1. EvtGen at Belle Akimasa Ishikawa KEK, IPNS 21 Jan 2005

2. EvtGen  Standard generator at Belle. Both BBbar and continuum events are generated with EvtGen. Version 00-10-07++ is used. To be updated coming version.  EvtGen package is included in Belle library. Anybody can easily modify EvtGen for private purpose by checking out the source codes from Belle CVS. In order to load EvtGen from BASF (Belle AnalysiS Framework), shared object module “evtgen” is created. basf<<EOF path create main path add_module main evtgen ….. EOF

3. Decay Table  We use modified DECAY.DEC and evt.pdl. Only includes tree level b  c decays. Other rare decays, which proceed through b  u, s, d, annihilation or exchange diagrams, are separated to study rare decay backgrounds. Decay table is basically tuned with PDG and HFAG results and Theory.  Both exclusive and inclusive measurements. D 0, D + and Ds spectra are tuned by inclusive measurements.  Only possible at e+e- B-factory Total width difference between B0 and B+ is introduced.  ex. BF(B+  Xl ) /BF(B0  Xl )=1.08 Some particles are added to evt.pdl  ex. higher N and charmed baryons and X(3872) assuming hc’. Please find the decay tables at http://www.belle.kek.jp/~akimasa/decaytable/2003/

4. Branching Fractions  7 inclusive decay modes are considered.  Determined with inclusive measurements BF(B  lepton X)=10.9% BF(B  Ds X)=10.5% etc. BFB0B+Average DXlnu0.2090.2770.218 DXtaunu0.0240.0260.025 ccX0.0240.0260.025 DsX0.1010.1090.105 DDX0.0870.0830.085 DX0.4580.4360.447 BaryonX0.0970.0930.095 Total1.000 total width difference

5. D0, D+ and Ds spectra  Belle has measured inclusive D meson spectra. B(B  DsX)=11.7+-0.1(stat)+-1.1(syst)+-2.9(Ds   ) % B(B  D0X)=66.3+-0.2(stat)+-2.1(syst)+-1.5(D0  K  ) % B(B  D+X)=24.0+-0.2(stat)+-0.9(syst)+-1.4(D+  K  ) % Before After Very Very Preliminary D0 70.5% D0 68.2% D+ 28.3% D+ 26.8% Ds fixed to 10.5% Next Step  inclusive charmonia and charmed baryons.  flavor specific D mesons and charmed baryons

6. Pythia, continuum production  Rolf Seuster developed Pythia interface. Now in EvtGen. Better representation for heavy flavor fragmentaion.  Charm fragmentaion tuning with D0 and Ds* mesons. We use Bowler function D0 prefers pure Bowler(r Q =1) but Ds* prefers pure Lund(r Q =0) r Q =1 gives minimum combined  2 /ndf. We choose r Q =1. This analysis was done before obsevations of Ds(2317) and Ds*(2457), so we need to check again. Red : Bowler Solid : Lund Dot : data D0 Ds*

7. Event shape  Tuning of event shape is also performed. 19 event shape variables are put into   and search for minimum by changing the parameters Q 0, Q’: termination of parton shower,  q : transverse momentum,  QCD, Lund a and b.  Thrust, cosThurst, Thrust major and minor, oblateness, Planarity, heavy and light Jet Mass, Jet Broadening W and T, Sphericity, Aplanarity, R1, R2, R3, y23, y24, CPar, DPar BelleEvtGenpythia Q00.51.0 Q’0.3 0.8 qq 0.420.36  QCD 0.3 A0.320.3 B0.620.58

8. Photos  We only use photos for semi-leptonic and leptonic decays.  However radiative effect is large especially two body decays, B  .  We need to turn on photos for all decay modes. events  K+K- without photos8000+-907577+-87 with photos7474+-877282+-85 difference6.6+-1.5%3.9+-1.6% B   EE M bc EE

9. Interference Weight  Elisabetta Barberio, who is one of the photos authors, pointed out that interference weight for multi body decay W multi is not introduced in EvtGen except for two body particle-anti-particle decay, such as B    W multi should be introduced.

10. Speed, Random Generator  Speed EvtGen is about 2.5 times slower than qq98.  350Hz and 300Hz for BBbar and uds events on Pentium3 1266MHz, respectively  30fb -1 /day and 11fb -1 /day.   33days and 90days to generate 1/ab MC (about 3x data we have).  Need faster CPU or parallel production.  True random number generator board for parallel production Pick up thermal noise in semiconductor. Distribute random number via network. About 7M single precision random numbers/sec 800~900 random numbers to generate BBbar events.  ~8kHz for BBbar events  600fb -1 /day A dozen random boards are enough even at Super-B factory. Cost $6000/board http://www3.toshiba.co.jp/power/techno/secret/random/index_j.htm In japanese

11. Platform  OS/compiler Linux/gcc2,gcc3  We will/should use PC Linux to get enough computing power. Solaris/gcc3, SunWS5.0 cc  SunWS5.0 cc does not support template member function, so we cannot compile EvtGen with it. Need to switch to Sun one studio 8/9. FreeBSD/gcc2, gcc3  Some institute at Belle used.  We want to try these compiler. PGI compiler Intel C/C++ Compiler

12. What is needed (my opinion)  Decay models should allow that lower resonance decays to higher resonance. It is possible if both resonances have large width. Ex. K1(1270)  K0*(1430) .  Decay models for Higgs mediated B  D  and B   decays. One of the inportant decay mode at Super B-factory.  Parity (and C-Parity?) should be defined in evt.pdl.

13. Summary  EvtGen is standard generator at Belle.  We improve the decay table by measuring D meson spectra. Next target is charmonia and charmed baryons. Next to Next is flavor specific D mesons and charmed baryons.  We also tune the continuum production with D mesons and event shapes.  Photos should be applied to all decay modes.  Interference weight should be introduced.  EvtGen is not so fast but enough processing speed is possile with parallel production with random generator allows

14. Back up

15. History qq98 EvtGen 1999 2000 2001 2002 2003 2004 2005  ~2000: qq98 for both signal/BG study.  End of 2000: EvtGen is implemented to make a better flavor tagging tool and study CPV in b  ccs.  2001: Observation of CPV.  2001~2003 some analyses used EvtGen for signal study (B  , B  Kll, b  ul etc.).  2004: start background MC mass production with EvtGen. Signal MC Background MC qq98 EvtGen