Heavy Neutral Leptons at FASER

We study the prospects for discovering heavy neutral leptons at ForwArd Search ExpeRiment (FASER), the newly proposed detector at the LHC. Previous studies showed that a relatively small detector with ~10 m length and ~1 m cross sectional area can probe large unconstrained parts of parameter space for dark photons and dark Higgs bosons. In this work we show that FASER will also be sensitive to heavy neutral leptons that have mixing angles with the active neutrinos that are up to an order of magnitude lower than current bounds. In particular, this is true for heavy neutral leptons produced dominantly in $B$-meson decays, in which case FASER's discovery potential is comparable to the proposed SHiP detector. We also illustrate how the search for heavy neutral leptons at FASER will be complementary to ongoing searches in high-$p_T$ experiments at the LHC and can shed light on the nature of dark matter and the process of baryogenesis in the early Universe.Comment: 24 pages, 9 figures; matches to the published versio

Genetic algorithms with memory- and elitism-based immigrants in dynamic environments

Copyright @ 2008 by the Massachusetts Institute of TechnologyIn recent years the genetic algorithm community has shown a growing interest in studying dynamic optimization problems. Several approaches have been devised. The random immigrants and memory schemes are two major ones. The random immigrants scheme addresses dynamic environments by maintaining the population diversity while the memory scheme aims to adapt genetic algorithms quickly to new environments by reusing historical information. This paper investigates a hybrid memory and random immigrants scheme, called memory-based immigrants, and a hybrid elitism and random immigrants scheme, called elitism-based immigrants, for genetic algorithms in dynamic environments. In these schemes, the best individual from memory or the elite from the previous generation is retrieved as the base to create immigrants into the population by mutation. This way, not only can diversity be maintained but it is done more efficiently to adapt genetic algorithms to the current environment. Based on a series of systematically constructed dynamic problems, experiments are carried out to compare genetic algorithms with the memory-based and elitism-based immigrants schemes against genetic algorithms with traditional memory and random immigrants schemes and a hybrid memory and multi-population scheme. The sensitivity analysis regarding some key parameters is also carried out. Experimental results show that the memory-based and elitism-based immigrants schemes efficiently improve the performance of genetic algorithms in dynamic environments.This work was supported by the Engineering and Physical Sciences Research Council (EPSRC) of the United Kingdom under Grant EP/E060722/01

Control Structures and Payout Policy

This paper examines the payout policies of UK firms listed on the London Stock Exchange during the 1990s.It complements the existing literature by analyzing the trends in both dividends and total payouts (including share repurchases).In a dynamic panel data regression setting, we relate target payout ratios to control structure variables.Profitability drives payout decisions of the UK companies, but the presence of strong block holders or block holder coalitions considerably weakens the relationship between corporate earnings and payout dynamics.While the impact of the voting power of shareholders coalitions on payout ratios is found to be always negative, the magnitude of this effect differs across different categories of block holders (i.e. industrial firms, outside individuals, directors, financial institutions).The controlling shareholders appear to trade off the agency problems of free cash flow against the risk of underinvestment, and try to enforce payout policies that optimally balance these two costs.Finally, the paper improves upon some methodological flaws of the recent empirical studies of payout policy.Payout policy;dividend payout;share repurchases;partial adjustment;ownership and control;voting power;Banzhaf power indices;corporate governance;free cash flow;pecking order

Towards understanding thermal history of the Universe through direct and indirect detection of dark matter

We examine the question to what extent prospective detection of dark matter by direct and indirect- detection experiments could shed light on what fraction of dark matter was generated thermally via the freeze-out process in the early Universe. By simulating putative signals that could be seen in the near future and using them to reconstruct WIMP dark matter properties, we show that, in a model- independent approach this could only be achieved in a thin sliver of the parameter space. However, with additional theoretical input the hypothesis about the thermal freeze-out as the dominant mechanism for generating dark matter can potentially be verified. We illustrate this with two examples: an effective field theory of dark matter with a vector messenger and a higgsino or wino dark matter within the MSSM.Comment: 31 pages, 7 figures, extended discussion in section

Axino dark matter with low reheating temperature

We examine axino dark matter in the regime of a low reheating temperature T_R after inflation and taking into account that reheating is a non-instantaneous process. This can have a significant effect on the dark matter abundance, mainly due to entropy production in inflaton decays. We study both thermal and non-thermal production of axinos in the context of the MSSM with ten free parameters. We identify the ranges of the axino mass and the reheating temperature allowed by the LHC and other particle physics data in different models of axino interactions. We confront these limits with cosmological constraints coming the observed dark matter density, large structures formation and big bang nucleosynthesis. We find a number of differences in the phenomenologically acceptable values of the axino mass and the reheating temperature relative to previous studies. In particular, an upper bound on the axino mass becomes dependent on T_R, reaching a maximum value at T_R~10^2 GeV. If the lightest ordinary supersymmetric particle is a wino or a higgsino, we obtain lower a limit of approximately 10 GeV for the reheating temperature. We demonstrate also that entropy production during reheating affects the maximum allowed axino mass and lowest values of the reheating temperature.Comment: v2: improved discussion of warm dark matter bounds, results for stau LOSP adde

What do peer support workers do? A job description.

BackgroundThe extant literature suggests that poorly defined job roles make it difficult for peer support workers to be successful, and hinder their integration into multi-disciplinary workplace teams. This article uses data gathered as part of a participatory evaluation of a peer support program at a psychiatric tertiary care facility to specify the work that peers do.MethodsData were gathered through interviews, focus groups, and activity logs and were analyzed using a modified grounded theory approach.ResultsPeers engage in direct work with clients and in indirect work that supports their work with clients. The main types of direct work are advocacy, connecting to resources, experiential sharing, building community, relationship building, group facilitation, skill building/mentoring/goal setting, and socialization/self-esteem building. The main types of indirect work are group planning and development, administration, team communication, supervision/training, receiving support, education/awareness building, and information gathering and verification. In addition, peers also do work aimed at building relationships with staff and work aimed at legitimizing the peer role. Experience, approach, presence, role modeling, collaboration, challenge, and compromise can be seen as the tangible enactments of peers' philosophy of work.ConclusionsCandidates for positions as peer support workers require more than experience with mental health and/or addiction problems. The job description provided in this article may not be appropriate for all settings, but it will contribute to a better understanding of the peer support worker position, the skills required, and the types of expectations that could define successful fulfillment of the role

Equity Block Transfers in Transition Economies: Evidence from Poland.

This Paper investigates valuation effects of share block transfers and employs agency theory to explain the determinants of block premia. A sample of transactions from Poland is used to measure benefits and costs of ownership concentration. Block premia are found to be substantially lower than in well-developed markets, in spite of the insufficient minority shareholders' protection in transitional economies. Shareholder's opportunities to extract private benefits of control turn out to depend not only on the size of equity stake, but also on the relative power of other block holders. The expropriation threat appears to be most severe in the companies where the free float constitutes a substantial fraction of the shares outstanding. Moreover, the analysis reveals that liquidity costs considerably influence the level of block premia in Poland. Finally, the results document a positive role of the state as an institutional investor in listed companies.