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Lecture notes for Les Houches Summer School 2021: Dark Matter. These lectures give a brief introduction to sub-GeV dark matter models, and then reviews theory and approaches to direct detection of sub-GeV dark matter.
We report on recent progress in the search for dark matter particles with masses from 1 Mev c ^{-2} − 2 to 1 Gev c ^{-2} − 2 . Several dark matter candidates in this mass range are expected to generate measurable electronic-recoil signals in direct-detection experiments. We focus on dark matter particles scattering with electrons in semiconductor detectors since they have fundamentally the highest sensitivity due to their low ionization threshold. Charge-coupled device (CCD) silicon detectors are the leading technology, with significant progress expected in the coming years. We present the status of the CCD program and briefly report on other efforts.
This dissertation presents a search for dark matter in events with one or more jets and large missing transverse energy using proton-proton collisions at center-of-mass energy of 13 TeV. The data was collected in 2016 by the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider (LHC) corresponding to an integrated luminosity of 35.9 $fb^{-1}$. The results are interpreted in terms of Light Non-thermal dark matter model which explains presence of dark matter as well as baryon asymmetry in the universe. Model independent limit on narrow resonance is also obtained for monojet dominant coupling parameter space. There is no evidence for an excess of events above the background processes in the signal region, therefore cross section limits are set for different mediator masses.
In this paper we rewrite the neutrino mixing angles and mass squared differences in matter given, in our original paper, in a notation that is more conventional for the reader. Replacing the usual neutrino mixing angles and mass squared differences in the expressions for the vacuum oscillation probabilities with these matter mixing angles and mass squared differences gives an excellent approximation to the oscillation probabilities in matter. Comparisons for T2K, NOvA, T2HKK and DUNE are also given for neutrinos and anti-neutrinos, disappearance and appearance channels, normal ordering and inverted ordering.
The aims of this research project were to support the experimental effort to discover the particle nature of dark matter through theoretical work at the intersection of particle and astrophysics. In particular, the research was intended to: quantify and reduce astrophysical uncertainties on direct and indirect detection results; improve LHC analyses for dark matter; and improve the theoretical framework in which we contextualize dark matter searches to find unexplored directions.
Why do we exist today? The question simply comes to mind and most of us must have wondered at least once. Scientifically answering it is one of the serious but engrossing challenges in modern physics. The question is translated into another one in language of particle physics; why is there more matter than antimatter in our Universe? Antimatter is composed of antiparticles which have an opposite electric charge to that of particle. In the early Universe, both particles were present in equal amount. However, looking around the present Universe, everything, such as the moon, galaxies and human being, is made of matter. The puzzle is known as matter-antimatter asymmetry of the Universe. This talk will discuss theoretical approaches to solving the mystery in terms of particle physics introducing one possible hypothesis, electroweak baryogenesis, which is the most testable scenario in experiments.
This LDRD addressed one of the central questions in physics today: the lack of antimatter relative to matter in the universe. If antimatter and matter existed in equal amounts they would have annihilated into radiation and we would not exist today. DOE is funding experiments to investigate processes that could lead to lepton number violation and the resulting neutrino-less double beta decay (0nbb) signal that may be observed (lepton number is a property of elementary particles similar to electric charge and lepton number violation would explain the matter-antimatter imbalance). However, even if the 0nbb decay is detected in these experiments, the physics mechanism that violates lepton number would not be known, as there are several candidates. Determining the appropriate mechanism from the experimental data requires theoretical calculations. Theoretical effort in the field has focused on long-range 0nbb decay mechanisms associated with the exchange of light neutrinos between two nucleons. An equally important set of mechanisms are associated with the exchange of heavy particles and short-range physics, including the exchange of massive Majorana neutrinos. Calculating the event rate for 0nbb decays for candidate theories involving heavy particle exchange requires large-scale Lattice simulations of the underlying fundamental theory of Quantum Chromodynamics (QCD). We have performed these simulations on the LLNL supercomputers and have calculated the necessary matrix elements of short-range operators that arise from the exchange of heavy mediators that contribute to 0nbb decay via the leading pion exchange diagrams. Our published results can now be used as input to effective field theory calculations to calculate the 0nbb decay rate for the nuclei involved in the various experimental detectors. In the process of this work we entered the 2018 Gordon Bell Prize competition (the highest prize in scientific supercomputing) with our innovative and highly optimized code and methods and were selected as one of the six international finalists. During this effort we helped with the bring-up of the new LLNL Sierra and Lassen supercomputers by identifying hardware and software problems. Aiming towards the next step of this research, involving the sub-leading nucleon-nucleon direct vertex, we have developed algorithms and codes that will play a significant role in future Lattice QCD calculations involving nucleon-nucleon interactions.
Two analyses searching for new heavy resonances and interpreting the result with dark matter are presented in this dissertation. The first analysis searches for resonances decaying into dijet final states using the proton-proton collision data at center mass of $\sqrt{s}=13$ TeV with the CMS detector at Large Hadron Collider in2016, corresponding to a total integrated luminosity of 36 fb -1 . No significant evidence for the production of new particles is observed. A simplified model of interactions between quarks and dark matter is used to interpret the result. The second analysis searches for resonances decaying into dijet final states using the proton-proton collision data at center mass of $\sqrt{s}=13$ TeV with the CMS detector at Large Hadron Collider in 2016, 2017, and 2018, corresponding to a total integrated luminosity of 137.5 fb -1 . A b-tagger named DeepJet is used to examine the events with jets containing B hadrons. No evidence of new heavy resonances is observed, as well. The 95% confidence level cross-section upper limit is set on excited b-quark b* and Coloron models. Limits are also set on a simplified model of interactions between b-quarks and dark matter.
This project pursued two major experimental goals related to the quantum engineering of the ensemble of nuclear spin qubits, as a potential sensing platform for axion-like dark matter: (1) control the fidelity of spin ensemble state preparation, (2) characterize the coherence time of the spin ensemble under different drive conditions. We have successfully achieved these goals. We have experimentally demonstrated control over the polarization of the 207 Pb nuclear spin ensemble, using light-induced transient paramagnetic centers. We have also performed NMR measurements on the 207 Pb spin ensemble in solid ferroelectric PMN-PT, demonstrating the T 2 coherence time of 16.7 ms. We have used this approach to set new experimental limits on the EDM and the gradient interactions of axion-like dark matter in the mass range 162 neV to 166 neV. In addition, having characterized the magnetic resonance properties of the 207 Pb spin ensemble in solid ferroelectric PMN-PT, we have formulated the technical requirements needed to reach the quantum sensitivity limits in a magnetic resonance-based search for axion-like dark matter.
Decades of dark matter searches with increasingly higher sensitivity have so far not been able to detect the most-favored hypothetical dark matter particles. This has increased interest in sterile neutrinos with masses in the kilo-electronvolt (keV) range as possible dark matter candidates. We have established a and new and world-leading approach to search for keV-scale sterile neutrinos with superconducting radiation detectors. For this, we have implanted radioactive beryllium-7 (Be-7) nuclei into our superconducting tunnel junction (STJ) detectors and measured the recoil energy of the lithium-7 (Li-7) daughter nucleus with high accuracy. If the associated electron neutrino wave function contains some admixture of a keV sterile flavor, the Li-7 recoil energy will be shifted and produce an additional peak in the spectrum whose energy depends on the sterile neutrino mass. While we have not observed any evidence for sterile neutrinos in these precision decay experiments, the experiment has increased the sensitivity of sterile neutrino searches by a factor of ~10 over competing approaches in the mass range from ~10 to ~800 keV. The next generation of STJ detectors that we have developed as part of this project will be able further increase the sensitivity of the sterile neutrino search by at least another two orders of magnitude.
The nuclear equation of state (EOS) is at the center of numerous theoretical and experimental efforts in nuclear physics, motivated by its crucial role in our understanding of the properties of nuclear matter found on Earth, in neutron stars, and in neutron-star mergers. With advances in microscopic theories for nuclear interactions, the availability of experiments probing nuclear matter under conditions not reached before, and the advent of multi-messenger astronomy, the next decade will bring new opportunities for determining the nuclear matter EOS.
Dark matter is one of the most interesting research topics in physics. Many particle physicists are trying to identify it because we know that dark matter could be a major component of a complete fundamental description of nature. The Muon g-2 Experiment at Fermilab measures the anomalous precession frequency of the muon. Oscillations of this precession frequency could be produced by dark matter coupling to muons. This talk will describe how we could observe DM signals in the Muon g-2 data. I will explain how we determine the Muon g-2 DM mass range sensitivity, and analysis strategies throughout the mass range. Finally, I will present the expected Muon g-2 experiment discovery/exclusion reach in selected DM model-dependent scenarios.
Long-baseline atom interferometer (LBAI) experiments offer unprecedented sensitivity to ultralight scalar dark matter (DM) [1], however reconstruction of a putative DM signal with traditional frequency-domain analysis requires ``perfect data (i.e., regularly-sampled with no missing samples). In a real LBAI experiment, there will undoubtedly be imperfections in the data leading to downtime. This downtime can arise from operational considerations (e.g., maintenance), the operational environment (motion of people and animals [2] or elevators), and robustness of the experimental apparatus (e.g., bad atom launches). In this work, we investigate the impact of various downtime models on the overall DM sensitivity of such an experiment. We compare the sensitivity for each downtime model as determined by a ``compound FFT analysis to a baseline no-downtime case. We also show how much sensitivity can be regained by moving to a Lomb-Scargle frequency analysis, as in [2]. Furthermore, we demonstrate reconstruction of the DM wave s phase as well as its frequency. [1] D. Antypas, et al, ``New Horizons: Scalar and Vector Ultralight Dark Matter (2022). arXiv:2203.14915 [2] J. Carlton and C. McCabe, ``From RATs to riches: mitigating anthropogenic and synanthropic noise in atom interferometer searches for ultra-light dark matter (2023). arXiv:2308.101731
The Superconducting Quantum Materials and Systems Center, led by Fermi National Accelerator Laboratory, is one of five research centers funded by the U.S. Department of Energy as part of a national initiative to develop and deploy the world s most powerful quantum computers and sensors. SQMS will also apply the same technologies used for quantum computing, such as SRF cavities and superconducting qubits, to search for fundamental physics. This presentation will focus on the SERAPH experiment, a family of superconducting haloscopes being developed by SQMS to search for wavelike dark matter like axions and dark photons. In this presentation, I will focus on the progress of the current phase of SERAPH, which will search dark photon dark matter using a widely-tunable SRF cavity (4-7 GHz) with Q>10^8. In parallel, SQMS has recently developed superconducting transmon qubits with leading coherence times. I will report new results for SQMS dark matter searches implementing these qubits to subvert the Standard Quantum Limit noise.
One of the challenges in exploring promising novel materials for dark matter searches is the detection of sub-eV energy excitations from light-dark matter interaction with a target material. Dark matter interaction can excite sub-eV optical phonon modes in polar materials like sapphire. We plan to utilize superconducting qubits on a sapphire substrate to study their response to energy deposition into the superconducting film and the substrate by irradiating them with photons and particles and also generating phonons in the chip. A fraction of the incident energy is expected to break Cooper pairs in the superconductor, releasing quasiparticles. As the quasiparticles tunnel across the Josephson junction, the charge parity of the qubit changes. The parity switching rate is proportional to the quasiparticle density in the qubit superconductor film and can be measured using standard qubit readout protocol. This presentation describes our ongoing attempt to build such a prototype detector.
Wave-like dark matter candidates such as axions or dark photons in the microwave frequency range can be probed using resonant superconducting cavities. We demonstrate a quantum-enhanced sensing approach based on a multimode, high-Q superconducting RF (SRF) cavity, where a large Fock state is prepared in the storage mode via sideband transitions mediated by a transmon ancilla and a measurement-based feedforward protocol, achieving high-fidelity Fock states [1]. The prepared |n⟩ state induces stimulated emission from the dark-matter field, providing an (n + 1) enhancement in transition probability and proportional boost in signal rate [2]. A secondary cavity mode functions as an in-situ reference to calibrate noise. We present the control sequence, noise-referencing strategy, and projected sensitivity improvements for axion and dark-photon detection. This multimode architecture combines large Fock state preparation with noise calibration, offering a practical path to increased scan rate in cavity-based dark-matter searches.
In recent years, the combination of advanced quantum Monte Carlo (QMC) methods and local interactions derived from chiral effective field theory (EFT) has been shown to provide a versatile and systematic approach to nuclear systems. Calculations at next-to-next-to-leading order in chiral EFT have lead to fascinating results for nuclei and nucleonic matter. On the one hand, ground-state properties of nuclei are well reproduced up to A $≤$ 16, even though these potentials have been fit to nucleon-nucleon scattering and few-body observables only. On the other hand, a reasonable description of neutron-matter properties emerges. While regulator functions applied to two- and three-nucleon forces are a necessary ingredient in these many-body calculations, the use of local regulators leads to a substantial residual regulator and cutoff dependence that increases current theoretical uncertainties. In this contribution, we review local chiral interactions, their applications, and QMC results for nuclei and neutron matter. In addition, we address regulator issues for such potentials and present a possible path forward.
We discuss low scale implications of a class of SUSY GUTs with non-universal SSB masses and confront them with the current experimental results from the direct detection of dark matter experiments, as well as the collider experiments of different center of mass energies. This class of SUSY GUTs are expected to be tested soon in direct detection dark matter experiments through the scatterings of Higgsino and Wino-like dark matters at nuclei. Besides, the stop and gluino will be able to be probed and tested up to about 5-6 TeV in the current and future collider experiments. Furthermore, these probe scales are expected to be further when high luminosities are achieved.