Higgs Exotic Decay
Goal of the group
Group Contacts
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Meetings
Meeting |
Date |
Location |
Link to Indico |
Link to minute |
17th LHCHXS WG Workshop |
9-11 November 2020 |
Vidyo |
Indico |
|
16th LHCHXS WG Workshop |
16-18 October 2019 |
CERN |
Indico |
|
Exotic Higgs Decays Workshop |
7-8 November 2016 |
SLAC, CA, US |
Indico |
Minute |
Exotic Higgs Decays Workshop |
21-22 May 2015 |
Fermilab, Illinois, US and Vidyo |
Indico |
Minute |
Exotic Higgs Decays Kick-off Meeting |
26-27 March 2015 |
Vidyo-Only |
Indico |
Minute |
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
- Production cross-sections
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/LHCHWGExoticDecayYR4ExtraMaterials
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 → ALPs |
1708.00443 , see attached slides for exp signatures, nice benchmark for H(125)→aa (ss) → 4y/2j2y |
ALP BRs for 1 benchmark point: g(fermions)=1; g(gauge bosons)=1/(4 pi)^2, BR figure |
|
Andrea Thamm |
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) →XXYY/invis |
mixture of visible & invisible (DM) decays |
|
|
|
Parameter calculations
- Higgs rare decays to mesons + photon
- Most up-to-date calculations for decays to light mesons: 1505.03870v3
- Most up-to-date calculations for decays to heavy quarkonia (J/Psi, Upsilon) using heavy-quark effective theory: 1907.06473v2
Results
CMS Higgs Exotic Decay Results
CADI # |
Signature |
Title |
Mass range |
Luminosity and Dataset |
Trigger |
Results |
arXiv |
Journal |
PAS-HIG-19-012 |
H(125) -> Z+ρ/ϕ |
Search for decays of the H(125) into a Z boson and a ρ or ϕ meson |
H(125) |
137/ fb at 13 TeV |
Standard single-lepton: IsoMu24, Ele27WPTight (2016), IsoMu27, Ele35WPTight (2017), IsoMu24, Ele32WPTight (2018) |
Upper limits on the Higgs boson branching fractions into Zρ and Zϕ are determined to be 1.21-1.89% and 0.36-0.58%, respectively, where the ranges reflect the considered polarization scenarios; these values are 860-1350 and 860-1380 times larger than the respective standard model expectations. |
2007.05122 |
Submitted to JHEP |
PAS-HIG-19-007 |
h->XX/ZX->4l |
Search for a low-mass dilepton resonance in Higgs boson decays to four-lepton final states |
4<m(X)<60 GeV |
137/ fb at 13 TeV |
|
Upper limits are set on model-independent cross sections and Higgs boson decay BRs. Additionally, limits on dark photon and axion-like particle models are reported. |
no arXiv yet |
|
PAS-HIG-18-025 |
H->J/ψ J/ψ or H->Υ(nS) Υ(nS) |
Search for Higgs and Z boson decays to J/ψ or Υ pairs |
H(125) |
37.5/ fb at 13 TeV |
Dedicated triggers in 2017: HLT_Dimuon0_Jpsi3p5_Muon2, HLT_Trimuon5_3p5_2_Upsilon_Muon |
Upper limits on the branching fractions. In the J/ψ pair final state the limits are 1.8×10−3 for the Higgs boson, respectively, while in the combined Υ(nS) pair final states the limits are 1.4×10−3 |
1905.10408 |
PLB 797 (2019) 134811 |
HIG-18-024 |
H->aa->μμττ (boosted) |
Search for a light a1 boson boson in the boosted μμττ final state |
m(a)<2*m(b): 3.6 <m(a)< 21 GeV |
35.9/ fb at 13 TeV |
Iso(Tk)Mu24 |
Limits on BR for H→aa→μμττ, down to 1.5 (2.0) × 10−4 for mH= 125 (300) GeV. Model-dependent limits on BR(H→aa) are set within 2HDM+s models, with the most stringent results obtained for Type-III models. |
2005.08694 |
Accepted for publication in JHEP |
HIG-18-017 |
h->μτ, h->eτ |
Search for lepton flavour violating decays of a neutral heavy Higgs boson to μτ and eτ |
h mass: 200-900 GeV |
35.9/ fb at 13 TeV |
singleMu for μτ, singleEle for eτ(h), electron-muon trigger for eτ(μ) |
Upper limits on the production cross section multiplied by the branching fraction vary from 51.9 (57.4) fb to 1.6 (2.1) fb for the μτ and from 94.1 (91.6) fb to 2.3 (2.3) fb for the eτ |
1911.10267 |
JHEP 03 (2020) 103 |
HIG-18-011 |
h->a1a1->2b2mu |
Search for an exotic decay of the Higgs boson to two a1 bosons in final state with two muons and two b quarks |
20 < m(a) < 62.5 GeV |
35.9/ fb at 13 TeV |
doubleMu (17 & 8 GeV) OR Iso(Tk)Mu24 OR Iso(Tk)Mu22_eta2p1 |
The limits on the branching fraction are (1-6)×10−4. Compared with the similar analysis in Run I, the limits are improved by more than a factor of two |
1812.06359 |
Phys. Lett. B 795 (2019) 398 |
PAS-HIG-18-006 |
H→a1a1→4τ/2μ2τ |
Search for light pseudoscalar boson pairs in final states with two muons and two nearby tracks |
4 < m(a) < 15 GeV |
35.9/ fb at 13 TeV |
doubleMu (17 & 8 GeV) + same-sign + DZ |
With no evidence for a signal, the observed upper limit on the product of the inclusive signal cross section and the branching fraction, relative to the SM H production cross section, ranges from 0.022 at ma1= 9 GeV to 0.23 at ma1= 4 GeV and reaches 0.16 at ma1=15 GeV. |
1907.07235 |
Phys. Lett. B 800 (2019) 135087 |
HIG-18-003 |
h->a1a1->4mu |
Search for pair production of new light bosons decaying into muons |
light boson masses from 0.25 to 8.5 GeV |
35.9/ fb at 13 TeV |
doubleMu: HLT_TrkMu15_DoubleTrkMu5NoFiltersNoVtx |
Result interpreted in the context of the NMSSM and a dark supersymmetry model that allows for nonnegligible light boson lifetimes. |
1812.00380 |
Phys. Lett. B 796 (2019) 131 |
HIG-17-029 |
H->aa->μμττ |
Search for light pseudoscalars in the final state of two muons and two τ leptons |
m(a) between 15.0 and 62.5 GeV |
35.9/ fb at 13 TeV |
doubleMu (17 & 8 GeV) |
Upper limits are set on the branching fraction of the Higgs boson to two light pseudoscalar bosons in different types of 2HDM+s |
1805.04865 |
JHEP 11 (2018) 018 |
PAS-HIG-17-023 |
VBF h->invisible |
Search for invisible decays of the Higgs boson produced through vector boson fusion |
mH=125.09 GeV |
35.9/ fb at 13 TeV |
MET and HT triggers with 110 or 120 GeV thresholds |
Upper limit of 0.24 (0.18) is placed on the invisible branching fraction. This result is also interpreted in the context of Higgs-portal dark matter models. The combined observed (expected) upper limit is 0.19 (0.15). |
1809.05937 |
PLB 793 (2019) 520 |
HIG-17-001 |
h->μτ, h->eτ |
Search for lepton flavour violating decays of the Higgs boson to μτ and eτ |
h(125) |
35.9/ fb at 13 TeV |
single-mu, single-ele, e+mu triggers |
The observed (expected) upper limits on the lepton flavour violating BRs are BR(H→μτ)< 0.25% (0.25%) and BR(H→eτ)< 0.61% (0.37%), at 95% confidence level. |
1712.07173 |
JHEP 06 (2018) 001 |
HIG-13-010 |
h->a1a1->4mu |
Search for non-SM Higgs decaying to two a1 bosons that decay to muons |
2mμ < m(a) < 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), dilepton (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 .
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
Links
--
ReiTanaka - 2014-12-18
- ALP Brs: blue(ee,mm,tt)(dot,dash,solid)_green(ss,cc,bb)_red(yy)_orange(gg):