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

Very recently, the LHCb Collaboration released the newest measurements of $B_s \to J/\psi p\bar{p}$, where an enhancement structure near 4.34 GeV was observed in the invariant mass spectrum of $J/\psi p$ with the statistical significance of $3.1\sim 3.7$ $\sigma$. In this work, by performing a combined analysis for the three invariant mass spectra of $B_s \to J/\psi p\bar{p}$, we find that this $J/\psi p$ structure near 4.34 GeV can correspond to the contributions from the $P_c(4380)^+$ state with the assumption of $J^{P}=3/2^{-}$ together with the reflections of $B_s \to (f_2^{*} \to p\bar{p})J/\psi$. Here, $P_c(4380)$ was first observed in $\Lambda_b \to J/\psi p K$ but not confirmed in the updated LHCb data in 2019, and $f_2^{*}$ means the exciting light isoscalar tensor meson around 2.0 GeV. Thus, this provides a possible evidence to support the existence of the pentaquark $P_c(4380)$. Specifically, the assumed spin-parity $J^{P}=3/2^{-}$ of $P_c(4380)$ is consistent with a prediction of the theoretical explanation of an $S$-wave $\bar{D}\Sigma_c^*$ molecular bound state.

The evidence supporting the existence of $P_c(4380)^{\pm}$ from the recent measurements of $B_s \to J/\psi p\bar{p}$

Fu-Lai Wang1,2,3,∗ Si-Qiang Luo1,2,3,† Hong-Yan Zhou1,2,‡ Zhan-Wei Liu1,2,3,§ and Xiang Liu1,2,3,4¶ 1School of Physical Science and Technology, Lanzhou University, Lanzhou 730000, China 2Research Center for Hadron and CSR Physics, Lanzhou University and Institute of Modern Physics of CAS, Lanzhou 730000, China 3Lanzhou Center for Theoretical Physics, Key Laboratory of Theoretical Physics of Gansu Province, and Frontiers Science Center for Rare Isotopes, Lanzhou University, Lanzhou 730000, China 4Key Laboratory of Quantum Theory and Applications of MoE, Lanzhou University, Lanzhou 730000, China

D̄s molecular states

We study the so-called magic mixing angles for doubly heavy baryons. Defining that a magic mixing angle rotates states with definite $^{2S+1}(l_\lambda)_J$ to make them heavy-quark symmetric states, we derive the magic mixing angle only in the case $L_\rho=0$ between the heavy quark symmetric states with quantum numbers $\left(J, j_\ell\right)$ and the states with $\left(J, s_q+j_\rho\right)=\left(J, \{^4l_\lambda/^2l_\lambda\}\right)$ for a doubly heavy baryon in the standard $\rho-\lambda$ configuration, where $\vec j_\ell=\vec l_\lambda+\vec s_q$, $\vec s_\rho=\vec s_{Q1}+\vec s_{Q2}$, and $\vec j_\rho=\vec s_\rho+\vec L_\rho$. We discuss how this mixing angle affects model building for a doubly heavy baryon.

Magic mixing angles for doubly heavy baryons

Recently, the BaBar Collaboration reported a broad resonance structure near 2 GeV when analyzing the e + e − → f 1 (1285) π + π − process, which provides a good opportunity to study the higher ρ mesonic states. When considering the ρ (1900) and ρ (2150) contributions, the experimental data of the cross section of e + e − → f 1 (1285) π + π − around 2 GeV can be well depicted, especially the observed broad resonance structure in e + e − → f 1 (1285) π + π − containing two substructures is suggested by the present work. Additionally, we also indicate a possible signal of ρ (5 S ) around 2.5 GeV in the e + e − → f 1 (1285) π + π − process. The obtained result may provide valuable hint to identify higher ρ mesons, which will be a new task for the BESIII and Belle II experiments with the accumulation of higher precision data.

Broad enhancement structure existing in e + e − → f 1 (1285) π + π − excited by higher ρ mesons

In this work, we explore the decay channels $Y(4220)\to\Lambda\bar{\Lambda}$ and $\Xi^-\bar{\Xi}^+$ by treating the $Y(4220)$ as a vector charmonium state. The possible signals of the $Y(4220)$ in the $\Lambda\bar{\Lambda}$ and $\Xi^-\bar{\Xi}^+$ channels are pointed out. Based on the hadronic loop mechanism, the extracted branching ratios of the $Y(4220)\to\Lambda\bar{\Lambda}$ and $\Xi^-\bar{\Xi}^+$ processes are reproduced, and the ratio and phase of the time-like electromagnetic form factors (EMFFs) are predicted. For the EMFFs of $\Lambda$ at $\sqrt{s}=m_{Y(4220)}$, $|G_E^\Lambda /G_M^\Lambda|$ and $\Delta\Phi^\Lambda$ are predicted to be $|G_E^\Lambda /G_M^\Lambda|=2.36$ and $\Delta\Phi^\Lambda=2.74^\circ$, and those of $\Xi^-$ are predicted to be $|G_E^{\Xi^-}/G_M^{\Xi^-}|=0.40$ and $\Delta\Phi^{\Xi^-}=-115.60^\circ$. These predictions can be treated as tests for the charmonium assignment of the $Y(4220)$.

Xiang Liu

Papers

The evidence supporting the existence of $P_c(4380)^{\pm}$ from the recent measurements of $B_s \to J/\psi p\bar{p}$

D̄s molecular states

Magic mixing angles for doubly heavy baryons

Broad enhancement structure existing in e + e − → f 1 (1285) π + π − excited by higher ρ mesons

The induced $\Lambda\bar{\Lambda}$ and $\Xi^-\bar{\Xi}^+$ decay modes of the $Y(4220)$ as a vector charmonium