===================================================== ===================================================== Instructions for generating the nCTEQ Demonstration program. ===================================================== ===================================================== Unpack the files into a directory. The list of files is: Cteq6Pdf-2008_FIO.f demo1.f demo2.f doit pdfNames.f README.TXT setNpdf2.f The PDF grids in form of PDS table files are collected into the directory: Grids The "doit" file has the Linux commands to build the demo. This will produce "demo1" and "demo2" If you execute demo1, it will print out sample PDFs using all the table files. A partial log file is below. ===================================================== dell 1:% ./doit Now execute demo1 dell 2:% ./demo1 enter x,Q / -------------------------------------- x,Q = 0.1 10. -------------------------------------- FILE NAME A Z :(Dbar,Ubar,G,U,D,S,C,B) decut3_108_54 ||108 54 1.24 1.24 13.4 5.64 5.64 0.738 0.353 0.103 decut3_119_59 ||119 59 1.24 1.25 13.5 5.64 5.66 0.740 0.356 0.104 decut3_1_1 || 1 1 1.35 0.952 10.8 6.50 3.96 0.616 0.258 7.807E-02 decut3_12_6 || 12 6 1.22 1.22 12.2 5.55 5.55 0.688 0.308 9.119E-02 decut3_131_54 ||131 54 1.21 1.28 13.5 5.42 5.88 0.743 0.358 0.105 decut3_14_7 || 14 7 1.22 1.22 12.3 5.56 5.56 0.692 0.311 9.199E-02 ... ===================================================== The PDS files are grouped into families, and the trailing integers identify the (A,Z) of the specific PDS file. The first (larger) is the A, and the second (smaller) is Z. For example "decut3_108_54.pds" has A=108 and Z=54. If the PDS file is missing the trailing integers, it is for a proton by default. Thus, "decut3g1.pds" has A=1 and Z=1. ===================================================== ===================================================== Instructions for calling the nCTEQ PDFs ===================================================== ===================================================== To use the PDS files, there are 2 key steps. These are demonstrated in the demo.f program. 1) Call "SetNPDF" to setup a specific PDS file. Call SetNPDF (file,ierr) !*** Call by file name "file" is the PDS filename (with subdirectory if necessary) to open. "ierr" is returned non-zero if there is an error. 2) Once SetNPDF is called, the PDFs are obtained with CtqNpdf. pdfN(iptn)= CtqNpdf(iptn,x,Q,iA,iZ) !*** Get A,Z adjusted nucleon values "iptn" is the parton number in MASS-ORDER: (u,d,s,c,b,t). IMPORTANT: note this order is different from the Monte Carlo standard order of (d,u,s,c,b,t). "x" is the parton x. "Q" is the parton Q in GeV. "iA" and "iZ" are the (A,Z) values. If (A,Z)=(1,1) the results for the proton are returned. Note, pdfN returns the PDF, _NOT_ the momentum x*PDF. If a different PDS file is desired, "SetNPDF" must be called again. ===================================================== ===================================================== FAMILIES OF nCTEQ PDFs ===================================================== ===================================================== The PDF are grouped into families listed below. The trailing integers on the file names indicate the (A,Z) values computed. Here we focus on the general family properties. ---------------------------------------------------- decut3 The decut3 fit is the PDF from reference Phys.Rev.D80:094004,2009 (arXiv 0907.2357). These PDFs do NOT include any neutrino data. ---------------------------------------------------- decut3g1 decut3g2 decut3g3 decut3g4 decut3g5 decut3g7 decut3g8 decut3g9 These fits (as well as the above decut3 fit) are from reference JHEP 1101:152,2011 (arXiv:1012.1178). These different fits vary the small x behavior of the gluon distribution. The details are contained in Table 2 of the above reference. We summarize the key parameters below, and refer the reader to the text for the definitions and details. NAME PARM c_{1,1} c_{1,2} decut3 Fixed -0.29 -0.09 decut3g1 Fixed 0.2 50.0 decut3g2 Fixed -0.1 -0.15 decut3g3 Fixed 0.2 -0.15 decut3g4 Free 0.2 -0.15 decut3g5 Fixed 0.2 -0.25 decut3g7 Fixed 0.2 -0.23 decut3g8 Fixed 0.35 -0.15 decut3g9 Fixed 0.0 ----- (free proton) ---------------------------------------------------- decut3 glofac1a glofac1c glofac1b global2b nuanua1 This family of PDFs are from reference Phys.Rev.Lett.106:122301,2011 (arXiv:1012.0286). The decut3 fit does not use the neutrino data, while the nuanua1 fit includes the neutrino data but no charged lepton data. The "globfac" fits use both the neutrino and charged lepton data with various weight factors as indicated below. decut3 w=0 glofac1a w=1/7 glofac1c w=1/4 glofac1b w=1/2 global2b w=1 nuanua1 w=infinity ---------------------------------------------------- nutuncor1 nutuncor2 nutuncor3 nutuncor4 This family of PDFs are also from reference Phys.Rev.Lett.106:122301,2011 (arXiv:1012.0286). They use both the charged lepton and neutrio data, but they use uncorrelated errors for the neutrino data. The different sets used different Q2 cuts and different gluon inputs as indicated below. nutuncor1 - uncorr.errors & Q2>4 nutuncor2 - uncorr.errors & Q2>5 nutuncor3 - uncorr.errors & Q2>5 & different gluon (decut3g4 from decut3gx family) nutuncor4 - uncorr.errors & Q2>4 & different gluon (decut3g4 from decut3gx family) ===================================================== ===================================================== QUESTIONS: ===================================================== ===================================================== For questions, contact: Karol Kovarik kovarik@particle.uni-karlsruhe.de Fred Olness olness@smu.edu ===================================================== ===================================================== ===================================================== ===================================================== DEMO2: ===================================================== ===================================================== The "demo2" routine illustrates a simple means to work with 2 pdf files at the same time. It is intended to be used e.g. in p-A collisions when one has to use 2 different pdf files to describe the initial state. After initializing 2 files with Set2NPDF(file1,file2,ierr), one can access all PDF for all partons from both files with Ctq2Npdf(iset,iparton,x,Q,iA,iZ). This saves time in cases where one integrates over x and would have to open and close files for each evaluation of the differential cross-section. CAUTION: Note, the routines with 2 PDFs are for demonstration only. These assume the internal structures (x, Q, NF, and PDF arrays) are the same size. A more flexible interface (implemented with pointers in C) is under construction.