IOPP Seminar- Dr. YU Ning,,3:30pm,Oct.12,Monday

Talk 1
Time:2:30pm, Oct.16, Monday
Place:Room 9-409

Speaker: Chen Ji, Postdoctoral Researcher, ECT*-TIFPA, Trento, Italy

Title: "Nuclear structure effects in exotic atoms"


The proton radius extracted from recent high-precision spectroscopy
measurements in muonic hydrogen disagrees significantly with that
determined from electronic hydrogen spectroscopy or electron-proton
elastic scattering. Intrigued by the proton radius puzzle, new
measurements of the Lamb shift in other light muonic atoms will be
performed at PSI. These experiments aim to extract the nuclear charge
radius with high accuracies, however limited by our knowledge of nuclear
polarizability corrections.

The nuclear polarizabilities are QCD effects that contribute to the
atomic spectrum. They need to be provided by theory with high accuracy.
I will talk about how we perform ab-initio calculations of such nuclear
polarizability using state-of-the-art nuclear Hamiltonians, with a
precision that satisfies the experimental requirement. I will present
results for several light muonic atoms, and discuss the uncertainties
from both atomic and nuclear physics.

I will future extend the discussion to nuclear structure effects in
electronic atoms containing light halo nuclei near the edge of
stability. These nuclei are easier to be excited by the surrounding
electrons. As an example, I will discuss the calculation of 6He with the
halo effective field theory, and the possible extension to obtain the
nuclear polarizability, which is important for extracting the radius of
a halo nucleus from spectroscopic measurements.


Talk 2
Speaker: Dr. YU Ning
Title:Beam energy dependence of deuteron production in Au + Au collisions at RHIC

The production of light nuclei with small binding energy such as (anti)deuterons, can be used to study the freeze-out properties and local baryon density in high-energy nuclear collisions. The azimuthal anisotropic results of protons and deuterons have shown that the coalescence is the dominant process for the light nuclei production at later stage of the evolution.\\
%\hspace{0.3cm}In this talk we present a systematic study of colliding energy, centrality, and transverse momentum dependence of mid-rapidity deuteron and anti-deuteron production, measured by the STAR experiment, from Au + Au collisions at RHIC at $\sqrt{s_{NN}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39 and 200 GeV. Deuterons, protons and their anti-particles are identified using the time projection chamber (TPC) and time-of-flight detector (TOF). Proton and anti-proton yields are corrected from weak decays. The $B_2$ parameters, defined as $N(d)/N^2(p)$, which measure the phase space density for nucleons show a difference between $B_2(d)$) and $B_2(\bar{d})$. These observations may imply that baryon and anti-baryon freeze-out at different densities.