Tue·Mar 3, 2015Tuesday·March 3, 2015

1. 01*

   KADoNiS-$p$: The astrophysical $p$-process database

   T. Szücs🇭🇺 · I. Dillmann🇩🇪 · R. Plag🇩🇪 · Zs. Fülöp

   The KADoNiS-$p$ project is an online database for cross sections relevant to the $p$-process. All existing experimental data was collected and reviewed. With this contribution a user-friendly database using the KADoNiS (Karlsruhe Astrophysical Database of Nucleosynthesis in Stars) framework is launched, including all available experimental data from (p,$\gamma$), (p,n), (p,$\alpha$), ($\alpha$,$\gamma$), ($\alpha$,n) and ($\alpha$,p) reactions in or close to the respective Gamow window with cut-off date of August 2012 (www.kadonis.org/pprocess).

   nucl-exNucl.Data Sheets(2014)·16 citations
2. 02*

   Analysing powers and spin correlations in deuteron-proton charge exchange at 726 MeV

   S. Dymov🇷🇺 · T. Azaryan🇷🇺 · Z. Bagdasarian🇬🇪 · S. Barsov🇷🇺 · J. Carbonell🇫🇷 · D. Chiladze🇬🇪 · R. Engels🇩🇪 · R. Gebel🇩🇪 · K. Grigoryev🇩🇪 · M. Hartmann🇩🇪 · A. Kacharava🇩🇪 · A. Khoukaz🇩🇪 and 27 other authors

   The charge exchange of vector polarised deuterons on a polarised hydrogen target has been studied in a high statistics experiment at the COSY-ANKE facility at a deuteron beam energy of Td = 726 MeV. By selecting two fast protons at low relative energy E_{pp}, the measured analysing powers and spin correlations are sensitive to interference terms between specific neutron-proton charge-exchange amplitudes at a neutron kinetic energy of Tn ~ 1/2 Td =363 MeV. An impulse approximation calculation, which takes into account corrections due to the angular distribution in the diproton, describes reasonably the dependence of the data on both E_{pp} and the momentum transfer. This lends broad support to the current neutron-proton partial-wave solution that was used in the estimation.

   nucl-exnucl-thPLB(2015)·3 citations
3. 03*

   Strange Baryonic Resonances and Resonances Coupling to Strange Hadrons at SIS Energies

   L. Fabbietti🇩🇪

   The role played by baryonic resonances in the production of final states containing strangeness for proton-proton reactions at 3.5 GeV measured by HADES is discussed by means of several very different measurements. First the associate production of $\Delta$ resonances accompanying final states with strange hadrons is presented, then the role of interferences among N${}^{\ast }$ resonances, as measured by HADES for the first time, is summarised. Last but not least the role played by heavy resonances, with a mass larger than $2$ GeV/c${}^2$ in the production of strange and non-strange hadrons is discussed. Experimental evidence for the presence of a $\Delta (2000{)}^{++}$ are presented and hypotheses are discussed employing the contribution of similar objects to populate the excesses measured by HADES for the $\Xi$ in A+A and p+A collisions and in the dilepton sector for A+A collisions. This extensive set of results helps to better understand the dynamic underlaying particle production in elementary reactions and sets a more solid basis for the understanding of heavy ion collisions at the same energies and even higher as planned at the FAIR facility.

   nucl-exAIP Conf.Proc.(2016)·5 citations
4. 04*

   $\Lambda (1405)$ observations in p+p and K${}^{-}$-induced reactions

   L. Fabbietti🇩🇪 · K. Pischicchia🇮🇹 · A. Scordo🇮🇹

   The $\Lambda (1405)$ production in p+p collisions at 3.5 GeV and K${}^{-}$-induced reactions is discussed. The shift of the measured spectral function of the $\Lambda (1405)$ in p+p reactions does not match either theoretical calculations for p+p reactions or experimental observation in previous K${}^{-}$-induced reactions. New experiments with stopped and in-flight $K^{-}$ are needed to study this initial state more in detail. The state of the art of the analysis is discussed.

   nucl-exHyperfine Interact.(2015)·0 citations
5. 05*

   Pion Production in High-Energy Neutrino Reactions with Nuclei

   Ulrich Mosel🇩🇪

   [Background] A quantitative understanding of neutrino interactions with nuclei is needed for precision era neutrino long baseline experiments (MINOS, NOvA, DUNE) which all use nuclear targets. Pion production is the dominant reaction channel at the energies of these experiments. [Purpose] Investigate the influence of nuclear effects on neutrino-induced pion production cross sections and compare predictions for pion-production with available data. [Method] The Giessen Boltzmann--Uehling--Uhlenbeck (GiBUU) model is used for the description of all incohrent channels in neutrino-nucleus reactions. [Results] Differential cross sections for charged and neutral pion production for the MINER$\nu$A neutrino and antineutrino flux are calculated. An estimate for the coherent cross section is obtained from a comparison of data with theoretical results. The invariant mass ($W$) distribution of the $\Delta$ resonances produced is analyzed. [Conclusions] Final state interactions affect the pion kinetic energy spectra significantly. The data for charged pion production at MINER$\nu$A are compatible with the results of calculations using elementary data taken from an old Argonne National Laboratory experiment. Remaining differences can be attributed to coherent production; the data for antineutrino induced neutral pion production, where no coherent contribution is present, are reproduced quite well. In contrast, the MiniBooNE data, taken at a lower energy, are consistently higher than the theoretical description. The analysis of $W$-distributions shows that experimental cuts on this quantity lead to shape distortions for nuclear targets.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2015)·26 citations
6. 06*

   Neutron-proton effective mass splitting in neutron-rich matter and its impacts on nuclear reactions

   Bao-An Li🇺🇸 · Lie-Wen Chen🇨🇳

   The neutron-proton effective mass splitting in neutron-rich nucleonic matter reflects the space-time nonlocality of the isovector nuclear interaction. It affects the neutron/proton ratio during the earlier evolution of the Universe, cooling of protoneutron stars, structure of rare isotopes and dynamics of heavy-ion collisions. While there is still no consensus on whether the neutron-proton effective mass splitting is negative, zero or positive and how it depends on the density as well as the isospin-asymmetry of the medium, significant progress has been made in recent yeas in addressing these issues. We first recall the connections among the neutron-proton effective mass splitting, the momentum dependence of the isovector potential and the density dependence of the symmetry energy. We then make a few observations about the progress in calculating the neutron-proton effective mass splitting using various nuclear many-body theories and its effects on the isospin-dependence of in-medium nucleon-nucleon cross sections. Perhaps, our most reliable knowledge so far about the neutron-proton effective mass splitting at saturation density of nuclear matter comes from optical model analyses of huge sets of nucleon-nucleus scattering data accumulated over the last five decades. The momentum dependence of the symmetry potential from these analyses provide a useful boundary condition at saturation density for calibrating nuclear many-body calculations. Several observables in heavy-ion collisions have been identified as sensitive probes of the neutron-proton effective mass splitting in dense neutron-rich matter based on transport model simulations. We review these observables and comment on the latest experimental findings.

   ↳ nucl-thastro-ph.SRnucl-exMod.Phys.Lett.A(2015)·32 citations
7. 07*

   Cosmic-ray induced background intercomparison with actively shielded HPGe detectors at underground locations

   T. Szücs🇭🇺 · D. Bemmerer🇩🇪 · T. P. Reinhardt🇩🇪 · K. Schmidt🇩🇪 · M. P. Takács🇩🇪 · A. Wagner🇩🇪 · L. Wagner🇩🇪 · D. Weinberger🇩🇪 · K. Zuber🇩🇪

   The main background above 3\,MeV for in-beam nuclear astrophysics studies with $\gamma$-ray detectors is caused by cosmic-ray induced secondaries. The two commonly used suppression methods, active and passive shielding, against this kind of background were formerly considered only as alternatives in nuclear astrophysics experiments. In this work the study of the effects of active shielding against cosmic-ray induced events at a medium deep location is performed. Background spectra were recorded with two actively shielded HPGe detectors. The experiment was located at 148\,m below the surface of the Earth in the Reiche Zeche mine in Freiberg, Germany. The results are compared to data with the same detectors at the Earth's surface, and at depths of 45\,m and 1400\,m, respectively.

   ↳ physics.ins-detastro-ph.IMnucl-exEPJA(2015)·9 citations
8. 08*

   Hydrodynamic modeling of 3He-Au collisions at sqrt(sNN)=200 GeV

   Piotr Bozek🇵🇱 · Wojciech Broniowski🇵🇱

   Collective flow and femtoscopy in ultrarelativistic 3He-Au collisions are investigated within the 3+1-dimensional (3+1D) viscous event-by-event hydrodynamics. We evaluate elliptic and triangular flow coefficients as functions of the transverse momentum. We find the typical long-range ridge structures in the two-particle correlations in the relative azimuth and pseudorapidity, in the pseudorapidity directions of both Au and 3He. We also make predictions for the pionic interferometric radii, which decrease with the transverse momentum of the pion pair. All features found hint on collectivity of the dynamics of the system formed in 3He-Au collisions, with hydrodynamics leading to quantitative agreement with the up-to-now released data.

   ↳ nucl-thnucl-exPLB(2015)·29 citations
9. 09*

   Constraining supernova equations of state with equilibrium constants from heavy-ion collisions

   Matthias Hempel🇨🇭 · Kris Hagel🇺🇸 · Joseph Natowitz🇺🇸 · Gerd Röpke🇩🇪 · Stefan Typel🇩🇪

   Cluster formation is a fundamental aspect of the equation of state (EOS) of warm and dense nuclear matter such as can be found in supernovae (SNe). Similar matter can be studied in heavy-ion collisions (HIC). We use the experimental data of Qin et al. [Phys. Rev. Lett. 108, 172701 (2012)] to test calculations of cluster formation and the role of in-medium modifications of cluster properties in SN EOSs. For the comparison between theory and experiment we use chemical equilibrium constants as the main observables. This reduces some of the systematic uncertainties and allows deviations from ideal gas behavior to be identified clearly. In the analysis, we carefully account for the differences between matter in SNe and HICs. We find that, at the lowest densities, the experiment and all theoretical models are consistent with the ideal gas behavior. At higher densities ideal behavior is clearly ruled out and interaction effects have to be considered. The contributions of continuum correlations are of relevance in the virial expansion and remain a difficult problem to solve at higher densities. We conclude that at the densities and temperatures discussed mean-field interactions of nucleons, inclusion of all relevant light clusters, and a suppression mechanism of clusters at high densities have to be incorporated in the SN EOS.

   ↳ nucl-thastro-ph.SRnucl-exPRC(2015)·56 citations
10. 10*

    Deeply virtual Compton scattering at small-$x$ in future Electron - Ion Colliders

    V. P. Goncalves🇧🇷 · D. S. Pires🇧🇷

    The study of exclusive processes in the future electron-ion ($eA$) colliders will be an important tool to investigate the QCD dynamics at high energies as they are in general driven by the gluon content of the target which is strongly subject to parton saturation effects. In this paper we compute the coherent and incoherent cross sections for the deeply virtual Compton scattering (DVCS) process relying on the color dipole approach and considering different models for the dipole - proton scattering amplitude. The dependencies of the cross sections with the energy, photon virtuality, nuclear mass number and squared momentum transfer are analysed in detail. We demonstrate that the ratio between the incoherent and coherent cross sections decreases at smaller values of $Q^2$ and increases at smaller values of $A$. We show that the coherent cross section dominates at small $t$ and exhibits the typical diffractive pattern, with the number of dips in the range $|t|\le 0.3$ GeV${}^2$ increasing with the mass atomic number. Our results indicate that the position of the dips are independent of the model used to treat the dipole - proton interaction as well as of the center-of-mass energy.

    ↳ hep-phhep-exnucl-exnucl-thPRC(2015)·19 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.