To review and discuss the status and future of the searches for dark sector states, their implications for the mystery of Dark Matter, and new associated theoretical developments.
Topics or Session Information:
I will discuss the direct detection of dark matter (DM) with polar materials, where single production of optical or acoustic phonons gives excellent reach to scattering of sub-MeV DM for both scalar and vector mediators. Using Density Functional Theory (DFT), we calculate the material-specific matrix elements, focusing on GaAs and sapphire, and show that DM scattering in an anisotropic crystal such as sapphire features a strong directional dependence. For example, for a DM candidate with mass 40 keV and relic abundance set by freeze-in, the daily modulation in the interaction rate can be established at 90\% C.L. with a gram-year of exposure. Non-thermal dark photon DM in the meV - eV mass range can also be effectively absorbed in polar materials.
We have understood robustly that the overwhelming majority of matter throughout our galaxy and the universe is something other than what we are made of. We remain profoundly ignorant of what it is. In this talk, Neal Weiner will describe the range of ideas that have arisen as to what this mysterious stuff might be, where it came from, and how to look for it. He will detail the progress made in the search to understand the nature of dark matter, and what questions this era hopes to answer, including perhaps the central one: what does the dark universe have to do with the one we can see?
Refreshments will follow (courtesy of BSA). All are invited to attend. This lecture is open to the public. Visitors 16 and older must carry a photo ID while at BNL.
I will review limits on dark matter and dark sectors from indirect searches, with a particular emphasis on what we can learn from probes of the early universe. I will discuss the recent claim of a primordial 21cm absorption signal by the EDGES experiment, and its possible implications for dark-sector physics.
Gravity provides both the evidence for dark matter and all of our present knowledge about its properties. By understanding the detailed structure of gravitationally bound objects in our Universe, we can probe the particle physics of dark matter in a way that is completely orthogonal to the Earth-based high-energy physics searches for dark matter. Such efforts will require close collaboration between astronomers and particle physicists, but have a great deal of potential in the near future. I will describe a useful parameter space to make connections between the two fields, and areas of potential advance.
The LIGO detection of gravitational waves has opened a new window on the universe. I will discuss how the process of superradiance, combined with gravitational wave measurements, makes black holes into nature's laboratories to search for new light bosons, from axions to dark photons. When a bosonic particle's Compton wavelength is comparable to the horizon size of a black hole, superradiance of these bosons into `hydrogenic' bound states extracts energy and angular momentum from the black hole. The occupation number of the levels grows exponentially and the black hole spins down. One candidate for such an ultralight boson is the QCD axion with decay constant above the GUT scale. Current black hole spin measurements disfavor a factor of 30 (400) in axion (vector) mass; future measurements can provide evidence of a new boson. Particles transitioning between levels and annihilating to gravitons may produce thousands of monochromatic gravitational wave signals, and turn LIGO into a particle detector.
We propose using interferometry of circularly polarized light as a mechanism by which to test for axion dark matter. These interferometers differ from standard interferometers only by the addition of a few quarter waveplates to preserve the polarization of light upon reflection. We show that using current technology, interferometers can probe new regions of axion parameter space up to a couple orders of magnitude beyond current constraints.
I will argue that axion dark matter may be detectable through narrow radio lines emitted from neutron stars. Neutron star magnetospheres host both a strong magnetic field and a plasma frequency that increases towards the neutron star surface. As the axions pass through the magnetosphere, they can resonantly convert into radio photons when the plasma frequency matches the axion mass, making the radio photon signal an analogue of indirect detection for axions. I will show sensitivity projection from a proposal recently submitted to the Green Bank radio telescope, which shows that a few hours of observation may provide sensitivity competitive with future ADMX runs in the mass range near 4 x 10^-6 eV.
Among the theoretical models addressing the dark matter problem, the category based on a secluded sector is attracting increasing interest. The PADME experiment, at the Laboratori Nazionali di Frascati (LNF) of INFN, is designed to be sensitive to the production of a low mass gauge boson A’ of a new U(1) symmetry holding for dark particles. This 'dark photon’ is weakly coupled to the photon of the Standard Model, and it provides an experimental signature for one of the simplest implementations of the dark sector paradigm. The DAΦNE Beam-Test Facility of LNF will provide a high intensity, mono-energetic positron beam impacting on a low Z target. The PADME detector will measure with high precision the momentum of a photon, produced along with A’ boson in e+e- annihilation in the target, thus allowing to measure the A’ mass as the missing mass in the final state. This technique, particularly useful in case of invisible decays of the A’ boson, will be exploited for the first time in a fixed target experiment. Simulation studies predict a sensitivity on the interaction strength (ε**2 parameter) down to 10−6, in the mass region 1 MeV<M_A’<22.5 MeV, for one year of data taking with a 550 MeV beam of 6000 positrons in 40 ns long bunches.
In the middle of 2018, the first run will take place, and early data will give the opportunity to compare the detector performance with the design requirements. This talk will review the status of the experiment and the prospects.
Abstract: I will show how ultra-high-resolution measurements of the gravitational lensing of the Cosmic Microwave Background (CMB) can be used to measure the small-scale matter power spectrum. A robust measurement of structure on scales below 10 kiloparsecs today (M < 10^9 solar masses) with lensing of the CMB requires a telescope with roughly 20 arcsecond resolution or better, and would provide a firm anchor against which to match models of dark matter particle properties and the baryonic influence on the dark matter distribution. For example, a CMB survey at 90 GHz covering 4,000 square degrees of sky, with an instrumental sensitivity of 0.1 microKelvin-arcmin at 10 arcsecond resolution, could distinguish between cold dark matter and an alternative such as 1 keV warm dark matter or 10^−22 eV fuzzy dark matter with about 30-sigma significance, in the absence of baryonic effects; it may also allow one to distinguish between the impact of baryons and the particle nature of dark matter, since each potentially affects the shape of the lensing power spectrum differently. In addition, such a high-resolution, low-noise CMB Dark Matter Survey would also push the boundaries of our knowledge about the early Universe, dark energy, reionization, and galaxy evolution.
Abstract: Various theories beyond the Standard Model possess weakly interacting sub-eV particles often referred to as WISPs. Such particles, if they exist, would mediate long-range forces between macroscopic bodies. Strong constraints exist on such ultralight bosons with scalar and vector couplings to fermions from “spin-independent” experiments involving unpolarized test bodies. In contrast, present direct laboratory constraints on exotic spin-dependent forces from pseudoscalar and axial couplings to fermions are many orders of magnitude weaker. Motivated by the disparity between these limits, we investigated whether tighter constraints on pseudoscalar and axial couplings can be extracted using the data from spin-independent searches combined with higher-order perturbation theory calculations. We derive the functional forms for all possible exotic spin-independent interactions arising from two-boson exchange with pseudoscalar and axial couplings between a pair of fermions in the nonrelativistic limit. Some of our results coincide with the results found in the literature calculated a long time ago for pseudo-Goldstone bosons with Yukawa and derivative couplings in the context of nuclear forces: others are completely new. Coupled with the stringent limits from current spin-independent experiments, we have opened up a new opportunity to constrain spin-dependent couplings over new length scales for different fermionic species. We present the first example of the successful use of this approach.
No-host Dinner
Sea Basin Restaurant
642 Route 25A, Rocky Point, NY
631-744-1643
October 3, 2018, 6:30 PM
Cost: $42/pp
Abstract: MiniBooNE has recently updated both their short baseline neutrino oscillation and sub-GeV dark matter analyses. Both results have strong implications for the dark sector. The oscillation analyses suggests the existence of at least one sterile neutrino, while the null results from the sub-GeV dark matter search have placed the most stringent limits to date, on the vector portal dark matter scenario, for dark matter with masses between 5 and 50 MeV. This talk will present both of these analyses, their results, and discuss some of the implications to the dark sector.
We set constraints on millicharged particles (mCPs) based on electron scattering data from MiniBooNE and the Liquid Scintillator Neutrino Detector (LSND). Both experiments are found to provide new (and leading) constraints in certain mCP mass windows: 5 − 35 MeV for LSND and 100 − 180 MeV for MiniBooNE. Furthermore, we provide projections for the ongoing Fermilab SBN program, the Deep Underground Neutrino Experiment (DUNE), and the proposed Search for Hidden Particles (SHiP) experiment. In the SBN program, SBND and MicroBooNE have the capacities to provide the leading bounds in the 100-300 MeV mass regime. Both DUNE and SHiP are capable of probing parameter space for mCP masses ranging from 5 MeV − 5 GeV that is significantly beyond the reach of existing bounds, including those from collider searches and SLAC's mQ experiment.
This work is based on arXiv:1806.03310.
Axion-like particles (ALPs) produced in the core of a neutron star can convert to photons in the magnetosphere, leading to possible signatures in the soft and hard X-ray emission from these sources. We study these signatures taking the magnetar SGR 1806-20 as an example. In particular, assuming ALP emission rates from the core that are just subdominant to neutrino emission, the parameter space of ALPs can be constrained by the requirement that the luminosity from ALP-to-photon conversion should not exceed the total observed luminosity from the magnetar. Up to astrophysical uncertainties pertaining to the core temperature, these constraints are competitive with constraints from helioscope experiments in the relevant part of ALP parameter space. Another class of signatures in this context are polarized X-rays, since ALPs only mix with the parallel component of the photon. These polarization signals may be observable by IXPE (in the 2-8 keV range) and X-Calibur (in the 15-60 keV range). A better understanding of the astrophysics of the polarization due to the plasma will be necessary to isolate the contribution from ALPs, in case a polarization signal is observed.
It is well known that light scalar fields present during inflation are coherently excited. We show that if the field couples to gravity in a non-minimal way, the fluctuations at large scales are suppressed with respect to the small scales ones. This fact allows for the field excitations to make a sizeable contribution to the energy density of the universe without generating too large isocurvature fluctuations at observable scales. We show that this mechanism could generate all the observable dark matter and study the main cosmological implications of this setup.
ArXiv: https://arxiv.org/abs/1807.09785
We study the simplest model of a dark sector that forms structure via cooling, in analogy to the baryonic sector.
This dark sector is an asymmetric, sub-dominant component of dark matter, that consists of a dark electron and a dark photon.
The dark-electron perturbations collapse and fragment due to bremsstrahlung cooling, forming astronomical objects of varying size and compactness. These objects may run away into black holes, or be stabilized via kinetic or long-range repulsive Coulomb pressure. Such dark-sector objects may lead to novel signatures at new high-precision astronomical observatories.
The New Experiments With Spheres-Gas (NEWS-G) is dedicated to the direct search for Dark Matter candidates in the 0.1 – 10 GeV range. The experiment uses the novel Spherical Proportional Counter detector, which exhibits a number of key features including: a) low energy thresholds, few tens of eV, owing to low detector capacitance independently of the volume and high gain operation; b) small number of readout channels and potential for directionality; c) background rejection through pulse shape analysis; d) simplicity and use of highly radio-pure materials; e) variety of light target gases, including Hydrogen, Helium, and Neon, allowing optimisation of momentum transfers for low-mass particles in the GeV mass range, significantly increasing the sensitivity to subGeV candidates; and f) possibility to vary the operational pressure and high voltage, providing additional handles to disentangle potential signals from unknown instrumental backgrounds. The first detector SEDINE, a 60cm diameter sphere already operated in the Underground Laboratory of Modane (France), while the full scale detector, with 140cm diameter, will be installed in SNOLab (Canada) later this year. In this talk, the first NEWS-G results based on 9.7kg.days of exposure will be presented, and that status of the project and prospects for the future will be discussed.
We have all heard of the cloud and bubble chambers of course, and the latter in the context of direct WIMP dark matter detection even. However, no one has explored a 3rd phase transition, into solid, until now that is. This talk will introduce the snowball chamber, which utilizes a supercooled liquid, just purified water in the prototype. An incoming particle triggers nucleation in the liquid, forming a solid. We will present the world's first definitive evidence that radiation can trigger freezing in metastable cold water, an effect never before observed, and in particular share AmBe and Cf-252 neutron source calibration data, wherein multiple nucleation sites could be observed, another world first, making our device act just like a reverse bubble chamber. Because the reaction is exothermic, not endothermic as in a bubble chamber, the energy threshold should be lower, perfect for dark sector dark matter searches. We will present the measured background gamma-ray discrimination, high as in a bubble chamber, and the projected sensitivity, with a smaller, more cost-effective detector than many of the competing new technologies. The crystallization may even have directionality which we will demonstrate preliminary evidence for: this would mean higher-density directional detectors than in gas.
Authors: Sankha S Chakrabarty and Pierre Sikivie
Caustic rings of dark matter with tricusp cross-section were predicted to lie in the galactic disk. In the self-similar evolution of the dark halo, their radii increase on cosmological time scales at a rate of order 1 kpc/Gyr. When a caustic ring passes through the orbit of a star, the orbit is strongly perturbed. We find that a star moving in a nearly circular orbit is first attracted towards the caustic ring, then moves with and oscillates about the caustic for approximately 1 Gyr before returning to its original orbit. This results in a stellar overdensity around the caustic ring. We predict such overdensities to be of order 120% near the 2nd caustic ring where the Monoceros Ring is observed and of order 45, 30 and 15% near the 3rd, 4th and 5th caustic rings, respectively. We show that the associated bulk velocities of the stars near the caustic rings are less than a few km/s. We also determine the density profile of interstellar gas near the 5th caustic ring assuming it is in thermal equilibrium in the gravitational potential of the caustic and of the gas itself.
The high-intensity setup, trigger system flexibility, and detector performance -- high-frequency tracking of beam particles, redundant PID, ultra-high-efficiency photon vetoes ― make NA62 particularly suitable for searching new-physics effect from different scenarios. Results from a search for invisible dark photons produced from pi0 decays are given. Fixed target experiments are a particularly useful tool in the search of very weakly coupled particles in the MeV-GeV range, which are of interest, e.g. as potential Dark Matter mediators. The NA62 experiment at the CERN SPS is currently taking data to measure rare kaon decays. Owing to the high beam-energy and a hermetic detector coverage, NA62 also has the opportunity to directly search for a plaethora of long-lived beyond-the Standard Model particles, such as Axion-like Particles and Dark Photons. In this talk, we will review the status of this searches and give prospects for future data taking at NA62.
I will review BaBar's searches for the direct production of new particles in the context of dark sector and other models. Such searches are a high priority for the early running period of Belle II. I will discuss the status of Belle II and the prospects of these searches.