Tue·May 10, 2016Tuesday·May 10, 2016

1. 01*

   Pseudorapidity dependence of the anisotropic flow of charged particles in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV

   ALICE Collaboration

   We present measurements of the elliptic (${\mathrm{v}}_2$), triangular (${\mathrm{v}}_3$) and quadrangular (${\mathrm{v}}_4$) anisotropic azimuthal flow over a wide range of pseudorapidities ($-3.5<\eta <5$). The measurements are performed with Pb-Pb collisions at $\sqrt{s_{\text{NN}}}=2.76$ TeV using the ALICE detector at the Large Hadron Collider (LHC). The flow harmonics are obtained using two- and four-particle correlations from nine different centrality intervals covering central to peripheral collisions. We find that the shape of ${\mathrm{v}}_n(\eta )$ is largely independent of centrality for the flow harmonics $n=2-4$, however the higher harmonics fall off more steeply with increasing $|\eta |$. We assess the validity of extended longitudinal scaling of ${\mathrm{v}}_2$ by comparing to lower energy measurements, and find that the higher harmonic flow coefficients are proportional to the charged particle densities at larger pseudorapidities. Finally, we compare our measurements to both hydrodynamical and transport models, and find they both have challenges when it comes to describing our data.

   nucl-exhep-exPLB(2016)·87 citations
2. 02*

   Absolute hydrogen depth profiling using the resonant ${}^1$H(${}^{15}$N,$\alpha \gamma$)${}^{12}$C nuclear reaction

   Tobias P. Reinhardt (TU Dresden)🇩🇪 · Shavkat Akhmadaliev (HZDR)🇸🇪 · Daniel Bemmerer (HZDR)🇩🇪 · Klaus Stöckel (HZDR and TU Dresden)🇩🇪 · Louis Wagner (HZDR and TU Dresden)🇩🇪

   Resonant nuclear reactions are a powerful tool for the determination of the amount and profile of hydrogen in thin layers of material. Usually, this tool requires the use of a standard of well-known composition. The present work, by contrast, deals with standard-less hydrogen depth profiling. This approach requires precise nuclear data, e.g. on the widely used ${}^1$H(${}^{15}$N,$\alpha \gamma$)${}^{12}$C reaction, resonant at 6.4\,MeV ${}^{15}$N beam energy. Here, the strongly anisotropic angular distribution of the emitted $\gamma$-rays from this resonance has been re-measured, resolving a previous discrepancy. Coefficients of (0.38$\pm$0.04) and (0.80$\pm$0.04) have been deduced for the second and fourth order Legendre polynomials, respectively. In addition, the resonance strength has been re-evaluated to (25.0$\pm$1.5)\,eV, 10\% higher than previously reported. A simple working formula for the hydrogen concentration is given for cases with known $\gamma$-ray detection efficiency. Finally, the absolute approach is illustrated using two examples.

   nucl-excond-mat.mtrl-sciNucl.Instrum.Meth.B(2016)·9 citations
3. 03*

   Extension of the ratio method to low energy

   F. Colomer · P. Capel🇩🇪 · F. M. Nunes🇺🇸 · R. C. Johnson

   Background: The ratio method has been proposed as a means to remove the reaction model dependence in the study of halo nuclei. Purpose: Originally, it was developed for higher energies but given the potential interest in applying the method at lower energy, in this work we explore its validity at 20 MeV/nucleon. Method: The ratio method takes the ratio of the breakup angular distribution and the summed angular distribution (which includes elastic, inelastic and breakup) and uses this observable to constrain the features of the original halo wave function. In this work we use the Continuum Discretized Coupled Channel method and the Coulomb-corrected Dynamical Eikonal Approximation for the study. Results: We study the reactions of 11Be on 12C, 40Ca and 208Pb at 20 MeV/nucleon. We compare the various theoretical descriptions and explore the dependence of our result on the core-target interaction. Conclusions: Our study demonstrates that the ratio method is valid at these lower beam energies.

   ↳ nucl-thnucl-exPRC(2016)·7 citations
4. 04*

   Production of $Y(4260)$ as a hadronic molecule state of $\bar{D}{D}_1+c.c.$ in $e^{+}{e}^{-}$ annihilations

   Wen Qin🇨🇳 · Si-Run Xue🇨🇳 · Qiang Zhao🇨🇳

   We study the $Y(4260)$ production mechanism in $e^{+}{e}^{-}$ annihilations in the framework of hadronic molecules and investigate the consequence of such a picture in different decay channels. In the hadronic molecule picture the $Y(4260)$ is described as a mixture state composed of a long-ranged $\bar{D}{D}_1(2420)+c.c.$ molecule state and a compact $c\bar{c}$ component. We show that the compositeness relation can still provide a reasonable constraint on the wavefunction renormalization parameter due to the dominance of the molecular component. Such a mechanism can be regarded as a natural consequence of the heavy quark spin symmetry (HQSS) breaking. This study elaborates the molecular picture for the $Y(4260)$ in the $e^{+}{e}^{-}$ annihilations and affirms that the cross section lineshape of $e^{+}{e}^{-}\to \bar{D}{D}^{\ast }\pi +c.c.$ in the vicinity of the $Y(4260)$ should have a nontrivial behavior. In this framework we predict that the upper limit of the $Y(4260)$ leptonic decay width is about 500 eV. We also investigate the coupling for $D_1(2420)\to D^{\ast }\pi$ in the ${}^3{P}_0$ quark model and examine the possible HQSS breaking effects due to the deviation from the ${|}^1{P}_1⟩$ and ${|}^3{P}_1⟩$ ideal mixing. This will in turn provide a constraint on the HQSS breaking coupling for the $Y(4260)$ to $\bar{D}{D}_1(2420)+c.c.$ via its $c\bar{c}$ component.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2016)·53 citations
5. 05*

   Effective field theory for large logarithms in radiative corrections to electron proton scattering

   Richard J. Hill🇺🇸

   Radiative corrections to elastic electron-proton scattering are analyzed in effective field theory. A new factorization formula identifies all sources of large logarithms in the limit of large momentum transfer, $Q^2\gg m_e^2$. Explicit matching calculations are performed through two-loop order. A renormalization analysis in soft-collinear effective theory is performed to systematically compute and resum large logarithms. Implications for the extraction of charge radii and other observables from scattering data are discussed. The formalism may be applied to other lepton-nucleon scattering and $e^{+}{e}^{-}$ annihilation processes.

   ↳ hep-phhep-exnucl-exnucl-th+1PRD(2017)·47 citations
6. 06*

   Re-evaluation of the ${}^{16}$O($n$,$\gamma$)${}^{17}$O cross section at astrophysical energies and its role as neutron poison in the $s$ process

   Peter Mohr🇭🇺 · Christian Heinz · Marco Pignatari🇭🇺 · Iris Dillmann🇨🇦 · Alberto Mengoni🇮🇹 · Franz Kaeppeler🇩🇪

   The doubly-magic nucleus ${}^{16}$O has a small neutron capture cross section of just a few tens of microbarn in the astrophysical energy region. Despite of this, ${}^{16}$O plays an important role as neutron poison in the astrophysical slow neutron capture ($s$) process due to its high abundance. We present in this paper a re-evaluation of the available experimental data for ${}^{16}$O($n,\gamma$)${}^{17}$O and derive a new recommendation for the Maxwellian-averaged cross sections (MACS) between $kT$= 5$-$100 keV. Our new recommendations are lower up to $kT$= 60 keV compared to the previously recommended values but up to 14\% higher at $kT$= 100 keV. We explore the impact of this different energy dependence on the weak $s$-process during core helium- ($kT$= 26 keV) and shell carbon burning ($kT$= 90 keV) in massive stars where ${}^{16}$O is the most abundant isotope.

   ↳ astro-ph.SRnucl-exnucl-thApJ(2016)·14 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.