Tue·Sep 21, 2021Tuesday·September 21, 2021

1. 01*

   First-principle calculation of ${\eta }_c\to 2\gamma$ decay width from lattice QCD

   Yu Meng🇨🇳 · Xu Feng🇨🇳 · Chuan Liu🇨🇳 · Teng Wang🇨🇳 · Zuoheng Zou🇨🇳

   We perform a lattice QCD calculation of the ${\eta }_c\to 2\gamma$ decay width using a model-independent method that requires no momentum extrapolation of the off-shell form factors. This method also provides a straightforward and simple way to examine the finite-volume effects. The calculation is accomplished using $N_f=2$ twisted mass fermion ensembles. The statistically significant excited-state effects are observed and eliminated using a multi-state fit.The impact of fine-tuning the charm quark mass is also examined and confirmed to be well-controlled. Finally, using three lattice spacings for the continuum extrapolation, we obtain the decay width ${\Gamma }_{{\eta }_c\gamma \gamma }=6.67(16{)}_{\mathrm{stat}}(6{)}_{\mathrm{syst}}$ keV, which differs significantly from the Particle Data Group's reported value of ${\Gamma }_{{\eta }_c\gamma \gamma }=5.4(4)$ keV (2.9~$\sigma$ tension). We provide insight into the comparison between our findings, previous theoretical predictions, and experimental measurements.

   hep-lathep-exhep-phSci.Bull.(2023)·32 citations
2. 02*

   Spin-1 fields and RG flows in 4 dimensions

   Daniel Nogradi🇭🇺

   The most general local, classically scale invariant, perturbatively renormalizable, globally $SU(N)$ invariant Lagrangian is constructed for spin-1 fields in 4 dimensions. The total number of independent couplings is 7 and the 1-loop $\beta$-functions are computed in the MSbar scheme. A number of asymptotically free RG flows are identified corresponding to non-trivial QFTs. None of these are gauge theories. The details of the large-$N$ limit are also worked out and it is shown that the RG phase space is qualitatively similar for all $N>5$ including the $N\to \infty$ limit.

   hep-lathep-phPoS(2022)·0 citations
3. 03*

   Determination of the continuous $\beta$ function of SU(3) Yang-Mills theory

   Curtis T. Peterson🇺🇸 · Anna Hasenfratz🇺🇸 · Jake van Sickle🇺🇸 · Oliver Witzel🇩🇪

   In infinite volume the gradient flow transformation can be interpreted as a continuous real-space Wilsonian renormalization group (RG) transformation. This approach allows one to determine the continuous RG $\beta$ function, an alternative to the finite-volume step-scaling function. Unlike step-scaling, where the lattice must provide the only scale, the continuous $\beta$ function can be used even in the confining regime where dimensional transmutation generates a physical scale ${\Lambda }_{\mathrm{QCD}}$. We investigate a pure gauge SU(3) Yang-Mills theory both in the deconfined and the confined phases and determine the continuous $\beta$ function in both. Our investigation is based on simulations done with the tree-level Symanzik gauge action on lattice volumes up to $32^4$ using both Wilson and Zeuthen gradient flow (GF) measurements. Our continuum GF $\beta$ function exhibits considerably slower running than the universal 2-loop perturbative prediction, and at strong couplings it runs even slower than the 1-loop prediction.

   hep-latPoS(2022)·12 citations
4. 04*

   Pauli radius of the proton

   Zhu-Fang Cui🇨🇳 · Daniele Binosi🇮🇹 · Craig D. Roberts🇨🇳 · Sebastian M. Schmidt🇩🇪

   Using a procedure based on interpolation via continued fractions supplemented by statistical sampling, we analyse proton magnetic form factor data obtained via electron+proton scattering on $Q^2\in [0.027,0.55]$GeV${}^2$ with the goal of determining the proton magnetic radius. The approach avoids assumptions about the function form used for data interpolation and ensuing extrapolation onto $Q^2\simeq 0$ for extraction of the form factor slope. In this way, we find $r_M=0.817(27)$fm. Regarding the difference between proton electric and magnetic radii calculated in this way, extant data are seen to be compatible with the possibility that the slopes of the proton Dirac and Pauli form factors, $F_{1,2}(Q^2)$, are not truly independent observables; to wit, the difference $F_1^{\prime }(0)-F_2^{\prime }(0)/{\kappa }_p=[1+{\kappa }_p]/[4m_p^2]$, viz. the proton Foldy term.

   ↳ hep-phhep-exhep-latnucl-ex+1Chin.Phys.Lett.(2021)·11 citations
5. 05*

   Magnetic moment of the ${\Xi }_b(6227)$ as a molecular pentaquark state

   U. Ozdem🇹🇷

   In this study, considering that the ${\Xi }_b(6227)$ state is in molecular structure, the magnetic moment of this state is extracted in the light-cone QCD sum rules. The numerical result is obtained as ${\mu }_{{\Xi }_b}=0.12\pm 0.03{\mu }_N$. The magnetic moment of this state contains important information of its internal structure and shape deformations. Measurement of the magnetic moment of the ${\Xi }_b(6227)$ state in future experimental facilities can be very helpful in identification of the quantum numbers, as well as comprehension of the inner structure of this state.

   ↳ hep-phhep-exhep-latEur.Phys.J.Plus(2022)·11 citations
6. 06*

   Chiral Effective Field Theory after Thirty Years: Nuclear Lattice Simulations

   Dean Lee🇺🇸

   The introduction of chiral effective field theory by Steven Weinberg three decades ago has had a profound and lasting impact on nuclear physics. This brief review explores the impact of Weinberg's work on the field of nuclear lattice simulations. Rather than a summary of technical details, an effort is made to present the conceptual advances that made much of the recent progress possible.

   ↳ nucl-thhep-latnucl-exFew Body Syst.(2021)·3 citations
7. 07*

   Time-space duality in 2D quantum gravity

   Ding Jia🇨🇦

   An important task faced by all approaches of quantum gravity is to incorporate superpositions and quantify quantum uncertainties of spacetime causal relations. We address this task in 2D. By identifying a global $Z_2$ symmetry of 1+1D quantum gravity, we show that gravitational path integral configurations come in equal amplitude pairs with timelike and spacelike relations exchanged. As a consequence, any two points are equally probable to be timelike and spacelike separated in a universe without boundary conditions. In the context of simplicial quantum gravity we identify a local symmetry of the action which shows that even with boundary conditions causal uncertainties are generically present. Depending on the boundary conditions, causal uncertainties can still be large and even maximal.

   ↳ gr-qchep-lathep-thquant-phClass.Quant.Grav.(2022)·9 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.