# nuclear seminar

## Probing Strong Nucleon-Nucleon Interactions at Short Distance

Nucleon interactions at short distances are not well-described in either QCD or the field theory. Experimentally, a series of electron-nucleon scattering measurements at Jefferson Lab (JLab) have determined about 20% of nucleons in heavy nuclei are moving fast (above the Fermi momentum) due to hard, short-distance interactions with another nucleons, forming so-called short-range correlated (SRC) pairs. Understanding those SRC pairs is necessary in providing a complete description of nuclear structure. It also offers us a unique chance to probe the tensor and repulsive force at intermediate to short distances. In this talk, I will present recent results from the JLab Hall A tritium program which studied the momentum distribution, and spin/isospin structure of SRC pairs in the mirror nuclei tritium and helium-3. I will then discuss how those measurements help us better understand the short-distance part of strong nucleon-nucleon interactions, and their connections to future experiments.

## New detection techniques for axion dark matter

The axion is one of the best motivated dark matter candidates, simultaneously solving the Strong CP problem as well as providing the dark matter of the universe. However, in comparison to WIMPs the axion was historically neglected by experimental efforts. This has been changing in the last five years, which a bevy of new experiment proposals and results. I outline several recent updates for new detection ideas, including plasma haloscopes and axion detection with phonon-polaritons.

## The Project 8 Neutrino Mass Experiment

Although the existence of neutrino mass is firmly established, the precise neutrino mass scale remains unknown. To directly probe this property, measurements of the endpoint of the tritium beta spectrum have achieved the greatest sensitivity, recently reaching the sub-eV scale. In this talk, I will present Project 8, an experimental concept based on the novel Cyclotron Radiation Emission Spectroscopy (CRES) technique. Project 8 has recently released its first measurements of the tritium beta spectral endpoint and demonstrated its high precision spectroscopy using krypton calibration. An R&D campaign is now underway to demonstrate scalability of the CRES technique and to develop the atomic tritium source required. Building on these successes, a next-generation experiment is envisioned with neutrino mass sensitivity down to 40 meV.

## Measuring the muon’s wobble: Analysis of the Runs 2 & 3 data from the Muon g-2 Experiment at Fermilab

Abstract: In April 2021, the Muon g-2 Experiment at Fermilab reported its first measurement of the muon magnetic anomaly to an unprecedented precision of 460 ppb. The result agrees with the previous measurement performed at Brookhaven National Laboratory, and the combined experimental value is in tension with the Standard Model prediction at 4.2 sigma, a possible hint of new physics. The first result from the Fermilab experiment was based on its Run-1 data, collected in 2018, which comprises just 6% of the experiment’s target statistics. The Runs 2 & 3 data, collected between 2019-2020, amount to a four-fold increase in statistics and consequently, a factor of two reduction in the statistical uncertainty. The measurement relies on the precise determination of two key quantities: the anomalous precession frequency of the muon and the magnetic field. In this seminar, I will describe the Fermilab experiment with a focus on the anomalous precession frequency analysis of the Run-2 and Run-3 data. I detail the procedures used, highlighting improvements compared to the Run-1 analysis. I also show blinded results and discuss some of the largest systematic uncertainties in the analysis, as well as provide an outlook and current status of the experiment.

## Magnetic strength of 3He

The hyperfine structure of hydrogen-like ions are a unique probe to access nuclear magnetic

moments and nuclear structure. Thus, while eliminating the ignorance of essential links in

metrology due to insufficiently known magnetic moments, at the same time these ions

provide complementary insight into the inner nucleus. The very recently started 3He-

experiment exploits these characteristics to provide a new standard for absolute precision-

magnetometry and determine the nuclear charge and current distribution of 3He.

To this end, a novel four Penning-trap experiment was designed and built. Using novel

techniques, this system enables non-demolition measurements of the nuclear quantum state

and allows sympathetic laser cooling of single, spatially separated ions to sub-thermal

energies [1].

In the first measurement campaign, 3He was investigated by exciting microwave transitions

between the ground-state hyperfine states. This enabled us to determine the nuclear g-factor,

the electronic g-factor and the zero-field ground-state hyperfine-splitting of 3He+ with a

precision of 5*10-10, 3*10-10 and 2*10-11, respectively [2].

Our measurement constitutes the first direct and most precise determination of the 3He+

nuclear magnetic moment. The result is of utmost relevance for absolute precision

magnetometry, as it allows the use of He NMR probes as an independent new standard with

much higher accuracy. In addition, the comparison to advanced theoretical calculations

enables us to determine the size of the 3He nucleus with a precision of 2,4*10-17m.

In future, we aim at a direct determination of the bare nuclear magnetic moment of 3He to be

compared to the bound-state result. For this measurement, it is essential to implement new

methods and technology such as sympathetic laser cooling and a high-precision voltage

source based on Josephson junctions [3]. The latest results, status and the future prospect of

the experiment will be presented.

References

[1] A Mooser et al., J. Phys.: Conf. Ser. 1138, 012004 (2018)

[2] A. Schneider et al., Nature 606, 878 (2022)

[3] A. Schneider et al., Ann. Phys. 531, 1800485 (2019)

## Precision measurements of rare pion decays in the Pioneer experiment

Precision measurements of rare decays of charged pions offer important tests of the standard model. The ratio of pi+ -> e+ nu to mu+ nu decay provides the best test of electron–muon weak universality and is uniquely sensitive to non-V-A exotic currents. The rate of pion beta decay pi+ -> pi0 e nu offers a theoretically pristine sensitivity to the Vud matrix element of the CKM matrix.

## Probing nonlinear gluon dynamics at RHIC and the EIC

The gluon distribution function grows with lower and lower momentum fraction very fast. As the total scattering cross section is bound by quantum mechanics, the raise of the gluon density has to be tamed, which is explained by gluon recombination under the color glass condensate (CGC) framework. A definitive discovery of nonlinear effects in QCD and as such the saturation regime would significantly improve our understanding of the nucleon structure and of nuclear interactions at high energy. Two particle azimuthal correlation is one of the most direct and sensitive channels to access the underlying nonlinear gluon dynamics. In this talk, we will present the recent results of forward di-hadron correlations measured at RHIC, together with the signatures of gluon saturation predicted by CGC. New opportunities for measurements with the STAR forward upgrade and future EIC to study the nonlinear effects in QCD will also be discussed.