LHCでのBSMヒッグス物理佐藤構二
宇宙史研究センター構成員会議
2024年7月2日

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BSM Higgs Search Motivation• Many BSM theories predict additional Higgs Bosons.
• BSM can enhance rare decay modes of 𝐻(125) boson.
• Two Higgs Doublet Model (2HDM, e.g. MSSM)– 5 Higgs Bosonsℎ, 𝐻, 𝐴, 𝐻 + , 𝐻 −– Widely used as a benchmark for BSM Higgs searches.
• 2HDM+Singlet (e.g. NMSSM)– 7 Higgs Bosons– 5 of 2HDM, with 2 additional neutral bosons (1 CP-evenand 1 CP-odd)ℎ1 , ℎ2 , ℎ3 , 𝐻+ , 𝐻 − , 𝑎1 , 𝑎2
• Many other models are searched for at LHC.

• I will present a small subset of newest and moderately new
results among many BSM Higgs results from ATLAS andCMS.
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Large Hadron Collider (LHC)ATLAS

Particle physics experiment at the highest energy𝒑 − 𝒑 collisions at 𝑬𝑪𝑴 ≤14 TeV
Broad physics program at ATLAS and CMS, including BSM
Higgs Searches.

CMS

LHC Circumferrence 27km

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Higgs Boson
Discovery

LHC Long Term Schedule• Each Exp. Collected~100 fb−1 in Run 3.
• Many analyses stillworking on Run 2 dataset.
• Analysis groups starting towork on Run 3 data.

Nowyear

𝑬𝑪𝑴 (𝐓𝐞𝐕)

integ lumi
[fb-1]

2011

752012821

Run 2

2015-2018

13139

Run 3

2022-2025

13.6

250

HL-LHC2029-2038

1430004

Run 1

Searches in 2HDM/MSSM Regime– 2HDM and MSSM are widely used as a theoreticalbenchmark for BSM Higgs searches.
– 5 Higgs bosonsℎ, 𝐻, 𝐴, 𝐻 + , 𝐻 −5

Higgs Discovery in 2012

• ATLAS and CMS reported discoveryof Higgs boson on July 4, 2012.
• Englert and Higgs won the Nobel
prize in 2013.
6𝐻(125) Measurements• Both collaborations have measured H(125) properties.
• Results are consistent with SM.

Nature 607, 52–59 (2022)

These results can be used toconstrain BSM Higgs scenarios.

Nature 607, 60–68 (2022)

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Interpretation of 𝐻(125) Measurements• Production and decay rates of 𝐻 125 are interpreted in
2HDM and MSSM scenarios.
arXiv:2402.05742

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MSSM Higgs Status• Current status of hMSSM.
• Some more full Run2 results to be released.

https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PUBNOTES/ATL-PHYS-PUB-2024-008/

https://twiki.cern.ch/twiki/bin/view/CMSPublic/SummaryResultsH
IG#NEW_Summary_of_MSSM_Higgs_Boson

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Low mass 𝐻 → 𝛾𝛾
• Many theories can give rise to additional low mass Higgs bosons.
• CMS observes an excess around 95.4 GeV with local (global)
significance of 2.9𝜎 1.3𝜎 .
ATLAS-CONF-2023-035• ATLAS local significance of 1.7𝜎 at 95.4 GeV.

arXiv:2405.18149

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BSM 𝐻/𝐴 → 𝑡𝑡ҧ

arXiv:2404.18986• Promising search for heavy 𝐻/𝐴 in 2HDM (e.g. MSSM)
at low tan 𝛽.
• Consider the intereference with SM 𝑡𝑡ҧ background.

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BSM 𝐻/𝐴 → 𝑡𝑡ҧ (cont'd)arXiv:2404.18986• Analyzed 1 and 2 lepton final states.
• Data were consistent with SM background.
• Most significant deviation was at 800 GeV with a local
significance of 2.3 𝜎.

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𝐴 → 𝑍𝐻 → ℓℓ𝑡𝑡ҧ
• Region with 400 GeV < 𝑚𝐻 ≪ 𝑚𝐴 is unexplored.
• This region is favored by some electroweak
baryogenesis scenarios.
• Analyze events with ℓ+ ℓ− + nj(1, ≥ 2𝑏)• Elliptical bins (Δ𝑚,𝑝𝑧 ) define final discriminant• No significant deviation from SM background.
Expected (∆m,𝒑𝒛 ) distribution for signal
for 𝒎𝑨 = 𝟏𝟎𝟎𝟎 𝐆𝐞𝐕, 𝒎𝑯 = 𝟔𝟎𝟎 𝐆𝐞𝐕

CMS-PAS-B2G-23-006

Involves two BSM
Higgs bosons

Data distribution for signal hypothesis
of 𝒎𝑨 = 𝟏𝟎𝟎𝟎 𝐆𝐞𝐕, 𝒎𝑯 = 𝟖𝟓𝟎 𝐆𝐞𝐕

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𝐴 → 𝑍𝐻 → ℓℓ𝑡𝑡ҧ (cont'd)

CMS-PAS-B2G-23-006

Exclusion limits for Type II 2HDM are set at low tan 𝛽values.

ATLAS has a comparable results for 𝐴 → 𝑍𝐻 → ℓℓ𝑡𝑡,ҧ 𝜈𝜈𝑡𝑡ҧ JHEP 02 (2024) 197

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𝐻 → ℎ125 ℎ125 → 𝑏𝑏𝜏𝜏

JHEP 07 (2023) 040• 𝜏ℎ𝑎𝑑 𝜏ℎ𝑎𝑑 (single and double 𝜏ℎ𝑎𝑑−𝑣𝑖𝑠 triggers), 𝜏𝑙𝑒𝑝 𝜏ℎ𝑎𝑑 (single lepton andlepton+𝜏ℎ𝑎𝑑−𝑣𝑖𝑠 triggers). Require two 𝑏-jets.
• PNN trained with inputs including 𝑚ℎℎ , 𝑚𝜏𝜏 , 𝑚𝑏𝑏

Largest deviation at 1 TeV with local (global) significance of 3.1𝜎 (2.0𝜎).

15Phys. Rev. Lett. 132 (2024) 231801

𝐻 → ℎ125 ℎ125
https://twiki.cern.ch/twiki/bin/view/CMSP
ublic/SummaryResultsHIG

Largest 1.1 TeV, with a local(global) significanceof 3.3σ (2.1σ).

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𝑋 → 𝐻𝐻/𝐻𝑌 → 𝑏𝑏𝛾𝛾

JHEP 05 (2024) 316• MSSM motivated search.
• 𝑋: heavy spin-0 particle.
– Spin-2 was also searched for.

• 𝑌: spin-0 particle. Can be another 𝐻(125).
• BDT was trained to divide signal regions.

Involves two BSM Higgs bosons.
Interpretation with NMSSM.

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Searches in 2HDM+Singlet/NMSSM– 7 Higgs Bosonsℎ1 , ℎ2 , ℎ3 , 𝐻 + , 𝐻 − , 𝑎1 , 𝑎2

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𝑉𝐻, 𝐻 → 𝑎𝑎 → 𝑏𝑏ത 𝑏𝑏ത
••••arXiv:2403.10341

𝑎 → 𝑏𝑏ത is usually the dominant decay mode above 𝑏𝑏ത threshold.
𝑍 → ℓℓ and 𝑊 → ℓ𝜈 channels.
3 or 4 b-tagged jets.
BDT discriminants trained for 𝑍𝐻 and 𝑊𝐻 channels for signal
separation.

𝑾𝑯 → 𝒆𝝂 + 𝟒𝒃 chan.

𝒁𝑯 → 𝝁𝝂 + 𝟒𝒃 chan.

19𝐻 → 𝑎𝑎 Search Summary Plots
https://twiki.cern.ch/twiki/bin/view/CMSPublic/Summary2HDMSRun2
ATL-PHYS-PUB-2021-008

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𝐻 → 𝑍𝑎, 𝑎 → 𝛾𝛾

Phys. Lett. B 848 (2024) 138536• 𝐻 → 𝑍𝑎 decay is unexplored.
• 𝐻 → 𝑍𝑎 decay is also motivated by axion models.
• Analysis split into resolved and merged categories
based on angular separation of 𝛾’s.
• Main backgrounds from 𝑍 + 𝑗𝑒𝑡𝑠 (𝜋 0 decays) and 𝑍 + 𝛾.
– Composition is 25:75 in merged, 90:10 in resolved.
MergedResolved

CMS has a comparable results in this search: Phys. Lett. B 852 (2024) 138582.
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Summary• LHC is under Run3 operation in 2022-2025.
– ATLAS/CMS recorded ~100 fb−1 of 13.6 TeV 𝑝 − 𝑝collision data in Run 3.
– Plan to have 250 fb−1 at end of 2025.
– Collaborations ramping up Run 3 analyses.
• Full Run 2 data (~140 fb−1 at 13 TeV) analysis are going on.
– Some more full Run2 results to be released for 2HDM,MSSM scenarios.
– Complicated signatures and heavier masses aresearched for.
– Advanced theoretical scenarios are explored.
• Run 3 dataset will enable searches and measurements athigher precision.
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Backup23

ATLAS and CMS at LHC• Multi-purpose detectors observing 𝑝 − 𝑝 collisions atWorld Highest Energy of 𝑠 ≤ 14 TeV– Standard Model phenomena: Higgs bosons, topquarks, Electroweak, 𝐵 Physics, …
– Searches for BSM physics: BSM Higgs,Supersymmetry, …

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Luminosity Delivered in Run 325

Searches for rare 𝐻(125) decays

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Rare Decays 𝐻(125) → 𝛾 + 𝑀𝑒𝑠𝑜𝑛Search Motivation• SM predicts very small branching fractions.
• 𝐻 → 𝛾(𝑞 𝑞)ത occur through direct Yukawa coupling andthrough 𝐻 → 𝛾𝛾 ∗ → 𝛾(𝑞 𝑞ത ).
– Yukawa coupling to 1st and 2nd generation is unknown.
• BSM processes can enhance the branching fractions.
• Processes like 𝐻 → 𝐾 ∗ 𝛾 can be sensitive to flavor
violating Yukawa couplings.

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Phys. Lett. B 847 (2023) 138292

Rare Decays 𝐻(125) → 𝛾𝜔/𝛾𝐾∗• Trigger on 𝛾 + tracks. Utilize modified version of 𝜏 trigger for 𝛾𝐾 ∗ .
• Meson reconstructions:– 𝜔 → 𝜋 + 𝜋 − 𝜋 0 : 279 < 𝑚 𝜋 + 𝜋 − 𝜋 0 < 648 MeV. 𝜋 0 reconstructedas Calorimeter cluster.
– 𝐾 ∗ → 𝐾 + 𝜋 − : 790 < 𝑚 𝜋 + 𝜋 − 𝜋 0 < 990 MeV.
•Observed Upper Limit
𝐵𝑟(𝐻 → 𝜔𝛾)

5.5 × 10−4𝐵𝑟(𝐻 → 𝐾 ∗ 𝛾)

2.2 × 10−428

Rare Decays 𝐻(125) → 𝛾𝜌, 𝛾𝜙, 𝛾𝐾• Mesons are reconstructed as atrack pair.
𝝆 → 𝝅+ 𝝅−∗0

CMS-PAS-HIG-23-005

𝝓 → 𝑲+ 𝑲−

𝑲∗𝟎 → 𝑲± 𝝅∓

Obtained most stringent 95% CL experimental
upper limits to date:
Br 𝐻 → 𝛾𝜌0 ≤ 3.74 × 10−4
Br 𝐻 → 𝛾𝜙 ≤ 2.97 × 10−4
Br 𝐻 → 𝐾 ∗0 𝜙 ≤ 1.71 × 10−4𝒎𝝆𝜸 (𝐆𝐞𝐕)

𝒎𝝓𝜸 (𝐆𝐞𝐕)

𝒎𝑲∗𝟎 𝜸 (𝐆𝐞𝐕)29

Rare Decays 𝐻(125) → 𝛾 + 𝑀𝑒𝑠𝑜𝑛
ATL-PHYS-PUB-2023-00430

𝐻(125) → 𝑖𝑛𝑣𝑖𝑠𝑖𝑏𝑙𝑒• Massive DM can couple to Higgs boson.
• Some theories predict that 𝐻 can act as a portal between
DM and SM sector.
• Both ATLAS and CMS searched for invisible Higgs
decays in different production modes.

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𝐻(125) → 𝑖𝑛𝑣𝑖𝑠𝑖𝑏𝑙𝑒
Phys. Lett. B 842 (2023) 137963

Eur. Phys. J. C 83 (2023) 933

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DM plots
arXiv:2107.01252 [hep-ph]Phys. Lett. B 842 (2023) 137963

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𝐻 → ℎ125 ℎ125
• Analyses in ATLAS combination Phys. Rev. Lett. 132(2024) 231801– 𝑏𝑏𝛾𝛾 resolved only Phys. Rev. D 106 (2022) 052001– 𝑏𝑏𝜏𝜏 resolved only JHEP 07 (2023) 040– 𝑏𝑏𝑏𝑏 Phys. Rev. D 105 (2022) 092002

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𝑋 → 𝑌𝐻• Atlas– 𝑋 → 𝑆𝐻 → 𝑏𝑏𝛾𝛾 2404.12915– 𝑋 → 𝑆𝐻 → 𝑙𝑒𝑝𝑡𝑜𝑛𝑠 + 𝛾𝛾 2405.20926• CMS– 𝑋 → 𝑌𝐻 → 𝑏𝑏𝑏𝑏 Phys. Lett. B 842 (2023) 137392– 𝑋 → 𝑌𝐻 → 𝑏𝑏𝜏𝜏 JHEP 11 (2021) 057– 𝑋 → 𝑌𝐻 → 𝑏𝑏𝛾𝛾 JHEP 05 (2024) 316

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ATLAS 2HDM+S Searches••••••

Full Run2 2HDM+S results from ATLAS:
𝐻 → 𝑎𝑎 → 4𝛾 2312.03306
𝐻 → 𝑎𝑎 → 𝑏𝑏𝜇𝜇 Phys. Rev. D 105 (2022) 012006
ҧ 𝑎 → 𝜇𝜇 Phys. Rev. D 108 (2023) 092007
𝑡𝑡𝑎,
𝐻 → 𝑍𝑎, 𝑎 → 𝛾𝛾 Phys. Lett. B 848 (2024) 138536
𝐻 → 𝑍𝑎, 𝑎 → ℎ𝑎𝑑𝑟𝑜𝑛𝑠 Phys. Rev. Lett. 125 (2020) 221802

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