Using a data sample corresponding to an integrated luminosity of 2.93 fb −1 collected at a centerof-mass energy of 3.773 GeV with the BESIII detector at the BEPCII collider, we search for a scalar partner of the X(3872), denoted as X(3700), via ψ(3770) → γηη and γπ + π − J/ψ processes. No significant signals are observed and the upper limits of the product branching fractions B(ψ(3770) → γX(3700))•B(X(3700) → ηη ) and B(ψ(3770) → γX(3700))•B(X(3700) → π + π − J/ψ) are determined at the 90% confidence level, for the narrow X(3700) with a mass ranging from 3710 to 3740 MeV/c 2 , which are from 0.8 to 1.8 (×10 −5 ) and 0.9 to 3.4 (×10 −5 ), respectively.

We measure the branching fractions for psi(3770)-->D(0)D[over ](0), D+D-, DD[over ], and non-DD[over ] to be (46.7+/-4.7+/-2.3)%, (36.9+/-3.7+/-2.8)%, (83.6+/-7.3+/-4.2)%, and (16.4+/-7.3+/-4.2)%, respectively. The resonance parameters of psi(3770) and psi(2S) are measured to be M_(psi(3770))=3772.2+/-0.7+/-0.3 MeV, Gamma_(psi(3770))(tot)=26.9+/-2.4+/-0.3 MeV, and Gamma_(psi(3770))(ee)=251+/-26+/-11 eV; M_(psi(2S))=3685.5+/-0.0+/-0.3 MeV, Gamma_(psi(2S))(tot)=331+/-58+/-2 keV, and Gamma_(psi(2S))(ee)=2.330+/-0.036+/-0.110 keV. We also measure the light hadron R value to be R(uds)=2.262+/-0.054+/-0.109 in the energy region from 3.660 to 3.872 GeV.

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The Giffen effect is a particular economic phenomenon that only occurs in a specific background. Due to its effect on both commodity and labor markets, the Giffen effect became an irreplaceable phenomenon in the development of economy and society. Despite the fact that it is a rare incidence, it still can be found in daily life. Under the circumstance of COVID-19, the mask is a quintessential example of the Giffen goods. At the same time, the mask provides a more tangible explanation of the Giffen effect. This study mainly focuses on explaining the Giffen effect and its influence on the commodity and labor market. Furthermore, the paper also helps to illustrate the real-life example of Giffen goods. The terminal goal of the study is to explore the effects of Giffen goods, and provide others about the idea of the Giffen effect and figure out its main characters. This study also provides a reference for researchers who are interested in this area and willing to spend more time exploring it.