BSM Higgs Boson Searches with ATLASmoriond.in2p3.fr/QCD/2012/SundayAfternoon/Kroseberg.pdfDecays to γγ, WW, ZZ, Zγ Here: focus on γγ (enhanced w.r.t. SM for light(!) Higgs) arXiv:1101.0593v3

J. Kroseberg BSM Higgs Searches with ATLAS Moriond QCD 2012 1

Jürgen KrosebergUniversity of Bonn

on behalf of theATLAS collaboration

BSM Higgs Boson Searches with ATLAS

Rencontres de Moriond - QCD and High-Energy Interactions

La Thuile , March 10-17 2012

J. Kroseberg BSM Higgs Searches with ATLAS Moriond QCD 2012

Closing in on the SM Higgs Boson

2

see Ralf Bernhardʼs talk

ATLAS-CONF-2012-019


Closing in on the SM Higgs Boson

3

see Ralf Bernhardʼs talk

Really?

ATLAS-CONF-2012-019


What if...

4

… the Higgs-boson couplings are different from the SM ones?… this is only one of several SUSY (MSSM)Higgs bosons?… an even more complex Higgs sector is realized in nature?


What if...

5

… the Higgs-boson couplings are different from the SM ones?… this is only one of several SUSY (MSSM)Higgs bosons?… an even more complex Higgs sector is realized in nature?

fermiophobic Higgs

MSSM neutral Higgs

Charged Higgs H+

Doubly charged H++

e.g.

e.g.

e.g.


6

Fermiophobic Higgs

arXiv:1201.3084v1


Fermiophobic H→γγ : Benchmark Scenario

7

Decreased coupling to some or all fermions in Higgs doublet and triplet modelsHere: simple benchmark scenario without any Higgs-fermion coupling and SM coupling to gauge bosonsProduction via Vector-Boson Fusion and associated VH productionDecays to γγ, WW, ZZ, ZγHere: focus on γγ (enhanced w.r.t. SM for light(!) Higgs)

arXiv:1101.0593v3

ATLAS-CONF-2012-013 (4.9 fb-1)


Fermiophobic H→γγ : Analysis

8

high pTt

low pTtselect events with 2 isolated photons with pT > 40/25 GeVdi-photon mass:100 GeV < mγγ < 160 GeV9 analysis categories based on

presence of γ conversionsγ calorimeter impact pointpTt: di-photon transverse momentum orthogonal to the di-photon thrust axis in the transverse plane

signal mγγ model: “Crystal Ball” + wide Gaussianbackground mγγ model:exponential

ATLAS-CONF-2012-013 (4.9 fb-1)


Fermiophobic H→γγ : Exclusion Limits

9

observed mH exclusion:[110.0,118.0], [119.5,121.0]expected mH exclusion:[110.0,123.5]

ATLAS-CONF-2012-013 (4.9 fb-1)


Fermiophobic H→γγ : Exclusion Limits

10

observed mH exclusion:[110.0,118.0], [119.5,121.0]expected mH exclusion:[110.0,123.5]

largest excess from BG-only hypothesis at mH =125.5 GeV1.6σ (with look-elsewhere)

ATLAS-CONF-2012-013 (4.9 fb-1)


11

Neutral Higgs


MSSM Higgs Sector

12

MSSM: minimal super-symmetric extension of SMrequires 2 Higgs doublets → 5 Higgs bosons:Ф = h, H0, A ; H+,H- number of parameters can be reduced with additional assumptions, e.g. to mA, tanβenhanced couplings to b and tau in large regions of the parameter space (in particular high tanβ)

multivariate identificationJ. Kroseberg BSM Higgs Searches with ATLAS Moriond QCD 2012

τ-Lepton Decays

13

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+,01!#$()2!7*#$!•  Q2<2332J"0/"64"&1";$"01;4"06DR"

τ decay

QCD jet

hadronic tau decays:narrow, collimated jetisolated energy deposits and tracks large electromagnetic component low track multiplicity (1 or 3)high leading-track momentum fraction

full reconstruction

with “missing mass calculator” (MMC)

effective mass

inv. lepton-ETmiss mass


MSSM Higgs → ττ : Selection

14

τlτl τlτh τhτh2-τhad trigger2 τhad with pT > 45 GeV andpT > 30 GeVopposite chargeslepton vetoETmiss > 25 GeV(QCD)

hadron-hadronisolated e / µ with pT > 25 / 20 GeVexactly one τhad with pT > 20 GeVopposite chargesdilepton veto (Z, top)ETmiss > 20 GeV (QCD)mT < 30 GeV (W)

1 isolated e with pT > 25 GeV1 isolated µ with pT > 20 GeVopposite charges(sum of lepton pT and ETmiss) < 120 GeV,ΔΦe,µ > 2.0 GeV(top, WW, ZZ)

lepton-hadronelectron-muon

visible mass

invariant mass of visible τ decay products

(NIM A654 (2011) 481)

ATLAS-CONF-2011-132 (1.06 fb-1)

ττ mass reconstruction


MSSM Higgs → ττ : Background Estimation

15

Use mainly data-driven methods, e.g.Z/γ* →ττ from τ-embedded Z/γ* →μμ dataQCD jet background from same-sign-charge, low-MET, and/or anti-isolated lepton samplesW+jets normalization from high-mT data sample (and/or same-sign charge sample - after correction)

ATLAS-CONF-2011-132 (1.06 fb-1)

Wl

ν

ʻ


MSSM Higgs → ττ : Results

16

τlτl τlτh τhτhelectron-muon lepton-hadron

visible mass

hadron-hadron

effective mass MMC mass

consistent with predicted background yield+shape

ATLAS-CONF-2011-132 (1.06 fb-1)


MSSM Higgs → ττ : Exclusion Limits

17

cross section x BR tanβ-mA plane

ATLAS-CONF-2011-132 (1.06 fb-1)


18

Charged Higgs


Charged Higgs : Overview

19

considered channels:

for mH+ < mtop :

ATLAS-CONF-2012-011 (4.6 fb-1)

selection:1 electron or 1 muon withpT > 25 GeV / pT > 20 GeVat least 4 jets (2 of them b-tagged)with pT > 20 GeV ETmiss > 40 GeV (>20 GeV for small φl,miss) event kinematics consistent with signal topology

discriminating variables:

related to invariant mass of b jet and lepton from same top decay

lower bound on charged (W or H) boson mass from top decay


Charged Higgs : Lepton + Jets

20

ATLAS-CONF-2012-011 (4.6 fb-1)


Charged Higgs : Tau + Lepton

21

selection:1 electron or 1 muon withpT > 25 GeV / pT > 20 GeV1 hadronic tau decaywith pT > 20 GeV opposite chargeat least 2 jets (1 of them b-tagged)with pT > 20 GeVsum of primary-vertex track pT: ΣpT > 100 GeV

discriminating variable:ETmiss

ATLAS-CONF-2012-011 (4.6 fb-1)


Charged Higgs : Tau + Jets

22

selection:Tau + Etmiss trigger1 hadronic tau decaywith pT > 40 GeV ETmiss > 65 GeV

> 13

jet kinematics consistent with signal topology

discriminating variable:transverse mass mT

ATLAS-CONF-2012-011 (4.6 fb-1)


Charged Higgs : Exclusion Limits

23

lepton+jets

tau+jets combined

tau+lepton

ATLAS-CONF-2012-011 (4.6 fb-1)


Charged Higgs : Exclusion Limits

24

lepton+jets

tau+jets combined

tau+lepton

ATLAS-CONF-2012-011 (4.6 fb-1)


25

Doubly-Charged Higgs


H±±→μ±μ± : Analysis

26

relevant in Higgs Triplet, Little Higgs, and Left-Right Symmetric modelsselect pairs of 2 same-sign-charge muons withpT > 20 GeVlook for resonance in di-muon mass spectrumno significant excess over background-only prediction found

arXiv:1201.1091 (1.6 fb-1), acc. by PRD


H±±→μ±μ± : Exclusion Limits

27

arXiv:1201.1091 (1.6 fb-1), acc. by PRD


Also… [not in this talk]

28

H+ →csnMSSM a1→μμ

ATLAS-CONF-2011-094 (35 pb-1)

ATLAS-CONF-2011-020 (40 pb-1)


Summary

29

a number of BSM Higgs scenarios are being probed in parallel to the SM Higgs searchno indication for a BSM Higgs boson yetsearches continue with more data and improved methodsstill significant room for BSM Higgs discoveries for the year ahead


Backup Material


Fermiophobic Higgs

31


The Missing Mass Calculator

32

split missing Et into two vectors pmis1,2 (→ neutrinos)kinem. constraints

scan free parameters and weight with expected probability to come from τ decaytake maximum of obtained di-τ mass distribution

A.Elagin, P.Murat, A.Pranko, A.Safonov arXiv:1012.4686 ; NIM A654 (2011) 481

e.g.

http://arxiv.org/find/hep-ex/1/au:+Pranko_A/0/1/0/all/0/1

http://arxiv.org/find/hep-ex/1/au:+Pranko_A/0/1/0/all/0/1


τ Embedding (e.g. for Z → ττ Modeling)

33

select Z → μμ data eventsremove muon tracks and nearby calorimeter cellssimulate stand-alone Z → ττ decays such that simulated τ four-momenta are the same as original muons ones (after mass correction)merge into single hybrid eventre-reconstruct objects and missing Et

reliable model of Z → ττ background shape essential (for low-mass Higgs)desirable to use real data but cannot select Z → ττ signal-freeuse Z → μμ data as starting point (≈ signal-free due to small H-μ coupling)

underlying event, pileup, hadronic activity, … from data


Charged Higgs Candidate Event

34


H±±→μ±μ± : Exclusion Limits

Documents

BSM Higgs Boson Searches with ATLASmoriond.in2p3.fr/QCD/2012/SundayAfternoon/Kroseberg.pdfDecays to γγ, WW, ZZ, Zγ Here: focus on γγ (enhanced w.r.t. SM for light(!) Higgs) arXiv:1101.0593v3