Analytic continuation of nucleon electromagnetic form factors in the time-like region

The possibility to compute nucleon electromagnetic form factors in the time-like region by analytic continuation of their space-like expressions has been explored in the framework of the Skyrme model. We have developed a procedure to solve analytically Fourier transforms of the nucleon electromagnetic current and hence to obtain form factors defined in all kinematical regions and fulfilling the first-principles requirements. The results are discussed and compared to data, both in space-like and time-like region.Comment: 34 pages, 15 figure

Theoretical and Experimental Essentials on Baryon Form Factors

This brief review is a practical guide on the basic concepts, pivotal formulae, standard relations, and some unusual, often forgotten, but sometimes revealing features of baryons' form factors. All available measured values of nucleon form factors in the space-like and time-like regions extracted from scattering and annihilation cross-sections are also reported

Radiotherapy Timing in 4,820 Patients With Breast Cancer: University of Florence Experience

PURPOSE: To analyze the relationship between a delay in radiotherapy (RT) after breast-conserving surgery and ipsilateral breast recurrence (BR). METHODS AND MATERIALS: We included in our analysis 4,820 breast cancer patients who had undergone postoperative RT at the University of Florence. The patients were categorized into four groups according to the interval between surgery and RT (T1, 180 days). RESULTS: On multivariate analysis, the timing of RT did not reach statistical significance in patients who received only postoperative RT (n = 1,935) or RT and hormonal therapy (HT) (n = 1,684) or RT, chemotherapy (CHT), and HT (n = 529). In the postoperative RT-only group, age at presentation, surgical margin status, and a boost to the tumor bed were independent prognostic factors for BR. In the RT plus HT group, age at presentation and boost emerged as independent prognostic factors for BR (p = 0.006 and p = 0.049, respectively). Finally, in the RT, CHT, and HT group, only multifocality was an independent BR predictor (p = 0.01). Only in the group of patients treated with RT and CHT (n = 672) did multivariate analysis with stepwise selection show RT timing as an independent prognostic factor (hazard ratio, 1.59; 95% confidence interval, 1.01-2.52; p = 0.045). Analyzing this group of patients, we found that most patients included had worse prognostic factors and had received CHT consisting of cyclophosphamide, methotrexate, and 5-fluorouracil before undergoing RT. CONCLUSION: The results of our study have shown that the timing of RT itself does not affect local recurrence, which is mainly related to prognostic factors. Thus, the "waiting list" should be thought of as a "programming list," with patients scheduled for RT according to their prognostic factors

Serum Albumin Is Inversely Associated With Portal Vein Thrombosis in Cirrhosis

We analyzed whether serum albumin is independently associated with portal vein thrombosis (PVT) in liver cirrhosis (LC) and if a biologic plausibility exists. This study was divided into three parts. In part 1 (retrospective analysis), 753 consecutive patients with LC with ultrasound-detected PVT were retrospectively analyzed. In part 2, 112 patients with LC and 56 matched controls were entered in the cross-sectional study. In part 3, 5 patients with cirrhosis were entered in the in vivo study and 4 healthy subjects (HSs) were entered in the in vitro study to explore if albumin may affect platelet activation by modulating oxidative stress. In the 753 patients with LC, the prevalence of PVT was 16.7%; logistic analysis showed that only age (odds ratio [OR], 1.024; P = 0.012) and serum albumin (OR, -0.422; P = 0.0001) significantly predicted patients with PVT. Analyzing the 112 patients with LC and controls, soluble clusters of differentiation (CD)40-ligand (P = 0.0238), soluble Nox2-derived peptide (sNox2-dp; P < 0.0001), and urinary excretion of isoprostanes (P = 0.0078) were higher in patients with LC. In LC, albumin was correlated with sCD4OL (Spearman's rank correlation coefficient [r(s)], -0.33; P < 0.001), sNox2-dp (r(s), -0.57; P < 0.0001), and urinary excretion of isoprostanes (r(s), -0.48; P < 0.0001) levels. The in vivo study showed a progressive decrease in platelet aggregation, sNox2-dp, and urinary 8-iso prostaglandin F2 alpha-III formation 2 hours and 3 days after albumin infusion. Finally, platelet aggregation, sNox2-dp, and isoprostane formation significantly decreased in platelets from HSs incubated with scalar concentrations of albumin. Conclusion: Low serum albumin in LC is associated with PVT, suggesting that albumin could be a modulator of the hemostatic system through interference with mechanisms regulating platelet activation

J/ψ decays into baryon-antibaryon pairs

In 2019 the BESIII Collaboration collected a sample of 10 billions of J/ψ events and, using about 1.3 × 109 of them, observed baryon polarization in baryon-antibaryon decays, publishing a paper in Nature Physics. Using new data from both PDG and BESIII experiment and a model based on an effective strong Lagrangian, we separate, for the first time, the strong and electromagnetic contributions to the total branching ratio of the J/ψ decays into a pair of spin-1/2 baryon-antibaryon, finding a relative phase of ϕ = (73 ± 8)◦

The first exploration of the physical Riemann surfaces of the ratio GEΛ/GMΛG_E^\Lambda/G_M^\Lambda

International audienceRecently, the BESIII experiment renewed the interest on baryon form factors by measuring the modulus and phase of the ratio GEΛ/GMΛ between the electric and the magnetic Λ form factors with unprecedented accuracy. The BESIII measurement together with older, less precise data, can be analyzed by means of a dispersive procedure based on analyticity and a set of first-principle constraints. Such a dispersive procedure shows the unique ability to determine, for the first time, the complex structure of the ratio knowing its modulus and phase measured by the BESIII Collaboration at only one energy point. Different classes of solutions are obtained, and in all cases, the timelike and spacelike behaviors show interesting properties; spacelike zeros or unexpected large determinations for the phase. More data at different energies would be crucial to enhance the predictive power of the dispersive procedure and to unravel further remarkable features of the Λ baryon

The cross section of

Under the aegis of isospin conservation, the amplitudes in Born approximation, i.e., considering the only one-photon-exchange mechanism, of the decay $$\psi \rightarrow \Lambda \overline{\Sigma }{}^0+\text {c.c.}$$, where $$\psi$$ is a vector charmonium, and of the reaction $$e^+e^-\rightarrow \Lambda \overline{\Sigma }{}^0+\text {c.c.}$$ at the $$\psi$$ mass, are parametrized by the same electromagnetic coupling. It follows that, the modulus of such a coupling can be extracted from the data on the two observables: the decay branching fraction and the annihilation cross section. By considering the first two vector charmonia, $$J/\psi$$ and $$\psi (2S)$$, it is found that, especially in the case of $$\psi (2S)$$, there is a substantial discrepancy between the values of the modulus of the same electromagnetic coupling extracted from the branching ratio and the cross section. We propose, as a possible explanation for such a disagreement, the presence in the decay amplitude of isospin-violating contributions driven by two different mechanisms, that, however, appear to be more favored in the $$\psi (2S)$$ than in the $$J/\psi$$ decays