19,092 research outputs found
The CDF dijet excess and Z'_{cs} coupled to the second generation quarks
Recently the CDF collaboration has reported the excess in the dijet
invariant-mass distribution of the Wjj events, corresponding to a significance
of 3.2 standard deviations. Considering the lack of similar excesses in the
and events yet, we propose a new Z' model: Z' couples only
to the second generation quarks. Single production of \zsc as well as
associated production with are mainly from the sea quarks. Only
production has additional contribution from one valence quark and one
sea quark, which is allowed by CKM mixing. We found that if the new gauge
coupling is large enough, marginally permitted by perturbativity, this new
model can explain the observed CDF anomaly as well as the lack of \gm
jj and anomalies. Vanishing coupling of Z'-b-b protects this model from
the constraint of p pbar ->WH -> l\nu b \bar{b}.Comment: references adde
The Octonions
The octonions are the largest of the four normed division algebras. While
somewhat neglected due to their nonassociativity, they stand at the crossroads
of many interesting fields of mathematics. Here we describe them and their
relation to Clifford algebras and spinors, Bott periodicity, projective and
Lorentzian geometry, Jordan algebras, and the exceptional Lie groups. We also
touch upon their applications in quantum logic, special relativity and
supersymmetry.Comment: 56 pages LaTeX, 11 Postscript Figures, some small correction
A Study on GPS Data Tracking Method for KOMPSAT Spacecraft Orbit Control
The Global Positioning System (GPS) is becoming more attractive navigation means for LEO spacecraft due to the data accuracy and convenience for utilization. The anomalies such as serious variations of Dilution-Of-Precision (DOP), loss of infrequent 3-dimensional position fix, and deterioration of instantaneous accuracy of position and velocity data could be observed, which have not been appeared during the ground testing. It may cause lots of difficulty for the processing of the orbit control algorithm using the GPS data. In this paper, the characteristics of the GPS data were analyzed according to the configuration of GPS receiver such as position fix algorithm and mask angle using GPS navigation data obtained from the first Korea Multi-Purpose Satellite (KOMPSAT). The problem in orbit tracking using GPS data, including the infrequent deterioration of the accuracy, and an efficient algorithm for its countermeasures has also been introduced. The reliability and efficiency of the modified algorithm were verified by analyzing the effect of the results between algorithm simulation using KOMPSAT flight data and ground simulator
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