Contact Person(s)Jessie Shelton, Stefania Gori More details on this mode may be found in Section 5 of Survey of Exotic Higgs Decays (arXiv:1312.4992).
1 Theoretical MotivationThe possibility of Higgs decaying invisibly was first noted by Suzuki and Shrock . A well motivated scenario for such a decay mode is Higgs decaying to dark matter [2,3]. The more minimal models of thermal dark matter annihilating via the Higgs boson are excluded by direct detection (see e.g. ), but more involved models do allow for such coupling [5,6]. In SUSY, the Higgs may decay to neutralinos in principle. This is typically not the case in the CMSSM , but it may occur in non-minimal scenarios, such as NMSSM [8,9,10] or multiple SUSY breaking sectors (goldstini) . Other theoretical framework with an invisibly decaying Higgs are majorons [1,12] as well as more general pNGBs ; hidden sectors [14,15]; fourth-generation neutrinos [16,17]; and right-handed neutrinos  and their K-K excitations  or superpartners .
2 Existing Collider StudiesInvisible decays are difficult experimentally and have an irreducible background from Z→νν production. A Higgs decaying invisibly must be produced in association with another object in order to be observed. In order of production cross-section, the reasonable candidates are then:
- gg→ h + jets
- VBF production of h+2j
- Wh, W→ lν
- Zh, Z→ l+l−, (bb).
3 Existing Experimental Searches and LimitsThe best existing constraints come from ATLAS measurements targeting Zh associated production with Z→ll, which limit the invisible branching fraction to be
at 95% CL  with 4.7 fb −1 at 7 TeV and 13.0 fb−1 at 8 TeV. The measurement by CMS in the same channel with the full 7 and 8 TeV data sets places a 95% CL upper bound on the invisible branching fraction of Br(h→ invisible) < 0.75(0.91) . CMS also has a measurement in the VBF channel, with a 95% CL upper limit 
with 19.6 fb−1 of 8 TeV data. Much weaker limits come from reinterpretation of monojet + MET measurements .
Here we list new experimental results pertinent to this exotic higgs decay channel.
- CMS Collaboration, Search for invisible decays of Higgs bosons in the vector boson fusion and associated ZH production modes, CMS-HIG-13-030, CERN-PH-EP-2014-051 (arXiv:1404.1344).
- Ning Zhou, Zepyoor Khechadoorian, Daniel Whiteson, Tim Tait, Bounds on Invisible Higgs boson Decays from tt¯H Production, arxiv:1408.0011.
- R. E. Shrock and M. Suzuki, Invisible Decays of Higgs Bosons, Phys.Lett. B110 (1982) 250.
- J. McDonald, Gauge singlet scalars as cold dark matter, Phys.Rev. D50 (1994) 3637-3649, [hep-ph/0702143].
- C. Burgess, M. Pospelov, and T. ter Veldhuis, The Minimal model of nonbaryonic dark matter: A Singlet scalar, Nucl.Phys. B619 (2001) 709-728, [hep-ph/0011335].
- Y. Mambrini, Higgs searches and singlet scalar dark matter: Combined constraints from XENON 100 and the LHC, Phys.Rev. D84 (2011) 115017, [arXiv:1108.0671].
- M. Pospelov and A. Ritz, Higgs decays to dark matter: beyond the minimal model, Phys.Rev. D84 (2011) 113001, [arXiv:1109.4872].
- S. Weinberg, Goldstone Bosons as Fractional Cosmic Neutrinos, Phys.Rev.Lett. 110 (2013) 241301, [arXiv:1305.1971].
- S. P. Martin and J. D. Wells, Motivation and detectability of an invisibly decaying Higgs boson at the Fermilab Tevatron, Phys.Rev. D60 (1999) 035006, [hep-ph/9903259].
- L. J. Hall, D. Pinner, and J. T. Ruderman, A Natural SUSY Higgs Near 126 GeV, JHEP 1204 (2012) 131, [arXiv:1112.2703].
- B. Ananthanarayan, J. Lahiri, P. Pandita, and M. Patra, Invisible decays of the lightest Higgs boson in supersymmetric models, Physical Review D 87, 115021 (2013) [ arXiv:1306.1291].
- J. Kozaczuk and S. Profumo, Light NMSSM Neutralino Dark Matter in the Wake of CDMS II and a 126 GeV Higgs, [arXiv:1308.5705].
- D. Bertolini, K. Rehermann, and J. Thaler, Visible Supersymmetry Breaking and an Invisible Higgs, JHEP 1204 (2012) 130, [arXiv:1111.0628].
- A. S. Joshipura and S. D. Rindani, Majoron models and the Higgs search, Phys.Rev.Lett. 69 (1992) 3269-3273.
- A. Dedes, T. Figy, S. Hoche, F. Krauss, and T. E. Underwood, Searching for Nambu-Goldstone Bosons at the LHC, JHEP 0811 (2008) 036, [arXiv:0807.4666].
- R. Schabinger and J. D. Wells, A Minimal spontaneously broken hidden sector and its impact on Higgs boson physics at the large hadron collider, Phys.Rev. D72 (2005) 093007, [hep-ph/0509209].
- N. Craig and K. Howe, Doubling down on naturalness with a supersymmetric twin Higgs, [ arXiv:1312.1341].
- A. Rozanov and M. Vysotsky, Tevatron constraints on the Higgs boson mass in the fourth-generation fermion models revisited, Phys.Lett. B700 (2011) 313-315, [ arXiv:1012.1483].
- W.-Y. Keung and P. Schwaller, Long Lived Fourth Generation and the Higgs, JHEP 1106 (2011) 054, [arXiv:1103.3765].
- M. L. Graesser, Broadening the Higgs boson with right-handed neutrinos and a higher dimension operator at the electroweak scale, Phys.Rev. D76 (2007) 075006, [ arXiv:0704.0438].
- S. Banerjee, P. S. B. Dev, S. Mondal, B. Mukhopadhyaya, and S. Roy, Invisible Higgs Decay in a Supersymmetric Inverse Seesaw Model with Light Sneutrino Dark Matter, [ arXiv:1306.2143].
- J. Gunion, Detecting an invisibly decaying Higgs boson at a hadron supercollider, Phys.Rev.Lett. 72 (1994) 199-202, [hep-ph/9309216].
- B. P. Kersevan, M. Malawski, and E. Richter-Was, Prospects for observing an invisibly decaying Higgs boson in the t anti-t H production at the LHC, Eur.Phys.J. C29 (2003) 541-548, [hep-ph/0207014].
- Y. Bai, P. Draper, and J. Shelton, Measuring the Invisible Higgs Width at the 7 TeV LHC, JHEP 1207 (2012) 192, [arXiv:1112.4496].
- O. J. Eboli and D. Zeppenfeld, Observing an invisible Higgs boson, Phys.Lett. B495 (2000) 147-154, [hep-ph/0009158].
- H. Davoudiasl, T. Han, and H. E. Logan, Discovering an invisibly decaying Higgs at hadron colliders, Phys.Rev. D71 (2005) 115007, [hep-ph/0412269].
- D. Ghosh, R. Godbole, M. Guchait, K. Mohan, and D. Sengupta, Looking for an Invisible Higgs Signal at the LHC, [arXiv:1211.7015].
- Sensitivity to an Invisibly Decaying Higgs Boson, Tech. Rep. ATL-PHYS-PUB-2009-061. ATL-COM-PHYS-2009-220, CERN, Geneva, Apr, 2009.
- S. Frederiksen, N. Johnson, G. L. Kane, and J. Reid, Detecting invisible Higgs bosons at the CERN Large Hadron Collider, Phys.Rev. D50 (1994) 4244-4246.
- Higgs Working Group, D. Cavalli et. al., The Higgs working group: Summary report, [hep-ph/0203056].
- R. Godbole, M. Guchait, K. Mazumdar, S. Moretti, and D. Roy, Search for `invisible' Higgs signals at LHC via associated production with gauge bosons, Phys.Lett. B571 (2003) 184-192, [hep-ph/0304137].
- ATLAS Collaboration, Search for invisible decays of a Higgs boson produced in association with a Z boson in ATLAS, .
- Search for invisible higgs produced in association with a z boson, Tech. Rep. CMS-PAS-HIG-13-018, CERN, Geneva, 2013.
- Search for an invisible higgs boson, Tech. Rep. CMS-PAS-HIG-13-013, CERN, Geneva, 2013.
- A. Djouadi, A. Falkowski, Y. Mambrini, and J. Quevillon, Direct detection of Higgs-portal dark matter at the LHC, [arXiv:1205.3169].
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