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.

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Heavy quarkonium: progress, puzzles, and opportunities

In this review, we discuss some interesting issues in charm physics which is full with puzzles and challenges. So far in the field there exist many problems which have not obtained satisfactory answers yet and more unexpected phenomena have been observed at the present facilities of high energy physics. Charm physics may become an ideal place for searching new resonances and studying non-perturbative QCD effects, moreover probably is an area to explore new physics beyond the Standard Model. More data will be available at BESIII, B-factories, LHC and even future ILC which may open a wide window to a better understanding of the nature.

Charm Physics - A Field Full with Challenges and Opportunities

Erratum to “Novel charmonium-like structures in the J /ψ ϕ and J /ψ ω invariant mass spectra” [Phys. Lett. B 699 (2011) 341]

We revisit the B+→X(3872)+K+ in the pQCD approach assigning to X(3872) a 23P1 charmonium state. In this theoretical framework all the phenomenological parameters in the wavefunctions and Sudakov factor are a priori fixed by fitting other experimental data; therefore, there hardly are any free parameters in the whole numerical computations. Our results are larger than the upper bound set by the BABAR measurements.

Revisiting B+ -X(3872) + K+ in pQCD assigning to X(3872) 23P1 charmonium

We study the $\ensuremath{\eta}$ transitions between $\ensuremath{\psi}(4040/4160)$ and $J/\ensuremath{\psi}$ by introducing charmed meson loops in an effective Lagrangian approach to enhance the decay amplitudes. The branching fractions $\mathcal{B}[\ensuremath{\psi}(4040)\ensuremath{\rightarrow}J/\ensuremath{\psi}\ensuremath{\eta}]$ and $\mathcal{B}[\ensuremath{\psi}(4160)\ensuremath{\rightarrow}J/\ensuremath{\psi}\ensuremath{\eta}]$ estimated in this paper can remarkably explain the experimental measurements of Belle and BESIII within a reasonable parameter range. The ${\ensuremath{\eta}}^{\ensuremath{'}}$ transition between $\ensuremath{\psi}(4160)$ and $J/\ensuremath{\psi}$ is also investigated, and the branching fraction is under the upper limit of CLEO, which can be tested by future experiments.

η transitions between charmonia with meson loop contributions

Babar Collaboration announced two new excited charmed baryons $\Xi_c(3055)^+$ and $\Xi_c(3123)^+$. We study their strong decays assuming they are D-wave states. Some assignments are excluded by comparing our numerical results with the experimental values of the total widths of $\Xi_c(3055)^+$ and $\Xi_c(3123)^+$. We also suggest some possible decay modes, which will be helpful to determine the properties of $\Xi_c(3055)^+$ and $\Xi_c(3123)^+$.

Xiang Liu

Papers

Charm Physics - A Field Full with Challenges and Opportunities

Erratum to “Novel charmonium-like structures in the J /ψ ϕ and J /ψ ω invariant mass spectra” [Phys. Lett. B 699 (2011) 341]

Revisiting B+ -X(3872) + K+ in pQCD assigning to X(3872) 23P1 charmonium

η transitions between charmonia with meson loop contributions

A note on \Xi_c(3055)^+ and \Xi_c(3123)^+