Mon·Feb 20, 2017Monday·February 20, 2017

1. 01*

   Study of the proton-proton collisions at 1683 MeV/c

   K.N. Ermakov🇷🇺 · V.A. Nikonov🇷🇺 · O.V. Rogachevsky🇷🇺 · A.V. Sarantsev🇷🇺 · V.V. Sarantsev🇷🇺 · S.G. Sherman🇷🇺

   The new data on the elastic $pp$ and single pion production reaction $pp\to pn{\pi }^{+}$ taken at the incident proton momentum 1683 MeV/c are presented. The data on the $pp\to pn{\pi }^{+}$ reaction are compared with predictions from the OPE model. To extract contributions of the leading partial waves the single pion production data are analyzed in the framework of the event-by-event maximum likelihood method together with the data measured earlier. The analysis allows us to obtain the assessment with a better precision the contributions from different initial partial waves.

   nucl-exnucl-thEPJA(2017)·4 citations
2. 02*

   Ab initio calculations of the isotopic dependence of nuclear clustering

   Serdar Elhatisari🇩🇪 · Evgeny Epelbaum🇩🇪 · Hermann Krebs🇩🇪 · Timo A. Lähde🇩🇪 · Dean Lee🇺🇸 · Ning Li🇩🇪 · Bing-nan Lu🇩🇪 · Ulf-G. Meißner🇩🇪 · Gautam Rupak🇺🇸

   Nuclear clustering describes the appearance of structures resembling smaller nuclei such as alpha particles (4He nuclei) within the interior of a larger nucleus. While clustering is important for several well-known examples, much remains to be discovered about the general nature of clustering in nuclei. In this letter we present lattice Monte Carlo calculations based on chiral effective field theory for the ground states of helium, beryllium, carbon, and oxygen isotopes. By computing model-independent measures that probe three- and four-nucleon correlations at short distances, we determine the shape of the alpha clusters and the entanglement of nucleons comprising each alpha cluster with the outside medium. We also introduce a new computational approach called the pinhole algorithm, which solves a long-standing deficiency of auxiliary-field Monte Carlo simulations in computing density correlations relative to the center of mass. We use the pinhole algorithm to determine the proton and neutron density distributions and the geometry of cluster correlations in 12C, 14C, and 16C. The structural similarities among the carbon isotopes suggest that 14C and 16C have excitations analogous to the well-known Hoyle state resonance in 12C.

   ↳ nucl-thastro-ph.SRhep-latnucl-exPRL(2017)·106 citations
3. 03*

   Tensor-polarized structure function $b_1$ in the standard convolution description of the deuteron

   W. Cosyn🇧🇪 · Yu-Bing Dong🇨🇳 · S. Kumano🇯🇵 · M. Sargsian🇺🇸

   Tensor-polarized structure functions of a spin-1 hadron are additional observables which do not exist for the spin-1/2 nucleon. They could probe novel aspects of the internal hadron structure. Twist-2 tensor-polarized structure functions are $b_1$ and $b_2$, and they are related by the Callan-Gross-like relation in the Bjorken scaling limit. In this work, we theoretically calculate $b_1$ in the standard convolution description for the deuteron. Two different theoretical models, a basic convolution description and a virtual nucleon approximation, are used for calculating $b_1$ and their results are compared with the HERMES measurement. We found large differences between our theoretical results and the data. Although there is still room to improve by considering higher-twist effects and in the experimental extraction of $b_1$ from the spin asymmetry $A_{zz}$, there is a possibility that the large differences require physics beyond the standard deuteron model for their interpretation. Future $b_1$ studies could shed light on a new field of hadron physics. In particular, detailed experimental studies of $b_1$ will start soon at the Thomas Jefferson National Accelerator Facility. In addition, there are possibilities to investigate tensor-polarized parton distribution functions and $b_1$ at Fermi National Accelerator Laboratory and a future electron-ion collider. Therefore, further theoretical studies are needed for understanding the tensor structure of the spin-1 deuteron, including a new mechanism to explain the large differences between the current data and our theoretical results.

   ↳ hep-phhep-exhep-latnucl-ex+1PRD(2017)·48 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.