Speaker: Tanja Horn (Catholic University of America)

Title: Pion and kaon structure functions 

Abstract: Pions and kaons are, along with protons and neutrons, the main building blocks of nuclear matter. They are connected to the Goldstone modes of dynamical chiral symmetry breaking, and appear to be key to the further understanding of the mechanisms that generate all hadron mass in the visible universe. The distribution of the fundamental constituents, the quarks and gluons, is expected to be different in pions, kaons, and nucleons. However, experimental data are sparse. As a result, there has been persistent doubt about the behavior of the pion's valence quark structure function at large Bjorken-x and virtually nothing is known about the contribution of gluons. Experiments at the 12 GeV JLab using hard scattering from the virtual meson of the nucleon will shed light on this by providing information on how emergent mass manifests in the wave function and about the quark-gluon momentum fractions. The Electron-Ion Collider (EIC) with an acceptance optimized for forward physics will enable a revolution in our ability to study pion and kaon structure. The unique experimental facilities at the EIC will provide access to structure functions over a wide range of kinematics. This would allow for measurements testing if the origin of mass is encoded in the differences of gluons in pions, kaons, and nucleons, and measurements that could serve as a test of assumptions used in the extraction of structure functions and the pion and kaon form factors. Measurements at an EIC would also allow to explore the effect of gluons at high x. In this talk we will discuss the status of measurements at Jefferson Lab and prospects of such measurements at the EIC.

Short Bio: Tanja Horn is Professor of Physics at The Catholic University of America (CUA). Her research in medium energy nuclear physics and applications focuses in the near and intermediate term on Jefferson Lab 12 GeV and in the long term on the US-based Electron-Ion Collider (EIC). She has been spearheading the science direction of meson structure and experimental validation of femtography, and also detector efforts in all experimental halls at Jefferson Lab. She is leading the Neutral Particle Spectrometer Collaboration consisting of about 50 people and is spokesperson for five Jefferson Lab experiments, each consisting of 50-100 people. She has been actively involved for over a decade in the design and science of the EIC. Early on she was part of the steering committee of the EIC white paper, where she co-led the detector section, in addition to developing some of the science case. More recently she was one of four conveners worldwide leading the EEIC Yellow Report Detector Working Group and is now a member of the Steering Committee for the ECCE EIC Detector Proposal. Prof. Horn has been pioneering initiatives in autonomous optimization of detectors in nuclear physics with Artificial Intelligence (AI) with particular focus on design and streaming. She has represented the Nuclear Science Advisory Committee in the 2020 DOE SC cross-examination to identify scientific opportunities and challenges from the intersection of AI with data-intensive science such as Nuclear Physics. Prof Horn started up a small business in 2016 and has been leading six technology transfer projects for the development of novel materials for detectors at Jefferson Lab and EIC supported by the DOE Small Business program. Prof. Horn has chaired multiple international workshops and conferences, including the recent EIC User Group Meeting, and has over 50 publications in refereed journals on a variety of topics in medium energy nuclear physics. She has mentored 23 high school and undergraduate, 6 graduate students, and 3 postdoctoral researchers. Prof. Horn received a PhD in physics from the University of Maryland in 2006, and was a postdoctoral fellow at Jefferson Lab before joining the faculty at CUA in 2009. She holds a joint position with Jefferson Lab since 2011.