Bulletin of the American Physical Society
6th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Sunday–Friday, November 26–December 1 2023; Hawaii, the Big Island
Session 3WGB: When Color meets Gravity: Gravitational Form Factors of the Nucleon IIInvited Workshop
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Chair: Shunzo Kumano, Japan Women's University / KEK Room: Hilton Waikoloa Village Queens 6 |
Monday, November 27, 2023 11:00AM - 11:30AM |
3WGB.00001: Perturbative QCD constraints on the gravitational form factors Invited Speaker: Kazuhiro Tanaka We discuss the gravitational form factors (GFFs) using the QCD constraints on the hadron matrix elements of the energy-momentum tensor Tμν. With those constraints taking into account the perturbation contributions, the asymptotic behaviors of the GFFs at large momentum transfers and the forward values of the GFFs at zero momentum transfer are discussed. In particular, the latter results are derived for the twist-four gravitational form factor for the quark as well as for the gluon, Cq,g, at NNLO QCD from the trace anomaly constraints. For this purpose, the QCD trace anomaly is attributed to the anomalies for each of the gauge-invariant quark part and gluon part of Tμν, and those anomalies are evaluated at the three loop order. For the nonperturbative matrix elements arising in the corresponding formulas, we use the present information from experiment and lattice QCD. We show quantitative results for the nucleon as well as for the pion, leading to a model-independent determination of the forward value of Cq,g. We also mention that the same framework based on the trace anomaly constraints also indicates quite different pattern in the mass structures between the nucleon and the pion. |
Monday, November 27, 2023 11:30AM - 12:00PM |
3WGB.00002: Measurement of the gravitational form factors at J-PARC Invited Speaker: Shinya Sawada The Japan Proton Accelerator Research Complex, J-PARC, is a high-intensity proton accelerator facility, with the Materials and Life science Facility, the Neutrino Experimental Facility, and the Hadron Experimental Facility. The Hadron Experimental Facility utilizes the 30-GeV proton beams from the accelerator. The intense 30-GeV proton beams are injected into the production target, and the secondary beams, such as kaons, pions. Currently, strangeness nuclear physics experiments are a major activity with the low momentum (1 - 2 GeV/c) charged kaons and pions. Neutral kaons are used for a Kaon rare decay experiment. Alternatively, 8-GeV proton beams are used for a muon-to-electron conversion experiment. In addition, there is a high-momentum beamline, which is used for low-intensity 30-GeV proton beam experiments. There is an idea to upgrade this high-momentum beam line for high-momentum secondary beams. Once 10 or 20 GeV/c pions become available, physics cases will be greatly expanded. An experiment has been proposed to use these high-momentum pion beams to carry out charmed baryon spectroscopy. In the experiment, high-momentum negative pions will be used to pruduce charmed baryons with (pi, D^(*-)) reactions. A large acceptance spectrometer to detect D^(*-) will be constructed. In addition, a Letter of Intent has been submitted, which intend to investigate generalized parton distributions and pion distribution functions with the exclusive pion-induced Drell-Yan process. This LoI proposes an addition of detectors to the spectrometer used for the charmed baryon spectroscopy. This kind of studies will lead to an understanding of gravitational form factors. |
Monday, November 27, 2023 12:00PM - 12:30PM |
3WGB.00003: Measurement of the gravitational form factors at Belle Invited Speaker: Masataka Masuda Three dimensional tomography for hadrons has developed recently by using generalized parton distributions and generalized distribution amplitudes. This development makes us possible to study gravitational form factors for hadrons experimentally. We have measured differential cross section of pi0 pair production in single-tag two-photon collisions, gamma*gamma→pi0pi0, based on a data sample of 759 fb-1 collected with the Belle detector at the KEKB asymmetric-energy e+e− collider. Two types of gravitational form factors which indicate mechanical distributions and gravitational mass distributions are extracted from the Belle data and converted to the corresponding gravitational radii for a pion. I would like to talk about the analysis and future prospects of gravitational pion radii. |
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