935 research outputs found
Database support of detector operation and data analysis in the DEAP-3600 Dark Matter experiment
The DEAP-3600 detector searches for dark matter interactions on a 3.3 tonne
liquid argon target. Over nearly a decade, from start of detector construction
through the end of the data analysis phase, well over 200 scientists will have
contributed to the project. The DEAP-3600 detector will amass in excess of 900
TB of data representing more than 10 particle interactions, a few of
which could be from dark matter. At the same time, metadata exceeding 80 GB
will be generated. This metadata is crucial for organizing and interpreting the
dark matter search data and contains both structured and unstructured
information.
The scale of the data collected, the important role of metadata in
interpreting it, the number of people involved, and the long lifetime of the
project necessitate an industrialized approach to metadata management.
We describe how the CouchDB and the PostgreSQL database systems were
integrated into the DEAP detector operation and analysis workflows. This
integration provides unified, distributed access to both structured
(PostgreSQL) and unstructured (CouchDB) metadata at runtime of the data
analysis software. It also supports operational and reporting requirements
Polyethylene naphthalate film as a wavelength shifter in liquid argon detectors
Liquid argon-based scintillation detectors are important for dark matter
searches and neutrino physics. Argon scintillation light is in the vacuum
ultraviolet region, making it hard to be detected by conventional means.
Polyethylene naphthalate (PEN), an optically transparent thermoplastic
polyester commercially available as large area sheets or rolls, is proposed as
an alternative wavelength shifter to the commonly-used tetraphenyl butadiene
(TPB). By combining the existing literature data and spectrometer measurements
relative to TPB, we conclude that the fluorescence yield and timing of both
materials may be very close. The evidence collected suggests that PEN is a
suitable replacement for TPB in liquid argon neutrino detectors, and is also a
promising candidate for dark matter detectors. Advantages of PEN are discussed
in the context of scaling-up existing technologies to the next generation of
very large ktonne-scale detectors. Its simplicity has a potential to facilitate
such scale-ups, revolutionizing the field.Comment: 6 pages, 3 figure
Empathic forecasting: How do we predict other people's feelings?
When making affective forecasts, people commit the impact bias. They overestimate the impact an emotional event has on their affective experience. In three studies we show that people also commit the impact bias when making empathic forecasts, affective forecasts for someone else. They overestimate the impact an emotional event has on someone else's affective experience (Study 1), they do so for friends and strangers (Study 2), and they do so when other sources of information are available (Study 3). Empathic forecasting accuracy, the correlation between one person's empathic forecast and another person's actual affective experience, was lower than between-person forecasting correspondence, the correlation between one person's empathic forecast and another person's affective forecast. Empathic forecasts do not capture other people's actual experience very well but are similar to what other people forecast for themselves. This may enhance understanding between people
Exact and simple results for the XYZ and strongly interacting fermion chains
We conjecture exact and simple formulas for physical quantities in two
quantum chains. A classic result of this type is Onsager, Kaufman and Yang's
formula for the spontaneous magnetization in the Ising model, subsequently
generalized to the chiral Potts models. We conjecture that analogous results
occur in the XYZ chain when the couplings obey J_xJ_y + J_yJ_z + J_x J_z=0, and
in a related fermion chain with strong interactions and supersymmetry. We find
exact formulas for the magnetization and gap in the former, and the staggered
density in the latter, by exploiting the fact that certain quantities are
independent of finite-size effects
Radon backgrounds in the DEAP-1 liquid-argon-based Dark Matter detector
The DEAP-1 \SI{7}{kg} single phase liquid argon scintillation detector was
operated underground at SNOLAB in order to test the techniques and measure the
backgrounds inherent to single phase detection, in support of the
\mbox{DEAP-3600} Dark Matter detector. Backgrounds in DEAP are controlled
through material selection, construction techniques, pulse shape discrimination
and event reconstruction. This report details the analysis of background events
observed in three iterations of the DEAP-1 detector, and the measures taken to
reduce them.
The Rn decay rate in the liquid argon was measured to be between 16
and \SI{26}{\micro\becquerel\per\kilogram}. We found that the background
spectrum near the region of interest for Dark Matter detection in the DEAP-1
detector can be described considering events from three sources: radon
daughters decaying on the surface of the active volume, the expected rate of
electromagnetic events misidentified as nuclear recoils due to inefficiencies
in the pulse shape discrimination, and leakage of events from outside the
fiducial volume due to imperfect position reconstruction. These backgrounds
statistically account for all observed events, and they will be strongly
reduced in the DEAP-3600 detector due to its higher light yield and simpler
geometry
Multi-epoch Near-Infrared Interferometry of the Spatially Resolved Disk Around the Be Star Zeta Tau
We present interferometric observations of the Be star Zeta Tau obtained
using the MIRC beam combiner at the CHARA Array. We resolved the disk during
four epochs in 2007-2009. We fit the data with a geometric model to
characterize the circumstellar disk as a skewed elliptical Gaussian and the
central Be star as a uniform disk. The visibilities reveal a nearly edge-on
disk with a FWHM major axis of ~ 1.8 mas in the H-band. The non-zero closure
phases indicate an asymmetry within the disk. Interestingly, when combining our
results with previously published interferometric observations of Zeta Tau, we
find a correlation between the position angle of the disk and the spectroscopic
V/R ratio, suggesting that the tilt of the disk is precessing. This work is
part of a multi-year monitoring campaign to investigate the development and
outward motion of asymmetric structures in the disks of Be stars.Comment: Accepted for publication in the Astronomical Journal. 27 pages, 7
Figure
In-situ characterization of the Hamamatsu R5912-HQE photomultiplier tubes used in the DEAP-3600 experiment
The Hamamatsu R5912-HQE photomultiplier-tube (PMT) is a novel high-quantum
efficiency PMT. It is currently used in the DEAP-3600 dark matter detector and
is of significant interest for future dark matter and neutrino experiments
where high signal yields are needed.
We report on the methods developed for in-situ characterization and
monitoring of DEAP's 255 R5912-HQE PMTs. This includes a detailed discussion of
typical measured single-photoelectron charge distributions, correlated noise
(afterpulsing), dark noise, double, and late pulsing characteristics. The
characterization is performed during the detector commissioning phase using
laser light injected through a light diffusing sphere and during normal
detector operation using LED light injected through optical fibres
Tensor network states and geometry
Tensor network states are used to approximate ground states of local
Hamiltonians on a lattice in D spatial dimensions. Different types of tensor
network states can be seen to generate different geometries. Matrix product
states (MPS) in D=1 dimensions, as well as projected entangled pair states
(PEPS) in D>1 dimensions, reproduce the D-dimensional physical geometry of the
lattice model; in contrast, the multi-scale entanglement renormalization ansatz
(MERA) generates a (D+1)-dimensional holographic geometry. Here we focus on
homogeneous tensor networks, where all the tensors in the network are copies of
the same tensor, and argue that certain structural properties of the resulting
many-body states are preconditioned by the geometry of the tensor network and
are therefore largely independent of the choice of variational parameters.
Indeed, the asymptotic decay of correlations in homogeneous MPS and MERA for
D=1 systems is seen to be determined by the structure of geodesics in the
physical and holographic geometries, respectively; whereas the asymptotic
scaling of entanglement entropy is seen to always obey a simple boundary law --
that is, again in the relevant geometry. This geometrical interpretation offers
a simple and unifying framework to understand the structural properties of, and
helps clarify the relation between, different tensor network states. In
addition, it has recently motivated the branching MERA, a generalization of the
MERA capable of reproducing violations of the entropic boundary law in D>1
dimensions.Comment: 18 pages, 18 figure
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