6,164 research outputs found
Theory of Charmless Inclusive B Decays and the Extraction of V_{ub}
We present ``state-of-the-art'' theoretical expressions for the triple
differential B->X_u l^- nu decay rate and for the B->X_s gamma photon spectrum,
which incorporate all known contributions and smoothly interpolate between the
``shape-function region'' of large hadronic energy and small invariant mass,
and the ``OPE region'' in which all hadronic kinematical variables scale with
M_B. The differential rates are given in a form which has no explicit reference
to the mass of the b quark, avoiding the associated uncertainties. Dependence
on m_b enters indirectly through the properties of the leading shape function,
which can be determined by fitting the B->X_s gamma photon spectrum. This
eliminates the dominant theoretical uncertainties from predictions for B->X_u
l^- nu decay distributions, allowing for a precise determination of |V_{ub}|.
In the shape-function region, short-distance and long-distance contributions
are factorized at next-to-leading order in renormalization-group improved
perturbation theory. Higher-order power corrections include effects from
subleading shape functions where they are known. When integrated over
sufficiently large portions in phase space, our results reduce to standard OPE
expressions up to yet unknown O(alpha_s^2) terms. Predictions are presented for
partial B->X_u l^- nu decay rates with various experimental cuts. An elaborate
error analysis is performed that contains all significant theoretical
uncertainties, including weak annihilation effects. We suggest that the latter
can be eliminated by imposing a cut on high lepton invariant mass.Comment: 45 pages, 4 figures; several minor revisions, more systematic
treatment of subleading shape-function effects, numerical results and tables
updated; version to appear in Physical Review
The Curious Case of NGC6908
The object NGC6908 was once thought to be simply a surface-brightness
enhancement in the eastern spiral arm of the nearby spiral galaxy NGC6907.
Based on an examination of near-infrared imaging, the object is shown in fact
to be a lenticular S0(6/7) galaxy hidden in the optical glare of the disk and
spiral structure of the larger galaxy. New radial velocities of NGC6908
(3,060+/-16 (emission); 3,113+/-73 km/s (absorption)) have been obtained at the
Baade 6.5m and the duPont 2.5m telescopes at Las Campanas, Chile placing
NGC6908 at the same expansion-velocity distance as NGC6907 (3,190+/-5 km/s),
eliminating the possibility of a purely chance line-of-sight coincidence. The
once-enigmatic asymmetries in the disk and outer spiral structure of NGC6907
are now explained as being due to an advanced merger event. Newly discovered
tails and debris in the outer reaches of this galaxy further support the merger
scenario for this system. This pair of galaxies is a rather striking example of
two objects discovered over 100 years ago, whose true nature was lost until
modern detectors operating at infrared wavelengths gave us a new
(high-contrast) look. Other examples of embedded merger remnants may also
reveal themselves in the growing samples of near-infrared imaging of nearby
galaxies; and a pilot study does reveal several other promising candidates for
follow-up observations.Comment: 17 pages, 8 figures, accepted for publication in A
Identifying ENSO Phase Impacts on Area Yield Insurance Rates: An Application of Non-Parametric Analysis
The paper reports results of non-parametric analysis of peanut, corn, and cotton yield distributions by the ElNino Southern Oscillation (ENSO) phases in the Southeastern U.S. For validation purposes, the historical yield data is complemented by a set of simulated peanut yields generated using daily weather data. The hypothesis, justified by the observed South-Eastern climate differences and research on ENSO cycles and planting dates, is that different climate conditions during ENSO cycles translate into different yield distributions and, therefore, insurance premiums (loss to coverage ratios). Kernel density estimates of historical county yield data show consistent patterns in the actuarially fair rate schedules grouped by ENSO phases and geographical areas. In particular, corn and cotton yield insurance premiums appear to be the most dependent on the ENSO phases and are the highest, regardless of coverage, during ElNino and the lowest during LaNina. Peanut premiums are higher during Neutral years and lowest during LaNina. The results appear to be robust to the transformations used to make the yield series stationary. While these dependencies do not necessarily correspond to the precipitation and solar radiation characteristics of the corresponding ENSO cycles in the Southeastern US, drawing direct analogies with yield variability is premature as many less documented factors, like the spacing of sunny and rainy days, may be just as important. The comparisons of the empirical and simulated peanut yield distributions show that they are similar in many ways and that the dissimilarities can be explained by known factors. These findings should be more relevant for the area yield insurance as opposed to the APH arrangements as the yield data used in designing contracts for the former reflects the systemic risk more influenced by climate than by the farm-level, basis risk factors accommodated in the APH plans.Risk and Uncertainty, Q140, C220, G220,
Interpretation of runaway electron synchrotron and bremsstrahlung images
The crescent spot shape observed in DIII-D runaway electron synchrotron
radiation images is shown to result from the high degree of anisotropy in the
emitted radiation, the finite spectral range of the camera and the distribution
of runaways. The finite spectral camera range is found to be particularly
important, as the radiation from the high-field side can be stronger by a
factor than the radiation from the low-field side in DIII-D. By
combining a kinetic model of the runaway dynamics with a synthetic synchrotron
diagnostic we see that physical processes not described by the kinetic model
(such as radial transport) are likely to be limiting the energy of the
runaways. We show that a population of runaways with lower dominant energies
and larger pitch-angles than those predicted by the kinetic model provide a
better match to the synchrotron measurements. Using a new synthetic
bremsstrahlung diagnostic we also simulate the view of the Gamma Ray Imager
(GRI) diagnostic used at DIII-D to resolve the spatial distribution of
runaway-generated bremsstrahlung.Comment: 21 pages, 11 figure
ELEMENTARY EDUCATION PROGRAMS TEACHERS AND MTB MLE IMPLEMENTATION IN THE PHILIPPINES
According to the new The K to 12 Basic Education Program implemented in the Philippines in 2013, modifications in pre-service education for aspiring teachers shall be applied to conform to the requirements of both K to 12 and its auxiliary program for the first three levels called Mother Tongue-Based Multilingual Education (MTB-MLE) that mandates the utility of studentsâ mother tongue(s) as medium of instruction. The agencies in charge for these modifications are the Department of Education and the Commission on Higher Education. Their task involves ensuring that the Teacher Education curriculum offered in different higher education institutions in the Philippines will meet the necessary quality standards for new teachers. However, since the implementation of MTB-MLE as a national policy in the School Year 2012-2013, no national guideline has been issued to higher education institutions regarding the said modifications.This paper locates voices of tertiary instructors employed in elementary education programs in four selected universities across the Philippines during the implementation of the MTB-MLE policy. This study specifically sought to determine the interventions applied by university administrations to their elementary education programs to ensure that their adult learnersâ knowledge and skills are aligned with the national policies even without direct guidelines from any macro agents. Central to this paper are the perceptions of the informants regarding the interventions applied by their university administrations to their elementary education programs
Does ethnicity moderate the relationship between communication of the leader and LMX? Perception of employees in Peru
Proceeding of: 47th EIBA Annual Conference 2021, Madrid 10-12 December 2021Book summaries are published (linked in the URL of the publisher).The objective of this research is to determine if ethnic similarity / difference is a relevant variable in the relationship between the leader's communication style and the quality of the leader-follower relationship, in the context of Peru. Using a multidimensional model of the leader's communication style, we have identified that verbal aggressiveness and emotionality are the two dimensions that interact with the ethnic similarity/difference between the leader and the subordinate. Verbal aggressiveness intensifies his negative affect on LMX when leader and subordinate are ethnically similar. The emotionality in the communication of the leader favors the LMX with more intensity if there is an ethnic similarity. The dimensions of expressiveness, precision, questioning and manipulation of the impression of the leader's communication style are not sensitive to ethnicit
The non-self-adjointness of the radial momentum operator in n dimensions
The non self-adjointness of the radial momentum operator has been noted
before by several authors, but the various proofs are incorrect. We give a
rigorous proof that the -dimensional radial momentum operator is not self-
adjoint and has no self-adjoint extensions. The main idea of the proof is to
show that this operator is unitarily equivalent to the momentum operator on
which is not self-adjoint and has no self-adjoint
extensions.Comment: Some text and a reference adde
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