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 Motivation

The possibility of Higgs decaying invisibly was first noted by Suzuki and Shrock [1]. 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. [4]), 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 [7], but it may occur in non-minimal scenarios, such as NMSSM [8,9,10] or multiple SUSY breaking sectors (goldstini) [11]. Other theoretical framework with an invisibly decaying Higgs are majorons [1,12] as well as more general pNGBs [13]; hidden sectors [14,15]; fourth-generation neutrinos [16,17]; and right-handed neutrinos [18] and their K-K excitations [7] or superpartners [19].  

2  Existing Collider Studies

Invisible 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).

tt h production generally suffer from a suppressed cross-section and a complex final state, but has been considered in [20,21]. The gg→ h + jets cross section is the largest, but suffers from a Z+j background [22], making VBF the best mode to look for invisible Higgs decays (see [23,24] for 14 TeV and [22] for 7 and 8 TeV Ref. [22] estimates that 20 fb⁻¹ at 8 TeV can allow limits to be placed for Br(h→ MET) >~0.4, while Ref. [25] estimates the sensitivity Br(h→ MET) >~0.25 with 300 fb⁻¹ at 14 TeV. Meanwhile Ref. [26] estimates sensitivity for Br(h→ MET) >~0.50 with 30 fb⁻¹ at 14 TeV. Assumptions about systematic errors are critical in obtaining these estimates. Associated Zh production with a leptonically decaying Z boson can nearly approach the reach of VBF at LHC14 for m_h=125 GeV [26], despite its much lower cross-section [27,28,29]. Including Z→ bb as well as Z→ l⁺l⁻ decays can incrementally improve the reach, at both the Tevatron [7] and the LHC [25].  

3  Existing Experimental Searches and Limits

The 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 [30] 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) [31]. CMS also has a measurement in the VBF channel, with a 95% CL upper limit [32]

with 19.6 fb⁻¹ of 8 TeV data. Much weaker limits come from reinterpretation of monojet + MET measurements [33].

References

[1]R. E. Shrock and M. Suzuki, Invisible Decays of Higgs Bosons, Phys.Lett. B110 (1982) 250.

[2]J. McDonald, Gauge singlet scalars as cold dark matter, Phys.Rev. D50 (1994) 3637-3649, [hep-ph/0702143].

[3]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].

[4]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].

[5]M. Pospelov and A. Ritz, Higgs decays to dark matter: beyond the minimal model, Phys.Rev. D84 (2011) 113001, [arXiv:1109.4872].

[6]S. Weinberg, Goldstone Bosons as Fractional Cosmic Neutrinos, Phys.Rev.Lett. 110 (2013) 241301, [arXiv:1305.1971].

[7]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].

[8]L. J. Hall, D. Pinner, and J. T. Ruderman, A Natural SUSY Higgs Near 126 GeV, JHEP 1204 (2012) 131, [arXiv:1112.2703].

[9]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].

[10]J. Kozaczuk and S. Profumo, Light NMSSM Neutralino Dark Matter in the Wake of CDMS II and a 126 GeV Higgs, [arXiv:1308.5705].

[11]D. Bertolini, K. Rehermann, and J. Thaler, Visible Supersymmetry Breaking and an Invisible Higgs, JHEP 1204 (2012) 130, [arXiv:1111.0628].

[12]A. S. Joshipura and S. D. Rindani, Majoron models and the Higgs search, Phys.Rev.Lett. 69 (1992) 3269-3273.

[13]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].

[14]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].

[15]N. Craig and K. Howe, Doubling down on naturalness with a supersymmetric twin Higgs, [ arXiv:1312.1341].

[16]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].

[17]W.-Y. Keung and P. Schwaller, Long Lived Fourth Generation and the Higgs, JHEP 1106 (2011) 054, [arXiv:1103.3765].

[18]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].

[19]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].

[20]J. Gunion, Detecting an invisibly decaying Higgs boson at a hadron supercollider, Phys.Rev.Lett. 72 (1994) 199-202, [hep-ph/9309216].

[21]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].

[22]Y. Bai, P. Draper, and J. Shelton, Measuring the Invisible Higgs Width at the 7 TeV LHC, JHEP 1207 (2012) 192, [arXiv:1112.4496].

[23]O. J. Eboli and D. Zeppenfeld, Observing an invisible Higgs boson, Phys.Lett. B495 (2000) 147-154, [hep-ph/0009158].

[24]H. Davoudiasl, T. Han, and H. E. Logan, Discovering an invisibly decaying Higgs at hadron colliders, Phys.Rev. D71 (2005) 115007, [hep-ph/0412269].

[25]D. Ghosh, R. Godbole, M. Guchait, K. Mohan, and D. Sengupta, Looking for an Invisible Higgs Signal at the LHC, [arXiv:1211.7015].

[26]Sensitivity to an Invisibly Decaying Higgs Boson, Tech. Rep. ATL-PHYS-PUB-2009-061. ATL-COM-PHYS-2009-220, CERN, Geneva, Apr, 2009.

[27]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.

[28]Higgs Working Group, D. Cavalli et. al., The Higgs working group: Summary report, [hep-ph/0203056].

[29]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].

[30]ATLAS Collaboration, Search for invisible decays of a Higgs boson produced in association with a Z boson in ATLAS, .

[31]Search for invisible higgs produced in association with a z boson, Tech. Rep. CMS-PAS-HIG-13-018, CERN, Geneva, 2013.

[32]Search for an invisible higgs boson, Tech. Rep. CMS-PAS-HIG-13-013, CERN, Geneva, 2013.

[33]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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