Wed·Aug 18, 2021Wednesday·August 18, 2021

1. 01*

   Physics Opportunities with Meson Beams for EIC

   William J. Briscoe (GWU) · Michael Doring (GWU) · Helmut Haberzettl (GWU) · D. Mark Manley · (KSU) · Megumi Naruki (Kyoto University) · Greg Smith (JLab) · Igor Strakovsky (GWU) · Eric S. Swanson (University of Pittsburgh)

   Over the past two decades, meson photo- and electroproduction data of unprecedented quality and quantity have been measured at electromagnetic facilities worldwide. By contrast, the meson-beam data for the same hadronic final states are mostly outdated and largely of poor quality, or even non-existent, and thus provide inadequate input to help interpret, analyze, and exploit the full potential of the new electromagnetic data. To reap the full benefit of the high-precision electromagnetic data, new high-statistics data from measurements with meson beams, with good angle and energy coverage for a wide range of reactions, are critically needed to advance our knowledge in baryon and meson spectroscopy and other related areas of hadron physics. To address this situation, a state-of-the-art meson-beam facility needs to be constructed. The present letter summarizes unresolved issues in hadron physics and outlines the vast opportunities and advances that only become possible with such a facility.

   nucl-exhep-exhep-phnucl-th6 citations
2. 02*

   Structure of ${}^{43}$P and ${}^{42}$Si in a two-level shape-coexistence model

   A. O. Macchiavelli🇺🇸 · H. L. Crawford🇺🇸 · C. M. Campbell🇺🇸 · R. M. Clark · M. Cromaz🇺🇸 · P. Fallon · I. Y. Lee · A. Gade🇺🇸 · A. Poves🇪🇸 · E. Rice🇺🇸

   Exclusive cross sections for the ${}^{43}$P$(-1p{)}^{42}$Si reaction to the lowest $0^{+}$ and $2^{+}$ states, measured at NSCL with GRETINA and the S800, are interpreted in terms of a two-level mixing (collective) model of oblate and prolate co-existing shapes. Using the formalism developed for deformed nuclei we calculate the spectroscopic amplitudes and exclusive cross-sections in the strong coupling limit, where for ${}^{43}$P the schematic wavefunction includes the coupling of the Nilsson [211]$\frac{1}{2}$ proton orbit. Good agreement with the experimental data is obtained when the amplitude of the oblate configuration is $\gtrsim$ 80\%, suggesting that both nuclei are predominantly oblate, in line with theoretical expectations.

   ↳ nucl-thnucl-exPRC(2022)·7 citations
3. 03*

   Description of isospin mixing by a generator coordinate method

   M. Kimura🇯🇵 · Y. Suzuki🇯🇵 · T. Baba · Y. Taniguchi🇯🇵

   Background: The isospin mixing is an interesting feature of atomic nuclei. It plays a crucial role in astrophysical nuclear reactions. However, it is not straightforward for variational nuclear structure models to describe it. Purpose: We propose a tractable method to describe the isospin mixing within a framework of the generator coordinate method and demonstrate its usability. Method: We generate the basis wave functions by applying the Fermi transition operator to the wave functions of isobars. The superposition of these basis wave functions and variationally obtained wave functions quantitatively describes the isospin mixing. Results: Using 14N as an example, we demonstrate that our method reasonably describes both T = 0 and 1 states and their mixing. Energy spectrum and E1 transition strengths are compared with the experimental data to confirm isospin mixing. Conclusion: The proposed method is effective enough to describe isospin mixing and is useful, for example, when we discuss {\alpha} capture reactions of N = Z nuclei.

   ↳ nucl-thnucl-exPRC(2022)·1 citation
4. 04*

   Longitudinal and transverse polarizations of $\Lambda$ hyperon in unpolarized SIDIS and $e^{+}{e}^{-}$ annihilation

   Kai-bao Chen🇨🇳 · Zuo-tang Liang🇨🇳 · Yu-kun Song🇨🇳 · Shu-yi Wei🇮🇹

   We make a systematic study of $\Lambda$ hyperon polarizations in unpolarized lepton induced semi-inclusive reactions such as $e^{-}N\to e^{-}\Lambda X$ and $e^{+}{e}^{-}\to \Lambda hX$. We present the general form of cross sections in terms of structure functions obtained from a general kinematic analysis. This already shows that the produced hyperons can be polarized in three orthogonal directions, i.e., the longitudinal direction along the hyperon momentum, the normal direction of the production plane, and the transverse direction in the production plane. We present the parton model results at the leading twist and leading order in perturbative QCD and provide the expressions for these structure functions and polarizations in terms of parton distribution functions and fragmentation functions. We emphasize in particular that by studying the longitudinal polarization and the transverse polarization in the production plane, we can extract the corresponding chiral-odd fragmentation functions $H_{1Lq}^{\perp \Lambda }$, $H_{1Tq}^{\Lambda }$ and $H_{1Tq}^{\perp \Lambda }$. We also present numerical results of rough estimates utilizing available parameterizations of fragmentation functions and approximations. We discuss how to measure these polarizations and point out in particular that they can be carried out in future EIC and/or $e^{+}{e}^{-}$ annihilation experiments such as Belle.

   ↳ hep-phhep-exnucl-exPRD(2022)·26 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.