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4.5 Fundamental Interactions
what are the absolute neutrino masses and their ordering
(hierarchy) are of primary importance. Neutrino-less
double β decay experiments and direct neutrino mass
determinations from β decay address these questions
and should therefore be strongly supported. Improved
nuclear matrix element calculations as well as auxiliary
measurements are important to derive or constrain the
effective Majorana neutrino mass.
Neutrino mixing parameters and the CP
violating phases
The central focus of upcoming and future reactor and
accelerator neutrino oscillation experiments is the measurement
of the mixing angle θ 13 and the study of the CP
violating Dirac δ-phase. CP violating Majorana phases
will manifest themselves in neutrino-less double β decay
experiments and can be studied by comparing the results
with those from direct neutrino mass measurements
(single β decay) and cosmology. Strong support is
needed for R&D studies crucial for such experiments
that have tight connection with future radioactive ion
beam facilities, such as for example production of high
ion intensities for candidate beta-beam emitters.
Electroweak Interactions
Precision measurements in β decay
Better limits on possible types of new physics will be
obtained from a more precise unitary test of the quark
mixing matrix. The current puzzle with respect to neutron
lifetime should be addressed with high priority. Also,
higher precision in correlation measurements is essential
to search for non Standard Model weak interactions.
Increased exotic beam and neutron intensities, particle
traps, including developments to store polarised nuclei,
as well as improved simulation codes for keV to MeV
electrons are crucial to this.
Precise QED studies within the Standard
Model
Accurate QED predictions and precision measurements
are necessary for improved determination of fundamental
constants such as α, magnetic moments, or particle
masses. Further developments in atomic structure calculations
including QED effects are required to interpret
APNC experiments and to extract nuclear properties
from precise atomic measurements.
4.5.6 Recommendations
In order to achieve the challenging physics goals listed in
the previous section the European nuclear physics community
needs an appropriate environment consisting of
adequate academic positions for young researchers and
state of the art facilities. These comprise centrally:
Priority 1.
Support of small-sized laboratories
and university groups
There is a need for continuous support of small-sized
laboratories and university-based groups. In these stimulating
environments young people are trained and new
techniques are developed and tested before they move
to the larger facilities and large-scale infrastructures.
a. Detector development
The development of detectors with better resolution and
efficiency is crucial to experiments in this field.
b. Development work to improve
the possibilities with particle traps
Particle traps are by now well established in fundamental
physics research. Improvements and new developments
will extend their applicability (e.g. with respect
to polarised trapped samples), to increase the accuracy
of results and address new observables.
Priority 2.
Theoretical support
Well-founded theoretical guidance and input is indispensable
to select the best experimental options in view of
the many technological possibilities that exist nowadays.
Theory groups should therefore be supported and more
theoreticians should be attracted to this field.
Priority 3.
Facilities
a. Precise QED studies with intense sources
of low-energy antiprotons
Anti-matter research is exploring very basic principles,
a main topic here being tests of CPT. Intense sources
of low-energy antiprotons will boost this fascinating
field with the potential for a large public outreach. They
are indispensable for making progress in exotic atom
spectroscopy and searches for new interactions such
as anti-gravity.
b. Development work to improve
the underground laboratories
Improved sensitivities for e.g. double β decay experiments,
but also for other measurements requiring low
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