160 research outputs found

    Second T = 3/2 state in 9^9B and the isobaric multiplet mass equation

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    Recent high-precision mass measurements and shell model calculations~[Phys. Rev. Lett. {\bf 108}, 212501 (2012)] have challenged a longstanding explanation for the requirement of a cubic isobaric multiplet mass equation for the lowest A=9A = 9 isospin quartet. The conclusions relied upon the choice of the excitation energy for the second T=3/2T = 3/2 state in 9^9B, which had two conflicting measurements prior to this work. We remeasured the energy of the state using the 9Be(3He,t)^9{\rm Be}(^3{\rm He},t) reaction and significantly disagree with the most recent measurement. Our result supports the contention that continuum coupling in the most proton-rich member of the quartet is not the predominant reason for the large cubic term required for A=9A = 9 nuclei

    The relationship between adverse neighborhood socioeconomic context and HIV continuum of care outcomes in a diverse HIV clinic cohort in the Southern United States

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    Retention in care and viral suppression are critical to delaying HIV progression and reducing transmission. Neighborhood socioeconomic context (NSEC) may affect HIV care receipt. We therefore assessed NSEC's impact on retention and viral suppression in a diverse HIV clinical cohort. HIV-positive adults with ≥1 visit at the Vanderbilt Comprehensive Care Clinic and 5-digit ZIP code tabulation area (ZCTA) information between 2008 and 2012 contributed. NSEC z-score indices used neighborhood-level socioeconomic indicators for poverty, education, labor-force participation, proportion of males, median age, and proportion of residents of black race by ZCTA. Retention was defined as ≥2 HIV care visits per calendar year, >90 days apart. Viral suppression was defined as an HIV-1 RNA <200 copies/mL at last measurement per calendar year. Modified Poisson regression was used to estimate risk ratios (RR) and 95% confidence intervals (CI). Among 2272 and 2541 adults included for retention and viral suppression analyses, respectively, median age and CD4 count at enrollment were approximately 38 (1st and 3rd quartile: 30, 44) years and 351 (176, 540) cells/μL, respectively, while 24% were female, and 39% were black. Across 243 ZCTAs, median NSEC z-score was 0.09 (-0.66, 0.48). Overall, 79% of person-time contributed was retained and 74% was virally suppressed. In adjusted models, NSEC was not associated with retention, though being in the 4th vs. 1st NSEC quartile was associated with lack of viral suppression (RR = 0.88; 95% CI: 0.80-0.97). Residing in the most adverse NSEC was associated with lack of viral suppression. Future studies are needed to confirm this finding

    Study of proton-unbound states in 24Al^{24}{\rm Al} relevant for the 23Mg(p,γ)^{23}{\rm Mg}(p,\gamma) reaction in novae

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    Background: The nucleosynthesis of several proton-rich nuclei is determined by radiative proton-capture reactions on unstable nuclei in nova explosions. One such reaction is 23Mg(p,γ)24Al^{23}{\rm Mg}(p,\gamma)^{24}{\rm Al}, which links the NeNa and MgAl cycles in oxygen-neon (ONe) novae. Purpose: To extract 23Mg(p,γ)24Al^{23}{\rm Mg}(p,\gamma)^{24}{\rm Al} resonance strengths from a study of proton-unbound states in 24Al^{24}{\rm Al}, produced via the 24^{24}Mg(3^{3}He,tt) reaction. Methods: A beam of 3He2+^3 {\rm He}^{2+} ions at 50.7 MeV was used to produce the states of interest in 24^{24}Al. Proton-triton angular correlations were measured with a K=600K=600 QDD magnetic spectrometer and a silicon detector array, located at iThemba LABS, South Africa. Results: We measured the excitation energies of the four lowest proton-unbound states in 24^{24}Al and place lower-limits on Γp/Γ\Gamma_p/\Gamma values for these four states. Together with USD-C shell-model calculations of partial gamma widths, the experimental data are also used to determine resonance strengths for the three lowest 23Mg(p,γ)24Al^{23}{\rm Mg}(p,\gamma)^{24}{\rm Al} resonances. Conclusions: The energy of the dominant first 23Mg(p,γ)^{23}{\rm Mg}(p,\gamma) resonance is determined to be Er=481.4±1.1E_{r} = 481.4 \pm 1.1 keV, with a resonance strength ωγ=18±6\omega \gamma = 18 \pm 6 meV

    138Ba(d,α)^{138}{\rm Ba}(d,\alpha) study of states in 136Cs^{136}{\rm Cs}: Implications for new physics searches with xenon detectors

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    We used the 138^{138}Ba(d,α)(d,\alpha) reaction to carry out an in-depth study of states in 136^{136}Cs, up to around 2.5~MeV. In this work, we place emphasis on hitherto unobserved states below the first 1+1^+ level, which are important in the context of solar neutrino and fermionic dark matter (FDM) detection in large-scale xenon experiments. We identify for the first time candidate metastable states in 136^{136}Cs, which would allow a real-time detection of solar neutrino and FDM events in xenon detectors, with high background suppression. Our results are also compared with shell-model calculations performed with three Hamiltonians that were previously used to evaluate the nuclear matrix element (NME) for 136^{136}Xe neutrinoless double beta decay. We find that one of these Hamiltonians, which also systematically underestimates the NME compared to the others, dramatically fails to describe the observed low-energy 136^{136}Cs spectrum, while the other two show reasonably good agreement

    138Ba(d,alpha) Study of States in 136Cs: Implications for New Physics Searches with Xenon Detectors

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    We used the 138Ba⁢( , ) reaction to carry out an in-depth study of states in 136Cs, up to around 2.5 MeV. In this Letter, we place emphasis on hitherto unobserved states below the first 1+ level, which are important in the context of solar neutrino and fermionic dark matter (FDM) detection in large-scale xenon-based experiments. We identify for the first time candidate metastable states in 136Cs, which would allow a real-time detection of solar neutrino and FDM events in xenon detectors, with high background suppression. Our results are also compared with shell-model calculations performed with three Hamiltonians that were previously used to evaluate the nuclear matrix element (NME) for 136Xe neutrinoless double beta decay. We find that one of these Hamiltonians, which also systematically underestimates the NME compared with the others, dramatically fails to describe the observed low-energy 136Cs spectrum, while the other two show reasonably good agreement
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