Wed·Jan 20, 2021Wednesday·January 20, 2021

1. 01*

   First detection of collective oscillations of a stored deuteron beam with an amplitude close to the quantum limit

   J. Slim🇩🇪 · N.N. Nikolaev🇷🇺 · F. Rathmann🇩🇪 · A. Wirzba🇩🇪 · A. Nass🇩🇪 · V. Hejny🇩🇪 · J. Pretz🇩🇪 · H. Soltner🇩🇪 · F. Abusaif🇩🇪 · A. Aggarwal🇵🇱 · A. Aksentev🇷🇺 · A. Andres🇩🇪 and 32 other authors

   We investigated coherent betatron oscillations of a deuteron beam in the storage ring COSY, excited by a detuned radio-frequency Wien filter. The beam oscillations were detected by conventional beam position monitors. With the currently available apparatus, we show that oscillation amplitudes down to \SI{1}{\micro \meter} can be detected. The interpretation of the response of the stored beam to the detuned radio-frequency Wien filter is based on simulations of the beam evolution in the lattice of the ring and realistic time-dependent 3D field maps of the Wien filter. Future measurements of the electric dipole moment of protons will, however, require control of the relative position of counter-propagating beams in the sub-picometer range. Since here the stored beam can be considered as a rarefied gas of uncorrelated particles, we moreover demonstrate that the amplitudes of the zero-point (ground state) betatron oscillations of individual particles are only a factor of about 10 larger than the Heisenberg uncertainty limit. As a consequence of this, we conclude that quantum mechanics does not preclude the control of the beam centroids to sub-picometer accuracy. The smallest Lorentz force exerted on a single particle that we have been able to determine is \SI{10}{aN}.

   nucl-exquant-phPhys.Rev.Accel.Beams(2021)·16 citations
2. 02*

   Feasibility of an experimental search for a resonance of a pion and a light nucleus

   Hiroyuki Fujioka🇯🇵

   A hypothesis is proposed herein, suggesting that a pion-nuclear resonance may be observed in the $\alpha +d\to {}^6\mathrm{Li}(3.563)+{\pi }^0$ reaction. The resonance has a $\pi NN\alpha$ structure, containing $\alpha NN$ and $\pi NN$ subsystems. The former corresponds to the $A=6$ isotriplet (${}^6{\mathrm{He}}_{\text{g.s.}}$, ${}^6\mathrm{Li}(3.563)$, ${}^6{\mathrm{Be}}_{\text{g.s.}}$), whereas the latter is a hypothetical $NN$-decoupled dibaryon. We propose an experiment to search for this resonance using the ${}^7\mathrm{Li}(p,d)$ reaction.

   nucl-exnucl-thPTEP(2021)·0 citations
3. 03*

   Second and fourth moments of the charge density and neutron-skin thickness of atomic nuclei

   Tomoya Naito🇯🇵 · Gianluca Colò🇮🇹 · Haozhao Liang🇯🇵 · Xavier Roca-Maza🇮🇹

   A method is presented to extract the neutron-skin thickness of atomic nuclei from the second and fourth moments of the electric charge distribution. We show that the value of the proton fourth moment must be independently known in order to estimate the neutron skin thickness experimentally. To overcome this problem, we propose the use of a strong linear correlation among the second and fourth moments of the proton distribution as calculated with several energy density functionals of common use. We take special care in estimating the errors associated with the different contributions to the neutron radius and show, for the first time, the analytic expressions for the spin-orbit contribution to the charge fourth moments of neutrons and protons. To reduce the uncertainty on the extraction of the neutron radius, two neighboring even-even isotopes are used. Nevertheless, the error on the fourth moment of the proton distribution, even if determined or assumed with large accuracy, dominates and prevents the present method from being applied for a sound determination of the neutron skin thickness.

   ↳ nucl-thnucl-exPRC(2021)·19 citations
4. 04*

   Combined Constraints on First Generation Leptoquarks

   Andreas Crivellin · Dario Müller · Luc Schnell

   In this article we perform a combined analysis of low energy precision constraints and LHC searches for leptoquarks which couple to first generation fermions. Considering all ten leptoquark representations, five scalar and five vector ones, we study at the precision frontier the constraints from $K\to \pi \nu \nu$, $K\to \pi e^{+}{e}^{-}$, $K^0-{\bar{K}}^0$ and $D^0-{\bar{D}}^0$ mixing, as well as from experiments searching for parity violation (APV and QWEAK). We include LHC searches for $s$-channel single resonant production, pair production and Drell-Yan-like signatures of leptoquarks. Interestingly, we find that the recent non-resonant di-lepton analysis of ATLAS provides stronger bounds than the resonant searches recasted so far to constrain $t$-channel production of leptoquarks. Taking into account all these bounds, we observe that none of the leptoquark representations can address the so-called "Cabibbo angle anomaly" via a direct contribution to super-allowed beta decays.

   ↳ hep-phhep-exnucl-exnucl-thPhys. Rev. D 103, 115023 (2021)

* 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.