1,447 research outputs found
The Precision Determination of Invisible-Particle Masses at the LHC
We develop techniques to determine the mass scale of invisible particles
pair-produced at hadron colliders. We employ the constrained mass variable
m_2C, which provides an event-by-event lower-bound to the mass scale given a
mass difference. We complement this variable with a new variable m_2C,UB which
provides an additional upper bound to the mass scale, and demonstrate its
utility with a realistic case study of a supersymmetry model. These variables
together effectively quantify the `kink' in the function Max m_T2 which has
been proposed as a mass-determination technique for collider-produced dark
matter. An important advantage of the m_2C method is that it does not rely
simply on the position at the endpoint, but it uses the additional information
contained in events which lie far from the endpoint. We found the mass by
comparing the HERWIG generated m_2C distribution to ideal distributions for
different masses. We find that for the case studied, with 100 fb^-1 of
integrated luminosity (about 400 signal events), the invisible particle's mass
can be measured to a precision of 4.1 GeV. We conclude that this technique's
precision and accuracy is as good as, if not better than, the best known
techniques for invisible-particle mass-determination at hadron colliders.Comment: 20 pages, 11 figures, minor correction
Phenomenological Analysis of and Elastic Scattering Data in the Impact Parameter Space
We use an almost model-independent analytical parameterization for and
elastic scattering data to analyze the eikonal, profile, and
inelastic overlap functions in the impact parameter space. Error propagation in
the fit parameters allows estimations of uncertainty regions, improving the
geometrical description of the hadron-hadron interaction. Several predictions
are shown and, in particular, the prediction for inelastic overlap
function at TeV shows the saturation of the Froissart-Martin
bound at LHC energies.Comment: 15 pages, 16 figure
Global Analysis of Nucleon Strange Form Factors at Low
We perform a global analysis of all recent experimental data from elastic
parity-violating electron scattering at low . The values of the electric
and magnetic strange form factors of the nucleon are determined at
GeV/ to be and .Comment: 8 pages, 1 figur
Applicability of a Representation for the Martin's Real-Part Formula in Model-Independent Analyses
Using a novel representation for the Martin's real-part formula without the
full scaling property, an almost model-independent description of the
proton-proton differential cross section data at high energies (19.4 GeV - 62.5
GeV) is obtained. In the impact parameter and eikonal frameworks, the extracted
inelastic overlap function presents a peripheral effect (tail) above 2 fm and
the extracted opacity function is characterized by a zero (change of sign) in
the momentum transfer space, confirming results from previous model-independent
analyses. Analytical parametrization for these empirical results are introduced
and discussed. The importance of investigations on the inverse problems in
high-energy elastic hadron scattering is stressed and the relevance of the
proposed representation is commented. A short critical review on the use of
Martin's formula is also presented.Comment: Two comments and one reference added at the end of Subsec. 3.3; 23
pages, 9 figures; to be published in Int. J. Mod. Phys.
Zeeman Relaxation of Cold Atomic Iron and Nickel in Collisions with 3He
We have measured the ratio of the diffusion cross-section to the angular
momentum reorientation cross-section in the colliding Fe-3He and Ni-3He
systems. Nickel (Ni) and iron (Fe) atoms are introduced via laser ablation into
a cryogenically cooled experimental cell containing cold (< 1 K) 3He buffer
gas. Elastic collisions rapidly cool the translational temperature of the
ablated atoms to the helium temperature. The cross-section ratio is extracted
by measuring the decays of the atomic Zeeman sublevels. For our experimental
conditions, thermal energy is comparable to the Zeeman splitting. As a result,
thermal excitations between Zeeman sublevels significantly impact the observed
decay. To determine the cross-section ratio accurately, we introduce a model of
Zeeman state dynamics that includes thermal excitations. We find the
cross-section ratio for Ni-3He = 5 x 10^3 and Fe-3He <= 3 x 10^3 at 0.75 K in a
0.8 T magnetic field. These measurements are interpreted in the context of
submerged shell suppression of spin relaxation as studied previously in
transition metals and rare earth atoms.Comment: 10 pages, 5 figures; submitted to Phys. Rev.
Three-dimensional simulations of rotationally-induced line variability from a Classical T Tauri star with a misaligned magnetic dipole
We present three-dimensional (3-D) simulations of rotationally induced line
variability arising from complex circumstellar environment of classical T Tauri
stars (CTTS) using the results of the 3-D magnetohydrodynamic (MHD) simulations
of Romanova et al., who considered accretion onto a CTTS with a misaligned
dipole magnetic axis with respect to the rotational axis. The density, velocity
and temperature structures of the MHD simulations are mapped on to the
radiative transfer grid, and corresponding line source function and the
observed profiles of neutral hydrogen lines (H-beta, Pa-beta and Br-gamma) are
computed using the Sobolev escape probability method. We study the dependency
of line variability on inclination angles (i) and magnetic axis misalignment
angles (Theta). By comparing our models with the Pa-beta profiles of 42 CTTS
observed by Folha & Emerson, we find that models with a smaller misaligngment
angle (Theta<~15 deg.) are more consistent with the observations which show
that majority of Pa-beta are rather symmetric around the line centre. For a
high inclination system with a small dipole misalignment angle (Theta ~ 15
deg.), only one accretion funnel (on the upper hemisphere) is visible to an
observer at any given rotational phase. This can cause an anti-correlation of
the line equivalent width in the blue wing (v0)
over a half of a rotational period, and a positive correlation over other half.
We find a good overall agreement of the line variability behaviour predicted by
our model and those from observations. (Abridged)Comment: 15 pages, 13 figures. Accepted for publication in MNRAS. A version
with full resolution figures can be downloaded from
http://www.physics.unlv.edu/~rk/preprint/inclined_dipole.pd
Mobile tools for Windows: user guide : report produced in the context of the Inventory Data Capture Tools Risk Global Component
The aim of this document is to provide guidelines for the use of the digital Windows Mobile Tools that have been designed and built to collect building inventory pre- and post-earthquake events. The guide instructs users how to install the software on a Windows device and provides step-by-step instructions for collecting and managing the data that has been collected.
It is expected that the field staff are already experts in collecting building inventory, therefore this guide does not provides instructions how to recognise or understand building structural components.
Appendices to this guide also include the following:
A copy of the paper Forms that are used to collect data in the field if the digital Mobile Tools are unavailable
The Photos-4-GEM Protocol that provides guidance for photography of structures in the context of the Inventory Data Capture Tools and the GEM Taxonomy
Carrier thermal escape in families of InAs/InP self-assembled quantum dots
We investigate the thermal quenching of the multimodal photoluminescence from
InAs/InP (001) self-assembled quantum dots. The temperature evolution of the
photoluminescence spectra of two samples is followed from 10 K to 300 K. We
develop a coupled rate-equation model that includes the effect of carrier
thermal escape from a quantum dot to the wetting layer and to the InP matrix,
followed by transport, recapture or non-radiative recombination. Our model
reproduces the temperature dependence of the emission of each family of quantum
dots with a single set of parameters. We find that the main escape mechanism of
the carriers confined in the quantum dots is through thermal emission to the
wetting layer. The activation energy for this process is found to be close to
one-half the energy difference between that of a given family of quantum dots
and that of the wetting layer as measured by photoluminescence excitation
experiments. This indicates that electron and holes exit the InAs quantum dots
as correlated pairs
Measurement of the temperature of an ultracold ion source using time-dependent electric fields
We report on a measurement of the characteristic temperature of an ultracold
rubidium ion source, in which a cloud of laser-cooled atoms is converted to
ions by photo-ionization. Extracted ion pulses are focused on a detector with a
pulsed-field technique. The resulting experimental spot sizes are compared to
particle-tracking simulations, from which a source temperature
mK and the corresponding transversal reduced emittance m rad are determined. We find that this result is
likely limited by space charge forces even though the average number of ions
per bunch is 0.022.Comment: 8 pages, 11 figure
Control of polarization rotation in nonlinear propagation of fully-structured light
Knowing, and controlling, the spatial polarization distribution of a beam is of importance in applications such as optical tweezing, imaging, material processing and communications. Here we show how the polarization distribution is affected by both linear and nonlinear (self-focussing) propagation. We derive an analytical ex- pression for the polarization rotation of fully-structured light (FSL) beams during linear propagation and show that the observed rotation is due entirely to the difference in Gouy phase between the two eigenmodes comprising the FSL beams, in excellent agreement with numerical simulations. We also explore the effect of cross-phase modulation due to self-focusing (Kerr) nonlinearity and show that polarization rotation can be controlled by changing the eigenmodes of the superposition, and physical parameters such as the beam size, the amount of Kerr nonlinearity and the input power. Finally, we show that by biasing cylindrical vector (CV) beams to have elliptical polarization, we can vary the polarization state from radial through spiral to azimuthal using nonlinear propagation
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