Fri·Jan 24, 2020Friday·January 24, 2020

1. 01*

   Constraining the ${}^{22}$Ne($\alpha$,$\gamma$)${}^{26}$Mg and ${}^{22}$Ne($\alpha$,n)${}^{25}$Mg reaction rates using sub-Coulomb $\alpha$-transfer reactions

   H. Jayatissa🇺🇸 · G.V. Rogachev🇺🇸 · V.Z. Goldberg🇺🇸 · E. Koshchiy🇺🇸 · G. Christian🇨🇦 · J. Hooker🇺🇸 · S. Ota🇯🇵 · B.T. Roeder🇺🇸 · A. Saastamoinen🇺🇸 · O. Trippella · S. Upadhyayula🇺🇸 · E. Uberseder🇺🇸

   The ${}^{22}$Ne($\alpha$,$\gamma$)${}^{26}$Mg and ${}^{22}$Ne($\alpha$,n)${}^{25}$Mg reactions play an important role in astrophysics because they have significant influence on the neutron flux during the weak branch of the s-process. We constrain the astrophysical rates for these reactions by measuring partial $\alpha$-widths of resonances in ${}^{26}$Mg located in the Gamow window for the ${}^{22}$Ne+$\alpha$ capture. These resonances were populated using ${}^{22}$Ne(${}^6$Li,d)${}^{26}$Mg and ${}^{22}$Ne(${}^7$Li,t)${}^{26}$Mg reactions at energies near the Coulomb barrier. At these low energies $\alpha$-transfer reactions favor population of low spin states and the extracted partial $\alpha$-widths for the observed resonances exhibit only minor dependence on the model parameters. The astrophysical rates for both the ${}^{22}$Ne($\alpha$,$\gamma$)${}^{26}$Mg and the ${}^{22}$Ne($\alpha$,n)${}^{25}$Mg reactions are shown to be significantly different than the previously suggested values.

   nucl-exastro-ph.SRnucl-thPLB(2020)·28 citations
2. 02*

   Deuteron-induced reactions on manganese at low energies

   M. Avrigeanu🇷🇴 · E. Simeckova🇨🇿 · U. Fischer · J. Mrazek🇨🇿 · J. Novak🇫🇷 · M. Stefanik · C. Costache🇷🇴 · V. Avrigeanu

   The scarce data systematics and complexity of deuteron interactions demand the update of both the experimental database and theoretical frame of deuteron activation cross sections. Various reactions induced by neutrons and protons following the deuteron breakup (BU) should be also taken into account. On the other hand, deuteron reaction cross sections recommended recently for high-priority elements are still based on data fit without predictive power. Purpose: Accurate new measurements of low-energy deuteron-induced reaction cross sections for monoisotopic (55Mn) natural manganese target enhance the related database as well as the opportunity of an unitary and consistent account of the related reaction mechanisms. Method: Activation cross sections of 54,56Mn, and 51Cr nuclei by deuterons on ${}^{55}$Mn were measured at energies <20 MeV by the stacked-foil technique and high resolution gamma spectrometry at the U-120M cyclotron of CANAM, NPI CAS. Then all available data for deuterons on 55Mn up to 50 MeV are analyzed paying particular attention to BU and direct reaction (DR) mechanisms. Results: Newly measured activation cross sections strengthen the deuteron database at low energies, at once with a consistent account for the first time of all available data. Conclusions: Due account of deuteron-induced reactions on 55Mn, including particularly the new experimental data at low energies, is provided by a suitable BU and DR assessment.

   nucl-exnucl-thPRC(2020)·7 citations
3. 03*

   Bulk medium evolution has considerable effects on jet observables

   Yasuki Tachibana🇺🇸 · Chun Shen🇺🇸 · Abhijit Majumder🇺🇸

   We consider the case, in QCD, of a single jet propagating within a strongly interacting fluid, of finite extent. Interactions lead to the appearance of a source of energy-momentum within the fluid. The remnant jet that escapes the container is analyzed along with portions of the medium excited by the jet. We study the effect of a static versus a semi-realistic expanding medium, with jets traveling inward versus outward. We consider the medium response via recoils in partonic scatterings based on a weakly-coupled description and its combination with hydrodynamical medium response based on a strongly-coupled description, followed by incorporation into a jet. The effects of these limits on the reconstructed energy, momentum and mass of the jet, as a function of the angle away from the original parton direction are studied. It is demonstrated that different flow velocity configurations in the medium produce considerable differences in jet observables. This work highlights the importance of accurate dynamical modeling of the soft medium as a foundation on which to calculate jet modification, and casts skepticism on results obtained without such modeling.

   ↳ nucl-thhep-phnucl-exPRC(2022)·44 citations
4. 04*

   Skewness, kurtosis and the 5th and 6th order cumulants of net baryon-number distributions from lattice QCD confront high-statistics STAR data

   A. Bazavov🇺🇸 · D. Bollweg🇩🇪 · H.-T. Ding🇨🇳 · P. Enns🇩🇪 · J. Goswami🇩🇪 · P. Hegde🇮🇳 · O. Kaczmarek🇩🇪 · F. Karsch🇩🇪 · R. Larsen🇺🇸 · Swagato Mukherjee🇺🇸 · H. Ohno🇯🇵 · P. Petreczky🇺🇸 and 3 other authors

   We present new results on up to $6^{th}$ order cumulants of net baryon-number fluctuations at small values of the baryon chemical potential, ${\mu }_B$, obtained in lattice QCD calculations with physical values of light and strange quark masses. Representation of the Taylor expansions of higher order cumulants in terms of the ratio of the two lowest order cumulants, $M_B/{\sigma }_B^2={\chi }_1^B(T,{\mu }_B)/{\chi }_2^B(T,{\mu }_B)$, allows for a parameter free comparison with data on net proton-number cumulants obtained by the STAR Collaboration in the Beam Energy Scan at RHIC. We show that recent high statistics data on skewness and kurtosis ratios of net proton-number distributions, obtained at beam energy $\sqrt{s_{{}_{NN}}}=54.4$ GeV, agree well with lattice QCD results on cumulants of net baryon-number fluctuations close to the pseudo-critical temperature, $T_{pc}({\mu }_B)$, for the chiral transition in QCD. We also present first results from a next-to-leading order expansion of $5^{th}$ and $6^{th}$ order cumulants on the line of pseudo-critical temperatures.

   ↳ hep-lathep-phnucl-exnucl-thPRD(2020)·215 citations
5. 05*

   Centrality fluctuations and decorrelations in heavy-ion collisions

   Jiangyong Jia🇺🇸 · Chunjian Zhang🇺🇸 · Jun Xu🇨🇳

   The centrality or the number of initial-state sources $V$ of the system produced in heavy ion collision is a concept that is not uniquely defined and subject to significant theoretical and experimental uncertainties. We argue that a more robust connection between the initial-state sources with final-state multiplicity could be established from the event-by-event multiplicity correlation between two subevents separated in pseudorapidity, $N_a$ vs $N_b$. This correlation is sensitive to two main types of centrality fluctuations (CF): 1) particle production for each source $p(n)$ which smears the relation between $V$ and $N_a$ used for experimental centrality, and 2) decorrelations between the sources in the two subevents $V_b$ and $V_a$. The CF is analyzed in terms of cumulants of $V_b$ and $N_b$ as a function of $N_a$, i.e. experimental centrality is defined with $N_a$. We found that the mean values $⟨V_b{⟩}_{N_a}$ and $⟨N_b{⟩}_{N_a}$ increase linearly with $N_a$ in mid-central collisions, but flatten out in ultra-central collisions. Such non-linear behavior is sensitive to the centrality resolution of $N_a$. In the presence of centrality decorrelations, the scaled variances $⟨(\delta V_b{)}^2⟩/⟨V_b⟩$ and $⟨(\delta N_b{)}^2⟩/⟨N_b⟩$ are found to decrease linearly with $N_a$ in mid-central collisions, while the $p(n)$ leads to another sharp decrease in the ultra-central region. The higher-order cumulants of $V_b$ and $N_b$ show interesting but rather complex behaviors which deserve further studies. Our results suggest that one can use the cumulants of the two-dimensional multiplicity correlation, especially the mean and variance, to constrain the particle production mechanism as well as the longitudinal fluctuations of the initial-state sources.

   ↳ nucl-thhep-phnucl-exPRResearch(2020)·17 citations
6. 06*

   Mass Yields of Fission Fragment of Pt to Ra Isotopes

   Krzysztof Pomorski🇵🇱 · Artur Dobrowolski🇵🇱 · Rui Han🇨🇳 · Bozena Nerlo-Pomorska🇵🇱 · Michal Warda🇵🇱 · Zhigang Xiao🇨🇳 · Yongjing Chen🇨🇳 · Lilie Liu · Jun-Long Tian🇨🇳

   An effective Fourier nuclear shape parametrization which describes well the most relevant degrees of freedom on the way to fission is used to construct a 3D collective model. The potential energy surface is evaluated within the macroscopic-microscopic approach based on the Lublin-Strasbourg Drop (LSD) macroscopic energy and Yukawa-folded single particle potential. A phenomenological inertia parameter is used to describe the kinetic properties of the fissioning system. The fission fragment mass yields are obtained by using an approximate solution of the underlying Hamiltonian. The predicted mass fragmentations for even-even Pt to Ra isotopes are compared with available experimental data. Their main characteristics are well reproduced when the neck rupture probability dependent on the neck radius is introduced.

   ↳ nucl-thnucl-exPRC(2020)·18 citations
7. 07*

   A new possibility for light-quark Dark Matter

   M. Bashkanov🇬🇧 · D. P. Watts🇬🇧

   Despite many decades of study the physical origin of "dark matter" in the Universe remains elusive. In this letter we calculate the properties of a completely new dark matter candidate - Bose-Einstein condensates formed from a recently discovered bosonic particle in the light-quark sector, the ${\mathbf{d}}^{\ast }(2380)$ hexaquark. In this first study, we show stable ${\mathbf{d}}^{\ast }(2380)$ Bose-Einstein condensates could form in the primordial early universe, with a production rate sufficiently large that they are a plausible new candidate for dark matter. Some possible astronomical signatures of such dark matter are also presented.

   ↳ astro-ph.COnucl-exJ.Phys.G(2020)·11 citations
8. 08*

   A new approach to monitor 13C-targets degradation in situ for 13C(alpha,n)16O cross-section measurements at LUNA

   G.F. Ciani🇮🇹 · L. Csedreki🇮🇹 · J. Balibrea-Correa🇪🇸 · A. Best🇮🇹 · M. Aliotta · F. Barile🇮🇹 · D. Bemmerer🇩🇪 · A. Boeltzig🇮🇹 · C. Broggini🇮🇹 · C.G. Bruno🇬🇧 · A. Caciolli🇮🇹 · F. Cavanna🇮🇹 and 37 other authors

   Direct measurements of reaction cross-sections at astrophysical energies often require the use of solid targets able to withstand high ion beam currents for extended periods of time. Thus, monitoring target thickness, isotopic composition, and target stoichiometry during data taking is critical to account for possible target modifications and to reduce uncertainties in the final cross-section results. A common technique used for these purposes is the Nuclear Resonant Reaction Analysis (NRRA), which however requires that a narrow resonance be available inside the dynamic range of the accelerator used. In cases when this is not possible, as for example the 13C(alpha,n)16O reaction recently studied at low energies at the Laboratory for Underground Nuclear Astrophysics (LUNA) in Italy, alternative approaches must be found. Here, we present a new application of the shape analysis of primary gamma rays emitted by the 13C(p,g)14N radiative capture reaction. This approach was used to monitor 13C target degradation {\em in situ} during the 13C(alpha,n)16O data taking campaign. The results obtained are in agreement with evaluations subsequently performed at Atomki (Hungary) using the NRRA method. A preliminary application for the extraction of the 13C(alpha,n)16O reaction cross-section at one beam energy is also reported.

   ↳ physics.ins-detnucl-exEPJA(2020)·24 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.