Earthquake forecast via neutrino tomography

We discuss the possibility of forecasting earthquakes by means of (anti)neutrino tomography. Antineutrinos emitted from reactors are used as a probe. As the antineutrinos traverse through a region prone to earthquakes, observable variations in the matter effect on the antineutrino oscillation would provide a tomography of the vicinity of the region. In this preliminary work, we adopt a simplified model for the geometrical profile and matter density in a fault zone. We calculate the survival probability of electron antineutrinos for cases without and with an anomalous accumulation of electrons which can be considered as a clear signal of the coming earthquake, at the geological region with a fault zone, and find that the variation may reach as much as 3% for ν_e emitted from a reactor. The case for a ν_e beam from a neutrino factory is also investigated, and it is noted that, because of the typically high energy associated with such neutrinos, the oscillation length is too large and the resultant variation is not practically observable. Our conclusion is that with the present reactor facilities and detection techniques, it is still a difficult task to make an earthquake forecast using such a scheme, though it seems to be possible from a theoretical point of view while ignoring some uncertainties. However, with the development of the geology, especially the knowledge about the fault zone, and with the improvement of the detection techniques, etc., there is hope that a medium-term earthquake forecast would be feasible.     

Effects of nuclear deformation on the form factor for direct dark matter detection

For the detection of direct dark matter, in order to extract useful information about the fundamental interactions from the data, it is crucial to properly determine the nuclear form factor. The form factor for the spin-independent cross section of collisions between dark matter particles and the nucleus has been thoroughly studied by many authors. When the analysis was carried out, the nuclei were always supposed to be spherically symmetric. In this work, we investigate the effects of the deformation of nuclei from a spherical shape to an elliptical one on the form factor. Our results indicate that as long as the ellipticity is not too large, such deformation will not cause any substantial effects. In particular, when the nuclei are randomly orientated in room-temperature circumstances, one can completely neglect them.     

N巴黎势和可能的p共振态(英文)

通过求解N巴黎光学势的复薛定谔方程,研究了N系统的近阈束缚和共振行为,得到了一个p系统的13P0共振态.发现其能量和宽度与最近BES用Breit Wigner(B W)公式分析J/ψ→γp衰变的实验数据给出的结果相容.讨论了这一结果的含义及进一步研究的建议.     

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.     

序

2001年第一届“粒子物理，核物理及宇宙学交叉学科前沿问题研究会”文集     

利用具有两个Higgs-doublets的扩展标准模型对LEPⅡ能量下tc产生过程的研究

在标准模型和两个Higgs二重态以及包括第四代费米子的扩充中计算了用正负电子对撞出tc(或tc),即e⁺e^－→(or tc)产生截面.结果表明即使顶夸克质量如模型预言的有140GeV左右,只要在此扩充中取最有利的参数时甚至在LEPⅡ中这一过程亦是可观测的.     

采用多元化的教学手段,提高物理人才的综合素质——南开大学物理学基础科学人才培养基地建设经验介绍

介绍了南开大学国家物理学基础科学研究人才培养基地在十多年的建设中,通过多元化的教学手段提高学生的学习自主性,通过加强科研训练提高物理人才综合素质的经验和取得的成果.     

线性σ-模型和在J/ψ→γpp的pp质量谱中观测到的增强现象

假定BES合作组在辐射衰变J/ψ→γ pp中观测到的pp,谱的增强是由于存在一个pp的分子态,用线性σ-模型计算了它的束缚能和寿命. 具体考虑了这种增强现象是由于pp可能形成一个S-波或P-波共振态, 并把计算结果和实验数据做了比较. 与氘核不同, 由于pp可以通过s-道湮没, 因此通过研究它的总宽度可以获得线性σ-模型及其相关问题的信息.     

在ILC上用γγ→Z过程检验非对易时空标度

讨论关于在ILC用γγ到Z过程检验非对易时空能标(原文发在hep-ph/0604115). 在通常时空量子场论中, 由杨氏定理可知一个自旋为1的粒子不可能衰变为两个光子. 但在非对易时空中此过程是允许的. 因此这个过程能作为检验非对易时空的工具. ILC的光子对撞模式能实现这个过程. 如果总亮度能达到500fb^－1, 我们证明对Gamma (Z to gamma gamma)宽度的测量精度将比现有限制(<5.2×10^－5GeV)好3—4个数量级. 对非对易时空能标的检测可高达几个TeV.     

培养学生的兴趣、独立性、自主性与素质教育

30年前,甚至十几年前物理系还是一个众生向往的殿堂,那些决心献身科学并且品学兼优的佼佼者进入到这个领域,从而受到同龄人的尊敬和羡慕.一代优秀的物理学工作者就是在这个环境中成长起来,成为今天物理科研与教学领域的中坚力量.然而随着时代的发展,社会的需求,职业市场的选择以及人们价值观的改变,部分优秀的中学毕业生选择了更现实的领域,如经济、计算机等,他们毕业后可以较轻松地获得工作条件优越,报酬丰厚的职业.因而大量的人才从物理学,特别是纯物理学领域中流失了.这些年再加上出国留学热,甚至在高中毕业就已走上出国之路,对我们人才培养的冲击之大是难以估计的.物理学在许多学生及家长眼中已沦为第二等的学科,或是不得已的选择.