Fri·Oct 1, 2021Friday·October 1, 2021

1. 01*

   Nucleon-pion-state contamination in lattice computations of the nucleon electromagnetic form factors

   Oliver Bar🇩🇪 · Haris Colic🇩🇪

   The nucleon-pion-state contributions to QCD two-point and three-point functions relevant for lattice calculations of the nucleon electromagnetic form factors are studied in chiral perturbation theory. To leading order the results depend on a few experimentally known low-energy constants only, and the nucleon-pion-state contribution to the form factors can be estimated. The nucleon-pion-state contribution to the electric form factor $G_{\mathrm{E}}(Q^2)$ is at the +5 percent level for a source-sink separation of 2 fm, and it increases with increasing momentum transfer $Q^2$. For the magnetic form factor the nucleon-pion-state contribution leads to an underestimation of $G_{\mathrm{M}}(Q^2)$ by about $-5$ percent that decreases with increasing $Q^2$. For smaller source-sink separations that are accessible in present-day lattice simulations the impact is larger. Although the ChPT results may not be applicable for these time separations a comparison with recent lattice data works reasonably well.

   hep-latPoS(2022)·2 citations
2. 02*

   Parton physics from a heavy-quark operator product expansion: Lattice QCD calculation of the second moment of the pion distribution amplitude

   William Detmold🇺🇸 · Anthony Grebe🇺🇸 · Issaku Kanamori🇯🇵 · C.-J. David Lin🇹🇼 · Santanu Mondal🇺🇸 · Robert Perry🇹🇼 · Yong Zhao🇺🇸

   The pion light-cone distribution amplitude (LCDA) is a central non-perturbative object of interest for high-energy exclusive processes in quantum chromodynamics. In this article, the second Mellin moment of the pion LCDA is determined as a proof-of-concept calculation for the first numerical implementation of the heavy-quark operator product expansion (HOPE) method. The resulting value for the second Mellin moment, determined in quenched QCD at a pion mass of $m_{\pi }=550$ MeV at a factorization scale of 2 GeV is $⟨{\xi }^2⟩=0.210\pm 0.013\text{ (stat.)}\pm 0.034\text{ (sys.)}$. This result is compatible with those from previous determinations of this quantity.

   hep-lathep-phnucl-thPRD(2022)·40 citations
3. 03*

   Heavy-quark spin polarization induced by the Kondo effect in a magnetic field

   Daiki Suenaga🇯🇵 · Yasufumi Araki🇯🇵 · Kei Suzuki🇯🇵 · Shigehiro Yasui🇯🇵

   We propose a new mechanism of the heavy-quark spin polarization (HQSP) in quark matter induced by the Kondo effect under external magnetic field. The Kondo effect is caused by a condensate between a heavy and a light quark called the Kondo condensate leading to a mixing of the heavy and light quark spins. Thus the HQSP is driven through the Kondo effect from light quarks coupling with the magnetic field in quark matter. For demonstration, we employ the Nambu--Jona-Lasinio type model under a magnetic field, and investigate the HQSP within the linear response theory with vertex corrections required by the $U(1{)}_{\mathrm{EM}}$ electromagnetic gauge invariance. As a result, we find that the HQSP arises significantly with the appearance of the Kondo effect. Our findings are testable in future sign-problem-free lattice simulations.

   ↳ hep-phhep-latnucl-thPRD(2022)·6 citations
4. 04*

   Towards the real-time evolution of gauge-invariant ${\mathbb{Z}}_2$ and $U(1)$ quantum link models on NISQ Hardware with error-mitigation

   Emilie Huffman🇨🇦 · Miguel García Vera🇪🇨 · Debasish Banerjee🇮🇳

   Practical quantum computing holds clear promise in addressing problems not generally tractable with classical simulation techniques, and some key physically interesting applications are those of real-time dynamics in strongly coupled lattice gauge theories. In this article, we benchmark the real-time dynamics of ${\mathbb{Z}}_2$ and $U(1)$ gauge invariant plaquette models using noisy intermediate scale quantum (NISQ) hardware, specifically the superconducting-qubit-based quantum IBM Q computers. We design quantum circuits for models of increasing complexity and measure physical observables such as the return probability to the initial state, and locally conserved charges. NISQ hardware suffers from significant decoherence and corresponding difficulty to interpret the results. We demonstrate the use of hardware-agnostic error mitigation techniques, such as circuit folding methods implemented via the Mitiq package, and show what they can achieve within the quantum volume restrictions for the hardware. Our study provides insight into the choice of Hamiltonians, construction of circuits, and the utility of error mitigation methods to devise large-scale quantum computation strategies for lattice gauge theories.

   ↳ quant-phcond-mat.str-elhep-latPRD(2022)·25 citations
5. 05*

   Exclusive determinations of $|V_{cb}|$ and $R(D^{\ast })$ through unitarity

   G. Martinelli🇮🇹 · S. Simula🇮🇹 · L. Vittorio🇮🇹

   In this work we apply the Dispersive Matrix (DM) method of Refs. [1,2] to the lattice computations of the Form Factors (FFs) entering the semileptonic $B\to D^{\ast }\ell {\nu }_{\ell }$ decays, recently produced by the FNAL/MILC Collaborations [3] at small, but non-vanishing values of the recoil variable ($w-1$). Thanks to the DM method we obtain the FFs in the whole kinematical range accessible to the decay in a completely model-independent and non-perturbative way, implementing exactly both unitarity and kinematical constraints. Using our theoretical bands of the FFs we extract $|V_{cb}|$ from the experimental data and compute the theoretical value of $R(D^{\ast })$. Our final result for $|V_{cb}|$ reads $|V_{cb}|=(41.3\pm 1.7)\cdot 10^{-3}$, compatible with the most recent inclusive estimate at the $0.5\sigma$ level. Moreover, we obtain the pure theoretical value $R(D^{\ast })=0.275\pm 0.008$, which is compatible with the experimental world average at the $\sim 1.3\sigma$ level.

   ↳ hep-phhep-exhep-latEPJC(2022)·65 citations
6. 06*

   C-P-T Fractionalization

   Juven Wang🇺🇸

   Discrete spacetime symmetries of parity P or reflection R, and time-reversal T, act naively as ${\mathbb{Z}}_2$-involutions in the passive transformation on the spacetime coordinates; but together with a charge conjugation C, the total C-P-R-T symmetries have enriched active transformations on fields in representations of the spacetime-internal symmetry groups of quantum field theories (QFTs). In this work, we derive that these symmetries can be further fractionalized, especially in the presence of the fermion parity $(-1{)}^{\mathrm{F}}$. We elaborate on examples including relativistic Lorentz invariant QFTs (e.g., spin-1/2 Dirac or Majorana spinor fermion theories) and nonrelativistic quantum many-body systems (involving Majorana zero modes), and comment on applications to spin-1 Maxwell electromagnetism (QED) or interacting Yang-Mills (QCD) gauge theories. We discover various C-P-R-T-$(-1{)}^{\mathrm{F}}$ group structures, e.g., Dirac spinor is in a projective representation of ${\mathbb{Z}}_2^{\mathrm{C}}\times {\mathbb{Z}}_2^{\mathrm{P}}\times {\mathbb{Z}}_2^{\mathrm{T}}$ but in an (anti)linear representation of an order-16 nonabelian finite group, as the central product between an order-8 dihedral (generated by C and P) or quaternion group and an order-4 group generated by T with T${}^2=(-1{)}^{\mathrm{F}}$. The general theme may be coined as C-P-T or C-R-T fractionalization.

   ↳ hep-thcond-mat.str-elhep-lathep-ph+2PRD(2022)·10 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.