Tue·Sep 9, 2014Tuesday·September 9, 2014

1. 01*

   Broken axial symmetry as essential feature to predict radiative capture in heavy nuclei

   Eckart Grosse🇩🇪 · Arnd R. Junghans🇩🇪 · Ralph Massarczyk🇺🇸

   Cross sections for neutron capture in the range of unresolved resonances are predicted for more than 140 spin-0 target nuclei with A > 50. Allowing the breaking of spherical and axial symmetry in nearly all these nuclei a combined parameterization for both, level density and photon strength is obtained which employs a surprisingly small number of parameters only. The strength functions used are based on a global fit to IVGDR shapes by the sum of three Lorentzians. They are based on theoretical predictions for the A-dependence of pole energies and spreading widths and add up to the TRK sum rule. For the small spins reached by capture resonance spacings are well described by a level density parameter close to the nuclear matter value; a significant collective enhancement is apparent due to the deviation from axial symmetry. Reliable predictions for compound nuclear reactions also outside the valley of stability (as important for nuclear astrophysics and for the transmutation of nuclear waste) are expected to result from the global parameterization presented.

   nucl-exastro-ph.SRnucl-thPLB(2014)·8 citations
2. 02*

   Isolation of Flow and Nonflow Correlations by Two- and Four-Particle Cumulant Measurements of Azimuthal Harmonics in $\sqrt{s_{{}_{\mathrm{NN}}}}=$ 200 GeV Au+Au Collisions

   N. M. Abdelwahab · L. Adamczyk · J. K. Adkins · G. Agakishiev · M. M. Aggarwal · Z. Ahammed · I. Alekseev · J. Alford · C. D. Anson · A. Aparin · D. Arkhipkin · E. C. Aschenauer and 339 other authors

   A data-driven method was applied to measurements of Au+Au collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=$ 200 GeV made with the STAR detector at RHIC to isolate pseudorapidity distance $\Delta \eta$-dependent and $\Delta \eta$-independent correlations by using two- and four-particle azimuthal cumulant measurements. We identified a component of the correlation that is $\Delta \eta$-independent, which is likely dominated by anisotropic flow and flow fluctuations. It was also found to be independent of $\eta$ within the measured range of pseudorapidity $|\eta |<1$. The relative flow fluctuation was found to be $34\%\pm 2\%(stat.)\pm 3\%(sys.)$ for particles of transverse momentum $p_T$ less than $2$ GeV/$c$. The $\Delta \eta$-dependent part may be attributed to nonflow correlations, and is found to be $5\%\pm 2\%(sys.)$ relative to the flow of the measured second harmonic cumulant at $|\Delta \eta |>0.7$.

   nucl-exPLB(2015)·19 citations
3. 03*

   Measurement of double-polarization asymmetries in the quasi-elastic ${}^3\overrightarrow{\mathrm{He}}(\vec{\mathrm{e}},{\mathrm{e}}^{\prime }\mathrm{d})$ process

   The Jefferson Lab Hall A Collaboration: M. Mihovilovič🇸🇮 · G. Jin🇺🇸 · E. Long🇺🇸 · Y.-W. Zhang · K. Allada🇺🇸 · B. Anderson🇺🇸 · J. R. M. Annand🇬🇧 · T. Averett🇺🇸 · W. Boeglin🇺🇸 · P. Bradshaw🇺🇸 · A. Camsonne🇺🇸 · M. Canan🇺🇸 and 86 other authors

   We present a precise measurement of double-polarization asymmetries in the ${}^3\overrightarrow{\mathrm{He}}(\vec{\mathrm{e}},{\mathrm{e}}^{\prime }\mathrm{d})$ reaction. This particular process is a uniquely sensitive probe of hadron dynamics in ${}^3\mathrm{He}$ and the structure of the underlying electromagnetic currents. The measurements have been performed in and around quasi-elastic kinematics at $Q^2=0.25(\mathrm{GeV}/c{)}^2$ for missing momenta up to $270\mathrm{MeV}/c$. The asymmetries are in fair agreement with the state-of-the-art calculations in terms of their functional dependencies on $p_{\mathrm{m}}$ and $\omega$, but are systematically offset. Beyond the region of the quasi-elastic peak, the discrepancies become even more pronounced. Thus, our measurements have been able to reveal deficiencies in the most sophisticated calculations of the three-body nuclear system, and indicate that further refinement in the treatment of their two- and/or three-body dynamics is required.

   nucl-exPRL(2014)·8 citations
4. 04*

   Photonuclear Reaction Cross Sections for Gallium Isotopes

   Serkan Akkoyun · Tuncay Bayram

   The photon induced reactions which are named as photonuclear reactions have a great importance in many field of nuclear, radiation physics and related fields. Since we have planned to perform photonuclear reaction on gallium target with bremmstrahlung photons from clinical linear accelerator in the future, the cross-sections of neutron (photo-neutron ({\gamma},xn)) and proton (photo-proton ({\gamma},xn)) productions after photon activation have been calculated by using TALYS 1.2 computer code in this study. The target nucleus has been considered gallium which has two stable isotopes, 69Ga and 71Ga. According to the results, we have seen that the calculations are in harmony in the limited literature values. Furthermore, the pre-equilibrium and compound process contributions to the total cross-section have been investigated.

   nucl-exJ.Phys.Conf.Ser.(2015)·1 citation
5. 05*

   Inclusive cross sections, charge ratio and double-helicity asymmetries for ${\pi }^{+}$ and ${\pi }^{-}$ production in $p$$+$$p$ collisions at $\sqrt{s}$=200 GeV

   A. Adare · C. Aidala · N.N. Ajitanand · Y. Akiba · R. Akimoto · H. Al-Ta'ani · J. Alexander · K.R. Andrews · A. Angerami · K. Aoki · N. Apadula · E. Appelt and 370 other authors

   We present the midrapidity charged pion invariant cross sections and the ratio of ${\pi }^{-}$-to-${\pi }^{+}$ production ($5<p_T<13$ GeV/$c$), together with the double-helicity asymmetries ($5<p_T<12$ GeV/$c$) in polarized $p$$+$$p$ collisions at $\sqrt{s}=200$ GeV. The cross section measurements are consistent with perturbative calculations in quantum chromodynamics within large uncertainties in the calculation due to the choice of factorization, renormalization, and fragmentation scales. However, the theoretical calculation of the ratio of ${\pi }^{-}$-to-${\pi }^{+}$ production when considering these scale uncertainties overestimates the measured value, suggesting further investigation of the uncertainties on the charge-separated pion fragmentation functions is needed. Due to cancellations of uncertainties in the charge ratio, direct inclusion of these ratio data in future parameterizations should improve constraints on the flavor dependence of quark fragmentation functions to pions. By measuring charge-separated pion asymmetries, one can gain sensitivity to the sign of $\Delta G$ through the opposite sign of the up and down quark helicity distributions in conjunction with preferential fragmentation of positive pions from up quarks and negative pions from down quarks. The double-helicity asymmetries presented are sensitive to the gluon helicity distribution over an $x$ range of $\sim$0.03--0.16.

   ↳ hep-exnucl-exPRD(2015)·25 citations
6. 06*

   Collective flow in ultrarelativistic ${}^3$He-Au collisions

   Piotr Bozek🇵🇱 · Wojciech Broniowski🇵🇱

   The triangular flow in ultrarelativistic ${}^3$He-Au collisions at RHIC energies is enhanced due to the triangular arrangement of the nucleon configurations in ${}^3$He. We study the fireball eccentricities in the Glauber Monte Carlo model and find that since the configurations of the projectile ${}^3$He are elongated triangles, the created fireball has a large ellipticity and a smaller triangularity. The dependence of the triangularity on centrality is weak, so it cannot be extracted from the centrality dependence of the triangular flow $v_3$, as it is dominated by the centrality dependence of the hydrodynamic response. We propose to look at the centrality dependence of the ratio $v_n\{4\}/v_n\{2\}$, where the uncertainties from the hydrodynamic response cancel, and show that the basic signature of the geometry-driven collective flow is the raise of the ratio $v_3\{4\}/v_3\{2\}$ with the number of participant nucleons for centralities less than 10%.

   ↳ nucl-thhep-phnucl-exPLB(2014)·37 citations
7. 07*

   Near-threshold J/Psi production in proton-nucleus collisions

   Yu. T. Kiselev🇷🇺 · E. Ya. Paryev🇷🇺 · Yu. M. Zaitsev🇷🇺

   We study the J/Psi production from nuclei near the kinematic threshold within the collision model, based on the nuclear spectral function, for incoherent primary proton-nucleon charmonium creation processes. The model takes into account the initial proton and final J/Psi absorption, target nucleon binding and Fermi motion, the formation length of J/Psi mesons as well as the effect of their nuclear mean-field potential on these processes. We calculate the A dependences of the absolute and relative (transparency ratio) charmonium yields as well as its excitation function within the different scenarios for the J/PsiN absorption cross section, for the J/Psi formation length and for J/Psi in-medium modification. We demonstrate that the former observables, on the one hand, are not practically affected by the charmonium formation length effects and, on the other hand, they are appreciably sensitive to the genuine J/PsiN absorption cross section at beam energies of interest, which means that these observables can be useful to help determine the above cross section from the comparison of the results of our calculations with the future data from the CBM experiment at FAIR-the upcoming accelerator facility at GSI-Darmstadt, Germany. We also show that the excitation function for J/Psi subthreshold production in pA reactions reveals some sensitivity to adopted its in-medium modification scenarios. Therefore, such observable may be an important tool to get valuable information on the charmonium in-medium properties.

   ↳ nucl-thhep-phnucl-exIJMPE(2014)·6 citations
8. 08*

   Heavy Mesons in Nuclear Matter and Nuclei

   Laura Tolos🇪🇸 · Daniel Cabrera🇩🇪 · Carmen Garcia-Recio🇪🇸 · Raquel Molina🇺🇸 · Juan Nieves🇪🇸 · Eulogio Oset🇪🇸 · Angels Ramos🇪🇸 · Olena Romanets🇳🇱 · Lorenzo Luis Salcedo🇪🇸 · Juan M. Torres-Rincon🇫🇷

   Heavy mesons in nuclear matter and nuclei are analyzed within different frameworks, paying a special attention to unitarized coupled-channel approaches. Possible experimental signatures of the properties of these mesons in matter are addressed, in particular in connection with the future FAIR facility at GSI.

   ↳ nucl-thhep-phnucl-exJ.Phys.Conf.Ser.(2014)·0 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.