07.02.2024
Since October 2024, Tyler Kutz has held a tenure-track assistant professorship in experimental hadron and nuclear physics at the Institute for Nuclear Physics, where he is PI at the PRISMA+ Cluster of Excellence. After his postdoctoral position at the Massachusetts Institute of Technology (MIT), he moved to Mainz to begin his professorship, where his expertise in electron scattering makes him a key addition to the MESA (Mainz Energy-recovering Superconducting Accelerator) team. "I use electron scattering to study nuclear structure and fundamental interactions," explains Tyler.
An active member of international collaborations, Tyler has been active in Mainz since the beginning of his career. "My first Ph.D. project was on detector development for parity-violating electron scattering. During this time, I traveled to Mainz several times for beam tests at MAMI, so I was already familiar with Mainz and its experiments. Now I am extremely excited to join MESA."
The future of MESA
MESA is a unique facility that offers a variety of new opportunities for fundamental physics research and has two main experiments: MAGIX and P2. In the so-called "Energy Recovery Linac" mode, the MAGIX experiment will run with very high beam currents. The P2 experiment will run in "extracted beam" mode, in which the beam can be recirculated a third time, gaining an additional 50 MeV of energy. The accelerator will begin operation in a start phase in late 2025 and will gradually increase its operation in several stages. MESA will be completely ready for use around 2029."I am looking forward to contributing to the measurements of the weak mixing angle and lead neutron skin thickness at P2, as well as measurements of the proton form factor with MAGIX.”
Tyler’s contributions to P2 will build on his experience as a graduate student and postdoc. Starting in 2012, Tyler was involved in the PREX and MOLLER experiments at Thomas Jefferson National Accelerator Facility (JLab). PREX, like the MREX experiment at P2, used parity-violating electron scattering (PVES) to study the neutron distribution in 208Pb. The so-called neutron skin thickness of heavy, neutron-rich nuclei has important implications for nuclear theory, and can be used to constrain the properties of nuclear matter and neutron stars. MOLLER, like the flagship P2 measurement, will use PVES to perform a high-precision extraction of the weak mixing angle, a measure of the relative strengths of the weak and electromagnetic interactions. It can be calculated very precisely theoretically, making it an important quantity in the search for physics that cannot be explained by the Standard Model of particle physics (or “new physics”). Any discrepancies between experimental data and theoretical predictions could indicate the existence of such effects.
Next door to P2 is the MAGIX experimental hall. The MAGIX spectrometer, with its innovative gas-jet target, will probe the structure of protons and light nuclei. "In fixed-target experiments, the target is traditionally solid or liquid, so the scattered electrons have to pass through a lot of material that contaminates the measurements." Such a gas target, which has already been extensively tested at the local MAMI accelerator, significantly reduces multiple scattering effects and background generation by eliminating the target walls required for many traditional targets. These effects are further reduced thanks to the "windowless connection" between the spectrometers and the scattering chamber. This will improve our understanding of nucleon form factors, provide important information for precision electroweak studies, and enable the search for dark photons.
In addition to participating in the existing experimental program at MAGIX, Tyler also hopes to make some new contributions. "I am interested in starting a campaign of measurements related to two-photon exchange (TPE) with MAGIX. Specifically, beam-normal single-spin asymmetries (SSA) where the electron beam is polarized transverse to its momentum," explains Tyler. SSAs arise from the interaction between the electron dipole moment and target magnetic field during the electron scattering process. Since this effect cannot occur for the exchange of a single photon, SSAs are directly sensi-tive to multi-photon exchange. The role of TPE in electron scattering has received considerable attention in both the theoretical and experimental nuclear physics communities in an effort to understand its connection to hadron structure. “Determining how to best take advantage of MESA’s unique capabilities to measure SSAs is one of my first projects here in Mainz."
Strong international collaboration
Additionally, Tyler is paving the way for strong international collaboration between JGU and the Electron-Ion Collider (EIC), a new facility to be built at Brookhaven National Laboratory. "With high-energy electron-ion collisions, we can study the properties of the quarks and gluons within hadrons. I have been very active in this project and am excited to stay involved in the future." The EIC is a successor to the Hadron-Electron Ring Accelerator (HERA), a lepton-proton collider in operation at DESY in Hamburg until 2007, whose data are still leading to new discoveries. While the EIC will have a lower maximum center of mass energy than HERA, it will achieve higher luminosities, enable electron-nucleus collisions, and cover a wider phase space of polarized collisions. The EIC is expected to be operational by the mid-2030s, and will allow fully polarized collisions with energies up to 18 GeV for electrons and up to 275 GeV for protons.
The hadron beam can also consist of complex nuclei, from light elements such as deuterium and helium, to heavy elements such as lead. "I am excited about extending measurements to heavy nuclei where the nuclear parton distribution functions are highly modified compared to lighter nuclei or free nucleons. This extension could provide valuable insights into nuclear dynamics.”
Another major focus of Tyler's EIC research is double-spin asymmetry measurements, which are sensitive to the spin orientation of the quarks in the target. Such measurements have the potential to solve the proton spin puzzle – a long-standing question in nuclear physics. The EIC is expected to provide critical constraints on the proton spin composition, particularly at low momentum fractions where the contribution from gluons is expected to be large.
Tyler is thrilled to return to Mainz as a professor. "In the US, one of my options was applying to jobs at a national laboratory such as JLab, which offers the advantage of working on-site with the accelerator. But I have always preferred the university environment, and I enjoy teaching," concludes Tyler. "MESA offers a unique opportunity to have access to a cutting-edge electron accelerator for nuclear physics experiments, on a university campus. There are very few other places that offer that, with infrastructure and research of this caliber."