24,403 research outputs found
Search for Contact Interactions in the Dimuon Final State at ATLAS
The Standard Model has been successful in describing many fundamental aspects
of particle physics. However, there are some remaining puzzles that are not
explained within the context of its present framework. We discuss the
possibility to discover new physics in the ATLAS Detector via a four-fermion
contact interaction, much in the same way Fermi first described Weak
interactions. Using a simple ratio method on dimuon events, we can set a 95%
C.L. lower limit on the effective scale Lambda = 7.5 TeV (8.7 TeV) for the
constructive Left-left Isoscalar Model of quark compositeness with 100 pb^-1
(200 pb^-1) of data at sqrt{s} = 10 TeV.Comment: To be published in the proceedings of DPF-2009, Detroit, MI, July
2009, eConf C09072
Gas Gain Measurements from a Negative Ion TPC X-ray Polarimeter
Gas-based time projection chambers (TPCs) have been shown to be highly
sensitive X-ray polarimeters having excellent quantum efficiency while at the
same time achieving large modulation factors. To observe polarization of the
prompt X-ray emission of a Gamma-ray burst (GRB), a large area detector is
needed. Diffusion of the electron cloud in a standard TPC could be prohibitive
to measuring good modulation when the drift distance is large. Therefore, we
propose using a negative ion TPC (NITPC) with Nitromethane (CH3NO2) as the
electron capture agent. The diffusion of negative ions is reduced over that of
electrons due to the thermal coupling of the negative ions to the surrounding
gas. This allows for larger area detectors as the drift distance can be
increased without degrading polarimeter modulation. Negative ions also travel
~200 times slower than electrons, allowing the readout electronics to operate
slower, resulting in a reduction of instrument power. To optimize the NITPC
design, we have measured gas gain with SciEnergy gas electron multipliers
(GEMs) in single and double GEM configurations. Each setup was tested with
different gas combinations, concentrations and pressures: P10 700 Torr, Ne+CO2
700 Torr at varying concentrations of CO2 and Ne+CO2+CH3NO2 700 Torr. We report
gain as a function of total voltage, measured from top to bottom of the GEM
stack, and as a function of drift field strength for the gas concentrations
listed above. Examples of photoelectron tracks at 5.9 keV are also presented.Comment: 6 pages, 6 figures, accepted for publication in IEEE Trans Nucl Sc
A basic lock-in amplifier experiment for the undergraduate laboratory
We describe a basic experiment for the undergraduate laboratory that demonstrates aspects of both, the science and the art of precision electronic measurements. The essence of the experiment is to measure the resistance of a small length of brass-wire to high accuracy using a simple voltage divider and a lock-in amplifier. By performing the measurement at different frequencies and different drive currents, one observes various random noise sources and systematic measurement effects
Macroscopic coherence effects in a mesoscopic system: Weak localization of thin silver films in an undergraduate lab
We present an undergraduate lab that investigates weak localization in thin
silver films. The films prepared in our lab have thickness, , between 60-200
\AA, a mesoscopic length scale. At low temperatures, the inelastic dephasing
length for electrons, , exceeds the thickness of the film (), and the films are then quasi-2D in nature. In this situation, theory
predicts specific corrections to the Drude conductivity due to coherent
interference between conducting electrons' wavefunctions, a macroscopically
observable effect known as weak localization. This correction can be destroyed
with the application of a magnetic field, and the resulting magnetoresistance
curve provides information about electron transport in the film. This lab is
suitable for Junior or Senior level students in an advanced undergraduate lab
course.Comment: 16 pages, 9 figures. Replaces earlier version of paper rejected by
Am. J. Phys. because of too much content on vacuum systems. New version deals
with the undergraduate experiment on weak localization onl
Sulphur molecules in the circumstellar envelopes of M-type AGB stars
The sulphur compounds SO and SO have not been widely studied in the
circumstellar envelopes of asymptotic giant branch (AGB) stars. By presenting
and modelling a large number of SO and SO lines in the low mass-loss rate
M-type AGB star R Dor, and modelling the available lines of those molecules in
a further four M-type AGB stars, we aim to determine their circumstellar
abundances and distributions. We use a detailed radiative transfer analysis
based on the accelerated lambda iteration method to model circumstellar SO and
SO line emission and molecular data files for both SO and SO that are
more extensive than those previously available. Using 17 SO lines and 98 SO2
lines to constrain our models for R Dor, we find an SO abundance of
6.7x10 and an SO abundance of 5x10 with both species having
high abundances close to the star. We also modelled SO and found an
abundance of 3.1x10, giving an SO/SO ratio of 21.6. We
derive similar results for the circumstellar SO and SO abundances and their
distributions for the low mass-loss rate object W Hya. For these stars, the
circumstellar SO and SO abundances are much higher than predicted by
chemical models and these two species may account for all available sulphur.
For the higher mass-loss rate stars, we find shell-like SO distributions with
peak abundances that decrease and peak abundance radii that increase with
increasing mass-loss rate. The positions of the peak SO abundance agree very
well with the photodissociation radii of HO. We find evidence that SO is
most likely through the photodissociation of HO and the subsequent reaction
between S and OH. The S-bearing parent molecule appears not to be HS. The
SO models suggest an origin close to the star for this species, also
disagreeing with current chemical models.Comment: 25 page
X-ray polarimetry with an active-matrix pixel proportional counter
We report the first results from an X-ray polarimeter with a micropattern gas
proportional counter using an amorphous silicon active matrix readout. With
100% polarized X-rays at 4.5 keV, we obtain a modulation factor of 0.33 +/-
0.03, confirming previous reports of the high polarization sensitivity of a
finely segmented pixel proportional counter. The detector described here has a
geometry suitable for the focal plane of an astronomical X-ray telescope.
Amorphous silicon readout technology will enable additional extensions and
improvements.Comment: 4 pages, 4 figures, 1 tabl
Health and education provider collaboration to deliver adolescent sexual and reproductive health in Sri Lanka
The complex nature of adolescent sexual and reproductive health (ASRH) determinants demands a multidisciplinary and intersectoral approach. Collaborative approaches are central to the delivery of quality health care and services but the focus is often health sector specific. Few research studies have explored the views and experiences of health workers and teachers and examined how ASRH services and information are provided by professionals across the education and health sector. Sri Lanka has made considerable progress towards addressing the Millennium Development Goals (MDG), however, there are still gaps reflected in adolescent health, social indicators, and the delivery of services. Enhancing the collective efforts of teachers and health professionals may help to improve the quality and use of services and ASRH knowledge. This study aimed to identify the experiences, needs, knowledge, attitudes and practices of primary healthcare and education professionals and the strategies that best support them to deliver sexual and reproductive health information, education, counseling and clinical services to Sri Lankan adolescents. Qualitative and survey data were gathered from 65 nurses, midwives, public health inspectors, medical officers, teachers, counselors and principals in the district of Kalutara. Knowledge, attitudes and service gaps were identified in relation to contraception and policy guiding practice. Participants highlighted concerns with confidence, roles and training that were said to affect student access to appropriate health services. ASRH Collaborative practices were noted across the sectors and strategies suggested for improvement. Findings suggest that inter-professional educa-tion and training may provide opportunities to enhance collaboration supported and guided by appropriate policy, supervision and job descriptions (i.e. roles and responsibilities)
Effects to Scalar Meson Decays of Strong Mixing between Low and High Mass Scalar Mesons
We analyze the mass spectroscopy of low and high mass scalar mesons and get
the result that the coupling strengths of the mixing between low and high mass
scalar mesons are very strong and the strengths of mixing for scalar
mesons and those of I=0 scalar mesons are almost same. Next, we analyze the
decay widths and decay ratios of these mesons and get the results that the
coupling constants for which represents the coupling of high
mass scalar meson -> two pseudoscalar mesons are almost same as the
coupling for the I=0. On the other hand, the coupling constant for
which represents the low mass scalar meson -> are far
from the coupling constant for I=0. We consider a resolution for this
discrepancy. Coupling constant for glueball -> is smaller than
the coupling . is .Comment: 15 pages, 6 figure
Exact correlation functions of the BCS model in the canonical ensemble
We evaluate correlation functions of the BCS model for finite number of
particles. The integrability of the Hamiltonian relates it with the Gaudin
algebra . Therefore, a theorem that Sklyanin proved for the
Gaudin model, can be applied. Several diagonal and off-diagonal correlators are
calculated. The finite size scaling behavior of the pairing correlation
function is studied.Comment: 4 pages revtex; 2 figures .eps. Revised version to be published in
Phys. Rev. Let
First detection of [N II] 205 micrometer absorption in interstellar gas
We present high resolution [NII] 205 micrometer ^3P_1-^3P_0 spectra obtained
with Herschel-HIFI towards a small sample of far-infrared bright star forming
regions in the Galactic plane: W31C (G10.6-0.4), W49N (G43.2-0.1), W51
(G49.5-0.4), and G34.3+0.1. All sources display an emission line profile
associated directly with the HII regions themselves. For the first time we also
detect absorption of the [NII] 205 micrometer line by extended low-density
foreground material towards W31C and W49N over a wide range of velocities. We
attribute this absorption to the warm ionised medium (WIM) and find
N(N^+)\approx 1.5x10^17 cm^-2 towards both sources. This is in agreement with
recent Herschel-HIFI observations of [CII] 158 micrometer, also observed in
absorption in the same sight-lines, if \approx7-10 % of all C^+ ions exist in
the WIM on average. Using an abundance ratio of [N]/[H] = 6.76x10^-5 in the gas
phase we find that the mean electron and proton volume densities are ~0.1-0.3
cm^-3 assuming a WIM volume filling fraction of 0.1-0.4 with a corresponding
line-of-sight filling fraction of 0.46-0.74. A low density and a high WIM
filling fraction are also supported by RADEX modelling of the [NII] 205
micrometer absorption and emission together with visible emission lines
attributed mainly to the WIM. The detection of the 205 micrometer line in
absorption emphasises the importance of a high spectral resolution, and also
offers a new tool for investigation of the WIM.Comment: 7 pages, 4 figures, accepted for publication in Astronomy &
Astrophysics, 11 June 201
- …