Thu·Apr 13, 2017Thursday·April 13, 2017

1. 01*

   Collective flow from AA, pA to pp collisions - Toward a unified paradigm

   Wei Li🇺🇸

   I give an overview of the latest development in understanding collective phenomena in high-multiplicity hadronic final state from relativistic nucleus-nucleus, proton-nucleus and proton-proton collisions. Upon reviewing the experimental data and confronting them with theoretical models, a unified paradigm in describing the observed collectivity across all hadronic collision systems is emerging. Potential future paths toward addressing key open questions, especially on collectivity in small systems (pp, pA), are discussed.

   nucl-exhep-exhep-phnucl-thNPA(2017)·22 citations
2. 02*

   Single-neutron knockout from ${}^{20}\text{C}$ and the structure of ${}^{19}\text{C}$

   J.W. Hwang🇰🇷 · S. Kim🇰🇷 · Y. Satou🇰🇷 · N.A. Orr🇫🇷 · Y. Kondo🇯🇵 · T. Nakamura🇯🇵 · J. Gibelin🇫🇷 · N.L. Achouri🇫🇷 · T. Aumann🇩🇪 · H. Baba🇯🇵 · F. Delaunay🇫🇷 · P. Doornenbal🇯🇵 and 33 other authors

   The low-lying unbound level structure of the halo nucleus ${}^{19}\text{C}$ has been investigated using single-neutron knockout from ${}^{20}\text{C}$ on a carbon target at 280 MeV/nucleon. The invariant mass spectrum, derived from the momenta of the forward going beam velocity ${}^{18}\text{C}$ fragment and neutrons, was found to be dominated by a very narrow near threshold ($E_{\text{rel}}$ = 0.036(1) MeV) peak. Two less strongly populated resonance-like features were also observed at $E_{\text{rel}}$ = 0.84(4) and 2.31(3) MeV, both of which exhibit characteristics consistent with neutron $p$-shell hole states. Comparisons of the energies, measured cross sections and parallel momentum distributions to the results of shell-model and eikonal reaction calculations lead to spin-parity assignments of $5/2_1^{+}$ and $1/2_1^{-}$ for the levels at $E_x$ = 0.62(9) and 2.89(10) MeV with $S_n$ = 0.58(9) MeV. Spectroscopic factors were also deduced and found to be in reasonable accord with shell-model calculations. The valence neutron configuration of the ${}^{20}\text{C}$ ground state is thus seen to include, in addition to the known $1s_{1/2}^2$ component, a significant $0d_{5/2}^2$ contribution. The level scheme of ${}^{19}\text{C}$, including significantly the $1/2_1^{-}$ cross-shell state, is well accounted for by the YSOX shell-model interaction developed from the monopole-based universal interaction.

   nucl-exnucl-thPLB(2017)·21 citations
3. 03*

   Disentangling flow and signals of Chiral Magnetic Effect in U+U, Au+Au and p+Au collisions

   Prithwish Tribedy (for the STAR Collaboration)🇺🇸

   We present STAR measurements of the charge-dependent three-particle correlator ${\gamma }^{a,b}=⟨\cos ({\varphi }_1^a+{\varphi }_2^b-2{\varphi }_3)⟩/v_2\{2\}$ and elliptic flow $v_2\{2\}$ in U+U, Au+Au and p+Au collisions at RHIC. The difference $\Delta \gamma =\gamma (\mathrm{opposite}-\mathrm{sign})-\gamma (\mathrm{same}-\mathrm{sign})$ measures charge separation across the reaction plane, a predicted signal of the Chiral Magnetic Effect (CME). Although charge separation has been observed, it has been argued that the measured separation can also be explained by elliptic flow related backgrounds. In order to separate the two effects, we perform measurements of the $\gamma$-correlator where background expectations differ from magnetic field driven effects. A differential measurement of $\gamma$ with the relative pseudorapidity ($\Delta \eta$) between the first and second particles indicate that $\Delta \gamma$ in peripheral A+A and p+A collisions are dominated by short-range correlations in $\Delta \eta$. However, a relatively wider component of the correlation in $\Delta \eta$ tends to vanish the same way as projected magnetic field as predicted by MC-Glauber simulations.

   nucl-exhep-phnucl-thNPA(2017)·24 citations
4. 04*

   Noise Refocusing in a Five-blade Neutron Interferometer

   J. Nsofini🇨🇦 · D. Sarenac🇨🇦 · K. Ghofrani · M. G. Huber · M. Arif · D. G. Cory🇨🇦 · D. A. Pushin🇨🇦

   We provide a quantum information description of a proposed five-blade neutron interferometer geometry and show that it is robust against low frequency mechanical vibrations and dephasing due to the dynamical phase. The extent to which the dynamical phase affects the contrast in a neutron interferometer is experimentally shown. In our model, we consider the coherent evolution of a neutron wavepacket in an interferometer crystal blade and simulate the effect of mechanical vibrations and momentum spread of the neutron through the interferometer. The standard three-blade neutron interferometer is shown to be immune to dynamical phase noise but prone to noise from mechanical vibrations, the decoherence free subspace four-blade neutron interferometer is shown to be immune to mechanical vibration noise but prone to noise from the dynamical phase, while the proposed five-blade neutron interferometer is shown to be immune to both low-frequency mechanical vibration noise and dynamical phase noise.

   ↳ quant-phnucl-exphysics.atom-phJ.Appl.Phys.(2017)·8 citations
5. 05*

   Two-photon exchange corrections to ${\gamma }^{\ast }N\Delta$ form factors for $Q^2\le 4$ (Gev/$c$)${}^2$

   Hai-Qing Zhou🇨🇳 · Shin Nan Yang🇹🇼

   We evaluate the corrections of the two-photon exchange (TPE) process on the ${\gamma }^{\ast }N\Delta$ transition form factors. The contributions of the TPE process to the $eN\to e\Delta (1232)\to eN\pi$ are calculated in a hadronic model with the inclusion of only the elastic nucleon intermediate states, to estimate its effects on the multipoles $M_{1^{+}}^{(3/2)},E_{1^{+}}^{(3/2)},S_{1^{+}}^{(3/2)}$ at the $\Delta$ peak. We find that TPE effects on $G_M^{\ast }$ is very small. $G_E^{\ast },$ and $G_C^{\ast }$ are also little affected at small $Q^2$. For $G_E^{\ast }$, the TPE effects reach about $3-8\%$ near $Q^2\sim 4$ GeV${}^2$, depending on the model, MAID or SAID, used to emulate the data. For $G_C^{\ast }$, the TPE effects decrease rapidly with increasing $ϵ$ while growing with increasing $Q^2$ to reach $\sim 6-15\%$ with $Q^2\sim 4$ GeV${}^2$ at $ϵ=0.2$. Sizeable TPE corrections to $G_E^{\ast }$ and $G_C^{\ast }$ found here points to the need of including TPE effects in the multipole analysis in the region of high $Q^2$ and small $ϵ$. The TPE corrections to $R_{EM}$ and $R_{SM}$ obtained in our hadronic calculation are compared with those obtained in a partonic calculation for moderate momentum transfer of $2<Q^2<4$ GeV${}^2$.

   ↳ nucl-thhep-phnucl-exPRC(2017)·13 citations
6. 06*

   Low-$x$ Physics in $pA$ Collisions and at the EIC

   Bo-Wen Xiao🇨🇳

   In this proceeding, I review what we have learned, and what we will be able to learn, about low-$x$ physics from proton-nucleus ($pA$) collisions at RHIC and the LHC, and how this complements future Electron-Ion Collider (EIC) measurements. EIC not only will provide us essential and complementary information about the gluon saturation to the knowledge that we have learned from $pA$ collisions at RHIC and the LHC, it will also allow us to visualize the internal structure of protons and nuclei in a multi-dimensional fashion with unprecedented precision.

   ↳ nucl-thhep-phnucl-exNPA(2017)·3 citations
7. 07*

   Efficient, high-resolution resonance laser ionization spectroscopy using weak transitions to long-lived excited states

   R. P. de Groote🇫🇮 · M. Verlinde🇧🇪 · V. Sonnenschein🇫🇮 · K. T. Flanagan🇬🇧 · I. Moore🇫🇮 · G. Neyens🇧🇪

   Laser spectroscopic studies on minute samples of exotic radioactive nuclei require very efficient experimental techniques. In addition, high resolving powers are required to allow extraction of nu- clear structure information. Here we demonstrate that by using weak atomic transitions, resonance laser ionization spectroscopy is achieved with the required high efficiency (1-10%) and precision (linewidths of tens of MHz). We illustrate experimentally and through the use of simulations how the narrow experimental linewidths are achieved and how distorted resonance ionization spec- troscopy lineshapes can be avoided. The role of the delay of the ionization laser pulse with respect to the excitation laser pulse is crucial: the use of a delayed ionization step permits the best resolving powers and lineshapes. A high efficiency is maintained if the intermediate level has a lifetime that is at least of the order of the excitation laser pulse width. A model that describes this process re- produces well the observed features and will help to optimize the conditions for future experiments.

   ↳ physics.ins-detnucl-exPRA(2017)·27 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.