Bulletin of the American Physical Society
APS April Meeting 2021
Volume 66, Number 5
Saturday–Tuesday, April 17–20, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session D15: Light Mesons and BaryonsLive

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Sponsoring Units: GHP Chair: Astrid Hiller Blin, Jefferson Lab 
Saturday, April 17, 2021 1:30PM  1:42PM Live 
D15.00001: Pion formfactors from lattice: toward the continuum limit Peter Petreczky, Gao Xiang, Nikhil Karthik, Swagato Mukherjee, Sergey Syritsyn, Yong Zhao We will present lattice results in 2$+$1 flavor QCD on the pion formfactor in a wide range of momentum transfer using staggered sea quarks with improvedclover quarks in the valance sector. Our study uses three lattice spacings, a$=$0.076fm, 0.06fm, and 0.04fm, and two pion masses, a pion mass of about 300 MeV and the physical pion mass. This allows us to control the continuum limit as well as the quark mass effects. [Preview Abstract] 
Saturday, April 17, 2021 1:42PM  1:54PM Live 
D15.00002: Precision lattice calculation of the $x$dependence of pion valence PDF Yong Zhao, Xiang Gao, Swagato Mukherjee In this talk, we present a modelindependent calculation of the $x$dependence of pion valence PDF with the largemomentum effective theory approach. In this calculation we adopt the most uptodate theoretical developments on the systematic corrections, which include the hybrid renormalization scheme that rigorously renormalizes the lattice matrix elements at both short and long distances, as well as the inverted twoloop matching kernel that allows for extraction of the PDF without any model assumption. Therefore, we are able to make predictions for the PDF within a range of $x\in [x_{\rm min}, x_{\rm max}]$ where the systematic uncertainties are under control. This is a firm step towards the stage of precision calculation of both meson and nucleon PDFs. [Preview Abstract] 
Saturday, April 17, 2021 1:54PM  2:06PM Live 
D15.00003: Hybrid renormalization and its application to lattice determination of vector meson distribution amplitudes Jianhui Zhang Recent developments have shown that parton physics can be extracted from lattice QCD calculations of Euclidean correlation functions in a hadron with finite but large momentum. Such correlations involve both power and logarithmic divergences and thus need to be properly renormalized. In this talk, I'll discuss a hybrid renormalization scheme and its application to lattice calculations of vector meson distribution amplitudes. [Preview Abstract] 
Saturday, April 17, 2021 2:06PM  2:18PM Not Participating 
D15.00004: Double Polarization Observable $ E $ for $\gamma p \to \pi^0 p$ from JLAB CLAS Chan Kim To study baryon resonances, measurements of the double polarization observable E for $\gamma p\to\pi^0 p $ was performed using a circularly polarized photon beam on longitudinally polarized proton target (FROzen Spin Target experiment) at $ W $ energies between 1450 MeV and 2050 MeV. The final state particles were detected with CEBAF Large Acceptance Spectrometer (CLAS) in Hall B at the Thomas Jefferson National Accelerator Facility. The extracted data of helicity asymmetry E will be compared to the experimental results from CBELSA and partial wave analysis predictions from SAID, MAID, and BnGA. In certain energy and angle ranges, significant deviations from partial wave predictions were observed albeit in agreement with CBELSA results. Such discrepancies emphasize the need of further studies on polarization observables. In this talk, methods employed in the event selection, including machine learning techniques to control contaminated data, and preliminary results of helicity asymmetry E for $ \gamma p \to \pi^0 p $ will be presented. [Preview Abstract] 
Saturday, April 17, 2021 2:18PM  2:30PM Live 
D15.00005: Calibrating Pions with Deep Learning at the Atlas Detector at the Lhc Sylvia Mason Pions are produced more than any other particle at the LHC, so it is important that their energy is accurately calibrated in order to measure essentially any physics process at the LHC. Charged and neutral pions deposit energy via different mechanisms in the ATLAS detector, so their energy may be incorrectly measured in some cases. This project focused on utilizing deep learning techniques to correct the measured energy deposit to the true value, using image recognition techniques. Several variants of this imagebased regression technique are shown, and several significantly improve the energy reconstruction compared to baseline techniques. [Preview Abstract] 
Saturday, April 17, 2021 2:30PM  2:42PM Live 
D15.00006: An Easy Experiment to Solve an Old Puzzle Walton Perkins Although the pion and kaon have spin zero, many experiments in the 1950's and 1960's showed that the pion and kaon carry directional information (see Ref. [1]). The probability of statistical fluctuations causing the observed effect is less than 1 in a 1000 in several experiments by different researchers. The problem with these old experiments is that the researchers never varied a parameter and showed that the observed effect varied in a predictable manner. Recently, it has been shown theoretically, that massive vector particles with spin zero can exist[2]. These spin0 vector particles would be polarized along the direction of their creation, and a magnetic field cannot change that polarization direction. Thus, varying the angle between the polarization vector and the momentum of these charged particles using a magnetic field leads to a simple experimental test with predictable results. [1] W. A. Perkins, "PionMuon Asymmetry Revisted," Int. J. Theor. Phys\textbf{. 47} (2008) 1316. [2] W. A. Perkins, "Massive vector particles with spin zero," EPL (Europhysics Letters) \textbf{114} (2016) 41002. [Preview Abstract] 
Saturday, April 17, 2021 2:42PM  2:54PM Live 
D15.00007: Gluon pseudodistributions at short distances: Forward case Wayne Morris, Ian Balitsky, Anatoly Radyushkin We present the results that are necessary in the ongoing lattice calculations of the gluon parton distribution functions (PDFs) within the pseudoPDF approach. We give a classification of possible twogluon correlator functions and identify those that contain the invariant amplitude determining the gluon PDF in the lightcone $z^2\to0$ limit. Oneloop calculations have been performed in the coordinate representation and in an explicitly gaugeinvariant form. We made an effort to separate ultraviolet (UV) and infrared (IR) sources of the $\ln(−z^2)$dependence at short distances $z^2$. The UV terms cancel in the reduced Ioffetime distribution (ITD), and we obtain the matching relation between the reduced ITD and the lightcone ITD. Using a kernel form, we get a direct connection between lattice data for the reduced ITD and the normalized gluon PDF. We also show that our results may be used for a rather straightforward calculation of the oneloop matching relations for quasiPDFs. [Preview Abstract] 
Saturday, April 17, 2021 2:54PM  3:06PM Live 
D15.00008: Searching for Dark Forces at ARIEL Ross Corliss In addition to cosmological motivations, anomalies in precision nuclear and atomic measurements have prompted standard model extensions in the form of Dark Photons or, more generically, a new forcecarrier. Experimental searches have probed the parameter spaces where the simplest models predict such particles, but so far no culprit has been found and the anomalies remain unexplained. The recent report of an anomaly in $^4$He transitions, joining a similar anomaly in $^8$Be, has heightened interest in a potential new particle near 17 MeV. To reconcile this with existing searches, the particle would need to be protophobic, and hence suppressed in hadronic production. Leptonic searches, such as production and decay in electronnucleus scattering, $eX\rightarrow eXA'\rightarrow eXee^+$ can test leptonic couplings directly. The DarkLight collaboration has proposed to mount such a search in the near future at TRIUMF's ARIEL accelerator, using asymmetric spectrometers to reconstruct candidate $e^+e^$ pairs, which could exhaust the preferred parameter space with a relatively short running time. I will briefly review of the physics involved and introduce this proposed experiment, as well as prospects to search for new, MeVscale forces beyond this anomaly region in the future. [Preview Abstract] 
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