MRS Parton distributions

The MRS parton distributions are produced by A. D. Martin, R. G. Roberts, and W. J. Stirling, sometimes with coauthors (in recent years, Robert Thorne). More about these distributions can be found at the HEPDATA site at Durham.

References

MRST 2001
- "MRST2001: partons and alpha_s from precise deep inelastic scattering and Tevatron jet data", A.D. Martin, R.G. Roberts, W.J. Stirling and R.S Thorne, Univ. Durham preprint IPPP/01/37 (2001), [hep-ph/0110215], Eur. Phys. J. C23 (2002) 73.
For references to older sets, please see the MRS website.

Definitions

The MRS parton distributions available here are defined at next-to-leading order in the MSbar scheme. They include u,d,s,c and b quarks.

Smoothing

For the MRSA' and MRSG partons, we have made a parton table using the analytic form supplied by MRS. For the R-series and the MRST series, we have made a parton table using the table interpolation supplied by MRS. However, our table interpolation requires that the parton distributions represented in the tables be smooth functions of x and Q². At some places (where the values of the parton distributions are small) the functions given by the MRS parton tables are not smooth. We have, therefore, applied a smoothing operation to the MRS table before making a table in our format. Here is a picture illustrating our smoothed version and the original MRS version.

Parton distribution tables

NOTE (5 December 2002): I have discovered that the line in the 1998 MRST tables that specified the (five flavor) QCD lambda value was wrong. The parton distribution numbers in the table were OK, but a program that relied on reading the lambda value, such as the EKS jet program, would get the wrong answer. The tables in the links below are corrected. (DES)

NOTE (31 February 2003): Another glitch. For a few weeks, I had tables for MRST01(1) and MRST01(4) here. They were dated 16 December 2002. Unfortately, when I got the data from MRS upon which these tables were based, my web brouser put two blank lines in the MRS files. This resulted in incorrect files here. The tables in the links below are corrected. (DES)

MRS(A') parton distribution table.
MRS(G) parton distribution table.
MRS(R1) parton distribution table.
MRS(R2) parton distribution table.
MRS(R3) parton distribution table.
MRS(R4) parton distribution table.
MRST98(1) parton distribution table.
MRST98(2) parton distribution table.
MRST98(3) parton distribution table.
MRST98(4) parton distribution table.
MRST98(5) parton distribution table.
MRST01(1) parton distribution table (the standard).
MRST01(4) parton distribution table (fits jet data better).

The MRST(n)DIS distributions are not included because they are negative in certain regions and our interpolation routine at present works only with positive functions.

FORTRAN code for creating these tables

Code to create our MRS(A') table.
Code to create our MRS(G) table.
Code to create our MRS(R_n) tables from the MRS tables.
Code to create our (corrected) MRST98(n) tables from the MRS tables.
Code to create our MRST01(n) tables from the MRST01 tables.

Davison E. Soper and Parvez Anandam
Institute of Theoretical Science, University of Oregon, Eugene OR 97403 USA
soper@physics.uoregon.edu
email:

soper@physics.uoregon.edu