72 research outputs found
Violation of the I=1/2 rule in the nonmesonic weak decay of hypernuclei
Violations of the I=1/2 rule are investigated in the nonmesonic weak
hypernuclear decay using a weak NNN transition potential based on
meson exchange. While the weak I=3/2 matrix elements of baryons with
pseudoscalar mesons are known to be very small, the same matrix elements of
baryons with vector mesons, evaluated in the factorization approximation, are
found to be significant. Within the uncertainties of the factorization
approximation we find that the total rate increases by at most 6% lying within
the error bars of the more recent experimental result. The neutron- to
proton-induced rate, on the other hand, can change by up to a factor of two,
while the asymmetry parameter is strongly affected as well.Comment: 17 pages. Paper related to a contribution presented at the
International Conference on Hypernuclear and Strange Particle Physics
(HYP97). Submitted to Phys. Lett.
Public Awareness of the Nebraska Regional Poison Control Center
A Poison Control Center needs to continually update its impact on the community it serves. At the Nebraska Regional Poison Control Center, a telephone survey was performed to ascertain baseline data for ongoing poison awareness programs. Our data shows that 36.6% of the population would call the PCC in the case of acute poisoning. There is a need to stress that the PCC is not only a center for information but also for treatment at home. Distribution of the PCC phone number to be attached to the phone needs to be increased. Many people obtained the phone number through time consuming methods which would increase the anxiety of the caller. Despite past programs, 63.9% of the respondents were not familiar with Syrup of Ipecac, and overall out of 608, people, 91.1% did not have Syrup of Ipecac at home in case of poisoning. In distributing poison information to the public, the pre-school and other school programs seem to be very effective. Newspapers and television also are an integral part in distributing poison information. With the help of the networks and newspapers in devoting time and space to poison prevention more households can be reached. There is a need to involve the pharmacist in distribution of poison information. Being the major supplier of Syrup of Ipecac, pharmacists can take a more active role by always carrying Syrup of Ipecac, and displaying it so that patrons may be reminded that they should have it at home
Decay of Hypernuclei
We present a nonrelativistic transition potential for the weak
strangeness-changing reaction . The potential is based on a
one meson exchange model (OME), where, in addition to the long-ranged pion, the
exchange of the pseudoscalar , as well as the vector mesons is considered. Results obtained for different hypernuclear decay
observables are compared to the available experimental data.Comment: 8 pages. Invited talk given at the KEK-Tanashi International
Symposium on Physics of Hadrons and Nuclei. Tokyo, Japan, December 14-17,
1998. In honor of Prof. K. Yazaki. Submitted to Nucl. Phys. A. LateX file
(uses espcrc1.sty
Neutron and proton spectra from the decay of hypernuclei
We have determined the spectra of neutrons and protons following the decay of
hypernuclei through the one- and two-nucleon induced mechanisms. The
momentum distributions of the primary nucleons are calculated and a Monte Carlo
simulation is used to account for final state interactions. From the spectra we
calculate the number of neutrons () and protons () per
decay and show how the measurement of these quantities, particularly , can
lead to a determination of , the ratio of neutron to
proton induced decay. We also show that the consideration of the
two-nucleon induced channel has a repercussion in the results, widening the
band of allowed values of with respect to what is
obtained neglecting this channel.Comment: 30 pages, 12 Postscript figures, uuencoded file, ReVTeX, epsf.st
Final State Interactions in Hypernuclear Decay
We present an update of the One-Meson-Exchange (OME) results for the weak
decay of s- and p-shell hypernuclei (Ref. Phys. Rev. C {\bf 56}, 339 (1997)),
paying special attention to the role played by final state interactions between
the emitted nucleons. The present study also corrects for a mistake in the
inclusion of the and exchange mechanisms, which substantially
increases the ratio of neutron-induced to proton-induced transitions,
. With the most up-to-date model ingredients, we find that
the OME approach is able to describe very satisfactorily most of the measured
observables, including the ratio .Comment: 20 pages, 2 eps figure
Clinical characteristics of 80 subjects with KCNQ2-related encephalopathy: Results from a family-driven survey
Variants of KCNQ2 are associated with a wide spectrum of disorders, ranging from Self-limiting Neonatal Epilepsy (SelNE) to Early Onset Developmental and Epileptic Encephalopathy (KCNQ2-DEE). Comorbidities associated with this end of the spectrum have been seldomly described and their impact on the life of patients and their families is yet to be investigated. Collaborating with caregivers from different European family associations, we have developed a questionnaire aimed at investigating the onset and frequency of epileptic seizures, anti-seizure medications (ASM), hospitalizations, stages of development, and comorbidities. Responses from 80 patients, 40 males, from 14 countries have been collected. Median age 7.6 years (4 months - 43.6 years). Of 76 epileptic patients (93.6%), 55.3% were seizure-free with a mean age at last seizure of 26.7 months. Among patients with active epilepsy, those older have a lower frequency of seizures (p > 0.05). We were able to identify three different clusters of varying severity (Mild, Severe, Profound), based on neurodevelopmental features and symptoms, excluding epilepsy. Patients in a higher severity cluster had a higher mean number of comorbidities, which had a higher impact on families. Notably, patients in different clusters presented different epilepsy onset and courses. This study constitutes the most extensive data collection of patients with KCNQ2-DEE, with a focus on comorbidities in a wide age group. The participation of caregivers helps to define the impact of the disease on the lives of patients and families and can help identify new primary and secondary outcomes beyond seizures in future studies
Non-Mesonic Weak Decay of Lambda-hypernuclei: a new determination of the Gn/Gp ratio
Theoretical descriptions of the non-mesonic weak decay of Lambda-hypernuclei
are unable to reproduce the experimental values of the ratio Gn/Gp=G(Lambda n
-> nn)/G(Lambda p -> np). In this contribution we discuss a new approach to
this problem. We have incorporated a one-meson-exchange model for the Lambda N
-> nN transition in finite nuclei in an intranuclear cascade code for the
calculation of double-coincidence nucleon distributions corresponding to the
non-mesonic decay of 5_Lambda-He and 12_Lambda-C. The two-nucleon induced decay
mechanism, Lambda np -> nnp, has been taken into account within a local density
approximation scheme using a one-pion-exchange model supplemented by short
range correlations. A weak decay model independent analysis of preliminary KEK
coincidence data for 5_Lambda-He allows us to extract Gn/Gp=0.39 \pm 0.11 when
the two-nucleon induced channel is neglected (i.e., G2=0) and Gn/Gp=0.26 \pm
0.11 when G2/G1=0.2.Comment: 7 pages, 1 figure. Invited talk at the International Conference on
Hypernuclear and Strange Particle Physics (HYP2003), Jefferson Lab, Newport
News, Virginia (USA), Oct 14-18, 200
An EFT for the weak interaction
The nonleptonic weak interaction, responsible for
the dominant, nonmesonic decay of all but the lightest hypernuclei, is studied
in the framework of an effective field theory. The long-range physics is
described through tree-level exchange of the SU(3) Goldstone bosons ( and
), while the short-range potential is parametrized in terms of lowest-order
contact terms obtained from the most general non-derivative local four-fermion
interaction. Fitting to available weak hypernuclear decay rates for , and yields
reasonable values for the low-energy constants.Comment: Contribution to the Proceedings of the VIII International Conference
on Hypernuclear and Strange Particle Physics, HYP03, revised version. 10
pages. Uses espcrc1.st
Strangeness nuclear physics: a critical review on selected topics
Selected topics in strangeness nuclear physics are critically reviewed. This
includes production, structure and weak decay of --Hypernuclei, the
nuclear interaction and the possible existence of bound
states in nuclei. Perspectives for future studies on these issues are also
outlined.Comment: 63 pages, 51 figures, accepted for publication on European Physical
Journal
Single and double coincidence nucleon spectra in the weak decay of Lambda hypernuclei
Recent progress has been experienced in the field of hypernuclear weak decay,
especially concerning the ratio of the neutron- to proton-induced Lambda
non-mesonic decay rates, G_n/G_p. Theoretical analyses of nucleon coincidence
data have been performed in a finite nucleus framework. They led to the
extraction of G_n/G_p values in agreement with pure theoretical estimates, thus
providing an evidence for the solution of a longstanding puzzle. Here we
present an alternative approach to the problem, based on a nuclear matter
formalism extended to finite nuclei via the local density approximation. The
work is motivated by the exigence to make the determination of G_n/G_p from
data less model dependent. One-meson-exchange potentials are used for
describing both the one- and two-nucleon induced decays, Lambda N -> n N and
Lambda N N -> n N N. For the latter, treated within a microscopic approach, the
channels Lambda n n -> n n n and Lambda p p -> n p p are included in addition
to the mode Lambda n p -> n n p already considered, in a phenomenological way,
in previous studies. The propagation of the final nucleons in the residual
nucleus is simulated by an intranuclear cascade code. We evaluate single and
double coincidence nucleon spectra for the non-mesonic decay of C-12-Lambda.
Through the comparison of our predictions with KEK coincidence data we
determine G_n/G_p=0.43 \pm 0.10 for this hypernucleus, confirming previous
finite nucleus analyses.Comment: 34 pages, 17 figure
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