Ellis, Kunszt and Soper Jet Programs

We present here fortran code to calculate jet cross sections in next-to-leading order quantum chromodynamics. We also provide some explanation, but we must admit that the programs are not designed to be user friendly. Caveat emptor.

Explanation of Jet version 3.4.

Code for Jet version 3.4

jet3_4.f One jet inclusive cross section d sigma / d E_T.
jjy3_4.f Two jet inclusive cross section d sigma / d M_JJ d y*.
jjyy3_4.f Two jet inclusive cross section d sigma / d ET d y1 d y2.
jetsubs3_4.f Subroutines for these.
Slightly revised, 2 September 1997. (Avoid ieee divide by zero flags. Results are not affected.)

Running these is easy. The code in jet3_4.f and jjy3_4.f could be modified by knowledgeable users wishing to accomplish particular ends, such as changing the jet definition or modifying some of the parameters. We packaged the routines that should never need to be modified into jetsubs3_4.f, and in fact have not modified this code in any nontrivial way since 1992. Changes here are likely to result in the program giving the wrong answer.

New, 12 Decmeber 1996. The code for jet3_4.f now includes R_sep.

For the user's convenience, we also provide a special version of jet3_4.f in which the renormalization and factorization scales can be chosen to be a constant times ETmax, the maximum ET of any jet in the event. The purpose of this is to facilitate comparisons with the JETRAD program of Giele, Glover, And Kosower, for which this scale setting scheme is the default.

For some purposes, one would like a smooth function that fits the calculated cross section. The program provides this. One should just check that the quality of the fit is OK by comparing the columns Corrected XSECT and Unsmeared Fit XSECT. The smooth function, which gives Unsmeared Fit XSECT, is TRIAL(ET) times a polynomial in LOG(ET):

TRIAL(ET) * ( COUT(0,0) + COUT(1,0) LOG(ET)**2 + COUT(2,0) LOG(ET)**4 )

The coefficients COUT(J,K) are reported in the program output. The explicit form of TRIAL(ET) can be found in the program listing.

Explanation of Jet version 4.0.

Code for Jet version 4.0

jet4_0.f Triply differential two jet inclusive cross section d sigma / d x_A dx_B d y* : makes table of K factors.
readjet4_0.f Triply differential two jet inclusive cross section d sigma / d x_A dx_B d y* : uses table of K factors.
jetsubs4_0.f Subroutines for this.

The code in jet4_0.f and readjet4_0.f could be modified by knowledgeable users wishing to accomplish particular ends, such as changing the jet definition or modifying some of the parameters. We packaged the routines that should never need to be modified into jetsubs4_0.f. (The only modification compared to jetsubs3_4 is to make some of the output arrays three dimensional.) Changes here are likely to result in the program giving the wrong answer.

A Potpouri of Partons, including parton tables needed for these programs.

References.

Davison E. Soper, Institute of Theoretical Science, University of Oregon, Eugene OR 97403 USA soper@uoregon.edu