Fri·Feb 19, 2016Friday·February 19, 2016

1. 01*

   NICA-MPD: azimuthal and femtoscopic particle correlations

   V. A. Okorokov (National Research Nuclear University MEPhI)🇷🇺

   The discussion is focused on the study of the fundamental symmetries ($\mathcal{P}/\mathcal{C}\mathcal{P}$) of QCD and geometry of the particle source. The combination of correlators corresponding to the absolute asymmetry of distribution of electrically charged particles with respect to the reaction plane in heavy ion collisions is studied. A significant decrease of the absolute asymmetry is observed in the intermediate energy range which can be considered as indication of possible transition to predominance of hadronic states over quark-gluon degrees of freedom in the mixed phase created in heavy ion collisions at intermediate energies. For the investigation of the energy evolution of the geometric properties of the particle source the use of femtoscopic radii scaled on the averaged radius of colliding ions is suggested. This approach allows the expansion of the set of interaction types, in particular, on the collisions of non-symmetrical ion beams which can be studied within the framework of common treatment. There is no sharp changing of femtoscopic parameter values with increasing of the initial energy. The suggestions are made for future advancement of these studies on NICA-MPD.

   nucl-exEPJA(2016)·1 citation
2. 02*

   First observation of low-energy {\gamma}-ray enhancement in the rare-earth region

   A. Simon · M. Guttormsen🇳🇴 · A.C. Larsen🇳🇴 · C.W. Beausang · P. Humby · J.T. Burke · R.J. Casperson🇺🇸 · R.O. Hughes🇺🇸 · T.J. Ross · J.M. Allmond🇺🇸 · R. Chyzh · M. Dag and 5 other authors

   The {\gamma}-ray strength function and level density in the quasi-continuum of 151,153Sm have been measured using BGO shielded Ge clover detectors of the STARLiTeR system. The Compton shields allow for an extraction of the {\gamma} strength down to unprecedentedly low {\gamma} energies of about 500 keV. For the first time an enhanced low- energy {\gamma}-ray strength has been observed in the rare-earth region. In addition, for the first time both the upbend and the well known scissors resonance have been observed simultaneously for the same nucleus. Hauser-Feshbach calculations show that this strength enhancement at low {\gamma} energies could have an impact of 2-3 orders of magnitude on the (n,{\gamma}) reaction rates for the r-process nucleosynthesis.

   nucl-exPRC(2016)·61 citations
3. 03*

   Alpha-particle clustering in excited expanding self-conjugate nuclei

   B. Borderie🇫🇷 · Ad. R. Raduta🇷🇴 · G. Ademard🇫🇷 · M. F. Rivet🇫🇷 · E. De Filippo🇮🇹 · E. Geraci🇮🇹 · N. Le Neindre🇫🇷 · G. Cardella🇮🇹 · G. Lanzalone🇮🇹 · I. Lombardo🇮🇹 · O. Lopez🇫🇷 · C. Maiolino🇮🇹 and 5 other authors

   The fragmentation of quasi-projectiles from the nuclear reaction 40Ca + 12C at 25 MeV/nucleon was used to produce alpha-emission sources. From a careful selection of these sources provided by a complete detection and from comparisons with models of sequential and simultaneous decays, strong indications in favour of $\alpha$-particle clustering in excited 16O, 20Ne and 24}Mg are reported.

   nucl-exEPJ Web Conf.(2016)·2 citations
4. 04*

   A reanalysis of radioisotope measurements of the ${}^9$Be$(\gamma ,n{)}^8$Be cross-section

   Alan E. Robinson🇺🇸

   The ${}^9$Be$(\gamma ,n{)}^8$Be reaction is enhanced by a near threshold $1/2^{+}$ state. Contradictions between existing measurements of this reaction cross-section affect calculations of astrophysical r-process yields, dark matter detector calibrations, and the theory of the nuclear structure of ${}^9$Be. Select well-documented radioisotope ${}^9$Be$(\gamma ,n)$ source yield measurements have been reanalyzed, providing a set of high-accuracy independently measured cross sections. A Breit-Wigner fit of these corrected measurements yields $E_R=1738.8\pm 1.9$ keV, ${\Gamma }_{\gamma }=0.771\pm 0.021$ eV, and ${\Gamma }_n=268\pm 15$ keV for the $1/2^{+}$ state. A virtual $1/2^{+}$ state is excluded with 99.3\% confidence.

   nucl-exastro-ph.IMastro-ph.SRPRC(2016)·22 citations
5. 05*

   $\eta$ MAID-2015: update with new data and new resonances

   V.L. Kashevarov🇩🇪 · L. Tiator🇩🇪 · M. Ostrick🇩🇪

   Recent data for $\eta$ and $\eta \prime$ photoproduction on protons obtained by the A2 Collaboration at MAMI are presented. The total cross section for $\eta$ photoproduction demonstrates a cusp at the energy corresponding to the $\eta \prime$ threshold. The new data and existing data from GRAAL, CBELSA/TAPS, and CLAS collaborations have been analyzed by an expansion in terms of associated Legendre polynomials. %A Legendre decomposition shows the sensitivity to small partial-wave contributions. The isobar model $\eta$MAID updated with $\eta \prime$ channel and new resonances have been used to fit the new data. The new solution $\eta$MAID-2015 reasonably good describes the data in the photon beam energy region up to 3.7 GeV.

   ↳ nucl-thnucl-exBled Workshops Phys.(2015)·16 citations
6. 06*

   Unfolding problem clarification and solution validation

   Nikolai Gagunashvili🇮🇸

   The unfolding problem formulation for correcting experimental data distortions due to finite resolution and limited detector acceptance is discussed. A novel validation of the problem solution is proposed. Attention is drawn to fact that different unfolded distributions may satisfy the validation criteria, in which case a conservative approach using entropy is suggested. The importance of analysis of residuals is demonstrated.

   ↳ physics.data-anastro-ph.IMhep-exnucl-ex+10 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.