26 research outputs found
Signatures of large composite Dark Matter states
We investigate the interactions of large composite dark matter (DM) states
with the Standard Model (SM) sector. Elastic scattering with SM nuclei can be
coherently enhanced by factors as large as A^2, where A is the number of
constituents in the composite state (there exist models in which DM states of
very large A > 10^8 may be realised). This enhancement, for a given direct
detection event rate, weakens the expected signals at colliders by up to 1/A.
Moreover, the spatially extended nature of the DM states leads to an
additional, characteristic, form factor modifying the momentum dependence of
scattering processes, altering the recoil energy spectra in direct detection
experiments. In particular, energy recoil spectra with peaks and troughs are
possible, and such features could be confirmed with only O(50) events,
independently of the assumed halo velocity distribution. Large composite states
also generically give rise to low-energy collective excitations potentially
relevant to direct detection and indirect detection phenomenology. We compute
the form factor for a generic class of such excitations - quantised surface
modes - finding that they can lead to coherently-enhanced, but generally
sub-dominant, inelastic scattering in direct detection experiments. Finally, we
study the modifications to capture rates in astrophysical objects that follow
from the elastic form factor, as well as the effects of inelastic interactions
between DM states once captured. We argue that inelastic interactions may lead
to the DM collapsing to a dense configuration at the centre of the object.Comment: 30 pages, 5 figures, v2; references and minor additional comments
adde
PI3Kδ and primary immunodeficiencies.
Primary immunodeficiencies are inherited disorders of the immune system, often caused by the mutation of genes required for lymphocyte development and activation. Recently, several studies have identified gain-of-function mutations in the phosphoinositide 3-kinase (PI3K) genes PIK3CD (which encodes p110δ) and PIK3R1 (which encodes p85α) that cause a combined immunodeficiency syndrome, referred to as activated PI3Kδ syndrome (APDS; also known as p110δ-activating mutation causing senescent T cells, lymphadenopathy and immunodeficiency (PASLI)). Paradoxically, both loss-of-function and gain-of-function mutations that affect these genes lead to immunosuppression, albeit via different mechanisms. Here, we review the roles of PI3Kδ in adaptive immunity, describe the clinical manifestations and mechanisms of disease in APDS and highlight new insights into PI3Kδ gleaned from these patients, as well as implications of these findings for clinical therapy
Dark Matter in the Milky Way's Dwarf Spheroidal Satellites
The Milky Way's dwarf spheroidal satellites include the nearest, smallest and
least luminous galaxies known. They also exhibit the largest discrepancies
between dynamical and luminous masses. This article reviews the development of
empirical constraints on the structure and kinematics of dSph stellar
populations and discusses how this phenomenology translates into constraints on
the amount and distribution of dark matter within dSphs. Some implications for
cosmology and the particle nature of dark matter are discussed, and some
topics/questions for future study are identified.Comment: A version with full-resolution figures is available at
http://www.cfa.harvard.edu/~mwalker/mwdsph_review.pdf; 70 pages, 22 figures;
invited review article to be published in Vol. 5 of the book "Planets, Stars,
and Stellar Systems", published by Springe