2,337 research outputs found
Ultimate parameters of the photon collider at the ILC
At linear colliders, the e+e- luminosity is limited by beam-collision
effects, which determine the required emittances of beams in damping rings
(DRs). While in gamma-gamma collisions at the photon collider, these effects
are absent, and so smaller emittances are desirable. In present damping rings
designs, nominal DR parameters correspond to those required for e+e-
collisions. In this note, I would like to stress once again that as soon as we
plan the photon-collider mode of ILC operation, the damping-ring emittances are
dictated by the photon-collider requirements--namely, they should be as small
as possible. This can be achieved by adding more wigglers to the DRs; the
incremental cost is easily justified by a considerable potential improvement of
the gamma-gamma luminosity. No expert analysis exists as of yet, but it seems
realistic to obtain a factor five increase of the gamma-gamma luminosity
compared to the ``nominal'' DR design.Comment: Talk at LCWS06, Bangalore, India, March 2006, to be published in
Indian Journal of Physics, 5 pp, Latex, 1 .eps figur
Relativistic mask method for electron momentum distributions after ionization of hydrogen-like ions in strong laser fields
Wavefunction-splitting or mask method, widely used in the non-relativistic
calculations of the photoelectron angular distributions, is extended to the
relativistic domain within the dipole approximation. Since the closed-form
expressions for the relativistic Volkov states are not available within the
dipole approximation, we build such states numerically solving a single
second-order differential equation. We calculate the photoelectron energy
spectra and angular distributions for highly charged ions under different
ionization regimes with both the direct and the relativistic mask methods. We
show that the relativistic mask method works very well and reproduces the
electron energy and angular distributions calculated by the direct method in
the energy range where both methods can be used. On the other hand, the
relativistic mask method can be applied for longer laser pulses and/or higher
photoelectron energies where the direct method may have difficulties
Restriction on the energy and luminosity of e+e- storage rings due to beamstrahlung
The role of beamstrahlung in high-energy e+e- storage-ring colliders (SRCs)
is examined. Particle loss due to the emission of single energetic
beamstrahlung photons is shown to impose a fundamental limit on SRC
luminosities at energies 2E_0 >~ 140 GeV for head-on collisions and 2E_0 >~ 40
GeV for crab-waist collisions. With beamstrahlung taken into account, we
explore the viability of SRCs in the E_0=240-500 GeV range, which is of
interest in the precision study of the Higgs boson. At 2E_0=240 GeV, SRCs are
found to be competitive with linear colliders; however, at 2E_0=400-500 GeV,
the attainable SRC luminosity would be a factor 15-25 smaller than desired.Comment: Latex, 5 pages. v2 differs only by minor changes is abstract and
introduction, one reference is added. v3 corresponds to the paper published
in PR
Full one-loop QCD and electroweak corrections to sfermion pair production in collisions
We have calculated the full one-loop electroweak (EW) and QCD corrections to
the third generation scalar-fermion pair production processes at an
electron-positron linear collider(LC) in the minimal supersymmetric standard
model (MSSM). We analyze the dependence of the radiative corrections on the
parameters such as the colliding energy and the SUSY
fundamental parameters , , , and so forth. The
numerical results show that the EW corrections to the squark-, stau-pair
production processes and QCD corrections to the squark-pair production
processes give substantial contributions in some parameter space. The EW
relative corrections to squark-pair production processes can be comparable with
QCD corrections at high energies. Therefore, these EW and QCD corrections
cannot be neglected in precise measurement of sfermion pair productions via
collision at future linear colliders.Comment: to be appeared in Phys. Rev.
High-order perturbation expansion of non-Hermitian Floquet theory for multiphoton and above-threshold ionization processes
This is the published version, also available here: http://dx.doi.org/10.1103/PhysRevA.61.013408.A high-order perturbation theory is presented for efficient and accurate computation of multiphoton and above-threshold ionization cross sections of atoms and molecules in weak to medium strength laser fields. The procedure is based on a Raleigh-Schrödinger perturbative expansion of the time-independent non-Hermitian Floquet Hamiltonian. The reduced Green function and generalized pseudospectral discretization techniques are extended to facilitate the calculation of complex quasienergy resonance states without the need of diagonalizing the full Floquet Hamiltonian. Explicit expressions are presented for the determination of intensity-dependent total and partial rates and electron angular distributions. The theory is applied to a case study of multiphoton detachment of H- for a range of laser frequencies (corresponding to the absorption of a minimum of two photons) and laser intensities from 107 to 1012W/cm2. It is found that a 16th-order perturbative Floquet procedure provides an excellent description of the two-photon-dominant detachment processes for laser intensity up to 2×1011W/cm2. The predicted electron angular distributions are in good agreement with recent experimental data
Low-energy structure of above-threshold-ionization electron spectra: Role of the Coulomb threshold effect
This is the publishers version, also available here: http://dx.doi.org/10.1103/PhysRevA.83.063406.Recent experimental observations of above-threshold ionization of rare gas atoms and diatomic molecules by midinfrared laser fields [C. I. Blaga et al., Nat. Phys. 5, 335 (2009); W. Quan et al., Phys. Rev. Lett. 103, 093001 (2009)] revealed a prominent maximum in the electron energy spectrum very close to the ionization threshold which is not reproduced by widely used Keldysh-Faisal-Reiss theories. We have performed fully ab initio theoretical analysis and precision calculations to explore the quantum origin of the low-energy structure (LES) observed in the experiments. Our study shows that an important role in shaping of LES is played by the effect of Coulomb attraction in the final electron state and the Coulomb threshold effect
Multiphoton above-threshold detachment of Li-: Exterior-complex-scaling– generalized-pseudospectral method for calculations of complex-quasienergy resonances in Floquet formulation of time-dependent density-functional theory
This is the publisher's version, also available electronically from http://journals.aps.org/pra/abstract/10.1103/PhysRevA.66.043417.We extend the exterior-complex-scaling–generalized-pseudospectral (ECSGPS) method [D. A. Telnov and S. I. Chu, Phys. Rev. A 59, 2864 (1999)] to the nonperturbative calculations of complex-quasienergy resonances of many-electron quantum systems within the Floquet formulation of time-dependent density-functional theory (TDDFT) [D. A. Telnov and S. I. Chu, Chem. Phys. Lett. 264, 466 (1997)]. The ECSGPS technique appears very useful in TDDFT-Floquet calculations where the exchange-correlation potentials may exhibit quite complicated behavior as functions of the electron coordinates and cannot be easily treated by means of the uniform-complex-scaling techniques. We have applied this procedure to the study of one-photon detachment and two-photon dominant above-threshold detachment of Li- negative ions. In the one-photon case, the photodetachment cross section has been calculated as a function of the photon energy with results in good agreement with the experimental data. In the two-photon case, both the partial detachment rates and electron angular distributions for the dominant and above-threshold channels are presented for a range of laser field frequencies and intensities. Dramatic transformations of the angular distributions in the vicinity of the two-photon threshold are observed and analyzed
Exact relations of the quasienergy functional and the exchange-correlation potential from the Floquet formulation of time-dependent density functional theory
In the framework of the Floquet formulation of time-dependent density functional theory we present several
exact relations involving different parts of the quasienergy functional. These relations hold when the exact
densities and exchange-correlation energy functional are employed. They can be used as useful constraints and
tests when searching for the approximate forms of the time-dependent exchange-correlation functionals. The
general results are illustrated on an exactly soluble model, Hooke’s atom in a linearly polarized monochromatic
laser field
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