Atom interferometers exploit the quantum mechanical, wavelike nature of massive particles to make a broad range of highly precise measurements. Recent technological advances have opened a path for atom interferometers to contribute to two areas at the forefront of modern physics: gravitational wave astronomy and the search for dark matter. In this talk, I will describe a new experiment, MAGIS-100, that will use a 100-meter-tall atom interferometer to pursue these directions. MAGIS-100 will serve as a prototype gravitational wave detector in the mid-band frequency range 0.1 Hz to 10 Hz, which is complementary to the frequency bands addressed by laser interferometers such as LIGO and the planned LISA experiment. I will discuss the scientific motivation for gravitational wave detection in the mid-band. In addition, I will explain how MAGIS-100 can look for ultralight dark matter, a well-motivated class of dark matter candidates that behave as coherently oscillating fields. Finally, I will briefly introduce a related atom interferometry experiment we are building at Northwestern to perform fundamental tests of gravity.
Two of the biggest open questions in the Standard Model of Particle Physics are: is the neutrino its own antiparticle, a Majorana particle, and is Peccei-Quinn Symmetry with the resulting axion the solution to the strong CP problem. The answer to these questions is a portal to new physics and the answer to the even bigger questions of the generation of the matter-antimatter asymmetry and the nature of dark matter. My group works to address these questions with searches for neutrinoless double-beta decay and ultra-light axions. In this talk, I will review the physics that connects these two efforts, the current status of the fields, and our R&D efforts towards the next-generation experiments.
Abstract: Anomalies in gauge theories are of great interest because they represent topological features of the theory that are not contained in the Lagrangian. We will discuss here the role of the chiral anomaly in deeply inelastic scattering (DIS) of electrons off polarized protons where one observes a subtle interplay between hard parton dynamics and the topology of the QCD vacuum. Using a powerful worldline formalism, we demonstrate that the "triangle" graph provides the dominant contribution in the DIS "box" diagram both in the Bjorken limit of large Q^2 and in the Regge limit of small x_Bj. We then discuss how the infrared pole of the anomaly is canceled in this formalism leading to novel emergent dynamics governing how the spin of the proton diffuses from fast (large x) modes to slow (small x) modes. In particular, we present an effective action, consistent with anomalous chiral Ward identities, that is governed by dynamical scales corresponding to the topological charge density and the gluon saturation scale. We conjecture how the latter influences the former and emphasize that these ideas can be tested at the Electron-Ion Collider.
* title of the seminal paper by R. L. Jaffe and A. Manohar (Nucl. Phys. B 337, 509 (1990))
The prospects of extracting new physics signals in a coherent elastic neutrino-nucleus scattering (CEvNS) process are limited by the precision with which the underlying nuclear structure physics, embedded in the weak nuclear form factor, is known. In this talk, I will present a microscopic nuclear structure physics calculations of charge and weak nuclear form factors and CEvNS cross sections on $^{12}$C, $^{16}$O, $^{40}$Ar, $^{56}$Fe and $^{208}$Pb nuclei. We obtain the proton and neutron densities, and charge and weak form factors by solving Hartree-Fock equations with a Skyrme (SkE2) nuclear potential. We validate our approach by comparing $^{208}$Pb and $^{40}$Ar charge form factor predictions with elastic electron scattering data. In view of the worldwide interest in liquid-argon based neutrino and dark matter experiments, we pay special attention to the $^{40}$Ar nucleus and make predictions for the $^{40}$Ar weak form factor and the CEvNS cross sections. Furthermore, we attempt to gauge the level of theoretical uncertainty pertaining to the description of the $^{40}$Ar form factor and CEvNS cross sections by comparing relative differences between recent microscopic nuclear theory and widely-used phenomenological form factor predictions. Future precision measurements of CEvNS will potentially help in constraining these nuclear structure details that will in turn improve prospects of extracting new physics.
I am an external collaborator of the eROSITA science team. It is an X-ray instrument built by the MPE in Germany. It was successfully launched in July 2019. eROSITA will map the entire sky in X-ray band and it will be 25 times more sensitive than the previous ROSAT All Sky Survey.
I will discuss state of the art population synthesis models that improve on the following aspects with respect to most available models. (a) Treatment of the UV spectral range, including new evolutionary tracks and updated treatment of the ionizing radiation emitted by the stellar population. (b) Improved treatment of TP-AGB stars that dominate the NIR spectral range. (c) Definition of new diagnostics to characterize the combined stellar and nebular emission and the cold ISM in galaxies. (d) The role of interacting binary stars on the integrated spectra of stellar populations will be discussed and compared with the effects produced by stochastic fluctuations in low mass populations. Single star models are available in a wide range of metallicity, from Z = 0 to Z = 0.06, and are ready to use to interpret the spectra of galaxies of any age at low and high redshift. Applications will be discussed.
Lattice Quantum Chromodynamics QCD provides a way to have a precise calculation and a new way of understanding the hadrons from first principles. From this perspective, I will first present a precise calculation of the pion form factor using overlap fermions on six ensembles of 2+1-flavor domain-wall configurations generated by the RBC/UKQCD collaboration with pion masses varying from 137 to 339 MeV. With a z-expansion fitting of our data, we find the pion mean square charge radius to be $\braket{r^2}_\pi = 0.437(7)(7) {\rm{fm^2}}$, including the systematic uncertainties from pion mass, lattice spacing and finite volume dependence. It agrees with the experimental value $\braket{r^2}_\pi = 0.434(5) {\rm{fm^2}}$ at a percent level. The second topic is lattice calculation of proton momentum and angular momentum fractions. As confirmed from experiment and lattice QCD calculation, the total helicity contribution from quark is just about $\sim 30\%$ of the proton spin. Determination of the rest contributions from quarks and gluons to the nucleon spin is a challenging and important problem. On the lattice side, one way to approach this problem is using the nucleon matrix element of the traceless, symmetric energy-momentum tensor (EMT) to determine the momentum and angular momentum distributions of up, down, strange and glue constituents. Since the EMT of each parton species are not separately conserved, we summarized their final angular momentum fractions by considering mixing and non-perturbative renormalization at $\overline{\rm{MS}}(\mu = 2 \ {\rm{GeV}})$ and use the momentum and angular momentum sum rules to normalize them.
The CP-violating effects observed thus far appear in flavor-changing processes and in a manner more or less consistent with the predictions of the Standard Model (SM). However, it has long been thought that the observed size of the cosmic baryon asymmetry suggests that mechanisms of CP violation beyond the CKM paradigm should exist. Permanent electric dipole moment searches are exquisite probes of new sources of P and CP violation, whereas processes that would break C and CP are not well studied. The decay $\eta\to\pi^+\pi^-\pi^0$ is an ideal process in which to search for flavor-diagonal C and CP violation. The patterns of C and CP violation that could emerge from an observed violation of mirror symmetry in the Dalitz plot distribution of $\eta\to\pi^+\pi^-\pi^0$ decay would speak to patterns of new physics as well. In particular, the isospin of the underlying C- and CP-violating structures can be reconstructed from their kinematic representation in the Dalitz plot. Our analysis of recent KLOE-2 data reveals that the C- and CP-violating amplitude with total isospin $I = 2$ is much more severely suppressed than that with total isospin $I = 0$. We conclude with a discussion of the constraints on possible new C- and CP-odd operators as derived from SM effective field theory.
It is known from the Sakharov conditions that baryon number violation is required to explain the current observable universe's baryon abundance (BA) and associated matter-antimatter asymmetry; further, it seems that Standard Model (SM) B-L conserving processes (such as the sphaleron) are unable to naturally generate an adequate asymmetry without high-scale, effectively untestable physics being invoked to create a primordial lepton asymmetry. An alternative, testable theoretical framework (post-sphaleron baryogenesis) predicts low-scale (observable) B-L violating neutron-antineutron transformations which can produce a viable BA. Such transformations can be sought in future free neutron beam (European Spallation Source, ESS) and intranuclear bound neutron (DUNE, Hyper-Kamiokande) experiments; I will review past incarnations of these experiments, their future sensitivities, and advocate for their complimentary necessity. Current experimental work at ORNL in neutron disappearance phenomena will also be discussed as a stepping stone to these ultimate goals. These topics will be a focus of an upcoming Amherst Center for Fundamental Interactions workshop, a review (pre-CDR) paper from the ESS NNBar Collaboration, and the 2021 Snowmass Process.
With the availability of cost-effective digitizers and powerful pipeline processors, modern spectroscopy can be performed completely in the digital domain with minimal analog front-end signal processing. These systems offer the flexibility and extensibility of digital signal processing algorithms to simultaneously extract multiple waveform parameters such as pulse height and start time from faint signals buried in background noise. However, pulse fitting was traditionally a computationally intensive task performed offline on computing clusters in the final analysis. I present new algorithms we have developed to perform full nonlinear covariant least-squares fits for optimal resolution of 30 keV proton pulses in the Nab experiment. These algorithms can be implemented in digitizer firmware to increase the resolution and efficiency of our hardware trigger as well as on graphics processing units (GPUs) for high precision online analysis of triggered waveforms.
