210 research outputs found
Ultraperipheral Collisions at RHIC and LHC
A brief introduction to the physics of ultraperipheral collisions at collider
energies is given. Photon-hadron (proton/ nucleus) and photon-photon
interactions can be studied in a hitherto unexplored energy regime.Comment: 3 pages, 2 figures, Proceedings of PHOTON 2007, Paris 9-13 July 2007,
to be published in Nucl. Phys. B (Proceedings Supplements
Single-Photon Switch based on Rydberg Blockade
All-optical switching is a technique in which a gate light pulse changes the
transmission of a target light pulse without the detour via electronic signal
processing. We take this to the quantum regime, where the incoming gate light
pulse contains only one photon on average. The gate pulse is stored as a
Rydberg excitation in an ultracold atomic gas using electromagnetically induced
transparency. Rydberg blockade suppresses the transmission of the subsequent
target pulse. Finally, the stored gate photon can be retrieved. A retrieved
photon heralds successful storage. The corresponding postselected subensemble
shows an extinction of 0.05. The single-photon switch offers many interesting
perspectives ranging from quantum communication to quantum information
processing
Transverse momentum distribution of vector mesons produced in ultraperipheral relativistic heavy ion collisions
We study the transverse momentum distribution of vector mesons produced in
ultraperipheral relativistic heavy ion collisions (UPCs). In UPCs there is no
strong interaction between the nuclei and the vector mesons are produced in
photon-nucleus collisions where the (quasireal) photon is emitted from the
other nucleus. Exchanging the role of both ions leads to interference effects.
A detailed study of the transverse momentum distribution which is determined by
the transverse momentum of the emitted photon, the production process on the
target and the interference effect is done. We study the total unrestricted
cross section and those, where an additional electromagnetic excitation of one
or both of the ions takes place in addition to the vector meson production, in
the latter case small impact parameters are emphasized.Comment: 12 pages, REVTeX manuscrip
Production of Low Mass Electron Pairs Due to the Photon-Photon Mechanism in Central Collisions
We calculate the probability for dilepton production in central relativistic
heavy ion collisions due to the gamma-gamma mechanism. This is a potential
background to more interesting mechanisms. We find that this mechanism is
negligible in the CERES experiments. Generally, the contribution due to this
mechanism is small in the central region, while it can be large for small
invariant masses and forward or backward rapidities. A simple formula based on
the equivalent photon approximation and applications to a possible scenario at
RHIC are also given.Comment: 10 pages REVTeX, 5 Figures, for related work see
http://quasar.physik.unibas.ch/~hencken
Single-Photon Transistor Using a F\"orster Resonance
An all-optical transistor is a device in which a gate light pulse switches
the transmission of a target light pulse with a gain above unity. The gain
quantifies the change of the transmitted target photon number per incoming gate
photon. We study the quantum limit of one incoming gate photon and observe a
gain of 20. The gate pulse is stored as a Rydberg excitation in an ultracold
gas. The transmission of the subsequent target pulse is suppressed by Rydberg
blockade which is enhanced by a F\"orster resonance. The detected target
photons reveal in a single shot with a fidelity above 0.86 whether a Rydberg
excitation was created during the gate pulse. The gain offers the possibility
to distribute the transistor output to the inputs of many transistors, thus
making complex computational tasks possible
Production of QED pairs at small impact parameter in relativistic heavy ion collisions
The STAR collaboration at RHIC is measuring the production of
electron-positron pairs at small impact parameters, larger than but already
close to the range, where the ions interact strongly with each other. We
calculate the total cross section, as well as, differential distributions of
the pair production process with the electromagnetic excitation of both ions in
a semiclassical approach and within a lowest order QED calculation. We compare
the distribution of electron and positron with the one coming from the cross
section calculation without restriction on impact parameter. Finally we give an
outlook of possible results at the LHC.Comment: 15 pages, 8 figure
Electromagnetic Dissociation as a Tool for Nuclear Structure and Astrophysics
Coulomb dissociation is an especially simple and important reaction
mechanism. Since the perturbation due to the electric field of the nucleus is
exactly known, firm conclusions can be drawn from such measurements.
Electromagnetic matrix elements and astrophysical S-factors for radiative
capture processes can be extracted from experiments. We describe the basic
theory, new results concerning higher order effects in the dissociation of
neutron halo nuclei, and briefly review the experimental results obtained up to
now. Some new applications of Coulomb dissociation for nuclear astrophysics and
nuclear structure physics are discussed.Comment: 10 pages, 1 figure, to appear in Proceedings of the International
School on Nuclear Physics; 22nd Course: ``Radioactive Beams for Nuclear and
Astro Physics'', Erice/Sicily/Italy, September 16 - 24, 200
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