Leonid G. Levchuk -- 8th Annual CMS/RDMS Meeting, Dubna, Russia

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On the possibility to observe with CMS

a moderately heavy Higgs decaying via HZZll

Leonid G. Levchuk

Kharkov Institute of Physics & Technology

2Leonid G.Levchuk – 8th Annual CMS/RDMS Meeting, Dubna, Russia 05 Dec 2003

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TTMotivationMotivation

Search for physics suggesting importance of hadron calorimetry

HZZll has ~6 times greater BR

compared to HZZ4l

Some light could be shed on physics

of ZZ interaction

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TTPrevious studiesPrevious studies

N.Stepanov, CMS-TN/93-087 (1993); N.Stepanov and S.Abdullin, CMS-TN/94-178 (1994); I.Gaines, D.Green, S.Kunori, J.Marrafino, J.Womersley, and W.Wu, CMS-TN/95-84 (1995) heavy (MH>500 GeV) Higgs observability via HZZll was studied; irreducible background (IB) due to ZZ/ZW production thwarts H observation

L.Levchuk, 6th annual RDMS CMS collaboration meeting (MSU, Moscow, 2001); L.Levchuk, D.Soroka, P.Sorokin, V.Trubnikov, and S.Zub, 7th annual RDMS CMS collaboration meeting (IHEP, Protvino, 2002) extension to MH=200250 GeV; ways to eliminate IB

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Simulation toolsSimulation tools

PYTHIA (Ver. 6.158) CMSJET (Ver. 4.703)

Z+jets

ZZ

ZW

Background contributionsBackground contributions

_

t t

irreducible irreducible backgroundbackground

irreducible irreducible backgroundbackground

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1-st level (“tentative”) cuts:

ETmiss > 60 GeV, 2 leptons such that : |l| < 2.4,

pTl >20 GeV, PT

ll > 40 GeV, |MZ-Mll| < 5 GeV

At threshold ofAt threshold of HZZ decay, decay,

(MTZZ 2MZ)1/2 | |

At threshold ofAt threshold of HZZ decay, decay,

(MTZZ 2MZ)1/2 | |ll miss

T TP P

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““Loose” cuts (“A”)Loose” cuts (“A”)

1-st level (“tentative”) cuts:

ETmiss > 60 GeV, 2 leptons such that : |l| < 2.4, pT

l

>20 GeV, PTll > 40 GeV, |MZ-Mll| < 5 GeV

Elimination of the IB:

No b-jets:

Nb-jets=0

<90 >120 >120, ,ll miss ll j miss jT T T T T TP P P P P P

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““Hard” cuts (“C”)Hard” cuts (“C”)

1-st level (“tentative”) cuts with loosed cut on ETmiss :

ETmiss > 40 GeV, 2 leptons such that : |l| < 2.4,

pTl >20 GeV, PT

ll > 40 GeV, |MZ-Mll| < 5 GeV

Elimination of the IB:

No b-jets:

Nb-jets=0

Extra criteria (I):

Extra criterion (II) – selection of single-jet events:

Nj=1 , 1.0<|j| < 4.5, pTj >40 GeV

<90 >120 >120, ,ll miss ll j miss jT T T T T TP P P P P P

1 2 1 2

>60 >90,l l l lT TP P P P

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Current status and plans for nearest future

Current status and plans for nearest future

Publication of the preliminary results L.G.Levchuk, P.V.Sorokin and S.Kunori, “On the possibility to observe

a heavy Higgs via HZZll decays at CMS”, CMS Note (or CMS_IN?) – in preparation

Search with “fast” MC for kinematical criteria providing a better signal/background ratio

In case of success, preparation for “detailed” (OSCAR or CMSIM) simulation & ORCA reconstruction

Check for reliability and degree of the IB suppression Simulations with a generator other than PYTHIA (HERWIG, …?) Simulations of the non-resonant ZZ/ZW production accompanied by

high-pT jets based on 23 hard processes (COMPHEP, …?) NLO calculations of the non-resonant ZZ/ZW production (MC@NLO_2.2

[http://www.hep.phy.cam.ac.uk/theory/webber/MCatNLO], …? )

Consideration of the 23 Higgs production A generator for a combined treatment for both WBF and QCD 23

mechanisms of Higgs production – under development