Nuclear Theory·nucl-th
10 papers—5 primary·5 cross-listed
We consider a pentadiagonal matrix which will be described in the text. We demonstrate practical methods for obtaining weak coupling expressions for the lowest eigenvector in terms of the parameters in the matrix, v and w. It is found that the expressions simplify if the wave function coefficients are put in the denominator.
Malwin Niehus🇩🇪 · Martin Hoferichter🇨🇭 · Bastian Kubis🇩🇪 · Jacobo Ruiz de Elvira🇨🇭
Analyzing the pion-mass dependence of scattering phase shifts beyond the low-energy region requires the unitarization of the amplitudes from chiral perturbation theory. In the two-flavor theory, unitarization via the inverse-amplitude method (IAM) can be justified from dispersion relations, which is therefore expected to provide reliable predictions for the pion-mass dependence of results from lattice QCD calculations. In this work, we provide compact analytic expression for the two-loop partial-wave amplitudes for required for the IAM at subleading order. To analyze the pion-mass dependence of recent lattice QCD results for the -wave, we develop a fit strategy that for the first time allows us to perform stable two-loop IAM fits and assess the chiral convergence of the IAM approach. While the comparison of subsequent orders suggests a breakdown scale not much below the mass, a detailed understanding of the systematic uncertainties of lattice QCD data is critical to obtain acceptable fits, especially at larger pion masses.
Lubomir Pentchev (Thomas Jefferson National Accelerator Facility, Newport News, Virginia, USA)🇺🇸 · Igor I. Strakovsky (The George Washington University, Washington, D.C., USA)🇺🇸
The - scattering length, , can be extracted from the photoproduction cross section near threshold using the Vector Meson Dominance (VMD) model to relate the reaction to . Such estimates based on experimental data result in values for , which are much lower than most of the theoretical predictions. In this work, we study the relations between the different results, depending on the use of the total or the differential cross sections, and the method of extrapolating the data to threshold in the case of a low-statistics data sample, such as the near threshold photoproduction dataset. We estimate a range for of to ~fm as extracted from experimental data within the VMD model and discuss possible reasons for such lower values compared to the theoretical results.
Zhoudunming Tu (for the STAR Collaboration)🇺🇸
Gluon density and its distributions inside nuclei and the parton modification of bounded nucleons inside a nucleus, are some of the main standing problems in nuclear and particle physics. In recent years, ultra-peripheral collisions (UPC) of heavy ions have provided a new way of probing the gluon density, which is based on coherent diffractive vector-meson productions, e.g., meson. For heavy ions, e.g., Pb, the gluon density is found to be significantly suppressed through the UPC measurement, suggesting a strong gluon shadowing effect in heavy nuclei. In this analysis, we aim to look at a unique set of data taken by the STAR experiment, where mesons are photoproduced off the deuteron target with no other particle produced, except for the deuteron or its breakup products. The Zero Degree Calorimeter response with respect to the deuteron dissociation by detecting a beam-rapidity neutron is also investigated and provides additional information about the underlying physics process. The cross section of photoproduction in the photon-deuteron system is measured at the photon-nucleon center-of-mass energy , as well as the momentum transfer dependence cross section, . Data suggests a wider gluon density distribution than the Hulthen charge density distribution in deuteron.
Bin Wu🇨🇭
Deciphering the origin of collective phenomena in small colliding systems is one of contemporary focuses in heavy-ion physics. It entails penetrating the barrier between two previously separated research topics: thermalization/hydrodynamization and phenomenological studies of collectivity. I first review some recent progress in understanding thermalization/hydrodynamization in large colliding systems, centralized on bottom-up thermalization. Then, using a simple kinetic theory I demonstrate how the investigation of hydrodynamization is intertwined with the study of flow in small colliding systems. Connections of these studies to "hard probes" are also commented where possible.
first authorsco-authorsvia INSPIRE