Bulletin of the American Physical Society
2013 Annual Meeting of the California-Nevada Section of the APS
Volume 58, Number 14
Friday–Saturday, November 1–2, 2013; Rohnert Park, California
Session H3: Nuclear Physics |
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Chair: Benjamin Wang, Stanford University Room: Darwin 37 |
Saturday, November 2, 2013 2:00PM - 2:12PM |
H3.00001: Rapidity Dependent Pion Spectra from Fixed-Target $\sqrt{s_{NN}} =$ 3.0, 3.5, and 4.5 GeV Au$+$Al Collisions at STAR Brooke Haag The STAR detector at RHIC can study fixed-target Au$+$Al collisions resulting from the beam halo interacting with the beam pipe. Utilizing these data, STAR can extend the reach of the beam energy scan to lower center-of-mass energies and higher baryon chemical potentials than previously considered. This allows for a more thorough search for the possible onset of deconfinement of the phase transition between hadronic and partonic matter. In this talk, we discuss analysis details including the fixed-target acceptance and efficiency of the STAR detector. In addition we will present rapidity dependent fixed-target pion spectra from each of three Au$+$Al datasets at center-of-mass energies of 4.5, 3.5, and 3.0 GeV. [Preview Abstract] |
Saturday, November 2, 2013 2:12PM - 2:24PM |
H3.00002: Angular Correlations of High-pT Hadrons in PbPb and pp Simulations Gabriel Bonilla The quark-gluon plasma has a role in understanding the strong force, which is described by the theory of quantum chromodynamics. To probe the quark-gluon plasma, heavy ions are collided at high energies to recreate the conditions present in the early universe. Experiments like the Compact Muon Solenoid (CMS) at the Large Hadron Collider examine the results of colliding heavy nuclei together at high energies to recreate the quark gluon plasma. One such observation is jet quenching, which is believed to occur when the jets of particles produced in the collision interact with the plasma and lose energy. In this project, we use the HYDJET (Hydrodynamics plus Jets) program to simulate the jet quenching effects. The simulated HYDJET results will be cross-referenced with the real results from the CMS experiment in order to achieve a deeper theoretical understanding of the quark gluon plasma. In particular, we will look at the angular correlations of the jets of particles created in such an event. We will look to see how these angular correlations behave as a function of centrality and transverse momentum to help us understand the mechanisms of energy loss. [Preview Abstract] |
Saturday, November 2, 2013 2:24PM - 2:36PM |
H3.00003: Analysis of Z$+$jet Simulations in Pythia and Fastjet pp at $\sqrt{sNN}$ = 7 TeV Chadwick Rainbolt The focus of this research is to simulate Z$^{\mathrm{0}}+$jet events with the Pythia event generator. Pythia can yield the final state particles of a pp interaction. Pythia simulates an event and stores all of the information of each particle involved. Those particles can be entered into Fastjet, which is an algorithm made to cluster hadrons into jets, which correlate to the momentum of quarks and gluons. The Pythia analysis finds the leading quark in the pp simulation. Since quarks cannot exist in free space, the leading quark breaks off into many stable hadrons. This hadronization produces particles that have similar momenta, which look like a jet. Fastjet clusters the particles together in an attempt to estimate the original momenta of the quarks and gluons. The Pythia quark momentum and one of the Fastjet jets should be similar. Comparing these two can determine how accurately the Fastjet algorithm is at finding jets. The p$_{\mathrm{T}}$ of the found jet will then be compared to the p$_{\mathrm{T}}$ of the opposing Z$^{\mathrm{0}}$. To leading order, both of these p$_{\mathrm{T}}$'s should balance. This kind of study is useful to estimate the energy of quarks in Z$^{\mathrm{0}}+$jet events in heavy-ion collisions. [Preview Abstract] |
Saturday, November 2, 2013 2:36PM - 2:48PM |
H3.00004: Monte-Carlo Glauber model simulations of nuclear interactions Mikhail Miller, Chad Rexrode In order to understand the geometry of nuclear collisions, we created an iPython-based simulation of the Monte-Carlo Glauber model. The simulation utilizes a Woods-Saxon density distribution for the nuclei and cross-section data from the Particle Data Group to generate large samples of nuclear collisions. The results are analyzed to correlate the number of participating nucleons and binary collisions with the impact parameter of the events. Individual simulated collisions can be visually represented, demonstrating the event-by-event variation of the specific geometric overlaps, which are obscured in the ensemble data. [Preview Abstract] |
Saturday, November 2, 2013 2:48PM - 3:00PM |
H3.00005: Nucleon Neutral Weak Form Factors from AdS/QCD Correspondence Mark Lohmann, Prashanth Jaikumar The Anti-de Sitter/Conformal Field Theory (AdS/CFT) correspondence is an exact correspondence between a 4-dimensional supersymmetric Yang-Mills theory and a theory of quantum gravity in a 5-dimensional AdS space. This correspondence allows one to perform non-perturbative calculations of conformal field theories and has been used to accurately describe aspects of the Quark Gluon Plasma. In order to use this theory to perform non-perturbative Quantum Chromodynamics (QCD) calculations, the conformal symmetry of the AdS metric needs to be broken with either hard wall model which imposes a cutoff at the ultraviolet and inferred energy limits, or a soft wall model in which the AdS metric is multiplied by a dilaton field. This is known as the AdS/QCD correspondence and this approach has been used to calculate Reggie trajectories, form factors, and many other properties of QCD. Using the AdS/QCD correspondence in light front coordinates we attempt to calculate the Dirac and Pauli form factors, F$^{\mathrm{Z}}_{1}$(Q$^{2})$ and F$^{\mathrm{Z}}_{2}$(Q$^{2})$, for the neutral weak charge of both the proton and neutron. This will allow us to access the weak form-factor of nucleons in a non-perturbative regime. [Preview Abstract] |
Saturday, November 2, 2013 3:00PM - 3:12PM |
H3.00006: ClaRA: The CLAS12 Reconstruction and Analysis framework Eddie Banulos-Casillas, John Price, Dennis Weygand, Johann Goetz, Vardan Gyurjyan, Sebasti\'an Mancilla Like most modern nuclear physics experiments, the CLAS experiment at the Thomas Jefferson National Accelerator Facility (JLab) needs to deal with extremely high data rates; at CLAS, they can be as high as approximately one terabyte per day. The upgrade of the accelerator energy, and the upgrade of the CLAS detector necessitated by it, will increase the data rate by approximately a factor of five, making it even more important than ever to implement efficient data reconstruction and analysis techniques. Cloud computing provides an efficient and economically feasible way to handle such a large amount of data. A Beowulf cluster is a common type of setup for such a purpose; it uses many similar computers, all connected to each other, performing a task in unison. At the CSUDH Hadronic Structure Laboratory (HadLab), we have built a 44-node Beowulf-like computer cluster operating a Linux distribution of Rocks Cluster which is based on CentOS. All of the computers in the HadLab cluster are recycled, mostly from computer labs on campus, to reduce the overall cost of the cluster; two of the HadLab nodes perform administrative functions, while the rest perform the calculations done by the cluster. The software used for this work is the CLAS12 Reconstruction and Analysis framework (ClaRA), a service-oriented architecture in which data processing algorithms filter continuously flowing data. This talk will present the motivation behind the ClaRA framework, and will discuss the current status of the development project. [Preview Abstract] |
Saturday, November 2, 2013 3:12PM - 3:24PM |
H3.00007: Construction of the CLAS12 High-Threshold Cerenkov Counter Dylan Nicholas, John Price, Youri Sharabian As part of the general upgrade of the CLAS detector at the Thomas Jefferson National Accelerator Facility in Newport News, VA, the electron-identification system is being updated. A new subsystem, the CLAS12 High-Threshold \v{C}erenkov Counter (HTCC) is being built for this purpose. The HTCC, together with the existing Low-Threshold \v{C}erenkov Counter (LTCC) is designed to provide highly efficient electron detection as well as the possibility to positively identify pions. The HTCC will use CO$_2$ (index of refraction = 1.00045) as a radiator, giving it the ability to reject pions up to 5 GeV/$c$. Much of the preparatory work for the design of this device has been completed, and the construction is underway. There were three main tasks related to the construction this past summer. First, the largest single task involved the construction of the containment vessel of the HTCC, providing the superstructure for the detector. Second, the mirrors for the HTCC were assembled and tested. Third, the reflectivity of the Winston Cones, an integral part of the light collection system for the HTCC, was tested. This talk will introduce the design parameters for the upgrade of the HTCC, and will present the status of the work thus far. [Preview Abstract] |
Saturday, November 2, 2013 3:24PM - 3:36PM |
H3.00008: Three-dimensional pattern recognition of particle trajectories in hexagonal geometry drift detectors John Van Atta Nuclear fission events in the NIFFTE experiment's Time Projection Chamber emit multiple particles of varying type and momenta that leave ionization trails in the drift volume. Hexagonal charge sensors on the detector's pad planes record signals from the daughter particles. We present a program that employs a 3-dimensional gradient edge finder to reconstruct distinct particle trajectories from the raw sensor data of these fission events. The program calculates and displays the individual particle paths and reports the track-finding efficiency. Several possible upgrade features will also be discussed. [Preview Abstract] |
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