Tue·Nov 6, 2018Tuesday·November 6, 2018

1. 01*

   Clarification of large-strength transitions in the beta decay of 11Be

   J. Refsgaard · J. Büscher🇩🇪 · A. Arokiaraj · H.O.U. Fynbo🇩🇰 · R. Raabe🇧🇪 · K. Riisager🇩🇰

   The shape and normalisation of the beta-delayed alpha spectrum from 11Be was measured by implanting 11Be ions in a segmented Si detector. The spectrum is found to be dominated by a well-known transition to the 3/2+ state at Ex = 9.87MeV in 11B. A significant increase in the observed decay strength towards the higher end of the Q window means, however, that the 9.87MeV state cannot alone be responsible for the transition. Using the R-matrix framework we find that the inclusion of an extra 3/2+ state at Ex = 11.49(10)MeV is required in order to obtain a satisfactory description of the spectrum. Both states show large widths towards alpha decay, exhausting significant fractions of the Wigner limit, a typical signature of alpha clusterisation. The observed Gamow-Teller strength indicate large overlaps between the two states and the ground state of 11Be.

   nucl-exPRC(2019)·18 citations
2. 02*

   Measurement of Nuclear Transparency Ratios for Protons and Neutrons

   M. Duer · O. Hen · E. Piasetzky · L.B. Weinstein · A. Schmidt · I. Korover · E. O. Cohen · H. Hakobyan · the CLAS Collaboration

   This paper presents, for the first time, measurements of neutron transparency ratios for nuclei relative to C measured using the (e,e'n) reaction, spanning measured neutron momenta of 1.4 to 2.4 GeV/c. The transparency ratios were extracted in two kinematical regions, corresponding to knockout of mean-field nucleons and to the breakup of Short-Range Correlated nucleon pairs. The extracted neutron transparency ratios are consistent with each other for the two measured kinematical regions and agree with the proton transparencies extracted from new and previous (e,e'p) measurements, including those from neutron-rich nuclei such as lead. The data also agree with and confirm the Glauber approximation that is commonly used to interpret experimental data. The nuclear-mass-dependence of the extracted transparencies scales as A^{\alpha} with {\alpha} = -0.289 {\pm} 0.007, which is consistent with nuclear-surface dominance of the reactions.

   nucl-exnucl-thPLB(2019)·27 citations
3. 03*

   Statistical sensitivity of the nEDM apparatus at PSI to neutron mirror-neutron oscillations

   C. Abel🇬🇧 · N. Ayres🇬🇧 · G. Bison🇨🇭 · K. Bodek🇵🇱 · V. Bondar🇧🇪 · P.-J. Chiu🇨🇭 · M. Daum🇨🇭 · S. Emmenegger🇨🇭 · P. Flaux🇫🇷 · L. Ferraris-Bouchez🇫🇷 · W. C. Griffth🇬🇧 · N. Hild🇨🇭 and 24 other authors

   The neutron and its hypothetical mirror counterpart, a sterile state degenerate in mass, could spontaneously mix in a process much faster than the neutron $\beta$-decay. Two groups have performed a series of experiments in search of neutron - mirror-neutron ($n-n^{\prime }$) oscillations. They reported no evidence, thereby setting stringent limits on the oscillation time ${\tau }_{n{n}^{\prime }}$. Later, these data sets have been further analyzed by Berezhiani et al.(2009-2017), and signals, compatible with $n-n^{\prime }$ oscillations in the presence of mirror magnetic fields, have been reported. The Neutron Electric Dipole Moment Collaboration based at the Paul Scherrer Institute performed a new series of experiments to further test these signals. In this paper, we describe and motivate our choice of run configurations with an optimal filling time of $29$s, storage times of $180$s and $380$s, and applied magnetic fields of $10\mu$T and $20\mu$T. The choice of these run configurations ensures a reliable overlap in settings with the previous efforts and also improves the sensitivity to test the signals. We also elaborate on the technique of normalizing the neutron counts, making such a counting experiment at the ultra-cold neutron source at the Paul Scherrer Institute possible. Furthermore, the magnetic field characterization to meet the requirements of this $n-n^{\prime }$ oscillation search is demonstrated. Finally, we show that this effort has a statistical sensitivity comparable to the current leading constraints for $n-n^{\prime }$ oscillations.

   nucl-exphysics.ins-detEPJ Web Conf.(2019)·8 citations
4. 04*

   First calculation of $\hat{q}$ on a quenched SU(3) plasma

   Amit Kumar🇺🇸 · Abhijit Majumder🇺🇸 · Chiho Nonaka🇯🇵

   The jet transport coefficient $\hat{q}$ is the leading transport coefficient that controls the modification of hard jets produced in heavy-ion collisions. This coefficient is inherently non-perturbative, and hence, is challenging to compute from first principles. In this report, we present a perturbative quantum chromodynamics (pQCD) and lattice gauge theory based formulation to study $\hat{q}$. We formulate $\hat{q}$ within a 4-dimensional (4D) quenched SU(3) lattice. We consider a leading order diagram for a hard parton passing through the quark-gluon plasma. The non-perturbative part is expressed in terms of a non-local (two-point) Field-Strength-Field-Strength (FF) operator product which can be Taylor expanded after analytic continuation to the Euclidean region. Such an expansion allows us to write $\hat{q}$ in terms of the expectation of local operators. Finally, we present our results for $\hat{q}$ in a pure gluon plasma.

   ↳ nucl-thhep-latnucl-exPoS(2018)·9 citations
5. 05*

   Theory of two-pion photo- and electroproduction off the nucleon

   Helmut Haberzettl🇺🇸 · Kanzo Nakayama🇺🇸 · Yongseok Oh🇰🇷

   A theory of two-pion photo- and electroproduction off the nucleon is derived considering all explicit three-body mechanisms of the interacting $\pi \pi N$ system. The full three-body dynamics of the interacting $\pi \pi N$ system is accounted for by the Faddeev-type ordering structure of the Alt-Grassberger-Sandhas equations. The formulation is valid for hadronic two-point and three-point functions dressed by arbitrary internal mechanisms provided all associated electromagnetic currents are constructed to satisfy their respective (generalized) Ward-Takahashi identities. It is shown that coupling the photon to the Faddeev structure of the underlying hadronic two-pion production mechanisms results in a natural expansion of the full two-pion photoproduction current $M_{\pi \pi }^{\mu }$ in terms of multiple dressed loops involving two-body subsystem scattering amplitudes of the $\pi \pi N$ system that preserves gauge invariance as a matter of course order by order in the number of (dressed) loops. A closed-form expression is presented for the entire gauge-invariant current $M_{\pi \pi }^{\mu }$ with complete three-body dynamics. Individually gauge-invariant truncations of the full dynamics most relevant for practical applications at the no-loop, one-loop, and two-loop levels are discussed in detail. An approximation scheme to the full two-pion amplitude for calculational purposes is also presented. It approximates, systematically, the full amplitude to any desired order of expansion in the underlying hadronic two-body amplitude. Moreover, it allows for the approximate incorporation of all neglected higher-order mechanisms in terms of a phenomenological remainder current. The effect and phenomenological usefulness of this remainder current is assessed in a tree-level calculation of the $\gamma N\to KK\Xi$ reaction.

   ↳ nucl-thhep-phnucl-exPRD(2019)·9 citations
6. 06*

   Heavy quarkonia production at LHC and EIC using Basis Light-Front Quantization wavefunctions

   Guangyao Chen🇺🇸 · Yang Li🇺🇸 · Kirill Tuchin🇺🇸 · James Vary🇺🇸

   We study exclusive charmonium and bottomonium production in ultra-peripheral heavy-ion collisions and electron-ion collisions within the dipole picture. We employ heavy quarkonium light-front wavefunctions obtained within the basis light-front quantization framework, which has some features of the light-front holographic QCD. We focus on comparison with measurements of exclusive charmonium and bottomonium production in ultraperipheral $pp$, $p$Pb and PbPb collisions at LHC and find reasonable agreement with the cross sections. We also discuss the coherent production cross-section ratios of excited states to the ground state for charmonium and bottomonium, which exhibit insensitivity to the dipole model parameters. We show that electron-ion collisions provide an opportunity for a quantitative study of heavy quarkonium structure.

   ↳ nucl-thnucl-exPRC(2019)·18 citations
7. 07*

   Approximate sum rule for the electric dipole moment of light nuclei

   Nodoka Yamanaka🇫🇷

   The measurement of the electric dipole moment (EDM) is an excellent test of the standard model of particle physics, and the detection of a finite value is signal of a new source of CP violation beyond it. Among systems for which the EDM can be measured, light nuclei are particularly interesting due to their high sensitivity to new physics. In this proceedings contribution, we examine the sensitivity of the EDM of several light nuclei to the CP-odd one pion-exchange nucleon-nucleon interaction within the cluster model. We suggest an approximate sum rule for the nuclear EDM.

   ↳ nucl-thhep-exhep-phnucl-exSpringer Proc.Phys.(2020)·0 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.