2,841 research outputs found
Determination of the Gaugino Mass Parameter M_1 in Different Linear Collider Modes
We study the different linear collider modes with regard to the determination
of the gaugino mass parameter M_1. In a specific mSUGRA inspired scenario we
compare four processes with polarized beams: (a) e+ e- --> neutralino_1
neutralino_2 --> neutralino_1 neutralino_1 e+ e-, (b) e- gamma --> neutralino_1
selectron_{L/R} --> neutralino_1 neutralino_1 e-, (c) gamma gamma -->
chargino_1^+ chargino_1^- --> neutralino_1 neutralino_1 e+ e- neutrino_e
anti-neutrino_e, (d) e- e- --> selectron_{L/R} selectron_{L/R} --> neutralino_1
neutralino_1 e- e-.Comment: 5 pages, 8 figures, LaTex, Talk given at the 5th International Linear
Collider Workshop (LCWS 2000), Fermilab, Batavia, Illinois, Oct. 24-28, 200
Selectron Pair Production at e-e- and e+e- Colliders with Polarized Beams
We investigate selectron pair production and decay in e-e- scattering and
e+e- annihilation with polarized beams taking into account neutralino mixing as
well as ISR and beamstrahlung corrections. One of the main advantages of having
both modes at disposal is their complementarity concerning the threshold
behaviour of selectron pair production. In e-e- the cross sections at threshold
for seleectron_R selectron_R and selectron_L selectron_L rise proportional to
the momentum of the selectron and in e+ e- that for selectron_R selectron_L.
Measurements at threshold with polarized beams can be used to determine the
selectron masses precisely. Moreover we discuss how polarized electron and
positron beams can be used to establish directly the weak quantum numbers of
the selectrons. We also use selectron pair production to determine the gaugino
mass parameter M_1. This is of particular interest for scenarios with
non-universal gaugino masses at a high scale resulting in |M_1| << |M_2| at the
electroweak scale. Moreover, we consider also the case of a non-vanishing
selectron mixing and demonstrate that it leads to a significant change in the
phenomenology of selectrons.Comment: LaTex, 23 pages, 14 figures, v2, typos corrected, version to appear
in Eur.Phys.J.
Thinking about denial
This essay notes the frequent and varied uses of ‘denial’ in modern political discourse, suggests the specific psychoanalytic meanings the term has acquired and asks how useful such Freudian concept may be for historians. It notes the long and vexed debates that have occurred over the uses of psychoanalysis in historiography, before comparing and contrasting ‘denial’ with other terms that have particular psychoanalytic inflections, such as ‘disavowal’, ‘splitting’ and ‘negation’. The authors dwell, especially, on ‘disavowal’ and argue it may, sometimes provide a particularly useful basis for exploring how and why states of knowing and not knowing co-exist, in individuals and groups. This account also provide particular historical examples: most briefly, a fragment from a report about the war criminals, produced by an American psychiatrist at the Nuremberg Trial; at greater length, the political arguments and historical writings of an eighteenth-century slave owner; and finally, a case in a borough of London in the late-twentieth-century London, where the neglect, abuse and murder of a child was shockingly ‘missed’ by a succession of social agencies and individuals, who had evidence of the violence available to them. The essay refers more briefly to various more recent discussions, of denial and associated, relevant terms in the work of psychoanalysts, psychologists, and social theorists
Observation of a nanophase segregation in LiCl aqueous solutions from Transient Grating Experiments
Transient Grating experiments performed on supercooled LiCl, RH2O solutions
with R>6 reveal the existence of a strong, short time, extra signal which
superposes to the normal signal observed for the R=6 solution and other glass
forming systems. This extra signal shows up below 190 K, its shape and the
associated timescale depend only on temperature, while its intensity increases
with R. We show that the origin of this signal is a phase separation between
clusters with a low solute concentration and the remaining, more concentrated,
solution. Our analysis demonstrates that these clusters have a nanometer size
and a composition which are rather temperature independent, while increasing R
simply increases the number of these clusters.Comment: 19 pages+ 8 figures+ 2 table
Interference of Higgs boson resonances in mu^+ mu^- -> neutralino_i neutralino_j with longitudinal beam polarization
We study the interference of resonant Higgs boson exchange in neutralino
production in \mu^+ \mu^- annihilation with longitudinally polarized beams. We
use the energy distribution of the decay lepton in the process \neutralino_j
\to \ell^\pm \slepton^\mp to determine the polarization of the neutralinos. In
the CP conserving Minimal Supersymmetric Standard Model a non-vanishing
asymmetry in the lepton energy spectrum is caused by the interference of Higgs
boson exchange channels with different CP eigenvalues. The contribution of this
interference is large if the heavy neutral bosons H and A are nearly
degenerate. We show that the asymmetry can be used to determine the couplings
of the neutral Higgs bosons to the neutralinos. In particular, the asymmetry
allows to determine the relative phase of the couplings. We find large
asymmetries and cross sections for a set of reference scenarios with nearly
degenerate neutral Higgs bosons.Comment: 20 pages, 6 figures, minor typos corrected, to appear in Eur. Phys.
J.
Regular vs. classical M\"obius transformations of the quaternionic unit ball
The regular fractional transformations of the extended quaternionic space
have been recently introduced as variants of the classical linear fractional
transformations. These variants have the advantage of being included in the
class of slice regular functions, introduced by Gentili and Struppa in 2006, so
that they can be studied with the useful tools available in this theory. We
first consider their general properties, then focus on the regular M\"obius
transformations of the quaternionic unit ball B, comparing the latter with
their classical analogs. In particular we study the relation between the
regular M\"obius transformations and the Poincar\'e metric of B, which is
preserved by the classical M\"obius transformations. Furthermore, we announce a
result that is a quaternionic analog of the Schwarz-Pick lemma.Comment: 14 page
A trade-off between reproductive investment and maternal cerebellum size in a precocial bird
This is the author accepted manuscript. The final version is available from the Royal Society via the DOI in this record.Natural selection favours increased investment in reproduction, yet considerable variation in parental investment is observed in natural populations. Life-history theory predicts that this variation is maintained by a trade-off between the benefits of increased reproductive investment and its associated costs for the parents. The nature of these costs of reproduction, however, remains poorly understood. The brain is an energetically highly expensive organ and increased reproductive investment may, therefore, negatively affect brain maintenance. Using artificial selection lines for high and low prenatal maternal investment in a precocial bird, the Japanese quail (Coturnix japonica), we provide experimental evidence for this hypothesis by showing that increased prenatal provisioning negatively affects the size of a particular brain region of the mother, the cerebellum. Our finding suggests that cognitive demands may constrain the evolution of parental investment, and vice versa, contributing to the maintenance of variation in reproductive behaviour in animal populations.This work was supported by the Swiss National Science Foundation (PP00P3_128386, PP00P3_157455 to B.T.) and the Georges und Antoine Claraz-Schenkung (to C.E.)
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