Search results for "Coulomb"
showing 10 items of 379 documents
Photon-pion charge asymmetry in e+e− reactions: A laboratory for perturbative QCD phases
1987
Abstract The charge asymmetry in the production of a photon and a meson in e + e - annihilation is studied in perturbative QCD. This quantity measures the interference of amplitudes governed by different momentum scales. It is thus a powerful tool to probe strong interaction phases at high energy and in the context of Sudakov exponentiation and the chromo Coulomb phase. We find a null result at the lowest non-trivial order off α s in the entire kinematic region described by perturbative QCD.
Low-temperature X-ray detectors for precise Lamb shift measurements on hydrogen-like heavy ions
2000
The precise determination of the Lamb shift in heavy hydrogen-like ions provides a sensitive test of quantum electrodynamics in very strong Coulomb"elds, not accessible otherwise. For the investigation of the Lyman-a transitions in 208Pb81‘ or 238U91‘ with su$cient accuracy a high resolving calorimetric detector for hard X-rays (E)100 keV) is presently developed. The detector modules consist of arrays of silicon thermistors and of X-ray absorbers made of high Z material to optimize the absorption e$ciency. The detectors are housed in a specially designed 3He/4He dilution refrigerator with a side arm which "ts to the geometry of the internal target of the storage ring ESR at GSI Darmstadt. T…
Deeply bound pionic atoms from the $(\gamma,p)$ reaction in nuclei
2002
We study the $(\gamma,p)$ reaction on $^{208}Pb$ leading to $^{207}Pb$ with a bound pion attached to it in the lowest 1s or 2p pionic levels. The reaction can be made recoilless to optimize the production cross section but we must choose a bit higher photon energy to overcome the Coulomb barrier in the proton emission. The cross sections obtained are easily measurable and can be larger than 50 per cent of the background from inclusive ($\gamma$,p). This makes it a clear case for the detection of the pionic atom signals, converting this reaction into a practical tool to produce deeply bound pionic atoms.
Spectroscopy of nuclei approaching the proton drip-line using a secondary-fragmentation technique with the RISING detector array
2005
An experiment utilizing a double fragmentation reaction was performed to study isobaric analogue states in A similar to 50 nuclei approaching the proton drip-line. gamma-ray spectroscopy will be used to identify excited states in the neutron-deficient nuclei produced in the second fragmentation reaction. Excited state level schemes will be obtained, through comparison with states in their well-known mirror partners, along with information on Coulomb effects through measurements of the Coulomb energy differences between isobaric analogue excited states. The validity of isospin symmetry for nuclei approaching the proton drip-line can also be investigated and the information gained will aid in…
Nuclear structure of lowestTh229states and time-dependent fundamental constants
2009
The electromagnetic transition between the almost degenerate $5/{2}^{+}$ and $3/{2}^{+}$ states in $^{229}\mathrm{Th}$ is deemed to be very sensitive to potential changes in the fine structure constant $\ensuremath{\alpha}$. State of the art Hartree-Fock and Hartree-Fock-Bogoliubov calculations are performed to compute the difference in Coulomb energies of the two states that determines the sensitivity of the transition frequency \ensuremath{\nu} on variations in $\ensuremath{\alpha}$. The kinetic energies are also calculated that reflect a possible variation in the nucleon or quark masses. As the two states differ mainly in the orbit occupied by the last unpaired neutron the Coulomb energy…
Numerical treatment of the long-range Coulomb potential with Berggren bases
2010
The Schrodinger equation incorporating the long-range Coulomb potential takes the form of a Fredholm equation whose kernel is singular on its diagonal when represented by a basis bearing a continuum of states, such as in a Fourier-Bessel transform. Several methods have been devised to tackle this difficulty, from simply removing the infinite-range of the Coulomb potential with a screening or cut function to using discretizing schemes which take advantage of the integrable character of Coulomb kernel singularities. However, they have never been tested in the context of Berggren bases, which allow many-body nuclear wave functions to be expanded, with halo or resonant properties within a shell…
α-decay spectroscopy of deformed nuclei reexamined
2008
We perform an extensive analysis of $\ensuremath{\alpha}$-decays to ${2}^{+}$ and ${4}^{+}$ states in deformed even-even nuclei by using the stationary coupled channels approach. Collective excitations are described within the rigid rotor model. The $\ensuremath{\alpha}$-nucleus interaction is given by a double folding procedure with M3Y plus Coulomb nucleon-nucleon forces. We use a repulsive potential with one independent parameter in order to localize the $\ensuremath{\alpha}$-particle on the nuclear surface and to fit the experimental $Q$-value. The decaying state is identified with the first resonance inside the resulting pocket-like potential, as suggested by microscopic calculations. …
Coulomb-Fourier representation approach to three-body scattering with charged particles
2004
Abstract We present a novel approach for calculating charged-composite particle scattering. It consists in eliminating by means of a suitably chosen representation that part of the interaction which is of longest range and, hence, gives rise to all the troublesome feaures which plague charged particle scattering theories. In this paper only the simplest case is considered, namely that of two charged and one neutral particles which interact via pairwise strong potentials, and a repulsive Coulomb potential between the charged particles.
Study of meson production in nuclei near threshold
2009
We present a study of the η production at low energies in pd collision with 3He and pd nuclear systems in the final state. The η production mechanism is described by a two-step model and the final state interactions are included fully. The η - d and η - 3He final state interactions are incorporated through the solution of the Lippmann Schwinger equation for a half off-shell η - AT-matrix. For η - d this t -matrix is written in a factorized form, with an off-shell form factor multiplying an on-shell part having the scattering length representation. The p - d final state interaction is included by multiplying the production matrix element by the inverse of the Jost function which includes th…
Electromagnetic properties of low-spin states in102, 104Pd
1986
Electromagnetic transitions from low-lying 0+, 2+, 4+ and 3− states in102, 104Pd have been studied using (p, 2n) and (p, p′) reactions and Coulomb excitation. TheE2 transition probabilities from the 0 3 + state in102Pd (13 W.u.) and from the 02/+ state in104Pd (14 W.u.) are somewhat low for two-phonon states. Generally, theE2 transition rates are reasonably well reproduced by the IBA-2 and by the boson-expansion description. The intruding 0 2 + state (t1/2=14.3 ns) in102Pd is connected to the 22/+ and 2 3 + states via strong E2 transitions: B(E2; 0 2 + → 2 2 + )=96±40 W.u.; B(E2; 2 3 + → 0 2 + =17±11 W.u.