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H -> ZZ* Process

Goal of the group

Group Contacts

Group Members

  • Experiment: Chiara Mariotti, Cristina Botta (Torino), Gurpreet Singh Chahal (Bari), Marek Schoenherr (Dresden), Mario Pelliccioni (Torino), Sara Bolognesi (CERN)
  • Theory: Everybody who wants to contribute

Plan of the Activity (both Higgs signals and SM backgrounds)

  • differential K-factor
  • overview of background determination methods (data-driven, non-data driven)
a) sidebands by extrapolating the bkg from a control region (measured with data) to a signal region by the MC prediction 
b) ABCD method:  definition A,B,C,D control region based on two observables (isolation, impact parameter, for example for Zbb evaluation).
Strategies for the evaluation of ZZ and Zbb already defined but the results need to be compared if using NLO monte carlo instead of LO. 

  • list of LO/NLO Monte Carlo's
CMS: is going to produce PYHIA6 and POWHEG+ PYTHIA6; as soon as samples are available we will compare the main kinematical distribution LO vs NLO. Evaluation of cross section with POWHEG
is on going.  I started to play by myself with POWGEG (with the help of pietro govoni) to evaluate the differential k factor.  Hope to provide results soon. 
ATLAS:  need to check asap with stathes
  • wish List for theorists

Common cuts definition between ATLAS and CMS

  • 4l final state:
* >=3 leptons with pT>5 with |eta|<2.5
* >= 2 leptons with pT>10 with |eta|<2.5
* Electrons are required to satisfy pT>5 in |eta|<2.5 while muons are required to satisfy pT>5 in the barrel 
(|eta|<1.2        and pT>3 + p>9 in the endcap (1.2<|eta|<2.4). 
* Loose identification criteria on leptons  with opposite charge and matching flavour.
* loose isolation on the 4 leptons (sumpT/pT_l <0.7)
* best di-candidate selection (close of Z nominal mass) 
* m1ll > 40, m2ll>12, m4l>100

  • 2l2nu:

*  electrons: ID criteria + pT>20 and !eta!<2.5
*  muons: ID criteria + pT>20 and !eta!<2.5
*  jets: anti-kt in 0.4 + pT>25 and !eta!<2.5
*  exactly 2 electrons/muons opposite charge
*  76 < mll < 106 
*  events with btag jet rejected
*  for mh < 260: deltaphi_ll > 1
*  for mh < 280: MET > 66,  deltaphi_ll < 2. 64
*  for mh > 280: MET > 82,  deltaphi_ll  < 2.25

  • 2l2jet:
* electrons: ID criteria + pT>20 and !eta!<2.5
* muons: ID criteria + pT>20 and !eta!<2.5
* jets: anti-kt in 0.4 + pT>25 and !eta!<2.5
* exactly 2 electrons/muons opposite charge
* 76 < mll < 106 
* MET < 50
* at least 2 jets 
* for the two jets with highest pt: 70 < mjj < 105
* mh>=360: 
    -- pt jets >50
    -- deltaphi_jetjet < pi/2,   deltaphi_ll  < pi/2

Available Tools





-- ReiTanaka - 02-Oct-2010

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Topic revision: r4 - 2011-06-10 - NicolaDeFilippis
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