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.

New considerations for PM, Black Carbon and particle number concentration for air quality monitoring across different European cities

Abstract: In many large cities of Europe standard air quality limit values of particulate matter (PM) are exceeded. Emis- sions from road traffic and biomass burning are frequently reported to be the major causes. As a consequence of these exceedances a large number of air quality plans, most of them focusing on traffic emissions reductions, have been imple- mented in the last decade. In spite of this implementation, a number of cities did not record a decrease of PM levels. Thus, is the efficiency of air quality plans overestimated? Do the road traffic emissions contribute less than expected to am- bient air PM levels in urban areas? Or do we need a more specific metric to evaluate the impact of the above emissions on the levels of urban aerosols? This study shows the results of the interpretation of the 2009 variability of levels of PM, Black Carbon (BC), aerosol number concentration (N) and a number of gaseous pollu- tants in seven selected urban areas covering road traffic, ur- ban background, urban-industrial, and urban-shipping envi- ronments from southern, central and northern Europe. The results showed that variations of PM and N levels do not always reflect the variation of the impact of road traf-

Review of Urban Secondary Organic Aerosol Formation from Gasoline and Diesel Motor Vehicle Emissions

Abstract: Secondary organic aerosol (SOA) is formed from the atmospheric oxidation of gas-phase organic compounds leading to the formation of particle mass. Gasoline- and diesel-powered motor vehicles, both on/off-road, are important sources of SOA precursors. They emit complex mixtures of gas-phase organic compounds that vary in volatility and molecular structure—factors that influence their contributions to urban SOA. However, the relative importance of each vehicle type with respect to SOA formation remains unclear due to conflicting evidence from recent laboratory, field, and modeling studies. Both are likely important, with evolving contributions that vary with location and over short time scales. This review summarizes evidence, research needs, and discrepancies between top-down and bottom-up approaches used to estimate SOA from motor vehicles, focusing on inconsistencies between molecular-level understanding and regional observations. The effect of emission controls (e.g., exhaust aftertreatment technologies...

Simultaneous explanation of R(D (∗)) and b→sμ + μ −: the last scalar leptoquarks standing

Abstract: Over the past years, experiments accumulated intriguing hints for new physics (NP) in flavor observables, namely in the anomalous magnetic moment of the muon (a μ ), in R(D (∗)) = Br(B → D (∗) τ ν)/Br(B → D (∗) lν) and in b → sμ + μ − transitions, which are all at the 3 − 4 σ level In this article we point out that one can explain the R(D (∗)) anomaly using two scalar leptoquarks (LQs) with the same mass and coupling to fermions related via a discrete symmetry: an SU(2) L singlet and an SU(2) L triplet, both with hypercharge Y = −2/3 In this way, potentially dangerous contributions to b → sνν are avoided and non-CKM suppressed effects in R(D (∗)) can be generated This allows for smaller overall couplings to fermions weakening the direct LHC bounds In our model, R(D (∗)) is directly correlated to b → sτ + τ − transitions where an enhancement by orders of magnitude compared to the standard model (SM) is predicted, such that these decay modes are in the reach of LHCb and BELLE II Furthermore, one can also naturally explain the b → sμ + μ − anomalies (including R(K)) by a C 9 = −C 10 like contribution without spoiling μ − e universality in charged current decays In this case sizable effects in b → sτ μ transitions are predicted which are again well within the experimental reach One can even address the longstanding anomaly in a μ , generating a sizable decay rate for τ → μγ However, we find that out of the three anomalies R(D (∗)), b → sμ + μ − and a μ only two (but any two) can be explained simultaneously We point out that a very similar phenomenology can be achieved using a vector leptoquark SU(2) L singlet with hypercharge 2/3 In this case, no tuning between couplings is necessary, but the model is non-renormalizable

Negative flat band magnetism in a spin–orbit-coupled correlated kagome magnet

Abstract: Electronic systems with flat bands are predicted to be a fertile ground for hosting emergent phenomena including unconventional magnetism and superconductivity1–15, but materials that manifest this feature are rare. Here, we use scanning tunnelling microscopy to elucidate the atomically resolved electronic states and their magnetic response in the kagome magnet Co3Sn2S2 (refs. 16–20). We observe a pronounced peak at the Fermi level, which we identify as arising from the kinetically frustrated kagome flat band. On increasing the magnetic field up to ±8 T, this state exhibits an anomalous magnetization-polarized many-body Zeeman shift, dominated by an orbital moment that is opposite to the field direction. Such negative magnetism is induced by spin–orbit-coupling quantum phase effects21–25 tied to non-trivial flat band systems. We image the flat band peak, resolve the associated negative magnetism and provide its connection to the Berry curvature field, showing that Co3Sn2S2 is a rare example of a kagome magnet where the low-energy physics can be dominated by the spin–orbit-coupled flat band. The authors show that a magnetic material with kagome lattice planes hosts a flat band near the Fermi level. Electrons in this band exhibit ‘negative magnetism’ due to the Berry curvature.