D-meson enhancement in pp collisions at the LHC due to nonlinear gluon evolution (open access)

D-meson enhancement in pp collisions at the LHC due to nonlinear gluon evolution

When nonlinear effects on the gluon evolution are included with constraints from HERA, the gluon distribution in the free proton is enhanced at low momentum fractions, x {approx}< 0.01, and low scales, Q{sup 2} {approx}< 10 GeV{sup 2}, relative to standard, DGLAP-evolved, gluon distributions. Consequently, such gluon distributions can enhance charm production in pp collisions at center of mass energy 14 TeV by up to a factor of five at midrapidity, y {approx} 0, and transverse momentum p{sub T} {yields} 0 in the most optimistic case. We show that most of this enhancement survives hadronization into D mesons. Assuming the same enhancement at leading and next-to-leading order, we show that the D enhancement may be measured by D{sup 0} reconstruction in the K{sup -}{pi}{sup +} decay channel with the ALICE detector.
Date: August 22, 2004
Creator: Dainese, A.; Vogt, R.; Bondila, M.; Eskola, K.J. & Kolhinen, V.J.
System: The UNT Digital Library
Unstable crack motion is predictable (open access)

Unstable crack motion is predictable

Yoffe's linear theory of dynamic brittle fracture suggests that crack motion will be unstable beyond {approx}70% of the Rayleigh speed, a prediction that is not supported by experiment. We show by atomistic simulations that hyperelasticity, the elasticity of large strains, plays a governing role in the instability dynamics of brittle fracture. A simple scaling model based on an effective elastic modulus, coupled with Yoffe's solution, gives successful predictions for the onset speed of the crack instability.
Date: August 22, 2004
Creator: Abraham, F
System: The UNT Digital Library