3,433 research outputs found
Role of Scalar Meson Resonances in $K_{L}^{0} \rightarrow \pi^{0} \gamma \gamma Decay
Corrections to decay induced by
scalar meson exchange are studied within chiral perturbation theory. In spite
of bad knowledge of scalar-mesons parameters, the calculated branching ratio
can be changed by a few percent.Comment: 18 pages of text, 2 figures (available upon request); preprint
IJS-TP-16-94 , TUM-T31-63-94
Long distance contribution to decay and terms in CHPT
The long distance contribution to is
calculated using chiral perturbation theory. The leading contribution comes
from tree terms. The branching ratio of the long distance
contribution is found to be of order smaller than the short distance
contributions.Comment: 12 pages, 1 figure (available upon request
The Role of Underutilization of Protective Behavioral Strategies in the Relation of Social Anxiety with Risky Drinking
Social anxiety is prominent among undergraduates and increases the risk of experiencing alcohol problems. In fact, social anxiety more than quadruples the risk of developing an alcohol use disorder, yet it is inconsistently related to heavier drinking. Inconsistent findings may be due to lack of attention on protective behavioral strategies (PBS) among socially anxious drinkers. PBS are cognitive-behavioral strategies to reduce drinking and alcohol-related harm. Due to the nature of social anxiety, affected individuals may be especially vulnerable to PBS underutilization, leading to heavier and more problematic drinking. The current study examined the mediating role of PBS in the relationships of social anxiety with past-month drinking and alcohol problems using cross-sectional data among current (past-month) heavy undergraduate drinkers (N = 431). Social anxiety was significantly positively related to past-month alcohol problems and peak drinking. Social anxiety was significantly negatively related to typical drinking, drinking frequency, and PBSS Manner of Drinking. Social anxiety was indirectly (via PBSS Manner of Drinking) related to greater past-month peak drinks and more drinking problems. Findings suggest that socially anxious persons may be vulnerable to heavier and more problematic drinking due to PBS underutilization. Treatment implications are discussed
Rare Kaon Decays in the -Expansion
We study the unknown coupling constants that appear at order in the
Chiral Perturbation Theory analysis of ,
and decays. To that
end, we compute the chiral realization of the Hamiltonian
in the framework of the -expansion of the low-energy action. The
phenomenological implications are also discussed.Comment: 18 pages, LaTeX, CPT-92/P.279
Dispersion Relation Bounds for pi pi Scattering
Axiomatic principles such as analyticity, unitarity and crossing symmetry
constrain the second derivative of the pi pi scattering amplitudes in some
channels to be positive in a region of the Mandelstam plane. Since this region
lies in the domain of validity of chiral perturbation theory, we can use these
positivity conditions to bound linear combinations of \bar{l}_1 and \bar{l}_2.
We compare our predictions with those derived previously in the literature
using similar methods. We compute the one-loop pi pi scattering amplitude in
the linear sigma model (LSM) using the MS-bar scheme, a result hitherto absent
in the literature. The LSM values for \bar{l}_1 and \bar{l}_2 violate the
bounds for small values of m_sigma/m_pi. We show how this can occur, while
still being consistent with the axiomatic principles.Comment: 12 pages, 8 figures. Two references added, a few minor changes.
Published versio
One loop corrections to quantum hadrodynamics with vector mesons
The renormalized elastic scattering amplitude to one loop is
calculated in the chiral limit in the model and in a Quantum
Hadrodynamic model (QHD-III) with vector mesons. It is argued that QHD-III
reduces to the linear model in the limit that the vector meson masses
become large. The pion decay constant is also calculated to 1-loop in the
model, and at tree level in QHD-III; it is shown that the coefficient
of the tree level term in the scattering amplitude equals . The
1-loop correction of in QHD-III violates strong isospin current
conservation. Thus,it is concluded that QHD-III can, at best, only describe the
strongly interacting nuclear sector.Comment: 6 page
Navigation-Assisted Posterior Open Reduction and Internal Fixation in a C-CLAMP Fashion for an Isolated C1 Fracture.
C1 fractures with an intact transverse ligament are usually treated conservatively. Patients who present with a progressive diastasis of bone fragments and a progressive articular subluxation mainly attributed to progressive lengthening of the transverse ligament (TAL) fibers can be treated with a C1 "C-clamp" fusion. A 75-year-old male who sustained a motor vehicle accident was neurologically intact. A computed tomography (CT) imaging demonstrated a Jefferson's type-C1 fracture with a slight lateral displacement of the C1 left lateral mass (LM) and a rotatory subluxation on the right. MRI showed an intact TAL and demonstrated an isolated rupture of the left alar ligament. Conservative treatment was chosen. Radiographic follow-up showed, at 3 months, progressive lateral mass displacement, most likely due to elongation of the TAL fibers; this was also associated with a persistent mechanical neck pain. For this reason, we performed a posterior reduction and internal fixation in a C-clamp fashion by placement of C1 lateral mass screws and posterior compression sparing the C1-2 joint. Using navigation, a 3.5-mm screw was inserted into the LM bilaterally. The screw heads were then connected with a rod and compression was applied before tightening. Postoperative CT scan demonstrated a satisfying reduction and further imaging will be made during the follow-up. The patient had a considerable relief of neck pain. Simple lateral mass fixation with C-clamp technique is a reasonable option in case of isolated C1 fractures in patients who have failed conservative management while preserving the range of motion (ROM) at the atlanto-axial joint. The link to the video can be found at: https://youtu.be/x8bsVwzCt_M
Radiative Kaon Decays and Direct CP Violation
It is stressed that a measurement of the electric dipole amplitude for direct
photon emission in \kpm decays through its interference with inner
bremsstrahlung is important for differentiating among various models. Effects
of amplitude CP violation in the radiative decays of the charged kaon are
analyzed in the Standard Model in conjunction with the large approach. We
point out that gluon and electromagnetic penguin contributions to the
CP-violating asymmetry between the Dalitz plots of \kpm are of equal weight.
The magnitude of CP asymmetry ranges from to when the photon energy in the kaon rest frame varies from 50 MeV to
170 MeV.Comment: Latex, 11 pages, ITP-SB-93-36, IP-ASTP-22-9
Vector and Scalar Meson Resonances in Decays
Corrections to induced by vector and scalar meson
exchange are investigated within chiral perturbation theory.Comment: 15pages, Latex-file, TUM-T31-41/9
Rare Kaon Decays
The current status of rare kaon decay experiments is reviewed. New limits in
the search for Lepton Flavor Violation are discussed, as are new measurements
of the CKM matrix.Comment: 8 pages, 3 figures, LaTeX, presented at the 3rd International
Conference on B Phyiscs and CP Violation, Taipei December 3-7, 199
- …