1,569 research outputs found
The polarised gluon density from di-jet events in DIS at a polarised HERA
We present a possible direct measurement of the polarised gluon density
in LO from di-jet production in polarised deep inelastic ep
scattering, assuming the kinematics of the HERA collider. We show the
sensitivity to the x-dependence of and to the first moment in the range , assuming the electron and proton
beam of HERA being polarised to 70% and an integrated luminosity of at least
200 pb. We include in our study hadronisation and higher order effects,
as well as realistic detector smearing and acceptance. We find that the
statistical and systematic uncertainties are small enough to distinguish
between different parametrizations for , which all are in
accordance with present data. We stress that at HERA an x-range could be
measured, that is not accessible to any other present or proposed experiment.Comment: 15 pages, 9 figures, Contributed paper to the Proceedings of the
Workshop on Physics at HERA with Polarized Protons and Electron
An assessment of the potential contributions to oceanography from Skylab visual observations and hand-held photography
There are no author-identified significant results in this report
Space engine safety system
A rocket engine safety system was designed to initiate control procedures to minimize damage to the engine or vehicle or test stand in the event of an engine failure. The features and the implementation issues associated with rocket engine safety systems are discussed, as well as the specific concerns of safety systems applied to a space-based engine and long duration space missions. Examples of safety system features and architectures are given, based on recent safety monitoring investigations conducted for the Space Shuttle Main Engine and for future liquid rocket engines. Also, the general design and implementation process for rocket engine safety systems is presented
The development of power specific redlines for SSME safety monitoring
Over the past several years, there has been an increased awareness in the necessity for rocket engine health monitoring because of the cost and complexity of present and future systems. A current rocket engine system, the Space Shuttle Main Engine (SSME), combines a limited redline system with closed-loop control of the engine's thrust level and mixture ratio. Despite these features, 27 tests of the SSME have resulted in major incidents. A SSME transient model was used to examine the effect of variations in high pressure turbopump performance on various engine parameters. Based on analysis of the responses, several new parameters are proposed for further investigation as power-level specific redlines
The application of neural networks to the SSME startup transient
Feedforward neural networks were used to model three parameters during the Space Shuttle Main Engine startup transient. The three parameters were the main combustion chamber pressure, a controlled parameter, the high pressure oxidizer turbine discharge temperature, a redlined parameter, and the high pressure fuel pump discharge pressure, a failure-indicating performance parameter. Network inputs consisted of time windows of data from engine measurements that correlated highly to the modeled parameter. A standard backpropagation algorithm was used to train the feedforward networks on two nominal firings. Each trained network was validated with four additional nominal firings. For all three parameters, the neural networks were able to accurately predict the data in the validation sets as well as the training set
Asymmetry distributions and mass effects in dijet events at a polarized HERA
The asymmetry distributions for several kinematic variables are considered
for finding a systematic way to maximize the signal for the extraction of the
polarized gluon density. The relevance of mass effects for the corresponding
dijet cross section is discussed and the different approximations for including
mass effects are compared. We also compare via the programs Pepsi and Mepjet
two different Monte Carlo (MC) approaches for simulating the expected signal in
the dijet asymmetry at a polarized HERA.Comment: 18 pages, LaTeX, minor stylistic changes for Z.Phys.
OPE analysis of the nucleon scattering tensor including weak interaction and finite mass effects
We perform a systematic operator product expansion of the most general form
of the nucleon scattering tensor including electro-magnetic and
weak interaction processes. Finite quark masses are taken into account and a
number of higher-twist corrections are included. In this way we derive
relations between the lowest moments of all 14 structure functions and matrix
elements of local operators. Besides reproducing well-known results, new sum
rules for parity-violating polarized structure functions and new mass
correction terms are obtained.Comment: 50 pages, additional references adde
Diffractive charged meson pair production
We investigate the possibility to measure the nonforward gluon distribution
function by means of diffractively produced \pi^+\pi^- and K^+K^- pairs in
polarized lepton nucleon scattering. The resulting cross sections are small and
are dominated by the gluonic contribution. We find relatively large spin
asymmetries, both for \pi^+\pi^- and for K^+K^- pairs.Comment: 15 pages, version with changed kinematical cuts, to be pubished in
Phys.Lett.
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