Search for BSM Higgs bosons in fermion decay modes with ATLAS

Transcription

1 Search for BSM Higgs bosons in fermion decay modes with ATLAS A. Straessner on behalf the ATLAS Collaboration FSP 103 ATLAS CC BY-SA 3.0 LHCP 2017 Shanghai May 15-20, 2017

2 LHCHXSWG arxiv: arxiv: Beyond Standard Model Higgs Bosons MSSM predicts 5 physical Higgs states: h H A H ± 2 parameters define Higgs boson masses and couplings at tree level: mixing angle α and ratio of vacuum expectation values tanβ = v 2 /v 1 Yukawa couplings y d /y u ~ tanβ Some MSSM benchmark scenarios identify the lightest CP-even state h with the observed 125 GeV Higgs boson, e.g. m h mod±, hmssm H τ + τ H t t m h modtanβ=30 A τ + τ A t t m h modtanβ=30 H ± tb H ± τv m h modtanβ=10 2 Higgs Doublet Models (2HDM): again 5 Higgs bosons h, H, A, H ± with further variations of Higgs coupling structure to fermions and vector bosons H ±± bosons appear e.g. in left-right symmetric or Higgs triplet models Most search results presented here are based on 13 TeV ATLAS data using L=13 fb -1 Search for BSM Higgs bosons with ATLAS 2

3 Heavy H/A are produced in gg fusion and association with b-quark jets b-tag and b-veto categories Search for H/A τ + τ - Tau decays to e/µ+2v or hadrons + v final states: τ lep τ had and τ had τ had with opposite charge dedicated E T miss (+p T,µ ) > 150 GeV category in τ lep τ had QCD jets misidentified as τ had or e/µ estimated from data using fake factors Final variable: ATLAS-CONF Search for BSM Higgs bosons with ATLAS 3

4 Upper limits on σ x BR for gg fusion and b-associated production up to m A = 1.2 TeV Observed tanβ upper limits between 9 and 95% CL for m A = TeV Search Results H/A τ + τ - hmssm interpretation shows high model sensitivity for m A 2 m top Strong Coulomb correction when tops in gg-fusion loop are "slow" e.g. Z.Phys. C64 (1994) 401 ATLAS-CONF LHCHXSWG arxiv: arxiv: Search for BSM Higgs bosons with ATLAS 4

5 Search for H/A t t Positive and negative interference of pp H/A t t with SM t t production Treatment of signal (S) and interference (I) contribution is implemented by event-by-event matrix element reweighting Run-I data 8 TeV Selection: 1 lepton e/µ with p T > 25 GeV 4 jets of p T > 25 GeV, 1 or 2 b-tags E T miss + m TW > 60 GeV ATLAS-CONF Search for BSM Higgs bosons with ATLAS 5

6 Search for H/A t t 2HDM Type II interpretion separately for A and H ATLAS-CONF Decoupling limit sin(β-α) = 1: h is SM-like H VV (A VV since A is CP odd) Yukawa couplings g H/A t t ~ 1/tanβ gg A t t gg H t t tanβ<0.85 CL for m A =500 GeV and tanβ<0.45 for m H =500 GeV Search for BSM Higgs bosons with ATLAS 6

7 ATLAS-CONF For m H± > m top top-associated production dominates H ± τv subdominant at high mass for certain models and tanβ values, but cleaner final state than H ± tb Top-associated H ± τv Only hadronic decays of tau and W are considered here Main backgrounds in high mass region: events with QCD jets misidentified as τ fake factors derived from data t t background control region with 2 b-tag jets Transverse mass as final variable e/µ veto 1 b-tag jet N jet 3 p T > 25 GeV E T miss > 150 GeV 1 hadronic tau p T > 40 GeV Search for BSM Higgs bosons with ATLAS 7

8 Top-associated H ± τv ATLAS-CONF tanβ exclusion above for m H± mass range GeV in hmssm entire parameter space of m h max and m h mod± scenarios excluded for tanβ>1 and 90 GeV < m H± <140 GeV by searches at 8 TeV; 13 TeV low-mass analysis is ongoing arxiv: Search for BSM Higgs bosons with ATLAS 8

9 ATLAS-CONF Search for H ± tb High-mass H ± production mechanism with associated top: tb+t(b) final state Pre-selection: exactly 1 lepton (e/µ) p T > 25 GeV τ lepton veto N jet 4 with p T > 25 GeV 2 b-tag jets 4 signal regions: 5 jet 3 b, 5 jet 4 b, 6 jet 3 b, 6 jet 4 b 4 t t control regions with different flavor content: 4 jet 2 b, 4 jet 3 b, 5 jet 2 b, 6 jet 2 b Maximum-likelihood fit to BDT output in signal regions and H had T = p jet T distribution in control regions determine t t + 1b/1c background scale during combined fit Search for BSM Higgs bosons with ATLAS 9

10 H ± tb Search Results Good agreement of data with background-only hypothesis in all search categories ATLAS-CONF Observed σ x BR limit in pb range MSSM interpretation: mainly sensitive in low tanβ range with typical minimum at tanβ 6: analysis just starts to exclude high tanβ region in m h mod scenario Search for BSM Higgs bosons with ATLAS 10

11 H/A t t and H ± tb plus heavy flavour Search for vector-like quarks pp T T + X is interpreted as search for 2HDM Higgs production because of similar final state b, b, Main signal categories: 1 e/µ, 6 jets, 3 b-tags, E T miss + m TW > 60 GeV (0-lepton category not used for 2HDM interpretation) R=1 anti-k T jets used to include boosted decay topologies ATLAS-CONF t t + 1b background is determined in simultaneous fit to signal and control regions final variable: m eff = p T l + p T jet + E T miss Search for BSM Higgs bosons with ATLAS 11

12 H/A t t and H ± tb plus heavy flavour cos(β-α) = 0: decoupling limit pp bbh H t t pp bbh H t t Type I couplings: g H/A b b ~ 1 / tanβ g H/A t t ~ 1 / tanβ Type I tanβ=0.1 Type II tanβ=0.1 Type II couplings: g H/A b b ~ tanβ g H/A t t ~ 1 / tanβ ATLAS-CONF tth production constrained more strongly than bbh pp tth H t t tanβ=0.1 pp tbh ± H ± tb tanβ=0.1 Type I or II Type II Search for BSM Higgs bosons with ATLAS 12

13 ATLAS-CONF Search for H ±± e ± e ± Drell-Yan pair production usually dominates H ±± L and H ±± R couple to either left-handed or right-handed leptons and have different couplings to Z bosons Signal: at least 1 same-sign (SS) e ± e ± pair with m ee >300 GeV Control samples: 1 e + e SS, high and low m ee mass range Charge misidentification is measured in Z e + e - events as function of p T and η m H±±,R > 420 GeV and m H±±,L > 570 CL for BR(H ±± e ± e ± )=100% H ±± µ ± µ ± channel at 13 TeV is being studied Search for BSM Higgs bosons with ATLAS 13

14 Summary and Outlook Unfortunately, no signs of additional heavy Higgs bosons neither at 8 TeV nor in first 13 fb -1 of 13 TeV ATLAS data MSSM upper and lower limits on tanβ improved in high m A and m H± mass ranges Analyses with 35 fb -1 of 2016 data are still being worked on towards publications be patient good things take time Search for BSM Higgs bosons with ATLAS 14