131 research outputs found
Counting contact terms in decays
We clarify the origin and cancellation of contact terms in the weak
annihilation amplitudes contributing to . It is demonstrated
that the photon emission from the final-state quarks vanishes in the chiral
limit of massless quarks. The contact terms in the QCD light-cone sum rule
evaluation of the weak annihilation amplitudes are also discussed.Comment: 16 pages, 2 figures, Latex, ws-p8-50x6-00.cls, to be published in
Sergei Matinian Festschrift ``From Integrable Models to Gauge Theories.'',
Eds. V. Gurzadyan, A. Sedrakyan, World Scientific, 200
Axinos in Cosmology and at Colliders
The axino, the fermionic superpartner of the axion, is a well-motivated
candidate for cold dark matter if it is the lightest supersymmetric particle.
Since the axino couples very weakly to the matter multiplets, the
next-to-lightest supersymmetric particle (NLSP) has a long lifetime, which has
important consequences for both cosmology and collider phenomenology. Assuming
that a charged slepton is the NLSP, we calculate the complete leading one- and
two-loop contributions to its decay. We analyze in detail constraints on the
parameters space from cosmology and discuss how this scenario can be probed at
colliders. Scenarios in which both the axino and the gravitino are lighter than
the long-lived charged slepton are also explored with particular emphasis on
cosmological constraints and collider phenomenology.Comment: 64 pages, 22 figure
at Next-to-Leading Order in Chiral Perturbation Theory
The weak decay is a powerful probe of axion-like particles
(ALPs). In this work, we provide a comprehensive analysis of this process
within chiral perturbation theory, extending existing calculations by including
complete next-to-leading order (NLO) contributions and isospin-breaking
corrections at first order in . We show that the consistent
incorporation of ALPs in the QCD and weak chiral Lagrangians requires a
non-trivial extension of the corresponding operator bases, which we describe in
detail. Furthermore, we show that in the presence of an ALP the so-called weak
mass term, which is unobservable in the Standard Model, is non-redundant
already at leading order. We find that NLO corrections associated with
flavor-violating ALP couplings modify the leading-order result by a few
percent, with only small uncertainties. On the contrary, the NLO corrections
proportional to flavor-conserving ALP couplings lead to an
reduction relative to the leading-order predictions. These corrections are
accompanied by a large uncertainties mainly originating from the QCD low-energy
constant as well as from the presence of various unknown weak
low-energy constants. We emphasize the importance of a precise determination of
these coupling parameters for the successful study of new physics in light
meson decays.Comment: 35 pages, 8 figure
Health-related quality of life after radical prostatectomy and low-dose-rate brachytherapy for localized prostate cancer
To evaluate quality of life (QOL) after radical retropubic prostatectomy (RP) and low-dose-rate brachytherapy (BT)
Float, explode or sink: postmortem fate of lung-breathing marine vertebrates
What happens after the death of a marine tetrapod in seawater? Palaeontologists and neontologists have claimed that large lung-breathing marine tetrapods such as ichthyosaurs had a lower density than seawater, implying that their carcasses floated at the surface after death and sank subsequently after leakage of putrefaction gases (or ‘‘carcass explosions''). Such explosions would thus account for the skeletal disarticulation observed frequently in the fossil record. We examined the taphonomy and sedimentary environment of numerous ichthyosaur skeletons and compared them to living marine tetrapods, principally cetaceans, and measured abdominal pressures in human carcasses. Our data and a review of the literature demonstrate that carcasses sink and do not explode (and spread skeletal elements). We argue that the normally slightly negatively buoyant carcasses of ichthyosaurs would have sunk to the sea floor and risen to the surface only when they remained in shallow water above a certain temperature and at a low scavenging rate. Once surfaced, prolonged floating may have occurred and a carcass have decomposed gradually. Our conclusions are of significance to the understanding of the inclusion of carcasses of lung-breathing vertebrates in marine nutrient recycling. The postmortem fate has essential implications for the interpretation of vertebrate fossil preservation (the existence of complete, disarticulated fossil skeletons is not explained by previous hypotheses), palaeobathymetry, the physiology of modern marine lung-breathing tetrapods and their conservation, and the recovery of human bodies from seawate
Phenomenology of Mirror Fermions in the Littlest Higgs Model with T-Parity
Little Higgs models are an interesting alternative to explain electroweak
symmetry breaking without fine-tuning. Supplemented with a discrete symmetry
(T-parity) constraints from electroweak precision data are naturally evaded and
also a viable dark matter candidate is obtained. T-parity implies the existence
of new (mirror) fermions in addition to the heavy gauge bosons of the little
Higgs models. In this paper we consider the effects of the mirror fermions on
the phenomenology of the littlest Higgs model with T-parity at the LHC. We
study the most promising production channels and decay chains for the new
particles. We find that the mirror fermions have a large impact on the
magnitude of signal rates and on the new physics signatures. Realistic
background estimates are given.Comment: 13 p
Unstable particles in One Loop Calculations
We present a gauge invariant way to compute one loop corrections to processes
involving the production and decay of unstable particles.Comment: 21 pages latex, <A
HREF=http://pss058.psi.ch/preprints/unstablefull.ps>ps file,
PSI-PR-93-22, REVISED. (Completely rewritten due to many complaints about the
unclear exposition.
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