Tue·Nov 2, 2021Tuesday·November 2, 2021

1. 01*

   Experimental investigation of ground-state properties of ${}^7$H with transfer reactions

   M. Caamaño🇪🇸 · T. Roger🇫🇷 · A. M. Moro🇪🇸 · G. F. Grinyer🇫🇷 · J. Pancin🇫🇷 · S. Bagchi🇳🇱 · S. Sambi🇧🇪 · J. Gibelin🇫🇷 · B. Fernandez-Dominguez🇪🇸 · N. Itagaki🇯🇵 · J. Benlliure🇪🇸 · D. Cortina-Gil🇪🇸 and 9 other authors

   The properties of nuclei with extreme neutron-to-proton ratios, far from those naturally occurring on Earth, are key to understand nuclear forces and how nucleons hold together to form nuclei. ${}^7$H, with six neutrons and a single proton, is the nuclear system with the most unbalanced neutron-to-proton ratio known so far. However, its sheer existence and properties are still a challenge for experimental efforts and theoretical models. Here we report experimental evidences on the formation of ${}^7$H as a resonance, detected with independent observables, and the first measurement of the structure of its ground state. The resonance is found at $\sim$0.7 MeV above the ${}^3$H+4n mass, with a narrow width of $\sim$0.2 MeV and a $1/2^{+}$ spin and parity. These data are consistent with a ${}^7$H as a ${}^3$H core surrounded by an extended four-neutron halo, with a unique four-neutron decay and a relatively long half-life thanks to neutron pairing; a prime example of new phenomena occurring in what would be the most pure-neutron nuclear matter we can access in the laboratory.

   nucl-exPLB(2022)·2 citations
2. 02*

   Multi-differential studies to explore strangeness enhancement in pp with ALICE at the LHC

   Francesca Ercolessi (on behalf of the ALICE Collaboration)🇮🇹

   The study of energy and multiplicity dependence of strange hadron production in proton-proton collisions provides a powerful tool to understand similarities and differences between small and large collision systems. In order to better understand the origin of strangeness enhancement in pp new multi-differential analyses have been performed. The first separates the contribution of soft and hard processes, such as jets, to strange hadron production through two-particle correlation techniques. The second exploits the concept of the effective energy available for particle production in the event, which is estimated by an anti-correlation with the energy deposited in ALICE's Zero Degree Calorimeters. The results indicate that strangeness production emerges from the growth of the underlying event and confirm it is related to the final state multiplicity.

   ↳ hep-exnucl-exSciPost Phys.Proc.(2022)·0 citations
3. 03*

   The Selena Neutrino Experiment

   Alvaro E. Chavarria🇺🇸

   Imaging sensors made from an ionization target layer of amorphous selenium (aSe) coupled to a silicon complementary metal-oxide-semiconductor (CMOS) active pixel array for charge readout are a promising technology for neutrino physics. The high spatial resolution in a solid-state target provides unparalleled rejection of backgrounds from natural radioactivity in the search for neutrinoless $\beta \beta$ decay and for solar neutrino spectroscopy with ${}^{82}$Se. We present results on the ionization response of aSe measured from the photoabsorption of 122 keV $\gamma$ rays in a single-pixel device. We report on the progress in the fabrication and testing of the first prototype imaging sensors based on the Topmetal-II${}^{-}$ pixelated CMOS charge readout chip. We explore the scientific reach of a large neutrino detector with the proposed technology based on our experimental understanding of the sensor performance.

   ↳ physics.ins-dethep-exnucl-exJ.Phys.Conf.Ser.(2021)·4 citations
4. 04*

   Forward coherent $\omega$ and $\varphi$ mesons production in the photon induced reaction on nuclei

   Swapan Das🇮🇳

   The differential cross sections of the forward coherent $\omega$ and $\varphi$ mesons photoproduction from nuclei have been calculated using the Glauber model for the nuclear reaction. The measured cross section of the elementary reaction, i.e., $\gamma N\to \omega (\varphi )N$ reaction, are used as input in the Glauber model. The experimentally determined free-space scattering parameters of the quoted mesons have been used to evaluate the meson nucleus interactions. The sensitivity of the cross section to the Fermi-motion of the nucleon and the nucleon-nucleon short-range correlation in the nucleus are studied. The calculated results are compared with the measured cross sections.

   ↳ nucl-thnucl-exPhys.Scripta(2021)·2 citations
5. 05*

   Complementarity between neutrinoless double beta decay and collider searches for heavy neutrinos in composite-fermion models

   S. Biondini🇨🇭 · S. Dell'Oro🇮🇹 · R. Leonardi🇮🇹 · S. Marcocci🇺🇸 · O. Panella🇮🇹 · M. Presilla🇮🇹 · F. Vissani🇮🇹

   Composite-fermion models predict excited quarks and leptons with mass scales which can potentially be observed at high-energy colliders like the LHC; the most recent exclusion limits from the CMS and ATLAS Collaborations corner excited-fermion masses and the compositeness scale to the multi-TeV range. At the same time, hypothetical composite Majorana neutrinos would lead to observable effects in neutrinoless double beta decay ($0\nu \beta \beta$) experiments. In this work, we show that the current composite-neutrino exclusion limit $M_N>4.6$ TeV, as extracted from direct searches at the LHC, can indeed be further improved to $M_N>8.8$ TeV by including the bound on the nuclear transition ${}^{136}$Xe $\to$ ${}^{136}$Ba $+2e^{-}$. Looking ahead, the forthcoming HL-LHC will allow probing a larger portion of the parameter-space, nevertheless, it will still benefit from the complementary limit provided by $0\nu \beta \beta$ future detectors to explore composite-neutrino masses up to $12.6$ TeV.

   ↳ hep-phnucl-exnucl-th4 citations
6. 06*

   Improved search for neutron to mirror-neutron oscillations in the presence of mirror magnetic fields with a dedicated apparatus at the PSI UCN source

   N.J.Ayres🇨🇭 · Z.Berezhiani🇮🇹 · R.Biondi🇮🇹 · G.Bison🇨🇭 · K.Bodek🇵🇱 · V.Bondar🇨🇭 · P.-J.Chiu🇨🇭 · M.Daum🇨🇭 · R.T.Dinani🇧🇪 · C.B.Doorenbos🇨🇭 · S.Emmenegger🇨🇭 · K.Kirch🇨🇭 and 13 other authors

   While the international nEDM collaboration at the Paul Scherrer Institut (PSI) took data in 2017 that covered a considerable fraction of the parameter space of claimed potential signals of hypothetical neutron ($n$) to mirror-neutron ($n^{\prime }$) transitions, it could not test all claimed signal regions at various mirror magnetic fields. Therefore, a new study of $n-n^{\prime }$ oscillations using stored ultracold neutrons (UCNs)is underway at PSI, considerably expanding the reach in parameter space of mirror magnetic fields ($B^{\prime }$) and oscillation time constants (${\tau }_{n{n}^{\prime }}$). The new apparatus is designed to test for the anomalous loss of stored ultracold neutrons as a function of an applied magnetic field. The experiment is distinguished from its predecessors by its very large storage vessel (1.47\,m${}^3$), enhancing its statistical sensitivity. In a test experiment in 2020 we have demonstrated the capabilities of our apparatus. However, the full analysis of our recent data is still pending. Based on already demonstrated performance, we will reach a sensitivity to oscillation times ${\tau }_{n{n}^{\prime }}/\sqrt{\cos (\beta )}$ well above hundred seconds, with $\beta$ being the angle between $B^{\prime }$ and the applied magnetic field $B$. The scan of $B$ will allow the finding or the comprehensive exclusion of potential signals reported in the analysis of previous experiments and suggested to be consistent with neutron to mirror-neutron oscillations.

   ↳ physics.ins-dethep-exnucl-exSymmetry(2022)·32 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.