Lisa Goodenough | Argonne National Laboratory (original) (raw)

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Papers by Lisa Goodenough

Physics Letters B, 2011

We analyze the first two years of data from the Fermi Gamma Ray Space Telescope from the directio... more We analyze the first two years of data from the Fermi Gamma Ray Space Telescope from the direction of the inner 10° around the Galactic Center with the intention of constraining, or finding evidence of, annihilating dark matter. We find that the morphology and spectrum of ...

Physical Review D, 2007

... This allows us to consider an average of spectral information over a range of angles. We focu... more ... This allows us to consider an average of spectral information over a range of angles. We focus on the 22 and 33 GHz bands, as they are considerably less noisy and are more robust to theforeground subtraction method than the higher frequency channels. ...

We study the gamma rays observed by the Fermi Gamma Ray Space Telescope from the direction of the... more We study the gamma rays observed by the Fermi Gamma Ray Space Telescope from the direction of the Galactic Center and find that their angular distribution and energy spectrum are well described by a dark matter annihilation scenario. In particular, we find a good fit to the data for dark matter particles with a 25-30 GeV mass, an annihilation cross section of ∼ 9 × 10 −26 cm 3 /s, and that are distributed with a cusped halo profile, ρ(r) ∝ r −1.1 , within the inner kiloparsec of the Galaxy. We cannot, however, exclude the possibility that these photons originate from an astrophysical source or sources with a similar morphology and spectral shape to those predicted in an annihilating dark matter scenario.

Physical Review D, 2009

Recent preliminary results from the PAMELA experiment indicate the presence of an excess of cosmi... more Recent preliminary results from the PAMELA experiment indicate the presence of an excess of cosmic ray positrons above 10 GeV. In this letter, we consider possibility that this signal is the result of dark matter annihilations taking place in the halo of the Milky Way. Rather than focusing on a specific particle physics model, we take a phenomenological approach and consider a variety of masses and two-body annihilation modes, including W + W − , Z 0 Z 0 , bb, τ + τ − , µ + µ − , and e + e − . We also consider a range of diffusion parameters consistent with current cosmic ray data. We find that a significant upturn in the positron fraction above 10 GeV is compatible with a wide range of dark matter annihilation modes, although very large annihilation cross sections and/or boost factors arising from inhomogeneities in the local dark matter distribution are required to produce the observed intensity of the signal. We comment on constraints from gamma rays, synchrotron emission, and cosmic ray antiproton measurements. PACS numbers: 95.35.+d; 98.70.Sa; 96.50.S; 95.55.Vj

Physical Review D, 2009

We consider the signals of positrons and electrons from "exciting" dark matter (XDM) annihilation... more We consider the signals of positrons and electrons from "exciting" dark matter (XDM) annihilation. Because of the light (m φ < ∼ 1 GeV) force carrier φ into which the dark matter states can annihilate, the electrons and positrons are generally very boosted, yielding a hard spectrum, in addition to the low energy positrons needed for INTEGRAL observations of the galactic center. We consider the relevance of this scenario for HEAT, PAMELA and the WMAP "haze," focusing on light (m φ < ∼ 2mπ) φ bosons, and find that significant signals can be found for all three, although significant signals generally require high dark matter densities. We find that measurements of the positron fraction are generally insensitive to the halo model, but do suffer significant astrophysical uncertainties. We discuss the implications for upcoming PAMELA results.

Physical Review D, 2009

Multiple lines of evidence indicate an anomalous injection of high-energy e + e − in the Galactic... more Multiple lines of evidence indicate an anomalous injection of high-energy e + e − in the Galactic halo. The recent e + fraction spectrum from the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) shows a sharp rise up to 100 GeV. The Fermi Gamma-ray Space Telescope has found a significant hardening of the e + e − cosmic ray spectrum above 100 GeV, with a break, confirmed by HESS at around 1 TeV. The Advanced Thin Ionization Calorimeter (ATIC) has also detected detected a similar excess, falling back to the expected spectrum at 1 TeV and above. Excess microwaves towards the galactic center in the WMAP data are consistent with hard synchrotron radiation from a population of 10-100 GeV e + e − (the WMAP "Haze"). We argue that dark matter annihilations can provide a consistent explanation of all of these data, focusing on dominantly leptonic modes, either directly or through a new light boson. Normalizing the signal to the highest energy evidence (Fermi and HESS), we find that similar cross sections provide good fits to PAMELA and the Haze, and that both the required cross section and annihilation modes are achievable in models with Sommerfeld-enhanced annihilation. These models naturally predict significant production of gamma rays in the galactic center via a variety of mechanisms.

Physical Review D, 2011

As very high energy ( > ∼ 100 GeV) gamma rays travel over cosmological distances, their flux is a... more As very high energy ( > ∼ 100 GeV) gamma rays travel over cosmological distances, their flux is attenuated through interactions with the extragalactic background light. Observations of distant gamma ray sources at energies between ∼200 GeV and a few TeV by ground-based gamma-ray telescopes such as HESS, however, have motivated the possibility that the universe is more transparent to very high energy photons than had been anticipated. One proposed explanation for this is the existence of axion-like-particles (ALPs) which gamma rays can efficiently oscillate into, enabling them to travel cosmological distances without attenuation. In this article, we use a state-of-the-art model for the extragalactic background light (which is somewhat lower at ∼ µm wavelengths than in previous models) and data from the Fermi Gamma Ray Space Telescope to calculate the spectra at 1-100 GeV of two gamma-ray sources, 1ES1101-232 at redshift z = 0.186 and H2356-309 at z = 0.165, in conjunction with the measurements of ground-based telescopes, to test the ALP hypothesis. We find that these observations can be well-fit by an intrinsic power-law source spectrum with indices of -1.72 and -2.1 for 1ES1101-232 and H2356-309, respectively, and that no ALPs or other exotic physics is necessary to explain the observed degree of attenuation. While this does not exclude the possibility that ALPs are involved in the cosmological propagation of gamma rays, it does reduce the motivation for such new physics. PACS numbers: 95.85.Pw, 98.70.Vc 98.70.Rz 14.80.Mz

Journal of Cosmology and Astroparticle Physics, 2010

Journal of Cosmology and Astroparticle Physics, 2009

Recently published results from the PAMELA experiment have shown conclusive evidence for an exces... more Recently published results from the PAMELA experiment have shown conclusive evidence for an excess of positrons at high (∼ 10 − 100 GeV) energies, confirming earlier indications from HEAT and AMS-01. Such a signal is generally expected from dark matter annihilations. However, the hard positron spectrum and large amplitude are difficult to achieve in most conventional WIMP models. The absence of any associated excess in anti-protons is highly constraining on models with hadronic annihilation modes. We revisit an earlier proposal, wherein the dark matter annihilates into a new light ( < ∼ GeV) boson φ, which is kinematically constrained to go to hard leptonic states, without anti-protons or π 0 's. We find this provides a very good fit to the data. The light boson naturally provides a mechanism by which large cross sections can be achieved through the Sommerfeld enhancement, as was recently proposed. Depending on the mass of the WIMP, the rise may continue above 300 GeV, the extent of PAMELA's ability to discriminate between electrons and positrons.

Journal of Cosmology and Astroparticle Physics, 2011

Anomalies in direct and indirect detection have motivated models of dark matter consisting of a m... more Anomalies in direct and indirect detection have motivated models of dark matter consisting of a multiplet of nearly-degenerate states, coupled by a new GeV-scale interaction. We perform a careful analysis of the thermal freezeout of dark matter annihilation in such a scenario. We compute the range of "boost factors" arising from Sommerfeld enhancement in the local halo for models which produce the correct relic density, and show the effect of including constraints on the saturated enhancement from the cosmic microwave background (CMB). We find that boost factors from Sommerfeld enhancement of up to ∼ 800 are possible in the local halo. When the CMB bounds on the saturated enhancement are applied, the maximal boost factor is reduced to ∼ 400 for 1-2 TeV dark matter and sub-GeV force carriers, but remains large enough to explain the observed Fermi and PAMELA electronic signals. We describe regions in the DM mass-boost factor plane where the cosmic ray data is well fit for a range of final states, and show that Sommerfeld enhancement alone is enough to provide the large annihilation cross sections required to fit the data, although for light mediator masses (m φ < ∼ 200 MeV) there is tension with the CMB constraints in the absence of astrophysical boost factors from substructure. Additionally, we consider the circumstances under which WIMPonium formation is relevant and find for heavy WIMPs ( > ∼ 2 TeV) and soft-spectrum annihilation channels it can be an important consideration; we find regions with mχ > ∼ 2.8 TeV that are consistent with the CMB bounds with O(600-700) present-day boost factors.

Physics Letters B, 2011

We analyze the first two years of data from the Fermi Gamma Ray Space Telescope from the directio... more We analyze the first two years of data from the Fermi Gamma Ray Space Telescope from the direction of the inner 10° around the Galactic Center with the intention of constraining, or finding evidence of, annihilating dark matter. We find that the morphology and spectrum of ...

Physical Review D, 2007

... This allows us to consider an average of spectral information over a range of angles. We focu... more ... This allows us to consider an average of spectral information over a range of angles. We focus on the 22 and 33 GHz bands, as they are considerably less noisy and are more robust to theforeground subtraction method than the higher frequency channels. ...

We study the gamma rays observed by the Fermi Gamma Ray Space Telescope from the direction of the... more We study the gamma rays observed by the Fermi Gamma Ray Space Telescope from the direction of the Galactic Center and find that their angular distribution and energy spectrum are well described by a dark matter annihilation scenario. In particular, we find a good fit to the data for dark matter particles with a 25-30 GeV mass, an annihilation cross section of ∼ 9 × 10 −26 cm 3 /s, and that are distributed with a cusped halo profile, ρ(r) ∝ r −1.1 , within the inner kiloparsec of the Galaxy. We cannot, however, exclude the possibility that these photons originate from an astrophysical source or sources with a similar morphology and spectral shape to those predicted in an annihilating dark matter scenario.

Physical Review D, 2009

Recent preliminary results from the PAMELA experiment indicate the presence of an excess of cosmi... more Recent preliminary results from the PAMELA experiment indicate the presence of an excess of cosmic ray positrons above 10 GeV. In this letter, we consider possibility that this signal is the result of dark matter annihilations taking place in the halo of the Milky Way. Rather than focusing on a specific particle physics model, we take a phenomenological approach and consider a variety of masses and two-body annihilation modes, including W + W − , Z 0 Z 0 , bb, τ + τ − , µ + µ − , and e + e − . We also consider a range of diffusion parameters consistent with current cosmic ray data. We find that a significant upturn in the positron fraction above 10 GeV is compatible with a wide range of dark matter annihilation modes, although very large annihilation cross sections and/or boost factors arising from inhomogeneities in the local dark matter distribution are required to produce the observed intensity of the signal. We comment on constraints from gamma rays, synchrotron emission, and cosmic ray antiproton measurements. PACS numbers: 95.35.+d; 98.70.Sa; 96.50.S; 95.55.Vj

Physical Review D, 2009

We consider the signals of positrons and electrons from "exciting" dark matter (XDM) annihilation... more We consider the signals of positrons and electrons from "exciting" dark matter (XDM) annihilation. Because of the light (m φ < ∼ 1 GeV) force carrier φ into which the dark matter states can annihilate, the electrons and positrons are generally very boosted, yielding a hard spectrum, in addition to the low energy positrons needed for INTEGRAL observations of the galactic center. We consider the relevance of this scenario for HEAT, PAMELA and the WMAP "haze," focusing on light (m φ < ∼ 2mπ) φ bosons, and find that significant signals can be found for all three, although significant signals generally require high dark matter densities. We find that measurements of the positron fraction are generally insensitive to the halo model, but do suffer significant astrophysical uncertainties. We discuss the implications for upcoming PAMELA results.

Physical Review D, 2009

Multiple lines of evidence indicate an anomalous injection of high-energy e + e − in the Galactic... more Multiple lines of evidence indicate an anomalous injection of high-energy e + e − in the Galactic halo. The recent e + fraction spectrum from the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) shows a sharp rise up to 100 GeV. The Fermi Gamma-ray Space Telescope has found a significant hardening of the e + e − cosmic ray spectrum above 100 GeV, with a break, confirmed by HESS at around 1 TeV. The Advanced Thin Ionization Calorimeter (ATIC) has also detected detected a similar excess, falling back to the expected spectrum at 1 TeV and above. Excess microwaves towards the galactic center in the WMAP data are consistent with hard synchrotron radiation from a population of 10-100 GeV e + e − (the WMAP "Haze"). We argue that dark matter annihilations can provide a consistent explanation of all of these data, focusing on dominantly leptonic modes, either directly or through a new light boson. Normalizing the signal to the highest energy evidence (Fermi and HESS), we find that similar cross sections provide good fits to PAMELA and the Haze, and that both the required cross section and annihilation modes are achievable in models with Sommerfeld-enhanced annihilation. These models naturally predict significant production of gamma rays in the galactic center via a variety of mechanisms.

Physical Review D, 2011

As very high energy ( > ∼ 100 GeV) gamma rays travel over cosmological distances, their flux is a... more As very high energy ( > ∼ 100 GeV) gamma rays travel over cosmological distances, their flux is attenuated through interactions with the extragalactic background light. Observations of distant gamma ray sources at energies between ∼200 GeV and a few TeV by ground-based gamma-ray telescopes such as HESS, however, have motivated the possibility that the universe is more transparent to very high energy photons than had been anticipated. One proposed explanation for this is the existence of axion-like-particles (ALPs) which gamma rays can efficiently oscillate into, enabling them to travel cosmological distances without attenuation. In this article, we use a state-of-the-art model for the extragalactic background light (which is somewhat lower at ∼ µm wavelengths than in previous models) and data from the Fermi Gamma Ray Space Telescope to calculate the spectra at 1-100 GeV of two gamma-ray sources, 1ES1101-232 at redshift z = 0.186 and H2356-309 at z = 0.165, in conjunction with the measurements of ground-based telescopes, to test the ALP hypothesis. We find that these observations can be well-fit by an intrinsic power-law source spectrum with indices of -1.72 and -2.1 for 1ES1101-232 and H2356-309, respectively, and that no ALPs or other exotic physics is necessary to explain the observed degree of attenuation. While this does not exclude the possibility that ALPs are involved in the cosmological propagation of gamma rays, it does reduce the motivation for such new physics. PACS numbers: 95.85.Pw, 98.70.Vc 98.70.Rz 14.80.Mz

Journal of Cosmology and Astroparticle Physics, 2010

Journal of Cosmology and Astroparticle Physics, 2009

Recently published results from the PAMELA experiment have shown conclusive evidence for an exces... more Recently published results from the PAMELA experiment have shown conclusive evidence for an excess of positrons at high (∼ 10 − 100 GeV) energies, confirming earlier indications from HEAT and AMS-01. Such a signal is generally expected from dark matter annihilations. However, the hard positron spectrum and large amplitude are difficult to achieve in most conventional WIMP models. The absence of any associated excess in anti-protons is highly constraining on models with hadronic annihilation modes. We revisit an earlier proposal, wherein the dark matter annihilates into a new light ( < ∼ GeV) boson φ, which is kinematically constrained to go to hard leptonic states, without anti-protons or π 0 's. We find this provides a very good fit to the data. The light boson naturally provides a mechanism by which large cross sections can be achieved through the Sommerfeld enhancement, as was recently proposed. Depending on the mass of the WIMP, the rise may continue above 300 GeV, the extent of PAMELA's ability to discriminate between electrons and positrons.

Journal of Cosmology and Astroparticle Physics, 2011

Anomalies in direct and indirect detection have motivated models of dark matter consisting of a m... more Anomalies in direct and indirect detection have motivated models of dark matter consisting of a multiplet of nearly-degenerate states, coupled by a new GeV-scale interaction. We perform a careful analysis of the thermal freezeout of dark matter annihilation in such a scenario. We compute the range of "boost factors" arising from Sommerfeld enhancement in the local halo for models which produce the correct relic density, and show the effect of including constraints on the saturated enhancement from the cosmic microwave background (CMB). We find that boost factors from Sommerfeld enhancement of up to ∼ 800 are possible in the local halo. When the CMB bounds on the saturated enhancement are applied, the maximal boost factor is reduced to ∼ 400 for 1-2 TeV dark matter and sub-GeV force carriers, but remains large enough to explain the observed Fermi and PAMELA electronic signals. We describe regions in the DM mass-boost factor plane where the cosmic ray data is well fit for a range of final states, and show that Sommerfeld enhancement alone is enough to provide the large annihilation cross sections required to fit the data, although for light mediator masses (m φ < ∼ 200 MeV) there is tension with the CMB constraints in the absence of astrophysical boost factors from substructure. Additionally, we consider the circumstances under which WIMPonium formation is relevant and find for heavy WIMPs ( > ∼ 2 TeV) and soft-spectrum annihilation channels it can be an important consideration; we find regions with mχ > ∼ 2.8 TeV that are consistent with the CMB bounds with O(600-700) present-day boost factors.