Session D10: Undergraduate Research III

Measurement of the Structure of the Inner Tracking Detector of the CMS Experiment Using Nuclear Interactions

In order to improve detector simulations and identify any changes in the positions of the inactive elements, it is important to measure the location of material in the inner tracker system of the CMS detector at the LHC. Precise position measurements of the beam pipe, pixel shield, pixel support, and pixel support rails were made using secondary vertices that are reconstructed from hadronic interactions with nuclei in the detector material. The measurements used data from proton-proton collisions at a center-of-mass energy of 13 TeV recorded in 2015.   

Two-Dimensional Heavy-Ion Scattering using the PIQTr Model

Heavy-ion charged particle collisions have important applications in fields such as astrophysics, biophysics, and plasma physics, and from a fundamental standpoint, provide valuable information about the few-body problem. Current theoretical atomic collision models work well for electron projectiles, but heavy-ion projectiles continue to present a challenge for even the most advanaced models. To help address these challenges, we have developed the Path Integral Quantum Trajectory (PIQTr) model for the calculation of time-dependent wave functions. The method is numerically exact and has been successfully applied to particles moving in one dimension. These results show a favorable scaling in computational requirements as the mass of the projectile increases, and in general, the model has been shown to work well for heavy ions. We have now extended our method to charged particles moving in two dimensions. Here we present time-dependent numerical results for various different charged particles and discuss applications to heavy-ion atomic collisions.   

Tracing Quantum Trajectories using the PIQTr Model

The path integral technique is an alternative formulation of quantum mechanics that is based on a Lagrangian approach. In its exact form, it is completely equivalent to the Hamiltonian-based Schr\"{o}dinger equation approach. We have used the path integral formalism to develop our Path Integral Quantum Trajectory (PIQTr) model for use in the study of charged particle dynamics. We will present results for several one-dimensional systems, and demonstrate the method's ability to analyze individual trajectories and their influence on the total probability amplitude. We will also show how the range of included trajectories can affect the time evolution of the wave function, resulting in interference fringes reminiscent of those observed with single slit Fresnel diffraction.   

b Track Jets’ Number Identification in Graviton Searching Research with the ATLAS detector, G→hh→bb¯ττ¯ Channel

We will discuss novel techniques to search for Gravitons decaying to $G$ $\rightarrow$ $hh$ $\rightarrow$ $bb$ $^-$ $\tau \tau$ $^-$ at the Large Hadron Collider in $pp$ collisions at $\sqrt{s}=$ 13 TeV with the ATLAS detector. The b track jets’ (the b jets detected by the ATLAS inner detector) pointing directions gives us a clue about identifying $G$ $\rightarrow$ $hh$ $\rightarrow$ $bb$ $^-$ $\tau \tau$ $^-$ signal. The new analysis technique utilizes the number of b track jets which are pointing to the fat jets to classify Graviton’s simulations. We demonstrated the number of the b track jets depending on the various Graviton’s simulated masses. The simulation results show that Graviton mass 2250 GeV is the critical mass point. Different simulations should be used for Graviton heavier and lighter than 2250 GeV. This approached improved the agreement between data and simulations by an order of magnitude. In addition, different preselections on b jets’ Pt, phi, R, and BDT score are applied on the simulation to find the better agreement.   

Shower Classification in the GlueX Experiment

The GlueX forward calorimeter is an array of 2800 lead glass modules that was constructed to detect photons produced in the decays of hadrons. We applied machine learning techniques to the classification of particle interactions in this calorimeter. These signals can be classified as either true electromagnetic “showers”, produced by photons, or background originating from charged particles or noise. To train and test the algorithms, we used reconstructed $\omega$ meson events which contain both true photons and charged particles that interact with the calorimeter. Different attributes of particle showers in the calorimeter (energy distribution, shower width, etc.) were used as distinguishing variables in training the machine learning algorithms. The selected data were used to optimize nine different types of machine learning algorithms to determine which would give the most effective final classifications between true and false photon showers. Algorithms were evaluated on efficiency, rate of false positives, runtime, and implementation complexity. The optimal method utilized was a multilayer perceptron algorithm with a signal efficiency of 94\% for a background rejection rate of 90\%.   

Factorization and Next to Leading Order Corrections in the Dipole QCD Model

The Baitsky-Kovchegov (BK) equation governs the energy amplitude of a virtual photon in a Deep Inelastic Scattering or gluon distrobutions. In most studies of a purely deterministic model, one assumes that the Next-to-Leading order correction in Light Cone Perturbation theory of the dynamics of the system behaves as a simple case of a doubling of the Leading order correction, corresponding to a $x^{-2} \ln^{-2}{x}$ supression of the correction. This correction is assumed to be true at low momenta of the virtual photon, but is expected to be not fully correct at high momenta. In this limit, one must consider delays in particle decay, leading to the stochastic model and changing the suppression to a $ \ln^{-2}{x}$ dependence.   

Conformal Gravity Approach to the SPARC Dataset

The SPARC database (Spitzer Photometry and Accurate Rotation Curves) is a diverse set of 175 galaxies with reliable, well studied rotation curve data. Recently, Conformal Gravity (CG) has fit the remainder of the SPARC database galaxies, encompassing 30 galaxies not previously studied by CG. Adding these 30 galaxies to the list of galaxies modeled by CG furthers the assertion that CG not only successfully fits galaxies but it does so universally. The greatest notable difference between CG and other alternative theories of gravitation is the fact that CG is a fourth order theory that is a completely re-normalizable, metric theory of gravity. The quadratic potential present in CG allows the rotation curves to neither infinitely rise nor remain forever flat. In this work, we show how these 30 galaxies can be fit by CG without the need for dark matter and now brings the theory to over 250 galaxies fit in a universal manner.   

Competing Ideas in Quantum Measurement: The Search for a Perfect ``Theory of Everything''

Since the quantum revolution in the early 20th century, finding the "perfect" theory to completely describe the universe at the subatomic scale drove some of the greatest minds in modern physics. We study quantum non-locality theory using de Broglie-Bohm Pilot Wave Theory as a model hidden variable theory and Bell's Theorem as a model quantum measurement inequality to understand the fundamental theoretical challenges posed by quantum entanglement and contextuality. Controversial claims of a supposed "disproof of Bell's Theorem'' using Clifford algebra-valued local hidden variables is investigated through mathematical and computational methods. We compare results to the expected predictions of Bell's Theorem and the Copenhagen interpretation of quantum mechanics.