| [1] | Georgi H and Glashow S L 1974 Phys. Rev. Lett. 32 438 |
| Pati J C and Salam A 1974 Phys. Rev. D 10 275 |
| [2] | Schrempp B and Shrempp F 1985 Phys. Lett. B 153 101 |
| Gripaios B 2010 J. High Energy Phys. 1002 045 |
| [3] | Kaplan D B 1991 Nucl. Phys. B 365 259 |
| [4] | Aad G et al [ATLAS Collaboration] 2016 Eur. Phys. J. C 76 1 |
| Khachatryan V [CMS Collaboration] 2014 Phys. Lett. B 739 229 |
| Khachatryan V et al [CMS Collaboration] 2015 J. High Energy Phys. 1507 042 |
| [5] | Dor?ner I, Fajfer S and Greljo A 2014 J. High Energy Phys. 1410 154 |
| [6] | CMS Collaboration, Report No PAS EXO-12-041 http://cds.cern.ch/record/1742179/files/ |
| [7] | Olive K et al [Particle Data Group Collaboration] 2014 Chin. Phys. C 38 090001 |
| [8] | Miranda O G and Nunokawa H 2015 New J. Phys. 17 095002 |
| [9] | Wolfenstein L 1978 Phys. Rev. D 17 2369 |
| Grossman Y 1995 Phys. Lett. B 359 141 |
| Berezhiani Z and Rossi A 2002 Phys. Lett. B 535 207 |
| Davidson S, Pena-Garay C, Rius N and Santamaria A 2003 J. High Energy Phys. 0303 011 |
| [10] | Bolanos A, Miranda O, Palazzo A, Tortola M and Valle J 2009 Phys. Rev. D 79 113012 |
| Forero D and Guzzo M 2011 Phys. Rev. D 84 013002 |
| Agarwalla S K, Lombardi F and Takeuchi T 2012 J. High Energy Phys. 1212 079 |
| Agarwalla S K, Bagchi P, Forero D V and Tórtola M 2015 J. High Energy Phys. 1507 060 |
| [11] | Escrihuela F, Miranda O, Tórtola M and Valle J 2009 Phys. Rev. D 80 105009 |
| Biggio C, Blennow M and Fernández-Martínez 2009 J. High Energy Phys. 0903 139 |
| Biggio C, Blennow M and Fernández-Martínez E 2009 J. High Energy Phys. 0908 090 |
| Escrihuela F, Tórtola M, Valle J and Miranda O 2011 Phys. Rev. D 83 093002 |
| [12] | Agarwalla S K, Kao Y, Saha D and Takeuchi T 2015 J. High Energy Phys. 1511 035 |
| [13] | Aguilar-Arevalo A et al [PiE Nu Collaboration] 2015 Phys. Rev. Lett. 115 071801 |
| [14] | Buchmüller W, Rückl R and Wyler D 1987 Phys. Lett. B 191 442 |
| Davies A J and He G 1991 Phys. Rev. D 43 225 |
| [15] | Leurer M 1994 Phys. Rev. D 49 333 |
| Gabrielli E 2000 Phys. Rev. D 62 055009 |
| Benbrik R and Chua K 2008 Phys. Rev. D 78 075025 |
| Saha J P, Misra B and Kundu A 2010 Phys. Rev. D 81 095011 |
| Arbold J M, Fornal B and Wise M B 2013 Phys. Rev. D 88 035009 |
| [16] | Davidson S, Descotes-Genon S and Verdier P 2015 Phys. Rev. D 91 055031 |
| Bessaa A and Davidson S 2015 Eur. Phys. J. C 75 97 |
| [17] | Marciano W J and Sirlin A 1993 Phys. Rev. Lett. 71 3629 |
| Cirigliano V and Rosell I 2007 J. High Energy Phys. 0710 005 |
| Bryman D A, Marciano W, Tschirhart R and Ya-manaka T 2011 Annu. Rev. Nucl. Part. Sci. 61 331 |
| [18] | Rosner J L, Stone S and van de Water R S 2015 arXiv:1509.02220 |
| [19] | Broggio A et al 2014 J. High Energy Phys. 1411 058 |
| [20] | Chakraverty D, Choudhury D and Datta A 2001 Phys. Lett. B 506 103 |
| Cheung M 2001 Phys. Rev. D 64 033001 |
| Dor?ner I, Drobnak J, Fajfer S, Kamenik J F and Ko?nik N 2011 J. High Energy Phys. 1111 002 |
| Dor?ner I, Fajfer S, Ko?nik N and Ni?and?ic I 2013 J. High Energy Phys. 1311 084 |
| Baek S and Nishiwaki K 2016 Phys. Rev. D 93 015002 |
| [21] | Queiroz F S and Shepherd W 2014 Phys. Rev. D 89 095024 |
| Queiroz F S, Sinha K and Strumia A 2015 Phys. Rev. D 91 035006 |
2016, Vol. 33 
