3,282 research outputs found
QCD Interconnection Studies at Linear Colliders
Heavy objects like the W, Z and t are short-lived compared with typical
hadronization times. When pairs of such particles are produced, the subsequent
hadronic decay systems may therefore become interconnected. We study such
potential effects at Linear Collider energies.Comment: 1+7 pages, 6 figure
QCD Interconnection Effects
Heavy objects like the W, Z and t are short-lived compared with typical
hadronization times. When pairs of such particles are produced, the subsequent
hadronic decay systems may therefore become interconnected. We study such
potential effects at Linear Collider energies.Comment: 1+4 pages, no figures, to appear in the Proceedings of the
International Workshop on Linear Colliders, Sitges (Barcelona), Spain, April
28 - May 5, 199
A scenario for high-energy gamma-gamma interactions
A real photon has a complicated nature, whereby it may remain unresolved or
fluctuate into a vector meson or a perturbative q-qbar pair. In gamma-gamma
events, this gives three by three combinations of the nature of the two
incoming photons, and thus six distinct event classes. The properties of these
classes are partly constrained by the choices already made in our related
gamma-p model. It is therefore possible to predict the energy-dependence of the
cross section for each of the six components separately. The total cross
section gives support to the idea that a simple factorized ansatz with a
pomeron and a reggeon term can be a good approximation. Event properties
undergo a stepwise evolution from p-p to gamma-p to gamma-gamma events, with
larger charged multiplicity, more transverse energy flow and a higher jet rate
in the latter process.Comment: 1+27 pages, LaTeX2e, 20 ps/eps figures included in file using
filecontents environment
Forward-Backward Correlations and Event Shapes as probes of Minimum-Bias Event Properties
Measurements of inclusive observables, such as particle multiplicities and
momentum spectra, have already delivered important information on
soft-inclusive ("minimum-bias") physics at the Large Hadron Collider. In order
to gain a more complete understanding, however, it is necessary to include also
observables that probe the structure of the studied events. We argue that
forward-backward (FB) correlations and event-shape observables may be
particulary useful first steps in this respect. We study the sensitivity of
several different types of FB correlations and two event shape variables -
transverse thrust and transverse thrust minor - to various sources of
theoretical uncertainty: multiple parton interactions, parton showers, colour
(re)connections, and hadronization. The power of each observable to furnish
constraints on Monte Carlo models is illustrated by including comparisons
between several recent, and qualitatively different, PYTHIA 6 tunes, for pp
collisions at sqrt(s) = 900 GeV.Comment: 13 page
Tevatron Discovery Potential for Fourth Generation Neutrinos: Dirac, Majorana and Everything in Between
We analyze the power of the Tevatron dataset to exclude or discover fourth
generation neutrinos. In a general framework, one can have mixed left- and
right-handed neutrinos, with Dirac and Majorana neutrinos as extreme cases. We
demonstrate that a single Tevatron experiment can make powerful statements
across the entire mixing space, extending LEP's mass limits of 60-80 GeV up to
150-175 GeV, depending on the mixing.Comment: 4 pages, pdflate
Revisiting Constraints on Fourth Generation Neutrino Masses
We revisit the current experimental bounds on fourth-generation Majorana
neutrino masses, including the effects of right handed neutrinos. Current
bounds from LEPII are significantly altered by a global analysis. We show that
the current bounds on fourth generation neutrinos decaying to eW and mu W can
be reduced to about 80 GeV (from the current bound of 90 GeV), while a neutrino
decaying to tau W can be as light as 62.1 GeV. The weakened bound opens up a
neutrino decay channel for intermediate mass Higgs, and interesting
multi-particle final states for Higgs and fourth generation lepton decays.Comment: 7 pages 1 fi
Energy Scaling of Minimum-Bias Tunes
We propose that the flexibility offered by modern event-generator tuning
tools allows for more than just obtaining "best fits" to a collection of data.
In particular, we argue that the universality of the underlying physics model
can be tested by performing several, mutually independent, optimizations of the
generator parameters in different physical regions. For regions in which these
optimizations return similar and self-consistent parameter values, the model
can be considered universal. Deviations from this behavior can be associated
with a breakdown of the modeling, with the nature of the deviations giving
clues as to the nature of the breakdown. We apply this procedure to study the
energy scaling of a class of minimum-bias models based on multiple parton
interactions (MPI) and pT-ordered showers, implemented in the Pythia 6.4
generator. We find that a parameter controlling the strength of color
reconnections in the final state is the most important source of
non-universality in this model.Comment: 17 pages, 3 figures, 4 table
Resonance-free Region in scattering by a strictly convex obstacle
We prove the existence of a resonance free region in scattering by a strictly
convex obstacle with the Robin boundary condition. More precisely, we show that
the scattering resonances lie below a cubic curve which is the same as in the
case of the Neumann boundary condition. This generalizes earlier results on
cubic poles free regions obtained for the Dirichlet boundary condition.Comment: 29 pages, 2 figure
Inverse Slope Systematics in High-Energy p+p and Au+Au Reactions
We employ the Monte-Carlo PYTHIA to calculate the transverse mass spectra of
various hadrons and their inverse slopes T* at m_T-m=1.5-2 GeV in p+p reactions
at sqrt(s)=200 GeV. Due to (multiple) minijet production T* increases as a
function of the hadron mass. Moreover, the T*(m) systematics has a
``discontinuity'' at the charm threshold, i.e. the inverse slope of D-mesons is
much higher than that of non-charmed hadrons and even of the heavier Lambda_C
baryon. The experimental observation of this characteristic behaviour in Au+Au
collisions would indicate the absence of c-quark rescattering. In contrast, the
assumption of thermalized partons and hydrodynamical evolution would lead to a
smoothly increasing T*(m), without discontinuity at the charm threshold. The
degree of collective transverse flow, indicated by the slope of the T*(m)
systematics, depends strongly on whether kinetic equilibrium is maintained for
some time after hadronization or not.Comment: 14 pages, 2 figures, REVTEX; mistake in plot of c-quark
mt-distribution corrected, some references adde
On the Exponential Decay of the n-point Correlation Functions and the Analyticity of the Pressure
The goal of this paper is to provide estimates leading to a direct proof of
the exponential decay of the n-point correlation functions for certain
unbounded models of Kac type. The methods are based on estimating higher order
derivatives of the solution of the Witten Laplacian equation on one forms
associated with the hamiltonian of the system. We also provide a formula for
the Taylor coefficients of the pressure that is suitable for a direct proof the
analyticity
- …