14-Jun-2000 Eric Lançon 1

Jetset vs Herwig… Once more

c quark effectJetset vs Herwig on same selected

events

14-Jun-2000 Eric Lançon 2

c quark effect

• Questions :

– Is there a difference in efficiency between Jetset and Herwig for the different types of quark flavour in final state ?

– Are the fitted masses sensitive to quark flavour content of final state?

14-Jun-2000 Eric Lançon 3

Selection efficiency - same 4f evtsJetset 34511 evts

Herwig35011 evts

Number of selected evts for mass analysis

1.5 % more selected evts for Herwig

Number of c quarks in event

Relative difference of efficiency Herwig / Jetset vs number of c quarks in event

No real effect

14-Jun-2000 Eric Lançon 4

DMW vs nb c quarks in eventAll EventsBackground

in reference but not in fitted samples (1093 evt/sample)

No quark flavour

selection

14-Jun-2000 Eric Lançon 5

DMW vs nb c quarks in eventCommon eventsBackground

in reference but not in fitted samples

No quark flavour

selection

14-Jun-2000 Eric Lançon 6

No c quark in event

Mmin

Nchmin

22)(

HerwigJetset

HerwigJetsetHerwigJetset

2 (Jetset-Herwig)

14-Jun-2000 Eric Lançon 7

No c quark in event

Slimmer Herwig jetsMmin Nchmin

14-Jun-2000 Eric Lançon 8

One c quark in event

Mmin

14-Jun-2000 Eric Lançon 9

Two c quarks in event

BtagMmin

14-Jun-2000 Eric Lançon 10

Variation with Nb of c quarks in evt<Mmin> vs nb of c quark in events

B evt tag and Nch1 vs nb of c quark in events

2 of distributions Jetset vs Herwig

The are the only variables with a linear variation

Typical shape

14-Jun-2000 Eric Lançon 11

Conclusions from c quark study

• 4q mass selection is 1.5% more efficient on Herwig events, – No real dependence with quark flavour

• The are differences between Jetset and Herwig for the c and non-c final states :– those differences tend to compensate

(except Btag, Nch1)

• The mass shift between Jetset and Herwig is independent of the number of c quarks in final state

14-Jun-2000 Eric Lançon 12

Jetset - Herwig comparison

• Same events in same Ntuple– after mass selection (including pairing)– 600K events each before selection– use events which correspond to same jet-

jet combination for jetset and herwig

• Look at :– global event properties– event/event properties

14-Jun-2000 Eric Lançon 13

Total Event energy

300 Mev more energy in Herwig

•Pb of Eflow calibration?•Need Herwig Z0 events

This explain the higher efficiency of the selection for Herwig ?

14-Jun-2000 Eric Lançon 14

Charged energy

300 Mev less charged energy in Jetset

14-Jun-2000 Eric Lançon 15

Electromagnetic energy

same electromagnetic energy for Jetset and Herwig

14-Jun-2000 Eric Lançon 16

Charge multiplicity

0.16 more charged particles in Jetset

14-Jun-2000 Eric Lançon 17

Multiplicity per jet

Nb of charged tracks/jet Nb of Eflow objects/jet

More objects/jet in Jetset

14-Jun-2000 Eric Lançon 18

E jet jetset/Herwig vs

14-Jun-2000 Eric Lançon 19

Em fraction in jet vs

No dependence

14-Jun-2000 Eric Lançon 20

Multiplicity in jets vs

No dependence

Nb of charged tracks/jet Nb of Eflow objects/jet

14-Jun-2000 Eric Lançon 21

Fitted mass : Herwig - JetsetMHerwig - Mjetset = 90 8 MeV

Before rescaling

14-Jun-2000 Eric Lançon 22

Fitted mass vs Fch and Fem

No real dependence / difference Jetset-Herwig

14-Jun-2000 Eric Lançon 23

Fitted mass vs charged multiplicity

Some dependence and difference Jetset-Herwig?

14-Jun-2000 Eric Lançon 24

and (Jetset-Herwig)

(Jetset-Herwig) (Jetset-Herwig)

Worst ? … see later

14-Jun-2000 Eric Lançon 25

(raw-generated) vs gen.

Z

generated

Herwig

Jetset(rec.-gen.) vs gen.

• Jetset jets are more inside• Herwig jets less biased at low

14-Jun-2000 Eric Lançon 26

resolutionBetter resolution for Herwig

(rec.-gen.)

<> = -0.019 0.009RMS = 6.22

<> = -0.006 0.008RMS = 5.51

14-Jun-2000 Eric Lançon 27

after fit

(fit-gen.) vs gen.(fit-rec.) vs gen.

Fit does not correct for the difference in reconstruction at low angle between Jetset and Herwig

14-Jun-2000 Eric Lançon 28

Delta fitted mass vs Nb jets in Barrel

An effect when NO jet in barrel ?

MJetset - MHerwig vs number jets in barrel

14-Jun-2000 Eric Lançon 29

Delta fitted mass vs gen. Min.

MJetset - MHerwig vs Min( jet-gen.)

14-Jun-2000 Eric Lançon 30

Sum of Pt2

Jets JetParticles

TP 2

Wider Jetset jets

14-Jun-2000 Eric Lançon 31

Delta fitted mass vs Sum of Pt2MJetset - MHerwig vs Sum Pt2

Strong dependence

14-Jun-2000 Eric Lançon 32

Jet-jet angle

Jet1

Jet2

Herwig Ws are more ‘opened’

= -0.32 0.04 deg.

Strongly related to W mass

14-Jun-2000 Eric Lançon 33

Delta jet-jet angle vs (jetset-Herwig) vs number jets in barrel

(jetset-Herwig) vs W gen

No real variation

14-Jun-2000 Eric Lançon 34

Conclusions

• More reconstructed energy (300 MeV) with Herwig

• More charged energy in Herwig (300 MeV)– Calibration of Eflow? Herwig Z0 events

needed– Explain difference in efficiency

• Larger particle multiplicity in Jetset• Jetset jets are wider

– More losses are low/high

• Jetset resolution worst than Herwig• Jet-Jet angle larger for Herwig than JetsetWhich of the two MC data prefer?

14-Jun-2000 Eric Lançon 35

The 18 Variables

• Global properties of the event– # charged tracks in an event Nch

– charged/total energy Fch

– em E fraction in event Fem

• Parton-shower related– Minimum jet mass Mmin

– Maximum jet mass Mmax

– Sum of Pt2 wrt jets SumPT2

– Sum of Angles Ch. Part. wrt Jet 1,2

SumAng12

Jets JetParticles

TP 2

2,1arg

,JetsParticlesedCh

JetParticleCos

14-Jun-2000 Eric Lançon 36

The 18 Variables (Contd.)

• Hadronisation related– minimum # object in a jet Nobjmin

– minimum # of charged track in a jet Nchmin

– Max. e.m. energy fraction in 1 deg. cone

Max-em-frac

– Max. charged track energy fraction Max-ch-trk

– # charged particles in leading E jet Nch1

– # charged particles in lowest E jet Nch4

– # objects particles in leading E jet Nobj1

– # objects particles in lowest E jet Nobj4

– Sum Jets Btag SUMPROB

– QIPBTAG event prob. PROBE

Jets

jetobPrlog

10