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

The Signal

Examples of H+ → 3l+N

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

Cuts: Jet CutReject if the pT sum of the non top jets with pT > 50 GeV extends 300 GeV

Cut Results

L = 300 fb-1

5- Discovery Contour for H+

Set A

5- Discovery Contour for H+

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)