2,988 research outputs found
Creating semiclassical black holes in collider experiments and keeping them on a string
We argue that a simple modification of the TeV scale quantum gravity scenario
allows production of semiclassical black holes in particle collisions at the
LHC. The key idea is that in models with large extra dimensions the strength of
gravity in the bulk can be higher than on the brane where we live. A well-known
example of this situation is the case of warped extra dimensions. Even if the
energy of the collision is not sufficient to create a black hole on the brane,
it may be enough to produce a particle which accelerates into the bulk up to
trans-Planckian energy and creates a large black hole there. In a concrete
model we consider, the black hole is formed in a collision of the particle with
its own image at an orbifold plane. When the particle in question carries some
Standard Model gauge charges the created black hole gets attached to our brane
by a string of the gauge flux. For a 4-dimensional observer such system looks
as a long-lived charged state with the mass continuously decreasing due to
Hawking evaporation of the black hole. This provides a distinctive signature of
black hole formation in our scenario.Comment: Journal version, a misprint correcte
Spectacle lens fabrication in an optometric practice
Recently many of our classmates have asked questions concerning the actual set-up of an ophthalmic lens fabrication lab in an optometric practice. Our colleagues and peers not only want to know about feasibility, investment, space, equipment, and prices, but also how to perform the actual process of spectacle making. As graduating optometrists some of our classmates will enter into an association with an older established optometrist and some will go into solo practice. In either case one of their duties may be doing the actual lab work in spectacle fabrication. This is very common practice in the current optometric community.
As more and more optometrists become involved with lab work, the need for a manual of this type is obvious. A literature search proved fruitless in obtaining any source that covers the breadth and scope of the edging process in its entirety. Optometric and optician\u27s publications sometimes deal with various aspects of the spectacle fabrication process, but we have found these to be too general and in the style of an overview or snapshot . We were unable to find any source containing the actual mechanisms involved.
A previous research project involved a video tape of the edging process from a local laboratory, and was aimed toward explaining how the edging process is accomplished. We feel that the tape was good in that it oriented the viewer as to how this is done . However, the thrust of our project is to explain, step-by-step, how to edge lenses in an optometric office. The manual will be written from the perspective of How to do it , rather than how it is done .
To our knowledge, this work will be the first of its kind, and will represent a compilation of technical information obtained from manufacturers of laboratory equipment, combined with textbook information, and original writings based on our training and experience as laboratory 1 opticians. The authors do not intend this manual to be a statement saying that professional optometrists should spend their time edging lenses. To the contrary, we feel that the optometrist should spend his/her time doing what he/she was trained to do, that is, providing vision care. If however, a spectacle fabrication lab is to be incorporated into an optometric practice, two things are necessary. First, the optometrist needs to know the processes involved as well as the equipment required in order to set up the lab. Second, he/she needs a working knowledge of the basic mechanics and procedures involved, in order to train personnel if necessary
Long-Lived Neutralino NLSPs
We investigate the collider signatures of heavy, long-lived, neutral
particles that decay to charged particles plus missing energy. Specifically, we
focus on the case of a neutralino NLSP decaying to Z and gravitino within the
context of General Gauge Mediation. We show that a combination of searches
using the inner detector and the muon spectrometer yields a wide range of
potential early LHC discoveries for NLSP lifetimes ranging from 10^(-1)-10^5
mm. We further show that events from Z(l+l-) can be used for detailed kinematic
reconstruction, leading to accurate determinations of the neutralino mass and
lifetime. In particular, we examine the prospects for detailed event study at
ATLAS using the ECAL (making use of its timing and pointing capabilities)
together with the TRT, or using the muon spectrometer alone. Finally, we also
demonstrate that there is a region in parameter space where the Tevatron could
potentially discover new physics in the delayed Z(l+l-)+MET channel. While our
discussion centers on gauge mediation, many of the results apply to any
scenario with a long-lived neutral particle decaying to charged particles.Comment: 31 pages, 12 figure
A review of Quantum Gravity at the Large Hadron Collider
The aim of this article is to review the recent developments in the
phenomenology of quantum gravity at the Large Hadron Collider. We shall pay
special attention to four-dimensional models which are able to lower the
reduced Planck mass to the TeV region and compare them to models with a large
extra-dimensional volume. We then turn our attention to reviewing the emission
of gravitons (massless or massive) at the LHC and to the production of small
quantum black holes.Comment: 32 pages, invited revie
RECAST: Extending the Impact of Existing Analyses
Searches for new physics by experimental collaborations represent a
significant investment in time and resources. Often these searches are
sensitive to a broader class of models than they were originally designed to
test. We aim to extend the impact of existing searches through a technique we
call 'recasting'. After considering several examples, which illustrate the
issues and subtleties involved, we present RECAST, a framework designed to
facilitate the usage of this technique.Comment: 13 pages, 4 figure
Surface energy and stability of stress-driven discommensurate surface structures
A method is presented to obtain {\it ab initio} upper and lower bounds to
surface energies of stress-driven discommensurate surface structures, possibly
non-periodic or exhibiting very large unit cells. The instability of the
stressed, commensurate parent of the discommensurate structure sets an upper
bound to its surface energy; a lower bound is defined by the surface energy of
an ideally commensurate but laterally strained hypothetical surface system. The
surface energies of the phases of the Si(111):Ga and Ge(111):Ga systems and the
energies of the discommensurations are determined within eV.Comment: 4 pages RevTeX. 2 Figures not included. Ask for a hard copy (through
regular mail) to [email protected]
The integration of 'omic' disciplines and systems biology in cattle breeding
Enormous progress has been made in the selection of animals, including cattle, for specific traits using traditional quantitative genetics approaches. Nevertheless, considerable variation in phenotypes remains unexplained, and therefore represents potential additional gain for animal production. In addition, the paradigm shift in new disciplines now being applied to animal breeding represents a powerful opportunity to prise open the 'black box' underlying the response to selection and fully understand the genetic architecture controlling the traits of interest. A move away from traditional approaches of animal breeding toward systems approaches using integrative analysis of data from the 'omic' disciplines represents a multitude of exciting opportunities for animal breeding going forward as well as providing alternatives for overcoming some of the limitations of traditional approaches such as the expressed phenotype being an imperfect predictor of the individual's true genetic merit, or the phenotype being only expressed in one gender or late in the lifetime of an animal. This review aims to discuss these opportunities from the perspective of their potential application and contribution to cattle breeding. Harnessing the potential of this paradigm shift also poses some new challenges for animal scientists - and they will also be discussed
IR Dust Bubbles: Probing the Detailed Structure and Young Massive Stellar Populations of Galactic HII Regions
We present an analysis of wind-blown, parsec-sized, mid-infrared bubbles and
associated star-formation using GLIMPSE/IRAC, MIPSGAL/MIPS and MAGPIS/VLA
surveys. Three bubbles from the Churchwell et al. (2006) catalog were selected.
The relative distribution of the ionized gas (based on 20 cm emission), PAH
emission (based on 8 um, 5.8 um and lack of 4.5 um emission) and hot dust (24
um emission) are compared. At the center of each bubble there is a region
containing ionized gas and hot dust, surrounded by PAHs. We identify the likely
source(s) of the stellar wind and ionizing flux producing each bubble based
upon SED fitting to numerical hot stellar photosphere models. Candidate YSOs
are also identified using SED fitting, including several sites of possible
triggered star formation.Comment: 37 pages, 17 figure
Embedded Star Formation in the Eagle Nebula with Spitzer/GLIMPSE
We present new Spitzer photometry of the Eagle Nebula (M16, containing the
optical cluster NGC 6611) combined with near-infrared photometry from 2MASS. We
use dust radiative transfer models, mid-infrared and near-infrared color-color
analysis, and mid-infrared spectral indices to analyze point source spectral
energy distributions, select candidate young stellar objects (YSOs), and
constrain their mass and evolutionary state. Comparison of the different
protostellar selection methods shows that mid-infrared methods are consistent,
but as has been known for some time, near-infrared-only analysis misses some
young objects. We reveal more than 400 protostellar candidates, including one
massive young stellar object (YSO) that has not been previously highlighted.
The YSO distribution supports a picture of distributed low-level star
formation, with no strong evidence of triggered star formation in the
``pillars''. We confirm the youth of NGC 6611 by a large fraction of
infrared-excess sources, and reveal a younger cluster of YSOs in the nearby
molecular cloud. Analysis of the YSO clustering properties shows a possible
imprint of the molecular cloud's Jeans length. Multiwavelength mid-IR imaging
thus allows us to analyze the protostellar population, to measure the dust
temperature and column density, and to relate these in a consistent picture of
star formation in M16.Comment: 16p preprint - ApJ accepte
General Neutralino NLSPs at the Early LHC
Gauge mediated supersymmetry breaking (GMSB) is a theoretically
well-motivated framework with rich and varied collider phenomenology. In this
paper, we study the Tevatron limits and LHC discovery potential for a wide
class of GMSB scenarios in which the next-to-lightest superpartner (NLSP) is a
promptly-decaying neutralino. These scenarios give rise to signatures involving
hard photons, 's, 's, jets and/or higgses, plus missing energy. In order
to characterize these signatures, we define a small number of minimal spectra,
in the context of General Gauge Mediation, which are parameterized by the mass
of the NLSP and the gluino. Using these minimal spectra, we determine the most
promising discovery channels for general neutralino NLSPs. We find that the
2010 dataset can already cover new ground with strong production for all NLSP
types. With the upcoming 2011-2012 dataset, we find that the LHC will also have
sensitivity to direct electroweak production of neutralino NLSPs.Comment: 26 page
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