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W. C. Haxton

Publications and source records attributed to W. C. Haxton.

At least 55 records · Page 3Linked to original sources
arXiv2011

A Long, Cold, Early r-process? Neutrino-induced Nucleosynthesis in He Shells Revisited

We revisit a neutrino-driven r-process mechanism in the He shell of a core-collapse supernova, finding that it could succeed in early stars of metallicity < solar/1000, at relatively low temperatures and neutron densities, producing A ~ 130 and 195 abundance peaks over ~ 10-20 s. The mechanism is sensitive to the neutrino emission model and to neutrino oscillations. We discuss the implications of an r-process that could alter interpretations of abundance data from metal-poor stars, and point out the need for further calculations that include effects of the supernova shock.

astro-ph.SR↗
arXiv2011

Cosmology and Fundamental Physics and their Laboratory Astrophysics Connections

The Decadal Survey of Astronomy and Astrophysics created five panels to identify the science themes that would define the field's research frontiers in the coming decade. I will describe the conclusions of one of these, the Panel on Cosmology and Fundamental Physics, and comment on their relevance to the discussions at this meeting of the NASA Laboratory Astrophysics community.

astro-ph.CO↗
arXiv2010

Solar fusion cross sections II: the pp chain and CNO cycles

We summarize and critically evaluate the available data on nuclear fusion cross sections important to energy generation in the Sun and other hydrogen-burning stars and to solar neutrino production. Recommended values and uncertainties are provided for key cross sections, and a recommended spectrum is given for 8B solar neutrinos. We also discuss opportunities for further increasing the precision of key rates, including new facilities, new experimental techniques, and improvements in theory. This review, which summarizes the conclusions of a workshop held at the Institute for Nuclear Theory, Seattle, in January 2009, is intended as a 10-year update and supplement to Reviews of Modern Physics 70 (1998) 1265.

nucl-ex↗
arXiv2009

CIPANP 2009: Closing Talk

CIPANP 2009 is the tenth meeting of this series. I look back at some of the key events of past meetings, comment on a few of the presentations of this meeting, and look foward to the next CIPANP gathering, when first data from the LHC will be in hand.

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arXiv2009

The Scientific Life Of John Bahcall

This article follows the scientific life of John Norris Bahcall, including his tenacious pursuit of the solar neutrino problem, his contributions to our understanding of galaxies, quasars, and their emissions, and his leadership of and advocacy for astronomy and astrophysics.

astro-ph.SR↗
arXiv2009

Fundamental Symmetries and Conservation Laws

I discuss recent progress in low-energy tests of symmetries and conservation laws, including parity nonconservation in atoms and nuclei, electric dipole moment tests of time-reversal invariance, beta-decay correlation studies, and decays violating separate (family) and total lepton number.

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arXiv2009

CN-Cycle Neutrinos and Solar Metalicity

We discuss the current Standard Solar Model conflict between helioseismology and photospheric abundances, a speculation that connects this anomaly to formation of the gaseous giant planets, and a possible neutrino measurement to directly test solar core metalicity.

astro-ph.SR↗
arXiv2008

CN Neutrinos and the Sun's Primordial Core Metalicity

I discuss the use of neutrinos from the CN cycle and pp chain to constrain the primordial solar core abundances of C and N at an interesting level of precision. A comparison of the Sun's deep interior and surface compositions would test a key assumption of the standard solar model (SSM), a homogeneous zero-age Sun. It would also provide a cross-check on recent photospheric abundance determinations that have altered the once excellent agreement between the SSM and helioseismology. Motivated by the discrepancy between convective-zone abundances and helioseismology, I discuss the possibility that a two-zone Sun could emerge from late-stage metal differentiation in the solar nebula connected with formation of the gaseous giant planets.

astro-ph↗
arXiv2008

Edward Teller and Nuclei: Along the Trail to the Neutrino

I discuss two of Edward Teller's contributions to nuclear physics, the introduction of the Gamow-Teller operator in beta decay and the formulation of the Goldhaber-Teller model for electric dipole transitions, in the context of efforts to understand the weak interaction and the nature of the neutrino.

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arXiv2008

Neutrino Astrophysics

I review the current status of neutrino astrophysics, including solar neutrinos; atmospheric neutrinos; neutrino mass and oscillations; supernova neutrinos; neutrino nucleosynthesis (Big Bang nucleosynthesis, the neutrino process, the r-process); neutrino cooling and red giants; and high energy neutrino astronomy.

nucl-th↗
arXiv2008

CN-Cycle Solar Neutrinos and Sun's Primordial Core Metalicity

We argue that it may be possible to exploit neutrinos from the CN cycle and pp chain to determine the primordial solar core abundances of C and N at an interesting level of precision. Such a measurement would allow a comparison of the Sun's deep interior composition with it surface, testing a key assumption of the standard solar model (SSM), a homogeneous zero-age Sun. It would also provide a cross-check on recent photospheric abundance determinations that have altered the once excellent agreement between the SSM and helioseismology. As further motivation, we discuss a speculative possibility in which photospheric abundance/helioseismology puzzle is connected with the solar-system metal differentiation that accompanied formation of the gaseous giant planets. The theoretical relationship between core C and N and the 13N and 15O solar neutrino fluxes can be made more precise (and more general) by making use of the Super-Kamiokande and SNO 8B neutrino capture rates, which calibrate the temperature of the solar core. The primordial C and N abundances can then be obtained from these neutrino fluxes and from a product of nuclear rates, with little residual solar model dependence. We describe some of the recent experimental advances that could allow this comparison to be made (theoretically) at about the 9% level, and note that this uncertainty may be reduced further due to ongoing work on the S-factor for 14N(p,gamma). The envisioned measurement might be possible in deep, large-volume detectors using organic scintillator, e.g., Borexino or SNO+

astro-ph↗
arXiv2007

The Form of the Effective Interaction in Harmonic-Oscillator-Based Effective Theory

I explore the form of the effective interaction in harmonic-oscillator-based effective theory (HOBET) in next-to-next-to-next-to-leading order (N3LO). As the included space in a HOBET (as in the shell model) is defined by the oscillator energy, both long-distance (low-momentum) and short-distance (high-momentum) degrees of freedom reside in the high-energy excluded space. A HOBET effective interaction is developed in which a short-range contact-gradient expansion is combined with an exact summation of the relative kinetic energy. By this means the very strong coupling of the included (P) and excluded (Q) spaces by the kinetic energy is removed. One finds that the interplay of QT and QV is governed by a single parameter kappa, the ratio of an observable, the binding energy |E|, to a parameter in the effective theory, the oscillator energy. Once the functional dependence on kappa is identified, the remaining order-by-order subtraction of the short-range physics residing in Q becomes systematic and rapidly converging. Numerical calculations are used to demonstrate how well the resulting expansion reproduces the running of Heff from high scales to a typical shell-model scale of 8 hbar omega. At N3LO various global properties of Heff are reproduced to a typical accuracy of 0.01%, or about 1 keV. The state-dependence of the effective interaction has been a troubling problem in nuclear physics, and is embodied in the energy dependence of Heff(|E|) in the Bloch-Horowitz formalism. It is shown that almost all of this state dependence is also extracted in the procedures followed here, isolated in the analytic dependence of Heff on kappa. Thus there exists a simple, Hermitian Heff that can be use in spectral calculations.

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arXiv2007

The Cascades Proposal for the Deep Underground Science and Engineering Laboratory

One of the options for creating a Deep Underground Science and Engineering Laboratory (DUSEL) is a site in the Mt. Stuart batholith, a granodiorite and tonalite rock mass in the Cascade mountain range in Washington State. The batholith's 100-year history in hard-rock tunneling includes the construction of the longest and deepest tunnels in the U.S., the parallel Cascade and Pioneer tunnels. The laboratory plan would utilize these two tunnels to produce a laboratory that has many desirable features, including dedicated, clean, horizontal access, container-module transport, and low operations costs. Various aspects of the site help to reduce geotechnical, environmental, and safety risks.

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arXiv2007

Atomic Electric Dipole Moments: The Schiff Theorem and Its Corrections

Searches for the permanent electric dipole moments (EDMs) of diamagnetic atoms provide powerful probes of CP-violating hadronic and semileptonic interactions. The theoretical interpretation of such experiments, however, requires careful implementation of a well-known theorem by Schiff that implies a vanishing net EDM for an atom built entirely from point-like, nonrelativistic constituents that interact only electrostatically. Any experimental observation of a nonzero atomic EDM would result from corrections to the point-like, nonrelativistic, electrostatic assumption. We reformulate Schiff's theorem at the operator level and delineate the electronic and nuclear operators whose atomic matrix elements generate corrections to "Schiff screening". We obtain a form for the operator responsible for the leading correction associated with finite nuclear size -- the so-called "Schiff moment" operator -- and observe that it differs from the corresponding operator used in previous Schiff moment computations. We show that the more general Schiff moment operator reduces to the previously employed operator only under certain approximations that are not generally justified. We also identify other corrections to Schiff screening that may not be included properly in previous theoretical treatments. We discuss practical considerations for obtaining a complete computation of corrections to Schiff screening in atomic EDM calculations.

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arXiv2006

Arguments for a "U.S. Kamioka": SNOLab and its Implications for North American Underground Science Planning

We argue for a cost-effective, long-term North American underground science strategy based on partnership with Canada and initial construction of a modest U.S. Stage I laboratory designed to complement SNOLab. We show, by reviewing the requirements of detectors now in the R&D phase, that SNOLab and a properly designed U.S. Stage I facility would be capable of meeting the needs of North America's next wave of underground experiments. We discuss one opportunity for creating a Stage I laboratory, the Pioneer tunnel in Washington State, a site that could be developed to provide dedicated, clean, horizontal access. This unused tunnel, part of the deepest (1040 m) tunnel system in the U.S., would allow the U.S. to establish, at low risk and low cost, a laboratory at a depth (2.12 km.w.e., or kilometers of water equivalent) quite similar to that of the Japanese laboratory Kamioka (2.04 km.w.e.). We describe studies of cosmic ray attenuation important to properly locating such a laboratory, and the tunnel improvements that would be required to produce an optimal Stage I facility. We also discuss possibilities for far-future Stage II (3.62 km.w.e.) and Stage III (5.00 km.w.e.) developments at the Pioneer tunnel, should future North American needs for deep space exceed that available at SNOLab.

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arXiv2006

Nuclear Astrophysics: CIPANP 2006

I review progress that has been made in nuclear astrophysics over the past few years and summarize some of the questions that remain. Topics selected include solar neutrinos, supernovae (the explosion and associated nucleosynthesis), laboratory astrophysics, and neutron star structure.

nucl-th↗