Measurements of Collins and Sivers asymmetries at COMPASS

COMPASS is a fixed target experiment presently running at CERN. In 2002, 2003, and 2004 the experiment used a 160 GeV polarized muon beam coming from SPS and scattered off a $^6$LiD target. The nucleons in the target can be polarized either longitudinally or transversely with respect to the muon beam and 20% of the running time has been devoted to transverse polarization. From the transverse polarization data collected in 2002, which correspond to a total integrated luminosity of about 200 pb$^{-1}$, the Collins and the Sivers asymmetries have been determined separately and the preliminary results are presented here.Comment: 4 pages, 1 figure, presented at SPIN2004 International Symphosium, October 10-16 2004, Trieste, Ital

Uncertainties in polarimetric 3D reconstructions of coronal mass ejections

This work is aimed at quantifying the uncertainties in the 3D reconstruction of the location of coronal mass ejections (CMEs) obtained with the polarization ratio technique. The method takes advantage of the different distributions along the line of sight (LOS) of total (tB) and polarized (pB) brightnesses to estimate the average location of the emitting plasma. To this end, we assumed two simple electron density distributions along the LOS (a constant density and Gaussian density profiles) for a plasma blob and synthesized the expected tB and pB for different distances $z$ of the blob from the plane of the sky (POS) and different projected altitudes $\rho$. Reconstructed locations of the blob along the LOS were thus compared with the real ones, allowing a precise determination of uncertainties in the method. Independently of the analytical density profile, when the blob is centered at a small distance from the POS (i.e. for limb CMEs) the distance from the POS starts to be significantly overestimated. Polarization ratio technique provides the LOS position of the center of mass of what we call folded density distribution, given by reflecting and summing in front of the POS the fraction of density profile located behind that plane. On the other hand, when the blob is far from the POS, but with very small projected altitudes (i.e. for halo CMEs, $\rho < 1.4$ R$_\odot$), the inferred distance from that plane is significantly underestimated. Better determination of the real blob position along the LOS is given for intermediate locations, and in particular when the blob is centered at an angle of $20^\circ$ from the POS. These result have important consequences not only for future 3D reconstruction of CMEs with polarization ratio technique, but also for the design of future coronagraphs aimed at providing a continuous monitoring of halo-CMEs for space weather prediction purposes

The Political Economy of Corporate Governance

We analyze the political determinants of investor and employment protection. Our model predicts that proportional electoral systems are conducive to weaker investor protection and stronger employment protection than majoritarian systems. This prediction is consistent with international panel data evidence. The proportionality of the voting system is significantly and negatively correlated with shareholder protection in a panel of 45 countries, and positively correlated with employment protection in a panel of 21 OECD countries. Also other political variables appear to affect regulatory outcomes, especially for the labor market. The origin of the legal system has some additional explanatory power only for employment protection.political economy, shareholder protection, corporate governance, employment legislation, takeovers, mergers and acquisitions.

Securitization, Transparency and Liquidity

We present a model in which issuers of asset backed securities choose to release coarse information to enhance the liquidity of their primary market, at the cost of reducing secondary market liquidity or even causing it to freeze. The degree of transparency is inefficiently low if the social value of secondary market liquidity exceeds its private value. We analyze various types of public intervention — mandatory transparency standards, provision of liquidity to distressed banks or secondary market price support — and find that they have quite different welfare implications. Finally, transparency is greater if issuers restrain the issue size, or tranche it so as to sell the more information-sensitive tranche to sophisticated investors only.securitization, transparency, liquidity, rating, subprime, crisis, default

Shareholder Protection, Stock Market Development, and Politics

This paper presents a political economy model where there is mutual feedback between investor protection and stock market development. Better investor protection induces companies to issue more equity and thereby leads to a broader stock market. In turn, equity issuance expands the shareholder base and increases support for shareholder protection. This feedback loop can generate multiple equilibria, with investor protection and stock market size being positively correlated across equilibria. The model’s predictions are tested on panel data for 47 countries over 1993-2002, controlling for country and year effects and endogeneity issues. We also document international convergence in shareholder protection to best-practice standards, and show that it is correlated with cross-border M&A activity, consistent with the model.political economy, shareholder protection, corporate governance, stock market

The Political Economy of Finance

If the private benefits of control are high and management owns a small equity stake, managers and workers are natural allies. There are two forces at play. First, managers effectively transform employees into a “poison pill’’ by signing generous long-term labor contracts and thereby reducing the firm’s attractiveness to a raider. Second, employees act as “white squires’’ for the incumbent managers, lobbying against hostile takeovers to protect the high wages enjoyed under incumbent management. Our model is consistent with available empirical findings, and yields new predictions as well.political economy, shareholder protection, corporate governance, bankruptcy law, credit market regulation, financial development, privatization

Credit Ratings Failures and Policy Options

This paper examines the role of credit rating agencies in the subprime crisis that triggered the 2007-08 financial turmoil. We focus on two aspects of ratings that contributed to the boom and bust of the market for structured debt: rating inflation and coarse information disclosure. The paper discusses how regulation can be designed to mitigate these problems in the future. Our preferred policy is to require rating agencies to be paid by investors rather than by issuers and to grant open and free access to data about the loans or securities underlying structured debt products. A more modest (but less effective) approach would be to retain the “issuer pays” model but require issuers to pay an upfront fee irrespective of the rating, ban “rating shopping”, and prescribe a more complete format for the information that rating agencies must disseminate.credit rating agencies, securitization, default, liquidity, crisis, transparency

Future capabilities of CME polarimetric 3D reconstructions with the METIS instrument: A numerical test

Understanding the 3D structure of coronal mass ejections (CMEs) is crucial for understanding the nature and origin of solar eruptions. To derive information on the 3D structure of CMEs from white-light (total and polarized brightness) images, the polarization ratio technique is widely used. The soon-to-be-launched METIS coronagraph on board Solar Orbiter will use this technique to produce new polarimetric images. We determine the accuracy at which the position of the centre of mass, direction and speed of propagation, and the column density of the CME can be determined along the line of sight. We perform a 3D MHD simulation of a flux rope ejection where a CME is produced. From the simulation we (i) synthesize the corresponding METIS white-light (total and polarized brightness) images and (ii) apply the polarization ratio technique to these synthesized images and compare the results with the known density distribution from the MHD simulation. We find that the polarization ratio technique reproduces with high accuracy the position of the centre of mass along the line of sight. However, some errors are inherently associated with this determination. The polarization ratio technique also allows information to be derived on the real 3D direction of propagation of the CME. In addition, we find that the column density derived from white-light images is accurate and we propose an improved technique where the combined use of the polarization ratio technique and white-light images minimizes the error in the estimation of column densities. Our method allows us to thoroughly test the performance of the polarization ratio technique and allows a determination of the errors associated with it, which means that it can be used to quantify the results from the analysis of the forthcoming METIS observations in white light (total and polarized brightness)

Simulating AIA observations of a flux rope ejection

Extreme ultraviolet (EUV) images from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO) are providing new insights into the early phase of CME evolution. Observations now show the ejection of magnetic flux ropes from the solar corona and how they evolve into CMEs. These observations are difficult to interpret in terms of basic physical mechanisms and quantities. To fully understand CMEs we need to compare equivalent quantities derived from both observations and theoretical models. To this end we aim to produce synthesised AIA observations from simluations of a flux rope ejection. To carry this out we include the role of thermal conduction and radiative losses, both of which are important for determining the temperature distribution of the solar corona during a CME. We perform a simulation where a flux rope is ejected from the solar corona. From the density and temperature of the plasma in the simulation we synthesise AIA observations. The emission is then integrated along the line of sight using the instrumental response function of AIA. We sythesise observations of AIA in the channels at 304 A, 171 A, 335 A, and 94 A. The synthesised observations show a number of features similar to actual observations and in particular reproduce the general development of CMEs in the low corona as observed by AIA. In particular we reproduce an erupting and expanding arcade in the 304 A and 171 A channels with a high density core. The ejection of a flux rope reproduces many of the features found in the AIA observations. This work is therefore a step forward in bridging the gap between observations and models, and can lead to more direct interpretations of EUV observations in terms of flux rope ejections. We plan to improve the model in future studies in order to perform a more quantitative comparison

Credit ratings failures : causes and policy options

This paper examines the role of credit rating agencies in the subprime crisis, which was at the outset of the ongoing financial turmoil. The focus of the paper is on two aspects that contributed to the boom and bust of the market for asset-backed securities: rating inflation and coarse information disclosure. The paper discusses how regulation can be designed to mitigate these problems in the future. The suggestion is that regulators should require rating agencies to be paid by investors rather than by issuers (or at least constrain the way they are paid by issuers) and force greater disclosure of information about the underlying pool of securities