6,154 research outputs found
SUSY-QCD Corrections to Associated Production at the CERN Large Hadron Collider
We calculate the SUSY-QCD corrections to the inclusive total cross sections
of the associated production processes in the Minimal
Supersymmetric Standard Model(MSSM) at the CERN Large Hadron Collider(LHC). The
SUSY-QCD corrections can increase and decrease the total cross sections
depending on the choice of the SUSY parameters. When the SUSY-QCD
corrections increase the leading-order (LO) total cross sections significantly
for large tan (), which can exceed 10% and have the opposite
sign with respect to the QCD and the SUSY-EW corrections, and thus cancel with
them to some extent. Moreover, we also investigate the effects of the SUSY-QCD
on the differential distribution of cross sections in transverse momentum
and rapidity Y of W-boson, and the invariant mass .Comment: 24 pages, 10 figures; minor changes in references; two figures and
the corresponding disccusions added; a version to appear in PR
Proton-Antiproton Annihilation in Baryonium
A possible interpretation of the near-threshold enhancement in the
-mass spectrum in is the of existence
of a narrow baryonium resonance X(1860). Mesonic decays of the
-bound state X(1860) due to the nucleon-antinucleon annihilation
are investigated in this paper. Mesonic coherent states with fixed -parity
and -parity have been constructed . The Amado-Cannata-Dedoder-Locher-Shao
formulation(Phys Rev Lett. {\bf 72}, 970 (1994)) is extended to the decays of
the X(1860). By this method, the branch-fraction ratios of , and are calculated. It is shown
that if the X(1860) is a bound state of , the decay channel ( is favored over . In this way, we develop
criteria for distinguishing the baryonium interpretation for the near-threshold
enhancement effects in -mass spectrum in from other possibilities. Experimental checks are expected. An intuitive
picture for our results is discussed.Comment: 19 pages, 3 figure
Origins of ferromagnetism in transition-metal doped Si
We present results of the magnetic, structural and chemical characterizations of Mn<sup>+</sup>-implanted Si displaying <i>n</i>-type semiconducting behavior and ferromagnetic ordering with Curie temperature,T<sub>C</sub> well above room temperature. The temperature-dependent magnetization measured by superconducting quantum device interference (SQUID) from 5 K to 800 K was characterized by three different critical temperatures (T*<sub>C</sub>~45 K, T<sub>C1</sub>~630-650 K and T<sub>C2</sub>~805-825 K). Their origins were investigated using dynamic secondary mass ion spectroscopy (SIMS) and transmission electron microscopy (TEM) techniques, including electron energy loss spectroscopy (EELS), Z-contrast STEM (scanning TEM) imaging and electron diffraction. We provided direct evidences of the presence of a small amount of Fe and Cr impurities which were unintentionally doped into the samples together with the Mn<sup>+</sup> ions, as well as the formation of Mn-rich precipitates embedded in a Mn-poor matrix. The observed T*<sub>C</sub> is attributed to the Mn<sub>4</sub>Si<sub>7</sub> precipitates identified by electron diffraction. Possible origins of and are also discussed. Our findings raise questions regarding the origin of the high ferromagnetism reported in many material systems without a careful chemical analysis
Threshold Resummation Effects in the Associated Production of Chargino and Neutralino at Hadron Colliders
We investigate the QCD effects in the associated production of the chargino
and the neutralino, and , in the Minimal
Supersymmetric Standard Model (MSSM) at both the Fermilab Tevatron and the CERN
Large Hadron Collider (LHC). We include the next-to-leading order (NLO) QCD
corrections (including supersymmetric QCD) and the threshold resummation
effects. Our results show that, compared to the NLO predictions, the threshold
resummation effects can increase the total cross sections by 3.6% and 3.9% for
the associated production of and
at the LHC, respectively, and by 4.7% for
those of at the Tevatron. In the invariant
mass distributions the resummation effects are significant for large invariant
mass. The threshold resummation reduces the dependence of the total cross
sections at the LHC (Tevatron) on the renormalization/factorization scales to
5% (4%) from up to 7% (11%) at NLO.Comment: revised version with midifications, several references adde
Alternate proof of the Rowe-Rosensteel proposition and seniority conservation
For a system with three identical nucleons in a single- shell, the states
can be written as the angular momentum coupling of a nucleon pair and the odd
nucleon. The overlaps between these non-orthonormal states form a matrix which
coincides with the one derived by Rowe and Rosensteel [Phys. Rev. Lett. {\bf
87}, 172501 (2001)]. The propositions they state are related to the eigenvalue
problems of the matrix and dimensions of the associated subspaces. In this
work, the propositions will be proven from the symmetric properties of the
symbols. Algebraic expressions for the dimension of the states, eigenenergies
as well as conditions for conservation of seniority can be derived from the
matrix.Comment: 9 pages, no figur
General Supersymmetric Solutions of Five-Dimensional Supergravity
The classification of 1/4-supersymmetric solutions of five dimensional gauged
supergravity coupled to arbitrary many abelian vector multiplets, which was
initiated in hep-th/0401129, is completed. The structure of all solutions for
which the Killing vector constructed from the Killing spinor is null is
investigated in both the gauged and the ungauged theories and some new
solutions are constructed.Comment: 24 pages, references added, uses JHEP3.cl
Green Gasification Technology for Wet Biomass
The world now is facing two energy related threats which are lack of sustainable, secure and affordable energy supplies and the environmental damage acquired in producing and consuming ever-increasing amount of energy. In the first decade of the twenty-first century, increasing energy prices reminds us that an affordable energy plays an important role in economic growth and human development. To overcome the abovementioned problem, we cannot continue much longer to consume finite reserves of fossil fuels, the use of which contributes to global warming. Preferably, the world should move towards more sustainable energy sources such as wind energy, solar energy and biomass. However, the abovementioned challenges may not be met solely by introduction of sustainable energy forms. We also need to use energy more efficiently. Developing and introducing more efficient energy conversion technologies is therefore important, for fossil fuels as well as renewable fuels. This assignment addresses the question how biomass may be used more efficiently and economically than it is being used today. Wider use of biomass, a clean and renewable feedstock may extend the lifetime of our fossil fuels resources and alleviate global warming problems. Another advantage of using of biomass as a source of energy is to make developed countries less interdependent on oil-exporting countries, and thereby reduce political tension. Furthermore, the economies of agricultural regions growing energy crops benefit as new jobs are created.Keywords: energy, gasification, sustainable, wet biomas
Top quark chromomagnetic dipole moment in the littlest Higgs model with T-parity
The littlest Higgs model with T-parity, which is called model, predicts
the existence of the new particles, such as heavy top quark, heavy gauge
bosons, and mirror fermions. We calculate the one-loop contributions of these
new particles to the top quark chromomagnetic dipole moment . We find that the contribution of the model is one order of magnitude
smaller than the standard model prediction value.Comment: latex files, 12 pages, 3 figure
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