864 research outputs found
Perspectives for the detection and measurement of Supersymmetry in the focus point region of mSUGRA models with the ATLAS detector at LHC
This paper discusses the ATLAS potential to study Supersymmetry for the
"Focus-Point" region of the parameter space of mSUGRA models. The potential to
discovery a deviation from Standard Model expectations with the first few
of LHC data was studied using the parametrized simulation of the
ATLAS detector. Several signatures were considered, involving hard jets, large
missing energy, and either -tagged jets, opposite-sign isolated electron or
muon pairs, or top quarks reconstructed exploiting their fully hadronic decays.
With only 1 of data each of these signatures may allow to observe
an excess of events over Standard Model expectation with a statistical
significance exceeding 5 standard deviations. An analytical expression was
derived for the shape of the distribution of the dilepton invariant mass
arising from the three-body leptonic decay of the neutralinos under the
hypothesis of heavy scalars, which is appropriate for the focus-point scenario.
The resulting function was used to fit the distribution of the dilepton
invariant mass obtained with simulated LHC data, and to extract the value of
two kinematic endpoints measuring the and
the mass differences. This information was
used to constrain the MSSM parameter space compatible with the data
Doping and temperature dependence of incommensurate antiferromagnetism in underdoped lanthanum cuprates
The doping, temperature and energy dependence of the dynamical spin structure
factors of the underdoped lanthanum cuprates in the normal state is studied
within the t-J model using the fermion-spin transformation technique.
Incommensurate peaks are found at ,
at relatively low temperatures with linearly
increasing with doping at the beginning and then saturating at higher dopings.
These peaks broaden and weaken in amplitude with temperature and energy, in
good agreement with experiments. The theory also predicts a rotation of these
peaks by at even higher temperatures, being shifted to .Comment: 11 pages, PDF file, six figures are included, accepted for
publication in Physical Review
CMB Power Spectrum from Noncommutative Spacetime
Very recent CMB data of WMAP offers an opportunity to test inflation models,
in particular, the running of spectral index is quite new and can be used to
rule out some models. We show that an noncommutative spacetime inflation model
gives a good explanation of these new results. In fitting the data, we also
obtain a relationship between the noncommutative parameter (string scale) and
the ending time of inflation.Comment: 8 pages, 2 figures; v2: refs. added and minor corrections; v3:
further minor correctio
WMAP constraint on the P-term inflationary model
In light of WMAP results, we examine the observational constraint on the
P-term inflation. With the tunable parameter , P-term inflation contains
richer physics than D-term and F-term inflationary models. We find the
logarithmic derivative spectral index with on large scales and on
small scales in agreement to observation. We obtained a reasonable range for
the choice of the gauge coupling constant in order to meet the requirements
of WMAP observation and the expected number of the e-foldings. Although tuning
and we can have larger values for the logarithmic derivative of the
spectral index, it is not possible to satisfy all observational requirements
for both, the spectral index and its logarithmic derivative at the same time.Comment: 6 pages, double column, 13 figures included. Version appearing in the
Physical Review
Geochronological and geochemical constraints on Late Cryogenian to Early Ediacaran magmatic rocks on the northern Tarim Craton:implications for tectonic setting and affinity with Gondwana
The Tarim Craton provides a geologic record of both the fragmentation of the Rodinian supercontinent and the subsequent assembly of Gondwana. However, the timing and interactions of these radically different tectonic processes remain contested. A critical part of this debate revolves around the Late Cryogenian-Ediacaran igneous rocks along the Craton’s northern margin, specifically, whether they record super-plume related Rodinian breakup or Gondwanan orogeny. To address this issue, we present zircon U-Pb-Hf isotopic data and whole rock geochemistry from Late Cryogenian to Early Ediacaran granitoids of the northern Tarim Craton. U-Pb zircon ages reveal three magmatic periods along the northern Tarim margin: ca. 660–640 Ma, 635–625 Ma and 620–600 Ma, associated with small scale felsic and mafic magmas. These granitoids have an A2-type affinity and are enriched in alkalines, but are depleted in Nb, Ta, Sr, P and Ti. Elemental data and generally negative εHf(t) values (−13.96 to 1.65) suggest that they were mainly derived from partial melting of enriched, subduction-modified lithospheric mantle triggered by upwelling of the asthenospheric mantle along the active continental margin of northern Tarim. We suggest that the Tarim Craton travelled as an isolated plate for much of the Late Neoproterozoic, near the outer part of Rodinia and subsequently Gondwana. During this time it was affected by localized and periodic subduction-related intrusion and eruption. However, within the samples of this study, there is no U-Pb-Hf isotopic and whole-rock geochemical evidence to support either super-plume-related rifting (i.e. Rodinian breakup) or Pan-African orogeny (i.e. Gondwanan assembly).</p
The fermion dynamical symmetry model for the even--even and even--odd nuclei in the Xe--Ba region
The even--even and even--odd nuclei Xe-Xe and
Ba-Ba are shown to have a well-realized fermion dynamical symmetry. Their low-lying energy levels can be
described by a unified analytical expression with two (three) adjustable
parameters for even--odd (even--even) nuclei that is derived from the fermion
dynamical symmetry model. Analytical expressions are given for wavefunctions
and for transition rates that agree well with data. The distinction
between the FDSM and IBM limits is discussed. The experimentally
observed suppression of the the energy levels with increasing quantum
number can be explained as a perturbation of the pairing interaction on
the symmetry, which leads to an Pairing effect for nuclei.Comment: submitted to Phys. Rev. C, LaTeX, 31 pages, 8 figures with postscript
files available on request at [email protected]
Power-law entropy-corrected HDE and NADE in Brans-Dicke cosmology
Considering the power-law corrections to the black hole entropy, which appear
in dealing with the entanglement of quantum fields inside and outside the
horizon, the holographic energy density is modified accordingly. In this paper
we study the power-law entropy-corrected holographic dark energy in the
framework of Brans-Dicke theory. We investigate the cosmological implications
of this model in detail. We also perform the study for the new agegraphic dark
energy model and calculate some relevant cosmological parameters and their
evolution. {As a result we find that this model can provide the present cosmic
acceleration and even the equation of state parameter of this model can cross
the phantom line provided the model parameters are chosen suitably}.Comment: 14 pages, 2 figure, accepted by IJT
- …