Tue·Oct 22, 2019Tuesday·October 22, 2019

1. 01*

   Strong resonances at high excitation energy in 17O+alpha resonance scattering

   D. K. Nauruzbayev🇰🇿 · A. K. Nurmukhanbetova🇰🇿 · V. Z. Goldberg🇺🇸 · M. La Cognata🇮🇹 · A. Di Pietro🇮🇹 · P. Figuera🇮🇹 · S. Cherubini🇮🇹 · M. Gulino🇮🇹 · L. Lamia🇮🇹 · R. G. Pizzone🇮🇹 · R. Spart`a🇮🇹 · A. Tumino🇮🇹 · A. Serikov🇷🇺 · E. M. Gazeeva🇷🇺

   The Thick Target Inverse Kinematic (TTIK) approach was used to measure excitation functions for the elastic 17O ({\alpha}, {\alpha}) scattering at the initial 17O beam energy of 54.4 MeV. We observed strong peaks corresponding to highly excited {\alpha}-cluster states in the 21Ne excitation energy region of 8-16 MeV, which have never been investigated before. Additional tests were done at a 17O beam energy of 56.4 MeV to estimate a possible contribution of resonance inelastic scattering.

   nucl-exPhys.Atom.Nucl.(2020)·0 citations
2. 02*

   Measurement of electrons from semileptonic heavy-flavour hadron decays at midrapidity in pp and Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV

   ALICE Collaboration

   The differential invariant yield as a function of transverse momentum ($p_{\mathrm{T}}$) of electrons from semileptonic heavy-flavour hadron decays was measured at midrapidity in central (0-10%), semi-central (30-50%) and peripheral (60-80%) lead-lead (Pb-Pb) collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\text{ TeV}$ in the $p_{\mathrm{T}}$ intervals 0.5-26 GeV/$c$ (0-10% and 30-50%) and 0.5-10 GeV/$c$ (60-80%). The production cross section in proton-proton (pp) collisions at $\sqrt{s}=5.02$ TeV was measured as well in $0.5<p_{\mathrm{T}}<10$ GeV/$c$ and it lies close to the upper band of perturbative QCD calculation uncertainties up to $p_{\mathrm{T}}=5$ GeV/$c$ and close to the mean value for larger $p_{\mathrm{T}}$. The modification of the electron yield with respect to what is expected for an incoherent superposition of nucleon-nucleon collisions is evaluated by measuring the nuclear modification factor $R_{\mathrm{AA}}$. The measurement of the $R_{\mathrm{AA}}$ in different centrality classes allows in-medium energy loss of charm and beauty quarks to be investigated. The $R_{\mathrm{AA}}$ shows a suppression with respect to unity at intermediate $p_{\mathrm{T}}$, which increases while moving towards more central collisions. Moreover, the measured $R_{\mathrm{AA}}$ is sensitive to the modification of the parton distribution functions (PDF) in nuclei, like nuclear shadowing, which causes a suppression of the heavy-quark production at low $p_{\mathrm{T}}$ in heavy-ion collisions at LHC.

   nucl-exhep-exPLB(2020)·82 citations
3. 03*

   Measurement of the ${}^{70}$Ge($n,\gamma$) cross section up to 300~keV at the CERN n_TOF facility

   A. Gawlik · C. Lederer-Woods · the n_TOF collaboration

   Neutron capture data on intermediate mass nuclei are of key importance to nucleosynthesis in the weak component of the slow neutron capture processes, which occurs in massive stars. The ($n,\gamma$) cross section on ${}^{70}$Ge, which is mainly produced in the $s$~process, was measured at the neutron time-of-flight facility n_TOF at CERN. Resonance capture kernels were determined up to 40~keV neutron energy, and average cross sections up to 300~keV. Stellar cross sections were calculated from $kT=5$~keV to $kT=100$ keV and are in very good agreement with a previous measurement by Walter and Beer (1985), and recent evaluations. Average cross sections are in agreement with Walter and Beer (1985) over most of the neutron energy range covered, while being systematically smaller for neutron energies above 150~keV. We have calculated isotopic abundances produced in $s$-process environments in a 25 solar mass star for two initial metallicities (below solar, and close to solar). While the low metallicity model reproduces best the solar system germanium isotopic abundances the close to solar model shows a good global match to solar system abundances between mass numbers A=60-80.

   nucl-exPRC(2019)·17 citations
4. 04*

   Mixed higher-order anisotropic flow and nonlinear response coefficients of charged particles in PbPb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 2.76 and 5.02 TeV

   CMS Collaboration

   Anisotropies in the initial energy density distribution of the quark-gluon plasma created in high energy heavy ion collisions lead to anisotropies in the azimuthal distributions of the final-state particles known as collective flow. Fourier harmonic decomposition is used to quantify these anisotropies. The higher-order harmonics can be induced by the same order anisotropies (linear response) or by the combined influence of several lower order anisotropies (nonlinear response) in the initial state. The mixed higher-order anisotropic flow and nonlinear response coefficients of charged particles are measured as functions of transverse momentum and centrality in PbPb collisions at nucleon-nucleon center-of-mass energies $\sqrt{s_{\mathrm{NN}}}=$ 2.76 and 5.02 TeV with the CMS detector. The results are compared with viscous hydrodynamic calculations using several different initial conditions, as well as microscopic transport model calculations. None of the models provides a simultaneous description of the mixed higher-order flow harmonics and nonlinear response coefficients.

   ↳ hep-exnucl-exEPJC(2020)·36 citations
5. 05*

   Effects of Pauli blocking on pion production in central collisions of neutron-rich nuclei

   Natsumi Ikeno🇯🇵 · Akira Ono🇯🇵 · Yasushi Nara🇯🇵 · Akira Ohnishi🇯🇵

   Pauli blocking is carefully investigated for the processes of $NN\to N\Delta$ and $\Delta \to N\pi$ in heavy-ion collisions, aiming at a more precise prediction of the ${\pi }^{-}/{\pi }^{+}$ ratio which is an important observable to constrain the high-density symmetry energy. We use the AMD+JAM approach, which combines the antisymmetrized molecular dynamics for the time evolution of nucleons and the JAM model to treat processes for $\Delta$ resonances and pions. As is known in general transport-code simulations, it is difficult to treat Pauli blocking very precisely due to unphysical fluctuations and additional smearing of the phase-space distribution function, when Pauli blocking is treated in the standard method of JAM. We propose an improved method in AMD+JAM to use the Wigner function precisely calculated in AMD as the blocking probability. Different Pauli blocking methods are compared in heavy-ion collisions of neutron-rich nuclei, ${}^{132}\mathrm{Sn}+{}^{124}\mathrm{Sn}$, at 270 MeV/nucleon. With the more accurate method, we find that Pauli blocking is stronger, in particular for the neutron in the final state in $NN\to N\Delta$ and $\Delta \to N\pi$, compared to the case with a proton in the final state. Consequently, the ${\pi }^{-}/{\pi }^{+}$ ratio becomes higher when the Pauli blocking is improved, the effect of which is found to be comparable to the sensitivity to the high-density symmetry energy.

   ↳ nucl-thnucl-exPRC(2020)·13 citations
6. 06*

   Feasibility study of the $K^{+}d\to K^{0}pp$ reaction for the "${\Theta }^{+}$" pentaquark

   Takayasu Sekihara🇯🇵 · Hyun-Chul Kim🇰🇷 · Atsushi Hosaka🇯🇵

   We investigate theoretically the $K^{0}p$ invariant mass spectrum of the $K^{+}d\to K^{0}pp$ reaction and scrutinize how the signal of the "${\Theta }^{+}$" pentaquark, if it exists, emerges in the $K^{0}p$ spectrum. The most prominent advantage of this reaction is that we can clearly judge whether the "${\Theta }^{+}$" exists or not as a direct-formation production without significant backgrounds, in contrast to other reactions such as photoproduction and $\pi$-induced productions. We show that while the impulse or single-step scattering process can cover the "${\Theta }^{+}$" energy region with an initial kaon momentum $k_{\mathrm{lab}}\approx 0.40\mathrm{GeV}/c$ in the laboratory frame, the contributions from double-step processes may have a potential possibility to reach the "${\Theta }^{+}$" energy region with a higher kaon momentum $k_{\mathrm{lab}}\sim 1\mathrm{GeV}/c$. Assuming that the full decay width of the "${\Theta }^{+}$" is around $0.5\mathrm{MeV}$, we predict that the magnitude of the peak corresponding to the "${\Theta }^{+}$" is around a few hundred $\mu \mathrm{b}$ to $1\mathrm{mb}$ with the momentum of the kaon beam $k_{\mathrm{lab}}\approx 0.40\mathrm{GeV}/c$ while it is around $\lesssim 1\mu \mathrm{b}$ with $k_{\mathrm{lab}}\approx 0.85\mathrm{GeV}/c$. Thus, the "${\Theta }^{+}$" peak is more likely to be seen at $k_{\mathrm{lab}}\approx 0.40\mathrm{GeV}/c$ than at $k_{\mathrm{lab}}\approx 0.85\mathrm{GeV}/c$.

   ↳ hep-phhep-exnucl-exnucl-thPTEP(2020)·8 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.