157 research outputs found
Beta Decays and Non-Standard Interactions in the LHC Era
We consider the role of precision measurements of beta decays and light meson
semi-leptonic decays in probing physics beyond the Standard Model in the LHC
era. We describe all low-energy charged-current processes within and beyond the
Standard Model using an effective field theory framework. We first discuss the
theoretical hadronic input which in these precision tests plays a crucial role
in setting the baseline for new physics searches. We then review the current
and upcoming constraints on the various non-standard operators from the study
of decay rates, spectra, and correlations in a broad array of light-quark
systems. We finally discuss the interplay with LHC searches, both within models
and in an effective theory approach. Our discussion illustrates the independent
yet complementary nature of precision beta decay measurements as probes of new
physics, showing them to be of continuing importance throughout the LHC era.Comment: To appear in Prog. Part. Nucl. Phy
Neutron Electric Dipole Moment from Beyond the Standard Model
We discuss the phenomenology of neutron Electric Dipole Moment from the
Standard Model and beyond, and identify the matrix elements most necessary to
connect the current and forthcoming experiments with phenomenology. We then
describe lattice techniques for calculating these matrix elementsComment: Talk presented at Lattice 2012 (7 pages
Spin-dependent conversion
The experimental sensitivity to conversion on nuclei is expected
to improve by four orders of magnitude in coming years. We consider the impact
of flavour-changing tensor and axial-vector four-fermion operators
which couple to the spin of nucleons. Such operators, which have not previously
been considered, contribute to conversion in three ways: in nuclei
with spin they mediate a spin-dependent transition; in all nuclei they
contribute to the coherent (-enhanced) spin-independent conversion via
finite recoil effects and via loop mixing with dipole, scalar, and vector
operators. We estimate the spin-dependent rate in Aluminium (the target of the
upcoming COMET and Mu2e experiments), show that the loop effects give the
greatest sensitivity to tensor and axial-vector operators involving
first-generation quarks, and discuss the complementarity of the spin-dependent
and independent contributions to conversionComment: 6 pages, I figure, typo corrected in eqn
K -> pi pi Phenomenology in the Presence of Electromagnetism
We describe the influence of electromagnetism on the phenomenology of K -> pi
pi decays. This is required because the present data were analyzed without
inclusion of electromagnetic radiative corrections, and hence contain several
ambiguities and uncertainties which we describe in detail. Our presentation
includes a full description of the infrared effects needed for a new
experimental analysis. It also describes the general treatment of final state
interaction phases, needed because Watson's theorem is no longer valid in the
presence of electromagnetism. The phase of the isospin-two amplitude A_2 may be
modified by 50% -> 100%. We provide a tentative analysis using present data in
order to illustrate the sensitivity to electromagnetic effects, and also
discuss how the standard treatment of epsilon'/epsilon is modified.Comment: 25 pages, 6 figure
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