This Letter reports the results from a haloscope search for dark matter axions with masses between 2.66 and 2.81 μeV. The search excludes the range of axion-photon couplings predicted by plausible ...models of the invisible axion. This unprecedented sensitivity is achieved by operating a large-volume haloscope at subkelvin temperatures, thereby reducing thermal noise as well as the excess noise from the ultralow-noise superconducting quantum interference device amplifier used for the signal power readout. Ongoing searches will provide nearly definitive tests of the invisible axion model over a wide range of axion masses.
The μeV axion is a well-motivated extension to the standard model. The Axion Dark Matter eXperiment (ADMX) collaboration seeks to discover this particle by looking for the resonant conversion of ...dark-matter axions to microwave photons in a strong magnetic field. In this Letter, we report results from a pathfinder experiment, the ADMX "Sidecar," which is designed to pave the way for future, higher mass, searches. This testbed experiment lives inside of and operates in tandem with the main ADMX experiment. The Sidecar experiment excludes masses in three widely spaced frequency ranges (4202-4249, 5086-5799, and 7173-7203 MHz). In addition, Sidecar demonstrates the successful use of a piezoelectric actuator for cavity tuning. Finally, this publication is the first to report data measured using both the TM_{010} and TM_{020} modes.
A direct dark matter search is performed using fully-depleted high-resistivity CCD detectors. Due to their low electronic readout noise (R.M.S. ∼7 eV) these devices operate with a very low detection ...threshold of 40 eV, making the search for dark matter particles with low masses (∼5 GeV) possible. The results of an engineering run performed in a shallow underground site are presented, demonstrating the potential of this technology in the low mass region.
Spin-Dependent WIMP Limits from a Bubble Chamber Behnke, E; Collar, J.I; Cooper, P.S ...
Science (American Association for the Advancement of Science),
02/2008, Letnik:
319, Številka:
5865
Journal Article
Recenzirano
Odprti dostop
Bubble chambers were the dominant technology used for particle detection in accelerator experiments for several decades, eventually falling into disuse with the advent of other techniques. We report ...here on a new application for these devices. We operated an ultraclean, room-temperature bubble chamber containing 1.5 kilograms of superheated CF₃I, a target maximally sensitive to spin-dependent and -independent weakly interacting massive particle (WIMP) couplings. An extreme intrinsic insensitivity to the backgrounds that commonly limit direct searches for dark matter was measured in this device under operating conditions leading to the detection of low-energy nuclear recoils like those expected from WIMPs. Improved limits on the spin-dependent WIMP-proton scattering cross section were extracted during our experiments, excluding this type of coupling as a possible explanation for a recent claim of particle dark-matter detection.
Data from the operation of a bubble chamber filled with 3.5 kg of CF3I in a shallow underground site are reported. An analysis of ultrasound signals accompanying bubble nucleations confirms that ...alpha decays generate a significantly louder acoustic emission than single nuclear recoils, leading to an efficient background discrimination. Three dark matter candidate events were observed during an effective exposure of 28.1 kg day, consistent with a neutron background. This observation provides strong direct detection constraints on weakly interacting massive particle (WIMP)-proton spin-dependent scattering for WIMP masses >20 GeV/c2.
Objectives
To assess the associations of folate, homocysteine and vitamin B12 levels of children at birth and their methylenetetrahydrofolate reductase (MTHFR) variants with asthma and eczema in ...childhood.
Methods
This study was embedded in a population‐based prospective cohort study (n = 2,001). Neonatal cord blood folate, homocysteine and vitamin B12 levels were measured, and MTHFR C677T and A1298C genotyped. Wheezing and physician‐diagnosed eczema were annually obtained by questionnaire until 4 years. At 6 years, we collected information on physician‐diagnosed asthma ever and self‐reported eczema ever, measured fractional exhaled nitric oxide (FeNO), and interrupter resistance (Rint). Data were analysed with generalized estimating equations or logistic regression: continuous outcomes with linear regression models.
Results
Folate, homocysteine and vitamin B12 levels of children at birth were not associated with wheezing or eczema until 4 years, asthma and eczema ever, or FeNO or Rint at 6 years. In children carrying C677T mutations in MTHFR, higher folate levels were associated with an increased risk of eczema (repeated eczema until 4 years: OR 1.40 (95% CI 1.09–1.80) (SD change) P‐interaction = 0.003, eczema ever at 6 years: OR 1.41 (0.97–2.03) P‐interaction = 0.011). No interactions between MTHFR and child folate and homocysteine levels were observed for wheezing and asthma.
Conclusions
Folate, homocysteine and vitamin B12 levels of children at birth did not affect asthma‐ and eczema‐related outcomes up to the age of 6 years. Further studies are warranted to establish the role of MTHFR variants in these associations.
The BGOOD experiment at ELSA Jude, TC; Beck, R; Braghieri, A ...
Journal of physics. Conference series,
09/2023, Letnik:
2586, Številka:
1
Journal Article
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Abstract
The BGOOD photoproduction experiment accesses forward meson angles and low momentum exchange kinematics in the
uds
sector, which may be sensitive to molecular-like hadron structure. Recent ...results are presented, including strangeness photoproduction at forward meson angles, and π
0
π
0
coherent photoproduction off the deuteron.
Bubble chambers for experiments in nuclear astrophysics DiGiovine, B.; Henderson, D.; Holt, R.J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2015, Letnik:
781, Številka:
C
Journal Article
Recenzirano
Odprti dostop
A bubble chamber has been developed to be used as an active target system for low energy nuclear astrophysics experiments. Adopting ideas from dark matter detection with superheated liquids, a ...detector system compatible with γ-ray beams has been developed. This detector alleviates some of the limitations encountered in standard measurements of the minute cross-sections of interest to stellar environments. While the astrophysically relevant nuclear reaction processes at hydrostatic burning temperatures are dominated by radiative captures, in this experimental scheme we measure the time-reversed processes. Such photodisintegrations allow us to compute the radiative capture cross-sections when transitions to excited states of the reaction products are negligible. Due to the transformation of phase space, the photodisintegration cross-sections are up to two orders of magnitude higher. The main advantage of the new target-detector system is a density several orders of magnitude higher than conventional gas targets. Also, the detector is virtually insensitive to the γ-ray beam itself, thus allowing us to detect only the products of the nuclear reaction of interest. The development and the operation as well as the advantages and disadvantages of the bubble chamber are discussed.
Summary
Background
Helicobacter pylori prevalence in Western countries has been declining simultaneously with increases in childhood asthma and allergic diseases; prior studies have linked these ...phenomena.
Aims
To examine the association between H. pylori colonisation in children and risk of asthma and related conditions at school age. We secondly examined additional effects of maternal H. pylori status by pairing with children's status.
Methods
This study was embedded in a multi‐ethnic population‐based cohort in Rotterdam, The Netherlands. We measured anti‐H. pylori and anti‐CagA antibodies in serum of children obtained at age 6 years, and of their mothers obtained during midpregnancy. Asthma or related conditions were reported for children at age 6 years. We used multivariate logistic regression analyses among 3797 subjects.
Results
In children, the H. pylori positivity rate was 8.7%, and 29.2% of these were CagA‐positive. A child's colonisation with a CagA‐negative‐H. pylori strain was associated with an increased risk of asthma (Odds ratio 2.11; 95% CI 1.23–3.60), but this differed for European (3.64; 1.97–6.73) and non‐European (0.52; 0.14–1.89) children. When taking into account maternal H. pylori status, only H. pylori‐positive children with an H. pylori‐negative mother had increased risk of asthma (2.42; 1.11–5.27), accounting for 3.4% of the asthma risk.
Conclusions
Colonisation of a European child with a CagA‐negative‐H. pylori strain at age 6 was associated with an increased prevalence of asthma, but there was no association for non‐European children. The underlying mechanisms for the observed risk differences require further research.
Maternal fish consumption during pregnancy might influence the fetal immune system through anti-inflammatory effects of omega-3 fatty acids, and might affect the risks of childhood asthma and atopy. ...In Generation R, a prospective cohort study in the Netherlands, we examined the associations of first trimester fish consumption with childhood wheezing and eczema in the first 4 years of life.
In total, 2976 mothers completed a 293-item semiquantitative food frequency questionnaire covering dietary intake in the first trimester. The occurrence of wheezing and eczema was yearly assessed by questionnaires.
Median weekly fish consumption was 83 (95% range 0-316) grams per week. We observed no consistent associations of maternal total-, lean- or fatty-fish consumption during pregnancy with the risks of childhood wheezing. Maternal shellfish consumption of 1-13 g per week was associated with overall increased risks of childhood wheezing and eczema (OR 1.20 (1.04, 1.40) and OR 1.18 (1.01, 1.37), respectively). Maternal fatty fish consumption of 35-69 g per week was associated with increased overall risks of childhood eczema (OR 1.17 (1.00, 1.38)), but maternal total- or lean-fish consumption was not.
During pregnancy, shellfish consumption was associated with increased risks of wheezing and eczema, while fatty fish consumption was associated with a higher risk of eczema only. Maternal total fish or lean fish consumption were not associated with wheezing or eczema. Further studies are needed to replicate these findings and to explore underlying mechanisms.
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