles decaying to visible particles and a pair of invisible lightest supersymmetric particles (LSPs). Analytic expressions of the maximum of mT2 over all events (mT2max) are derived. It is noticed that if the decay product of each superparticle involves more than one visible particle, mT2max being a function of the trial LSP mass mχ has a kink structure at mχ = true LSP mass, which can be used to determine the mother superparticle mass and the LSP mass simultaneously. To see how well mT2max can be constructed from collider data, a Monte-Carlo analysis of the gluino mT2 is performed for some superparticle spectra.