Searching for new physics in D^0→μ^＋ μ^-,e^＋e^-,μ^±e at BES and/or the super charm-tau factory

In contrast with B0-ˉB0, Bs-ˉBs mixing where the standard model（SM） contributions overwhelm that of the new physics beyond standard model（BSM）, a measured relatively large D0-ˉD0mixing where the SM contribution is negligible, definitely implies the existence of the new physics BSM. It is natural to consider that the rare decays of D meson might be more sensitive to new physics, and the decay mode D0→μ＋μ-could be an ideal area to search for new physics because it is a flavor changing process. In this work we look for a trace of the new physics BSM in the leptonic decays of D0. Concretely we discuss the contributions of unparticle or an extra gauge boson Z while imposing the constraints set by fitting the D0-ˉD0mixing data. We find that the long-distance SM effects for D0→lˉl still exceed those contributions of the BSM under consideration, but for a double-flavor changing process such as D0→μ±e, the new physics contribution would be significant.     

低取代度两亲性β-环糊精及其水相中纳米球的制备

将2-O-(2-羟丙基)-β-环糊精与十二烷基、十四烷基、十六烷基和十八烷基缩水甘油醚在吡啶中反应,合成了4个低取代度的两亲性β-环糊精衍生物(平均取代度分别为1.87、1.95、2.14和1.80)。 将上述4个化合物分散于水中自组装成可稳定2~3周的纳米球,并且均呈现出较好的分散度和均匀性。     

运动声源的多普勒效应——第22届亚洲物理奥林匹克竞赛实验试题第二题介绍与解析

第22届亚洲物理奥林匹克竞赛实验试题共两道，其中第二道是声学黑匣子。该题目是一道虚拟实验题目，在二维平面上通过探测器对于运动声源的频率信号探测，判断声源的初始位置以及相关运动学参数等。该题目设计新颖，解法巧妙，综合了声波的传播与测量、声学多普勒效应等相关知识。在疫情形势下，非常适合物理专业学生进行线上虚拟实验学习。本文详细介绍了竞赛试题的内容，并给出试题的分析和解答。     

Experimental sensitivity on searching for CP violation at BES-III

The CP violation in the D system is predicted to be an unobserved level in the Standard Model. In this paper, we describe the method of searching for CP violation decay processes with the coherently produced D00 mesons from the ψ(3770) decay. The CP violation decay processes can be searched for at the BES-III experiment. The experimental sensitivity for searching for the CP violation can reach about a 10-4 level with a ψ(3770) data sample of about 20 fb-1.     

Discussion on Cross Section Measurement for D^-D Production around ψ（3770）

We give a brief discussion on the measurement of the cross section for D^-D production around the ψ（3770） resonance, and point out a new calculation of the cross sections based on the absolute measurements. Compared with single tag and double tag analyses, the new calculation provides us with many more opportunities to perform the cross section measurement.     

Searching for new physics in D0→μ+μ-, e+e-,μ±e干 at BES and/or the super charm-tau factory

In contrast with B⁰-B⁰, B_s-B_s mixing where the standard model (SM) contributions overwhelm that of the new physics beyond standard model (BSM), a measured relatively large D⁰-D⁰ mixing where the SM contribution is negligible, definitely implies the existence of the new physics BSM. It is natural to consider that the rare decays of D meson might be more sensitive to new physics, and the decay mode D⁰→μ⁺μ^- could be an ideal area to search for new physics because it is a flavor changing process. In this work we look for a trace of the new physics BSM in the leptonic decays of D⁰. Concretely we discuss the contributions of unparticle or an extra gauge boson Z' while imposing the constraints set by fitting the D⁰- D⁰ mixing data. We find that the long-distance SM effects for D⁰→l1 still exceed those contributions of the BSM under consideration, but for a double-flavor changing process such as D⁰→μ^±e⁺, the new physics contribution would be significant.     

Limits on light WIMPs with a 1 kg-scale germanium detector at 160 eVee physics threshold at the China Jinping Underground Laboratory

We report results of a search for light weakly interacting massive particle(WIMP) dark matter from the CDEX-1 experiment at the China Jinping Underground Laboratory(CJPL). Constraints on WIMP-nucleon spin-independent(SI) and spin-dependent(SD) couplings are derived with a physics threshold of 160 eVee, from an exposure of 737.1 kg-days. The SI and SD limits extend the lower reach of light WIMPs to 2 GeV and improve over our earlier bounds at WIMP mass less than 6 GeV.     

Experimental Sensitivities on Searching for Rare and Forbidden Decays of Charm Mesons at BES-Ⅲ

We discuss the Monte Carlo studies of searching for the rare and forbidden pure-leptonic and semi-leptonic decays of D^＋,0 and Ds^＋ mesons, based on a full Monte Carlo simulation for the BES-Ⅲ detector, with the BES-Ⅲ Ofttine Software System. The experimental sensitivities of searching for 36 rare and forbidden charm meson decays are estimated.     

Testing lepton flavor universality in terms of BESⅢ and charm-tau factory data

The recent measurements on R_K and R_π imply that there exists a possible violation of the leptonic flavor universality which is one of the cornerstones of the Standard Model. It is suggested that a mixing between sterile and active neutrinos might induce such a violation. In this work we consider the scenarios with one or two sterile neutrinos to explicitly realize the data while the constraints from the available experiments have been taken into account. Moreover, as indicated in literature, the deviation of the real PMNS matrix from the symmetric patterns may be due to a μ-τ asymmetry, therefore the measurements on R_D(Ds)eμ=Γ(D(D_s)→ e⁺ν_e)/Γ(D(D_s)→ μ⁺ν_μ) and R_D(Ds)μτ=Γ(D(D_s)→ μ⁺ν_μ)/Γ(D(D_s)→ τ⁺ν_τ) (and for some other heavy mesons B^± and B_c etc.) may shed more light on the physics responsible for the violation of the leptonic flavor universality. The data of BESⅢ are available to test the universality and that of future charm-tau factories will provide more accurate information. In this work, we will discuss R_D(Ds)eμ and R_D(Ds)μτ in detail and also briefly consider the cases for B^± and B_c.     

Searching for new physics in D~0→μ~+ μ~-,e~+e~-,μ~±e~■ at BES and/or the super charm-tau factory

In contrast with B0-ˉB0, Bs-ˉBs mixing where the standard model(SM) contributions overwhelm that of the new physics beyond standard model(BSM), a measured relatively large D0-ˉD0mixing where the SM contribution is negligible, definitely implies the existence of the new physics BSM. It is natural to consider that the rare decays of D meson might be more sensitive to new physics, and the decay mode D0→μ+μ-could be an ideal area to search for new physics because it is a flavor changing process. In this work we look for a trace of the new physics BSM in the leptonic decays of D0. Concretely we discuss the contributions of unparticle or an extra gauge boson Z while imposing the constraints set by fitting the D0-ˉD0mixing data. We find that the long-distance SM effects for D0→lˉl still exceed those contributions of the BSM under consideration, but for a double-flavor changing process such as D0→μ±e, the new physics contribution would be significant.