Small-momentum expansion of heavy-quark correlators in the large-β0 limit and αs extractions

We calculate the small-momentum expansion of vector, axial-vector, scalar, and pseudo-scalar heavy-quark current correlators in the large-β0 limit of QCD, extending the analysis of Grozin and Sturm beyond the vector current. Our results are used to study the higher-order behaviour of dimensionless ratios of vector and pseudo-scalar moments used for the precise extraction of the strong coupling, αs, from relativistic quarkonium sum rules and lattice data, respectively. We show that these ratios benefit from a partial cancellation of the leading renormalon singularities. Our results can guide the design of combinations of moments with improved perturbative behaviour.

Anomaly in the differential cross sections at 13 TeV

The analysis of the new TOTEM data at 13 TeV in a wide momentum transfer region reveals the unusual phenomenon — the presence in the elastic scattering amplitude of a term with a very large slope that is responsible for the behavior of hadron scattering at a very small momentum transfer. This term can be connected with hadron interactions at large distances.

DEBYE-WALLER TYPE EXPRESSIONS FOR THE NUCLEAR ELASTIC FORM FACTORS AT SMALL MOMENTUM TRANSFERS

The problem of the estimate of the nuclear elastic form factors in Born approximation is discussed in the region of small momentum transfers q. It is shown that approximate expressions of the Debye-Waller type are suitable for estimates of these form-factors in the oscillator shell model, for sufficiently small q.

The γγ Physics Program at BESIII

A key motivation for the two-photon physics program of the BESIII collaboration is the need of high precision data on electromagnetic transition form factors as input to the calculations of the contribution of hadronic Light-by-light scattering to the anomalous magnetic moment of the muon. The data collected with the BESIII detector allow to study the momentum dependence of the form factors at small momentum transfers, which is of special relevance for αμ. In this presentation the ongoing measurements of the transition form factors of π0,η and η' mesons, as well as pion pairs, are discussed, and the potential for first double-tagged measurements at BESIII are pointed out.

Exact correlations in the Lieb-Liniger model and detailed balance out-of-equilibrium

We study the density-density correlation function of the 1D Lieb–Liniger model and obtain an exact expression for the small momentum limit of the static correlator in the thermodynamic limit. We achieve this by summing exactly over the relevant form factors of the density operator in the small momentum limit. The result is valid for any eigenstate, including thermal and non-thermal states. We also show that the small momentum limit of the dynamic structure factors obeys a generalized detailed balance relation valid for any equilibrium state.