Nuclear Theory·nucl-th

Friday·August 27, 2021

13 papers—7 primary·6 cross-listed

08
From the lineshape of the $X (3872)$ to its structure
Angelo Esposito🇨🇭 · Luciano Maiani🇮🇹 · Alessandro Pilloni🇮🇹 · Antonio D. Polosa🇮🇹 · Veronica Riquer🇮🇹
From a study of the lineshape of the $X (3872)$ , the LHCb collaboration measures a sizeable negative effective range. This cannot be reconciled with a shallow $D D ˉ^{*}$ bound state hypothesis. Based on Weinberg's compositeness criterion, together with a theorem by Smorodinsky, it follows that the $X$ has to have a compact hidden charm structure, most likely a tetraquark, interacting with unbound $D D ˉ^{*}$ pairs via short-distance color forces. This conclusion is strengthened by the general pattern recently emerging for exotic mesons.
↳ hep-phnucl-thPRD(2022)·72 citations
09
Valence quark ratio in the proton
Zhu-Fang Cui🇨🇳 · Fei Gao🇩🇪 · Daniele Binosi🇮🇹 · Lei Chang🇨🇳 · Craig D. Roberts🇨🇳 · Sebastian M. Schmidt🇩🇪
Beginning with precise data on the ratio of structure functions in deep inelastic scattering (DIS) from $^{3}$ He and $^{3}$ H, collected on the domain $0.19 \leq x_{B} \leq 0.83$ , where $x_{B}$ is the Bjorken scaling variable, we employ a robust method for extrapolating such data to arrive at a model-independent result for the $x_{B} = 1$ value of the ratio of neutron and proton structure functions. Combining this with information obtained in analyses of DIS from nuclei, corrected for target-structure dependence, we arrive at a prediction for the proton's valence-quark ratio: $d_{v} / u_{v} ∣_{x_{B} \to 1} = 0.230 (57)$ . Requiring consistency with this result presents a challenge to many descriptions of proton structure.
↳ hep-phhep-exhep-latnucl-ex+1Chin.Phys.Lett.(2022)·24 citations
10
Near-threshold Spectrum from Uniformized Mittag-Leffler Expansion -Pole Structure of $Z (3900)$ -
Wren A. Yamada🇯🇵 · Osamu Morimatsu🇯🇵 · Toru Sato🇯🇵 · Koichi Yazaki🇯🇵
We demonstrate how S-matrix poles manifest themselves as the physical spectrum near the upper threshold in the context of the two-channel uniformized Mittag-Leffler expansion, an expression written as a sum of pole terms under an appropriate variable where the S-matrix is made single-valued (uniformization). We show that the transition of the spectrum is continuous as a S-matrix pole moves across the boundaries of the complex energy Riemann sheets and that the physical spectrum peaks at or near the upper threshold when the S-matrix pole is positioned sufficiently close to it on the uniformized plane. There is no essential difference on which sheet the pole is positioned. What is important is the existence of a pole near the upper threshold and the distance between the pole and the physical region, not on which complex energy sheet the pole is positioned. We also point out that when the pole is close to the upper threshold, the complex pole does not have the usual meaning of the resonance. Neither the real part represents the peak energy, nor the imaginary part represents the half width. Subsequently, we try to understand the current status of $Z (3900)$ from the viewpoint of the uniformized Mittag-Leffler expansion reflecting in particular, Phys.Rev.Lett.117, 242001 (2016) in which they concluded that $Z (3900)$ is not a conventional resonance but a threshold cusp. We point out that their results turn out to indicate the existence of S-matrix poles near the $D ˉ D^{*}$ threshold, which is most likely the origin of the peak found in their calculation of the near-threshold spectrum. In order to support our argument, we set up a separable potential model which shares common behavior of poles near the $D ˉ D^{*}$ threshold to the above-mentioned reference and show in our model that the structures near the $D ˉ D^{*}$ threshold are indeed caused by these near-threshold poles.
↳ hep-phnucl-thPRD(2022)·14 citations
11
Symmetry classification of uniform states in spin-2 Bose-Einstein condensates and neutron $^{3} P_{2}$ superfluids
Michikazu Kobayashi · Muneto Nitta
We clarify a relation between the Gross-Pitaevskii energy functional for spin-2 spinor Bose-Einstein condensates and the Ginzburg-Landau theory for neutron $^{3} P_{2}$ superfluidis (spin-triplet $P$ -wave pairing with total angular momentum two). We then classify all uniform states with nontrivial unbroken symmetries, with the help of geometric invariant theory.
↳ cond-mat.quant-gasnucl-thPRA(2021)·4 citations
12
Numerical Study on Beam-based Alignment of SXFEL Undulator Lattice
Liang Xu🇨🇳 · Nanshun Huang🇨🇳 · Qingmin Zhang🇨🇳 · Duan Gu🇨🇳 · Haixiao Deng🇨🇳
The undulator line of the Shanghai soft X-ray Free-electron Laser facility (SXFEL) has very tight tolerances on the straightness of the electron beam trajectory. However, the beam trajectory cannot meet the lasing requirements due to the influence of beam position, launch angle and quadrupole offsets. Traditional mechanical alignment can only control the rms of offsets to about 100 $μ$ m, which is far from reaching the requirement. Further orbit correction can be achieved by beam-based alignment (BBA) method based on electron energy variations. K modulation is used to determine whether the beam passes through the quadrupole magnetic center, and the Dispersion-Free Steering (DFS) method is used to calculate the offsets of quadrupole and BPM. In this paper, a detailed result of simulation is presented which demonstrates that the beam trajectory with rms and standard deviation ( $σ$ ) less than 10 $μ$ m can be obtained.
↳ physics.acc-phnucl-thProc.SPIE Int.Soc.Opt.Eng.(2022)·0 citations
13
Quantized electrical conductivity in binary neutron star mergers
Sreemoyee Sarkar🇮🇳 · Souvik Priyam Adhya🇵🇱
We examine nature of longitudinal electrical conductivity in magnetized electron-ion plasma in the context of binary neutron star mergers. In presence of strong magnetic field, high density and temperature, quantum oscillatory behaviour for electrons emerge due to breakdown of the classical description. For pronounced thermodynamic effects, we consider zeroth Landau level population of electrons for electrical conductivity. We solve Boltzmann equation in presence of magnetic field to obtain the dissipative component of the conductivity. The conductivity is formulated considering dynamically scattering centres in the medium with magnetically modified screening. Numerical estimations show that the effect of magnetically modified screening mass on electrical conductivity is less. On the other hand, we observe that frequency dependent screening reduces electrical conductivity leading to a reduction in the Ohmic decay time scale to become of the order of the characteristic timescale of the merger process in the low density regime. This indicates the relevance of dissipative process for the merger simulation in the above mentioned domain.
↳ hep-phastro-ph.HEnucl-thphysics.plasm-ph1 citation

Affiliations

first authorsco-authorsvia INSPIRE

From the lineshape of the X(3872) to its structure

Valence quark ratio in the proton

Near-threshold Spectrum from Uniformized Mittag-Leffler Expansion -Pole Structure of Z(3900)-

Symmetry classification of uniform states in spin-2 Bose-Einstein condensates and neutron 3P2​ superfluids

Numerical Study on Beam-based Alignment of SXFEL Undulator Lattice

Quantized electrical conductivity in binary neutron star mergers

Affiliations

From the lineshape of the $X (3872)$ to its structure

Near-threshold Spectrum from Uniformized Mittag-Leffler Expansion -Pole Structure of $Z (3900)$ -

Symmetry classification of uniform states in spin-2 Bose-Einstein condensates and neutron $^{3} P_{2}$ superfluids