Discovery potential for H + decaying to SUSY particles 30 March 2005, ATLAS Higgs Working Group...
-
Upload
imogene-gibson -
Category
Documents
-
view
213 -
download
0
Transcript of Discovery potential for H + decaying to SUSY particles 30 March 2005, ATLAS Higgs Working Group...
Discovery potential for H+ decaying to SUSY particles
30 March 2005, ATLAS Higgs Working Group Meeting, CERN
Christian Hansen
Uppsala University
Nils Gollub
Uppsala University
Ketevi Assamagan
BNL
Tord Ekelöf
Uppsala University
Bjarte Mohn
Bergen University
Introduction
Not possible to cover low tanβ region with SM decays Try susy decays
Discovery Potentials for H+ (from 2→2 processes) when
H+ → SM particles
D. Cavalli et al., “Search for H+ decays”, ATL-PHYS-94-053K. Assamagan, “The Charged Higgs in Hadronic Decays With the ATLAS Detector”, ATL-PHYS-99-013K. Assamagan, “The Hadronic decay of a Heavy H+ in ATLAS”, ATL-PHYS-2000-031
ATLAS 300 fb-1
Introduction (cont)
The channel
with
where N = invisible final state particles and with
has been studied with CMSJET.
M. Bisset, F. Moortgat and S. Moretti, “Trilepton+top signal from chargino-neutralino decays of MSSM charged Higgs bosons at the LHC”, hep-ph/0303093 v2 1 Oct 2003
Introduction (cont) CMS’ result : Parameter Set A :
• M2 = 210 GeV
• μ = 135 GeV
• ml̃R = 110 GeV
• mg ̃ = 800 GeV
• mq = 1 TeV
where soft slepton and squark masses are degenerate for all generations, where ml̃R
= ml̃L and where M1 = 3/5tan2θWM2
hep-ph/0303093 v2 1 Oct 2003
We have now performed a similar study using ATLFAST
Event Production • Used HERWIG for event production and ATLFAST for fast detector
simulation (ATLAS 7.0.3)
• Have MC data for tanβ = 3, 5, 8, 10, 15, 20, 25, 30, 35, 40 and mA = 200, 220, 230 250, 300, 350, 400, 450, 500 GeV, in the Parameter Set A
Process Number Events Produced
gb → H+t, H+ → χχ → 3l+N
and t → bqq
4·105 for each (tanβ, mA )
gg → tt 108
gg → ttZ 2·107
gg → tth 107 for each (tanβ, mA )
gg → χχ 107 for each (tanβ, mA )
gg → q, g 106 for each (tanβ, mA )
Signal
SM Bkg
SUSY Bkg
Signal Cross Section; NLO from
SM-Bkg Cross Section;CS(tt) = 737 pb (NLO)CS(ttZ) = 431 fb (LO from Herwig)
SUSY-Bkg Cross Section; (LO from Herwig)
Cross Section
Tilman Plehn, “Charged Higgs boson production in bottom-gluon fusion”, PHYSICAL REVIEW D 67, 014018 (2003)
• Signal Branching Ratio: H+ is forced to decay to χχ which are forced to decay to 3 leptons and a number N of undetectable particles
• The top is forced to decay hadronically e.g. for tanβ = 20, mA = 350
BRTOT = BR(H+→ χχ →3l+N)*BR(t→bqq) = 0.26*2/3 = 0.18
Signal Branching Ratio
Cuts: 3 Lepton Cut Events must have exactly three isolated leptons (e or μ) with
pT > 20, 7, 7 GeV, all with |η| < 2.4
Cuts: 2l Mass Cut
The invariant mass of the two same flavor, opposite sign leptons have to be less than 63 GeV
• χ0j → 2 same flavor, opposite sign leptons + one or more
undetectable particle(s)
• Out of the three isolated leptons at least 2 are required to have same flavor and opposite sign
• The inv. mass of these two is kinematically constrained. – E.g. if χ0
j only decayed to one undetectable particle (χ01) it follows that
– If tanβ = 10 and mA = 350 GeV we have m(χ01) = 78 GeV, m(χ0
2) = 131 GeV and m(χ0
3) = 146 GeV Mllmax = 51 (68) GeV for j = 2 (j = 3)
• If third lepton has same flavor, the biggest Mll are used for the cut 10 < Mll < 63
Cuts: 2l Mass Cut
The invariant mass of the two same flavor, opposite sign leptons have to be less than 63 GeV
Signal events, gb → H+t All Backgrounds
Cuts: 2l Mass Cut
The invariant mass of the two same flavor, opposite sign leptons have to be less than 63 GeV
Cuts: Top Cut •Must have at least three jets with pT > 20 GeV in |η| < 4.5
•Among these select 3 top jets by min( |mjjj – mt| ) < 35 GeV
•Among these select 2 W jets by min( |mjj – MW| ) < 15 GeV
Cuts: Jet CutReject if the pT sum of the non top jets with pT > 50 GeV extends 300 GeV
Signal events, gb → H+t All Backgrounds
Conclusions and Future Work
• Our paper is currently an ATLAS communication: (ATL-COM-PHYS-2005-008)Paper
More Sets • More MSSM parameter sets need to be analysed for a more general conclusion
Contour • The 5- significance contour for H+ through H+ → χχ encloses major part of intermediate tanβ region
CMS • Our discovery region is about same size as that obtained for CMS. Different shapes, due to– Different cuts– Different used cross sections (We: NLO for signal & tt and LO for the rest. They: LO for all)– Different detector descriptions (ATLFAST vs. CMSJET)