Physics Opportunities in Ultraperipheral Heavy Ion Collisions at LHC

Due to coherence, there are strong electromagnetic fields of short duration in very peripheral heavy ion collisions. They give rise to photon-photon and photon-nucleus collisions with high flux. Photon-photon and photon-hadron physics at various invariant mass scales are discussed.Comment: 9 pages, 4 figures Proceedings of the Workshop on Electromagnetic Probes of Fundamental Physics, Oct. 16-21,2001, Erice, Ital

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

Direct Reactions with Exotic Nuclei

We discuss recent work on Coulomb dissociation and an effective-range theory of low-lying electromagnetic strength of halo nuclei. We propose to study Coulomb dissociation of a halo nucleus bound by a zero-range potential as a homework problem. We study the transition from stripping to bound and unbound states and point out in this context that the Trojan-Horse method is a suitable tool to investigate subthreshold resonances.Comment: 9 pages, 1 figure, proceedings of Workshop on "Reaction Mechanisms for Rare Isotope Beams" Michigan State University March 9-12,200

Investigation of subthreshold resonances with the Trojan horse method

It is pointed out that the Trojan horse method is a suitable tool to investigate subthreshold resonances.Comment: references added, typo corrected;6 pages, 1 figure, to be published in the AIP Proceedings of Fusion06, International Conference on Reaction Mechanisms and Nuclear Structure at the Coulomb Barrier, March 19-23, 2006, San Servolo, Ital

Stock-bond co-movements and cross-country linkages

This paper shows empirically that the level of stock-bond correlation depends more on crosscountry influences than on stock and bond market interaction. The study examines the relation of cross-country and cross-asset stock and bond market linkages for eight developed countries and finds that (i) stock market returns primarily depend on the US stock market and (ii) bond market returns primarily depend on the US bond market. Recursive Granger causality tests further show that the dominance of the US stock and bond market has increased in recent years and that there is both Granger causality from stocks to bonds and from bonds to stocks in several periods. We argue that the relatively low level of stock-bond correlations is due to an increased cross-country interdependence of financial markets leading to more frequent portfolio reallocations between stocks and bonds in order to compensate for lower cross-country diversification benefits.financial market integration, stock market co-movements, bond market co-movements, stock-bond linkages, flight-to-quality, contagion

Coherent photon-photon interactions in very peripheral relativistic heavy ion collisions

Heavy ions at high velocities provide very strong electromagnetic fields for a very short time. The main characteristics of ultraperipheral relativistic heavy ion collisions are reviewed, characteristic parameters are identified. The main interest in ultraperipheral heavy ion collisions at relativistic ion colliders like the LHC is the interactions of very high energy (equivalent) photons with the countermoving (equivalent) photons and hadrons (protons/ions). The physics of these interactions is quite different from and complementary to the physics of the strong fields achieved with current and future lasers.Comment: 5 pages, 5 figures, invited talk presented at the ELI Workshop and School on Fundamental Physics with Ultra-high Fields (September 29- October 2, 2008, Frauenwoerth, German

Direct Reactions with Exotic Nuclei, Nuclear Structure and Astrophysics

Intermediate energy Coulomb excitation and dissociation is a useful tool for nuclear structure and astrophysics studies. Low-lying strength in nuclei far from stability was discovered by this method. The effective range theory for low-lying strength in one-neutron halo nuclei is summarized and extended to two-neutron halo nuclei. This is of special interest in view of recent rather accurate experimental results on the low-lying electric dipole strength in $^{11}$Li. Another indirect approach to nuclear astrophysics is the Trojan horse method. It is pointed out that it is a suitable tool to investigate subthreshold resonances.Comment: 8 pages, 2 figures, Proceedings of the Erice School on 'Radioactive Beams, Nuclear Dynamics and Astrophysics' to be published in 'Prog. Part. Nucl. Phys.

Photon-Photon and Photon-Hadron Interactions at Relativistic Heavy Ion Colliders

In central collisions at relativistic heavy ion colliders like the Relativistic Heavy Ion Collider RHIC/Brookhaven and the Large Hadron Collider LHC (in its heavy ion mode) at CERN/Geneva, one aims at detecting a new form of hadronic matter --- the Quark Gluon Plasma. We discuss here a complementary aspect of these collisions, the very peripheral ones. Due to coherence, there are strong electromagnetic fields of short duration in such collisions. They give rise to photon-photon and photon-nucleus collisions with high flux up to an invariant mass region hitherto unexplored experimentally. After a general survey photon-photon luminosities in relativistic heavy ion collisions are discussed. Then photon-photon physics at various gamma-gamma-invariant mass scales is discussed. The region of several GeV, relevant for RHIC is dominated by QCD phenomena (meson and vector meson pair production). Invariant masses of up to about 100 GeV can be reached at LHC, and the potential for new physics is discussed. Lepton-pair production, especially electron-positron pair production is copious. Due to the strong fields there will be new phenomena, especially multiple e+e- pair production.Comment: 10 pages, Proceedings of the Erice Summer School on Heavy Ion Physics 199

Comment on "A Quantum-Mechanical Equivalent-Photon Spectrum for Heavy Ion Physics"

We critically discuss the recently developed quantum-mechanical equivalent photon spectrum by Benesh et al. We point out that the key point, the strong absorption in heavy ion collisions, is not treated adequately. Conclusions drawn from such a spectrum are invalid. Equivalent photon spectra appropriate for heavy ions, have been given before in quantal as well as semiclassical versions and were found to be very satisfactory.Comment: 3 pages, LaTe