Fri·Jun 11, 2021Friday·June 11, 2021

1. 01*

   Elastic scattering measurements for the ${}^{10}$C + ${}^{208}$Pb system at E${}_{\mathrm{lab}}$ = 66 MeV

   R Linares🇧🇷 · Mandira Sinha🇮🇳 · E N Cardozo🇧🇷 · V Guimaraes🇧🇷 · G Rogachev🇺🇸 · J Hooker🇺🇸 · E Koshchiy🇺🇸 · T Ahn🇺🇸 · C Hunt🇺🇸 · H Jayatissa🇺🇸 · S Upadhyayula🇺🇸 · B Roeder🇺🇸 and 8 other authors

   Background: The influence of halo structure of ${}^6$He, ${}^8$B, ${}^{11}$Be and ${}^{11}$Li nuclei in several mechanisms such as direct reactions and fusion is already established, although not completely understood. The influence of the ${}^{10}$C Brunnian structure is less known. Purpose: To investigate the influence of the cluster configuration of ${}^{10}$C on the elastic scattering at an energy close to the Coulomb barrier. Methods: We present experimental data for the elastic scattering of the ${}^{10}$C+${}^{208}$Pb system at $E_{\mathrm{lab}}$ = 66 MeV. The data are compared to the three- and the four-body continuum-discretized coupled-channels calculations assuming ${}^9$B+$p$, ${}^6$Be+$\alpha$ and ${}^8$Be+$p$+$p$ configurations. Results: The experimental angular distribution of the cross sections shows the suppression of the Fresnel peak that is reasonably well reproduced by the continuum-discretized coupled-channels calculations. However, the calculations underestimate the cross sections at backward angles. Couplings to continuum states represent a small effect. Conclusions: The cluster configurations of ${}^{10}$C assumed in the present work are able to describe some of the features of the data. In order to explain the data at backward angles, experimental data for the breakup and an extension of theoretical formalism towards a four-body cluster seem to be in need to reproduce the measured angular distribution.

   nucl-exnucl-thPRC(2021)·10 citations
2. 02*

   Direct observation of the dead-cone effect in QCD

   ALICE Collaboration

   In particle collider experiments, elementary particle interactions with large momentum transfer produce quarks and gluons (known as partons) whose evolution is governed by the strong force, as described by the theory of quantum chromodynamics (QCD). These partons subsequently emit further partons in a process that can be described as a parton shower which culminates in the formation of detectable hadrons. Studying the pattern of the parton shower is one of the key experimental tools for testing QCD. This pattern is expected to depend on the mass of the initiating parton, through a phenomenon known as the dead-cone effect, which predicts a suppression of the gluon spectrum emitted by a heavy quark of mass $m_{\mathrm{Q}}$ and energy $E$, within a cone of angular size $m_{\mathrm{Q}}$/$E$ around the emitter. Previously, a direct observation of the dead-cone effect in QCD had not been possible, owing to the challenge of reconstructing the cascading quarks and gluons from the experimentally accessible hadrons. We report the direct observation of the QCD dead cone by using new iterative declustering techniques to reconstruct the parton shower of charm quarks. This result confirms a fundamental feature of QCD. Furthermore, the measurement of a dead-cone angle constitutes a direct experimental observation of the non-zero mass of the charm quark, which is a fundamental constant in the standard model of particle physics.

   nucl-exhep-exhep-phNature(2022)·189 citations
3. 03*

   ${}^{50}$Ti($d$,$p$)${}^{51}$Ti, single neutron energies in the $N=29$ isotones and the $N=32$ subshell closure

   L. A. Riley🇺🇸 · 1 J. M. Nebel-Crosson🇺🇸 · 1 K. T. Macon🇺🇸 · 2 G. W. McCann🇺🇸 · L. T. Baby🇺🇸 · D. Caussyn🇺🇸 · P. D. Cottle🇺🇸 · J. Esparza🇺🇸 · K. Hanselman🇺🇸 · K. W. Kemper🇺🇸 · E. Temanson🇺🇸 · I. Wiedenhöver🇺🇸

   A measurement of the ${}^{50}$Ti($d$,$p$)${}^{51}$Ti reaction at 16 MeV was performed using a Super Enge Split Pole Spectrograph to measure the magnitude of the $N=32$ subshell gap in Ti. Seven states were observed that had not been observed in previous ($d$,$p$) measurements, and the \textit{L} transfer values for six previously measured states were either changed or measured for the first time. The results were used to determine single neutron energies for the $p_{3/2}$, $p_{1/2}$ and $f_{5/2}$ orbitals. The resulting single neutron energies in ${}^{51}$Ti confirm the existence of the $N=32$ gap in Ti. These single neutron energies and those from previous measurements in ${}^{49}$Ca, ${}^{53}$Cr and ${}^{55}$Fe are compared to values from a covariant density functional theory calculation.

   nucl-exnucl-thPRC(2021)·9 citations
4. 04*

   New experimental limits on double-beta decay of osmium

   P. Belli🇮🇹 · R. Bernabei🇮🇹 · F. Cappella🇮🇹 · V. Caracciolo🇮🇹 · R. Cerulli🇮🇹 · F.A. Danevich🇺🇦 · A. Incicchitti🇮🇹 · D.V. Kasperovych🇺🇦 · V.V. Kobychev🇺🇦 · G.P. Kovtun🇺🇦 · N.G. Kovtun🇺🇦 · M. Laubenstein🇮🇹 and 6 other authors

   Double-beta processes in ${}^{184}$Os and ${}^{192}$Os were searched for over 15851 h at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. by using a 118 g ultra-pure osmium sample installed on the endcap of a 112 cm${}^3$ ultra-low-background broad-energy germanium detector. New limits on double-electron capture and electron capture with positron emission in ${}^{184}$Os were set at the level of $\lim T_{1/2}\sim 10^{16}-10^{17}$ yr. In particular the $2\nu$2K and $2\nu$KL decays of ${}^{184}$Os to the ground state of ${}^{184}$W are restricted as $T_{1/2}\ge 3.0\times 10^{16}$ yr and $T_{1/2}\ge 2.0\times 10^{16}$ yr, respectively. A lower limit on the half-life for the double-beta decay of ${}^{192}$Os to the first excited level of ${}^{192}$Pt was set as $\lim T_{1/2}=2.0\times 10^{20}$ yr at 90\% C.L.

   nucl-exJ.Phys.G(2021)·4 citations
5. 05*

   Computing Light-Front Wave Functions Without Light-Front Quantization: A Large-Momentum Effective Theory Approach

   Xiangdong Ji🇺🇸 · Yizhuang Liu🇵🇱

   Light-front wave functions play a fundamental role in the light-front quantization approach to QCD and hadron structure. However, a naive implementation of the light-front quantization suffers from various subtleties including the well-known zero-mode problem, the associated rapidity divergences which mixes ultra-violet divergences with infrared physics, as well as breaking of spatial rotational symmetry. We advocate that the light-front quantization should be viewed as an effective theory in which small $k^{+}$ modes have been effectively ``integrated out'', with an infinite number of renormalization constants. Instead of solving light-front quantized field theories directly, we make the large momentum expansion of the equal-time Euclidean correlation functions in instant quantization as an effective way to systematically calculate light-front correlations, including the light-front wave function amplitudes. This large-momentum effective theory accomplishes an effective light-front quantization through lattice QCD calculations. We demonstrate our approach using an example of a pseudo-scalar meson wave function.

   ↳ hep-phhep-latnucl-exnucl-thPRD(2022)·60 citations
6. 06*

   Preparation and Characterization of Thin Arsenic Targets for Stacked-Target Experiments

   Andrew S. Voyles🇺🇸 · Morgan B. Fox🇺🇸 · Jonathan T. Morrell🇺🇸 · Michael P. Zach · Evan K. Still · Lee A. Bernstein · Wesley D. Frey · Burton J. Mehciz

   Thin, uniform arsenic targets suitable for high-fidelity cross section measurements in stacked-target experiments were prepared by electrodeposition of arsenic on titanium backings from aqueous solutions. Electrolytic cells were constructed and capable of arsenic deposits ranging in mass from approximately 1$–$29 mg (0.32$–$7.2 mg/cm${}^2$, 0.57$–$13 $\mu$m). Examination of electrodeposit surface morphology by scanning electron microscopy and microanalysis was performed to investigate the uniformity of produced targets. Brief studies of plating growth dynamics and structural properties through cyclic voltammetry were also undertaken. Alternative target fabrication approaches by vapor deposition and electrodeposition from a deep eutectic solvent were additionally conducted. We further introduce a non-destructive characterization method for thin targets by neutron activation, which is independent of neutron flux shape, environmental factors, and source geometry, while correcting for any potential scatter or absorption effects.

   ↳ physics.ins-detnucl-ex1 citation
7. 07*

   Virtual Compton scattering at low energies with a positron beam

   B. Pasquini (U. Pavia and INFN, Pavia)🇮🇹 · M. Vanderhaeghen (U. Mainz, PRISMA)🇩🇪

   The Virtual Compton scattering (VCS) process at low energies explores the electromagnetic structure of the proton in terms of generalized polarizabilities (GPs). In the one-photon exchange approximation, VCS can be accessed with exclusive photon production reactions with electron or positron beams. The extraction of the GPs from VCS with electron beam has seen substantial progress over the past two decades. Nonetheless, a consistent picture of the GPs from low to higher scales demands further investigations. Complementary measurements with positron beams offer an unique possibility, and we present an impact study of such experimental program.

   ↳ hep-phhep-exnucl-exnucl-thEPJA(2021)·5 citations
8. 08*

   Event-by-event cumulants of azimuthal angles

   Ante Bilandzic🇩🇪

   We develop further the recently proposed event-by-event cumulants of azimuthal angles. The role of reflection symmetry, permutation symmetry, frame independence, and relabeling of particle indices in the cumulant expansion is discussed in detail. We argue that mathematical and statistical properties of cumulants are preserved if cumulants of azimuthal angles are defined event-by-event in terms of single-event averages of azimuthal angles, while they are violated in the traditional approach in which cumulants are defined in terms of all-event averages. We derive for the first time the example analytic solutions for the contribution of combinatorial background in the measured 2- and 3-particle correlations. We demonstrate that these solutions for the combinatorial background are universal as they can be written generically in terms of multiplicity-dependent combinatorial weights and marginal probability density functions of starting multivariate distribution. The new general results between multiparticle azimuthal correlators and flow amplitudes and symmetry planes are presented.

   ↳ hep-phhep-exnucl-exEPJC(2022)·5 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.