234 research outputs found

### Invisible Events with Radiative Photons at LEP

A study of the radiative neutrino counting reaction $e^+ e^- \to \nu {\bar
\nu} \gamma$ at LEP1 and LEP2 energies is presented. An approximate expression
for the spectrum of the observed photon is derived within the framework of the
$p_t$-dependent structure function approach. This is compared with an exact
expression and found in agreement within the foreseen experimental accuracy.
This model describing single-photon radiation can be applied to the more
general case of initial-state single-photon emission accompanying invisible
final-state events. Higher-order QED corrections due to undetected
initial-state radiation are also included. The implementation in a Monte Carlo
event generator is briefly described.Comment: 10 pages, LaTeX, 7 figures available via anonymous ftp at:
ftp://cobra1.pv.infn.it/pub/phot/, files fig#n.ps with #=1,...,

### A Path Integral Way to Option Pricing

An efficient computational algorithm to price financial derivatives is
presented. It is based on a path integral formulation of the pricing problem.
It is shown how the path integral approach can be worked out in order to obtain
fast and accurate predictions for the value of a large class of options,
including those with path-dependent and early exercise features. As examples,
the application of the method to European and American options in the
Black-Scholes model is illustrated. A particularly simple and fast
semi-analytical approximation for the price of American options is derived. The
results of the algorithm are compared with those obtained with the standard
procedures known in the literature and found to be in good agreement.Comment: 20 pages, 2 figures, 3 table

### ${\cal O} (\alpha^2)$ Next-to-Leading Photonic Corrections to Small-Angle Bhabha Scattering in the Structure Function Formalism

A general method for computing ${\cal O} (\alpha^2)$ and higher-order
next-to-leading photonic corrections is presented and applied to the precision
calculation of the small-angle Bhabha scattering cross section in the
phase-space region of interest for the luminosity measurement at LEP. The
formulation is based on a proper matching of exact $\cal O (\alpha)$ results
with higher-order corrections in the Structure Function formalism. The results
of the approach are analytically compared with theoretical calculations, both
for $s$- and $t$-channel processes, available for simple Event Selections.
Numerical predictions for realistic Event Selections are also provided and
critically compared with the ones existing in the literature.Comment: 16 pages, gzip'ed uuencoded tar fil

### Distinguishing New Physics Scenarios at a Linear Collider with Polarized Beams

Numerous non-standard dynamics are described by contact-like effective
interactions that can manifest themselves through deviations of the cross
sections from the Standard Model predictions. If one such deviation were
observed, one should try to identify to a given confidence level the actual
source among the possible non-standard interactions that in principle can
explain it. We here estimate the potential identification reach on different
New Physics effective interactions, obtainable from the angular distributions
of lepton pair production processes at the planned International Linear
Collider with polarized beams. The models discussed are the interactions based
on gravity in large and in TeV^{-1} extra dimensions and the
compositeness-inspired four-fermion contact interactions. The availability of
both beams polarized in many cases plays an essential role in enhancing the
identification sensitivity.Comment: 21 pages, LaTex, 11 figures. One author was missing from the previous
version. The authors list has been completed, no other change

### Six-Fermion Calculation of Intermediate-mass Higgs Boson Production at Future $e^+ e^-$ Colliders

The production of an intermediate-mass Higgs boson in processes of the kind
$e^+ e^- \to 6$ fermions at the energies of future linear colliders is studied.
The recently developed and fully automatic algorithm/code ALPHA is used to
compute the tree-level scattering amplitudes for the reactions $e^+ e^- \to
\mu^+ \mu^- \tau^- \bar\nu_{\tau} u \bar d, \mu^+ \mu^- e^- \bar\nu_{e} u \bar
d$. The code has been interfaced with the Monte Carlo program HIGGSPV/WWGENPV,
properly adapted to 6-fermion production, in order to provide realistic
results, both in the form of cross sections and event samples at the partonic
level. Phenomenological results, that incorporate the effects of initial-state
radiation and beamstrahlung, are shown and commented, emphasizing the
potentials of full six-fermion calculations for precise background evaluation
as well as for detailed studies of the fundamental properties of the Higgs
particle.Comment: 31 pages, LaTeX, 15 eps low-resolution figures include

### Relativistic Spontaneous Localization: A Proposal

A new proposal for a Lorentz-invariant spontaneous localization theory is presented. It is based on the choice of a suitable set of macroscopic quantities to be stochastically induced to have definite values. Such macroscopic quantities have the meaning of a time-integrated amount of a microscopically defined quantity called stuff related to the presence of massive particles

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