Tue·May 7, 2019Tuesday·May 7, 2019

1. 01*

   ${}^{21}$Ne level structure in the resonance ${}^{17}$O+$\alpha$ elastic scattering

   A. K. Nurmukhanbetova🇰🇿 · V. Z. Goldberg🇺🇸 · D. K. Nauruzbayev🇰🇿 · M. S. Golovkov · A. Volya🇺🇸

   The first study of resonances in ${}^{17}$O+$\alpha$ elastic scattering was carried out using the Thick Target Inverse Kinematics (TTIK) method. The data were analyzed in the framework of an $\text{R}$-matrix approach. Many $\alpha$-cluster states were found in the ${}^{21}$Ne excitation region of the 9-13 MeV excitation energy including the first observation of a broad $\text{l}$=0 state in an odd-even nucleus, which is likely the analog of the broad 0${}^{+}$ at 8 MeV in ${}^{20}$Ne. The observed structure in ${}^{21}$Ne appeared to be strikingly similar to that in ${}^{20}$Ne populated in the resonance ${}^{16}$O+$\alpha$ scattering. The results are also useful for refinement of data on an ${}^{17}$O($\alpha$,$\text{n}$) reaction important for astrophysics.

   nucl-exnucl-thPRC(2019)·10 citations
2. 02*

   Cross section of ${}^3$He($\alpha$,$\gamma$)${}^7$Be around the ${}^7$Be proton separation threshold

   T. Szücs🇩🇪 · G. G. Kiss🇯🇵 · Gy. Gyürky🇭🇺 · Z. Halász🇭🇺 · T. N. Szegedi🇭🇺 · Zs. Fülöp🇭🇺

   The ${}^3$He($\alpha$,$\gamma$)${}^7$Be reaction is a widely studied nuclear reaction; however, it is still not understood with the required precision. It has a great importance both in Big Bang nucleosynthesis and in solar hydrogen burning. The low mass number of the reaction partners makes it also suitable for testing microscopic calculations. Despite the high number of experimental studies, none of them addresses the ${}^3$He($\alpha$,$\gamma$)${}^7$Be reaction cross sections above 3.1-MeV center-of-mass energy. Recently, a previously unobserved resonance in the ${}^6$Li(p,$\gamma$)${}^7$Be reaction suggested a new level in ${}^7$Be, which would also have an impact on the ${}^3$He($\alpha$,$\gamma$)${}^7$Be reaction in the energy range above 4.0 MeV. The aim of the present experiment is to measure the ${}^3$He($\alpha$,$\gamma$)${}^7$Be reaction cross section in the energy range of the proposed level. For this investigation the activation technique was used. A thin window gas-cell target confining ${}^3$He gas was irradiated using an $\alpha$ beam. The ${}^7$Be produced was implanted into the exit foil. The ${}^7$Be activity was determined by counting the $\gamma$ rays following its decay by a well-shielded high-purity germanium detector. Reaction cross sections have been determined between $E_{cm}=4.0-4.4$ MeV with 0.04-MeV steps covering the energy range of the proposed nuclear level. One lower-energy cross-section point was also determined to be able to compare the results with previous studies. A constant cross section of around 10.5 $\mu$barn was observed around the ${}^7$Be proton separation energy. An upper limit of 45 neV for the strength of a ${}^3$He($\alpha$,$\gamma$)${}^7$Be resonance is derived.

   nucl-exPRC(2019)·25 citations
3. 03*

   First measurement of the temperature dependence of muon transfer rate from muonic hydrogen atoms to oxygen

   FAMU Collaboration: E. Mocchiutti (1)🇮🇹 · A. Adamczak (2)🇵🇱 · D. Bakalov (3)🇧🇬 · G. Baldazzi (4)🇮🇹 · R. Benocci (5,6)🇮🇹 · R. Bertoni (5)🇮🇹 · M. Bonesini (5,7)🇮🇹 · V. Bonvicini (1)🇮🇹 · H. Cabrera Morales (1)🇮🇹 · F. Chignoli (5)🇮🇹 · M. Clemenza (5,7)🇮🇹 · L. Colace (8,9)🇮🇹 and 29 other authors

   We report the first measurement of the temperature dependence of muon transfer rate from $\mu$p atoms to oxygen between 100 and 300 K. Data were obtained from the X-ray spectra of delayed events in gaseous target H${}_2$/O${}_2$ exposed to a muon beam. Based on the data, we determined the muon transfer energy dependence up to 0.1 eV, showing an 8-fold increase in contrast with the predictions of constant rate in the low energy limit. This work set constraints on theoretical models of muon transfer, and is of fundamental importance for the measurement of the hyperfine splitting of $\mu$p by the FAMU collaboration.

   nucl-exphysics.ins-detPLA(2020)·12 citations
4. 04*

   First observation of the directed flow of $D^0$ and $\overline{D^0}$ in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200~GeV

   STAR Collaboration: J. Adam🇺🇸 · L. Adamczyk🇵🇱 · J. R. Adams🇺🇸 · J. K. Adkins🇺🇸 · G. Agakishiev🇷🇺 · M. M. Aggarwal🇮🇳 · Z. Ahammed🇮🇳 · I. Alekseev🇷🇺 · D. M. Anderson🇺🇸 · R. Aoyama🇯🇵 · A. Aparin🇷🇺 · D. Arkhipkin🇺🇸 and 339 other authors

   We report the first measurement of rapidity-odd directed flow ($v_1$) for $D^0$ and $\overline{D^0}$ mesons at mid-rapidity ($|y|<0.8$) in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200\,GeV using the STAR detector at the Relativistic Heavy Ion Collider. In 10--80\% Au+Au collisions, the slope of the $v_1$ rapidity dependence ($d{v}_1/dy$), averaged over $D^0$ and $\overline{D^0}$ mesons, is -0.080 $\pm$ 0.017 (stat.) $\pm$ 0.016 (syst.) for transverse momentum $p_{\mathrm{T}}$ above 1.5~GeV/$c$. The absolute value of $D^0$-meson $d{v}_1/dy$ is about 25 times larger than that for charged kaons, with 3.4$\sigma$ significance. These data give a unique insight into the initial tilt of the produced matter, and offer constraints on the geometric and transport parameters of the hot QCD medium created in relativistic heavy-ion collisions.

   nucl-exhep-exnucl-thPRL(2019)·141 citations
5. 05*

   An efficient method for mapping the 12C+12C molecular resonances at low energies

   Xiaodong Tang🇨🇳 · Shaobo Ma🇨🇳 · Xiao Fang🇺🇸 · Brian Bucher🇺🇸 · Adam Alongi · Craig Cahillane · Wanpeng Tan🇺🇸

   The 12C+12C fusion reaction is famous for its complication of molecular resonances, and plays an important role in both nuclear structure and astrophysics. It is extremely difficult to measure the cross sections of 12C+12C fusions at energies of astrophysical relevance due to very low reaction yields. To measure the complicated resonant structure existing in this important reaction, an efficient thick target method has been developed and applied for the first time at energies Ec.m.<5.3 MeV. A scan of the cross sections over a relatively wide range of energies can be carried out using only a single beam energy. The result of measurement at Ec.m.= 4.1 MeV is compared with other results from previous work. This method would be useful for searching potentially existing resonances of 12C+12C in the energy range 1 MeV<Ec.m.<3 MeV.

   nucl-exastro-ph.SRNucl.Sci.Tech.(2019)·17 citations
6. 06*

   Comment on "Searching for flavor dependence in nuclear quark behavior"

   O. Hen🇺🇸 · F. Hauenstein🇺🇸 · D.W. Higinbotham🇺🇸 · G.A. Miller🇺🇸 · E. Piasetzky🇮🇱 · A. Schmidt🇺🇸 · E.P. Segarra🇺🇸 · M. Strikman🇺🇸 · L.B. Weinstein🇺🇸

   Weinstein, et. al [1] [PRL 106, 052301 (2011)] and Hen, et. al [2] [PRC 85, 047301 (2012)] observed a correlation between the EMC effect and the amount of short range correlated (SRC) pairs in nuclei which implies that quark distributions are different in SRC pairs as compared with free nucleons. Schmookler, et. al [3] [Nature 566, 354 (2019)] bolstered this by showing that the EMC data can be explained by a universal modification of the structure of nucleons in neutron-proton SRC pairs and presented the first data-driven extraction of this universal modification function (UMF). Arrington and Fomin [4] [arxiv 1903.12535] attempt to gain insight into the correlation between the EMC effect and SRCs by distinguishing between correlated nucleon pairs at high-virtuality (HV) vs. high local-density (LD). However, there is an inconsistency in their derivations of the UMFs, FLD univ and FHV , causing a non-physical difference between them for asymmetric nuclei. In addition, the univ combinatorial scaling they used to extract high-LD np, pp and nn pairs from measured HV np pairs is contradicted by realistic ab-initio Quantum Monte-Carlo (QMC) calculations.

   nucl-exnucl-th7 citations
7. 07*

   Resummation of Boson-Jet Correlation at Hadron Colliders

   Yang-Ting Chien🇺🇸 · Ding Yu Shao🇨🇭 · Bin Wu🇨🇭

   We perform a precise calculation of the transverse momentum (${\vec{q}}_T$) distribution of the boson+jet system in boson production events. The boson can be either a photon, $W$, $Z$ or Higgs boson with mass $m_V$, and ${\vec{q}}_T$ is the sum of the transverse momenta of the boson and the leading jet with magnitude $q_T=|{\vec{q}}_T|$. Using renormalization group techniques and soft-collinear effective theory, we resum logarithms $\log (Q/q_T)$ and $\log R$ at next-to-leading logarithmic accuracy including the non-global logarithms, where $Q$ and $R$ are respectively the hard scattering energy and the radius of the jet. Specifically, we investigate two scenarios of $p_T^J\lesssim m_V$ or $p_T^J\gtrsim m_V$ in $Z$+jet events, and we examine the $q_T$ distributions with different jet radii and study the effect of non-global logarithms. In the end we compare our theoretical calculations with Monte Carlo simulations and data from the LHC.

   ↳ hep-phhep-exnucl-exJHEP(2019)·59 citations
8. 08*

   The Giant Pairing Vibration in Heavy Nuclei: Present Status and Future Studies

   M. Assié🇫🇷 · C. H. Dasso🇪🇸 · R. J. Liotta🇸🇪 · A.O. Macchiavelli🇺🇸 · A. Vitturi🇮🇹

   The Giant Pairing Vibration, a two-nucleon collective mode originating from the second shell above the Fermi surface, has long been predicted and expected to be strongly populated in two-nucleon transfer reactions with cross sections similar to those of the normal Pairing Vibration. Recent experiments have provided evidence for this mode in ${}^{14,15}$C but, despite sensitive studies, it has not been definitively identified either in Sn or Pb nuclei where pairing correlations are known to play a crucial role near their ground states. In this paper we review the basic theoretical concepts of this "elusive" state and the status of experimental searches in heavy nuclei. We discuss the hindrance effects due to Q-value mismatch and the use of weakly-bound projectiles as a way to overcome the limitations of the (p,t) and (t,p) reactions. We also discuss the role of the continuum and conclude with some possible future developments.

   ↳ nucl-thnucl-ex1 citation
9. 09*

   Constraints on the Dark Matter Interpretation $n\to \chi +e^{+}{e}^{-}$ of the Neutron Decay Anomaly with the PERKEO II experiment

   M. Klopf🇦🇹 · E. Jericha🇦🇹 · B. Märkisch🇩🇪 · H. Saul🇩🇪 · T. Soldner🇫🇷 · H. Abele🇦🇹

   Discrepancies from in-beam and in-bottle type experiments measuring the neutron lifetime are on the 4$\sigma$ standard deviation level. In a recent publication Fornal and Grinstein proposed that the puzzle could be solved if the neutron would decay on the one percent level via a dark decay mode, one possible branch being $n\to \chi +e^{+}{e}^{-}$. With data from the \perkeoII experiment we set limits on the branching fraction and exclude a one percent contribution for $95\%$ of the allowed mass range for the dark matter particle.

   ↳ hep-exhep-phnucl-exPRL(2019)·35 citations
10. 10*

    Operator Relations for Gravitational Form Factors

    Kazuhiro Tanaka (Juntendo Univ.)🇯🇵

    The form factors for the hadron matrix element of the QCD energy-momentum tensor not only describe the coupling of the hadron with a graviton as the ``gravitational form factors'', but also serve as unique quantities for describing the shape inside the hadron reflecting dynamics of quarks and gluons, such as the internal shear forces acting on the quarks/gluons and their pressure distributions. We consider the gravitational form factors for a hadron, in particular, for a (pseudo)scalar hadron and for the nucleon. We derive and clarify the relations satisfied by the gravitational form factors as direct consequences of the symmetries and the equations of motion in QCD, and connections to the generalized parton distributions. Our results reveal that the gravitational form factors are related to the higher-twist quark-gluon correlation effects inside the hadrons and also to QCD trace anomaly.

    ↳ hep-phhep-exnucl-exnucl-thJPS Conf.Proc.(2019)·1 citation
11. 11*

    First principles electromagnetic responses in medium-mass nuclei

    Johannes Simonis🇩🇪 · Sonia Bacca🇩🇪 · Gaute Hagen🇺🇸

    We review the recent progress made in the computation of electromagnetic response functions in light and medium-mass nuclei using coupled-cluster theory. We show how a many-body formulation of the Lorentz integral transform method allows to calculate the photoabsorption cross sections of ${}^{16,22}$O and ${}^{40}$Ca. Then, we discuss electromagnetic sum rules, with particular emphasis on the electric dipole polarizability, ${\alpha }_D$. By including triples corrections in coupled-cluster theory, we revisit ${}^{48}$Ca, for which, beside the electric dipole polarizability, we had previously investigated the neutron and proton radii, as well as the size of the neutron-skin thickness [1]. We show that correlations among these observables still hold, albeit a better agreement with experiment is obtained for ${\alpha }_D$ and the prediction of a small neutron-skin thickness is further corroborated.

    ↳ nucl-thnucl-exEPJA(2019)·33 citations
12. 12*

    Gross, intermediate and fine structure of nuclear giant resonances: Evidence for doorway states

    Peter von Neumann-Cosel (1)🇩🇪 · Vladimir Yu. Ponomarev (1)🇩🇪 · Achim Richter (1)🇩🇪 · Jochen Wambach (1,2) ((1) Institut für Kernphysik, Technische Universität Darmstadt, Germany, (2) European Centre for Theoretical Studies in Nuclear Physics and related Areas (ECT*) and Fondazione Bruno Kessler, Villazzano, Italy)🇮🇹

    We review the phenomenon of fine structure of nuclear giant resonances and its relation to different resonance decay mechanisms. Wavelet analysis of the experimental spectra provides quantitative information on the fine structure in terms of characteristic scales. A comparable analysis of resonance strength distributions from microscopic approaches incorporating one or several of the resonance decay mechanisms allows conclusions on the source of the fine structure. For the isoscalar giant quadrupole resonance (ISGQR), spreading through the first step of the doorway mechanism, i.e.\ coupling between one particle-one hole ($1p1h$) and two particle-two hole ($2p2h$) states is identified as the relevant mechanism. In heavy nuclei it is dominated by coupling to low-lying surface vibrations, while in lighter nuclei stochastic coupling becomes increasingly important. The fine structure observed for the isovector giant dipole resonance (IVGDR) arises mainly from the fragmentation of the $1p1h$ strength (Landau damping), although some indications for the relevance of the spreading width are also found.

    ↳ nucl-thnucl-exEPJA(2019)·16 citations
13. 13*

    Calculated Inter-band B(E2)'s in the p-f Shell

    Levering Wolfe🇺🇸 · Larry Zamick🇺🇸

    Whereas previous works for B(E2)'s in the even-even Ti isotopes focused on yrast transitions we here also consider inter-band transitions to a second group i.e. states like 1_{1} , 2_{2}, 3_{1} , 4_{2} , 5_{1}e.t.c.. We focus on variations from one even-even Ti isotope to the next. We make a qualitative comparison with similar transitions in a heavier deformed nucleus.

    ↳ nucl-thnucl-exNPA(2019)·1 citation

* 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.