Nuclear Theory·nucl-th

Tuesday·January 12, 2021

13 papers—7 primary·6 cross-listed

08
Studies on the $K^{*} Σ$ bound-state via $K^{+} p \to K^{+} ϕ p$
Seung-il Nam🇰🇷
In the present work, we investigate the hidden-strangeness production process in the $S = + 1$ channel via $K^{+} p \to K^{+} ϕ p$ , focussing on the exotic \textit{pentaquark} molecular $K^{*} Σ$ bound state, assigned by $P_{s}^{+} (2071, 3/ 2^{-})$ . For this purpose, we employ the effective Lagrangian approach in the tree-level Born approximation. Using the experimental and theoretical inputs for the exotic state and for the ground-state hadron interactions, the numerical results show a small but obvious peak structure from $P_{s}^{+}$ with the signal-to-background ratio $\approx 1.7 %$ , and it is enhanced in the backward-scattering region of the outgoing $K^{+}$ in the center-of-mass frame. We also find that the contribution from the $K^{*} (1680, 1^{-})$ meson plays an important role to reproduce the data. The proton-spin polarizations are taken into account to find a way to reduce the background. The effects of the possible $27$ -plet pentaquark $Θ_{27}^{++}$ is discussed as well.
↳ hep-phhep-exnucl-thPRD(2021)·7 citations
09
Hybrid nature of the abnormal solutions of the Bethe-Salpeter equation in the Wick-Cutkosky model
J. Carbonell · V.A. Karmanov ans H. Sazdjian
In the Wick-Cutkosky model, where two scalar massive constituents interact by means of the exchange of a scalar massless particle, the Bethe-Salpeter equation has solutions of two types, called "normal" and "abnormal". In the non-relativistic limit, the normal solutions correspond to the usual Coulomb spectrum, whereas the abnormal ones do not have non-relativistic counterparts -- they are absent in the Schrödinger equation framework. We have studied, in the formalism of the light-front dynamics, the Fock-space content of the abnormal solutions. It turns out that, in contrast to the normal ones, the abnormal states are dominated by the massless exchange particles (by 90 \% or more), what provides a natural explanation of their decoupling from the two-body Schrödinger equation. Assuming that one of the massive constituents is charged, we have calculated the electromagnetic elastic form factors of the normal and abnormal states, as well as the transition form factors. The results on form factors confirm the many-body nature of the abnormal states, as found from the Fock-space analysis. The abnormal solutions have thus properties similar to those of hybrid states, made here essentially of two massive constituents and several or many massless exchange particles. They could also be interpreted as the Abelian scalar analogs of the QCD hybrid states. The question of the validity of the ladder approximation of the model is also examined.
↳ hep-phnucl-thEPJC(2021)·6 citations
10
Light-front dynamic analysis of the longitudinal charge density using the solvable scalar field model in (1+1) dimensions
Yongwoo Choi🇰🇷 · Ho-Meoyng Choi🇰🇷 · Chueng-Ryong Ji🇺🇸 · Yongseok Oh🇰🇷
We investigate the electromagnetic form factor $F (q^{2})$ of the meson by using the solvable $ϕ^{3}$ scalar field model in $(1 + 1)$ dimensions. As the transverse rotations are absent in $(1 + 1)$ dimensions, the advantage of the light-front dynamics (LFD) with the light-front time $x^{+} = x^{0} + x^{3}$ as the evolution parameter is maximized in contrast to the usual instant form dynamics (IFD) with the ordinary time $x^{0}$ as the evolution parameter. In LFD, the individual $x^{+}$ -ordered amplitudes contributing to $F (q^{2})$ are invariant under the boost, i.e., frame-independent, while the individual $x^{0}$ -ordered amplitudes in IFD are not invariant under the boost but dependent on the reference frame. The LFD allows to get the analytic result for the one-loop triangle diagram which covers not only the spacelike ( $q^{2} < 0$ ) but also timelike region ( $q^{2} > 0$ ). Using the analytic results, we verify that the real and imaginary parts of the form factor satisfy the dispersion relations in the entire $q^{2}$ space. Comparing with the results in $(3 + 1)$ dimensions, we discuss the transverse momentum effects on $F (q^{2})$ . We also discuss the longitudinal charge density in terms of the boost invariant variable $z ~ = p^{+} x^{-}$ in LFD.
↳ hep-phnucl-thPRD(2021)·5 citations
11
Hot spots and gluon field fluctuations as causes of eccentricity in small systems
S. Demirci🇫🇮 · T. Lappi🇫🇮 · S. Schlichting🇩🇪
We calculate eccentricities in high energy proton-nucleus collisions, by calculating correlation functions of the energy density field of the Glasma immediately after the collision event at proper time tau = 0. We separately consider the effects of color charge and geometrical hot spot fluctuations, analytically performing the averages over both in a dilute-dense limit. We show that geometric fluctuations of hot spots inside the proton are the dominant source of eccentricity whereas color charge fluctuations only give a negligible correction. The size and number of hot spots are the most important parameters characterizing the eccentricities.
↳ hep-phnucl-thPRD(2021)·24 citations
12
Remarks on Static Three-Quark Potentials, String Breaking and Gauge/String Duality
Oleg Andreev🇷🇺
Making use of the gauge/string duality, it is possible to study some aspects of the string breaking phenomenon in the three quark system. Our results point out that the string breaking distance is not universal and depends on quark geometry. The estimates of the ratio of the string breaking distance in the three quark system to that in the quark-antiquark system would range approximately from $\frac{2}{3}$ to $1$ . In addition, it is shown that there are special geometries which allow more than one breaking distance.
↳ hep-phhep-lathep-thnucl-thPRD(2021)·22 citations
13
Experimental evidence of (M1+E2) mixed character of the 9.2 keV transition in $^{227}$ Th and its consequence for spin-interpretation of low-lying levels
A. Kovalík (1 and 2) · A. Kh. Inoyatov (1 and 3) · L. L. Perevoshchikov (1) · M. Ryšavý (2). D. V. Filosofov (1) · P. Alexa (4) · J. Kvasil (5) ((1) JINR Dubna, (2) NPI Řež near Prague, (3) Institute of Applied Physics, Tashkent, (4) Technical University, Ostrava, (5) Institute of Particle and Nuclear Physics, Prague)
The 9.2 keV nuclear transition in $^{227}$ Th populated in the $β$ -decay of $^{227}$ Ac was studied by means of the internal conversion electron spectroscopy. Its multipolarity was proved to be of mixed character M1+E2 and the spectroscopic admixture parameter $δ^{2}$ (E2/M1)=0.695 $\pm$ 0.248 (| $δ$ (E2/M1)|=0.834 $\pm$ 0.210) was determined. Nonzero value of $δ$ (E2/M1) raises a question about the existing theoretical interpretation of low-lying levels of $^{227}$ Th.
↳ nucl-exnucl-thPLB(2021)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE

Studies on the K∗Σ bound-state via K+p→K+ϕp

Hybrid nature of the abnormal solutions of the Bethe-Salpeter equation in the Wick-Cutkosky model

Light-front dynamic analysis of the longitudinal charge density using the solvable scalar field model in (1+1) dimensions

Hot spots and gluon field fluctuations as causes of eccentricity in small systems

Remarks on Static Three-Quark Potentials, String Breaking and Gauge/String Duality

Experimental evidence of (M1+E2) mixed character of the 9.2 keV transition in 227Th and its consequence for spin-interpretation of low-lying levels

Affiliations

Studies on the $K^{*} Σ$ bound-state via $K^{+} p \to K^{+} ϕ p$

Experimental evidence of (M1+E2) mixed character of the 9.2 keV transition in $^{227}$ Th and its consequence for spin-interpretation of low-lying levels