Demonstration of o-Ps detection with a cylindrical array of NaI detectors

Ortho-positronium (o-Ps), the triplet bound state of an electron and positron, is a promising system in which to search for new physics. O-Ps production and detection can be achieved with a tabletop setup, involving a 22Na source, aerogel and a detector. We present our approach to o-Ps detection using the APEX array, which consists of 24 NaI(Tl) bars, arranged cylindrically. Our approach involves tagging on the 1.27 MeV gamma ray, a technique which is used in positron annihilation spectroscopy (PALS) Gidley et al. (2006). We demonstrate the ability to tag with any one of the bars in the array. Using a NaI(Tl) array of high angular coverage (75%) with this technique provides many benefits. This method provides some advantages over tagging on the positron directly insofar as it minimizes the amount of material inside the source holder and simplifies the design of the DAQ. This has potential applications to CP- and CPT-violation searches in o-Ps

Regulation of pH During Amelogenesis

During amelogenesis, extracellular matrix proteins interact with growing hydroxyapatite crystals to create one of the most architecturally complex biological tissues. The process of enamel formation is a unique biomineralizing system characterized first by an increase in crystallite length during the secretory phase of amelogenesis, followed by a vast increase in crystallite width and thickness in the later maturation phase when organic complexes are enzymatically removed. Crystal growth is modulated by changes in the pH of the enamel microenvironment that is critical for proper enamel biomineralization. Whereas the genetic bases for most abnormal enamel phenotypes (amelogenesis imperfecta) are generally associated with mutations to enamel matrix specific genes, mutations to genes involved in pH regulation may result in severely affected enamel structure, highlighting the importance of pH regulation for normal enamel development. This review summarizes the intra- and extracellular mechanisms employed by the enamel-forming cells, ameloblasts, to maintain pH homeostasis and, also, discusses the enamel phenotypes associated with disruptions to genes involved in pH regulation

Performance of the CMS high-level trigger during LHC Run 2

The CERN LHC provided proton and heavy ion collisions during its Run 2 operation period from 2015 to 2018. Proton-proton collisions reached a peak instantaneous luminosity of 2.1 × 1034 cm−2s−1, twice the initial design value, at √ = 13 TeV . The CMS experiment records a subset of the collisions for further processing as part of its online selection of data for physics analyses, using a two-level trigger system: the Level-1 trigger, implemented in custom-designed electronics, and the high-level trigger, a streamlined version of the offline reconstruction software running on a large computer farm. This paper presents the performance of the CMS high-level trigger system during LHC Run 2 for physics objects, such as leptons, jets, and missing transverse momentum, which meet the broad needs of the CMS physics program and the challenge of the evolving LHC and detector conditions. Sophisticated algorithms that were originally used in offline reconstruction were deployed online. Highlights include a machine-learning b tagging algorithm and a reconstruction algorithm for tau leptons that decay hadronically