Direct detection of fermion dark matter in the radiative seesaw model

We consider the scenario in the radiative seesaw model where the dark matter particle is the lightest $Z_2$-odd fermion. We identify the regions of the parameter space of the model compatible with neutrino oscillation data, with the upper limits from rare charged lepton decays and with the observed dark matter abundance via thermal freeze-out, and we compute the dark matter scattering cross section with nuclei via the one-loop exchange of a photon, a $Z^0$-boson or a Higgs boson. We find that the predicted spin-independent cross section lies below the current LUX limit, although, for some choices of parameters, above the expected sensitivity of XENON1T or LZ.Comment: 22 pages, 4 figure

PAMELA's cosmic positron from decaying LSP in SO(10) SUSY GUT

We propose two viable scenarios explaining the recent observations on cosmic positron excess. In both scenarios, the present relic density in the Universe is assumed to be still supported by thermally produced WIMP or LSP (\chi). One of the scenarios is based on two dark matter (DM) components (\chi,X) scenario, and the other is on SO(10) SUSY GUT. In the two DM components scenario, extremely small amount of non-thermally produced meta-stable DM component [O(10^{-10}) < n_X /n_\chi] explains the cosmic positron excess. In the SO(10) model, extremely small R-parity violation for LSP decay to e^\pm is naturally achieved with a non-zero VEV of the superpartner of one right-handed neutrino (\tilde{\nu}^c) and a global symmetry.Comment: 6 pages, Talks presented in PASCOS, SUSY, and COSMO/CosPA in 201

Validity of the N\'{e}el-Arrhenius model for highly anisotropic Co_xFe_{3-x}O_4 nanoparticles

We report a systematic study on the structural and magnetic properties of Co_{x}Fe_{3-x}O_{4} magnetic nanoparticles with sizes between $5$ to $25$ nm, prepared by thermal decomposition of Fe(acac)_{3} and Co(acac)_{2}. The large magneto-crystalline anisotropy of the synthesized particles resulted in high blocking temperatures ($42$ K \leqq $T_B$ $\leqq 345$ K for $5 \leqq$ d $\leqq 13$ nm ) and large coercive fields ($H_C \approxeq 1600$ kA/m for $T = 5$ K). The smallest particles ($=5$ nm) revealed the existence of a magnetically hard, spin-disordered surface. The thermal dependence of static and dynamic magnetic properties of the whole series of samples could be explained within the N\'{e}el-Arrhenius relaxation framework without the need of ad-hoc corrections, by including the thermal dependence of the magnetocrystalline anisotropy constant $K_1(T)$ through the empirical Br\"{u}khatov-Kirensky relation. This approach provided $K_1(0)$ values very similar to the bulk material from either static or dynamic magnetic measurements, as well as realistic values for the response times ($\tau_0 \simeq 10^{-10}$ s). Deviations from the bulk anisotropy values found for the smallest particles could be qualitatively explained based on Zener\'{}s relation between $K_1(T)$ and M(T)

Higgs Decays in the Low Scale Type I See-Saw Model

The couplings of the low scale type I see-saw model are severely constrained by the requirement of reproducing the correct neutrino mass and mixing parameters, by the non-observation of lepton number and charged lepton flavour violating processes and by electroweak precision data. We show that all these constraints still allow for the possibility of an exotic Higgs decay channel into a light neutrino and a heavy neutrino with a sizable branching ratio. We also estimate the prospects to observe this decay at the LHC and discuss its complementarity to the indirect probes of the low scale type I see-saw model from experiments searching for the $\mu\to e\gamma$ decay.Comment: 15 pages, 8 figures; references added and results unchanged; matched with the published version on PL

Dedicated Section: The Fifth International Seagrass Biology Workshop, 7-11 October 2002, Ensenada, Baja California, Mexico

Since 1996, seagrass experts have been meeting biennially to share knowledge of the biology of seagrasses and the animals associated with seagrass meadows. Previous workshops have taken place in Western Australia, Japan, the Philippines, and France. In 2002, the meeting was held in Mexico and four themes were chosen for the sessions: Ecophysiological Processes (Sven Beer, Chair), Plant-Animal Interactions (Kenneth L. HeckJR., Chair), Genetics and Reproductive Biology (Gabriele Procaccini and Michelle Wycott, Co-Chairs), and Changes in Seagrass Beds at the Local and Regional Scale (Fred T. Short, Chair). An additional session on Traditional Knowledge and Wisdom (Sandy Wyllie-Echeverria, Chair) provided an ethnobotanical perspective. Included here are abstracts accepted for the workshop, either as oral or poster presentations

Small steps towards Grand Unification and the electron/positron excesses in cosmic-ray experiments

We consider a small extension of the standard model by adding two Majorana fermions; those are adjoint representations of the SU(2)_L and SU(3)_c gauge groups of the standard model. In this extension, the gauge coupling unification at an energy scale higher than 10^{15} GeV is realized when the masses of the triplet and the octet fermions are smaller than 10^4 GeV and 10^{12} GeV, respectively. We also show that an appropriate symmetry ensures a long lifetime of the neutral component of the triplet fermion whose thermal relic density naturally explains the observed dark matter density. The electron/positron excesses observed in recent cosmic-ray experiments can be also explained by the decay of the triplet fermion.Comment: 11 pages, 5 figure

Challenging the gendered rhetoric of success? The limitations of women-only mentoring for tackling gender inequality in the workplace

Mentoring is widely acknowledged to be an important contributor to women’s career success and progression but women often struggle to access mentoring networks that can help sponsor and develop their careers. Formal mentoring programmes designed specifically for women help overcome this challenge, but such schemes may at the same time reinforce masculine discourses which position women as deficient in relation to the invisibly male norm that is implicit within contemporary working practices. Drawing on a formal women-only mentoring programme built on gender-positive goals to empower women to ‘be the best they can be’ within the events industry, this paper considers the extent to which such programmes can both challenge and reproduce gendered discourses of business and success. Interviews with mentors and mentees illustrate how such programmes make gender visible within business and individual careers, but masculinist underpinnings of organisational discourses remain invisible, unacknowledged and thus largely unchallenged