Multi-Scalar-Singlet Extension of the Standard Model - the Case for Dark Matter and an Invisible Higgs Boson

We consider a simple extension of the Standard Model by the addition of N real scalar gauge singlets \vp that are candidates for Dark Matter. By collecting theoretical and experimental constraints we determine the space of allowed parameters of the model. The possibility of ameliorating the little hierarchy problem within the multi-singlet model is discussed. The Spergel-Steinhardt solution of the Dark Matter density cusp problem is revisited. It is shown that fitting the recent CRESST-II data for Dark Matter nucleus scattering implies that the standard Higgs boson decays predominantly into pairs of Dark Matter scalars. It that case discovery of the Higgs boson at LHC and Tevatron is impossible. The most likely mass of the dark scalars is in the range 15 GeV \lsim \mvp \lsim 50 GeV with BR(h \to \vp\vp) up to 96%.Comment: 18 pages, 15 figure

The Real Gauge Singlet Scalar Extension of Standard Model: A Possible Candidate of Cold Dark Matter

We consider a simplest extension of Standard Model in which a real SM gauge singlet scalar with an additional discrete symmetry $Z_2$ is introduced to SM. This additional scalar can be a viable candidate of cold dark matter since the stability of $S$ is achieved by the application of $Z_2$ symmetry on $S$. Considering $S$ as a possible candidate of cold dark matter we have solved Boltzmann's equation to find the freeze out temperature and relic density of $S$ for Higgs mass 120 GeV in the scalar mass range 5 GeV to 1 TeV. As $HHSS$ coupling $\delta_2$ appearing in Lagrangian depends upon the value of scalar mass $m_S$ and Higgs mass $m_h$, we have constrained the $m_S - \delta_2$ parameter space by using the WMAP limit on the relic density of dark matter in the universe and the results of recent ongoing dark matter direct search experiments namely CDMS-II, CoGeNT, DAMA, EDELWEISS-II, XENON-10, XENON-100. From such analysis we find two distinct mass regions (a lower and higher mass domain) for such a dark matter candidate that satisfy both the WMAP limit and the experimental results considered here. We have estimated the possible differential direct detection rates and annual variation of total detection rates for this scalar dark matter candidate $S$ for two detector materials namely Ge, Xe. Finally we have calculated the $\gamma-$ray flux from the galactic centre due to annihilation of two 130 GeV scalar dark matter into two monoenergetic $\gamma-$rays.Comment: 21 pages, New calculations, figures and references adde

Effective Dark Matter Model: Relic density, CDMS II, Fermi LAT and LHC

The Cryogenic Dark Matter Search recently announced the observation of two signal events with a 77% confidence level. Although statistically inconclusive, it is nevertheless suggestive. In this work we present a model-independent analysis on the implication of a positive signal in dark matter scattering off nuclei. Assuming the interaction between (scalar, fermion or vector) dark matter and the standard model induced by unknown new physics at the scale $\Lambda$, we examine various dimension-6 tree-level induced operators and constrain them using the current experimental data, e.g. the WMAP data of the relic abundance, CDMS II direct detection of the spin-independent scattering, and indirect detection data (Fermi LAT cosmic gamma-ray), etc. Finally, the LHC reach is also explored

Leishmaniose cutânea experimental: I - sobre a susceptibilidade do primata Cebus apella (Cebidae) a infecção pela Leishmania (Viannia) lainsoni Silveira, Shaw, Braga e Ishikawa, 1987

Foi investigada a susceptibilidade do primata Cebus apella (Cebidae) à infecção experimental pela Leishmaiua (Viannia) lainsoni, com o objetivo de estudara patogenia desse parasita, ainda pouco conhecido para o homem. Dessa forma, cinco espécimens jovens daquele primata, 2 machos e 3 fêmeas, foram inoculados, intraderme, em oito sítios diferentes da região dorsal da cauda com 3 x 10(6) de promastigotas do parasita (MHOMZBR/81/M6426, Benevides, Pará), obtidas de cultura da fase estacionária. Em seguida às inoculações, a infecção experimental nos animais foi comprovada, não só pela presença de amastigotas do parasita na pele dos animais inoculados, mas, também, pela concomitância desse achado associado ao desenvolvimento de lesão cutânea nos pontos da pele onde o parasita foi inoculado. Diante desses resultados, ficou demonstrada a susceptibilidade do primata Cebus apella à infecção experimental pela Leishmama lainsoni cujo período de infecção durou quase quatro meses, suficiente para testar drogas antileishmanióticas e estudar a patogênese da doença causada por este parasita.The susceptibility of the monkey Cebus apella (Cebidae) to experimental infection by Leishmania (Viannia) lainsoni has been investigated. For this purpose, five young monkeys, 2 males and 3 females, were intradermally, inoculated, in eight different places along the dorsal surface of the tail with 3 x 10(6) promastigotes of the parasite (MHOM/BR/81/M6426, Benevides, Pará), from stationary phase culture in Difco B45 medium. After inoculations, infection in the monkeys was indicated by the presence of amastigotes in the skin lesions produced in these animals at the points of inoculation, confirming the susceptibility of the monkey Cebus apella to experimental infection by Leishmania lainsoni, with an infection period of four months. This represents a suitable period for testing antileishmanial drugs or studying the pathogenesis of the disease caused by this parasite