Long life stau in the minimal supersymmetric standard model

We study the stau lifetime in a scenario with the LSP taken to be a neutralino and the NLSP being a stau, based on the minimal supersymmetric Standard Model. The mass difference between the LSP and NLSP, $\delta m$, must satisfy $\delta m/m_{\tilde{\chi}} \sim$ a few % or less for coannihilation to occur, where $m_{\tilde{\chi}}$ is the neutralino mass. We calculate the stau lifetime from the decay modes $\tilde{\tau}\to \tilde{\chi}\tau$, $\tilde{\chi}\nu_\tau\pi$, and $\tilde{\chi}\nu_\tau\mu(e)\nu_{\mu(e)}$ and discuss its dependence on various parameters. We find that the lifetime is in the range $10^{-22}$--$10^{16}$ sec for $10^{-2} \le \delta m \le 10$ GeV. We also discuss the connection with lepton flavor violation if there is mixing between sleptons.Comment: 15 pages, 5 figure

Constraints from Unrealistic Vacua in Supersymmetric Standard Model with Neutrino Mass Operators

We analyze a scalar potential of the minimal supersymmetric standard model (MSSM) with neutrino mass operators along Unbounded-From-Below (UFB) and Color and/or Charged Breaking (CCB) directions. We show necessary conditions to avoid the potential minima which can be deeper than the realistic vacuum. These conditions would constrain more strongly than conditions in the MSSM without taking into account neutrino mass operators, and can improve the predictive power of supersymmetric models with neutrino mass operators.Comment: 11 pages, 4 figure

On the Logarithmic Asymptotics of the Sixth Painleve' Equation (Summer 2007)

We study the solutions of the sixth Painlev\'e equation with a logarithmic asymptotic behavior at a critical point. We compute the monodromy group associated to the solutions by the method of monodromy preserving deformations and we characterize the asymptotic behavior in terms of the monodromy itself.Comment: LaTeX with 8 figure

Non-ideal behavior of intramolecular structure factor of dilute polymers in a theta solvent

We study the configurational properties of single polymers in a theta solvent by Monte Carlo simulation of the bond fluctuation model. The intramolecular structure factor at the theta point is found to be distinctively different from that of the ideal chain. The structure factor shows a hump around $q\sim 5/R_g$ and a dip around $q\sim 10/R_g$ in the Kratky plot with $R_g$ being the radius of gyration. This feature is apparently similar to that in a melt. The theoretical expression by the simple perturbation expansion to the first order in terms of the Mayer function can be fitted to the obtained structure factor quite well, but the second virial coefficient cannot be set to zero.Comment: 8 pages, 7figure

Possible solution to the 7^7Li problem by the long lived stau

Modification of standard big-bang nucleosynthesis is considered in the minimal supersymmetric standard model to resolve the excessive theoretical prediction of the abundance of primordial lithium 7. We focus on the stau as a next-lightest superparticle, which is long lived due to its small mass difference with the lightest superparticle. It provides a number of additional decay processes of $\mathrm{^{7}Li}$ and $\mathrm{^{7}Be}$. A particularly important process is the internal conversion in the stau-nucleus bound state, which destroys the $\mathrm{^{7}Li}$ and $\mathrm{^{7}Be}$ effectively. We show that the modification can lead to a prediction consistent with the observed abundance of $\mathrm{^{7}Li}$.Comment: 6 pages, 5 figure

Nanoscale anisotropic structural correlations in the paramagnetic and ferromagnetic phases of Nd0.5Sr0.5 MnO3

We report x-ray scattering studies of short-range structural correlations and diffuse scattering in Nd0.5Sr0.5MnO3. On cooling, this material undergoes a series of transitions, first from a paramagnetic insulating (PI) to a ferromagnetic metallic (FM) phase, and then to a charge-ordered (CO) insulating state. Highly anisotropic structural correlations were found in both the PI and FM states. The correlations increase with decreasing temperature, reaching a maximum at the CO transition temperature. Below this temperature, they abruptly collapsed. Single-polaron diffuse scattering was also observed in both the PI and FM states suggesting that substantial local lattice distortions are present in these phases. We argue that our measurements indicate that nanoscale regions exhibiting layered orbital order exist in the paramagnetic and ferromagnetic phases of Nd0.5Sr0.5MnO3.Comment: 5 pages, 4 embedded figure

Kerangka kemahiran employability senibina graduan politeknik

Sehingga tahun 2014, hampir seratus peratus graduan diploma politeknik Malaysia diterima bekerja di pasaran pekerjaan Malaysia. Namun begitu, terdapat peningkatan tren pengangguran dalam kalangan graduan diploma senibina politeknik sejak tahun 2012. Salah satu punca kepada peningkatan jumlah pengangguran ini disebabkan oleh ketidak selarian antara kemahiran employability yang diperlukan oleh graduan senibina dan pihak firma binaan. Penekanan terhadap kemahiran employability yang bertepatan mengikut bidang penting dalam membantu graduan memahami dan mengaplikasikan kemahiran tersebut di alam pekerjaan. Kajian ini dijalankan bertujuan untuk menghasilkan kerangka kemahiran Employability Senibina (Ar–ES) bagi graduan diploma senibina politeknik yang memenuhi keperluan pihak firma binaan. Kajian ini turut bertujuan untuk mengenal pasti konstruk dan dimensi Ar–ES yang dominan diperlukan responden kajian. Kaedah gabungan penerokaan digunakan melibatkan sampel seramai 285 orang graduan diploma senibina politeknik dan 226 orang responden mewakili majikan firma binaan yang terdapat di Malaysia. Analisis data mendapati lima konstruk dan tujuh belas dimensi Ar–ES telah dikenal pasti. Konstruk etika profesional merupakan konstruk paling dominan diperlukan oleh graduan (logit= -0.19) dan pihak majikan (logit= -0.17). Hasil analisis Differential Group Functioning (DGF) mendapati tidak terdapat perbezaan yang signifikan antara graduan senibina dan pihak majikan bagi kesemua konstruk dan dimensi kerangka Ar–ES yang dominan diperlukan. Pengkaji turut mendapati bahawa kerangka Ar–ES yang diuji bersifat unidimensi dan disahkan secara empirikal dengan memenuhi kriteria analisis Principle Component Analysis (PCA). Di akhir kajian, pengkaji telah menghasilkan kerangka Ar–ES untuk graduan politeknik bagi memenuhi kehendak firma binaan Malaysia. Penghasilan kerangka ini diharap dapat membantu meningkatkan kebolehpasaran graduan diploma senibina di Malaysia dan menangani isu pengangguran dalam kalangan mereka