Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session Z10: Dark Matter Theory |
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Sponsoring Units: DAP Chair: Rakshya Khatiwada, Fermilab Room: Sheraton Governor's Square 12 |
Tuesday, April 16, 2019 3:30PM - 3:42PM |
Z10.00001: Sexaquark Dark Matter, the dark matter-baryon ratio, and solution to the 7Li problem via DM-baryon interactions Glennys R Farrar I will show how dark matter composed of sexaquarks (conjectured stable state composed of uuddss quarks) can account for two long-standing puzzles: 1) If DM is composed of sexaquarks (S) or more generally contains equal numbers of uds quarks, e.g. strangelets or PBHs composed of them or a mix, the observed 5.3 DM-to-baryon ratio is a practically parameter-free result of statistical physics at the end of the QGP phase. 2) If S or other DM has a sufficiently strong cross section for scattering on $A=7$ nuclei, Be7 (Li7) is broken up into He4 + He3 (H3) explaining the 10-sigma deficit of primordial Li7 without affecting the good predictions of BBN. Alternative mechanisms capable of this will be mentioned, time permitting. I will also show that recent objections to generic dibaryon dark matter based on SNe observations and claims that dibaryons are destroyed in the low temperature hadronic phase after the QGP phase transitions, do not apply to the sexaquark scenario. Due to the expected small size of the S, < 0.2 fm, its overlap with baryons is very small and the effective vertex for fusion or breakup is <~ 10^-6. |
Tuesday, April 16, 2019 3:42PM - 3:54PM |
Z10.00002: Interaction Between Dark Matter and Baryons: Non-Perturbative Effects, Experimental Bounds, and Solution to the 7Li Problem Xingchen Xu, Glennys R Farrar We propose a scenario of interaction between dark matter (DM) and baryons where non-perturbative effects and resonant scattering play a key role, which can result in cross section behavior that is very different from that found in traditional weakly-coupled models. We then test the compatibility of our model with direct detection experiments and other constraints, and discuss under what circumstances the 7Li problem may be solved in such scenario by breaking-up 7Be (7Li) through scattering with DM, thus reducing the predicted 7Li abundance to the observed value without affecting other successful predictions of BBN. An example of a DM candidate which can exhibit such non-perturbative effects is the sexaquark, a conjectured stable state composed of six quarks. |
Tuesday, April 16, 2019 3:54PM - 4:06PM |
Z10.00003: First direct astrophysical constraints on dark matter interactions at very low velocities Digvijay Wadekar, Glennys Farrar We derive the first direct constraints on millicharged DM cross sections at very low velocity, v ~ 7 km/s, by requiring that the heating/cooling due to DM interacting with gas in the Leo T dwarf galaxy not exceed the radiative cooling rate. We also use equilibrium heating/cooling constraints for durable Galactic molecular gas clouds to improve the constraints on sub-GeV DM cross sections for arbitrary velocity dependences. We correct erroneous results in the literature that were based on unsuitable clouds and analyses. Our results exclude the millicharge explanation for the reported EDGES 21 cm anomaly even when only 1% of DM is charged. |
Tuesday, April 16, 2019 4:06PM - 4:18PM |
Z10.00004: Effects of Relativistic Nonthermal Dark Matter on the Matter Power Spectrum Carisa A Miller, Adrienne L Erickcek The thermal production of dark matter during the radiation-dominated era is a simple and amply motivated theory. However, as the parameter space for particles that can fit this model continues to narrow, many compelling alternatives have been proposed. Notable among these modifications is a period of (effective) matter domination prior to the onset of radiation domination, which has interesting and observable consequences for structure growth. During this early matter-dominated era (EMDE), the Universe was dominated by massive particles or oscillating scalar fields that decayed into Standard Model (SM) particles, thus reheating the Universe after inflation. This decay process could also be the primary source of dark matter. In the absence of fine-tuning between the masses of the parent and daughter particles, both dark matter and SM particles would be born relativistic. We investigate the effects of the nonthermal production of dark matter particles with relativistic velocities on the matter power spectrum. We determine whether enhanced structure growth during the EMDE can be preserved and under what conditions lower limits on small-scale power obtained from the Lyman-alpha forest can be satisfied. |
Tuesday, April 16, 2019 4:18PM - 4:30PM |
Z10.00005: Dark matter halos in the multicomponent inelastic model. From dwarfs to galaxy clusters Keita Todoroki, Mikhail V. Medvedev A possibility of dark matter (DM) being multicomponent has a strong implication on resolving longstanding cosmological problems on small scale. The simplest two-component DM (2cDM) model with inelastic interactions has recently been shown to robustly resolve the missing satellites, core-cusp, and too-big-to-fail problems in N-body cosmological DM-only simulations tested on MW-like environments with DM halos of a virial mass ∼5×1011 Msun [1,2]. With the aim of further constraining the parameter space available for the 2cDM model, we extend our analysis to dwarf and galaxy cluster haloes with their virial mass of ∼107 Msun and ∼1015 Msun, respectively. We find that the normalized cross-sections σ/m≥0.1 cm2/g are disfavored for both dwarfs and galaxy cluster haloes, while σ/m≤0.001 cm2/g have too little effect on DM halos making them nearly indistinguishable from their CDM counterparts. We conclude that the 2cDM model can naturally resolve the above small-scale cosmological problems of DM halos across about eight orders of magnitude in their virial mass for the cross-sections σ/m∼0.1-0.001 cm2/g. [1,2] K. Todoroki, M.V. Medvedev, MNRAS, 483, 3983 (2019); MNRAS, 483, 4004 (2019) |
Tuesday, April 16, 2019 4:30PM - 4:42PM |
Z10.00006: Dwarf halos and ultralight dark matter model Mikhail V. Medvedev Ultralight bosons with de Broglie wavelength ~1 kpc have been proposed as a model of dark matter (DM) which can potentially evade some problems on small scales (core-cusp, substructure). Here we investigate a dwarf DM halo evolution in a tidal field of a host halo taking into account the DM quantum tunneling. This process reduces the dwarf halo mass by tunneling it into the host halo. We demonstrate that, for a halo of a particular mass, the process is very sensitive to the dwarf's radial position. We argue that the observed distribution of satellites around Milky Way and Andromeda can strongly constrain and even rule out the ultralight DM model. |
Tuesday, April 16, 2019 4:42PM - 4:54PM |
Z10.00007: Analyzing Boson Stars Using the Variational Method Lauren Street We use the variational method to analyze properties of gravitationally bound Bose Einstein condensates called boson stars which are potential candidates for dark matter. Using a set of qualitative and quantitative measures, we compare various ansatze found in the literature in order to determine the best fit solutions for a given regime or analysis. We then use the best fit ansatze found to further study these systems. Such studies include boson star decay rates and lifetimes, dense configurations, and both special and general relativistic corrections to the relevant equations of motion. We also analyze how multiple flavor dark matter theories can account for the galactic core density-radius scaling relation which can be found in the literature from observations of galactic profiles. Through these analyses we hope to gain insights into the viability of boson stars as possible candidates for dark matter and the possible parameter spaces in which these systems can be detected. |
Tuesday, April 16, 2019 4:54PM - 5:06PM |
Z10.00008: Charged dark matters, missing neutrinos, cosmic rays and extended standard model Jae-Kwang Hwang In the present work, the charged B1, B2 and B3 bastons with the condition of k(mm) = k >> k(dd) > k(dm) = k(lq) = 0 are explained as the good candidates of the dark matters. The proposed rest mass (26.12 eV/c2) of the B1 dark matter is indirectly confirmed from the supernova 1987A data. The missing neutrinos are newly explained by using the dark matters and lepton charge force. The neutrino excess anomaly of the MinibooNE data is explained by the B1 dark matter scattering within the Cherenkov detectors. And the rest masses of 1.4 TeV/c2 and 42.7 GeV/c2 are assigned to the Le particle and the B2 dark matter, respectively, from the cosmic ray observations. In the present work, the Q1 baryon decays are used to explain the anti-Helium cosmic ray events. Because of the graviton evaporation and photon confinement, the very small Coulomb’s constant (k(dd)) of 10x-54k and gravitation constant (GN(dd)) of 10xGN for the charged dark matters at the present time are proposed. The x value can have the positive, zero or negative value around zero. Therefore, Fc(mm) > Fg(dd) (?) Fg(mm) > Fg(dm) > Fc(dd) > Fc(dm) = Fc(lq) = 0 for the proton-like particle. [1] Jae-Kwang Hwang, Mod. Phys. Lett. A32, 1730023 (2017). |
Tuesday, April 16, 2019 5:06PM - 5:18PM |
Z10.00009: Spectral Properties of Self-Adjoint Extensions of an Unbounded Hamiltonian as a Model for Dark Interactions Michael A Maroun There is compelling evidence of massive dark matter around galactic structures. This observation poses difficulties for local detection of the matter, either due to extremely small mass or interaction that is very weak. As an analogy, one envisions the core of a galactic structure as the nucleus of an atom and the dark matter as being bound to the core like electrons. This model, if gravity were the only interaction, is known exactly as the Coulomb model for hydrogen-like atoms. The Hamiltonian can then be modified by a lowest order harmonic potential as an approximation for dark interactions. The resulting Hamiltonian is an unbounded linear operator-- one that is not even semi-bounded, meaning there is neither an upper nor a lower bound. This property is desirable for dark interactions at the galactic level because the upper bound, if it exists, is many times the excess of the average galactic radius. While, the non-existence of a lower bound implies room for as of yet undetected local particle structure. The resulting spectrum, if observable, will give a lowest order approximation to the dark interaction coupling. |
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