609 research outputs found
Neutrinoless double beta decay in chiral effective field theory: lepton number violation at dimension seven
We analyze neutrinoless double beta decay () within the
framework of the Standard Model Effective Field Theory. Apart from the
dimension-five Weinberg operator, the first contributions appear at dimension
seven. We classify the operators and evolve them to the electroweak scale,
where we match them to effective dimension-six, -seven, and -nine operators. In
the next step, after renormalization group evolution to the QCD scale, we
construct the chiral Lagrangian arising from these operators. We develop a
power-counting scheme and derive the two-nucleon currents up
to leading order in the power counting for each lepton-number-violating
operator. We argue that the leading-order contribution to the decay rate
depends on a relatively small number of nuclear matrix elements. We test our
power counting by comparing nuclear matrix elements obtained by various methods
and by different groups. We find that the power counting works well for nuclear
matrix elements calculated from a specific method, while, as in the case of
light Majorana neutrino exchange, the overall magnitude of the matrix elements
can differ by factors of two to three between methods. We calculate the
constraints that can be set on dimension-seven lepton-number-violating
operators from experiments and study the interplay between
dimension-five and -seven operators, discussing how dimension-seven
contributions affect the interpretation of in terms of the
effective Majorana mass .Comment: Matches version published in JHE
Compression creep of filamentary composites
Axial and transverse strain fields induced in composite laminates subjected to compressive creep loading were compared for several types of laminate layups. Unidirectional graphite/epoxy as well as multi-directional graphite/epoxy and graphite/PEEK layups were studied. Specimens with and without holes were tested. The specimens were subjected to compressive creep loading for a 10-hour period. In-plane displacements were measured using moire interferometry. A computer based data reduction scheme was developed which reduces the whole-field displacement fields obtained using moire to whole-field strain contour maps. Only slight viscoelastic response was observed in matrix-dominated laminates, except for one test in which catastrophic specimen failure occurred after a 16-hour period. In this case the specimen response was a complex combination of both viscoelastic and fracture mechanisms. No viscoelastic effects were observed for fiber-dominated laminates over the 10-hour creep time used. The experimental results for specimens with holes were compared with results obtained using a finite-element analysis. The comparison between experiment and theory was generally good. Overall strain distributions were very well predicted. The finite element analysis typically predicted slightly higher strain values at the edge of the hole, and slightly lower strain values at positions removed from the hole, than were observed experimentally. It is hypothesized that these discrepancies are due to nonlinear material behavior at the hole edge, which were not accounted for during the finite-element analysis
A neutrinoless double beta decay master formula from effective field theory
We present a master formula describing the neutrinoless-double-beta decay
() rate induced by lepton-number-violating (LNV) operators up
to dimension nine in the Standard Model Effective Field Theory. We provide an
end-to-end framework connecting the possibly very high LNV scale to the nuclear
scale, through a chain of effective field theories. Starting at the electroweak
scale, we integrate out the heavy Standard Model degrees of freedom and we
match to an effective theory. After
evolving the resulting effective Lagrangian to the QCD scale, we use chiral
perturbation theory to derive the lepton-number-violating chiral Lagrangian.
The chiral Lagrangian is used to derive the two-nucleon
transition operators to leading order in the chiral power counting. Based on
renormalization arguments we show that in various cases short-range two-nucleon
operators need to be enhanced to leading order. We show that all required
nuclear matrix elements can be taken from existing calculations. Our final
result is a master formula that describes the rate in terms of
phase-space factors, nuclear matrix elements, hadronic low-energy constants,
QCD evolution factors, and high-energy LNV Wilson coefficients, including all
the interference terms. Our master formula can be easily matched to any model
where LNV originates at energy scales above the electroweak scale. As an
explicit example, we match our formula to the minimal left-right-symmetric
model in which contributions of operators of different dimension compete, and
we discuss the resulting phenomenology.Comment: Published versio
Seiberg Duality and e+ e- Experiments
Seiberg duality in supersymmetric gauge theories is the claim that two
different theories describe the same physics in the infrared limit. However,
one cannot easily work out physical quantities in strongly coupled theories and
hence it has been difficult to compare the physics of the electric and magnetic
theories. In order to gain more insight into the equivalence of two theories,
we study the ``e+ e-'' cross sections into ``hadrons'' for both theories in the
superconformal window. We describe a technique which allows us to compute the
cross sections exactly in the infrared limit. They are indeed equal in the
low-energy limit and the equality is guaranteed because of the anomaly matching
condition. The ultraviolet behavior of the total ``e+ e-'' cross section is
different for the two theories. We comment on proposed non-supersymmetric
dualities. We also analyze the agreement of the ``\gamma\gamma'' and ``WW''
scattering amplitudes in both theories, and in particular try to understand if
their equivalence can be explained by the anomaly matching condition.Comment: 24 pages, 2 figures, uses psfi
Relic Abundance of Asymmetric Dark Matter
We investigate the relic abundance of asymmetric Dark Matter particles that
were in thermal equilibrium in the early universe. The standard analytic
calculation of the symmetric Dark Matter is generalized to the asymmetric case.
We calculate the asymmetry required to explain the observed Dark Matter relic
abundance as a function of the annihilation cross section. We show that
introducing an asymmetry always reduces the indirect detection signal from WIMP
annihilation, although it has a larger annihilation cross section than
symmetric Dark Matter. This opens new possibilities for the construction of
realistic models of MeV Dark Matter.Comment: 20 pages, 11 figures, Accepted by JCA
Moving the needle: Directed intervention by the American Society for Surgery of the Hand is effective in encouraging diversity in expert panel composition
PURPOSE: Recent efforts have been made by the American Society for Surgery of the Hand to encourage female inclusion in expert panels. We hypothesized that female representation on expert panels has increased over the past decade and that a directed intervention by the American Society for Surgery of the Hand would be associated with an increased percentage of submissions with female panelists.
METHODS: We performed a retrospective analysis of Instructional Course Lecture and Symposium submissions for the 2011 through 2021 American Society for Surgery of the Hand Annual Meetings. Authorship was reviewed, and the gender of the proposed authors was recorded. Additionally, the status of all-male panel was attributed to panels with no proposed female authors. Submissions were reviewed and compared with meeting programs to determine the status of accepted or rejected. Longitudinal analysis was performed to determine trends in the gender composition of expert panels.
RESULTS: In total, 1,687 submissions were reviewed, including 1,323 Instructional Course Lectures and 364 Symposia. Female authorship constituted 18% of authorship (1,170/6,663), and lead authorship was similarly distributed, with 18% being female (296/1,687). Overall, female representation has increased steadily over the past decade, with females constituting 13% (43/332) and 20% (163/818) of the submitted authors in 2011 and 2020, respectively. Similarly, all-male panels declined from 74% (76/103) to 46% (85/185) of panels over the same timeframe. Most strikingly, a sharp increase in gender representation was observed with the directed intervention noted in the 2021 Call for Abstracts, resulting in an increase in female authorship to 26% (295/1,124) and a decline in all-male panels to 29% (70/241).
CONCLUSIONS: Gender representation among hand surgery expert panels moved toward increased equity over the past decade, which has been aided by directed interventions.
CLINICAL RELEVANCE: Career development and trainee decision making are impacted by gender representation; directed and intentional interventions by professional organizations are effective in encouraging greater equity and diversity within the field
Massive Gravity on a Brane
At present no theory of a massive graviton is known that is consistent with
experiments at both long and short distances. The problem is that consistency
with long distance experiments requires the graviton mass to be very small.
Such a small graviton mass however implies an ultraviolet cutoff for the theory
at length scales far larger than the millimeter scale at which gravity has
already been measured. In this paper we attempt to construct a model which
avoids this problem. We consider a brane world setup in warped AdS spacetime
and we investigate the consequences of writing a mass term for the graviton on
a the infrared brane where the local cutoff is of order a large (galactic)
distance scale. The advantage of this setup is that the low cutoff for physics
on the infrared brane does not significantly affect the predictivity of the
theory for observers localized on the ultraviolet brane. For such observers the
predictions of this theory agree with general relativity at distances smaller
than the infrared scale but go over to those of a theory of massive gravity at
longer distances. A careful analysis of the graviton two-point function,
however, reveals the presence of a ghost in the low energy spectrum. A mode
decomposition of the higher dimensional theory reveals that the ghost
corresponds to the radion field. We also investigate the theory with a brane
localized mass for the graviton on the ultraviolet brane, and show that the
physics of this case is similar to that of a conventional four dimensional
theory with a massive graviton, but with one important difference: when the
infrared brane decouples and the would-be massive graviton gets heavier than
the regular Kaluza--Klein modes, it becomes unstable and it has a finite width
to decay off the brane into the continuum of Kaluza-Klein states.Comment: 26 pages, LaTeX. v2: extended version with an appendix added about
non Fierz-Pauli mass terms. Few typos corrected. Final version appeared in
PR
CPT and Other Symmetries in String/M Theory
We initiate a search for non-perturbative consistency conditions in M theory.
Some non-perturbative conditions are already known in Type I theories; we
review these and search for others. We focus principally on possible anomalies
in discrete symmetries. It is generally believed that discrete symmetries in
string theories are gauge symmetries, so anomalies would provide evidence for
inconsistencies. Using the orbifold cosmic string construction, we give some
evidence that the symmetries we study are gauged. We then search for anomalies
in discrete symmetries in a variety of models, both with and without
supersymmetry. In symmetric orbifold models we extend previous searches, and
show in a variety of examples that all anomalies may be canceled by a
Green-Schwarz mechanism. We explore some asymmetric orbifold constructions and
again find that all anomalies may be canceled this way. Then we turn to Type
IIB orientifold models where it is known that even perturbative anomalies are
non-universal. In the examples we study, by combining geometric discrete
symmetries with continuous gauge symmetries, one may define non-anomalous
discrete symmetries already in perturbation theory; in other cases, the
anomalies are universal. Finally, we turn to the question of CPT conservation
in string/M theory. It is well known that CPT is conserved in all string
perturbation expansions; here in a number of examples for which a
non-perturbative formulation is available we provide evidence that it is
conserved exactly.Comment: 52 pages.1 paragraph added in introduction to clarify assumption
‘Question Moments’: A Rolling Programme of Question Opportunities in Classroom Science
This article has been made available through the Brunel Open Access Publishing Fund.This naturalistic study integrates specific 'question moments' into lesson plans to
increase pupils' classroom interactions. A range of teaching tools has explored
students' ideas through opportunities to ask and write questions. Their oral and written
outcomes provide data on individual and group misunderstandings. Changes to the
schedule of lessons were introduced to discuss these questions and solve disparities.
Flexible lesson planning over fourteen lessons across a four-week period of highschool
chemistry accommodated students' contributions and increased student
participation, promoted inquiring and individualised teaching, with each teaching
strategy feeding forward into the next
The GUT Scale and Superpartner Masses from Anomaly Mediated Supersymmetry Breaking
We consider models of anomaly-mediated supersymmetry breaking (AMSB) in which
the grand unification (GUT) scale is determined by the vacuum expectation value
of a chiral superfield. If the anomaly-mediated contributions to the potential
are balanced by gravitational-strength interactions, we find a
model-independent prediction for the GUT scale of order . The GUT threshold also affects superpartner masses, and can easily
give rise to realistic predictions if the GUT gauge group is asymptotically
free. We give an explicit example of a model with these features, in which the
doublet-triplet splitting problem is solved. The resulting superpartner
spectrum is very different from that of previously considered AMSB models, with
gaugino masses typically unifying at the GUT scale.Comment: 17 page
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