Final Results from phase II of the Mainz Neutrino Mass Search in Tritium β\beta Decay

The paper reports on the improved Mainz experiment on tritum $\beta$ spectroscopy which yields a 10 times' higher signal to background ratio than before. The main experimental effects and systematic uncertainties have been investigated in side experiments and possible error sources have been eliminated. Extensive data taking took place in the years 1997 to 2001. A residual analysis of the data sets yields for the square of the electron antineutrino mass the final result of $m^2(\nu_e)=(-0.6 \pm 2.2_{\rm{stat}} \pm 2.1_{\rm{syst}})$ eV$^2$/c$^4$. We derive an upper limit of $m(\nu_e)\leq 2.3$ eV/c$^2$ at 95% confidence level for the mass itself.Comment: 22 pages, 22 figures submitted to EPJ

Monitoring of tritium purity during long-term circulation in the KATRIN test experiment LOOPINO using laser Raman spectroscopy

The gas circulation loop LOOPINO has been set up and commissioned at Tritium Laboratory Karlsruhe (TLK) to perform Raman measurements of circulating tritium mixtures under conditions similar to the inner loop system of the neutrino-mass experiment KATRIN, which is currently under construction. A custom-made interface is used to connect the tritium containing measurement cell, located inside a glove box, with the Raman setup standing on the outside. A tritium sample (purity > 95%, 20 kPa total pressure) was circulated in LOOPINO for more than three weeks with a total throughput of 770 g of tritium. Compositional changes in the sample and the formation of tritiated and deuterated methanes CT_(4-n)X_n (X=H,D; n=0,1) were observed. Both effects are caused by hydrogen isotope exchange reactions and gas-wall interactions, due to tritium {\beta} decay. A precision of 0.1% was achieved for the monitoring of the T_2 Q_1-branch, which fulfills the requirements for the KATRIN experiment and demonstrates the feasibility of high-precision Raman measurements with tritium inside a glove box

Accurate reference gas mixtures containing tritiated molecules: Their production and raman‐based analysis

Highly accurate, quantitative analyses of mixtures of hydrogen isotopologues—both the stable species, H$_{2}$, D$_{2}$2, and HD, and the radioactive species, T$_{2}$, HT, and DT—are of great importance in fields as diverse as deuterium–tritium fusion, neutrino mass measurements using tritium β-decay, or for photonuclear experiments in which hydrogen–deuterium targets are used. In this publication we describe a production, handling, and analysis facility capable of fabricating well-defined gas samples, which may contain any of the stable and radioactive hydrogen isotopologues, with sub-percent accuracy for the relative species concentrations. The production is based on precise manometric gas mixing of H$_{2}$, D$_{2}$, and T$_{2}$. The heteronuclear isotopologues HD, HT, and DT are generated via controlled, in-line catalytic reaction or by β-induced self-equilibration, respectively. The analysis was carried out using an in-line intensity- and wavelength-calibrated Raman spectroscopy system. This allows for continuous monitoring of the composition of the circulating gas during the self-equilibration or catalytic evolution phases. During all procedures, effects, such as exchange reactions with wall materials, were considered with care. Together with measurement statistics, these and other systematic effects were included in the determination of composition uncertainties of the generated reference gas samples. Measurement and calibration accuracy at the level of 1% was achieved

Neutral tritium gas reduction in the KATRIN differential pumping sections

The KArlsruhe TRItium Neutrino experiment (KATRIN) aims to measure the effective electron anti-neutrino mass with an unprecedented sensitivity of $0.2\,\mathrm{eV}/\mathrm{c}^2$, using $\beta$-electrons from tritium decay. The electrons are guided magnetically by a system of superconducting magnets through a vacuum beamline from the windowless gaseous tritium source through differential and cryogenic pumping sections to a high resolution spectrometer and a segmented silicon pin detector. At the same time tritium gas has to be prevented from entering the spectrometer. Therefore, the pumping sections have to reduce the tritium flow by more than 14 orders of magnitude. This paper describes the measurement of the reduction factor of the differential pumping section performed with high purity tritium gas during the first measurement campaigns of the KATRIN experiment. The reduction factor results are compared with previously performed simulations, as well as the stringent requirements of the KATRIN experiment.Comment: 19 pages, 4 figures, submitted to Vacuu

Improved Upper Limit on the Neutrino Mass from a Direct Kinematic Method by KATRIN.

We report on the neutrino mass measurement result from the first four-week science run of the Karlsruhe Tritium Neutrino experiment KATRIN in spring 2019. Beta-decay electrons from a high-purity gaseous molecular tritium source are energy analyzed by a high-resolution MAC-E filter. A fit of the integrated electron spectrum over a narrow interval around the kinematic end point at 18.57 keV gives an effective neutrino mass square value of (-1.0_{-1.1}^{+0.9})  eV^{2}. From this, we derive an upper limit of 1.1 eV (90% confidence level) on the absolute mass scale of neutrinos. This value coincides with the KATRIN sensitivity. It improves upon previous mass limits from kinematic measurements by almost a factor of 2 and provides model-independent input to cosmological studies of structure formation

Lack of association between gene polymorphisms of Angiotensin converting enzyme, Nod-like receptor 1, Toll-like receptor 4, FAS/FASL and the presence of Helicobacter pylori-induced premalignant gastric lesions and gastric cancer in Caucasians

<p>Abstract</p> <p>Background</p> <p>Several polymorphisms of genes involved in the immunological recognition of <it>Helicobacter pylori </it>and regulating apoptosis and proliferation have been linked to gastric carcinogenesis, however reported data are partially conflicting. The aim of our study was to evaluate potential associations between the presence of gastric cancer (GC) and high risk atrophic gastritis (HRAG) and polymorphisms of genes encoding <it>Angiotensin converting enzyme </it>(<it>ACE</it>), <it>Nod-like receptor 1 </it>(<it>NOD1</it>), <it>Toll-like receptor 4 </it>(<it>TLR4</it>) and <it>FAS/FASL</it>.</p> <p>Methods</p> <p>Gene polymorphisms were analyzed in 574 subjects (GC: n = 114; HRAG: n = 222, controls: n = 238) of Caucasian origin. <it>ACE I/D </it>(rs4646994), <it>NOD1 796G>A </it>(rs5743336), <it>TLR4 3725G>C </it>(rs11536889), <it>FAS 1377G>A </it>(rs2234767), <it>FAS 670A>G </it>(rs1800682) and <it>FASL 844T>C </it>(rs763110) were genotyped by different PCR approaches and restriction fragment length polymorphism analysis.</p> <p>Results</p> <p>Frequencies of genotypes in our study are similar to the data reported on subjects of Caucasian ethnicity. There was a tendency for <it>NOD1 796G/G </it>genotype to be associated with increased risk of HRAG (62.4% <it>vs</it>. 54.5% in controls, <it>p </it>= 0.082). <it>FAS 670G/G </it>genotype was more frequent in HRAG when compared to controls, 23.9% and 17.2% respectively, however it failed to reach significance level (<it>p </it>= 0.077). We did not find any significant associations for all polymorphisms in relation to GC or HRAG. <it>NOD1 796G>A </it>and <it>TLR4 3725G>C </it>gene polymorphisms were also not associated with <it>Helicobacter pylori </it>infection.</p> <p>Conclusions</p> <p><it>ACE, NOD1, TRL4 </it>and <it>FAS/FASL </it>gene polymorphisms are not linked with gastric carcinogenesis in Caucasians, and therefore they should not be considered as potential biomarkers for identifying individuals with higher risk for GC.</p