4 research outputs found
Production Associated to Rare Events in High Energy Hadron-Hadron Collisions
At very high energy the same universal relation between the multiparticle or
the transverse energy distribution associated to a rare event , and
the corresponding minimum bias distribution P, , or works for nucleus-nucleus collisions as well as
for hadron-hadron collisions. This suggests that asymptotically, all hadronic
processes are similar.Comment: 9 pages, 4 Postscript figure
Multiplicity and Transverse Energy Distributions Associated to Rare Events in Nucleus-Nucleus Collisions
We show that in high energy nucleus-nucleus collisions the transverse energy
or multiplicity distribution P_C, associated to the production of a rare,
unabsorbed event C, is universally related to the standard or minimum bias
distribution P by the equation , with and or n. Deviations from this formula are discussed,
in particular having in view the formation of the plasma of quarks and gluons.
This possibility can be distinguished from absortion or interaction of
comovers, looking at the curvature of the over Drell-Yan pairs as a
function of E_T.Comment: 8 pages, 4 Postscript figure
Bethe-Salpeter Approach for Unitarized Chiral Perturbation Theory
The Bethe-Salpeter equation restores exact elastic unitarity in the
channel by summing up an infinite set of chiral loops. We use this equation to
show how a chiral expansion can be undertaken in the two particle irreducible
amplitude and the propagators accomplishing exact elastic unitarity at any
step. Renormalizability of the amplitudes can be achieved by allowing for an
infinite set of counter-terms as it is the case in ordinary Chiral Perturbation
Theory. Crossing constraints can be imposed on the parameters to a given order.
Within this framework, we calculate the leading and next-to-leading
contributions to the elastic scattering amplitudes, for all isospin
channels, and to the vector and scalar pion form factors in several
renormalization schemes. A satisfactory description of amplitudes and form
factors is obtained. In this latter case, Watson's theorem is automatically
satisfied. From such studies we obtain a quite accurate determination of some
of the ChPT low energy parameters ({\bar l}_1 - {\bar l}_2 =
-6.1\er{0.1}{0.3} and ). We also compare the two
loop piece of our amplitudes to recent two--loop calculations.Comment: 63 pages, 9 figures. Some discussions on off-shell ambiguities and
convergence of the expansion adde