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Search Results: 1 - 10 of 200640 matches for " P Springer "
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Hyperon Decays in Chiral Perturbation Theory Revisited
R. P. Springer
Physics , 1995,
Abstract: The discrepancies found between S-wave and P-wave fits for hyperon decays are reinvestigated using the heavy baryon chiral Lagrangian formalism. The agreement is found to improve through the inclusion of previously omitted diagrams. The S-waves are unaffected by this, but the P-wave predictions are modified. A correlated fit to the chiral parameters is performed and the results discussed.
Using the decay \psi(4160) -> X(3872) \gamma\ to probe the molecular content of the X(3872)
Margaryan, Arman;Springer, Roxanne P
High Energy Physics - Phenomenology , 2013,
Abstract: The X(3872) has non-charmonium-like properties, such as decay processes that seem to violate isospin, and a mass that lies unexpectedly close to the neutral-D-plus-neutral-D-excited-state threshold. An EFT that includes both charmonium-like (short distance) and molecule-like (meson bound state) properties is used to analyze the X(3872) as it is produced in the decay of \psi(4160). This is a route that BESIII may be able to measure. We find that the correlation between the angular distribution of the outcoming photon (or X(3872)) and the polarization of the \psi(4160) source may be used to provide information on whether short-distance or long-distance effects dominate.
Heavy-Quark Symmetry and the Electromagnetic Decays of Excited Charmed Strange Mesons
Thomas Mehen,Roxanne P. Springer
Physics , 2004, DOI: 10.1103/PhysRevD.70.074014
Abstract: Heavy-hadron chiral perturbation theory (HH$\chi$PT) is applied to the decays of the even-parity charmed strange mesons, D_{s0}(2317) and D_{s1}(2460). Heavy-quark spin symmetry predicts the branching fractions for the three electromagnetic decays of these states to the ground states D_s and D_s^* in terms of a single parameter. The resulting predictions for two of the branching fractions are significantly higher than current upper limits from the CLEO experiment. Leading corrections to the branching ratios from chiral loop diagrams and spin-symmetry violating operators in the HH$\chi$PT Lagrangian can naturally account for this discrepancy. Finally the proposal that the D_{s0}(2317) (D_{s1}(2460)) is a hadronic bound state of a D (D^*) meson and a kaon is considered. Leading order predictions for electromagnetic branching ratios in this molecular scenario are in very poor agreement with existing data.
Kaon-Nucleon Couplings for Weak Decays of Hypernuclei
M. J. Savage,R. P. Springer
Physics , 1995, DOI: 10.1103/PhysRevC.54.2786
Abstract: We investigate the weak kaon-nucleon (NNK) S-wave and P-wave interactions using heavy baryon chiral perturbation theory. The leading 1-loop SU(3) breaking contributions to the $ppK$, $pnK$, and $nnK$ couplings are computed. We find that they suppress all NNK amplitudes by $30\%$ to $50\%$. The ratio of neutron-induced to proton-induced hypernuclear decay widths is sensitive to such reductions. It has been argued that the discrepancy between the predicted and observed P-wave amplitudes in $\Delta s=1$ hyperon decay results from an accidental cancellation between tree-level amplitudes, and is not a fundamental problem for chiral perturbation theory. Agreement between experimentally determined NNK P-wave amplitudes and our estimates would support this explanation.
Two parity violating asymmetries from $n p \to d γ$ in pionless effective field theories
Matthias R. Schindler,Roxanne P. Springer
Physics , 2009, DOI: 10.1016/j.nuclphysa.2010.06.002
Abstract: We consider parity-violating observables from the processes $\vec n p\to d \gamma$ and $ np \to d \overset {\circlearrowleft}{\gamma}$. We perform calculations using pionless effective field theory both with and without explicit dibaryon fields. After combining these results with ones we have already obtained on parity-violating asymmetries in $\vec NN$ scattering, experimental input would in principle allow the extraction of all five parameters occurring at leading order in the parity-violating Lagrangian.
Parity Violation in Effective Field Theory and the Deuteron Anapole Moment
Martin J. Savage,Roxanne P. Springer
Physics , 1998, DOI: 10.1016/S0375-9474(98)80013-4
Abstract: Effective field theory, including pions, provides a consistent and systematic description of nucleon-nucleon strong interactions up to center-of-mass momentum of order 300 MeV per nucleon. We describe the inclusion of hadronic parity violation into this effective field theory and find an analytic form for the deuteron anapole moment at leading order in the expansion.
The Weak $ΛΛK^0$ Interaction
Martin J. Savage,Roxanne P. Springer
Physics , 1997, DOI: 10.1103/PhysRevC.57.1478
Abstract: We calculate the leading contribution to the weak $\Lambda \Lambda K$ coupling in heavy baryon chiral perturbation theory, including the SU(3) breaking terms arising at one-loop. This coupling gives the leading one-boson exchange amplitude for the process $\Lambda\Lambda\to\Lambda n$ and is an important component in understanding the decay of $\Lambda\Lambda$-hypernuclei. We find the S-wave and P-wave amplitudes to be stable under one-loop corrections, but the associated errors become large. We discuss the theoretical errors and potential effects of higher order terms.
The Theory of Parity Violation in Few-Nucleon Systems
Matthias R. Schindler,Roxanne P. Springer
Physics , 2013, DOI: 10.1016/j.ppnp.2013.05.002
Abstract: We review recent progress in the theoretical description of hadronic parity violation in few-nucleon systems. After introducing the different methods that have been used to study parity-violating observables we discuss the available calculations for reactions with up to five nucleons. Particular emphasis is put on effective field theory calculations where they exist, but earlier and complementary approaches are also presented. We hope this review will serve as a guide for those who wish to know what calculations are available and what further calculations need to be completed before we can claim to have a comprehensive picture of parity violation in few nucleon systems.
$NNK$ and $ΛΛK$ Amplitudes in Chiral Perturbation Theory
Martin J. Savage,Roxanne P. Springer
Physics , 1997, DOI: 10.1016/S0375-9474(98)00290-5
Abstract: We explore the S-wave and P-wave amplitudes for $NNK$ and $\Lambda\Lambda K$ interactions using chiral perturbation theory to ${\cal O}(m_s\log m_s)$. In contrast to the large corrections found in P-wave amplitudes in the nonleptonic decay of octet baryons, the $NNK$ amplitudes receive only small corrections to their tree-level values. The uncertainty in the $\Lambda\Lambda K$ amplitudes is found to be large.
The Anapole Form Factor of the Deuteron
Martin J. Savage,Roxanne P. Springer
Physics , 1999, DOI: 10.1016/S0375-9474(00)00568-6
Abstract: We find the leading order result for the anapole form factor of the deuteron using effective field theory. The momentum dependence of the anapole form factor is different from that of the matrix element of the strange currents in the deuteron, which may provide a way for disentangling these two competing effects when analyzing parity violating electron-deuteron scattering experiments. We give closed form expressions for both the form factor and integrals often encountered in the NN effective field theory.
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