Fri·Dec 1, 2017Friday·December 1, 2017

1. 01*

   Cross section of $\alpha$-induced reactions on iridium isotopes obtained from thick target yield measurement for the astrophysical $\gamma$ process

   T. Szücs🇭🇺 · G. G. Kiss🇭🇺 · Gy. Gyürky🇭🇺 · Zs. Fülöp🇭🇺 · Z. Halász🇭🇺 · T. Rauscher🇨🇭

   The stellar reaction rates of radiative $\alpha$-capture reactions on heavy isotopes are of crucial importance for the $\gamma$ process network calculations. These rates are usually derived from statistical model calculations, which need to be validated, but the experimental database is very scarce. This paper presents the results of $\alpha$-induced reaction cross section measurements on iridium isotopes carried out at first close to the astrophysically relevant energy region. Thick target yields of ${}^{191}$Ir($\alpha$,$\gamma$)${}^{195}$Au, ${}^{191}$Ir($\alpha$,n)${}^{194}$Au, ${}^{193}$Ir($\alpha$,n)${}^{196m}$Au, ${}^{193}$Ir($\alpha$,n)${}^{196}$Au reactions have been measured with the activation technique between E${}_{\alpha }=13.4$ MeV and 17 MeV. For the first time the thick target yield was determined with X-ray counting. This led to a previously unprecedented sensitivity. From the measured thick target yields, reaction cross sections are derived and compared with statistical model calculations. The recently suggested energy-dependent modification of the $\alpha$+nucleus optical potential gives a good description of the experimental data.

   nucl-exPLB(2018)·14 citations
2. 02*

   Initial Results from the Majorana Demonstrator

   T.S. Caldwell🇺🇸 · N. Abgrall🇺🇸 · S.I. Alvis🇺🇸 · I.J. Arnquist🇺🇸 · F.T. Avignone III🇺🇸 · A.S. Barabash🇷🇺 · C.J. Barton🇺🇸 · F.E. Bertrand🇺🇸 · T. Bode🇩🇪 · B. Bos🇺🇸 · A.W. Bradley🇺🇸 · V. Brudanin🇷🇺 and 60 other authors

   The MAJORANA Collaboration has assembled an array of high purity Ge detectors to search for neutrinoless double-beta decay in ${}^{76}$Ge with the goal of establishing the required background and scalability of a Ge-based next-generation ton-scale experiment. The MAJORANA DEMONSTRATOR consists of 44 kg of high-purity Ge (HPGe) detectors (30 kg enriched in ${}^{76}$Ge) with a low-noise p-type point contact (PPC) geometry. The detectors are split between two modules which are contained in a single lead and high-purity copper shield at the Sanford Underground Research Facility in Lead, South Dakota. Following a commissioning run that started in June 2015, the full detector array has been acquiring data since August 2016. We will discuss the status of the MAJORANA DEMONSTRATOR and initial results from the first physics run; including current background estimates, exotic low-energy physics searches, projections on the physics reach of the DEMONSTRATOR, and implications for a ton-scale Ge-based neutrinoless double-beta decay search.

   ↳ physics.ins-detnucl-exJ.Phys.Conf.Ser.(2020)·0 citations
3. 03*

   Fitting and selecting scattering data

   Enrique Ruiz Arriola🇪🇸 · Jose Enrique Amaro🇪🇸 · Rodrigo Navarro Perez🇺🇸

   The main purpose of scattering experiments is to unveil the underlying structure of the colliding particles and their interaction. Typically one measures scattering observables (cross sections and polarizations) at discrete angles and energies and mutually consistent data may validate or falsify proposed theories or models. However, the accumulation of data from different laboratories while potentially improves the statistical significance it may sometimes generate mutually inconsistent data as a side-effect. Thus, some decision has to be made on what are the maximal amount of data which are mutually compatible. We show elastic $\pi N$ and $NN$ scattering as prominent examples where this selection is called for. We discuss how it can be done in a self-consistent manner invoking a principle of maximal consensus of the database and with the help of a sufficiently flexible model involving a minimal number of theoretical assumptions. In the NN case this has become possible with a combination of long distance field theoretical constraints at the hadronic level such as pion exchanges and electromagnetic effects and a coarse graining of the unknown interaction over the shortest de Broglie wavelength being probed in the scattering process.

   ↳ nucl-thhep-phnucl-exPoS(2018)·3 citations
4. 04*

   Studies of mesic atoms and nuclei

   Eliahu Friedman🇮🇱 · Avraham Gal🇮🇱 · Aleš Cieplý🇨🇿 · Jaroslava Hrtánková🇨🇿 · Jiří Mareš🇨🇿

   $K^{-}$ mesons offer a unique setting where mesic atoms have been studied both experimentally and theoretically, thereby placing constraints on the possible existence and properties of meson-nuclear quasibound states. Here we review progress in this field made recently by the Jerusalem--Prague Collaboration using near-threshold $K^{-}N$ scattering amplitudes generated in several meson--baryon coupled channels models inspired by a chiral EFT approach. Our own procedure of handling subthreshold kinematics self consistently is used to transform these free-space energy dependent amplitudes to in-medium density dependent amplitudes from which $K^{-}$ optical potentials are derived. To fit the world data of kaonic atoms, these single-nucleon optical potentials are augmented by multi-nucleon terms. It is found that only two of the studied models reproduce also the single-nucleon absorption fractions available from old bubble chamber experiments. These two models are then checked for possible $K^{-}$ nuclear quasibound states, despite realizing that $K^{-}$ optical potentials are not constrained by kaonic atom data at densities exceeding half nuclear-matter density. We find that when such states exist, their widths are invariably above 100 MeV, forbiddingly large to allow observation. Multi-nucleon absorption is found to be substantial in this respect. This suggests that observable strongly bound $K^{-}$ mesons are limited to the very light systems, such as $K^{-}pp$.

   ↳ nucl-thhep-phnucl-exPoS(2018)·4 citations
5. 05*

   Comprehensive Study of Observables in Compton Scattering on the Nucleon

   Harald W. Griesshammer (George Washington U.)🇺🇸 · Judith A. McGovern (U. of Manchester)🇬🇧 · Daniel R. Phillips (Ohio U.)🇺🇸

   We present an analysis of $13$ observables in Compton scattering on the proton. Cross sections, asymmetries with polarised beam and/or targets, and polarisation-transfer observables are investigated for energies up to the $\Delta (1232)$ resonance to determine their sensitivity to the proton's dipole scalar and spin polarisabilities. The Chiral Effective Field Theory Compton amplitude we use is complete at N${}^4$LO, $\mathcal{O}(e^2{\delta }^4)$, for photon energies $\omega \sim m_{\pi }$, and so has an accuracy of a few per cent there. At photon energies in the resonance region it is complete at NLO, $\mathcal{O}(e^2{\delta }^0)$, and so its accuracy there is about $20$\%. We find that for energies from pion-production threshold to about $250\mathrm{MeV}$, multiple asymmetries have significant sensitivity to presently ill-determined combinations of proton spin polarisabilities. We also argue that the broad outcomes of this analysis will be replicated in complementary theoretical approaches, e.g., dispersion relations. Finally, we show that below the pion-production threshold, $6$ observables suffice to reconstruct the Compton amplitude, and above it $11$ are required. Although not necessary for polarisability extractions, this opens the possibility to perform "complete" Compton-scattering experiments. An interactive Mathematica notebook, including results for the neutron, is available from judith.mcgovern@manchester.ac.uk .

   ↳ nucl-thhep-phnucl-exEPJA(2018)·16 citations
6. 06*

   Charmed-baryon production in antiproton-proton collisions within an effective Lagrangian model

   R. Shyam🇮🇳

   We study the productions of charmed baryons ${\bar{\Lambda }}_c^{-}{\Lambda }_c^{+}$, ${\bar{\Lambda }}_c^{-}{\Sigma }_c^{+}$, and ${\bar{\Sigma }}^{-}{\Sigma }_c^{+}$ in the antiproton-proton collisions within an effective Lagrangian model that has only the baryon-meson degrees of freedom and involves the physical hadron masses. The baryon production proceeds via the $t$-channel exchanges of $D^0$ and $D^{\ast 0}$ mesons in the initial collision of the antiproton with the target proton. The distortion effects in the initial and final states are accounted for by using an eikonal approximation-based procedure. We find that the reaction amplitudes of all the production channels are dominated by the $D^{\ast 0}$ meson-exchange diagrams. We discuss the relative roles of tensor and vector components of the $D^{\ast 0}$ coupling in the $D^{\ast 0}$ meson-exchange component of the total production cross sections. The magnitudes of the cross sections are predicted for each final state for the range of beam momenta of relevance to the $\bar{P}ANDA$ experiment.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2017)·6 citations
7. 07*

   Possibility of shears mechanism due to attractive interaction in the island of $A$ $\sim$ 140 region

   S. Rajbanshi

   The present work identify an island in the values of dimensionless parameter $\chi$ as +0.10 $<$ $\chi$ $<$ +0.55 outside which no magnetic rotational (MR) bands due to the repulsive interaction would be observed. The semi-classical calculations within the hybrid shears mechanism with the principal axis cranking model (HSPAC) reveal the possibility of the shears band due to the attractive interaction for nuclei in A $\sim$ 140 region. Though the limited information exists in literature, the HSPAC calculation exhibits the dipole bands above the 4389-keV and 4160-keV excited states in ${}^{145}$Sm and ${}^{146}$Eu nuclei, respectively, demand their candidature of the attractive shears bands. Other interesting consequence of the HSPAC calculations is the increasing nature of the $B(M1)$ and $B(E2)$ transition strengths with spin unlike the decreasing nature of the transition strengths ($B(M1)$ and $B(E2)$ values) of the MR bands. Thus measurement of the transition probability has been required on urgent basis to validate the strong candidature of such an extreme excitation mechanism in ${}^{145}$Sm and ${}^{146}$Eu nuclei.

   ↳ nucl-thnucl-ex1 citation

* 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.