30 research outputs found
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
Production in Peripheral Heavy-Ion Collisions
We estimate the impact parameter dependence of the production cross section
for and mesons in peripheral heavy-ion collisions collisions.
Total and elastic 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
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
fusion they include also electromagnetic interactions
and strong nucleon-nucleon interactions in grazing collisions. All these
processes are characterised by low multiplicities of produced particles.
and 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
events. The possibility of selecting mesons produced in
fusion events via different 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
Parental palliative cancer: psychosocial adjustment and health-related quality of life in adolescents participating in a German family counselling service
Ausschluss von Elektron-Positron-Resonanzen im Rahmen der Quantenelektrodynamik oberhalb der doppelten Elektronenmasse
SIGLETIB Hannover: DR 8315 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman