174,347 research outputs found
Dark matter from gravitational particle production at reheating
We show that curvature induced particle production at reheating generates
adiabatic dark matter if there are non-minimally coupled spectator scalars
weakly coupled to visible matter. The observed dark matter abundance implies an
upper bound on spectator masses and non-minimal coupling values . For
example, assuming quadratic inflation, instant reheating and a single spectator
scalar with only gravitational couplings, the observed dark matter abundance is
obtained for GeV and . Larger mass and coupling values
of the spectator are excluded as they would lead to overproduction of dark
matter.Comment: 10 pages, 1 figure. v2: updated references. v3: substantial
modifications, results and conclusions partially changed but bounds on
spectator fields almost unaffected. New title. v4: expanded discussion,
accepted for publication in JCA
On the participant-spectator matter and thermalization of neutron-rich systems in heavy-ion collisions
We study the participant-spectator matter at the energy of vanishing flow for
neutron-rich systems. Our study reveals similar behaviour of
articipant-spectator for neutron-rich systems as for stable systems and also
points towards nearly mass independence behaviour of participant-spectator
matter for neutron-rich systems at the energy of vanishing flow. We also study
the thermalization reached in the reactions of neutron-rich systems
Tagged spectator deep-inelastic scattering off the deuteron as a tool to study neutron structure
We give an overview of a model to describe deep-inelastic scattering (DIS)
off the deuteron with a spectator proton, based on the virtual nucleon
approximation (VNA). The model accounts for the final-state interactions (FSI)
of the DIS debris with the spectator proton. Values of the rescattering cross
section are obtained by fits to high-momentum spectator data. By using the
so-called "pole extrapolation method", free neutron structure functions can be
obtained by extrapolating low-momentum spectator proton data to the on-shell
neutron pole. We apply this method to the BONuS data set and find a surprising
Bjorken dependence, indicating a possible rise of the neutron to proton
structure function ratio at high .Comment: 6 pages, 4 figures, proceedings of POETIC
Dialectical Polyptych: an interactive movie installation
Most of the known video games developed by important software companies usually establish an
approach to the cinematic language in an attempt to create a perfect combination of narrative,
visual technique and interaction. Unlike most video games, interactive film narratives normally
involve an interruption in time whenever the spectator has to make choices. “Dialectical
Polyptych” is an interactive movie included in a project called “Characters looking for a spectactor”, which aims to give the spectator on-the-fly control over film editing, thus exploiting the
role of the spectator as an active subject in the presented narrative. This paper presents an
installation based on a mobile device, which allows seamless real-time interactivity with the
movie. Different finger touches in the screen allow the spectator to alternate between two
parallel narratives, both producing a complementary narrative, and change the angle or shot
within each narrative.info:eu-repo/semantics/publishedVersio
Polarized light ions and spectator nucleon tagging at EIC
An Electron-Ion Collider (EIC) with suitable forward detection capabilities
would enable a unique experimental program of deep-inelastic scattering (DIS)
from polarized light nuclei (deuterium 2H, helium 3He) with spectator nucleon
tagging. Such measurements promise significant advances in several key areas of
nuclear physics and QCD: (a) neutron spin structure, by using polarized
deuterium and eliminating nuclear effects through on-shell extrapolation in the
spectator proton momentum; (b) quark/gluon structure of the bound nucleon at x
> 0.1 and the dynamical mechanisms acting on it, by measuring the spectator
momentum dependence of nuclear structure functions; (c) coherent effects in
QCD, by exploring shadowing in tagged DIS on deuterium at x << 0.1. The JLab
MEIC design (CM energy sqrt{s} = 15-50 GeV/nucleon, luminosity ~ 10^{34}
cm^{-2} s^{-1}) provides polarized deuterium beams and excellent coverage and
resolution for forward spectator tagging. We summarize the physics topics, the
detector and beam requirements for spectator tagging, and on-going R&D efforts.Comment: 6 pages, 2 figures. Prepared for proceedings of DIS 2014, XXII.
International Workshop on Deep-Inelastic Scattering and Related Subjects,
University of Warsaw, Poland, April 28 - May 2, 201
Endpoint behavior of high-energy scattering cross sections
In high-energy processes near the endpoint, there emerge new contributions
associated with spectator interactions. Away from the endpoint region, these
new contributions are suppressed compared to the leading contribution, but the
leading contribution becomes suppressed as we approach the endpoint and the new
contributions become comparable. We present how the new contributions scale as
we reach the endpoint and show that they are comparable to the suppressed
leading contributions in deep-inelastic scattering by employing a power
counting analysis. The hadronic tensor in deep-inelastic scattering is shown to
factorize including the spectator interactions, and it can be expressed in
terms of the lightcone distribution amplitudes of initial hadrons. We also
consider the contribution of the spectator contributions in Drell-Yan
processes. Here the spectator interactions are suppressed compared to double
parton annihilation according to the power counting.Comment: 21 pages, 5 figures, published versio
Spectator Effects during Leptogenesis in the Strong Washout Regime
By including spectator fields into the Boltzmann equations for Leptogenesis,
we show that partially equilibrated spectator interactions can have a
significant impact on the freeze-out value of the asymmetry in the strong
washout regime. The final asymmetry is typically increased, since partially
equilibrated spectators "hide" a part of the asymmetry from washout. We study
examples with leptonic and non-leptonic spectator processes, assuming thermal
initial conditions, and find up to 50% enhanced asymmetries compared to the
limit of fully equilibrated spectators. Together with a comprehensive overview
of the equilibration temperatures for various Standard Model processes, the
numerical results indicate the ranges when the limiting cases of either fully
equilibrated or negligible spectator fields are applicable and when they are
not. Our findings also indicate an increased sensitivity to initial conditions
and finite density corrections even in the strong washout regime.Comment: 23 pages, 4 figure
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