Paul Scherrer Institute

About: Paul Scherrer Institute is a facility organization based out in Villigen, Switzerland. It is known for research contribution in the topics: Neutron & Large Hadron Collider. The organization has 9248 authors who have published 23984 publications receiving 890129 citations. The organization is also known as: PSI.

Ultrahigh Mass Resolution and Accurate Mass Measurements as a Tool To Characterize Oligomers in Secondary Organic Aerosols

Abstract: Organic aerosols are a major fraction, often more than 50%, of the total atmospheric aerosol mass. The chemical composition of the total organic aerosol mass is poorly understood, although hundreds of compounds have been identified in the literature. High molecular weight compounds have recently gained much attention because this class of compounds potentially represents a major fraction of the unexplained organic aerosol mass. Here we analyze secondary organic aerosols, generated in a smog chamber from alpha-pinene ozonolysis with ultra-high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). About 450 compounds are detected in the mass range of m/z 200-700. The mass spectrum is clearly divided into a low molecular weight range (monomer) and a high molecular weight range, where dimers and trimers are distinguishable. Using the Kendrick mass analysis, the elemental composition of about 60% of all peaks could be determined throughout the whole mass range. Most compounds have high O:C ratios between 0.4 and 0.6. Small compounds (i.e., monomers) have a higher maximum O:C ratio than dimers and trimers, suggesting that condensation reactions with, for example, the loss of water are important in the oligomer formation process. A program developed in-house was used to determine exact mass differences between peaks in the monomer, dimer, and trimer mass range to identify potential monomer building blocks, which form the co-oligomers observed in the mass spectrum. A majority of the peaks measured in the low mass region of the spectrum (m/z < 300) is also found in the calculated results. For the first time the elemental composition of the majority of peaks over a wide mass range was determined using advanced data analysis methods for the analysis of ultra-high-resolution MS data. Possible oligomer formation mechanisms in secondary organic aerosols were investigated.

Resummation of double logarithms in electroweak high-energy processes

Abstract: At future linear ${e}^{+}{e}^{\ensuremath{-}}$ collider experiments in the TeV range, Sudakov double logarithms originating from massive boson exchange can lead to significant corrections to the cross sections of the observable processes. These effects are important for the high precision objectives of the Next Linear Collider. We use the infrared evolution equation, based on a gauge invariant dispersive method, to obtain double logarithmic asymptotics of scattering amplitudes and discuss how it can be applied, in the case of broken gauge symmetry, to the standard model of electroweak processes. We discuss the double logarithmic effects to both non-radiative processes and to processes accompanied by soft gauge boson emission. In all cases the Sudakov double logarithms are found to exponentiate. We also discuss double logarithmic effects of a non-Sudakov type which appear in Regge-like processes.

Search for axionlike dark matter through nuclear spin precession in electric and magnetic fields

Abstract: We report on a search for ultra-low-mass axion-like dark matter by analysing the ratio of the spinprecession frequencies of stored ultracold neutrons and 199Hg atoms for an axion-induced oscillating electric dipole moment of the neutron and an axion-wind spin-precession effect. No signal consistent with dark matter is observed for the axion mass range 1024 eV ma 10 17 eV. Our null result sets the first laboratory constraints on the coupling of axion dark matter to gluons, which improve on astrophysical limits by up to 3 orders of magnitude, and also improves on previous laboratory constraints on the axion coupling to nucleons by up to a factor of 40.

A Unique Matched Quadruplet of Terbium Radioisotopes for PET and SPECT and for α- and β−-Radionuclide Therapy: An In Vivo Proof-of-Concept Study with a New Receptor-Targeted Folate Derivative

Abstract: Terbium offers 4 clinically interesting radioisotopes with complementary physical decay characteristics: 149Tb, 152Tb, 155Tb, and 161Tb. The identical chemical characteristics of these radioisotopes allow the preparation of radiopharmaceuticals with identical pharmacokinetics useful for PET (152Tb) and SPECT diagnosis (155Tb) and for α- (149Tb) and β−-particle (161Tb) therapy. The goal of this proof-of-concept study was to produce all 4 terbium radioisotopes and assess their diagnostic and therapeutic features in vivo when labeled with a folate-based targeting agent. Methods:161Tb was produced by irradiation of 160Gd targets with neutrons at Paul Scherrer Institute or Institut Laue-Langevin. After neutron capture, the short-lived 161Gd decays to 161Tb. 149Tb, 152Tb, and 155Tb were produced by proton-induced spallation of tantalum targets, followed by an online isotope separation process at ISOLDE/CERN. The isotopes were purified by means of cation exchange chromatography. For the in vivo studies, we used the DOTA–folate conjugate cm09, which binds to folate receptor (FR)–positive KB tumor cells. Therapy experiments with 149Tb-cm09 and 161Tb-cm09 were performed in KB tumor–bearing nude mice. Diagnostic PET/CT (152Tb-cm09) and SPECT/CT (155Tb-cm09 and 161Tb-cm09) studies were performed in the same tumor mouse model. Results: Carrier-free terbium radioisotopes were obtained after purification, with activities ranging from approximately 6 MBq (for 149Tb) to approximately 15 GBq (for 161Tb). The radiolabeling of cm09 was achieved in a greater than 96% radiochemical yield for all terbium radioisotopes. Biodistribution studies showed high and specific uptake in FR-positive tumor xenografts (23.8% ± 2.5% at 4 h after injection, 22.0% ± 4.4% at 24 h after injection, and 18.4% ± 1.8% at 48 h after injection). Excellent tumor-to-background ratios at 24 h after injection (tumor to blood, ∼15; tumor to liver, ∼5.9; and tumor to kidney, ∼0.8) allowed the visualization of tumors in mice using PET (152Tb-cm09) and SPECT (155Tb-cm09 and 161Tb-cm09). Compared with no therapy, α- (149Tb-cm09) and β−-particle therapy (161Tb-cm09) resulted in a marked delay in tumor growth or even complete remission (33% for 149Tb-cm09 and 80% for 161Tb-cm09) and a significantly increased survival. Conclusion: For the first time, to our knowledge, 4 terbium radionuclides have been tested in parallel with tumor-bearing mice using an FR targeting agent. Along with excellent tumor visualization enabled by 152Tb PET and 155Tb SPECT, we demonstrated the therapeutic efficacy of the α-emitter 149Tb and β−-emitter 161Tb.

Importance of Loop Effects in Explaining the Accumulated Evidence for New Physics in B Decays with a Vector Leptoquark.

Abstract: In recent years experiments revealed intriguing hints for new physics (NP) in $B$ decays involving $b\ensuremath{\rightarrow}c\ensuremath{\tau}\ensuremath{ u}$ and $b\ensuremath{\rightarrow}s{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ transitions at the $4\ensuremath{\sigma}$ and $5\ensuremath{\sigma}$ level, respectively. In addition, there are slight disagreements in $b\ensuremath{\rightarrow}u\ensuremath{\tau}\ensuremath{ u}$ and $b\ensuremath{\rightarrow}d{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ observables. While not significant on their own, they point in the same direction. Furthermore, ${V}_{us}$ extracted from $\ensuremath{\tau}$ decays shows a slight tension ($\ensuremath{\approx}2.5\ensuremath{\sigma}$) with its value determined from Cabibbo-Kobayashi-Maskawa unitarity, and an analysis of BELLE data found an excess in ${B}_{d}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$. Concerning NP explanations, the vector leptoquark SU(2) singlet is of special interest since it is the only single particle extension of the standard model which can (in principle) address all the anomalies described above. For this purpose, large couplings to $\ensuremath{\tau}$ leptons are necessary and loop effects, which we calculate herein, become important. Including them in our phenomenological analysis, we find that neither the tension in ${V}_{us}$ nor the excess in ${B}_{d}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$ can be fully explained without violating bounds from $K\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{ u}\overline{\ensuremath{ u}}$. However, one can account for $b\ensuremath{\rightarrow}c\ensuremath{\tau}\ensuremath{ u}$ and $b\ensuremath{\rightarrow}u\ensuremath{\tau}\ensuremath{ u}$ data finding intriguing correlations with ${B}_{q}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$ and $K\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{ u}\overline{\ensuremath{ u}}$. Furthermore, the explanation of $b\ensuremath{\rightarrow}c\ensuremath{\tau}\ensuremath{ u}$ predicts a positive shift in ${C}_{7}$ and a negative one in ${C}_{9}$, being nicely in agreement with the global fit to $b\ensuremath{\rightarrow}s{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ data. Finally, we point out that one can fully account for $b\ensuremath{\rightarrow}c\ensuremath{\tau}\ensuremath{ u}$ and $b\ensuremath{\rightarrow}s{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ without violating bounds from $\ensuremath{\tau}\ensuremath{\rightarrow}\ensuremath{\phi}\ensuremath{\mu}$, $\mathrm{\ensuremath{\Upsilon}}\ensuremath{\rightarrow}\ensuremath{\tau}\ensuremath{\mu}$, or $b\ensuremath{\rightarrow}s\ensuremath{\tau}\ensuremath{\mu}$ processes.