First Direct Detection Constraints on Planck-Scale Mass Dark Matter with Multiple-Scatter Signatures Using the DEAP-3600 Detector

Dark matter with Planck-scale mass (≃10^{19}  GeV/c^{2}) arises in well-motivated theories and could be produced by several cosmological mechanisms. A search for multiscatter signals from supermassive dark matter was performed with a blind analysis of data collected over a 813 d live time with DEAP-3600, a 3.3 t single-phase liquid argon-based detector at SNOLAB. No candidate signals were observed, leading to the first direct detection constraints on Planck-scale mass dark matter. Leading limits constrain dark matter masses between 8.3×10^{6} and 1.2×10^{19}  GeV/c^{2}, and ^{40}Ar-scattering cross sections between 1.0×10^{-23} and 2.4×10^{-18}  cm^{2}. These results are interpreted as constraints on composite dark matter models with two different nucleon-to-nuclear cross section scalings.

Pulse-shape discrimination against low-energy Ar-39 beta decays in liquid argon with 4.5 tonne-years of DEAP-3600 data

The DEAP-3600 detector searches for the scintillation signal from dark matter particles scattering on a 3.3 tonne liquid argon target. The largest background comes from 39 Ar beta decays and is suppressed using pulse-shape discrimination (PSD). We use two types of PSD estimator: the prompt-fraction, which considers the fraction of the scintillation signal in a narrow and a wide time window around the event peak, and the log-likelihood-ratio, which compares the observed photon arrival times to a signal and a background model. We furthermore use two algorithms to determine the number of photons detected at a given time: (1) simply dividing the charge of each PMT pulse by the mean single-photoelectron charge, and (2) a likelihood analysis that considers the probability to detect a certain number of photons at a given time, based on a model for the scintillation pulse shape and for afterpulsing in the light detectors. The prompt-fraction performs approximately as well as the log-likelihood-ratio PSD algorithm if the photon detection times are not biased by detector effects. We explain this result using a model for the information carried by scintillation photons as a function of the time when they are detected.

Measurement of the Permanent Electric Dipole Moment of the Neutron

We present the result of an experiment to measure the electric dipole moment (EDM) of the neutron at the Paul Scherrer Institute using Ramsey's method of separated oscillating magnetic fields with ultracold neutrons. Our measurement stands in the long history of EDM experiments probing physics violating time-reversal invariance. The salient features of this experiment were the use of a ^{199}Hg comagnetometer and an array of optically pumped cesium vapor magnetometers to cancel and correct for magnetic-field changes. The statistical analysis was performed on blinded datasets by two separate groups, while the estimation of systematic effects profited from an unprecedented knowledge of the magnetic field. The measured value of the neutron EDM is d_{n}=(0.0±1.1_{stat}±0.2_{sys})×10^{-26}  e.cm.

First Results from the DEAP-3600 Dark Matter Search with Argon at SNOLAB

This Letter reports the first results of a direct dark matter search with the DEAP-3600 single-phase liquid argon (LAr) detector. The experiment was performed 2 km underground at SNOLAB (Sudbury, Canada) utilizing a large target mass, with the LAr target contained in a spherical acrylic vessel of 3600 kg capacity. The LAr is viewed by an array of PMTs, which would register scintillation light produced by rare nuclear recoil signals induced by dark matter particle scattering. An analysis of 4.44 live days (fiducial exposure of 9.87 ton day) of data taken during the initial filling phase demonstrates the best electronic recoil rejection using pulse-shape discrimination in argon, with leakage <1.2×10^{-7} (90% C.L.) between 15 and 31  keV_{ee}. No candidate signal events are observed, which results in the leading limit on weakly interacting massive particle (WIMP)-nucleon spin-independent cross section on argon, <1.2×10^{-44}  cm^{2} for a 100  GeV/c^{2} WIMP mass (90% C.L.).

Test of Lorentz invariance with spin precession of ultracold neutrons

A clock comparison experiment, analyzing the ratio of spin precession frequencies of stored ultracold neutrons and 199Hg atoms, is reported. No daily variation of this ratio could be found, from which is set an upper limit on the Lorentz invariance violating cosmic anisotropy field b perpendicular < 2 x 10(-20) eV (95% C.L.). This is the first limit for the free neutron. This result is also interpreted as a direct limit on the gravitational dipole moment of the neutron |gn| < 0.3 eV/c2 m from a spin-dependent interaction with the Sun. Analyzing the gravitational interaction with the Earth, based on previous data, yields a more stringent limit |gn| < 3 x 10(-4) eV/c2 m.

Measurement of the transverse polarization of electrons emitted in free-neutron decay

Both components of the transverse polarization of electrons (sigmaT1, sigmaT2) emitted in the beta-decay of polarized, free neutrons have been measured. The T-odd, P-odd correlation coefficient quantifying sigmaT2, perpendicular to the neutron polarization and electron momentum, was found to be R=0.008+/-0.015+/-0.005. This value is consistent with time reversal invariance and significantly improves limits on the relative strength of imaginary scalar couplings in the weak interaction. The value obtained for the correlation coefficient associated with sigmaT1, N=0.056+/-0.011+/-0.005, agrees with the Standard Model expectation, providing an important sensitivity test of the experimental setup.

Cold neutron energy dependent production of ultracold neutrons in solid deuterium

A measurement of the production of ultracold neutrons from velocity-selected cold neutrons on gaseous and solid deuterium targets is reported. The expected energy dependence for two-particle collisions with well defined neutron and Maxwell-Boltzmann distributed molecular velocities is found for the gas target. The solid target data agree in shape with the phonon density-of-states curve and provide strong evidence for the phonon model including multiphonon excitations.

Direct experimental limit on neutron-mirror-neutron oscillations

In case a mirror world with a copy of our ordinary particle spectrum would exist, the neutron n and its degenerate partner, the mirror neutron n', could potentially mix and undergo nn' oscillations. The interaction of an ordinary magnetic field with the ordinary neutron would lift the degeneracy between the mirror partners, diminish the n' amplitude in the n wave function and, thus, suppress its observability. We report an experimental comparison of ultracold neutron storage in a trap with and without superimposed magnetic field. No influence of the magnetic field is found and, assuming negligible mirror magnetic fields, a limit on the oscillation time taunn' > 103 s (95% C.L.) is derived.

Measured total cross sections of slow neutrons scattered by solid deuterium and implications for ultracold neutron sources

The total scattering cross sections for slow neutrons with energies in the range 100 neV to 3 meV for solid ortho-2H2 at 18 and 5 K, frozen from the liquid, have been measured. The 18 K cross sections are found to be in excellent agreement with theoretical expectations and for ultracold neutrons dominated by thermal up scattering. At 5 K the total scattering cross sections are found to be dominated by the crystal defects originating in temperature induced stress but not deteriorated by temperature cycles between 5 and 10 K.

Investigation of Solid D 2 for UCN Sources

Solid deuterium (sD2) will be used for the production of ultra-cold neutrons (UCN) in a new generation of UCN sources. Scattering cross sections of UCN in sD2 determine the source yield but until now have not been investigated. We report first results from transmission and scattering experiments with cold, very cold and ultra-cold neutrons on sD2 along with light transmission and Raman scattering studies showing the influence of the sD2 crystal properties.

Search for Time Reversal Violating Effects: R-Correlation Measurement in Neutron Decay

An experiment aiming at the simultaneous determination of both transversal polarization components of electrons emitted in the decay of free neutrons begins data taking using the polarized cold neutron beam (FUNSPIN) from the Swiss Neutron Spallation Source (SINQ) at the Paul-Scherrer Institute, Villigen. A non-zero value of R due to the e(-) polarization component, which is perpendicular to the plane spanned by the spin of the decaying neutron and the electron momentum, would signal a violation of time reversal symmetry and thus physics beyond the Standard Model. Present status of the project and the results from analysis of the first data sample will be discussed.

Measured total cross sections of slow neutrons scattered by gaseous and liquid 2H(2)

The total scattering cross sections for slow neutrons with energies E in the range 300 neV to 3 meV for gaseous and liquid ortho-2H2 have been measured. The cross sections for 2H2 gas are found to be in excellent agreement with both the Hamermesh and Schwinger and the Young and Koppel models. For liquid 2H(2), we confirm the existing experimental data in the cold neutron range and the discrepancy with the gas models. We find a clear 1 / square root[E'] dependence at low energies for both states. A simple explanation for the liquid 2H2 cross section is offered.

[Efficacy and tolerance of trimetazidine, a metabolic antianginal, in combination with a hemodynamic antianginal in stable exertion angina. TRIMPOL I, a multicenter study]

OBJECTIVE

Assess the antianginal and anti-ischemic effect of trimetazidine in patients with stable exercise-induced angina insufficiently controlled with conventional antianginal drugs.

PATIENTS AND METHODS

The study population included patients with coronarographically documented stable exercise-induced angina and no other serious concomitant condition. For inclusion, patients had to have two comparably positive treadmill exercise tests. Conventional antiangina drugs (long-acting nitrate derivatives, beta-blockers or calcium antagonists) were continued as was any other therapy having no effect on the ECG ST segment. The patients were given a 4-week regimen of trimetazidine (20 mg t.i.d.) after the second positive treadmill test and final inclusion. At the end of this period, a final exercise test was performed. The study population included 700 patients (mean age 54 +/- 8.4 years, range 32-71 years, 615 men, 85 women) who completed the entire treatment protocol.

RESULTS

The main findings observed after 4 weeks of treatment with trimetazidine were: significant lengthening of the total duration of exercise (486.6 s versus 443.7 s, p < 0.01)), increase in total work (10.6 METS versus 9.4 METS, p < 0.01), significant lengthening of delay to 1 mm ST depression (389.9 s versus 337.8 s, p < 0.01) and of the delay to onset of angina (450.3 s versus 251.7 s, p < 0.01). The other results were a significant reduction in the number of daily episodes of angina (2.47 versus 3.66, p < 0.01) and a reduction in mean use of complementary trinitrine (1.8 versus 2.94, p < 0.01).

CONCLUSIONS

Four weeks of treatment with trimetazidine in combination with conventional antiangina drugs leads to a longer delay to development of 1 mm ST depression (ischemia threshold), significant lengthening of total duration of treadmill exercise, increased total work, and longer delay to angina theshold. Clinically, there was a reduction in the mean number of episodes of angina and a reduction in the use of trinitrine.

The antiischemic effects and tolerability of trimetazidine in coronary diabetic patients. A substudy from TRIMPOL-1

Diabetes mellitus, a disease with a wide prevalence, has major cardiovascular effects, being a risk factor for the development of ischemic heart disease and congestive heart failure. The aim of this open, multicenter study was to assess the antiischemic efficacy and tolerability of trimetazidine, a metabolic agent acting at the myocardial mitochondrial level, in diabetic patients with stable effort angina treated previously with a single conventional antianginal drug. Fifty diabetic patients (mean age 58 years) with proven coronary artery disease, stable effort angina for at least 3 months, and positive, comparable results of two initial treadmill exercise tests separated by a 1-week interval were included in the study. They continued their conventional antianginal monotherapy with a long-acting nitrate, beta-blocker, or calcium channel blocker. After stabilization, 4-week therapy with trimetazidine, three times daily, 20 mg was initiated in combination with previous treatment. The results showed a significant improvement in exercise tolerance (440.2 vs. 383.2 s; P < 0.01), time to 1-mm ST-segment depression (358.3 vs. 301.6 s; P < 0.01), time to onset of anginal pain (400.0 vs. 238.3 s; P < 0.01), and total work (9.39 vs. 8.67 metabolic equivalents, P < 0.01). Maximal ST-segment depression was attenuated compared with baseline (1.82 vs. 1.91 mm). Other findings included a significant decrease in the mean frequency of anginal episodes (3.06 vs. 4.79 per week; P < 0.01) and in mean nitrate consumption (2.29 vs. 4.2 doses/week). These results suggest that trimetazidine may be effective and is well tolerated as combination therapy for diabetic coronary artery disease patients uncontrolled with a single hemodynamic agent.