Higgs Exotic Decay

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Meetings

 LHCHXS WG Workshop Exotic Higgs Decays Workshop Exotic Higgs Decays Workshop Exotic Higgs Decays Kick-off Meeting Meeting Date Location Link to Indico Link to minute 16-18 October 2019 CERN Indico 7-8 November 2016 SLAC, CA, US Indico 21-22 May 2015 Fermilab, Illinois, US and Vidyo Indico 26-27 March 2015 Vidyo-Only Indico

Yellow Report 4

Here would be a summary of the Higgs Exotic Chapters of the YR4 ([link to arxiv):

Exclusive mesonic and flavour-violating Higgs boson decays

Rare exclusive decays of the SM-like Higgs boson to mesonic final states provide a unique window onto light quark Yukawa couplings. We discuss the SM predictions for the branching ratio for Higgs boson decays into a meson plus a photon and for Higgs boson decay to a meson plus a massive gauge boson . Additionally we summarize the impact of different frameworks for physics beyond the SM on these exclusive branching ratios following by a discussion about the prospects for their detection at the LHC.

Recommendations for searches for exotic Higgs boson decays

In Run 2 of the LHC, the programmatic search for exotic Higgs boson decays will increasingly become an important topic of study. To help guide this experimental program, in this section we provide a set of recommendations for searches for the production of exotic particles in the decays of the Higgs boson.

The recommendation will cover the following domains:

• A signature-based search program for exotic decays

• Presentation of results

• Production cross-sections

• Signal event generation

• Mass ranges

Partonic distributions for the prompt decay topology h → XX → 2Y 2Y ′

In this section we study the decay topology where the Higgs boson decays to two exotic particles of the same mass, each of which then undergoes a prompt two-body decay to visible SM particles Y, Y ′: h → XX → 2Y 2Y ′. This decay topology is naturally realized in many well-motivated BSM frameworks. In particular, extensions of the Higgs sector by an additional, possibly complex, singlet scalar can naturally have Higgs boson decays to (pseudo-)scalars as one of their leading signatures. These (pseudo-)scalars decay mainly to fermions, with preference for heavy flavour. Signals of this class of models, SM+S and 2HDM+S. The NMSSM is one of the best-studied examples of this type of extended Higgs sector. It has a large portion of parameter space where an approximate R-symmetry yields a SM-like Higgs boson with appreciable branching ratio into a pair of light pseudo- scalars a. Other motivations for singlet-extended Higgs sectors include models of first-order electroweak phase transitions and thermal dark matter . In composite Higgs models, a symmetry-protected light pseudo-scalar in the spectrum may be fermiophobic, with dominant decays to gluon or photon pairs, thus yielding the exotic decay modes h → aa → 4g,2γ2g,4γ. Another well-studied extension of the SM is a Higgsed dark U(1) that kinetically mixes with SM hypercharge, in which case the Higgs boson decay h → ZDZD → 2f2f′ yields final states weighted by gauge couplings, rather than Yukawa couplings, giving relatively leptophilic signatures All these exotic decays have very similar parton- level kinematics

Prospects for prompt decays with MET :h → 2γ + E/T test case

In this study, we devise a search strategy for the exotic decay of the 125 GeV Higgs boson in the $\gamma\gamma+MET$ final state. The studied final state comes in two different topologies: resonant and non-resonant. In the resonant case, the Higgs decays into two scalars, one being undetected and the other decaying resonantly into two photons. The non-resonant case, based on low scale SUSY breaking models, the Higgs decays into two neutralinos, each subsequently decaying into a photon and a gravitino. We estimate the sensitivity of these searches using a DELPHES detector simulation, and targeting $100$ fb$^{-1}$ of $\sqrt{s}=14$ TeV $pp$ data from the LHC.

Many plots for this search can be found here: https://twiki.cern.ch/twiki/bin/view/LHCPhysics/LHCHXSWGExoticDecayYR4ExtraMaterials

Longlived particles from Higgs boson decays

Long-lived particles (LLPs), specifically meta-stable particles with proper lifetimes cτ μm, arise in a large variety of BSM scenarios. Such particles, once produced at the LHC or other colliders, can decay within the detector volume with measurable displacement from the interaction point. For experimental searches, this represents both a challenge and an opportunity. On the one hand, the ATLAS and CMS detectors were not specifically optimized for displaced decays, which can make triggering and reconstruction challenging. On the other hand, events with displaced decays are spectacular and relatively background-free. This makes LLP searches enticing discovery avenues for new physics, especially in light of null results from prompt BSM searches at the LHC Run 1.

Generating MC samples for displaced objects ( Madgraph implementation )

The hXX-HF scenario can be realized by repurposing the SM + dark vector + dark Higgs MadGraph model of available at http://insti.physics.sunysb.edu/~curtin/hahm_mg.html. In this model, X is identified with the dominantly singlet scalar state hs, with mX corresponding to the model parameter MHSinput. The singlet hs decays to SM fermions via its mixing with the SM-like Higgs h, which is controlled by the model parameter kap. This MadGraph model includes the couplings between the Higgs and SM gauge bosons, including the gluons via an effective operator. X therefore inherits the same couplings, and decays like X → V*V* can also be generated.

For a given Br(h → XX), ΓX = 1/(cτX) and mX, the procedure for generating h → XX → SM events is the following:

1. Switch off dark photon effects (by setting the epsilon and mZDinput parameters to, say, 10e-09 and 1000e+00 respectively.)

2. Set the parameter MHSinput to the desired mX .

3. Event generation will depend on how LLPs are handled, specifically whether X is decayed in MadGraph or e.g. in Pythia. In the former case, one could generate the processes

p p > hs hs, hs > b b ̃

p p > hs hs, hs > ta+ ta-

p p > hs hs, hs > ta+ ta-, hs > b b ̃

separately (for the most important b ̄b and τ+τ− final states), then manually displace the decays. In the latter case, X can be left undecayed in MadGraph. The lifetime can then be written to the LHE file before running through Pythia. Another possibility is to produce events with the X decay implemented directly in Pythia. In that case the lifetime can be written to the SLHA file.

4. Each sample can then be rescaled to the desired σh ×Br(h → XX)×BR(XX → fff f ). Here σh is the inclusive Higgs boson production cross section, and BR(X → f f ) can be computed for a SM-like Higgs boson of mass mX using HDECAY 6.42. This method ensures that important NLO QCD and threshold effects are handled accurately, which is not guaranteed if using LO branching fractions generated internally by Madgraph or Pythia. Higher-order differential effects in Higgs boson production can be taken into account by reweighing events using Higgs boson pT spectra according to the recommendations of Secs. IV.6.3 and IV.6.4 of yellow report 4

Benchmark models

Signature Motivation Parameter calculations MC implementation Contact
H(125)→aa (ss) →XXYY 1312.4992 Br(a(s)→XX) for plots from the paper, outside of the quarkonia regions plotdata.zip   Stefania Gori, Yiming Zhong
H(125)→aa (ss) →XXYY 1802.02156 BR.tgz. Calculations provide Br(a->xx) values for multiple tan(beta) values and cover also the quarkonia regions. Please read the README.txt to know how to use them.   Ulrich Haisch
H(125)→hh 1601.07880, 1501.02234,slides see the quoted papers available, contact the authors Tania Robens, Tim Stefaniak
H(125)→h1h2 1908.08554, slides, slides see the quoted paper available, contact the authors Tania Robens, Tim Stefaniak, Jonas Wittbrodt
H(125)→hh EWPT: 1911.10210, 1911.10206 Br(S->ff) have been calculated using HDECAY, see the attached plot: s_Brs_1911.10210.pdf   paper authors
H(125)→2Zd→4 lep 1412.0018 Table2 of 1412.0018 hahm_mg Jessie Shelton, Stefania Gori, David Curtin, Rouven Essig
H(125)→2Hd→4Ad→8 lep Hto8lepChannel_Stolarski Table2 of 1412.0018 hahm_mg Daniel Stolarski
H(125)→aa (ss) → 4y/2j2y
H(125)→aa (ss) →XXYY/invis mixture of visible & invisible (DM) decays

Results

CMS Higgs Exotic Decay Results

 Cadi # Signature Title Mass range Luminosity and Dataset Trigger Results arXiv Journal HIG-13-010 h->a1a1->4mu Search for non-SM Higgs decaying to two a1 bosons that decay to muons 2mμ < ma < 2mτ and 85 < h<150 GeV 20.7/ fb and 8 TeV doubleMu (17 & 8 GeV) No excess is found. Results interpretation in NMSSM and in scenarios containing a hidden sector, including those predicting a nonnegligible light boson lifetime 1506.00424 Phys. Lett. B 752 (2016) 146 HIG-13-030 h->invisible Search for invisible Higgs decays in the VBF and associated Z production 115-145 up to 19.7/fb and 8 TeV MET+2 fwd-jets (VBF), dolepton (ZH) and MET+2jet (bbH) the observed (expected) upper limit on the invisible branching fraction at mH = 125 GeV is found to be 0.58 (0.44) at 95% confidence level 1404.1344 Eur. Phys. J. C 74 (2014) 2980 HIG-14-005 h->muTau and h->mue Search for lepton-flavour-violating decays of the Higgs boson 0-300 19.7/fb and 8 TeV singleMu and Mu+electron The search sensitivity is an order of magnitude better than the existing indirect limits. A slight excess of signal events with a significance of 2.4 standard deviations is observed. The best fit branching fraction is B(H to mu tau) = (0.84 +0.39 -0.37)%. B(H to mu tau) < 1.51% at 95% confidence level is set. Constrain the mu-tau Yukawa couplings to be less than 3.6E-3. 1502.07400 Phys. Lett. B 749 (2015) 337 HIG-14-003 H → (J/ψ)γ Search for a Higgs boson decaying into gamma* gamma to ll gamma with low dilepton mass in pp collisions at sqrt(s) = 8 TeV 120-150 19.7/fb and 8 TeV Gamma+Muon and double_gamma upper limit at 95% CL on the branching fraction of H to(JPsi) gamma for the 125 GeV Higgs boson is set at 1.5E-3 1507.03031 Phys. Lett. B 753 (2016) 341 HIG-14-019 h2->h1h1->4taus Search for NMSSM h2(125) to h1h1 to 4tau 4-8 GeV 19.7/fb and 8 TeV doublemu (17 and 8 GeV) no significant excess in data above standard model background expectations, an upper limit set on the signal production cross section times branching fraction as a functionofthea1(h1) boson mass.The limit ranges from 4.5 pb at ma1 (mh1)=8GeV to 10.3pb at ma1 (mh1) = 5GeV. 1510.06534 10.1007/JHEP01(2016)079 HIG-14-022 H → aa(hh)→ττ ττ Search for Higgs Decays to New Light Bosons in Boosted Tau Final States 5-15 GeV 19.7/fb and 8 TeV Single Mu No excess of events above the Standard Model backgrounds is found, and upper limits are set on the branching ratio BR(H → aa/hh)BR2(a/h → ττ) (Not available in arXiv) http://cds.cern.ch/record/2058768?ln=en HIG-14-025 h->photon+undetected Search for exotic decays of a Higgs boson into undetectable particles and photons 0-120 GeV up to 19.4 and 8 TeV Gamma+MET(for ggH) & single/double lepton (for ZH) For neutralino masses from 1 to 120 GeV an upper limit in the range of 7 to 13% is obtained 1507.00359 0.1016/j.physletb.2015.12.017 HIG-14-040 H → eτ and H → eμ Search for LFV Higgs boson decays in the e-tau and e-mu final states at 8 TeV 0-300 19.7 and 8 TeV e+mu trigger & single electron trigger set a limit on the branching ratio of B(H → eμ) < 0.036% at 95% confidence level. The limits on B(H → eτ) and B(H → eμ) are subsequently used to constrain the Yeτ and Yeμ Yukawa couplings. (Not available in arXiv) http://cds.cern.ch/record/2046190?ln=en HIG-15-011 H → aa→μμ ττ Search for the exotic decay of the Higgs boson to two light pseudoscalar bosons with two taus and two muons in the final state at 8 TeV 2-62.5 19.7 and 8 TeV double muon trigger Masses of the pseudoscalar boson between 20 and 62.5 GeV are probed, and upper limits between 4 and 15% are set on the branching fraction of the Higgs boson to two light pseudoscalar bosons, under the hypothesis that the pseudoscalar a does not decay to quarks. (Not available in arXiv) http://cds.cern.ch/record/2128149?ln=en HIG-15-011 H → aa→μμ bb; Search for exotic decays of the Higgs boson to a pair of new light bosons with two muon and two b jets in final states at 8 TeV 25-62.5 19.7 and 8 TeV double muon trigger Search for exotic decays of a Higgs boson with mh =125GeV to a pair of new light bosons, a1, where one of the light bosons decays to a pair of muons and the other one decays to a pair of b quarks is reported.A data sample corresponding to an integrated luminosity of 19.7 fb−1 recorded with the CMS detector in 2012 is exploited in μ+μ−bb final states where no statistically significant excess is observed with respect to the standard model back- grounds for different ma1 hypotheses above 25 GeV and below mh/2. (Not available in arXiv) http://cds.cern.ch/record/2135985?ln=en

ATLAS Higgs Exotic Decay Results

Most complete and up-to-date info can be found on the ATLAS public results Twiki: https://twiki.cern.ch/twiki/bin/view/AtlasPublic .

 Channel (date public) Title Data set CDS public arXiv Journal H → Za(→ jj) (Apr 2020) Search for Higgs boson decays into a Z boson and a light hadronically decaying resonance 139/fb (2015-2018) https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HDBS-2018-37/ https://arxiv.org/abs/2004.01678 H → ss → 4f (March 2020) Reinterpretation of the ATLAS Search for Displaced Hadronic Jets with the RECAST Framework 10-33/fb https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PUBNOTES/ATL-PHYS-PUB-2020-007/ H → ss → 4f (Feb 2019) Search for long-lived neutral particles in pp collisions at that decay into displaced hadronic jets 10-33/fb https://arxiv.org/abs/1902.03094 H → lepton jets Search prospects for dark-photons decaying to displaced collimated jets of muons at HL-LHC 3000 /fb https://cds.cern.ch/record/2654518/files/ATL-PHYS-PUB-2019-002.pdf H → inv, VBF Search for invisible Higgs boson decays in vector boson fusion at √s = 13 TeV with the ATLAS detector 36.1/fb (2015-2016) arXiv:1809.06682 H → φγ / ργ Search for exclusive Higgs and Z boson decays to φγ and ργ with the ATLAS detector 36.1/fb (2015-2016) arXiv:1712.02758 JHEP 07 (2018) 127 H → J/ψ γ / ψ(2S) γ / ϒ(nS) γ Searches for exclusive Higgs and Z boson decays into J/ψ γ, ψ(2S) γ, and ϒ(nS) γ at √s = 13 TeV with the ATLAS detector 36.1/fb (2015-2016) Phys. Lett. B 786 (2018) 134 H→aa→bbμμ Search for Higgs boson decays into a pair of light bosons in the bbμμ final state in pp collisions at √s = 13 TeV with the ATLAS detector 36.1/fb (2015-2016) HIGG-2016-03 arXiv:1807.00539 H → 2a → 4b Search for the Higgs boson produced in association with a vector boson and decaying into two spin-zero particles in the H → 2a → 4b channel in pp collisions at 13 TeV with the ATLAS detector 36.1/fb (2015-2016) arXiv:1606.08391 H → γγjj Search for Higgs boson decays into pairs of light (pseudo)scalar particles in the γγjj final state in pp collisions at 13 TeV with the ATLAS detector 36.1/fb (2015-2016) arXiv:1803.11145 H → Zd Zd → 4lep Search for Higgs boson decays to beyond-the-Standard-Model light bosons in four-lepton events with the ATLAS detector at √s=13 TeV 36.1/fb (2015-2016) arXiv:1802.03388 H → γ+MET Search for exotic decays of the Higgs boson to at least one photon and missing transverse momentum using 79.8 1/fb of proton-proton collisions collected at √s = 13 TeV with the ATLAS detector 79.8/fb ATLAS-CONF-2018-019 H → γγ+MET A search for new phenomena in events with missing transverse momentum and a Higgs boson decaying to two photons at √s = 13 TeV with the ATLAS detector 36.1/fb ATLAS-CONF-2017-024 H → γγ+MET A search for new phenomena in events with missing transverse momentum and a Higgs boson decaying to two photons in a 13.3 fb-1 pp collision dataset at √s = 13 TeV with the ATLAS detector 13.3/fb (2015+2016) ATLAS-CONF-2016-087 h(125) → φγ Search for Higgs and Z Boson Decays to φγ with the ATLAS Detector 3.2/fb (2015) arXiv:1607.03400 Phys. Rev. Lett. 117, 111802 (2016) h(125) → 2a → 4b Search for the Higgs boson produced in association with a W boson and decaying to four b-quarks via two spin-zero particles in pp collisions at 13 TeV with the ATLAS detector 3.2/fb (2015) arXiv:1606.08391 Eur. Phys. J. C (2016) 76:605 h(125) → γγ + MET Search for new phenomena in events with missing transverse momentum and a Higgs boson decaying to two photons in pp collisions at √s = 13 TeV with the ATLAS detecto 3.2/fb (2015) ATLAS-CONF-2016-011 h → τμ / τe / eμ Search for lepton-flavour-violating decays of the Higgs and Z bosons with the ATLAS detector Full 8 TeV arXiv:1604.07730 Submitted to EPJC VBF H→ INV Search for a high-mass Higgs boson decaying to W boson pairs in pp collisions at √s = 8 TeV with the ATLAS detector Full 8 TeV arXiv:1508.07869 JHEP01(2016)172 H→γγγγ Search for new phenomena in events with at least three photons collected in pp collisions at √s = 8 TeV with the ATLAS detector Full 8 TeV arXiv:1509.05051 Eur. Phys. J. C (2016) 76:210 LFV H→μτ Search for lepton-flavor-violating H→μτ decays of the Higgs boson with the ATLAS detector Full 8 TeV arXiv:1508.03372 JHEP11(2015)211 H→ γγ + MET Search for Dark Matter in Events with Missing Transverse Momentum and a Higgs Boson Decaying to Two Photons in pp Collisions with the ATLAS Detector at √s = 8 TeV full 8 TeV arXiv:1506.01081 Phys. Rev. Lett. 115, 131801 (2015) H→hh→4b Search for Higgs boson pair production in the b b-bar b b-bar final state from pp collisions at √s = 8 TeV with the ATLAS detector Full 8 TeV arXiv:1506.00285 Eur. Phys. J. C (2015) 75:412 H→ Z(dark)Zdark Search for new light gauge bosons in Higgs boson decays to four-lepton final states in pp collisions at √s = 8 TeV with the ATLAS detector at the LHC Full 8 TeV arXiv:1505.07645 Phys. Rev. D 92, 092001 (2015) VH→(had)INV Search for the invisible decay of the Higgs boson produced in association with a vector boson in pp collisions at √s = 8 TeV Full 8 TeV arXiv:1504.04324 Eur. Phys. J. C (2015) 75:337 H/h→aa→μμττ Search for Higgs bosons decaying to aa in the mu mu tau tau final state in pp collisions at √s = 8 TeV Full 8 TeV arXiv:1505.01609 Phys. Rev. D92 (2015) 052002 VBF H→ INV Search for an Invisibly Decaying Higgs Produced via Weak Boson Fusion Full 8 TeV Conf note ATLAS-CONF-2015-004 H->γ+MET Search for exotic Higgs-boson decays in events with at least one photon, missing transverse momentum, and two forward jets produced in s√ = 8 TeV pp collisions with the ATLAS detector Full 8 TeV Conf note ATLAS-CONF-2015-001 H→INV (monojet) Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at sqrt(s) = 8 TeV with the ATLAS detector Full 8 TeV arXiv:1502.01518 Eur. Phys. J. C (2015) 75:299 H→Jψγ Search for Higgs and Z Boson Decays to J/psi gamma and Upsilon(nS) gamma with the ATLAS Detector Full 8 TeV arXiv:1501.03276 Phys. Rev. Lett. 114 (2015) 121801 h->long lived particles Search for pair produced long-lived neutral particles decaying in the ATLAS hadronic calorimeter Full 8 TeV Conf note ATLAS-CONF-2014-041 h->hh->4b Search for resonant Higgs-pair production in the 4b final state Full 8 TeV Conf note ATLAS-CONF-2014-005 ZH→ (ll)INV Search for Invisible Decays of a Higgs Boson Produced in Association with a Z boson in ATLAS 7+8 TeV arXiv:1402.3244 HIGG-2013-03

LHCb Higgs Exotic Decay Results

 Channel Title Data set arXiv Journal h -> long lived particles Search for long-lived particles decaying to jet pairs 0.62/fb (2011) arXiv:1412.3021 Eur. Phys. J. C75 (2015) 152 h -> long lived particles Search for Higgs-like bosons decaying into long-lived exotic particles 0.62/fb (2011) arXiv:1609.03124 Eur. Phys. J. C (2016) 76: 664 h -> long lived particles Search for massive long-lived particles decaying semileptonically in the LHCb detector 1+2/fb (2011+2012) arXiv:1612.00945 Eur. Phys. J. C (2017) 77:224 h -> long lived particles Updated search for long-lived particles decaying to jet pairs 2/fb (2012) arXiv:1705.07332 New scalar mixing with SM Higgs Search for long-lived scalar particles in B+→K+χ(μ+μ−) decays 1+2/fb (2011+2012) arXiv:1612.07818 PRD 95, 071101 (R) 2017

References

-- ReiTanaka - 2014-12-18

Topic attachments
I Attachment History Action Size Date Who Comment
tgz BR.tgz r1 manage 6505.5 K 2018-09-12 - 18:52 LjiljanaMorvaj Br(a->xx) in various 2HDM including the quarkonia regions
jpg HiggsExoChart.jpg r1 manage 180.9 K 2017-01-16 - 04:23 AbdollahMohammadi
pdf HiggsExoChart.pdf r1 manage 194.5 K 2017-01-16 - 04:16 AbdollahMohammadi Higgs Exo Chart
pdf Hto8lepChannel_Stolarski.pdf r1 manage 187.0 K 2018-11-02 - 17:35 LjiljanaMorvaj
txt MinueExoticHiggsDecayKickOffMeeting.txt r1 manage 2.1 K 2015-06-10 - 22:37 AbdollahMohammadi Minute of exotic Higgs decays kick-off meeting
txt MinueExoticHiggsDecayMeetingFermilab.txt r1 manage 3.0 K 2015-06-10 - 22:09 AbdollahMohammadi Minute of the Exotic Higgs Decays workshop at Fermilab 21-22 May 2015
txt README.txt r1 manage 1.6 K 2018-09-12 - 18:52 LjiljanaMorvaj Readme for the usage of Br(a->xx) values in various 2HDM including the quarkonia regions
zip plotdata.zip r1 manage 1606.2 K 2017-10-13 - 22:04 StefaniaGori
pdf s_Brs_1911.10210.pdf r1 manage 27.7 K 2020-01-08 - 15:18 LjiljanaMorvaj Singlet Brs to SM from HDECAY, used in 1911.10210
Topic revision: r37 - 2020-04-17 - LjiljanaMorvaj

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