Are there eta-Helium bound states?

Using multiple scattering theory the scattering lengths of $\eta$ mesons on helium nuclei are calculated and checked against final state $\eta$ interactions from the $pd \rightarrow \eta ^3$He and $dd \rightarrow \eta ^4$He reactions. The existence of an $\eta^4$He quasibound state is indicated.Comment: revtex, 23 pages, 3 figures available by fax or mai

Distributional Implications of Tax Relief on Voluntary Private Pensions in Spain*

Using taxation statistics, this paper explores the distributional implications of tax relief on private pensions in Spain in 2002. For this purpose, the author suggests a decomposition of the Kakwani index and its generalisations that allows us to distinguish between the regressivity caused by targeting and that due to benefits allocation among recipients. This paper finds that these tax incentives are regressive - mainly for the latter reason - and have negative although small distributional effects. Finally, this work presents several proposals for reform of the current system and simulates their implications for equity. Copyright 2007 Institute for Fiscal Studies.