Wed·Jul 12, 2017Wednesday·July 12, 2017

1. 01*

   Measurement of the Vector and Tensor Asymmetries at Large Missing Momentum in Quasielastic $(\vec{e},e^{\prime }p)$ Electron Scattering from Deuterium

   A. DeGrush🇺🇸 · A. Maschinot🇺🇸 · T. Akdogan🇺🇸 · R. Alarcon🇺🇸 · W. Bertozzi🇺🇸 · E. Booth🇺🇸 · T. Botto🇺🇸 · J.R. Calarco🇺🇸 · B. Clasie🇺🇸 · C. Crawford🇺🇸 · K. Dow🇺🇸 · M. Farkhondeh🇺🇸 and 32 other authors

   We report the measurement of the beam-vector and tensor asymmetries $A_{ed}^V$ and $A_d^T$ in quasielastic $(\vec{e},e^{\prime }p)$ electrodisintegration of the deuteron at the MIT-Bates Linear Accelerator Center up to missing momentum of 500~MeV/c. Data were collected simultaneously over a momentum transfer range $0.1<Q^2<0.5$~(GeV/c)${}^2$ with the Bates Large Acceptance Spectrometer Toroid using an internal deuterium gas target, polarized sequentially in both vector and tensor states. The data are compared with calculations. The beam-vector asymmetry $A_{ed}^V$ is found to be directly sensitive to the $D$-wave component of the deuteron and have a zero-crossing at a missing momentum of about 320~MeV/c, as predicted. The tensor asymmetry $A_d^T$ at large missing momentum is found to be dominated by the influence of the tensor force in the neutron-proton final-state interaction. The new data provide a strong constraint on theoretical models.

   nucl-exPRL(2017)·3 citations
2. 02*

   Soft-QCD physics in pp and p-Pb with ALICE

   Valentina Zaccolo (for the ALICE Collaboration)🇮🇹

   At high collision energies as achieved at the LHC there are increasing contributions from hard processes, which can be computed with perturbative QCD. Nevertheless, particle production is still dominated by soft QCD with transferred momentum of a few GeV. These phenomena are described by non-perturbative phenomenology and challenge the theoretical models. ALICE has measured several observables which target soft QCD, both in Run 1 and 2 proton-proton and proton-lead collisions at the LHC. A selection of results will be presented in these proceedings, focusing on the model comparisons and summarising the understanding of soft QCD after almost 8 years of data taking.

   nucl-ex0 citations
3. 03*

   ${}^{\text{7}}$Li-induced reaction on ${}^{\text{nat}}$Mo: A study of complete versus incomplete fusion

   Deepak Kumar · Moumita Maiti · Susanta Lahiri🇮🇳

   Several investigations on the complete-incomplete fusion (CF-ICF) dynamics of $\alpha$-cluster well-bound nuclei has been contemplated above the Coulomb barrier ($\sim$ 4-7 MeV/nucleon) in recent years. It is therefore expected to observe significant ICF over CF in the reactions induced by a weakly bound $\alpha$-cluster nucleus at slightly above the barrier. In order to investigate CF-ICF in the loosely bound system, ${}^{\text{7}}$Li beam was bombarded on the ${}^{\text{nat}}$Mo foils, separated by the aluminium (Al) catcher foils alternatively, within $\sim$ 3-6.5 MeV/nucleon. Evaporation residues produced in each foil were identified by the $\gamma$-ray spectrometry. Measured cross section data of the residues were compared with the theoretical model calculations based on the equilibrium (EQ) and preequilibrium (PEQ) reaction mechanisms. The experimental cross section of ${}^{\text{101m,100,99m,97}}$Rh, ${}^{\text{97,95}}$Ru, ${}^{\text{99m,96,95,94,93m+g}}$Tc and ${}^{\text{93m}}$Mo residues measured at various projectile energies were satisfactorily reproduced by the simplified coupled channel approach in comparison to single barrier penetration model calculation. Significant cross section enhancement in the $\alpha$-emitting channels was observed compared to EQ and PEQ model calculations throughout observed energy region. The ICF process over CF was analyzed by comparing with EMPIRE. The increment of the incomplete fusion fraction was observed with increasing projectile energies. Theoretical model calculations reveal that compound reaction mechanism is the major contributor to the production of residues. Theoretical evaluations substantiate the contribution of ICF over the CF in $\alpha$-emitting channels.

   nucl-exPRC(2017)·34 citations
4. 04*

   First Exclusive Measurement of Deeply Virtual Compton Scattering off ${}^4$He: Toward the 3D Tomography of Nuclei

   M. Hattawy🇺🇸 · N.A. Baltzell🇺🇸 · R. Dupré🇫🇷 · K. Hafidi🇺🇸 · S. Stepanyan🇺🇸 · S. Bültmann🇺🇸 · R. De Vita🇮🇹 · A. El Alaoui🇨🇱 · L. El Fassi🇺🇸 · H. Egiyan🇺🇸 · F.X. Girod🇺🇸 · M. Guidal🇫🇷 and 148 other authors

   We report on the first measurement of the beam-spin asymmetry in the exclusive process of coherent deeply virtual Compton scattering off a nucleus. The experiment used the 6 GeV electron beam from the CEBAF accelerator at Jefferson Lab incident on a pressurized ${}^4$He gaseous target placed in front of the CEBAF Large Acceptance Spectrometer (CLAS). The scattered electron was detected by CLAS and the photon by a dedicated electromagnetic calorimeter at forward angles. To ensure the exclusivity of the process, a specially designed radial time projection chamber was used to detect the recoiling ${}^4$He nuclei. We measured beam-spin asymmetries larger than those observed on the free proton in the same kinematic domain. From these, we were able to extract, in a model-independent way, the real and imaginary parts of the only ${}^4$He Compton form factor, ${\mathcal{H}}_{\mathcal{A}}$. This first measurement of coherent deeply virtual Compton scattering on the ${}^4$He nucleus, with a fully exclusive final state via nuclear recoil tagging, leads the way toward 3D imaging of the partonic structure of nuclei.

   nucl-exhep-exPRL(2017)·47 citations
5. 05*

   Accelerator Based Fusion Reactor

   Keh-Fei Liu🇺🇸 · Alexander Wu Chao

   A feasibility study of fusion reactors based on accelerators is carried out. We consider a novel scheme where a beam from the accelerator hits the target plasma on the resonance of the fusion reaction and establish characteristic criteria for a workable reactor. We consider the reactions $d+t\to n+\alpha ,d+{}^3{H}_e\to p+\alpha$, and $p+{}^{11}B\to 3\alpha$ in this study. The critical temperature of the plasma is determined from overcoming the stopping power of the beam with the fusion energy gain. The needed plasma lifetime is determined from the width of the resonance, the beam velocity and the plasma density. We estimate the critical beam flux by balancing the energy of fusion production against the plasma thermo-energy and the loss due to stopping power for the case of an inert plasma. The product of critical flux and plasma lifetime is independent of plasma density and has a weak dependence on temperature. Even though the critical temperatures for these reactions are lower than those for the thermonuclear reactors, the critical flux is in the range of $10^{22}-10^{24}/\mathrm{c}{\mathrm{m}}^2/s$ for the plasma density ${\rho }_t=10^{15}/\mathrm{c}{\mathrm{m}}^3$ in the case of an inert plasma. Several approaches to control the growth of the two-stream instability are discussed. We have also considered several scenarios for practical implementation which will require further studies. Finally, we consider the case where the injected beam at the resonance energy maintains the plasma temperature and prolongs its lifetime to reach a steady state. The equations for power balance and particle number conservation are given for this case.

   ↳ physics.plasm-phhep-exnucl-exnucl-th+1Nucl.Fusion(2017)·3 citations
6. 06*

   On the use of NaI scintillation for high stability nuclear decay rate measurements

   Scott D. Bergeson🇺🇸 · Michael J. Ware · Jeremy Hawk

   We demonstrate the linearity and stability of a gamma-ray scintillation detector comprised of a NaI(Tl) crystal and a scientific-grade CMOS camera. After calibration, this detector exhibits excellent linearity more than three decades of activity levels. Because the detector is not counting pulses, no dead-time correction is required. When high activity sources are brought into close proximity to the NaI crystal, several minutes are required for the scintillation to achieve a steady state. On longer time scales, we measure drifts of a few percent over several days. These instabilities have important implications for precision determinations of nuclear decay rate stability.

   ↳ physics.ins-detnucl-ex0 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.