D. Levinthal

A non-numerical method for track finding in experimental high energy physics using vector computers

Abstract A non-numerical vector algorithm is used to reconstruct charged particle trajectories in the E-711 detector at Fermilab. The program is written for a CYBER 205. The vectorized version of the code is approximately 10 times faster than that of the previous scalar codes. The techniques used are applicable to other spectrometers relying on wire chambers for tracking information. The average event takes 7.7 ms to process in vector mode on a CYBER 205 compared to 1.6 s in scalar mode on a VAX-11/780.

On estimating the top quark mass from global analyses ofe+e− collision data

A study is undertaken to determine how to best extract the top quark massmt within the Minimal Standard Model (MSM) using a global fit to a variety of processes (including wide-angle Bhabha scattering) ine+e− collisions near theZ which should be measured in the coming years. Experimental cuts are accommodated as an integral part of the analysis. It is advantageous to use the collinear radiation approximation and to cut data in rapidity, center-of-mass polar angle and minimum final state invariant mass squared,s′. This avoids the need for the largest Monte Carlo acceptance correction to the data. Further, high precision cross section, calculations, (which include all one-loop electroweak and QED effects, certain higher-order improvements and perturbative QCD corrections as well as exponentiated soft and collinear photon radiation) then no longer require a Monte Carlo. This results in a speedup factor of at least fifty thousand (>5×104) in EXPOSTAR. The data (corrected only for detector cracks, resolution and small non-collinear radiation effects) can therefore be fit quickly and directly forMz,mt,mHiggs and αstrong without recourse to unphysical intermediate quantities (weak mixing angles, running couplings, partial widths, κ*, etc.) Determination ofmt could be as precise as ±15 GeV (and another±20 GeV frommHiggs) at the end of LEP running in 1991. Longitudinally polarized beams with very small polarization error could give an error onmtsmaller, by a factor ≈4 for the same luminosity.

Construction and testing of a precision 2 m long straw chamber prototype

Abstract The construction and testing of a 2 m straw chamber prototype is described. We achieved straw alignment of better than 30 μm and wire alignment of order 7 μm while keeping the amount of material to about one half the amount normally needed for a similar all-wire drift chamber.

Average fraction of jet momentum carried by highP⊥ leading hadrons

The average fraction,, of jet momentum carried by the associated charged leading hadron has been determined in the reactionp+N→h1+h2+X whereN is the target nucleon;h1,h2 are the leading particles of two jets produced at highP⊥. An 800 GeV/c proton beam and 4 nuclear targets: Be, Al, Fe and W were used. The distributions agree with the QCD-parton model predictions for single independent protonnucleon scattering and independent fragmentation process.