There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

비만아 부모의 돌봄 경험: q 방법론

A golden age for heavy-quarkonium physics dawned a decade ago, initiated by the confluence of exciting advances in quantum chromodynamics (QCD) and an explosion of related experimental activity. The early years of this period were chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in 2004, which presented a comprehensive review of the status of the field at that time and provided specific recommendations for further progress. However, the broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles could only be partially anticipated. Since the release of the YR, the BESII program concluded only to give birth to BESIII; the B-factories and CLEO-c flourished; quarkonium production and polarization measurements at HERA and the Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the deconfinement regime. All these experiments leave legacies of quality, precision, and unsolved mysteries for quarkonium physics, and therefore beg for continuing investigations at BESIII, the LHC, RHIC, FAIR, the Super Flavor and/or Tau-Charm factories, JLab, the ILC, and beyond. The list of newly found conventional states expanded to include h(c)(1P), chi(c2)(2P), B-c(+), and eta(b)(1S). In addition, the unexpected and still-fascinating X(3872) has been joined by more than a dozen other charmonium- and bottomonium-like "XYZ" states that appear to lie outside the quark model. Many of these still need experimental confirmation. The plethora of new states unleashed a flood of theoretical investigations into new forms of matter such as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the spectroscopy, decays, production, and in-medium behavior of c (c) over bar, b (b) over bar, and b (c) over bar bound states have been shown to validate some theoretical approaches to QCD and highlight lack of quantitative success for others. Lattice QCD has grown from a tool with computational possibilities to an industrial-strength effort now dependent more on insight and innovation than pure computational power. New effective field theories for the description of quarkonium in different regimes have been developed and brought to a high degree of sophistication, thus enabling precise and solid theoretical predictions. Many expected decays and transitions have either been measured with precision or for the first time, but the confusing patterns of decays, both above and below open-flavor thresholds, endure and have deepened. The intriguing details of quarkonium suppression in heavy-ion collisions that have emerged from RHIC have elevated the importance of separating hot- and cold-nuclear-matter effects in quark-gluon plasma studies. This review systematically addresses all these matters and concludes by prioritizing directions for ongoing and future efforts.

/pdf/heavy-quarkonium-progress-puzzles-and-opportunities-2tru0l8jyp.pdf

Heavy quarkonium: progress, puzzles, and opportunities

The measured masses and strong decays of ${\mathrm{\ensuremath{\Lambda}}}_{b}(6146{)}^{0}$ and ${\mathrm{\ensuremath{\Lambda}}}_{b}(6152{)}^{0}$ required us to decode them as the $1D$ excited states with ${J}^{P}=3/{2}^{+}$ and ${J}^{P}=5/{2}^{+}$, respectively. Under the suggested assignment, the masses and total decay widths of ${\mathrm{\ensuremath{\Lambda}}}_{b}(6146{)}^{0}$ and ${\mathrm{\ensuremath{\Lambda}}}_{b}(6152{)}^{0}$ can be explained. As a ${J}^{P}=3/{2}^{+}$ state, the ${\mathrm{\ensuremath{\Lambda}}}_{b}(6146{)}^{0}$ should mainly decay into ${\mathrm{\ensuremath{\Sigma}}}_{b}(5815)\ensuremath{\pi}$. However, this theoretical result is in contradiction to the measurement since no significant ${\mathrm{\ensuremath{\Lambda}}}_{b}(6146{)}^{0}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Sigma}}}_{b}(5815{)}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ensuremath{\mp}}$ signals were observed by the LHCb. The possible explanations for this difficulty are mentioned. For completeness, we present the prediction of masses and decay widths of other unseen $1D$ bottom baryons in this work. Our results could provide some important clues for the upcoming experiments.

Interpretation of the observed Λ b (6146 ) 0 and Λ b (6152 ) 0 states as 1 D bottom baryons

Considering the defects of the previous work for estimating the anomalous production rates of ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\Upsilon}(1S){\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$, $\ensuremath{\Upsilon}(2S){\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ near the peak of the $\ensuremath{\Upsilon}(5S)$ resonance at $\sqrt{s}=10.87\text{ }\text{ }\mathrm{GeV}$ [K. F. Chen et al. (Belle Collaboration), Phys. Rev. Lett. 100, 112001 (2008)], we suggest a new scenario where the contributions from the direct dipion transition and the final-state interactions interfere to result in not only the anomalously large production rates, but also line shapes of the differential widths consistent with experimental measurement when assuming the reactions are due to the dipion emission of $\ensuremath{\Upsilon}(5S)$. At the end, we raise a new puzzle that the predicted differential width $d\ensuremath{\Gamma}(\ensuremath{\Upsilon}(5S)\ensuremath{\rightarrow}\ensuremath{\Upsilon}(2S){\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})/d\mathrm{cos}﻿\ensuremath{\theta}$ has a discrepant trend from the data while other predictions are well in accord with the data. It should be further clarified by more accurate measurements carried by future experiments.

Dipion invariant mass distribution of the anomalous Υ ( 1 S ) π + π − and Υ ( 2 S ) π + π − production near the peak of Υ ( 10860 )

In this work, we propose a nonresonant explanation for the $Y(4260)$ structure observed in the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ process, i.e., $Y(4260)$ is not a genuine resonance. Our result indicates that the $Y(4260)$ structure can be reproduced by the interference of production amplitudes of the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ processes via direct ${e}^{+}{e}^{\ensuremath{-}}$ annihilation and through intermediate charmonia $\ensuremath{\psi}(4160)/\ensuremath{\psi}(4415)$. Besides describing the $Y(4260)$ line shape in ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ well, such a nonresonant explanation for the $Y(4260)$ structure naturally answers why there is no evidence of $Y(4260)$ in the exclusive open-charm decay channel and $R$-value scan.

Nonresonant explanation for the Y(4260) structure observed in the e{sup +}e{sup -}{yields}J/{psi}{pi}{sup +}{pi}{sup -} process

Inspired by the similarity between the mass gaps of the $$J/\psi $$
 and $$\Upsilon $$
 families, the prediction of a missing higher charmonium with mass 4,263 MeV and very narrow width is made. In addition, the properties of two charmonium-like states, $$X(3940)$$
 and $$X(4160)$$
 , and charmonium $$\psi (4415)$$
 are discussed, where our calculation shows that $$X(3940)$$
 as $$\eta _c(3S)$$
 is established, while the explanation of $$X(4160)$$
 to be $$\eta _c(4S)$$
 is fully excluded and that $$\eta _c(4S)$$
 is typically a very narrow state. These predictions might be accessible at BESIII, Belle, and BelleII in near future.

/pdf/prediction-of-a-missing-higher-charmonium-around-4-26-gev-in-1r7t3c40qn.pdf

Prediction of a missing higher charmonium around 4.26 GeV in $J/\psi$ family

In this work, we systematically study the two-body strong decay of the ρ/ρ3 states, which are observed and grouped into the ρ/ρ3 meson family By performing the phenomenological analysis, the underlying properties of these states are obtained and tested What is more important is that abundant information of their two-body strong decays is predicted, which will be helpful to further and experimentally study these states

Xiang Liu

Papers

Interpretation of the observed Λ b (6146 ) 0 and Λ b (6152 ) 0 states as 1 D bottom baryons

Dipion invariant mass distribution of the anomalous Υ ( 1 S ) π + π − and Υ ( 2 S ) π + π − production near the peak of Υ ( 10860 )

Nonresonant explanation for the Y(4260) structure observed in the e{sup +}e{sup -}{yields}J/{psi}{pi}{sup +}{pi}{sup -} process

Prediction of a missing higher charmonium around 4.26 GeV in $J/\psi$ family

Towards two-body strong decay behavior of higher ρ and ρ 3 mesons