Session M11: Physics Beyond the Standard Model II

Search for axion-like particles using nuclear targets in the GlueX detector

We report on the results of the first search for the production of axion-like particles (ALP) via Primakoff production on nuclear targets using the GlueX detector. This search uses an integrated luminosity of 100 pb⁻¹·nucleon on a ¹²C target, and explores the mass region of 200 < m_a < 450 MeV via the decay X → γγ. This mass range is between the π⁰ and η masses, which enables the use of the measured η production rate to obtain absolute bounds on the ALP production with reduced sensitivity to experimental luminosity and detection efficiency. We find no evidence for an ALP, consistent with previous searches in the quoted mass range, and present limits on the coupling on the scale of O(1 TeV). We further find that the ALP production limit we obtain is hindered by the peaking structure of the non-target-related dominant backgrounds, and comment on how that can be improved in future higher-statistics dedicated measurements.   

A lunar orbital experiment to detect exospheric neutrons and antineutrons as a probe of baryon number violation.

We propose a small satellite experiment to orbit the moon to probe for $nar{n}$ oscillations predicted by several beyond the standard model theories and important to an understanding of baryogenesis. The best terrestrial $nar{n}$ oscillation experiments that use free neutrons rely on long path lengths inside of large, magnetically sheilded vacuum chambers built near reactor neutron sources. As the quality factor is $propto Nt^2$ for $N$ neutrons and flight time $t$, the hundreds of meters scale required of these chambers has limited the probing power of these efforts. Exospheric neutrons generated by cosmic spallation on the lunar surface are produced with a sufficiently large flux, travel in a low magnetic field, and have long flight path lengths to make an orbital experiment significantly competitive with future proposed terrestrial experiments.   

Tri-nucleon decay in 130Te with CUORE

The conservation of baryon number in the Standard Model is based on an empirical symmetry rather than being derived from fundamental principles. If evidence were to be found indicating the violation of this symmetry, it would have profound implications for our understanding of the universe, particularly regarding the origin of the matter-antimatter imbalance. One proposed mechanism that could break the conservation of baryon number is tri-nucleon decay, which involves the simultaneous decay of three nucleons within a nucleus. The resulting decay products are emitted with energy in the GeV range, making them a promising signal for detection in the CUORE experiment. In cases where the daughter nucleus following the decay is unstable, the subsequent decay radiation can provide an additional signature in coincidence with the emitted energy. In our presentation, we will provide a comprehensive overview of the search signatures, the background factors involved, and the analysis techniques utilized in this investigation.   

Overview of the Tracking System and Kinematics Measurements for the MOLLER Experiment

MOLLER (Measurement Of a Lepton-Lepton Electroweak Reaction) is a parity-violating experiment set to begin data-taking in Jefferson Laboratory’s experimental Hall A in 2025. The parity-violating asymmetry of Møller scattered electrons, A_PV , will be measured and used to extract the weak charge of the electron, Q_W^e , to never before seen levels of precision. At tree level, the overall factor that correlates Q_W^e to A_PV is called the kinematic factor, Α, and is dependent on the incoming beam energy and center of mass scattering angle of the electron. A vital component of MOLLER will be its tracking system which will be used for kinematics measurements and will allow us to determine the kinematic factor and its uncertainty, as well as to monitor backgrounds and verify detector response.

Calibration of our tracking system and verification of our kinematics must be completed in order to calculate Q_W^e to the desired level of precision. This talk will overview the tracking system and the plan for our kinematics measurements. Specifically a brief overview will be given for the following subsystems: the ¹²C foil targets, the sieve and blocker collimators, the trigger scintillator system, the gas electron multiplier tracking detectors, and the pion detector system.   

Optics Calibration for the MOLLER Experiment (for the MOLLER Collaboration)

A precise measurement of the parity-violating asymmetry (A_PV) in MOLLER Experiment is strongly dependent on our ability to accurately determine the average kinematic factor and verifying the acceptance of the toroidal spectrometer system. The kinematic factor, for Møller scattering, depends not only on the scattering angle θ but also on the incident beam energy (E). The experiment aims to utilize the GEM tracking system in conjunction with a sieve-slit collimator and a set of thin foil targets to obtain an optics transport map between the variables defining the scattered electron (θ_lab, φ_lab, E', v_z) and the GEM variables (r, r', φ, φ') thus allowing the determination of the average kinematic factor as well as the acceptance function. In this talk, the various kinematic aspects that were involved in the development of the sieve-slit collimator design together with the performance of a Machine Learning based reconstruction algorithm will be presented.   

Beyond Standard Model Physics with the Electron Ion Collider

The upcoming Electron Ion Collider (EIC) at Brookhaven National Laboratory will make significant advances in our understanding of nucleon structure and dynamics. The extraordinary luminosity specifications for this new machine open the door to measurements sensitive to physics beyond the standard model, such as charge lepton flavor violation in the tau sector. Furthermore, the unique phase space access allows measurements at the EIC to constrain fundamental parameters in the standard model, such as the weak mixing angle. Finally, it has been shown that inclusion of EIC measurements into the Standard Model Effective Field Theory framework resolves flat directions providing complementary constraints to other measurements planned in the next decade. This talk will give an overview of different measurements and plans to further refine sensitivities using the ePIC detector.   

Precise half-life measurement of 29P

As part of our program to test for physics beyond the standard model via β decays, we measured the half-life of ²⁹P that undergoes a T=1/2 nuclear mirror transition. The radioactive beam was produced in the ¹H(³⁰Si,2n)²⁹P reaction, with a 24 A MeV ³⁰Si beam impinging on a hydrogen target kept at 2.0 atm and liquid nitrogen temperature. Using the MARS spectrograph, a high purity ²⁹P beam at 22 A MeV was extracted from the reaction products. Then, the radioactive beam was extracted in air through a 51 μm thick Kapton window, and further passed through a 0.3 mm thick BC-404 plastic scintillator and an Al degrader. The thickness of the degrader was set to stop the desired activity in the 76-μm-thick Mylar tape of our fast tape transport system. The radio-purity of the collected activity exceeded 99.9%. After collecting the sample, the beam was turned off, and the activity was moved in the center of our 4π proportional counter, where it was multiscaled for 84 s (~40 half-lives). Repeating such collect-move-detect cycles, we collected more than 10⁸ events. The experiment was split in sub-runs differing in detector bias, signal discrimination threshold, and dominant dead-time. No systematic bias could be identified. Our preliminary half-life value is 4.1140(8) s, which is the most precise measurement to date.

    

Precise Penning trap Q value determinations for forbidden and low energy β-decays

Historically, nuclear β-decay studies have provided insight into the nature of the weak interaction. They continue to be relevant for tests of the standard model, searches for new physics, and investigations of the properties of neutrinos. The β-decay Q value, the energy equivalent of the mass difference between parent and daughter atoms, can be precisely measured using Penning trap mass spectrometry to provide a result that is completely independent from spectroscopy measurements that determine the kinetic energy of the decay products. Q value measurements can be used as an inputs for theoretical calculations of β-spectrum shape factors, electron branching ratios, and half-lives. They also provide a test of systematics in precise β-spectroscopy measurements, and enable the identification of β-decays with very low Q values that could be used in direct neutrino mass determination experiments. In this presentation we will review Q value measurements for the forbidden decays of long-lived primordial nuclides, including a recent Penning trap measurement of ¹⁷⁶Lu. We will also discuss a recent evaluation of all potential ultra-low Q value decay nuclides and present recent results from a measurement on ⁷⁵Se.   

A Hint of the Existence of a Dark Photon

We perform a global QCD analysis of high energy scattering data within the JAM Monte Carlo framework, including a coupling to a dark photon. We first set limits on the dark photon mass and mixing parameter assuming that the SM is the true theory of Nature, taking into account also the effect on g − 2 of the muon. If instead we entertain the possibility that the dark photon may play a role in deep-inelastic scattering (DIS), we find that the best fit is preferred over the SM at 6.5σ, even

after accounting for missing higher order uncertainties. The improvement in χ2 with the dark photon is stable against all the tests we have applied, with the improvements in the theoretical predictions spread across a wide range of x and Q2. The best fit yields a value of g−2 which significantly reduces the disagreement with the latest experimental determination.