Factorization in the Production and Decay of the X(3872)

The production and decay of the X(3872) are analyzed under the assumption that the X is a weakly-bound molecule of the charm mesons D^0 \bar D^{*0} and D^{*0} \bar D^0. The decays imply that the large D^0 \bar D^{*0} scattering length has an imaginary part. An effective field theory for particles with a large complex scattering length is used to derive factorization formulas for production rates and decay rates of X. If a partial width is calculated in a model with a particular value of the binding energy, the factorization formula can be used to extrapolate to other values of the binding energy and to take into account the width of the X. The factorization formulas relate the rates for production of X to those for production of D^0 \bar D^{*0} and D^{*0} \bar D^0 near threshold. They also imply that the line shape of X differs significantly from that of a Breit-Wigner resonance.Comment: 23 pages, 8 figures, revtex4, typos correcte

Production of the X(3872) in B Meson Decay by the Coalescence of Charm Mesons

If the recently-discovered charmonium state X(3872) is a loosely-bound S-wave molecule of the charm mesons \bar D^0 D^{*0} or \bar D^{*0} D^0, it can be produced in B meson decay by the coalescence of charm mesons. If this coalescence mechanism dominates, the ratio of the differential rate for B^+ \to \bar D^0 D^{*0} K^+ near the \bar D^0 D^{*0} threshold and the rate for B^+ \to X K^+ is a function of the \bar D^0 D^{*0} invariant mass and hadron masses only. The identification of the X(3872) as a \bar D^0 D^{*0}/\bar D^{*0} D^0 molecule can be confirmed by observing an enhancement in the \bar D^0 D^{*0} invariant mass distribution near the threshold. An estimate of the branching fraction for B^+ \to X K^+ is consistent with observations if X has quantum numbers J^{PC} = 1^{++} and if J/\psi \pi^+ \pi^- is one of its major decay modes.Comment: 4 pages, 3 figures, revtex

Scattering Models for Ultracold Atoms

We present a review of scattering models that can be used to describe the low-energy behavior of identical bosonic atoms. In the simplest models, the only degrees of freedom are atoms in the same spin state. More elaborate models have other degrees of freedom, such as atoms in other spin states or diatomic molecules. The parameters of the scattering models are specified by giving the S-wave phase shifts for scattering of atoms in the spin state of primary interest. The models are formulated as local quantum field theories and the renormalization of their coupling constants is determined. Some of the parameters can be constrained by renormalizability or by the absence of negative-norm states. The Green's functions that describe the evolution of two-atom states are determined analytically. They are used to determine the T-matrix elements for atom-atom scattering and the binding energies of diatomic molecules. The scattering models all exhibit universal behavior as the scattering length in a specific spin state becomes large.Comment: 60 pages, 6 figures, minor correction

いわゆる第1波，第2波までのCOVID-19肺炎患者151例の臨床放射線学的特徴の検討

Introduction : Coronavirus Disease 2019 (COVID-19) has caused serious illness and numerous deaths worldwide. We evaluated the clinical features and initial chest computed tomography (CT) findings of 151 patients with COVID-19 pneumonia with the aim of comparison between first and second waves and exploring the factors associating the deterioration of oxygenation status during the clinical course. / Methods : We retrospectively enrolled 151 patients with COVID-19 pneumonia, diagnosed by reverse transcription-polymerase chain reaction (RT-PCR) and evaluated their clinical findings and CT imaging characteristics. The extent of pneumonia was evaluated visually and semi-quantitatively by the distribution of ground glass opacity (GGO) as follows : none, localized lesion, ＜25% involvement of the whole lung, ＞ 25% and ＜ 50% involvement and ＞ 50% involvement. We also evaluated the presence of crazy-paving appearance, consolidation, and linear opacity. / Results : The visual extent of GGO was positively correlated with shortness of breath, requirement of oxygen therapy at admission, the duration from onset to CT (B6 days), and the presence of a crazy-paving appearance and linear opacity. Most of the localized lesions showed a peripheral and non-segmental distribution. Patients in the second wave had a high rate of infection at dinner party, and generally had mild clinical symptoms. Exacerbation of oxygenation status after admission was significantly associated with age, hypertension, diabetes, higher value of body mass index (BMI), C-reactive protein (CRP), D-dimer, alanine aminotransferase, and a wider distribution of GGO. / Conclusion : The extent of GGO reflects the severity of pneumonia. It is also associated with deterioration of oxygenation status after admission