Aspects of Track-Assisted Mass

Track-assisted mass is a proxy for jet mass that only uses direction information from charged particles, allowing it to be measured at the Large Hadron Collider with very fine angular resolution. In this paper, we introduce a generalization of track-assisted mass and analyze its performance in both parton shower generators and resummed calculations. For the original track-assisted mass, the track-only mass is rescaled by the charged energy fraction of the jet. In our generalization, the rescaling factor includes both per-jet and ensemble-averaged information, facilitating a closer correspondence to ordinary jet mass. Using the track function formalism in electron-positron collisions, we calculate the spectrum of generalized track-assisted mass to next-to-leading-logarithmic order with leading-order matching. These resummed calculations provide theoretical insight into the close correspondence between track-assisted mass and ordinary jet mass. With the growing importance of jet grooming algorithms, we also calculate track-assisted mass on soft-drop groomed jets.Comment: 35+17 pages, 22 figures; v3: improvements to calculation and presentation to appear in JHE

Rescaling in flood risk governance – new spatial and institutional arrangements and structures

Flood governance and policy in Europe are changing: the role of the state and individual responsibility for risk management are now key contemporary issues in flood policy. The new policy agenda has been implemented to enhance the responsibilities of local authorities in flood risk management and reduce the controlling role of central national governments. The new strategies place the lead responsibility on local organisations to determine local strategies to manage local risks. This thesis examines the new role of these local authorities and organisations in flood risk management as well as how the nature of partnerships are established and operate, focusing especially on the main barriers and challenges. In principle, local authorities should be able to lead partnerships with local stakeholders to ensure effective local flood risk management. However, with current pressures on local authorities to reduce spending and a parallel reduction in the central state’s resources, partnership has been seen as a possibility to both increase the value of budgets available. The central aspects of this thesis are to investigate and to explore the influence of new scales on the interaction and performance of the different actors and their relationships; particularly with regard to power, processes and scaled networks.The research was carried out through a series of semi-structured interviews with both regional and local stakeholders in Austria and England. It demonstrates not only the importance of network connections between actors at the same scale, but refers also to the networks between actors and stakeholders at different scales, especially between local and national level. Local engagement strongly depends on social capacities, such as knowledge, motivation/self-interest, economics, networks, organisation and procedural capacity

Energy flow polynomials: A complete linear basis for jet substructure

We introduce the energy flow polynomials: a complete set of jet substructure observables which form a discrete linear basis for all infrared- and collinear-safe observables. Energy flow polynomials are multiparticle energy correlators with specific angular structures that are a direct consequence of infrared and collinear safety. We establish a powerful graph-theoretic representation of the energy flow polynomials which allows us to design efficient algorithms for their computation. Many common jet observables are exact linear combinations of energy flow polynomials, and we demonstrate the linear spanning nature of the energy flow basis by performing regression for several common jet observables. Using linear classification with energy flow polynomials, we achieve excellent performance on three representative jet tagging problems: quark/gluon discrimination, boosted W tagging, and boosted top tagging. The energy flow basis provides a systematic framework for complete investigations of jet substructure using linear methods.Comment: 41+15 pages, 13 figures, 5 tables; v2: updated to match JHEP versio

Spiral-shaped wavefronts in a sunspot umbra

Solar active regions show a wide variety of oscillatory phenomena. The presence of the magnetic field leads to the appearance of several wave modes, whose behavior is determined by the sunspot thermal and magnetic structure. We aim to study the relation between the umbral and penumbral waves observed at the high photosphere and the magnetic field topology of the sunspot. Observations of the sunspot in active region NOAA 12662 obtained with the GREGOR telescope (Observatorio del Teide, Spain) were acquired on 2017 June 17. The data set includes a temporal series in the Fe I 5435 \AA\ line obtained with the imaging spectrograph GREGOR Fabry-P\'erot Interferometer (GFPI) and a spectropolarimetric raster map acquired with the GREGOR Infrared Spectrograph (GRIS) in the 10830 \AA\ spectral region. The Doppler velocity deduced from the restored Fe I 5435 \AA\ line has been determined, and the magnetic field vector of the sunspot has been inferred from spectropolarimetric inversions of the Ca I 10839 \AA\ and the Si I 10827 \AA\ lines. A two-armed spiral wavefront has been identified in the evolution of the two-dimensional velocity maps from the Fe I 5435 \AA\ line. The wavefronts initially move counterclockwise in the interior of the umbra, and develop into radially outward propagating running penumbral waves when they reach the umbra-penumbra boundary. The horizontal propagation of the wavefronts approximately follows the direction of the magnetic field, which shows changes in the magnetic twist with height and horizontal position. The spiral wavefronts are interpreted as the visual pattern of slow magnetoacoustic waves which propagate upward along magnetic field lines. Their apparent horizontal propagation is due to their sequential arrival to different horizontal positions at the formation height of the Fe I 5435 \AA\ line, as given by the inclination and orientation of the magnetic field.Comment: Accepted for publication in A&

An operational definition of quark and gluon jets

While "quark" and "gluon" jets are often treated as separate, well-defined objects in both theoretical and experimental contexts, no precise, practical, and hadron-level definition of jet flavor presently exists. To remedy this issue, we develop and advocate for a data-driven, operational definition of quark and gluon jets that is readily applicable at colliders. Rather than specifying a per-jet flavor label, we aggregately define quark and gluon jets at the distribution level in terms of measured hadronic cross sections. Intuitively, quark and gluon jets emerge as the two maximally separable categories within two jet samples in data. Benefiting from recent work on data-driven classifiers and topic modeling for jets, we show that the practical tools needed to implement our definition already exist for experimental applications. As an informative example, we demonstrate the power of our operational definition using Z+jet and dijet samples, illustrating that pure quark and gluon distributions and fractions can be successfully extracted in a fully well-defined manner.Comment: 38 pages, 10 figures, 1 table; v2: updated to match JHEP versio

Partnership Funding in flood risk management: multi-level stakeholder engagement - a question of roles and power

The paper examines the new flood risk policy discussion in England and Wales. The summer floods in England in 2007 caused large damages to the environment, economy and humanity. Following this key flood event, the Government has started to redefine the national flood and coastal risk management policy in England and Wales. The key issue in the new policy agenda is to encourage the responsibilities of local authorities and reduce the central role of flood risk management. This decentralisation in flood risk management has a series of consequences in the development of new governance structures. The main reason for this shift from central to local level is the belief that local authorities deal with public administration tasks in a more efficient way. Nevertheless, the main problem is the gap between the delegated tasks and the lack of transfer of resources, especially the issue concerning funding is still unclear and unresolved. This constraint will go with fiscal and administration cuts. The consequences will be (1) ‘hollowing out’ of the Government with the downscaling of the responsibility towards local actors and (2) without proportional transfer of resources to local authorities they will not be able to deal with new tasks. Therefore, in practice there are many limitations, barriers and concerns with the new policy direction

Partnership funding in flood risk management: new localism debate and policy in England

The new flood risk policy discussion in England has started to redefine national policy regarding flood and coastal risk management. The key issue in the new policy agenda is to encourage the responsibilities of local authorities in flood risk management, which involve defining local strategies to manage local risks. This downscaling process in flood risk management has a series of consequences in the development of new governance structures and institutions as well as new working relations and intervention strategies. Nevertheless, the main problem is the gap between the downscaling of responsibility and the transfer of resources; in particular the question concerning funding and social capacity. In this way, the focus of policy discussion refers to two main aspects: (a) the equitable sharing of risk-burdens between public authorities, private companies and individuals and (b) how to encourage government agencies and nongovernment agents to take over responsibility for certain tasks from central government. The aim of this paper is to discuss the new funding regime for English flood risk management policy under the new policy paradigm

Evolving interregional co-operation in flood risk management: distances and types of partnership approaches in Austria

Flood risk management and policy in Europe are changing, so the role of local and catchment-wide flood risk management plans are now key contemporary issues in flood policy. A new policy agenda is to enhance inter-local solutions instead of local flood alleviation schemes. This paper analyses the new role of those local authorities and stakeholders in flood risk management as well as how the nature of the partnerships are established and operate, focusing especially on the main barriers and challenges. This paper examines catchment-based flood risk management in Austria. Catchment-based flood risk management was analysed in three different Austrian regions (Aist in Upper Austria, Triesting-Tal in Lower Austria and Ill-Walgau in Vorarlberg). The current functions of a partnership approach in flood risk prevention lie within the selection of sites for conservation of regionally important retention areas, harmonising spatial planning instruments and awareness-raising for protective measures on an inter-local level. The empirical results are currently characterized by a lack of sufficient co-operation between the members as well as with the regional authorities. The three case studies show different backgrounds and developments. The results show that the inter-local co-operation process is in no cases fully achieved. Some of the case studies show a higher integration in one field than others

Partnership approaches in flood risk management: lessons from the Eastern Alps

In the past decades flood risk management has taken a paradigm shift away from a structural, securitybased approach towards more an integrated, risk-based approach. While the ‘traditional’ approach was informed by afirm belief in controlling rivers via engineering solutions, flood risk management today increasingly acknowledgesthe importance of providing ‘more space for the rivers’. The new policy agenda has been implemented to enhance the development of catchment-wide management plans in flood risk management and at the same time to reduce the controlling role of central national governments. The aim of the paper is to examine the new role of these local authorities and organisations in flood risk management as well as how the nature of partnerships are established and operate, focusing especially on the main barriers and challenges. The current goal of this partnership approach lies with the conservation of regionally important retention areas for protective measures on an inter-local level. An important issue is that of compensation measures between upstream and downstream communities, which at present is causing many conflicts. We conclude that although a catchment-wide management approach may be seen as an ‘optimal’ solution for flood risk management. However, in practice there are many limitations and barriers in establishing these collaborations and making them effective