Suppression of Heavy Ion gamma gamma Production of the Higgs by Coulomb Dissociation

Predicted two-photon Higgs production with heavy ions at LHC is shown to be reduced due to the large Coulomb dissociation cross section. Incorporating the effect of dissociation reduces the production of a 100 GeV Higgs by about a factor of three compared to rates in the literature calculated without this effect.Comment: 5 pages, latex, revtex source, two postscript figure

η\eta Production in Peripheral Heavy-Ion Collisions

We estimate the impact parameter dependence of the production cross section for $\eta_c$ and $\eta_b$ mesons in peripheral heavy-ion collisions collisions. Total and elastic $\gamma\gamma$ cross sections are calculated in an equivalent photon approximation.Comment: 9 pages, uuencoded postscrip

Inclusive meson production in peripheral collisions of ultrarelativistic heavy ions

There exist several proposals to use Weizs\"{a}cker-Williams photons generated by ultrarelativistic heavy ions to produce exotic particles in $\gamma\gamma$ fusion reactions. To estimate the background conditions for such reactions we analyze various mechanisms of meson production in very peripheral collisions of ultrarelativistic heavy ions at RHIC and LHC energies. Besides $\gamma\gamma$ fusion they include also electromagnetic $\gamma A$ interactions and strong nucleon-nucleon interactions in grazing $AA$ collisions. All these processes are characterised by low multiplicities of produced particles. $\gamma A$ and $AA$ events are simulated by corresponding Monte Carlo codes, RELDIS and FRITIOF. In each of these processes a certain fraction of pions is produced close to the mid-rapidity region that gives a background for the $\gamma\gamma$ events. The possibility of selecting mesons produced in $\gamma\gamma$ fusion events via different $p_t$ cut procedures is demonstrated.Comment: 27 pages with 4 eps-figures included, uses axodraw.sty Tab.2 and 3 correcte

Exclusive Production of Higgs Bosons in Hadron Colliders

We study the exclusive, double--diffractive production of the Standard Model Higgs particle in hadronic collisions at LHC and FNAL (upgraded) energies. Such a mechanism would provide an exceptionally clean signal for experimental detection in which the usual penalty for triggering on the rare decays of the Higgs could be avoided. In addition, because of the color singlet nature of the hard interaction, factorization is expected to be preserved, allowing the cross--section to be related to similar hard--diffractive events at HERA. Starting from a Fock state expansion in perturbative QCD, we obtain an estimate for the cross section in terms of the gluon structure functions squared of the colliding hadrons. Unfortunately, our estimates yield a production rate well below what is likely to be experimentally feasible.Comment: 17 pages, RevTeX file, four uufiled PostScript figures. UMPP #94-177. (Revised version. Some mistakenly missing Feynman diagrams are now added. Results do not change qualitatively. Paper reorganized.

Photon-Photon and Pomeron-Pomeron Processes in Peripheral Heavy Ion Collisions

We estimate the cross sections for the production of resonances, pion pairs and a central cluster of hadrons in peripheral heavy-ion collisions through two-photon and double-pomeron exchange, at energies that will be available at RHIC and LHC. The effect of the impact parameter in the diffractive reactions is introduced, and imposing the condition for realistic peripheral collisions we verify that in the case of very heavy ions the pomeron-pomeron contribution is indeed smaller than the electromagnetic one. However, they give a non-negligible background in the collision of light ions. This diffractive background will be more important at RHIC than at LHC.Comment: 22 pages, 1 Postscript figures, 4 tables, to appear in Phys. Rev.

Photon-Photon Physics in Very Peripheral Collisions of Relativistic Heavy Ions

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. It is the purpose of this review to discuss 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. Special care is taken to include the effects of strong interactions and nuclear size. 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. Photonuclear reactions and other important background effects, especially diffractive processes are also discussed. A special chapter is devoted to lepton-pair production, especially electron-positron pair production; due to the strong fields new phenomena, especially multiple e+-e- pair production, will occur there.Comment: 40 pages, 19 figures, Topical Review, to appear in Journal of Physics G, revised text, updated text/references, one figure replace

Strolling along gauge theory vacua

We consider classical, pure Yang-Mills theory in a box. We show how a set of static electric fields that solve the theory in an adiabatic limit correspond to geodesic motion on the space of vacua, equipped with a particular Riemannian metric that we identify. The vacua are generated by spontaneously broken global gauge symmetries, leading to an infinite number of conserved momenta of the geodesic motion. We show that these correspond to the soft multipole charges of Yang-Mills theory.Comment: 46 pages, 1 figure, Published versio

Ausschluss von Elektron-Positron-Resonanzen im Rahmen der Quantenelektrodynamik oberhalb der doppelten Elektronenmasse

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