Nuclear Physics Seminars

The MUonE experiment proposes a novel approach to determine the leading hadronic contribution to the muon g-2, from a precise measurement of the differential cross section of the $\mu e$ elastic scattering, achievable by using the CERN SPS muon beam onto atomic electrons of a light target.

The detector layout is modular, consisting of an array of identical tracking stations, each one made of a light target and silicon strip planes, followed by an electromagnetic calorimeter made of $PbWO_{4}$ crystals with APD readout, placed after the last station, and a muon filter. The scattering particles are tracked without any magnetic field, and the event kinematics can be defined in a large phase space region from the expected correlation of the outgoing particle angles. The ambiguity affecting a specific region, with electron and muon outgoing with similar deflection angles, can be solved by identifying the electron track as the one with extrapolation matching the calorimeter cluster or the muon track by associating it to hits in the muon filter. The role of the calorimeter will be important for background estimate and reduction, and to assess systematic errors, providing some useful redundancy and allowing for alternative selections.

Beam tests are carried out at CERN with a prototype calorimeter to determine its calibration with both high energy ($20-150 GeV$) and low energy electrons ($1-10 GeV$). In late summer a pilot run is scheduled with up to three tracking stations and the calorimeter integrated within a common triggerless readout system. The main motivations for the MUonE calorimeter are discussed, and the status and first performance results will be presented.

The Large Hadron Collider beauty (LHCb) experiment provides an opportunity to study hadronization processes, how particular hadrons are formed from scattered quarks and gluons (partons), in the forward region. Going beyond traditional collinear non-perturbative fragmentation functions (FFs), transverse-momentum-dependent (TMD) FFs provide multidimensional information on the hadronization process. The excellent hadron identification capabilities LHCb allows for a wealth of possible hadronization measurements. Recent results measuring TMD jet FFs for identified charged pions, kaons, and protons in a predominantly light quark jet sample will be presented. Ongoing measurements of TMD hadronization in heavy-flavor-tagged jets as well as hyperon transverse polarization will additionally be discussed.

Whether neutrinos are Majorana or Dirac particles is an open question. Theoretically, it is also possible that neutrinos are pseudo-Dirac, which are fundamentally Majorana fermions, but essentially act like Dirac fermions in most experimental settings, due to extremely small active-sterile mass splitting. Such small values of mass splitting can only be accessed via active-sterile oscillations over an astrophysical baseline, or via decays of neutrinos over a cosmological time scale. In this talk, I will use the multi-messenger observation of high-energy neutrino sources and the excess radio background detection to probe two different regimes of pseudo-Dirac neutrino parameter space. 

"For a long time, it was believed that the fundamental constituents of atoms were electrons and nucleons until experiments conducted in the late 1960s at Standford Linear Accelerator Center (SLAC) proved the existence of internal degrees of freedom in the nucleons. These ones are called quarks and gluons, or collectively partons. With QCD as the fundamental theory for strong interactions, we can describe hadronic structure via correlators of partons giving rise to the so-called parton distribution functions (PDFs) and generalized parton distributions (GPDs) when the so-called collinear factorization applies. The non-elementary nature of hadrons makes these correlators perturbatively unsolvable so we can only measure or model them. 

This seminar will cover the discovery of the proton as a composite object through deep inelastic scattering (DIS), from both the experimental and theoretical sides. Modern experiments/theory on other processes such as deeply virtual, timelike and double deeply virtual Compton scattering (DVCS, TCS and DDVCS) will be covered too, giving a broad picture on the current access to parton distributions."

This talk presents an exploration of meson structure studies using the Sullivan process, which provides valuable insights into the fundamental nature of hadrons within the framework of Quantum ChromoDynamics (QCD).  The primary focus is on pion and kaon structures, offering unique opportunities for enhancing understanding of the emergent hadron mass-generating mechanism (EHM) and Generalized Parton Distributions (GPDs).

The KaonLT experiment, conducted in Hall C at Jefferson Lab (Jlab), employs a methodology comprising detector calibrations, efficiency studies, and offsets optimizations. These steps lead to the extraction of the kaon electroproduction cross section and the crucial separation of longitudinal and transverse components which, when warranted by the data, allow for kaon form factor extraction.

In addition to the Jlab efforts, ongoing research includes GEANT4 detector simulations to investigate the necessary requirements for measuring pion and kaon structure functions at the forthcoming Electron-Ion Collider (EIC). These investigations contribute significantly to constraining meson Parton Distribution Functions (PDFs) and validating the behavior of valence quark, sea quark, and gluon distributions.

Lymphocytes are a key component of the adaptive immune system. The presence of high numbers of lymphocytes, especially T cells, has been reported to be an indicator of good prognosis in many types of cancer. However, lymphocytes are highly radiosensitive and Radiation-Induced Immune Suppression (RIIS) means destroying existing as well as newly created lymphocytes. In the era of immunotherapy, predicting time-dependent immune levels could allow optimum time for immunotherapy administration. In this talk, I will present a comprehensive model to predict time-dependent absolute lymphocyte count (ALC) in blood for early-stage lung cancer patients following Stereotactic Body Radiation Therapy (SBRT) treatment. This complex model includes blood circulation among blood-rich organs such as heart, aorta, vena cava, pulmonary artery, etc; intertwined with lymphatic circulation among lymph-rich organs such as spleen, bone marrow, lymph nodes, liver, lung, etc. The model was trained on a set of retrospective lung SBRT patients and tested on a set of ongoing clinical trial patients. The model shows good accuracy in both training and testing datasets, with room for improvement.

In 1983, results published by the European Muon Collaboration (EMC) at CERN suggested that the quark structure of nucleons are modified when they are bound together in the nuclear environment. This modification, now called the EMC Effect, was largely unexpected and has been the subject of a significant amount of theoretical and experimental effort over the past 40 years to determine its underlying cause. Despite this effort, the exact mechanism that causes the EMC Effect has continued to elude physicists.

Experiment E12-10-008 at Jefferson Lab aims to shine a bright new light on this 40-year-old problem. Having collected data from September 2022 through February 2023, this experiment utilized the high luminosity 12 GeV electron beam of CEBAF to probe, with high precision, the quark structure of nearly 20 different nuclei. Data from this experiment will provide a significant contribution to the global set of EMC Effect data, producing the first measurements of the EMC Effect in many new nuclei and reducing uncertainty on previously studied nuclei. In this seminar, an overview of the EMC Effect will be given and the physics motivation of experiment E12-10-008 will be presented.

The constituents of dark matter are still unknown, and the viable possibilities span a very large mass range. Specific scenarios for a thermal origin of dark matter sharpen this mass range to within about an MeV to 100 TeV. Most of the stable constituents of known matter have masses in the MeV to GeV range, and a thermal origin for dark matter works in a simple and predictive manner in this mass range as well, yet it remains largely unexplored. The Heavy Photon Search (HPS) at Jefferson Lab is a fixed target experiment that uses an electron beam to probe models of thermal dark matter involving sub-GeV dark photons. HPS searches for visibly decaying dark photons through two distinct methods - a resonance search in the e+e- invariant mass distribution and a displaced vertex search for long-lived dark photons. This seminar will give an overview of the theoretical motivations, the main experimental challenges and how they are addressed, the results for the 2016 Engineering Run, and future data and upgrades. In addition, an introduction to the Light Dark Matter eXperiment (LDMX), a planned next generation experiment at SLAC that will search for invisibly decaying dark photons through a missing-momentum experiment, will be presented.