Nuclear Theory·nucl-th

Thursday·May 6, 2021

7 papers—4 primary·3 cross-listed

05
A dispersive estimate of scalar contributions to hadronic light-by-light scattering
Igor Danilkin🇩🇪 · Martin Hoferichter🇨🇭 · Peter Stoffer🇦🇹
We consider the contribution of scalar resonances to hadronic light-by-light scattering in the anomalous magnetic moment of the muon. While the $f_{0} (500)$ has already been addressed in previous work using dispersion relations, heavier scalar resonances have only been estimated in hadronic models so far. Here, we compare an implementation of the $f_{0} (980)$ resonance in terms of the coupled-channel $S$ -waves for $γ^{*} γ^{*} \to π π / K ˉ K$ to a narrow-width approximation, which indicates $a_{μ}^{HLbL} [f_{0} (980)] = - 0.2 (2) \times 1 0^{- 11}$ . With a similar estimate for the $a_{0} (980)$ , the combined effect is thus well below $1 \times 1 0^{- 11}$ in absolute value. We also estimate the contribution of heavier scalar resonances. In view of the very uncertain situation concerning their two-photon couplings we suggest to treat them together with other resonances of similar mass when imposing the matching to short-distance constraints. Our final result is a refined estimate of the $S$ -wave rescattering effects in the $π π$ and $K ˉ K$ channel up to about $1.3$ GeV and including a narrow-width evaluation of the $a_{0} (980)$ : $a_{μ}^{HLbL} [scalars] = - 9 (1) \times 1 0^{- 11}$ .
↳ hep-phhep-exhep-latnucl-thPLB(2021)·106 citations
06
$N = 4$ supersymmetric Yang-Mills thermodynamics to order $λ^{2}$
Qianqian Du🇨🇳 · Michael Strickland🇺🇸 · Ubaid Tantary🇺🇸
We calculate the resummed perturbative free energy of $N = 4$ supersymmetric Yang-Mills in four spacetime dimensions ( $SYM_{4, 4}$ ) through second order in the 't Hooft coupling $λ$ at finite temperature and zero chemical potential. Our final result is ultraviolet finite and all infrared divergences generated at three-loop level are canceled by summing over $SYM_{4, 4}$ ring diagrams. Non-analytic terms at $O (λ^{3/2})$ and $O (λ^{2} lo g λ)$ are generated by dressing the $A_{0}$ and scalar propagators. The gauge-field Debye mass $m_{D}$ and the scalar thermal mass $M$ are determined from their corresponding finite-temperature self-energies. Based on this, we obtain the three-loop thermodynamic functions of $SYM_{4, 4}$ to $O (λ^{2})$ . We compare our final result with prior results obtained in the weak- and strong-coupling limits and construct a generalized Padé approximant that interpolates between the weak-coupling result and the large- $N_{c}$ strong-coupling result. Our results suggest that the $O (λ^{2})$ weak-coupling result for the scaled entropy density is a quantitatively reliable approximation to the scaled entropy density for $0 \leq λ ≲ 2$ .
↳ hep-thhep-phnucl-thJHEP(2021)·10 citations
07
Heavy quark dynamics in a strongly magnetized quark-gluon plasma
Aritra Bandyopadhyay🇨🇳 · Jinfeng Liao🇺🇸 · Hongxi Xing🇨🇳
We present a calculation of the heavy quark momentum diffusion coefficients in a quark-gluon plasma under the presence of a strong external magnetic field, within the Lowest Landau Level (LLL) approximation. In particular, we apply the Hard Thermal Loop (HTL) technique for the resummed effective gluon propagator, generalized for a hot and magnetized medium. Using the derived effective HTL gluon propagator and the LLL quark propagator we analytically derive the full results for the longitudinal and transverse momentum diffusion coefficients as well as the energy losses for charm and bottom quarks beyond the static limit. We also show numerical results for these coefficients in two special cases where the heavy quark is moving either parallel or perpendicular to the external magnetic field.
↳ hep-phnucl-thPRD(2022)·24 citations

Affiliations

first authorsco-authorsvia INSPIRE

A dispersive estimate of scalar contributions to hadronic light-by-light scattering

N=4 supersymmetric Yang-Mills thermodynamics to order λ2

Heavy quark dynamics in a strongly magnetized quark-gluon plasma

Affiliations

$N = 4$ supersymmetric Yang-Mills thermodynamics to order $λ^{2}$