-
D. G. Phillips II,
E. Aguayo,
F. T. Avignone III,
H. O. Back,
A. S. Barabash,
M. Bergevin,
F. E. Bertrand,
M. Boswell,
V. Brudanin,
M. Busch, [......],
R. L. Varner,
K. Vetter,
K. Vorren,
J. F. Wilkerson,
B. A. Wolfe,
E. Yakushev,
A. R. Young,
C. -H. Yu,
V. Yumatov,
C. Zhang
[show abstract]
[hide abstract]
ABSTRACT: The observation of neutrinoless double-beta decay would resolve the Majorana
nature of the neutrino and could provide information on the absolute scale of
the neutrino mass. The initial phase of the Majorana experiment, known as the
Demonstrator, will house 40 kg of Ge in an ultra-low background shielded
environment at the 4850' level of the Sanford Underground Laboratory in Lead,
SD. The objective of the Demonstrator is to determine whether a future 1-tonne
experiment can achieve a background goal of one count per tonne-year in a
narrow region of interest around the 76Ge neutrinoless double-beta decay peak.
11/2011;
-
E. Aguayo,
J. E. Fast,
E. W. Hoppe,
M. E. Keillor,
J. D. Kephart,
R.T. Kouzes,
B. D. LaFerriere,
J. Merriman,
J. L. Orrell,
N. R. Overman, [......],
V. E. Guiseppe,
C Keller,
D. -M. Mei,
G. Perumpilly,
K. Thomas,
C Zhang,
A. L. Hallin,
K. J. Keeter,
L. Mizouni,
J. F. Wilkerson
[show abstract]
[hide abstract]
ABSTRACT: A brief review of the history and neutrino physics of double beta decay is
given. A description of the MAJORANA DEMONSTRATOR research and development
program including background reduction techniques is presented in some detail.
The application of point contact (PC) detectors to the experiment is discussed,
including the effectiveness of pulse shape analysis. The predicted sensitivity
of a PC detector array enriched to 86% in 76Ge is given.
09/2011;
-
The MAJORANA Collaboration,
E. Aguayo,
F. T. Avignone III,
H. O. Back,
A. S. Barabash,
M. Bergevin,
F. E. Bertrand,
M. Boswell,
V. Brudanin,
M. Busch, [......],
R. L. Varner,
K. Vetter,
K. Vorren,
J. F. Wilkerson,
B. A. Wolfe,
E. Yakushev,
A. R. Young,
C. -H. Yu,
V. Yumatov,
C. Zhang
[show abstract]
[hide abstract]
ABSTRACT: Neutrinoless double-beta decay experiments can potentially determine the
Majorana or Dirac nature of the neutrino, and aid in understanding the neutrino
absolute mass scale and hierarchy. Future 76Ge-based searches target a
half-life sensitivity of >10^27 y to explore the inverted neutrino mass
hierarchy. Reaching this sensitivity will require a background rate of <1 count
tonne^-1 y^-1 in a 4-keV-wide spectral region of interest surrounding the Q
value of the decay. We investigate the overburden required to reach this
background goal in a tonne-scale experiment with a compact (copper and lead)
shield based on Monte Carlo calculations of cosmic-ray background rates. We
find that, in light of the presently large uncertainties in these types of
calculations, a site with an underground depth >~5200 mwe is required for a
tonne-scale experiment with a compact shield similar to the planned 40-kg
MAJORANA DEMONSTRATOR. The required overburden is highly dependent on the
chosen shielding configuration and could be relaxed significantly if, for
example, a liquid cryogen and water shield, or an active neutron shield were
employed. Operation of the MAJORANA DEMONSTRATOR and GERDA detectors will serve
to reduce the uncertainties on cosmic-ray background rates and will impact the
choice of shielding style and location for a future tonne-scale experiment.
4/2013: The peer review process revealed that one of the veto rejection
factors (the factor-of-4 described on p12) needs to be better established. Our
reevaluation of this parameter to date has not yielded strong support for the
value stated in the manuscript, and we require further study to develop a solid
estimate. This further study will supersede the work described in this
manuscript, and may or may not lead to the same conclusion regarding the ~>5200
mwe requirement for future tonne-scale 76Ge neutrinoless double beta decay
experiments.
09/2011;
-
MAJORANA Collaboration,
A. G. Schubert,
E. Aguayo,
F. T. Avignone III,
H. O. Back,
A. S. Barabash,
M. Bergevin,
F. E. Bertrand,
M. Boswell,
V. Brudanin, [......],
R. L. Varner,
K. Vetter,
K. Vorren,
J. F. Wilkerson,
B. A. Wolfe,
E. Yakushev,
A. R. Young,
C. ?H. Yu,
V. Yumatov,
C. Zhan
[show abstract]
[hide abstract]
ABSTRACT: The observation of neutrinoless double-beta decay would determine whether the
neutrino is a Majorana particle and provide information on the absolute scale
of neutrino mass. The MAJORANA Collaboration is constructing the DEMONSTRATOR,
an array of germanium detectors, to search for neutrinoless double-beta decay
of 76-Ge. The DEMONSTRATOR will contain 40 kg of germanium; up to 30 kg will be
enriched to 86% in 76-Ge. The DEMONSTRATOR will be deployed deep underground in
an ultra-low-background shielded environment. Operation of the DEMONSTRATOR
aims to determine whether a future tonne-scale germanium experiment can achieve
a background goal of one count per tonne-year in a 4-keV region of interest
around the 76-Ge neutrinoless double-beta decay Q-value of 2039 keV.
09/2011;
-
SNO Collaboration,
B. Aharmim,
S N Ahmed,
A E Anthony,
N. Barros,
E W Beier,
A Bellerive,
B. Beltran,
M. Bergevin,
S D Biller, [......],
P. J. S. Watson,
J Wendland,
N West,
J. F. Wilkerson,
J R Wilson,
J.M. Wouters,
A. Wright,
M Yeh,
F Zhang,
K Zuber
[show abstract]
[hide abstract]
ABSTRACT: We report results from a combined analysis of solar neutrino data from all
phases of the Sudbury Neutrino Observatory. By exploiting particle
identification information obtained from the proportional counters installed
during the third phase, this analysis improved background rejection in that
phase of the experiment. The combined analysis resulted in a total flux of
active neutrino flavors from 8B decays in the Sun of (5.25 \pm
0.16(stat.)+0.11-0.13(syst.))\times10^6 cm^{-2}s^{-1}. A two-flavor neutrino
oscillation analysis yielded \Deltam^2_{21} = (5.6^{+1.9}_{-1.4})\times10^{-5}
eV^2 and tan^2{\theta}_{12}= 0.427^{+0.033}_{-0.029}. A three-flavor neutrino
oscillation analysis combining this result with results of all other solar
neutrino experiments and the KamLAND experiment yielded \Deltam^2_{21} =
(7.41^{+0.21}_{-0.19})\times10^{-5} eV^2, tan^2{\theta}_{12} =
0.446^{+0.030}_{-0.029}, and sin^2{\theta}_{13} =
(2.5^{+1.8}_{-1.5})\times10^{-2}. This implied an upper bound of
sin^2{\theta}_{13} < 0.053 at the 95% confidence level (C.L.).
09/2011;
-
B. Aharmim,
S N Ahmed,
J. F. Amsbaugh,
J. M. Anaya,
A E Anthony,
J. Banar,
N. Barros,
E W Beier,
A Bellerive,
B. Beltran, [......],
J Wendland,
N West,
J.B. Wilhelmy,
J. F. Wilkerson,
J R Wilson,
J.M. Wouters,
A. Wright,
M Yeh,
F Zhang,
K Zuber
[show abstract]
[hide abstract]
ABSTRACT: This paper details the solar neutrino analysis of the 385.17-day Phase-III
data set acquired by the Sudbury Neutrino Observatory (SNO). An array of $^3$He
proportional counters was installed in the heavy-water target to measure
precisely the rate of neutrino-deuteron neutral-current interactions. This
technique to determine the total active $^8$B solar neutrino flux was largely
independent of the methods employed in previous phases. The total flux of
active neutrinos was measured to be
$5.54^{+0.33}_{-0.31}(stat.)^{+0.36}_{-0.34}(syst.)\times 10^{6}$ cm$^{-2}$
s$^{-1}$, consistent with previous measurements and standard solar models. A
global analysis of solar and reactor neutrino mixing parameters yielded the
best-fit values of $\Delta m^2 = 7.59^{+0.19}_{-0.21}\times 10^{-5}{eV}^2$ and
$\theta = 34.4^{+1.3}_{-1.2}$ degrees.
07/2011;
-
B Beltran,
H Bichsel,
B Cai,
G A Cox,
H Deng,
J Detwiler,
J A Formaggio,
S Habib,
A L Hallin, A Hime, [......],
K Rielage,
R G H Robertson,
M W E Smith,
L C Stonehill,
N Tolich,
T Van Wechel,
H Wan Chan Tseung,
J Wendland,
J F Wilkerson,
A Wright
[show abstract]
[hide abstract]
ABSTRACT: The third phase of the Sudbury Neutrino Observatory (SNO) experiment added an array of 3He proportional counters to the detector. The purpose of this neutral-current detection (NCD) array was to observe neutrons resulting from neutral-current solar-neutrino–deuteron interactions. We have developed a detailed simulation of current pulses from NCD array proportional counters, from the primary neutron capture on 3He through NCD array signal-processing electronics. This NCD array MC simulation was used to model the alpha-decay background in SNO's third-phase 8B solar-neutrino measurement.
New Journal of Physics 07/2011; 13(7):073006. · 4.18 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A large number of current and future experiments in neutrino and dark matter
detection use the scintillation light from noble elements as a mechanism for
measuring energy deposition. The scintillation light from these elements is
produced in the extreme ultraviolet (EUV) range, from 60 - 200 nm. Currently,
the most practical technique for observing light at these wavelengths is to
surround the scintillation volume with a thin film of Tetraphenyl Butadiene
(TPB) to act as a fluor. The TPB film absorbs EUV photons and reemits visible
photons, detectable with a variety of commercial photosensors. Here we present
a measurement of the re-emission spectrum of TPB films when illuminated with
128, 160, 175, and 250 nm light. We also measure the fluorescence efficiency as
a function of incident wavelength from 120 to 250 nm.
04/2011;
-
B. Beltran,
H. Bichsel,
B. Cai,
H Deng,
J. A. Formaggio,
S. Habib,
A. L. Hallin, A. Hime,
M Huang,
C. Kraus, [......],
K. Rielage,
R. G. H. Robertson,
M W E Smith,
L. C. Stonehill,
N Tolich,
T. Van Wechel,
H. Wan Chan Tseung,
J Wendland,
J. F. Wilkerson,
A. Wright
[show abstract]
[hide abstract]
ABSTRACT: The third phase of the Sudbury Neutrino Observatory (SNO) experiment added an
array of 3He proportional counters to the detector. The purpose of this Neutral
Current Detection (NCD) array was to observe neutrons resulting from
neutral-current solar neutrino-deuteron interactions. We have developed a
detailed simulation of the current pulses from the NCD array proportional
counters, from the primary neutron capture on 3He through the NCD array
signal-processing electronics. This NCD array Monte Carlo simulation was used
to model the alpha-decay background in SNO's third-phase 8B solar-neutrino
measurement.
04/2011;
-
C E Aalseth,
E Aguayo,
M Amman,
F T Avignone,
Iii Cd,
H O Back,
X Bai,
A S Barabash,
P S Barbeau,
M Bergevin, [......],
K Vorren,
J F Wilkerson Pf D,
B A Wolfe,
W Xiang,
E Yakushev,
H Yaver,
A R Young,
C.-H Yu,
V Yumatov,
C Zhang
[show abstract]
[hide abstract]
ABSTRACT: The Majorana Collaboration is assembling an array of HPGe detectors to search for neutrinoless double-beta decay in 76Ge. Initially, Majorana aims to construct a prototype module to demonstrate the potential of a future 1-tonne experiment. The design and potential reach of this prototype Demonstrator module are presented.
Nuclear Physics B - Proceedings Supplements 01/2011; 217:44. · 0.88 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The next generation low-background detectors operating underground aim for
unprecedented low levels of radioactive backgrounds. Although the radioactive
decays of airborne radon (particularly Rn-222) and its subsequent progeny
present in an experiment are potential backgrounds, also problematic is the
deposition of radon progeny on detector materials. Exposure to radon at any
stage of assembly of an experiment can result in surface contamination by
progeny supported by the long half life (22 y) of Pb-210 on sensitive locations
of a detector. An understanding of the potential surface contamination from
deposition will enable requirements of radon-reduced air and clean room
environments for the assembly of low background experiments. It is known that
there are a number of environmental factors that govern the deposition of
progeny onto surfaces. However, existing models have not explored the impact of
some environmental factors important for low background experiments. A test
stand has been constructed to deposit radon progeny on various surfaces under a
controlled environment in order to develop a deposition model. Results from
this test stand and the resulting deposition model are presented.
12/2010;
-
MAJORANA Collaboration,
C. E. Aalseth,
M. Amman,
F. T. Avignone III,
H. O. Back,
A. S. Barabash,
P. S. Barbeau,
M. Bergevin,
F. E. Bertrand,
M. Boswell, [......],
J. F. Wilkerson,
B. A. Wolfe,
W Xiang,
E. Yakushev,
H. Yaver,
A. R. Young,
C. -H. Yu,
V. Yumatov,
C Zhang,
S. Zimmerman
[show abstract]
[hide abstract]
ABSTRACT: The MAJORANA Collaboration is building the MAJORANA DEMONSTRATOR, a 60 kg
array of high purity germanium detectors housed in an ultra-low background
shield at the Sanford Underground Laboratory in Lead, SD. The MAJORANA
DEMONSTRATOR will search for neutrinoless double-beta decay of 76Ge while
demonstrating the feasibility of a tonne-scale experiment. It may also carry
out a dark matter search in the 1-10 GeV/c^2 mass range. We have found that
customized Broad Energy Germanium (BEGe) detectors produced by Canberra have
several desirable features for a neutrinoless double-beta decay experiment,
including low electronic noise, excellent pulse shape analysis capabilities,
and simple fabrication. We have deployed a customized BEGe, the MAJORANA
Low-Background BEGe at Kimballton (MALBEK), in a low-background cryostat and
shield at the Kimballton Underground Research Facility in Virginia. This paper
will focus on the detector characteristics and measurements that can be
performed with such a radiation detector in a low-background environment.
07/2010;
-
B. Aharmim,
S. N. Ahmed,
A. E. Anthony,
N. Barros,
E. W. Beier,
A. Bellerive,
B. Beltran,
M. Bergevin,
S. D. Biller,
K. Boudjemline, [......],
H. Wan Chan Tseung,
D. L. Wark,
N. West,
J. F. Wilkerson,
J. R. Wilson,
J. M. Wouters,
A. Wright,
M. Yeh,
F. Zhang,
K. Zuber
[show abstract]
[hide abstract]
ABSTRACT: Results are reported from a joint analysis of Phase I and Phase II data from the Sudbury Neutrino Observatory. The effective electron kinetic energy threshold used is Teff=3.5 MeV, the lowest analysis threshold yet achieved with water Cherenkov detector data. In units of 106 cm-2 s-1, the total flux of active-flavor neutrinos from 8B decay in the Sun measured using the neutral current (NC) reaction of neutrinos on deuterons, with no constraint on the 8B neutrino energy spectrum, is found to be ΦNC=5.140-0.158+0.160(stat)-0.117+0.132(syst). These uncertainties are more than a factor of 2 smaller than previously published results. Also presented are the spectra of recoil electrons from the charged current reaction of neutrinos on deuterons and the elastic scattering of electrons. A fit to the Sudbury Neutrino Observatory data in which the free parameters directly describe the total 8B neutrino flux and the energy-dependent νe survival probability provides a measure of the total 8B neutrino flux Φ8B=5.046-0.152+0.159(stat)-0.123+0.107(syst). Combining these new results with results of all other solar experiments and the KamLAND reactor experiment yields best-fit values of the mixing parameters of θ12=34.06-0.84+1.16 degrees and Δm212=7.59-0.21+0.20×10-5 eV2. The global value of Φ8B is extracted to a precision of -2.95+2.38%. In a three-flavor analysis the best fit value of sin2θ13 is 2.00-1.63+2.09×10-2. This implies an upper bound of sin2θ13<0.057 (95% C.L.).
Phys. Rev. C. 05/2010; 81(5).
-
[show abstract]
[hide abstract]
ABSTRACT: The scintillation light yield of liquid argon from nuclear recoils relative
to electronic recoils has been measured as a function of recoil energy from 10
keVr up to 250 keVr. The scintillation efficiency, defined as the ratio of the
nuclear recoil scintillation response to the electronic recoil response, is
0.25 \pm 0.01 + 0.01(correlated) above 20 keVr.
04/2010;
-
Bulletin of the American Physical Society. 01/2010; 55.
-
Bulletin of the American Physical Society. 01/2010; 55.
-
[show abstract]
[hide abstract]
ABSTRACT: In this paper, we demonstrate the use of physical models to evaluate the production of $^{39}$Ar and $^{40}$Ar underground. Considering both cosmogenic $^{39}$Ar production and radiogenic $^{40}$Ar production in situ and from external sources, we can derive the ratio of $^{39}$Ar to $^{40}$Ar in underground sources. We show for the first time that the $^{39}$Ar production underground is dominated by stopping negative muon capture on $^{39}$K and ($\alpha,n)$ induced subsequent $^{39}$K(n,p)$^{39}$Ar reactions. The production of $^{39}$Ar is shown as a function of depth. We demonstrate that argon depleted in $^{39}$Ar can be obtained only if the depth of the underground resources is greater than 500 m.w.e. below the surface. Stopping negative muon capture on $^{39}$K dominates over radiogenic production at depths of less than 2000 m.w.e., and that production by muon-induced neutrons is subdominant at any depth. The depletion factor depends strongly on both radioactivity level and potassium content in the rock. We measure the radioactivity concentration and potassium concentration in the rock for a potential site of an underground argon source in South Dakota. Depending on the probability of $^{39}$Ar and $^{40}$Ar produced underground being dissolved in the water, the upper limit of the concentration of $^{39}$Ar in the underground water at this site is estimated to be in a range of a factor of 1.6 to 155 less than the $^{39}$Ar concentration in the atmosphere. The calculation tools presented in this paper are also critical to the dating method with $^{39}$Ar. Comment: 7 pages, 6 figures
12/2009;
-
C E Aalseth,
M Amman,
J F Amsbaugh,
F T Avignone Iii,
H O Back,
A S Barabash,
P S Barbeau,
J R Beene,
M Bergevin,
F E Bertrand, [......],
K Vetter,
R Warner,
J F Wilkerson,
J M Wouters,
E Yakushev,
A R Young,
C.-H Yu,
V Yumatov,
C Zhang,
S Zimmerman
J.L. Orrell. 11/2009; 101111161716(10).
-
B. Aharmim,
S. N. Ahmed,
T. C. Andersen,
A. E. Anthony,
N. Barros,
E. W. Beier,
A. Bellerive,
B. Beltran,
M. Bergevin,
S. D. Biller, [......],
P. Watson,
J. Wendland,
N. West,
J. F. Wilkerson,
J. R. Wilson,
J. M. Wouters,
A. Wright,
M. Yeh,
F. Zhang,
K. Zuber
[show abstract]
[hide abstract]
ABSTRACT: Results are reported on the measurement of the atmospheric neutrino-induced muon flux at a depth of 2 kilometers below the Earth’s surface from 1229 days of operation of the Sudbury Neutrino Observatory (SNO). By measuring the flux of through-going muons as a function of zenith angle, the SNO experiment can distinguish between the oscillated and unoscillated portion of the neutrino flux. A total of 514 muonlike events are measured between -1≤cosθzenith≤0.4 in a total exposure of 2.30×1014 cm2 s. The measured flux normalization is 1.22±0.09 times the Bartol three-dimensional flux prediction. This is the first measurement of the neutrino-induced flux where neutrino oscillations are minimized. The zenith distribution is consistent with previously measured atmospheric neutrino oscillation parameters. The cosmic ray muon flux at SNO with zenith angle cosθzenith>0.4 is measured to be (3.31±0.01(stat)±0.09(sys))×10-10 μ/s/cm2.
Phys. Rev. D. 07/2009; 80(1).
-
[show abstract]
[hide abstract]
ABSTRACT: Inelastic neutron scattering and reactions on Pb isotopes can result in gamma rays near the signature endpoint energy in a number of double-beta decay isotopes. In particular, there are gamma-ray transitions in Pb-206,207,208 that might produce energy deposits at the 76-Ge Q value in Ge detectors used for double-beta decay searches. The levels that produce these gamma rays can be excited by (n,n'gamma) or (n,xngamma) reactions, but the cross sections are small and previously unmeasured. This work uses the pulsed neutron beam at the Los Alamos Neutron Science Center to directly measure reactions of interest to double-beta decay experiments. The cross section on natural Pb to produce the 2041-keV gamma ray from Pb-206 is measured to be 3.6 +/- 0.7 (stat.) +/- 0.3 (syst.) mb at ~9.6 MeV. The cross section on natural Pb to produce the 3062-keV gamma ray from Pb-207 and Pb-208 is measured to be 3.9 +/- 0.8 (stat.) +/- 0.4 (syst.) mb at the same energy. We report cross sections or place upper limits on the cross sections for exciting some other levels in Pb that have transition energies corresponding to Q value in other double-beta decay isotopes. Comment: 6 pages, 3 figures. v2 resubmitted to Phys. Rev. C with minor changes. v3 with final review changes
Physical Review C 05/2009; 79(5):054604. · 3.31 Impact Factor
