A Geant4 Simulation of the COUPP Bubble Chamber. CHARLES
CAPPS (Carnegie Mellon University, Pittsburgh, PA, 15289)
ANDREW SONNENSCHEIN (Fermi National Accelerator Laboratory, Batavia, IL, 60510)
It is known that
a sensitivity on the order of 1 event per year per ton of detector
material is necessary to detect a WIMP (Weakly Interacting Massive
Particle) dark matter candidate. After successful veto of cosmic
radiation, the neutron background will become the greatest obstacle
for COUPP (Chicagoland Observatory for Underground Particle Physics)
to achieve this level of sensitivity. Thus, understanding the COUPP
bubble chamber's response to low-energy neutrons (< 50 MeV)
is crucial. A Geant4 simulation of the COUPP bubble chamber response
to an Am/Be neutron source is described. The recoil energy spectra
given by the simulation are presented. Simulation results of event
rate as a function of chamber pressure are compared to experimental
data. Moreover, multiple bubble events--indicative of neutrons--are
examined. The ratio of single to multiple bubble events is determined
for different energy thresholds. To verify Geant4 for neutrons
in this energy regime, cross-sections and differential cross-sections
are computed from the simulation and compared to the JENDL, JEFF,
and ENDF nuclear databases. Elements present in the COUPP experiment
are considered. Good agreement is found between simulation cross-sections
and the above nuclear databases.
A Preliminary CCD Cosmetic Grading System for the Dark Energy Survey Camera
Focal Plane CCDs. SARAH CARLSON (DePauw University, Greencastle, IN,
46135) JUAN ESTRADA (Fermi National Accelerator Laboratory, Batavia,
IL, 60510)
The Dark Energy
Survey (DES) is a 5000 sq-degrees sky survey that will strive to
make more precise measurements of dark energy. The DES team at
Fermilab is responsible for the construction of the Dark Energy
Camera (DECam) that will be mounted along with corrective optics
and electronics on the Blanco 4-meter telescope at the Cerro Tololo
Inter-American Observatory (CTIO) in Chile. The camera will be
comprised of 62 image charge-coupled devices (CCDs) and 8 guiding,
focusing and aligning CCDs. These CCDs are made of silicon and
manufactured at Lawrence-Berkley National Laboratory (LBNL). Part
of the task of building the DECam is understanding how each CCD
functions. This understanding includes knowing the limitations
of each CCD. Cosmetic defects can be crippling to the performance
of a CCD. Cosmetic defects include white and dark pixels, bad columns,
as well as defects caused by dark current and quantum efficiency
(QE) non-uniformity problems. Dark current is a small electric
current generated by the thermal motion of the silicon atoms in
the CCD. QE is the measure of the CCD’s sensitivity to a certain
wavelength. Using the popular astronomical source detection program
Source Extractor we make two separate analyses: a flat-fielding
analysis and a uniformity analysis which includes both the dark
current and QE uniformity. Catalogs of all the defects found are
created for each analysis and analyzed. To be an acceptable candidate
for the DECam focal plane, each CCD must meet the requirement of
no more than 5% non-usable image area. Using this requirement as
a starting point, we have devised a preliminary cosmetic grading
system to be used for each CCD. Each CCD will be given two grades,
one for the flat-fielding analysis and one for the uniformity analysis.
The CCD will receive a grade of 0 if the affected area is 2.5%
or less of the total CCD area. A grade of 1 will be given if the
affected area is between 2.5% and 5% of the total CCD area. A grade
of 2 will be given if the affected area is 5% or more of the total
CCD area. Our logic for giving each CCD two grades instead of one
overall grade is that we will be able to better characterize CCDs,
and if the occasion should arise that we need to pick between groups
of CCDs for the DECam focal plane the two grades will assist us
in making our choice.
Analysis of Creep in Polyvinyl Chloride for the NOvA Detector. CHRISTINE
MIDDLETON (Wesleyan University, Middletown, CT,
6459) HANS JOSTLEIN (Fermi National Accelerator Laboratory, Batavia, IL, 60510)
This analysis
is an attempt to predict creep in the NOvA
detector, a proposed electron neutrino detector for the NuMI beamline
at Fermilab. The NOvA
detector is constructed of large PVC extrusions which contain 25
ktons of scintillating oil. Due to the scale of this detector and
the proposed experiment length of 20 years, creep in the structural
PVC of the detector is a concern. Creep data was taken on 18 samples
over 188 days. Stress levels ranged from 500 PSI to 2100 PSI, with
2 samples being tested at each stress. A variety of models and
fit functions from the literature were used, however a best fit
function was not readily apparent. Although the data could be fit
reasonably well, these functions were unable to give a reasonable
prediction for the creep after 20 years. In order to improve these
results, more data is needed which represents the secondary and
tertiary creep stages. We anticipate being able to study this behavior
using accelerated high temperature creep tests.
Analysis of the Habitat of Henslow's Sparrows Compared to Randomly Chosen
Grassland Areas. ANITA
NUNEZ (University of Illinois, Chicago, Il, 60607) ROD WALTON (Fermi National Accelerator Laboratory, Batavia, IL, 60510)
The Henslow’s
Sparrow is state endangered and is at risk of extinction as a breeding
species in Illinois. The population of this species has been decreasing
due to the degradation and loss of grassland habitat. This is the
second year of an ongoing study of the Henslow’s habitat. It is
important to study the vegetation of the Henslow’s Sparrow’s habitat
in order to assess whether the land management plans at Fermilab
are effective. Once the Henslow’s were located, the vegetation
comprising the birds’ habitats was studied. Measurements of the
maximum plant height, average plant height, and duff height were
taken as well as ground coverage measurements (percents of grasses,
forbs, duff and bare ground). For a control, randomly chosen grassland
sites were located within Fermilab property. t-tests and two-sample variance tests were used to analyze the
plant and duff height data, and Mann-Whitney Utests were used to analyze the ground cover data. The data suggested
Henslow’s Sparrows prefer areas with shorter maximum plant height
than was found in the randomly chosen sites. Further, the data
suggested these grassland birds prefer more duff and less bare
ground when compared to randomly chosen sites. The two-sample variance
tests showed there is lower variation in the maximum plant height
at sites Henslow’s prefer. This study’s findings are in agreement
with the previous study, which found Henslow’s Sparrows prefer
less bare ground as well as lower variance in the maximum plant
height. The previous study also suggested that Henslow’s prefer
more grasses in their areas when compared to randomly chosen sites.
For further research, this study should be repeated to further
support the findings. It would also be interesting to study how
large the Henslow’s territories are.
Characterizing the Charge Collection of the 0.13 µm IBMPIX Prototype Pixel
Detector. ANJALI TRIPATHI (Massachusetts Institute of Technology, Cambridge, MA, 2139) RONALD LIPTON (Fermi National Accelerator Laboratory, Batavia, IL, 60510)
Central to collider
physics experiments are silicon detectors, which track the trajectory
of particles produced during collisions. With the drive for ever
more precise resolution in particle tracking, a prototype pixel
detector (IBMPIX) manufactured by IBM in a 0.13 µm RF CMOS process,
was investigated to understand its charge collection and individual
pixel behavior. As a Monolithic Active Pixel Sensor, it was comprised
of arrays of pixels (10µm by 150µm) divided into three diode types
- a standard N-well, a deep (or triple) N-well, and a control without
a diode. To measure the pixel to pixel variations from the readout
electronics, a signal generator pulsed charge directly into the
analog circuitry, bypassing the diodes, at different threshold
settings. Upon characterizing the response of the readout electronics
for each pixel, a pulsed 1.06 µm Nd:YAG laser was used to determine
the relationship between the input charge and the output pulse
width. This pulse width was the amount of time that the input charge
was above a set threshold. With the data from both the laser and
the signal generator, a mathematical model was made for charge
diffusion across the chip. From the signal generator tests, the
readout electronics showed significant pixel to pixel variation.
This variation was nearly proportional to the threshold current
setting. Additionally, testing of the diodes yielded a precise
equation relating pulse-width to charge. For an idealized laser
beam of zero width, a diffusion length of approximately 80 microns
was determined. The source of the pixel to pixel variation can
be attributed to gain variations due to the fabrication. Further
studies should employ a laser with a spot size contained within
one pixel, include a diffusion model incorporating variable beam
width, and use an additional current source to set the threshold
value.
Comparison of the Populations of Common Wood-Nymph Butterflies in Burned Prairie,
Unburned Prairie, and Old Field Grasses. MARLENE
HAHN (Loyola University, Chicago, IL, 60626) ROD WALTON (Fermi National Accelerator Laboratory, Batavia, IL, 60510)
Common wood-nymph
butterflies are found throughout the United States and Canada.
However, not much is known about how they overwinter or their preferences
for particular grasses and habitats. In this study, the impact
of prairie management plans on the abundance of the wood-nymph
population was assessed as well as the preference of these butterflies
to areas with native or non-native grasses. The abundance of common
wood-nymph butterflies was determined using Pollard walks. The
majority of the vegetation at each of the three sites was identified
and documented. Using a 1 X 3 ANOVA, it was determined that there
was a significant difference (p < 0.0005)
between the abundance of common wood-nymphs in the European grasses
site compared to the burned and unburned prairie sites. There was
no significant difference between the burned and unburned treatments
of the prairie on the common wood-nymph population. A multiple
variable linear regression generated a model in which the temperature
and weather affected the observed common wood-nymph butterflies
per hour (p =
0.026). To verify these preliminary results, future studies need
to repeat this experiment. Quadrat analysis of the vegetation from
all three sites should be done in order to see if there is a correlation
between common wood-nymph butterfly abundance per hour and the
specific types or quantity of vegetation at each site. Another
area of investigation is to determine how the observer’s visual
field is affected by the density or height of vegetation at each
site.
Noise Performance of Next-Generation Electronics for the SuperCDMS 25kg Experiment. PETER BROOKS (Stanford University, Stanford, CA, 94305) FRITZ DEJONGH (Fermi National Accelerator Laboratory, Batavia, IL, 60510)
The Cryogenic
Dark Matter Search (CDMS) is a direct detection experiment looking
for signatures of elastic scattering between dark matter and atomic
nuclei in high purity, cryogenic silicon and germanium crystals.
In order to discover rare dark matter events against an overwhelming
background of natural radioactive decay processes, the experiment
relies on high-precision measurements of ionization and phonon
signals from these interactions. To increase the sensitivity of
the detector, it will be necessary to scale the size of the experiment
beyond the current 5.85 kg of detector mass. In order to scale
the necessary electronics to the 25kg scale for the proposed SuperCDMS
experiment, a prototype electronics board has been developed, which
condenses all of the current electronics system onto a single circuit
board by digitizing the signal as soon as possible and analyzing
offline in software. Statistical and Fourier analysis have been
performed on the prototype board, both without signals and with
test signals mimicking the actual detector signal, in a number
of operating modes for the board. These analyses show that the
noise performance of the prototype board is comparable to that
of the current system, and it is believed that with further refinement
the noise could be improved to offer better precision than the
current CDMS electronics. This development is an important step
in demonstrating the feasibility of a 25kg SuperCDMS experiment.
Sensitivity Study of the Relative Fraction of top/anti-top events Produced
via Gluon-fusion. KELLY GREENLAND (Lock Haven University of Pennsylvania, Lock Haven, PA, 17745) DR. RICARDO EUSEBI (Fermi National Accelerator Laboratory, Batavia, IL, 60510)
In high-energy
experimental particle physics, a primary goal is to study particles
that the scientists create, and by studying those particles physicists
results aid in confirming the validity of the standard model of
particles. To date, the standard model is the best representative
model of basic particles, and confirming the model helps to reassure
physicists the model is indeed on the right path. At the Fermi
National Accelerator Laboratory a circular particle accelerator,
called the Tevatron, accelerates protons and anti-protons to approximately
0.999 times the speed of light before colliding with each other.
The proton's constituents, gluons and quarks, may interact with
enough energy to create particles not initially present. If a quark
and anti-quark interact they will annihilate and may produce a
top/anti-top quark pair. Also, a gluon may fuse with another gluon
to produce a top/anti-top pair. This study focuses on finding the
accuracy with which scientists can measure the ratio of top/anti-top
pairs created by quark/anti-quark annihilation to that created
by gluon-fusion. The degree of accuracy of measuring the relative
fractions was determined via computer simulation. Initially gluon-fusion
and quark-annihilation top/anti-top events were generated by Monte-Carlo
simulations. Next, matrix element probabilities were determined
for each event. Using these probabilities, a set of templates were
created. Finally, in preparation to analyze the data, a likelihood
was constructed based on the templates. The likelihood was never
run on data, but only on Monte-Carlo simulations to obtain the
degree of accuracy, or sensitivity, that this method can provide.
Past studies claim an accuracy measurement of 22%. This study shows
a strong improvement of the ratio to approximately 15%. While this
is clearly an improvement, the expected degree of accuracy cannot
yet ensure that the ratios predicted by the standard model, regarding
production top/anti-top events, are indeed correct.
Simulation of Radioactive Ions for the Tevatron. JOSEPH
BOUIE III (Southern University, Baton Rouge, LA, 70813)
TERRENCE REESE (Fermi National Accelerator Laboratory, Batavia, IL, 60510)
To generate a
very pure and intense neutrino beam for Neutrino Physics experiments,
it has been proposed to use the beta-decay of radioactive ions
stored in a high energy decay ring. The original proposal was to
use parts of the existing CERN infrastructure, namely the Proton
Synchrotron (PS) and the Super Proton Synchrotron (SPS), to accelerate
the ions to 100GeV, but recent work has shown that it would be
advantageous to go to even higher energies. The Tevatron, located
at Fermi National Accelerated Laboratory, will be retired from
Collider Physics in a few years, and could be used for this purpose.
However, the decay products from the ions will present a significant
heat load to the superconducting magnets, which will limit the
number of ions that can be accelerated. To understand where the
limit is, a simulation of heat deposition from the decay products
is needed.
Software for The Perfect PID. KURTIS
GEERLINGS (Michigan State University, East Lansing, MI, 48825)
HOLGER MEYER (Fermi National Accelerator Laboratory, Batavia, IL, 60510)
The Main Injector
Particle Production Experiment (MIPP, FNAL E-907) promises to shed
light on many aspects of the particle physics world, from proton
radiography to nuclear physics and from neutrino flux measurements
to non-perturbative QCD. MIPP uses several detectors in order to
obtain nearly 100 percent acceptance for charged particles over
a vast momentum range, yielding nearly perfect particle identification.
The detectors include two beam cerenkovs, a time projection chamber
(TPC), a threshold cerenkov, a ring imaging cerenkov (RICH), a
time-of-flight system and an electromagnetic/hadronic calorimeter.
While the detectors are very important, without software to analyze
the data, no physics can be discovered. The MIPP software, written
mainly in C++, includes packages to reconstruct tracks of charged
particles in the TPC and packages to fit rings to the cerenkov
radiation in the RICH. Equally important is the monte carlo package,
which allows one to compare simulations with data. To most effectively
test the analysis software with the simulation, the monte carlo
must output its data in the same format as the experimental data.
This process is often called digitization. In the case of the threshold
cerenkov, it represents converting exact timing information from
the simulation into a time to digital converter (TDC) signal, and
the number of photoelectrons detected into an analog to digital
converter (ADC) signal. This way, the monte carlo information resembles
the data coming from detectors. Another important aspect to consider
is testing and debugging of existing code. Since many people have
contributed to the MIPP software, it is important to debug and
test code written by other people. This helps to ensure that the
software does what it is supposed to, and results are not based
on false analysis.
