Mon·Aug 24, 2020Monday·August 24, 2020

1. 01*

   Low background measurement in CANDLES-III for studying the neutrino-less double beta decay of ${}^{48}$Ca

   S. Ajimura🇯🇵 · W.M. Chan🇯🇵 · K. Ichimura🇯🇵 · T. Ishikawa🇯🇵 · K. Kanagawa🇯🇵 · B.T. Khai🇯🇵 · T. Kishimoto🇯🇵 · H. Kino🇯🇵 · T. Maeda🇯🇵 · K. Matsuoka🇯🇵 · N. Nakatani🇯🇵 · M. Nomachi🇯🇵 and 57 other authors

   We developed a CANDLES-III system to study the neutrino-less double beta (0$\nu \beta \beta$) decay of ${}^{48}$Ca. The proposed system employs 96 CaF${}_2$ scintillation crystals (305 kg) with natural Ca (${}^{nat.}$Ca) isotope which corresponds 350\,g of ${}^{48}$Ca. External backgrounds were rejected using a 4$\pi$ active shield of a liquid scintillator surrounding the CaF${}_2$ crystals. The internal backgrounds caused by the radioactive impurities within the CaF${}_2$ crystals can be reduced effectively through analysis of the signal pulse shape. We analyzed the data obtained in the Kamioka underground for a live-time of 130.4\,days to evaluate the feasibility of the low background measurement with the CANDLES-III detector. Using Monte Carlo simulations, we estimated the background rate from the radioactive impurities in the CaF${}_2$ crystals and the rate of high energy $\gamma$-rays caused by the (n, $\gamma$) reactions induced by environmental neutrons. The expected background rate was in a good agreement with the measured rate, i.e., approximately 10${}^{-3}$ events/keV/yr/(kg of ${}^{nat.}$Ca), in the 0$\nu \beta \beta$ window. In conclusion, the background candidates were estimated properly by comparing the measured energy spectrum with the background simulations. With this measurement method, we performed the first search for 0$\nu \beta \beta$ decay in a low background condition using a detector with a Ca isotope, in which the Ca present was not enriched, in a scale of hundreds of kg. The ${}^{48}$Ca isotope has a high potential for use in 0$\nu \beta \beta$ decay search, and is expected to be useful for the development of a next-generation detector for highly sensitive measurements.

   ↳ hep-exnucl-exphysics.ins-detPRD(2021)·35 citations
2. 02*

   Enhanced Tensor Polarization in Solid-State Targets

   Dustin Keller🇺🇸 · Don Crabb🇺🇸 · Donal Day🇺🇸

   We report measurements of enhanced tensor polarization on solid-state targets. The results here represent an increase in tensor polarization over that previously achieved in high energy and nuclear scattering experiments that focused on the measurement of tensor polarized observables. Enhancement techniques are used which require RF produced close to the Larmor frequency of the target spins and use selective semi-saturation resulting from two sources of irradiation, microwave for the DNP process and the additional RF used to manipulate the population of the energy levels in the target material. The spin dynamics of the solid target are used to align the spins enhancing the ensemble average to improve the figure of merit of the scattering experiment. Target rotation at an optimized rate can lead to additional enhancement by applying selective semi-saturation in polycrystalline materials that possess a Pake doublet in their NMR signal.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2020)·24 citations
3. 03*

   Calculating the energy loss of leading jets

   Duff Neill🇺🇸 · Felix Ringer🇺🇸 · Nobuo Sato🇺🇸

   The energy loss mechanism of jets plays a central role in nuclear and high energy physics. We propose direct measurements of the energy loss of leading jets and perform a calculation at next-to-leading logarithmic (NLL${}^{\prime }$) accuracy in the vacuum. The formation of leading jets can be described by jet functions which constitute probability densities and thus allow for a perturbative calculation of the average the energy loss. We identify the following three criteria for a direct measurement of jet energy loss at the cross section level. $i)$ We measure a well defined object, the leading jet, where the formation process can be expressed in terms of a probability density. $ii)$ In addition, we need a measurement of a hard reference scale with respect to which jet energy loss is defined. $iii)$ At leading logarithmic accuracy, we require that the jet energy loss can be identified with parton energy loss. We discuss suitable observables and present numerical results including threshold corrections by making use of a parton shower Monte Carlo approach.

   ↳ hep-phhep-exnucl-exnucl-thPoS(2021)·1 citation

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.