Nuclear Experiment·nucl-ex
8 papers—1 primary·7 cross-listed·reconstructed*
Magdalena Skurzok🇵🇱 · Oleksandr Rundel🇵🇱 · Aleksander Khreptak🇵🇱 · Paweł Moskal🇵🇱
In this report one of the methods used for the luminosity determination for the experiment performed by WASA Collaboration to search for 3He-eta mesic nuclei is presented. The method is based on the analysis of pd -> 3He eta process.
Mary Alberg🇺🇸 · Gerald A. Miller🇺🇸
The light-quark flavor dependence of the proton sea has been of great interest for many years because of its close connection with non-perturbative effects. One hypothesis is that this dependence arises from the pion cloud of the proton. We apply light cone perturbation theory and experimental constraints to a chiral Lagrangian to compute the relevant Fock-space components of the nucleon wave function with well-defined uncertainties. Existing experimental information regarding the light flavor sea is studied, and predictions for future experimental results are provided. Future experiments have the ability to rule out this hypothesis and have profound implications for understanding the nucleon-nucleon force.
The electric dipole moment is a very sensitive probe of CP violation beyond the standard model. Light nuclei are particularly interesting since the CP violation may be enhanced by nuclear many-body effects. In this proceeding, we present the current status of the theoretical evaluations of the electric dipole moment of light nuclei in the ab initio approach and in the cluster model. We add the preliminary result of the evaluation of the electric dipole moment of Li which is treated in a cluster model with a triton.
C. E. Fields · F. X. Timmes🇺🇸 · R. Farmer🇺🇸 · I. Petermann · William M. Wolf · S. M. Couch🇺🇸
We explore properties of core-collapse supernova progenitors with respect to the composite uncertainties in the thermonuclear reaction rates by coupling the reaction rate probability density functions provided by the STARLIB reaction rate library with stellar models. We evolve 1000 15 models from the pre main-sequence to core O-depletion at solar and subsolar metallicities for a total of 2000 Monte Carlo stellar models. For each stellar model, we independently and simultaneously sample 665 thermonuclear reaction rates and use them in a in situ reaction network that follows 127 isotopes from H to Zn. With this framework we survey the core mass, burning lifetime, composition, and structural properties at five different evolutionary epochs. At each epoch we measure the probability distribution function of the variations of each property and calculate Spearman Rank-Order Correlation coefficients for each sampled reaction rate to identify which reaction rate has the largest impact on the variations on each property. We find that uncertainties in NO, triple-, CO, C(C,)Na, C(O,)Al, O(O,)S, O(O,)P, and O(O,)Si reaction rates dominate the variations of the properties surveyed. We find that variations induced by uncertainties in nuclear reaction rates grow with each passing phase of evolution, and at core H-, He-depletion are of comparable magnitude to the variations induced by choices of mass resolution and network resolution. However, at core C-, Ne-, and O-depletion, the reaction rate uncertainties can dominate the variation causing uncertainty in various properties of the stellar model in the evolution towards iron core-collapse.
Takayasu Sekihara (JAEA, Ibaraki)🇯🇵 · Hiroyuki Fujioka (Kyoto U.)🇯🇵 · Takatsugu Ishikawa (ELPH, Tohoku Univ.)🇯🇵
We theoretically investigate a possibility of an bound state and its formation in the reaction. First, in the fixed center approximation to the Faddeev equations we obtain an bound state with a binding energy of 25 MeV and width of 19 MeV, where we take the interaction with a coupling to the channel from the linear model. Then, in order to investigate the feasibility from an experimental point of view, we calculate the cross section of the reaction at the photon energy in the laboratory frame around 1.2 GeV. As a result, we find a clear peak structure with the strength 0.2 nb/sr, corresponding to a signal of the bound state in case of backward emission. This structure will be prominent because a background contribution coming from single-step emission off a bound nucleon is highly suppressed. In addition, the signal can be seen even in case of forward emission as a bump or dip, depending on the relative phase between the bound-state formation and the single-step background.
B. Wojtsekhowski🇺🇸 · G. Niculescu🇺🇸
We propose to build a shielded magnet that will act as an untagged bremsstrahlung photon source suitable for deployment in Hall A/C at Jefferson Lab. The goal of the project is a compact source which provides a narrow 1-mm diameter photon beam at the target with the intensity adequate to the polarized target operation. The proposed solution is based on the absorption of the electron beam in the magnet. The compactness is achieved by means of a shallow channel which leads to an electromagnetic shower in the Cu-W body of the channel and surrounding material after a 1-2~mm deflection of the beam electrons by a horizontal magnetic field. This source will allow us to achieve ten times the luminosity of the mixed electron--photon beam configuration while keeping the heat load on the (polarized) target as well as the radiation level in the experimental hall at acceptable levels. The concept for this device was developed for the experimental proposal PR12-15-003 but, if built, it would become a general--purpose source that would be usable for a variety of photon--induced reactions of interest in the 12-GeV era.
A. Saleev🇩🇪 · N. N. Nikolaev🇷🇺 · F. Rathmann🇩🇪 · F. Hinder🇩🇪 · J. Pretz🇩🇪 · M. Rosenthal🇩🇪
Precision experiments, such as the search for electric dipole moments of charged particles using radiofrequency spin rotators in storage rings, demand for maintaining the exact spin resonance condition for several thousand seconds. Synchrotron oscillations in the stored beam modulate the spin tune of off-central particles, moving it off the perfect resonance condition set for central particles on the reference orbit. Here we report an analytic description of how synchrotron oscillations lead to non-exponential decoherence of the radiofrequency resonance driven up-down spin rotations. This non-exponential decoherence is shown to be accompanied by a nontrivial walk of the spin phase. We also comment on sensitivity of the decoherence rate to the harmonics of the radiofreqency spin rotator and a possibility to check predictions of decoherence-free magic energies.
Tomoya Naito🇯🇵 · Ryosuke Akashi · Haozhao Liang🇯🇵
We test the Coulomb exchange and correlation energy density functionals of electron systems for atomic nuclei in the local density approximation (LDA) and the generalized gradient approximation (GGA). For the exchange Coulomb energies, it is found that the deviation between the LDA and GGA ranges from around in to around in , by taking the Perdew-Burke-Ernzerhof (PBE) functional as an example of the GGA\@. For the correlation Coulomb energies, it is shown that those functionals of electron systems are not suitable for atomic nuclei.
* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.