Nuclear Experiment

In pp collisions at LHC energies, heavy quarks are produced in initial hard scatterings and then these quarks hadronize in either open heavy-flavor hadrons or quarkonia (e.g. J/ ψ , ψ(2S) , Υ ). The study of quarkonium production as a function of charged-particle multiplicity links soft and hard processes and allows one to study their interplay. While a linear increase of quarkonium production as a function of charged-particle multiplicity can be reasonably well understood in the context of multi-parton interactions, the observation of deviations with respect to a linear increase requires a more detailed description of the collision. In this contribution, we will present the latest ALICE measurements at forward rapidity for J/ ψ and Υ production as a function of charged-particle multiplicity in pp collisions at s √ =13 TeV. The first measurement of the double ratios of relative yield of Υ(2S) over Υ(1S) and J/ ψ over Υ(1S) as a function of charged-particle multiplicity will also be shown.

Quarkonium has been proposed as a sensitive probe of quark-gluon plasma (QGP) more than thirty years ago. Since then, lots of experimental efforts have been devoted to study its production in heavy-ion collisions to search for QGP and study its properties and significant progresses have been made. In this paper, an overview of recent experimental results on charmonium and bottomonium production in heavy-ion collisions as well as in small systems are presented. Furthermore, the results on exotic particle X(3872) production in Pb+Pb and p+p collisions are also discussed.

The low-lying non-yrast states in 114 Te have been investigated using the Indian National Gamma Array through the fusion-evaporation reaction 112 Sn( 4 He, 2n) at a beam energy of 37 MeV. Eight new γ -transitions have been placed in the level scheme to establish the quasi- γ band in this nucleus. Spin and parity of several excited states have been assigned from the present spectroscopy measurements. The comparison of experimental results on the observed bands with the Interacting Boson Model (IBM) and Triaxial Projected Shell Model (TPSM) confirming the existence of the quasi- γ band structure in the 114 Te nucleus.

Available data on the polarization of the secondary proton (as a function of its momentum K ) in the inelastic ({\it p, p ??}) reactions with the 9 Be, 12 C, and 40 Ca nuclei and differential cross section data (the momentum distributions) for the reactions at the initial proton energy 1 GeV and scattering angles ? =21 ??and ? =24.5 ??were analysed in a range of the high momenta K close to the momentum corresponding to the proton elastic scattering off the investigated nucleus. A structure in the polarization and momentum distribution data at the high momenum K , related probably to quasi-elastic scattering off a 8 Be-like nucleon cluster inside the nuclei, was observed.

A kinematically complete quasi-free (p,pn) experiment in inverse kinematics was performed to study the structure of the Borromean nucleus 17 B, which had long been considered to have neutron halo. By analyzing the momentum distributions and exclusive cross sections, we obtained the spectroscopic factors for 1 s 1/2 and 0 d 5/2 orbitals, and a surprisingly small percentage of 9(2) % was determined for 1 s 1/2 . Our finding of such a small 1 s 1/2 component and the halo features reported in prior experiments can be explained by the deformed relativistic Hartree-Bogoliubov theory in continuum, revealing a definite but not dominant neutron halo in 17 B. The present work gives the smallest s - or p -orbital component among known nuclei exhibiting halo features, and implies that the dominant occupation of s or p orbitals is not a prerequisite for the occurrence of neutron halo.

Kr83m with a short lifetime is an ideal calibration source for liquid xenon or liquid argon detector. The 83mKr isomer can be generated through the decay of Rb83 isotope, and Rb83 is usually produced by proton beams bombarding natural krypton atoms. In this paper, we report a successful production of Rb83/Kr83m with 3.4 MeV proton beam energy and measure the production rate with such low proton energy for the first time. Another production attempt was performed with newly available 20 MeV proton beam in China, the production rate is consistent with our expectation. The produced Kr83m source has been successfully injected into PandaX-II liquid xenon detector and yielded enough statistics for detector calibration.

The competing 22 Ne( α,γ ) 26 Mg and 22 Ne( α,n ) 25 Mg reactions control the production of neutrons for the weak s -process in massive and AGB stars. In both systems, the ratio between the corresponding reaction rates strongly impacts the total neutron budget and strongly influences the final nucleosynthesis. The 22 Ne( α,γ ) 26 Mg and 22 Ne( α,n ) 25 Mg reaction rates was re-evaluated by using newly available information on 26 Mg given by various recent experimental studies. Evaluations of The evaluated 22 Ne( α,γ ) 26 Mg reaction rate remains substantially similar to that of Longland {\it et al.} but, including recent results from Texas A\&M, the 22 Ne( α,n ) 25 Mg reaction rate is lower at a range of astrophysically important temperatures. Stellar models computed with NEWTON and MESA predict decreased production of the weak branch s -process due to the decreased efficiency of 22 Ne as a neutron source. Using the new reaction rates in the MESA model results in 96 Zr/ 94 Zr and 135 Ba/ 136 Ba ratios in much better agreement with the measured ratios from presolar SiC grains.

The recent progress of multiple chiral doublet bands (M χ D) is reviewed for both experimental and theoretical sides. In particular, the experimental findings, theoretical predictions, selection rule for electromagnetic transitions, M χ D with octupole correlations and some related topics are highlighted. Based on these discussions, it is of highly scientific interest to search for the more M χ D as well as the possible chiral wobblers, chirality-parity quartet and chirality-pseudospin triplet (or quartet) bands in nuclear system.

These proceedings present an overview of the recent results on light flavor by the STAR experiment at RHIC.

Polarized proton-proton collisions at the Relativistic Heavy Ion Collider (RHIC) provide unique opportunities to study the spin structure of the nucleon. We will highlight recent results on the nucleon spin structure from the STAR and PHENIX experiments at RHIC: (1) A sizable gluon polarization in the proton is measured with longitudinal double spin asymmetries of jet and hadron production; (2) Longitudinal single spin asymmetries in W boson production improve constraints on the sea quark polarization. The new spin asymmetry results for W boson confirmed the SU(2) flavor asymmetry of the light sea quark polarization in the proton; (3) Transverse spin effects in hadronic systems offer new implications on parton distribution functions in the collinear and transverse momentum dependent frameworks. We will also discuss near term plans for the STAR forward detector upgrade and prospects for proton-proton and proton-ion collisions in the years beyond 2021 at STAR.