University of Iowa

Status qq->H->zz with fully simulated calorimeters

Alexi MestvirishviliFIU Feb. 2004

Event generation and reconstruction

PYTHIA 6.2, CMSIM version 127, ORCA version 7.3.0, ROOTMAKER

Initial and Final state radiations are switched on

No Pileup (for the time being)

PYTHIA 6.2, CMSIM version 127, ORCA version 7.3.0, ROOTMAKER

Initial and Final state radiations are switched on

No Pileup (for the time being)

No tracker was simulated, particle level analysis was done

on the generator particles. This concerns mainly Z e+ e-

reconstruction.

No tracker was simulated, particle level analysis was done

on the generator particles. This concerns mainly Z e+ e-

reconstruction.

Event samples

Z+jets was not simulated. Preliminary analysis with CMSJET shows total negligence of this kind of background.

Z+jets was not simulated. Preliminary analysis with CMSJET shows total negligence of this kind of background.

Signal eventsqqH (Pythia proc. 124 (WW fusion)) 300, 350 and 500 GeV was considered as H mass

Background eventsDirect ZZ production (Pythia proc.22) WWZZ (Pythia proc.76)

One of Z decays to e+ e-, another Z to neutrinos, thus generating large missing ET

Additional background -- ttbar events where each t quark decays to Wb and each

W decays to two leptons (e+/e-) .Central jets veto was not used due to the

ISR and FSR switched on.

Signal eventsqqH (Pythia proc. 124 (WW fusion)) 300, 350 and 500 GeV was considered as H mass

Background eventsDirect ZZ production (Pythia proc.22) WWZZ (Pythia proc.76)

One of Z decays to e+ e-, another Z to neutrinos, thus generating large missing ET

Additional background -- ttbar events where each t quark decays to Wb and each

W decays to two leptons (e+/e-) .Central jets veto was not used due to the

ISR and FSR switched on.

Jets pre selection

H M(300GeV)

H M(500GeV)

WW->ZZ

H M(350GeV)

ZZ

ttbar

Multiplicity

Jets in the cone 0.5 rec. with iterative algorithm were used.Jets with ET 20GeV must be well within CMS acceptance |

| 5. Any jet closely associated to the leptons were removed from the jet list. Jet isolation condition:- no any

object around the jet in the cone with R=0.5

Pseudorapidity

Tag jets selection

|j1-j2|>4; j1· j2 < 0;|j1-j2|>4; j1· j2 < 0; Tag jets pair combinations

Tag jets pair combinations

H M(300GeV) H M(350GeV)

H M(500GeV) ZZ

WW->ZZ ttbar

Jet pair comb.

%

Tag jets selectionTag jets

Pseudorapidity

Tag jets

Pseudorapidity

H M(300GeV) H M(350GeV)

H M(500GeV) ZZ

WW->ZZ ttbar

Pseudorapidity.

? ontag jets selection

Restriction on ET20GeV cuts out 17 % of events with pair of forward jets

Restriction on ET20GeV cuts out 17 % of events with pair of forward jets

Red arrows indicate forwardregion occupied with the highenergetic jets and ET<20GeVBlue arrow – central region With low energetic jets and ET<20GeV. May be better cutOn E rather tan on ET?

Red arrows indicate forwardregion occupied with the highenergetic jets and ET<20GeVBlue arrow – central region With low energetic jets and ET<20GeV. May be better cutOn E rather tan on ET?

ET Cut valueET Cut value

Lepton Selection and cut on Missing ET

Leptons (e+ e- ) were selected from generator particles data. Lepton cuts:

||<2.5, ET > 20GeV, |M(e+ e-)-M(Z)|<15GeV,

j,min +0.5< l< j,max-0.5

(Leptons are between tag jets)

Requirement for reconstructed Missing ET > 50GeV

This cut along with others totally eliminates Z+jets events

Leptons (e+ e- ) were selected from generator particles data. Lepton cuts:

||<2.5, ET > 20GeV, |M(e+ e-)-M(Z)|<15GeV,

j,min +0.5< l< j,max-0.5

(Leptons are between tag jets)

Requirement for reconstructed Missing ET > 50GeV

This cut along with others totally eliminates Z+jets events

Number of Events, CS, Integrated luminosity

Process N. of gen. Events

CS(fb) Int. lum. (fb-1)

H (M=300GeV)

44795 1.43 3.13x104

H (M=350GeV)

29232 1.12 2.61x104

H (M=500GeV)

23093 0.47 4.9x104

WW-> ZZ 35459 2.32x10-2 1.53x106

ZZ 24298 48.3 5.03x102

t tbar 9676* 7.27x103 3.5x10-2* -- statistic needs to be increased

Acceptance for individual process after all the cuts

Process Acceptance

H (M=300GeV) 24.0%

H (M=350GeV) 26.7%

H (M=500GeV) 31.6%

WW->ZZ 18.8%

ZZ 0.13%

ttbar 0.021%*

*-- Since tracker was not simulated and b jet tagging wasn’t used, all the events with the tag jets in the region covered by tracker were dropped. This assumes 100% efficient B jet vetoing.

Number of events

Process

Number of events for different

Value of LCH Int. Lum.

60fb-1 100fb-1

H (M=300GeV) 21 34

H (M=350GeV) 18 30

H (M=500GeV) 9 15

WW->ZZ 0.26 0.43

ZZ 4 6

ttbar 92 153

Significance and LHC luminosity again

ProcessSignal significance

60fb-1 100fb-1

H (M=300GeV)

2.1 2.7

H (M=350GeV)

1.8 2.4

H (M=500GeV)

0.92 1.2

ProcessLHC IL for 5 sign. (fb-1)

H (M=300GeV) 330

H (M=350GeV) 442

H (M=500GeV) 1860

5 significance level

60fb-160fb-1

100fb-1100fb-1

Conclusions

Even WW ZZ has very same topology as signal events, their contribution to the background is almost negligible due to the small CS.Main background comes from direct ZZ and t tbar because of huge production CS. Even WBF processes has second largest CS after Higgs gg production scheme, it will be necessary few years of running to observe H produced in WW fusion and decayed to this particular channel.

Even WW ZZ has very same topology as signal events, their contribution to the background is almost negligible due to the small CS.Main background comes from direct ZZ and t tbar because of huge production CS. Even WBF processes has second largest CS after Higgs gg production scheme, it will be necessary few years of running to observe H produced in WW fusion and decayed to this particular channel.