Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.qfthep04.sinp.msu.ru/2004/programm/qfthep04f/talks/qfthep_grappa.pdf Дата изменения: Fri Jul 9 17:04:22 2004 Дата индексирования: Mon Oct 1 20:01:32 2012 Кодировка: Поисковые слова: jet

Introduction of GR@PPA event generator
Soushi Tsuno Okayama U.

l l l l l

Introduction GR@PPA generator Automatic generation system Typical examples Summary
XVIIIth International Workshop on QFTHEP at St. Peterburg, Russia

Jun.18.2004


Introduction
GRACE :
1) An automatic source code generator to calculate Feynman diagrams. 2) Using CHANNEL/BASES/SPRING libraries. In principle, GRACE provides a framework of a phase space integration and (unweighted) event generation at once for any processes even in the higher order. GRACE was mostly used at LEP. But once we want to make the processes in the hadron collisions, we encounter huge number of diagrams, which consume much CPU time...

GR@PPA :
1) Event generator for hadron collisions. 2) Generic treatment of parton flavor in GRACE output code. 3) Previous work can be seen in bbbb process; CPC 151(2003)216. Event integration/generation time can be much faster than the automated processes of GRACE.
Jun.18.2004 XVIIIth International Workshop on QFTHEP at St. Peterburg, Russia


Schematic view
prototype

GRACE
feedback
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GR@PPA

user defined process user customizable running not so fast

l l l l

process specific optimized kinematics easy to use running fast

Suitable for study of specified signals rather than background estimation.
Jun.18.2004

Suitable for mass production of background or specified signals.

XVIIIth International Workshop on QFTHEP at St. Peterburg, Russia


Symbolic treatment
In hadron-hadron collision, single process (e.g. I(pp) several "subprocesses" at parton level. F(X)) consists of

t ot =

pert . IF

pert. I F

+
i

non- pert. X
2 j 2 2

=
I ,F

f I ( x1 , Q ) f I ( x 2 , Q ) dx1 dx

d

ij F

d

d

The subprocesses increase with the possible parton configuration in initial (e.g. p) and final (e.g. jet) state particles. Symbolical treatment of parton flavor allows us to calculate fewer subprocesses. Flavor is treated as one integration variable. ex. W + jets process : W+ + + + GRACE 1 jet : 288 2 jets: 4752 3 jets: 37264 4 jets: GR@PPA 6 diagrams 64 596 4456

Symbolic treatment of flavor(mass) & coupling.


GR@PPA generator
Process : p p(pbar) j W + k Z/* + l H + m + n jets + X; (j + k + l + m + n 6, j,k,l,m,n = 1,2,3,...) Current processes Boson(s) + n jets : W + n jets WW + n jets Z/* + n jets Z/* Z/ + n jets Z/* W + n jets QCD n bb t jets : jets bb t+j

(n (n (n (n (n

= = = = =

0,1,2,3,4) 0,1,2) 0,1,2,3,4) 0,1,2) 0,1,2)

Note that the bosons are decayed into fermions, so that the decay correlation is reproduced correctly.

(n = 2,3,4)

In tt proc., 3-body decay are considered, that is, calculating 6(7)-body kinematics.

Only LO is available now... Ever growing processes if users request!!


Performance (I)
s = 14 TeV at LHC (CTEQ6L, pT > 20 GeV , | | < 2.5, R < 0.4)
Cross section (pb) W-(e-e) + n jets ALPGEN MadEvent GR@PPA W+(e+e) + n jets ALPGEN MadEvent GR@PPA 0 3904(6) 3902(5) 3905(5) 0 5423(9) 5433(8) 5434(7) Number of jets 1 1013(2) 1012(2) 1013(1) 1 2 3 4 364(2) 136(1) 53.6(6) 361(1) 135.5(3) 53.6(2) 361.0(7) 133.8(3) 53.8(1) 2 3 4

1291(13) 465(2) 182.8(8) 75.7(8) 1277(2) 464(1) 182(1) 75.9(3) 1273(2) 467.7(9) 181.8(5) 76.6(3) at Workshop for MC4LHC2003

Jun.18.2004

XVIIIth International Workshop on QFTHEP at St. Peterburg, Russia


Performance (II)
CPU: Intel 3GHz on RedHat linux. CPU time (h:m:s) W+(e+e) + n jets free soft (g77) intel fortran (ifc) parallel 15 CPU 0 0:00:04 0:00:12 0:00:12 Number of jets 1 0:00:58 0:01:22 0:00:39 2 3 4 0:56:14 15:37:02 0:22:37 5:00:55 0:02:08 0:29:29 66:32:11

Note that the "parallel" does not mean the integration of each subprocess by each CPU. That DOES mean the integration of same process by multiCPU. These time is corresponding to the event generation of ~100,000 events. One can generate events by their PC.

Jun.18.2004

XVIIIth International Workshop on QFTHEP at St. Peterburg, Russia


Automatic generation system in GRACE at hadron collisions (in future)
GRACE has two generation cycles. User input Graph generation Makes graph structure based on the initial/final state particles(flavor) and coupling order. The extension will be done in this "graph generation" cycle. Ex. u-quark => proton, gluon => jet Code generation Makes (fortran) code based on this graph structure. If necessary, PDF is embedded into the kinematics.
Jun.18.2004 XVIIIth International Workshop on QFTHEP at St. Peterburg, Russia


Recipe for automatic "graph" generation
0) Start with current GRACE system. Initial and final state is well-defined. 1) For example, let's make "W + 1 jet" process. => pp ­> W + jet 2) Then, find all possible combinations of the sub-processes. Initial partons : (uD) , (dU) , (Du) , (Ud) , (ug) , (dg) , (gu) , (gd) , (Ug), (Dg) , (g Final partons : u , d , U, D, g 3) Now, consider "Charge" and "Parity" transformation: P (z ­> ­z) "base ME" (uD) ­> W+ + g (Du) ­> W+ + g + C CP ­ (Ud) ­> W­ + g (dU) ­> W­ + g then, DO diagram reduction except "base ME".
Jun.18.2004 XVIIIth International Workshop on QFTHEP at St. Peterburg, Russia

... (A) U) , (gD) ... (B)

"C", "P", & "CP" cover every combinations of type (A).


Rule of base ME : positive ( > 0) side. ­
initial +4/3 +3/3 +2/3 +2/3 +1/3 +1/3 0 0 0 ­1/3 (uu) (uD) (ug) (DD) (Dg) (ud) (g g ) (uU) (dD) (UD) ch + + + final

+n

W+ Z H

+m

u D g d U

+2/3 +1/3 0 ­ 1 /3 ­ 2 /3

(n) + (m)

Under W W W
Jun.18.2004

arge & particle/anti-particle conservations. 1 jet 3 2 jets 14 base MEs 3 jets 20
XVIIIth International Workshop on QFTHEP at St. Peterburg, Russia


Recipe of automatic "code" generation
1) Make kinematics. The dimension of numerical integration is N= 2 x1,x2 + 3 (n - 1 ) n -b o d y +1 + 1 (+ 1 ) . decay

ini. Flav. jets

2) Decide initial flavors by weight of PDF of the initial hadron. 3) Decide final state flavors if the graph has "jet". The "jet" flavors are characterized by the number of W bosons. (the jet flavor is decided by the weight of |CKM|2n, where n is # of W's.) 4) Find singularities. This generalization is not so difficult. That's it (!?).
Jun.18.2004 XVIIIth International Workshop on QFTHEP at St. Peterburg, Russia


SUSY process
We can also make SUSY processes. Ex. SUSY golden channel at Tevatron/LHC(?)

cascade

W/Z propagate

slepton propagate If you use GRACE, you have 23750 diagrams!!
Jun.18.2004

Note that decay correlation appears in 6-body ME.

XVIIIth International Workshop on QFTHEP at St. Peterburg, Russia


Summary
We have developed a newly event generator, GR@PPA, which is based on the automatic Feynman amplitude calculation system, GRACE. GR@PPA is developed for usability of GRACE system in hadron collisions. Both of them complementary feedback each other. Our recent activity: l Y.Kurihara et.al. Nucl.Phys.B654(2003)301; NLO+PS with no-double counting l H.Tanaka, Prog.Theo.Phys.110(2003)963; NLL partonshower We will provide the NLO+NLL generators on GR@PPA framework. We are also thinking the extension of GRACE system for hadron collisions. Remarks: http://minami-home.kek.jp/ http://atlas.kek.jp/physics/nlo-wg/
Jun.18.2004

for Minami-Tateya Group for GRACE for hadron collisions

XVIIIth International Workshop on QFTHEP at St. Peterburg, Russia