Astrophysical signatures of leptonium

Ellis, S. C.; Bland-Hawthorn, Joss

doi:10.1140/epjd/e2017-80488-7

Cited by 13 publications

(11 citation statements)

References 77 publications

(120 reference statements)

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“…Consistent annihilation flux, line width, and line centroid variations may point to known large-scale components of the Milky Way, such as the galactic bar (e.g. Wegg & Gerhard 2013;Ellis & Bland-Hawthorn 2018), or rather local features such as the local bubble (e.g. Lallement et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Constraints on positron annihilation kinematics in the inner Galaxy

Siegert

Crocker²,

Diehl

et al. 2019

A&A

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Context. The annihilation of cosmic positrons with electrons in the interstellar medium results in the strongest persistent γ-ray line signal in the sky. For the past 50 years, this 511 keV emission -predominantly from the galactic bulge region and from a low surfacebrightness disk -has puzzled observers and theoreticians. A key issue for understanding positron astrophysics is found in cosmic-ray propagation, especially at low kinetic energies ( 10 MeV). Aims. We want to shed light on how positrons propagate and the resulting morphology of the annihilation emission. We approach this "positron puzzle" by inferring kinematic information of the 511 keV line in the inner radian of the Galaxy. This constrains propagation scenarios and positron source populations in the Milky Way. Methods. By dissecting the positron annihilation emission as measured with INTEGRAL/SPI, we derive spectra for individual and independent regions in the sky. The centroid energies of these spectra around the 511 keV line are converted into Doppler-shifts, representing the line-of-sight velocity along different galactic longitudes. This results in a longitude-velocity diagram of positron annihilation. From high-resolution spectra, we also determine Doppler-broadening from γ-ray line shape parameters to study annihilation conditions as they vary with galactic longitude. Results. We find line-of-sight velocities in the 511 keV line that are consistent with zero, as well as with galactic rotation from CO measurements (2-3 km s −1 deg −1 ), and measurements of radioactive 26 Al (7.5-9.5 km s −1 deg −1 ). The velocity gradient in the inner ±30 • is determined to be 4 ± 6 km s −1 deg −1 . The width of the 511 keV line is constant as a function of longitude at 2.43 ± 0.14 keV, with possibly different values towards the disk. The positronium fraction is found to be 1.0 along the galactic plane. Conclusions. The weak signals in the disk leave open the question whether positron annihilation is associated with the high velocities seen in 26 Al or rather with ordinarily rotating components of the Milky Way's interstellar medium. We confirm previous results that positrons are slowed down to the 10 eV energy scale before annihilation, and constrain bulk Doppler-broadening contributions to 1.25 keV in the inner radian. Consequently, the true annihilation conditions remain unclear.

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Section: Introductionmentioning

confidence: 99%

Constraints on positron annihilation kinematics in the inner Galaxy

Siegert

Crocker²,

Diehl

et al. 2019

A&A

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“…[24,25] for recent progress). For the scalar and tensor currents, chiral effective field theories (EFTs) have also been used to organize multinucleon effects in nuclear MEs [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]. In contrast to arXiv:1712.03221v2 [hep-lat] 13 May 2018 2 the axial case, these effects are not well constrained by experiment, but could be determined by matching to abinitio Standard Model calculations of few-body matrix elements using lattice quantum chromodynamics (lattice QCD).…”

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confidence: 99%

Scalar, Axial, and Tensor Interactions of Light Nuclei from Lattice QCD

et al. 2018

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Complete flavor decompositions of the matrix elements of the scalar, axial, and tensor currents in the proton, deuteron, diproton, and ^{3}He at SU(3)-symmetric values of the quark masses corresponding to a pion mass m_{π}∼806 MeV are determined using lattice quantum chromodynamics. At the physical quark masses, the scalar interactions constrain mean-field models of nuclei and the low-energy interactions of nuclei with potential dark matter candidates. The axial and tensor interactions of nuclei constrain their spin content, integrated transversity, and the quark contributions to their electric dipole moments. External fields are used to directly access the quark-line connected matrix elements of quark bilinear operators, and a combination of stochastic estimation techniques is used to determine the disconnected sea-quark contributions. The calculated matrix elements differ from, and are typically smaller than, naive single-nucleon estimates. Given the particularly large, O(10%), size of nuclear effects in the scalar matrix elements, contributions from correlated multinucleon effects should be quantified in the analysis of dark matter direct-detection experiments using nuclear targets.

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“…It has long been known that positrons are produced in the Milky Way galaxy, through the detection of the 511 keV γ-rays produced as the positrons annihilate with ambient electrons [1,2,3]. The emission is concentrated towards the Galactic Center, but has wide extension in the bulge and (at lower intensity) along the plane of the Galaxy [3].…”

Section: Introductionmentioning

confidence: 99%

“…Alternatively, the positrons could arise from objects such as exploding stars (supernovae) or processes occurring near the Galactic Center Black Hole itself (with subsequent diffusion through the interstellar medium before annihilation). More exotic sources could include annihilating dark matter [3]. The main reason for this uncertainty is the coarse angular resolution (~2°) of the best available γ-ray observations.…”

Section: Introductionmentioning

confidence: 99%

Seeking celestial positronium with an OH-suppressed diffraction-limited spectrograph

Robertson

Ellis

et al. 2021

Appl. Opt.

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Celestially, Positronium (Ps), has only been observed through gamma-ray emission produced by its annihilation. However, in its triplet state, a Ps atom has a mean lifetime long enough for electronic transitions to occur between quantum states. This produces a recombination spectrum observable in principle at near IR wavelengths, where angular resolution greatly exceeding that of the gamma-ray observations is possible. However, the background in the NIR is dominated by extremely bright atmospheric hydroxyl (OH) emission lines. In this paper we present the design of a diffraction-limited spectroscopic system using novel photonic components -a photonic lantern, OH Fiber Bragg Grating filters, and a photonic TIGER 2-dimensional pseudo-slit -to observe the Ps Balmer alpha line at 1.3122 μm for the first time.

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Astrophysical signatures of leptonium

Cited by 13 publications

References 77 publications

Constraints on positron annihilation kinematics in the inner Galaxy

Constraints on positron annihilation kinematics in the inner Galaxy

Scalar, Axial, and Tensor Interactions of Light Nuclei from Lattice QCD

Seeking celestial positronium with an OH-suppressed diffraction-limited spectrograph

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