Toshimi Suda,, Research Center for Accelerator and Radioisotope Science (RARiS), Tohoku University
[KEK-JAEA Joint Seminar] Proton Charge Radius
Hybrid On-site: KEK Tokai Bldg1 room 116 Online: Zoom The “Proton Radius Puzzle,” initiated by the 2010 muonic hydrogen measurement, highlighted a significant discrepancy (about 7\sigma) with respect to values derived from electron scattering and ordinary hydrogen spectroscopy. While recent measurements, such as the PRad experiment at JLab and some of updated hydrogen spectroscopies, look to favor a smaller proton charge radius, consistent with the muonic result, inconsistencies with earlier electron scattering data remain unresolved. In addition, discrepancies among recent 1S–3S transition hydrogen spectroscopy resultsn suggest the presence of unquoted systematic uncertainties. Consequently, a precise determination of the proton charge radius is still critical to resolve this long-standing issue.
The “Proton Radius Puzzle,” initiated by the 2010 muonic hydrogen measurement, highlighted a significant discrepancy (about 7\sigma) with respect to values derived from electron scattering and ordinary hydrogen spectroscopy. While recent measurements, such as the PRad experiment at JLab and some of updated hydrogen spectroscopies, look to favor a smaller proton charge radius, consistent with the muonic result, inconsistencies with earlier electron scattering data remain unresolved. In addition, discrepancies among recent 1S–3S transition hydrogen spectroscopy resultsn suggest the presence of unquoted systematic uncertainties. Consequently, a precise determination of the proton charge radius is still critical to resolve this long-standing issue.
In this seminar, I will report on the current status of our ULQ2 (Ultra-Low Q2) project at the Research Center for Accelerator and Radioisotope Science (RARiS; former ELPH), Tohoku University. Utilizing a 60-MeV electron linac, we have measured the elastic electron–proton scattering cross section in the lowest-ever momentum transfer region, Q^2 = 0.0003–0.008 (GeV/c)^2. A key feature of this project is an absolute cross-section measurement relative to the well-known ^{12}C cross section using a CH_2 target, aiming to control systematic uncertainties at the 10^{-3} level. This approach is expected to provide the least model-dependent determination of the proton charge radius from electron scattering.
In addition to the proton measurement, we have also performed elastic electron–deuteron scattering measurement under the same kinematics, providing the world’s lowest-Q^2 data for the deuteron. A puzzle similar to that of the proton has been pointed out, and our measurement enables a determination of the deuteron charge radius. From this e+d data, we are challenging the determination of the neutron charge radius via electron scattering for the first time by exploiting the fourth moments of the deuteron charge distribution.
I will first review the current status of the Proton Radius Puzzle and recent global experimental efforts. I will then present the details of the ULQ2 project, including the challenges for the neutron charge radius.
Mohammad Aghaie, Osaka U
Axion Dark Matter from Heavy Quarks
Hybrid On-site: Kenkyu Honkan Semiar room321 322 Online: Zoomid
We propose simple scenarios in which the observed dark matter abundance arises from decays and scatterings of heavy quarks through freeze-in production of an axion-like particle with a mass in the 10 keV–1 MeV range. These models can be tested by future X-ray telescopes and, in some cases, will be almost entirely probed by searches for two-body decays (K \to \pi + \text{invisible}) at NA62. As a byproduct, we discuss the cancellation of infrared divergences in flavor-violating scattering processes relevant for thermal axion production and derive the general contribution to the axion–photon coupling from all three light quarks.
Shuhei Minato, U of Tokyo
Impact of Higher-Order Color-Superconducting Gap Corrections on the Dense-Quark-Matter EoS
Hybrid On-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom
Recent astrophysical observations suggest that, inside neutron stars, the speed of sound and the trace anomaly may not follow a simple extrapolation from normal-phase quark matter. This possible discrepancy has drawn attention because it could provide observational signatures of color superconductivity. On the theory side, QCD becomes weakly coupled at sufficiently high density, so perturbative methods can be applied. Weak-coupling frameworks that include the color-superconducting gap are well established and allow systematic, order-by-order improvements. In this talk, I summarize current observational constraints on the equation of state, compare them with state-of-the-art theoretical predictions, and discuss whether color superconductivity can occur in neutron-star cores.
Sho Araki, Osaka University
The Arf–Brown–Kervaire (ABK) Invariant in Lattice Fermion Systems
Hybrid on-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom
Topological invariants in fermionic systems provide sharp probes of symmetry and anomaly. In this talk, we study how to formulate such a topological invariant that is valued in Z_8, known as the Arf-Brown-Kervaire (ABK) invariant, for the lattice fermion systems. The ABK invariant is a two-dimensional invariant that is encoded in the complex phase of the Majorana fermion partition function, and it plays a role analogous to topological terms such as the instanton number in 4D Dirac fermion settings. We employ massive Wilson Dirac operators and numerically demonstrate that the ABK invariant emarges on the partition function. To capture the ABK invariant fully, it is essential to consider various types of manifold including non-orientable ones such as the real projective plane and the Klein bottle. In addition, manifolds with boundaries are also important for understanding anomaly and anomaly inflow. We discuss how to realize the geometries of these manifolds on the lattice and verify numerically (and partly analytically) that our formulation reproduces the known values in continuum theory.
Stephen R. Sharpe, University of Washington
Three-particle scattering amplitudes from lattice QCD
Hybrid On-site: Seminar room 321, 322 Online: Zoom
I discuss recent progress in calculating scattering amplitudes and resonance properties involving three particles using lattice QCD results for the finite-volume spectrum, coupled with solutions to the associated integral equations. I describe the outlook for future extensions of this work.
Yu-ki Suzuki, YITP
Understanding de Sitter holography through quantum inequalities
Hybrid On-site: Kenkyu Honkan meeting room321 322 Online: Zoom
The dS/CFT correspondence was proposed more than two decades ago. However, to date, no fully controllable and universally accepted formulation of de Sitter holography has been established. Recently, a qualitatively different approach to de Sitter holography has been proposed, in which the dual quantum field theory is defined on a timelike boundary rather than on future or past infinity. In this seminar, we focus on this type of holographic models and demonstrate that they are subject to nontrivial constraints arising from holographic entanglement entropy inequalities, such as strong subadditivity.
Wei-Hsiang Shao, RIKEN
UV Physics and a New Perspective on Hawking Radiation
Hybrid On-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom Non-perturbative UV effects are believed to be essential for resolving the black hole information paradox. Yet, an equally important question is whether such effects could also largely alter Hawking radiation itself, the process that led to the paradox in the first place.
Non-perturbative UV effects are believed to be essential for resolving the black hole information paradox. Yet, an equally important question is whether such effects could also largely alter Hawking radiation itself, the process that led to the paradox in the first place.
In this talk, I will explore this possibility and discuss how UV physics can dramatically modify the standard properties of Hawking radiation predicted by low-energy effective field theory.
In particular, I will show that by incorporating nonlocal features inspired by string theory, Hawking radiation can become a transient phenomenon that is largely suppressed after the scrambling time, much earlier than the conventionally expected black hole lifetime. This suggests a major departure from the usual picture of black hole evaporation and may offer fresh insight into alternative resolutions of the information paradox.
Toshiya Namikawa, IPMU
[Joint Experimental-Theoretical Cosmology Seminar] Implications for Cosmic Birefringence from Recent Cosmological Observations
4gou-kan Bld. 1F seminar hall
In this talk, I present implications for cosmic birefringence from recent cosmological observables. I begin by showing constraints on ALP mass through the ALP-induced cosmic birefringence using the Planck EB power spectrum. We find that some specific ALP masses are excluded. Next, I show that cosmic birefringence can explain a higher optical depth ¥tau~0.09 as a result of the DESI BAO measurements and CMB observations within the standard cosmological model. Specifically, I use the fact that the recent cosmic birefringence measurement, ¥beta_0=0.34 deg, has the phase ambiguity, ¥beta=¥beta_0+180n deg with n¥in Z. An ALP-induced birefringence model with a nonzero n can suppress the reionization bump in the EE spectrum while allowing for a large optical depth. I show a viable parameter region that simultaneously explains the large-scale CMB polarization, Planck EB power spectrum, and an elevated value of ¥tau. I also introduce the polarized SZ effect as a further test of cosmic birefringence at low redshift.
Rishi Mouland, Imperial College London
Phases of 2d Gauge Theories and Symmetric Mass Generation
Online (Zoom)
I will review symmetric mass generation (SMG), whereby fermions are gapped while preserving a chiral but necessarily non-anomalous symmetry. A simple model of SMG will be described, which leverages strongly-coupled gauge dynamics. I will then use bosonisation and dualities to derive the phase diagrams of a series of 2d Abelian gauge theories, including the 2d SMG model, in doing show establishing its validity. I will finally comment on the application of such constructions to symmetry-preserving boundary conditions and fermion-monopole scattering in 4d gauge theory.
Hiroyuki Tajima, The University of Tokyo
[KEK-JAEA Joint Seminar] An interdisciplinary approach to many-body physics: From ultracold atoms to dense matter
Hybrid On-site: Meeting Room 1, Kenkyu Honkan 1F (KEK Tsukuba Campus) Online: Zoom
