Fall 2017

The wealth of research opportunities available in LNS can be confusing and overwhelming, especially for new graduate students. In this special introductory talk we’ll come together to try to make sense of it all.

The COMSOL Multiphysics now become a widely used solver package with finite element method in science and engineering. Due to its versatility like in fluid, structural, chemical, E&M and so on, someone(not me!) expected that the LNS should operate a group license for the software so that we can simulate our targets and detectors easily. In this talk, I'm going to show you how it works, why I'm using this black box software, and which advantages and disadvantages it contains in order to help your decision making. To make it not too boring, I'm introducing a little bit about the aim of DarkLight experiment-i.e. what the dark photon is. Oops, sorry if you find that part more boring. I hope to see all of you there!

Since its discovery over 30 years ago, understanding the EMC effect remains a large focus, with no generally accepted model to date. Recently, there have been indications, experimentally and theoretically, that the EMC effect may be linked to high-momentum nucleons. If a nucleon in such a highly virtual state has structure functions which are modified, even to a modest degree, then it may explain the EMC effect. BAND (Backward Angle Neutron Detector) is a future experiment in 2018 at Jefferson Lab Hall B to search for medium-modification in high-momentum nucleons. By using a method of spectator-tagging, one can be sure of selecting deep-inelastic scattering events on these highly virtual nucleons. In my talk, I will present the EMC effect, discuss its possible connection to high momentum nucleons, and briefly describe how BAND will select on these nucleons (spectator-tagging) and then extract medium-modification effects. Finally, I will present the work that I’ve done using a Geant4 simulation of Hall B, some studies we’ve done in the lab to select detector component models, and preparation for the construction of the BAND array in Jan 2018.

The electromagnetic form factors of the proton are fundamental quantities defined in the context of one-photon exchange. The measurement of the elastic electron-proton cross section is a standard method for extracting information about the proton form factors. In this talk, I will discuss the details of how a cross-section can be determined using a high-resolution, small-acceptance spectrometer. I will focus on the GMp experiment performed in Hall A at Jefferson Lab, which measured the elastic electron-proton cross section in the Q^2 range of 7-14 GeV^2. Lastly, I will consider recent attempts to understand the apparent discrepancy between the elastic cross section and the recoil polarization results.

Calculating a process to leading order is typically only enough for a basic analysis. “Radiative corrections” is the general term for going beyond leading order. This is a tricky and unsettling process for even the simplest things, e.g. electron-electron scattering. In this talk, we’ll go through a day in the life of two electrons, and all of the chaos that follows.

Counting experiments are everywhere in physics, and are a fundamental component of nearly every experimental particle physics collaboration. One of the main issues universal to all counting experiments is accounting for the efficiency of the detector. An imperfect detector efficiency alters the higher moments of a particle multiplicity distribution in nontrivial ways, and current methods of recovering such moments are computationally expensive and/or inaccurate. Fortunately, there exists a method to reliably reconstruct the true multiplicity distribution that, for certain experimental parameters, is not only simpler, but also more accurate in recovering higher moments. I will present this method, along with its limitations and a few applications.

A search for new physics in events with a Z boson produced in association with large missing transverse momentum at the LHC is presented. The search is based on the 2016 data sample of proton-proton collisions recorded with the CMS experiment at sqrt(s) = 13 TeV, corresponding to an integrated luminosity of 35.9 inverse femtobarns. The results of this search are interpreted in terms of a simplified model of dark matter production via spin-0 or spin-1 mediators, a scenario with a standard-model-like Higgs boson produced in association with the Z boson and decaying invisibly, a model of unparticle production, and a model with large extra spatial dimensions.

Rey's Topic: Motivations for and experimental constraints on hidden sector dark matter

Tom's Topic: Goals and status of neutrinoless double beta decay searches

AMS-02 experiment is the only magnetic spectrometer in space. It has been collecting cosmic ray data for more than six years and will continue collecting until the International Space State retires from its legendary mission(scheduled in 2024 but now rumor to extend to 2028). I'm going to talk about a method I have developed to improve the charge resolution in AMS tracker. With large statistics, we can measure cosmic ray flux up to iron. Since I came back from CERN to take the Oral in the beginning of next month. I would be happy to take any related question about AMS or unrelated questions for an oral practice if time permits.

Topic: PDFs, gluon saturation, and the EMC Effect

Radiologists routinely use contrast-enhanced MRI with applications mainly in oncology and abdominal imaging. Over the last decade, researchers have put significant efforts in developing new probes for molecular imaging where contrast agents would target only specific cells and/or regions. In all cases, one main question remains: what is the potential toxicity of this new contrast agent? We propose here a safe approach to contrast-enhanced MRI, using pre-polarized biocompatible saline combined with imaging at ultra-low field (0.0065 T).

Jet quenching in heavy-ion collisions is one of the tools to study the hot QCD matter. Electroweak boson+jet correlations is the golden channel for this probe. There were two lunchtime seminars this semester showing the results from photon+jet and Z+jet correlations at the LHC. This talk will first give a recap of experimental results. Then it will ask what gives rise to the shape of the momentum imbalance distribution (main boson+jet observable for jet quenching), which is wide even in proton-proton collisions. Some MC exercises on photon+jet observables in pp collisions will be shown. These exercises aim to address how the simulated physics processes can explain what we see in data.

Why does the Standard Model not include right-handed neutrinos? One proposed resolution to this seemingly hopeless situation is the existence of a massive "sterile neutrino" which does not couple to the weak interaction. Originally invoked in the seesaw mechanism to generate the masses of the three known (left-handed) neutrinos or to account for baryon asymmetry, keV-scale sterile neutrinos have also become an attractive dark matter candidate. In this talk, I will discuss the consistency of sterile neutrino dark matter with astrophysical constraints from Big Bang nucleosynthesis and cosmological structure formation, as well as recent searches for radiative sterile neutrino decay using the NuSTAR x-ray observatory.