Exact relativistic beta decay endpoint spectrum

The exact relativistic form for the beta decay endpoint spectrum is derived and presented in a simple factorized form. We show that our exact formula can be well approximated to yield the endpoint form used in the fit method of the KATRIN collaboration. We also discuss the three neutrino case and how information from neutrino oscillation experiments may be useful in analyzing future beta decay endpoint experiments.Comment: 12 pages, 3 figure

Sensitivity of Next-Generation Tritium Beta-Decay Experiments for keV-Scale Sterile Neutrinos

We investigate the sensitivity of tritium $\beta$-decay experiments for keV-scale sterile neutrinos. Relic sterile neutrinos in the keV mass range can contribute both to the cold and warm dark matter content of the universe. This work shows that a large-scale tritium beta-decay experiment, similar to the KATRIN experiment that is under construction, can reach a statistical sensitivity of the active-sterile neutrino mixing of $\sin^2\theta \sim 10^{-8}$. The effect of uncertainties in the known theoretical corrections to the tritium $\beta$-decay spectrum were investigated, and found not to affect the sensitivity significantly. It is demonstrated that controlling uncorrelated systematic effects will be one of the main challenges in such an experiment.Comment: 24 pages, 16 figure

Photochemistry in the arctic free troposphere: NOx budget and the role of odd nitrogen reservoir recycling

The budget of nitrogen oxides (NOx) in the arctic free troposphere is calculated with a constrained photochemical box model using aircraft observations from the Tropospheric O3 Production about the Spring Equinox (TOPSE) campaign between February and May. Peroxyacetic nitric anhydride (PAN) was observed to be the dominant odd nitrogen species (NOy) in the arctic free troposphere and showed a pronounced seasonal increase in mixing ratio. When constrained to observed acetaldehyde (CH3CHO) mixing ratios, the box model calculates unrealistically large net NOx losses due to PAN formation (62pptv/day for May, 1-3km). Thus, given our current understanding of atmospheric chemistry, these results cast doubt on the robustness of the CH3CHO observations during TOPSE. When CH3CHO was calculated to steady state in the box model, the net NOx loss to PAN was of comparable magnitude to the net NOx loss to HNO3 (NO2 reaction with OH) for spring conditions. During the winter, net NOx loss due to N2O5 hydrolysis dominates other NOx loss processes and is near saturation with respect to further increases in aerosol surface area concentration. NOx loss due to N2O5 hydrolysis is sensitive to latitude and month due to changes in diurnal photolysis (sharp day-night transitions in winter to continuous sun in spring for the arctic). Near NOx sources, HNO4 is a net sink for NOx; however, for more aged air masses HNO4 is a net source for NOx, largely countering the NOx loss to PAN, N2O5 and HNO3. Overall, HNO4 chemistry impacts the timing of NOx decay and O3 production; however, the cumulative impact on O3 and NOx mixing ratios after a 20-day trajectory is minimal. © 2003 Elsevier Science Ltd. All rights reserved

Ion source for tests of ion behavior in the KATRIN beam line

An electron-impact ion source based on photoelectron emission was developed for ionization of gases at pressures below 1e-4 mbar in an axial magnetic field in the order of 5 T. The ion source applies only DC fields, which makes it suitable for use in the presence of equipment sensitive to radio-frequency (RF) fields. The ion source was succesfully tested under varying conditions regarding pressure, magnetic field and magnetic-field gradient, and the results were studied with the help of simulations. The processes in the ion source are well understood and possibilities for further optimization of generated ion currents are clarified.Comment: 10 pages, 13 figure

Ultra-stable implanted 83Rb/83mKr electron sources for the energy scale monitoring in the KATRIN experiment

The KATRIN experiment aims at the direct model-independent determination of the average electron neutrino mass via the measurement of the endpoint region of the tritium beta decay spectrum. The electron spectrometer of the MAC-E filter type is used, requiring very high stability of the electric filtering potential. This work proves the feasibility of implanted 83Rb/83mKr calibration electron sources which will be utilised in the additional monitor spectrometer sharing the high voltage with the main spectrometer of KATRIN. The source employs conversion electrons of 83mKr which is continuously generated by 83Rb. The K-32 conversion line (kinetic energy of 17.8 keV, natural line width of 2.7 eV) is shown to fulfill the KATRIN requirement of the relative energy stability of +/-1.6 ppm/month. The sources will serve as a standard tool for continuous monitoring of KATRIN's energy scale stability with sub-ppm precision. They may also be used in other applications where the precise conversion lines can be separated from the low energy spectrum caused by the electron inelastic scattering in the substrate.Comment: 30 pages, 10 figures, 1 table, minor revision of the preprint, accepted by JINST on 5.2.201

Relation between CPT Violation in Neutrino masses and mixings

The neutrino parameters determined from the solar neutrino data and the anti-neutrino parameters determined from KamLAND reactor experiment are in good agreement with each other. However, the best fit points of the two sets differ from each other by about $10^{-5}$ eV$^2$ in mass-square differenc and by about $2^\circ$ in the mixing angle. Future solar neutrino and reactor anti-neutrino experiments are likely to reduce the uncertainties in these measurements. This, in turn, can lead to a signal for CPT violation in terms a non-zero difference between neutrino and anti-neutrino parameters. In this paper, we propose a CPT violating mass matrix which can give rise to the above differences in both mass-squared difference and mixing angle and study the constraints imposed by the data on the parameters of the mass matrix.Comment: 10page

Technical design and commissioning of the KATRIN large-volume air coil system

The KATRIN experiment is a next-generation direct neutrino mass experiment with a sensitivity of 0.2 eV (90% C.L.) to the effective mass of the electron neutrino. It measures the tritium $\beta$-decay spectrum close to its endpoint with a spectrometer based on the MAC-E filter technique. The $\beta$-decay electrons are guided by a magnetic field that operates in the mT range in the central spectrometer volume; it is fine-tuned by a large-volume air coil system surrounding the spectrometer vessel. The purpose of the system is to provide optimal transmission properties for signal electrons and to achieve efficient magnetic shielding against background. In this paper we describe the technical design of the air coil system, including its mechanical and electrical properties. We outline the importance of its versatile operation modes in background investigation and suppression techniques. We compare magnetic field measurements in the inner spectrometer volume during system commissioning with corresponding simulations, which allows to verify the system's functionality in fine-tuning the magnetic field configuration. This is of major importance for a successful neutrino mass measurement at KATRIN.Comment: 32 pages, 16 figure

Conditional degradation of SDE2 by the Arg/N-End rule pathway regulates stress response at replication forks

Multiple pathways counteract DNA replication stress to prevent genomic instability and tumorigenesis. The recently identified human SDE2 is a genome surveillance protein regulated by PCNA, a DNA clamp and processivity factor at replication forks. Here, we show that SDE2 cleavage after its ubiquitin-like domain generates Lys-SDE2^(Ct), the C-terminal SDE2 fragment bearing an N-terminal Lys residue. Lys-SDE2^(Ct) constitutes a short-lived physiological substrate of the Arg/N-end rule proteolytic pathway, in which UBR1 and UBR2 ubiquitin ligases mediate the degradation. The Arg/N-end rule and VCP/p97^(UFD1-NPL4) segregase cooperate to promote phosphorylation-dependent, chromatin-associated Lys-SDE2^(Ct) degradation upon UVC damage. Conversely, cells expressing the degradation-refractory K78V mutant, Val-SDE2^(Ct), fail to induce RPA phosphorylation and single-stranded DNA formation, leading to defects in PCNA-dependent DNA damage bypass and stalled fork recovery. Together, our study elucidates a previously unappreciated axis connecting the Arg/N-end rule and the p97-mediated proteolysis with the replication stress response, working together to preserve replication fork integrity