56,650 research outputs found
The prompt lepton cookbook
We review the calculation of the prompt lepton flux, produced in the
atmosphere by the semileptonic decay of charmed particles. We describe side by
side the intermediary ingredients used by different authors, which include not
only the charm production model, but also other atmospheric particle showering
parameters. After evaluating separately the relevance of each single
ingredient, we analyze the effect of different combinations over the final
result. We highlight the impact of the prompt lepton flux calculation upon
high-energy neutrino telescopes.Comment: 21 pages, 10 figures; revised version, accepted for publication in
Astroparticle Physic
The Star Cluster Systems of the Magellanic Clouds
The characteristics of the cluster systems of the Magellanic Clouds, as
inferred from integrated properties, are compared with those from individual
cluster studies and from the field population. The agreement is generally
satisfactory though in the case of the LMC, the lack of clusters older than ~3
Gyr is not reflected in the field population. The possible origin(s) for this
cluster ``age-gap'' are discussed. The SMC cluster age-metallicity relation is
also presented and discussed.Comment: 11 pages, 4 figures. To appear in the Proceedings of IAU Symposium
207, "Extragalactic Star Clusters", eds E. Grebel, D. Geisler and D. Minnit
A Second Shell in the Fornax dSph Galaxy
In the search for tidal structure in Galactic satellite systems, we have
conducted a photometric survey over a 10 square degree area centred on the
Fornax dSph galaxy. The survey was made in two colours, and the resulting
colour-magnitude data were used as a mask to select candidate Fornax RGB stars,
thereby increasing the contrast of Fornax stars to background sources in the
outer regions. Previously, we reported the presence of a shell (age 2 Gyr)
located towards the centre of Fornax. In this contribution we reveal a second
shell, significantly larger than the first, located 1.3 degrees NW from the
centre of Fornax, outside the nominal tidal radius. Moreover, the distribution
of Fornax RGB stars reveals two lobes extending to the spatial limit of our
survey, and aligned with the minor axis and with the two shells. These results
support the hypothesis of a merger between Fornax and a gas-rich companion
approximately 2 Gyr ago.Comment: Four pages,accepted for the Publications of the Astronomical Society
of Australia. Contribution the annual ASA meeting, Brisbane 200
Superstring dualities and p-brane bound states
We show that the M-theory/IIA and IIA/IIB superstring dualities together with
the diffeomorphism invariance of the underlying theories require the presence
of certain p-brane bound states in IIA and IIB superstring theories preserving
1/2 of the spacetime supersymmetry. We then confirm the existence of IIA and
IIB supergravity solutions having the appropriate p-brane bound states
interpretation.Comment: 21 pages, Phyzzx, Minor corrections, Version that will appear in
Nucl. Phys.
Beliefs and actions in the trust game: creating instrumental variables to estimate the causal effect
In many economic contexts, an elusive variable of interest is the agent's expectation about relevant events, e.g. about other agents' behavior. Recent experimental studies as well as surveys have asked participants to state their beliefs explicitly, but little is known about the causal relation between beliefs and other behavioral variables. This paper discusses the possibility of creating exogenous instrumental variables for belief statements, by shifting the probabilities of the relevant events. We conduct trust game experiments where the amount sent back by
the second player (trustee) is exogenously varied by a random process, in a way that informs only the �first player (trustor) about the realized variation. The procedure
allows detecting causal links from beliefs to actions under plausible assumptions.
The IV estimates indicate a signi�ficant causal effect, comparable to the connection
between beliefs and actions that is suggested by OLS analyses
- …