4,624 research outputs found
Measuring sigma(e^+e^- \to hadrons) using tagged photon
We propose to use events with radiated photons in e^+e^- collisions to
measure the total cross section of e^+ e^- \to hadrons as a function of the
center of mass energy. The Monte Carlo simulation for the collider DAPHNE shows
that a competitive accuracy can be achieved with this method.Comment: revtex, 13 page
Cyclosporin A inhibits PGE2 release from vascular smooth muscle cells
The influence of the fungoid undecapeptide cyclosporin A (CyA) on PGE2 release from cultured rat aortic smooth muscle cells was investigated in this study. We found that CyA time and concentration dependently (ED50:500 ng/ml) inhibited PGE2 release from the cells. CyA attenuated both basal and PGE2 release evoked by angiotensin II (10(-10)-10(-6) M), arginine vasopressin (10(-10)-10(-6) M) and ionomycin (10(-9)-10(-6) M). CyA (1 microgram/ml) did not affect the conversion of exogenous arachidonic acid (1 microM) into PGE2. The inhibitory effect of CyA was neutralized by high concentrations of the calcium ionophore ionomycin (greater than 3 X 10(-6) M). Taken together our results indicate that CyA inhibits both basal and vasoconstrictor evoked PGE2 release from vascular smooth muscle by impairing the availability of free arachidonic acid rather than by inhibiting the conversion of arachidonic acid into PGE2
Gluon Fragmentation into Heavy Quarkonium
The dominant production mechanism for heavy quark-antiquark bound states in
very high energy processes is fragmentation, the splitting of a high energy
parton into a quarkonium state and other partons. We show that the
fragmentation functions describing these processes can be calculated
using perturbative QCD. We calculate the fragmentation functions for a gluon to
split into S-wave quarkonium states to leading order in the QCD coupling
constant. The leading logarithms of , where is the factorization
scale and is the heavy quark mass, are summed up using Altarelli-Parisi
evolution equations.Comment: LateX 11 pages (3 figures available upon request). NUHEP-TH-92-2
Five-loop fermion anomalous dimension for a general gauge group from four-loop massless propagators
We extend the result of the analytic calculation of
the quark mass anomalous dimension in pQCD [1] to the case of a generic gauge
group. We present explicit formulas which express the relevant renormalization
constants in terms of four-loop massless propagators. We also use our result to
shed new light on the old puzzle of the absence of even zetas in results of
perturbative calculations for a class of physical observables.Comment: An important reference [47] is correcte
Scalar Correlator at O(alpha_s^4), Higgs Decay into b-quarks and Bounds on the Light Quark Masses
We compute, for the first time, the absorptive part of the massless
correlator of two quark scalar currents in five loops. As physical applications
we consider the O(alpha_s^4) corrections to the decay rate of the Standard
Model Higgs boson into quarks, as well as the constraints on the strange quark
mass following from QCD sum rules.Comment: 5 pages, REVTeX4. Few references updated. The final version, accepted
for publication. The complete paper is also available via the www at
http://www-ttp.physik.uni-karlsruhe.de/Preprints
Quark Mass and Field Anomalous Dimensions to
We present the results of the first complete analytic calculation of the
quark mass and field anomalous dimensions to in QCD
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