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   herwig_i/herwig_v64a_cdf.doc                         
   -----------------------------
                                           July 2002.
 
 
     Here are some items concerning HERWIG, version 6.4, as set up for CDF
   run 2.
     For a nice 91-page description of herwig, as of v 6.200, see the official
   write-up in hep-ph/0011363, G. Corella et al. That write-up can be reached
   from the Herwig web site, http://hepwww.rl.ac.uk/theory/seymour/herwig/ .
     That write-up includes (pages 33 - 37) a list of the hard sub-
   processes that were available in v 6.200 (and remain in v 6.4).
     Also reachable from that web site is the v 6.3 release note (under
   "Old HERWIG versions") and the v 6.4 release note (line ~4 of the
   web site).
     v 6.3 was released July 2001 but not set up at Fermilab. This version
   added many new processes: WW, WZ, ZZ production, ZQQ production,
   and several 2->3 MSSM Higgs production processes. Details on these
   and on some bug fixes are in the release note.
     v 6.4 was released January 2002. The main new feature for CDF is the
   introduction of spin correlations between the production and decay
   of heavy fermions. For details see the release note.
     In v6_4 there are two items that appear to be not user-friendly. See
   section below on "Changes made in v6_4 by CDF".
     The pure herwig code is in $HERWIG_DIR/src/herwig .
     
 
 
                Jeremy Lys.
 
 
 -----------------------------------------------------------------------------
 -----------------------------------------------------------------------------
 
      Current status (18-Jul-2002)
      -----------------------------
     
 
     Herwig v6_4 has been in development since May 2002. It is not
   in any frozen release 4.5.* or earlier, it is not in 4.6.2, it
   is in 4.6.0int5 .
     With cdfGen, herwig runs and produces sensible output.
     With cdfSim, herwig runs and produces sensible output.
 
     On fcdfsgi2, for t.tbar events with underlying event (Process 1706)
   Herwig takes 0.2 cpu sec/event. Simulation on these events takes
   ~ 15 cpu sec/event. For SUSY events,  2 partons to 2 spartons (Process
   3010), the analogous times are 0.7 and ~15 cpu sec/event. But note
   that Simulation times can vary appreciably, depending on the 
   current state of the simulation.
 
     Herwig produces sensible output for SUSY processes. For SUSY, a file
   must be read in that gives SUSY particle properties. Such files can
   be written by hand or can be produced using the ISAWIG program (a
   combination of Isajet and a new package, HWISSP). There is an ISAWIG
   web page, http://www.hep.phy.cam.ac.uk/~richardn/HERWIG/ISAWIG/ ,
   which gives information on ISAWIG and from which one can find sample
   input files for SUSY processes. Three of those files reside in
   fcdfsgi2: /cdf/home/lys/SUSY/*. Note that for Process numbers 3000 -
   3099 (MSSM) it is good for efficiency to set PTPOW = 2 (see talk-to
   notes below).
 
     Note that Herwig can get into a (semi-)infinite loop if the chosen
   beam momentum is too low for a SUSY process. I have seen this for
   processes 3110 and 3230 with Pbeam1 = Pbeam2 = 1000. No warning
   message is printed (the loop occurs on testing RQ52 in hwhisq, and
   is a function of input particle masses).
 
     StdHep README's state that Version 5.01 of StdHep is appropriate
   for Herwig 6.4. But, as of May 2002, version  5_01 is not ready. 
   In tests I have found no difference between using 5_01 and the
   present default, 4_09.
 
 -----------------------------------------------------------------------------
 -----------------------------------------------------------------------------
 
      Some properties of Herwig to be aware of
      ----------------------------------------
 
   1. In Herwig, the "second mother" (jmo2) and "second daughter" (jda2)
   have different meanings when partons are involved: they are the parton's
   colour mother and colour daughter (see Herwig 6 manual sect. 8.3). In
   general, if a hepg entry has jda2<jda1 one can assume that there is
   just one daughter, jda1.
 
   2. Searching *up* the generator level chain to find ancestors of a particle
   can give wrong answers and infinite loops. Problem occurs amongst the
   clusters and quarks and diquarks. So the stdhep library routine 
   stdparentlst.F  is not good for herwig. An alternative, which searches
   *down* the chain, is in  cdfsga ~lys/backup/stdparentlst.F .
   But note that this alternative has problems with isajet and pythia events.
 
   3. Herwig gives non-zero vhep values (i.e., production vertex x y z t) for
   most quarks, diquarks, gluons, clusters, etc. (as explained in the 
   documentation). Hence a ttbar event may have 395 entries and 385 displaced
   vertices. We could get rid of "unwanted" vertices by resetting vhep values
   to zero (in hwufne.f or hwanal.f, for example).
 
   4. Herwig has a non-zero lifetime for pizero. So gammas from pizero decay
   get a different production vertex than the pizero. But these vertices
   may not appear in OBSV, because of the Lifetime cut (10E-16)in McEvent.cc .
 
   5. In top quark decays in v 6.4 (as in v 6.2 but different from v 5.9)
   there is an explicit W. That is, we get t -> b W, with W -> (u,dbar) or
   (c,sbar) or (e/mu/tau,neutrino). But this W is "added later" (see hwudat.f,
   which lists only 3-body top decays, and hwdhob.f), and its decay is not
   changed by MODBOS settings.
 
   6. A small but non-zero width for the top quark appears in v6.4 (actually
   it got in in a bug fix).
 
   7. See the comment on the the quantity MAXER below. You may want to have
   a line in talk Herwig that says:
     Maxer set 1.E10
 
   8. As set up at CDF, Herwig does not decay hadrons that contain a b or c
   quark. It is assumed that QQ will be used. With the current QQ defaults,
   it is good to set  Bc, Upsilon, B_Baryons and prompt_charm decays on
   in talk QQModule.
 
 -----------------------------------------------------------------------------
 -----------------------------------------------------------------------------
 
      To run HERWIG
      -------------
     One can run either cdfGen or cdfSim. These exist in code releases
   (in bin/$BFARCH) and often in development. They are created via
   gmake generatorMods or gmake SimulationMods resp. Only cdfSim includes
   possible simulation in the detector.
     Some example tcl files exist in $CDFSOFT2_DIR/herwig_i/examples. There,
   herwig_top.tcl and herwig_test.tcl are intended for cdfGen running.
   And hersim0_test.tcl and hersim1_test.tcl for cdfSim running without
   and with detector simulation, respectively. 
 
     So one can do something like:
 
   $CDFSOFT2_DIR/bin/$BFARCH/cdfGen  herwig_test.tcl > herwig_test.log
 
 
     For a SUSY process, one would have in the tcl file, inside the
   Herwig talkto, something like:
 
     Process set 3010
     Read_susy
       File_Readsusy set /cdf/home/lys/SUSY/sps_pt1a.1105.in
     exit
      
 
 
     The type of reaction is specified by the Process number, which is set in
   the talkto (see below).
     For a list of the possible Process numbers, see the official write-up
   (hep-ph/0011363, G. Corella et al.), pages 33-53, and the added processes
   described in the v6.3 Release Note (see above).
     A few  Process numbers are:
           1453    q q' -> W -> tau.nutau,
           1500    QCD 2->2 hard parton scattering,
           1706    t.tbar production,
           2100    W + jet production,
           2300    SM Higgs + jet production.
     If 10000 is added (e.g., 11706) the underlying event is suppressed.
 
 
     In running Herwig, a few warnings: HWWARN ... HWSFUN: CODE = 5 (or 4)
   often occur.
 
     For more and better wisdom on tcl files, see Ken Bloom's CDF note
   5294, and the tcl files in $CDFSOFT2_DIR/SimulationMods/test .
 
 -------------------------------------------------------------------------------
 -------------------------------------------------------------------------------
 
     HERWIG talk-to
     --------------
 
     Simple Herwig talk-to example:
 
 talk Herwig
   help                // This gives ~50 lines of information
   show                // ~100 lines, gives values of all the variables
   Process set 11706   // Note order, "set" does NOT come first 
   Masses
     top set 175.      // Decimal point not required (of course)
     show              // Gives values of variables in Menu 11 - Masses
   exit
   Prints
     maxpr set 1       // Gives internal Herwig print of 1 event
     prvtx set 0       // In Herwig is Boolean, default true, here is integer. 
   exit
 exit
 
 -------------------------------------------------------------------------------
 
     Herwig talk-to details:
 
     The Herwig manual for version 6 (hep-ph/0011363, G Corcella et al., see
   above) lists three sets of variables that must or may be set by a user. 
   These are reproduced below, with the Herwig description for each of the
   three lists in quotes. A fourth list contains variables that have been
   added in v6.3 or v6.4 and which a CDF user may wish to reset.
 
     Appended, on the right hand side of the lists, is HERWIG talk-to
   information, as set up for CDF users in generatorMods/HerwigModule.cc
   (and ditto.hh).
     The talk-to "name" is the word required in the talk-to interaction,
   after giving the menu command. The menu commands are in the Menu table
   below the lists. G stands for general menu, for which no menu command is
   needed. 
  
     Default values in the lists below (except the *-ed ones) are as set in
   the initializing HERWIG routines. Almost all are set in hwigin.f. Some
   values are set or reset in HerwigInterface.F, and indicated by a star (*)
   in the default column below.
     The talk-to variables are preset in HerwigModule, but all except three
   are reset by Herwig. The three not reset are  noshower, nohadronization
   and File_Readsusy; the first two are used in HerwigModule.cc but not in any
   Herwig routines (are not in Herwig.inc), and the third is passed as an
   argument to cdfreadsusy.
 
     Some of the parameters listed are not (i.e., not currently) accessible in
   the talk-to. For such parameters there are no entries to the right of the
   herwig information.
 
     Beneath the lists of variables and parameters is a list of 5 further
   variables that it may be useful to change sometimes and that can be set in
   the talk-to.
 
     -------------------------------------------
 
    "As  indicated  above,  a  number of variables must be set in the main
    program to specify what is to be simulated:"
 
    +----------+------------------------------+-----------+     talk-to
    |   Name   |     Description              |  Default  |Menu "name"
    +----------+------------------------------+-----------+
    | PART1    | Type of particle in beam 1   |*'P       '| 01  Beam1
    | PART2    | Type of particle in beam 2   |*'PBAR    '| 01  Beam2
    | PBEAM1   | Momentum of beam 1           |*980.      | 01  Pbeam1
    | PBEAM2   | Momentum of beam 2           |*980.      | 01  Pbeam2
    | IPROC    | Type of process to generate  |*1500      |  G  Process
    | MAXEV    | Number of events to generate | Not used  |
 
    +----------+------------------------------+-----------+
 
 
 
    "The quantities that may be regarded as adjustable parameters are"
 
    +----------+----------------------------------+-------+     talk-to
    |   Name   |     Description                  |Default|Menu "name"
    +----------+----------------------------------+-------+
    | QCDLAM   | QCD Lambda (see below)           | 0.18  |  G  Lambda_QCD
 
    +----------+----------------------------------+-------+
    | RMASS(1) | Down    quark mass               | 0.32  | 11  down
    | RMASS(2) | Up      quark mass               | 0.32  | 11  up
    | RMASS(3) | Strange quark mass               | 0.50  | 11  strange
    | RMASS(4) | Charmed quark mass               | 1.55  | 11  charm
    | RMASS(5) | Bottom  quark mass               | 4.95  | 11  bottom
    | RMASS(6) | Top     quark mass               | 174.3 | 11  top
 
    +----------+----------------------------------+-------+
    | RMASS(13)| Gluon effective mass             | 0.75  | 11  gluon
 
    +----------+----------------------------------+-------+
    | VQCUT    | Quark virtuality cutoff (added to| 0.48  | 05  Qcutoff
    |          | quark masses in parton showers)  |       |
    | VGCUT    | Gluon virtuality cutoff (added to| 0.10  | 05  Gcutoff
    |          | effective mass in parton showers)|       |
    | VPCUT    | Photon virtuality cutoff         | 0.40  | 05  Pcutoff
 
    +----------+----------------------------------+-------+
    | CLMAX    | Maximum cluster mass parameter   | 3.35  | 06  Clmax
    | CLPOW    | Power in maximum cluster mass    | 2.00  | 06  Clpow
    | PSPLT(1) | Split cluster spectrum, non-b    | 1.00  | 06  Psplt1
    | PSPLT(2) | Split cluster spectrum, b        | 1.00  | 06  Psplt2
 
    +----------+----------------------------------+-------+
    | QDIQK    | Maximum scale for gluon->diquarks| 0.00  | 06  Qdiqk
    | PDIQK    | Gluon->diquarks rate parameter   | 5.00  | 06  Pdiqk
 
    +----------+----------------------------------+-------+
    | QSPAC    | Cutoff for spacelike evolution  | 2.50 | 05 Spacelike_evolution
    | PTRMS    | Intrinsic pt in incoming hadrons| 0.00 | 05 Pt_incoming_hadrons
 
    +----------+------------------------------+-----------+
 
 
 
    "A number of quantities can be reset to control the program and
    various options:"
 
    +----------+----------------------------------+-------+     talk-to
    |   Name   |     Description                  |Default|Menu "name"
    +----------+----------------------------------+-------+
    | NEVHEP   | Current no. of events            | 0     |
    | NHEP     | Current no. entries in /HEPEVT/  | 0     |
 
    +----------+----------------------------------+-------+
    | IPRINT   | Printout option                  |*1     | 14  iprint
    | MAXPR    | Number of events to print out    |*0     | 14  maxpr
    | PRVTX    | Include vertex info in print out | .TRUE.| 14  prvtx
    | NPRFMT   | Print to screen or log file      | 1     | 14  nprfmt
    | PRNDEC   | Use decimal/hexadecimal in print | .TRUE.| 14  prndef
    | PRNDEF   | Print to screen or log file      | .TRUE.| 14  prndef
    | PRNTEX   | Print to latex file              |.FALSE.| 14  prntex
    | PRNWEB   | Print to html file               |.FALSE.| 14  prnweb
 
    +----------+----------------------------------+-------+
    | MAXER    | Max number of errors             |*100   |  G  Maxer
 
    +----------+----------------------------------+-------+
    | LWEVT    | Unit for writing output events   |*0     |
 
    +----------+----------------------------------+-------+
    | LRSUD    | Unit for reading Sudakov table   | 0     |
    | LWSUD    | Unit for writing Sudakov table   | 77    |
    | SUDORD   | Alpha_s order in Sudakov table   |*2     | 02  Sudakov_order
    | INTER    | Order of interp., Sudakov tables | 3     |
 
    +----------+----------------------------------+-------+
    | NRN(1)   | Random number seed 1             |not used| 
    | NRN(2)   | Random number seed 2             |not used|
    | WGTMAX   | Max weight (0 to search for it)  | 0.    | 09  Maxwt  
    | NOWGT    | Generate unweighted events       | .TRUE.| 09  No_weights
    | AVWGT    | Mean event weight                | 1.0   |
    | EFFMIN   | Minimum acceptable efficiency    | 0.001 | 09  Effmin
 
    +----------+----------------------------------+-------+
    | AZSOFT   | Soft gluon azimuthal correlations| .TRUE.| 05  Azsoft
    | AZSPIN   | Gluon spin azimuthal correlations| .TRUE.| 05  Azspin
 
    +----------+----------------------------------+-------+
    | HARDME   | Use hard matrix-el corrections   | .TRUE.|
    | SOFTME   | Use soft matrix-el corrections   | .TRUE.|
    | GCUTME   | Gluon energy cut in top ME corr. | 2.0   |
 
    +----------+----------------------------------+-------+
    | NCOLO    | Number of colours                | 3     | 10  Colors
    | NFLAV    | Number of (producible) flavours  | 6     | 10  Flavors
 
    +----------+----------------------------------+-------+
    | MODPDF(I)| PDFLIB structure function set and| -1    | 03  Modpdf
    | AUTPDF(I)| author group for beam I(=1,2)    | 'MRS' | 03  Autpdf
    |          | (if MODPDF()<0 do not use PDFLIB)|       |
    | NSTRU    | Input structure function set     | 8     | 03  Nstru
    |          | (1-5 old, 6-8 MRST 1998)         |       |
 
    +----------+----------------------------------+-------+
    | PRSOF    | Prob. of soft underlying event   | 1.0   | 07  Prsof
 
    +----------+----------------------------------+-------+
    | ENSOF    | multipl. factor for underly evt  | 1.0   | 07  Ensof
    | PMBN1    | Soft interaction model parameter | 9.11  | 07  Pmbn1
    | PMBN2    | Soft interaction model parameter | 0.115 | 07  Pmbn2
    | PMBN3    | Soft interaction model parameter | -9.50 | 07  Pmbn3
    | PMBK1    | Soft interaction model parameter | 0.029 | 07  Pmbk1
    | PMBK2    | Soft interaction model parameter |-0.104 | 07  Pmbk2
 
    +----------+----------------------------------+-------+
    | PMBM1    | Soft interaction model parameter | 0.4   | 07  Pmbm1
    | PMBM2    | Soft interaction model parameter | 2.0   | 07  Pmbm2
    | PMBP1    | Soft interaction model parameter | 5.2   | 07  Pmbp1
    | PMBP2    | Soft interaction model parameter | 3.0   | 07  Pmbp2
    | PMBP3    | Soft interaction model parameter | 5.2   | 07  Pmbp3
 
    +----------+----------------------------------+-------+
    | IOPREM   | Options for remnant clusters     | 1     |
 
    +----------+----------------------------------+-------+
    | BTCLM    | Mass param. in remnant fragmentn.| 1.0   |
 
    +----------+----------------------------------+-------+
    | VMIN2    | Min. parton virt-sq in dist. cal.| 0.1   |
 
    +----------+----------------------------------+-------+
    | CLRECO   | Include colour rearrangement     |.FALSE |
    | PRECO    | Probability for rearrangement    | 1./9. |
    | EXAG     | Lifetime scaling for weak bosons | 1.    |
 
    +----------+----------------------------------+-------+
    | ETAMIX   | eta/eta' mixing angle in degrees | -23   |
    | PHIMIX   | phi/omega         mix ang. degs  | +36   |
    | H1MIX    | h1(1380)/h1(1170) mix ang. degs. | 35.26 |
    | F0MIX    | -/f0(1370)        mix ang. degs. | 35.26 |
    | F1MIX    | f1(1420)/f1(1285) mix ang. degs. | 35.26 |
    | F2MIX    | f2'/f2            mix ang. degs. | +26   |
    | ET2MIX   | et2(1645)/et2(1870) mix ang. deg | 35.26 |
    | OMHMIX   | -/omega(1600)     mix ang. degs. | 35.26 |
    | PH3MIX   | phi3/omega3       mix ang. degs. | +28   |
 
    +----------+----------------------------------+-------+
    | B1LIM    | B cluster -> 1 hadron parameter  |  0.0  |
    | CLDIR(1) | Orientation of clusters, non-b   | 1     | 06  Cldir1
    | CLDIR(2) | Orientation of clusters, b       | 1     | 06  Cldir2
    | CLSMR(1) | Width of G. angle smear, non-b   | 0.0   | 06  Clsmr1
    | CLSMR(2) | Width of G. angle smear, b       | 0.0   | 06  Clsmr2
 
    +----------+----------------------------------+-------+
    | PWT[I]   | a priori weights, f.fbar pairs   | 1.0   | 06  Pwt1
    |          | - I=1-7: d,u,s,c,b,t,qq'         | 1.0   | 06  Pwt2
    |          |                                  | 1.0   | 06  Pwt3
    |          |                                  | 1.0   | 06  Pwt4
    |          |                                  | 1.0   | 06  Pwt5
    |          |                                  | 1.0   | 06  Pwt6
    |          |                                  | 1.0   | 06  Pwt7
    |REPWT(L,J,N)| a priori weight, L_J mesons    | 1.0   |
    | SNGWT    | a priori wgt, singlet baryons    | 1.0   | 06  Sngwt
    | DECWT    | a priori wgt, decuplet baryons   | 1.0   | 06  Decwt
 
    +----------+----------------------------------+-------+
    | PLTCUT   | Lifetime cut, "stable" particles |*1.E-11| 08  Pltcut
 
    +----------+----------------------------------+-------+
    | VTOCDK(I)| Veto cluster decay to hadron I   |.FALSE.|
    | VTORDK(I)| Veto resonance decay to hadron I |.FALSE.|
    |          | - I=290-293, f0(980), a0(980)    | .TRUE.|
 
    +----------+----------------------------------+-------+
    | PIPSMR   | Smear the primary vertex         |.FALSE.| 01  Pipsmr
    | VIPWID(1)| x width (mm)                     | 0.25  | 01  Vipwidx
    | VIPWID(2)| y width (mm)                     | 0.015 | 01  Vipwidy
    | VIPWID(3)| z width (mm)                     | 1.8   | 01  Vipwidz
 
    +----------+----------------------------------+-------+
    | MAXDKL   | Veto decays outside given volume |.FALSE.|
    | IOPDKL   | Option for volume: 1=cyl, 2=sph  | 1     |
    | DXRCYL   | Radius for cyl. option (mm)      | 20    |
    | DXZMAX   | Length for cyl. option (mm)      | 500   |
    | DXRSPH   | Radius for sph. option (mm)      | 100   |
 
    +----------+----------------------------------+-------+
    | BDECAY   | Controls which B Decay package is| 'HERW'|
    |          | used. The allowed values are:    |       |
    |          | 'HERW'; 'EURO'; or 'CLEO'.       |       |
    | MIXING   | Include neutral B meson mixing   |*.FALSE.|
    | XMIX(1)  | del_Mass/Gamma, B^0_s            | 10.0  |
    | XMIX(2)  | del_Mass/Gamma, B^0_d            | 0.7   |
    | YMIX(1)  | del_Gamma/2*Gamma, B^0_s         | 0.2   |
    | YMIX(2)  | del_Gamma/2*Gamma, B^0_d         | 0.0   |
 
    +----------+----------------------------------+-------+
    |RMASS(198)| W+ mass                          | 80.42 | 11  W
    |RMASS(199)| W- mass                          |W+ mass|
    | GAMW     | W+- width                        | 2.12  | 10  W_width
    |RMASS(200)| Z0 mass                          | 91.188| 11  Z0
    | GAMZ     | Z0 width                         | 2.495 | 10  Z_width
    | WZRFR    | W/Z rest frame for decay pars.   | .TRUE.|
    | MODBOS(I)| Force decay modes for weak bosons| 0     | 08  Modbos1
    |          |                                  | 0     | 08  Modbos2
 
    +----------+----------------------------------+-------+
    |RMASS(201)| SM Higgs mass                    | 115.  | 11  Higgs
    | IOPHIG   | Options for large Higgs mass dist| 3     |
    | GAMMAX   | Limit on range of Higgs mass dist| 10.   | 11  Gammax
    | ENHANC(I)| Enhance factor, Higgs dk mode I  | 1.0   |
 
    +----------+----------------------------------+-------+
    |RMASS(209)| 4th generation b quark mass      | 200.  |
    |RMASS(215)| 4th generation bbar mass         |RMAS209|
 
    +----------+----------------------------------+-------+
    | ALPHEM   | Thompson limit value, alpha_em(0)|0.0072993|
    | SWEIN    | Value of sin_sq(theta_W)         | 0.2319| 10  Weinberg_angle 
    | QFCH(I)  | Fermion electric charge          |       |
    | AFCH(I,J)| Fermion weak axial charge        |       |
    | VFCH(I,J)| Fermion weak vector charge       |       |
    | ZPRIME   | Include a Z' in g*/Z0 processes  |.FALSE.| 13  Zprime
    |RMASS(202)| Mass of Z'                       | 500.  | 13  ZP
    | GAMZP    | Width of Z'                      | 5.0   | 13  ZP_width
    | VCKM(I,J)| CKM matrix elements              |       |
    | SCABI    | Value of sin_sq(theta_C)         | 0.0488| 10  Cabbibo_angle
 
    +----------+----------------------------------+-------+
    |EPOLN(1-3)| Electron and positron beam       | 0.0   |
    |          | polarizations in DIS and e+e-    | 0.0   |
    |          | annihilation. First two cmpts are| 0.0   |
    |PPOLN(1-3)| transverse and only used in e+e-,| 0.0   |
    |          | 3rd cmpt is longitudinal, and is | 0.0   |
    |          | +/-1 for fully rh/lh polarized   | 0.0   |
 
    +----------+----------------------------------+-------+
    |  QLIM    | Upper limit on hard process scale| 1E08  | 04  Qlim
 
    +----------+----------------------------------+-------+
    | THMAX    | Max thrust, IPROC=110-116        | 0.9   | 04  Thrustmax
    | Y4JT     | Min. jet separn., IPROC=600-656  | 0.01  |
    | DURHAM   | Use DURHAM or JADE, IPROC=600-656| .TRUE.|
    |IOP4JT(1) | Color interference, IPROC=600-656| 0     |
    |IOP4JT(2) | Color interference, IPROC=600-656| 0     |
 
    +----------+----------------------------------+-------+
    | BGSHAT   | Scale=shat for boson-gluon fusion|.FALSE.| 04  Bgshat
 
    +----------+----------------------------------+-------+
    | BREIT    | Use Breit frame for DIS kinematix| .TRUE.|
    | USECMF   | Use hadron-hadron cmf            | .TRUE.|
 
    +----------+----------------------------------+-------+
    | NOSPAC   | Switch off space-like showers    |.FALSE.| 05  Nospac
    | ISPAC    | Changes meaning of QSPAC,        | 0     | 05  Ispac
    |          | (see the earlier notes on QSPAC) |       |
 
    +----------+----------------------------------+-------+
    | TMNISR   | Min vaule shat/S for photon ISR  | 1E-4  |
    | ZMXISR   | Max mom fraction for photon ISR  | 1-1E-6|
 
    +----------+----------------------------------+-------+
    | ASFIXD   | fixed alpha_s for Mueller-Tang xs| 0.25  |
    | OMEGA    | omega for Mueller-Tang xsec      | 0.3   |
 
    +----------+----------------------------------+-------+
    | IAPHIG   | Approx in Higgs+jet, IPROC=23xx  | 1     |
 
    +----------+----------------------------------+-------+
    | PHOMAS   | Damp structure functions for off-| 0.0   |
    |          | shell photons (0 for no damping) |       |
 
    +----------+----------------------------------+-------+
    | PTMIN    | Min pt in hadronic jet production| 10.   | 04  Ptmin
    | PTMAX    | Max pt in hadronic jet production| 1.E8  | 04  Ptmax
    | PTPOW    | 1/pt**PTPOW for jet sampling     | 4.    | 04  Ptpow
    | YJMIN    | Min jet rapidity                 |-8.    |
    | YJMAX    | Max jet rapidity                 | 8.    | 04  Ymax
 
    +----------+----------------------------------+-------+ 
    | EMMIN    | Min dilepton mass in Drell-Yan   | 10.   | 04  MassMin
    | EMMAX    | Max dilepton mass in Drell-Yan   | 1.E8  | 04  MassMax
    | EMPOW    | 1/m**EMPOW for Drell-Yan sampling| 4.    | 04  Empow
 
    +----------+----------------------------------+-------+
    | Q2MIN    | Min Q**2 in deep inelastic       | 0.0   | 04  Q2dilsmin
    | Q2MAX    | Max Q**2 in deep inelastic       | 1.E10 | 04  Q2dilsmax
    | Q2POW    | (1/Q**2)**Q2POW for sampling DIS | 2.5   | 04  Q2power
 
    +----------+----------------------------------+-------+
    | YBMIN    | Min and Max Bjorken-y in DIS     | 0.0   |
    | YBMAX    |                                  | 1.0   |
 
    +----------+----------------------------------+-------+
    | WHMIN    |Min had mass in gamma-ind. procs. | 0.0   |
 
    +----------+----------------------------------+-------+
    | ZJMAX    | Max Z in J/psi production        | 0.9   |
 
    +----------+----------------------------------+-------+
    | Q2WWMN   | Min Q**2 in Equiv Photon Approx  | 0.0   |
    | Q2WWMX   | Max Q**2 in Equiv Photon Approx  | 4.0   |
    | YWWMIN   | Min, max photon light-cone fract.| 0.0   |
    | YWWMAX   | - in Equiv. Photon approx        | 1.0   |
 
    +----------+----------------------------------+-------+
    | CSPEED   | Speed of light in vacuum (mm/s)  |2.99792E11|
    | GEV2NB   | (crossh.c/e)**2                  |389379.|
 
    +----------+----------------------------------+-------+
    | IBSH     | No. of shots for init. max wgt.  | 10000 |
    | IBRN(1)  | 1st random no. seed for max wgt. |1246579|
    | IBRN(2)  | - search                         |8447766|
 
    +----------+----------------------------------+-------+
    | NQEV     | No. of entries in Sudakov table  | 1024  |
    | ZBINM    | Max bin size, z in spacelike bran| 0.05  |
    | NZBIN    | Max no. of z bins in spacelike br| 100   |
 
    +----------+----------------------------------+-------+
    | NBTRY    | Max. attempts to branch a parton | 200   |
    | NCTRY    | Max. attempts to decay a cluster | 200   |
    | NETRY    | Max. attempts, generate reqd mass| 200   |
    | NSTRY    | Max. attempts at soft subprocess | 200   |
 
    +----------+----------------------------------+-------+
    | ACCUR    | Precision, soft Gauss integration| E-6   |
 
    +----------+----------------------------------+-------+
    | RPARTY   | R-parity conservation in SUSY    | .TRUE.| 12  Rparty
 
    +----------+----------------------------------+-------+
    | SUSYIN   | Check if SUSY dataalready loaded |.FALSE.|
    | LRSUSY   | Unit for reading SUSY data       | 66    |
 
    +----------+----------------------------------+-------+
 
 
 
    Talk-to quantities added at CDF with Herwig version 6.4 (the first
   four are in v6.3):
 
    +----------+----------------------------------+-------+
    | OPTM     | Optimize phase space (28xx, 29xx)|.FALSE.| 15  Optm
    | IOPSTP   | No. of iterations if optimizing  | 10    | 15  Iopstp
    | IOPSH    | Events per iteration             | 1000  | 15  Iopsh
 
    +----------+----------------------------------+-------+
    | NEGWTS   | Allow negative weights           |.FALSE.| 09  Negwts
 
    +----------+----------------------------------+-------+
    | SYSPIN   | Switch on spin correls           |.TRUE. | 15  Syspin
    | THREEB   | Switch on 3-body decay mat els.  |.TRUE. | 15  Threeb
    | FOURB    | Switch on 4-body decay mat els.  |.FALSE.| 15  Fourb
    | LRDEC    | Unit to read spin or mat el inits| 0     | 15  Lrdec
    | LWDEC    | Unit to write spin or mat el init| 88    | 15  Lwdec
 
    +----------+----------------------------------+-------+
    | RLTIM(6) | Lifetime of top quark (secs)   | 5.534E-25| 08 Topltim
 
    +----------+----------------------------------+-------+
 
 
 
    Additional quantities in HERWIG talk-to:
 
                                                                talk-to
      Name        Description                     Default  Menu "name"
 
      TLOUT      time to terminate gracefully      *-1e07 . 09  Tlout
      RSTAB[21]   whether pizero is stable   ....   false . 08  Pizstable
 
      .....   used internally in HerwigModule.cc    0      09  No_shower
      .....    "        "              "            0      09  No_hadronization
      .....    "        "              "                   12  File_Readsusy
     
 
 
   Menu numbers and commands
       G   [none]
      01   Beam
      02   Sudakov
      03   Struc_Function
      04   Hards
      05   Shower
      06   Hadronization
      07   Underl_event
      08   Decays
      09   Generation
      10   Sm_par
      11   Masses
      12   Read_susy
      13   Zprime
      14   Prints
      15   Vers64
 
     -------------------------------------------
 
  
   Assorted notes.
 
     The exact "name" is required in the talk-to. For example, Help, Show,
   Q2pow do not work (get a brief message and the thing continues on).
     All Boolean variables in the explicitly Herwig talk-to are there as
   integers. So, for example, talk-to requires Bgshat set 1 ; the line 
   Bgshat set true  (or, .true.) gets no error message and does not change
   Bgshat.
     Given a name without arguments, the program gives a simple error message 
   and continues.
 
     For any quantity with a * in the default column above, the value given
   is as set in HerwigInterface.F (i.e., cdf people have changed a default
   value set by Herwig people). 
 
     Note (for anyone who worries about this) that a Herwig routine (hwuinc)
   explicitly sets mass(W-) = mass(W+), and similarly for all six quark masses.
   So we do not need to set both W+ and W-, both charm and anticharm masses,
   etc. Also, the top lifetime is applied to both t and tbar.
 
     There is a difficulty with inputting negative numbers in the talk-to.
   For PMBN3 and PMBK2, the magnitude must be input, and the program
   assumes the variables are negative. For example,  Pmbn1 set 9.00  will lead
   to PMBN1 = -9.00 in the HERWIG code.
 
     The minimum jet rapidity, YJMIN above, is set to -YJMAX, the negative
   of the maximum jet rapidity.
 
     For inputting powers of 10, one must use E (or e), not D or d. For
   example,  Pltcut set 1.E-10  works OK, but  Pltcut set 1.D-10  leads to
   Pltcut being set to 1. 
  
     On MAXER, the maximum number of errors. If the number of errors
   exceeds MAXER, the run ends gracefully, and the message "HWWARN
   CALLED FROM SUBROUTINE HWUFNE" appears. The default MAXER value is 100,
   which may not be large enough. Herwig people suggest it be set to
   number-of-events/100. If you have a tested executable and tcl file
   you could just set MAXER to a large value (1.E10, whatever). 
 
     On TLOUT, 'the time to terminate gracefully'. Herwig has had a way
   of nicely ending a run if the cpu time limit was approaching. In v6.4
   at Fermilab the two relevant routines, hwutim and timel, are dummies.
   To restore this feature, one must edit hwutim.f and timel.f and get
   them linked into the executable. There is a timel in library KERNLIB,
   see short writeup Z007, but that "is not reliable - especially on
   Linux".
 
     The option to write to disk a Sudakov table, and read it in, is not
   in the talk-to. The Herwig code still allows that option, but the cpu time
   saved is very small, so it is more sensible to recalculate the table for
   every run.
 
     The variable SUDORD controls whether the Sudakov form factors are
   calculated using one-loop or two-loop alphs-s (see pages 9 and 71 of the
   Herwig v 6 writeup). The default in Herwig is 1. In the CDF version that
   is changed (in HerwigInterface.F) to 2, because (i) then herwig is ~40%
   faster, (ii) it makes little difference, (iii) Mike Seymour (an author)
   uses 2.
 
     The variable MODBOS(I) controls the decay of the Ith gauge boson per
   event. Some intelligence, and maybe a test run, may be needed if anyone
   wants to change the default settings. The talkto currently allows only the
   decays of the first two gauge bosons to be changed. The decay of W's from
   top decay is unaffected by MODBOS settings. See the Herwig 6 writeup page
   14 for MODBOS information.
 
     The variable MAXEV, included in the first list above, is not used in
   CDF's Herwig.  
 
 --------------------------------------------------------------------------
 --------------------------------------------------------------------------
 
       Random Numbers, and Reproducing Events
       --------------------------------------
 
       The HERWIG package has its own random number generator, in 
   function hwrgen in hwrgen.f . That hwrgen.f is now not used.
   Instead, we use the random number machinery in the CLHEP library.
       If events are printed in Herwig (e.g., using  maxpr set 10) the
   print includes the random number seed pair for the event. That seed pair
   is also printed with any Herwig warning for an event. At present (July
   2002) what is printed is history, and is not the random number seed pair
   actually used. 
 
       Onto reproducibility. For example, we may want to reproduce event
   number 3846 of a run without rerunning all 3846 events. We need to know
   the random numbers at the start of event 3846. If the earlier run ended
   (e.g., crashed) on event 3846 then the file CdfRnStat.dat gives those
   random numbers, which can be input into the new run, using  talk
   RandomGenManager. But also a maximum weight must be input, using, in
   talk Herwig:
      Generation
        Maxwt set [value]
      exit
   where the value can be found in the earlier run log file as the last
   "New Maximum WEIGHT" value. All 16 decimal places can be used.
       Tests show that this procedure works with Herwig and QQ, but not
   with tauola (presumably tauola uses random numbers in initializing).
   (Also, does not work with Pythia).
 
   Footnote on random numbers (for anyone who cares).
       The random number generator uses a l'Ecuyer method, which combines
   two MLCG (multiplicative linear congruential) generators. See the nice
   "A review of pseudorandom number generators", F. James, Comput. Phys.
   Commun. 60, 329 (1990).
 
 --------------------------------------------------------------------------
 --------------------------------------------------------------------------
 
       User routines in Herwig, and Filtering Inside Herwig
       ----------------------------------------------------
 
       The Herwig writeup mentions user-provided analysis routines, hwabeg,
   hwaend, and hwanal (see page 6 of herwig v 6 write-up). These routines
   can provide a simple way to study generator-level quantities, and
   to filter events, i.e., select only certain events to procede with.
   Information is all in the common blocks, particularly in common/hepevt/... . 
   Dummy routines reside in the file herwig_i/HerwigInterface.F.
       To make any event selection easier, we have added another routine,
   hwanal0, with Herwig v6.4. Both hwanal and hwanal0 have an integer argument.
   If the integer is set to 0 in hwanal or hwanal0 the current event will be
   rejected. One could use hwanal0 to make a selection before hadronization,
   and/or hwanal for after hadronization - see the logic in generatorMods/
   HerwigModule.cc .
 
       A trivial hwanal.F could be
 
         subroutine hwanal(ihwcod)
 #include "HERWIG64.INC"
         integer ihwcod
         write (lhwout,10) nhep
 10      format ('  NHEP  ',i8)
         return
         end
 
   which will write the number of generator-level particles produced by
   Herwig for each event.
 
       A simple filtering hwanal0 could be
 
         subroutine hwanal0(ihwcod)
 #include "HERWIG64.INC"
         integer ihwcod
         integer ii,ib
         ib=0
         do ii=1,nhep
           if(idhep(ii).eq.5.or.idhep(ii).eq.-5) ib=1
         end do
 cc reject event unless there is at least one b quark 
         ihwcod=ib
         return
         end
 
       The above hwanal0 will not select events (if any) with b's from
   decays of higher-mass upsilons.
       Note that hwanal is called before any qq or tauola operation occurs.
   So, for example, filtering on J/psi from B decays in hwanal is not possible
   if qq is used.
       Also, be aware that if you elect to print (in Herwig) some events,
   lots of printing will occur if you are selecting a rare event type.
   For example, if   maxpr set 5   and the required event type occurs
   in 1% of the generated events, about 500 events will be printed.
 
 
 --------------------------------------------------------------------------
 --------------------------------------------------------------------------
 
       Structure Function Notes
       ------------------------
 
       The default parton distributions in Herwig are a MRST 1998 set,
   see the explanation in the Herwig 6.3 release note pg 2. This MRST
   set is in the Herwig code, i.e., does not use PDFLIB.
       To see which pdf a job used, search for PDFLIB in the log file.
   If present, that will tell you. If not present, search for
   STRUCTURE FUNCTION SET in the log file, the value there is nstru (see
   below).
 
       The structure functions used by Herwig are controlled by the
   variables nstru, autpdf(i), modpdf(i), i=1,2.
       If modpdf(i) < 0, autpdf(i) is ignored and nstru determines
   which of the built-in structure functions is used (see hwsfun.f).
   Allowed nstru values are 1 to 8, the default is 8, and the value can
   be changed in the talk-to. The pdf's for nstru = 1 - 5 are very old
   (~1991). The nstru = 6 - 8 were added in v6.3, are from MRST-1998,
   and are explained in the Herwig 6.3 Release Note.
 
       If modpdf(i) >= 0, nstru is ignored, and autpdf(i) and modpdf(i)
   determine the structure functions, which are taken from PDFLIB. Here
   autpdf gives author initials (approx.), and modpdf gives the set number
   (as defined by PDFLIB) for those authors. Some possible autpdf are 'MRS',
   'CTEQ', and 'GRV', with modpdf <= 100 (MRS) or <= 54 (CTEQ) or <= 14 (GRV).
   See the PDFLIB writeup (//consult.cern.ch/writeups/pdflib/), especially
   Tables 1 - 4. As of August 2001 the writeup is for version 8.04 (dated
   April 2000);  one should check the current Fermilab version.
 
       The talk-to allows modpdf(i) and autpdf(i) to be changed. It is assumed
   that i = 1 and i = 2 values are equal (OK for pbar-p). That is, talkto
   sets Autpdf, and then autpdf(i) = Autpdf, i = 1,2, and Modpdf similarly.
       If a non-existing (autpdf, modpdf) pair is asked for, PDFLIB defaults
   to MRST set 89 (which I think is the same as the Herwig default). PDFLIB
   always writes (to log file) what set it is using.
 
       Possible talk-to, inside  talk herwig , are:
 
   ## MRS set G:
    Struc_Function
     Autpdf set MRS
     Modpdf set 41
    exit
 
   ##CTEQ set 5L:
    Struc_Function
     Autpdf set CTEQ
     Modpdf set 46
    exit
 
 
 
 --------------------------------------------------------------------------
 --------------------------------------------------------------------------
 
       On Decays in the Generator versus in Geant - Pltcut
       ---------------------------------------------------
 
     For particles with lifetimes ~ E-10 s, the question arises of whether
   to do the decay in the generator or in Geant. If done in the generator,
   then (i) the decay products are available in the HEPG bank, (ii) the
   decaying particle cannot interact in the detector, (iii) if the decaying
   particle is charged, it leaves no track and does not bend in the magnetic
   field. If done in Geant, the converse holds.
     Given the particle lifetimes, it seems preferable for weakly-decaying
   strange hadrons to be decayed in geant, and B and C hadrons in the
   generator. Therefore, pltcut, the variable used in Herwig for making
   particles stable, has been changed (as of 26-Jan-2001) from 1.E-8 to
   1.E-11. This change also gives agreement with the qq default of not
   decaying K-shorts and weak-decay strange baryons. Pltcut has been added
   to the talk-to, so if desired the previous value (or any value) can be
   used.
 
 --------------------------------------------------------------------------
 --------------------------------------------------------------------------
 
       Changes Made in v6_4 by CDF
       ---------------------------
 
     Routines with the same names as tauola routines were added in
   the released v6_4. They were to facilitate the use of tauola. At
   CDF's request, those tauola routines have been moved to a dummy
   sub-library, and are not (should not be) linked. The herwig routine
   that calls these tauola routines has been put into HerwigInterface.F
   and changed so that all it does is stop the run - it should never
   be called.
 
     The coding for the new gauge boson pair production processes
   (IPROC = 2800-2816 and 2900-2916) introduced a severe complication in
   the setting of variables and parameters by a user. That complication
   is unnecessary, and CDF avoids it by making a few simple changes
   to the routine HWIPHS, which is then added to HerwigInterface.F.
 
 --------------------------------------------------------------------------
 --------------------------------------------------------------------------
 
 
 
 
 
 
 
 

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