• Northwestern Mini-Workshop on Z's: Northwestern University, Illinois (Nov. 16, 2004)
• Dark Forces Workshop: SLAC, California (Sep. 24-26, 2009)
• Searching for a New Gauge Boson at JLab (Boson 2010): JLab, Virginia (Sep. 20-21, 2010)
• Dark Forces at Accelerator Workshop (DARK 2012): INFN at Rome, Italy (Oct. 16-19, 2012)

• Landau-Yang theorem: Z' (massive vector boson) cannot decay into 2 photons (massless vector boson)
• The moment of a 2-photon system [L.D. Landau (1948)]
• Selection Rules for the Dematerialization of a Particle Into Two Photons [C.N. Yang (1950)]
• Z' -> ZZ decay is possible.
• Landau-Yang Theorem and Decays of a Z' Boson into Two Z Bosons [W.Y. Keung, I. Low, J. Shu (2008)]
• U(1)_Y & U(1)' kinetic mixing: If new particles are gauged by a U(1)', their electromagnetic charges may be shifted by a calculable amount.
• Two U(1)'s and Epsilon Charge Shifts [B. Holdom (1986)]

---

---

Heavy Z'  (mZ' ~ EW/TeV scale)

Implications of Z' [General]

• General
  • Implications of a Heavy Z' Gauge Boson (Feb. 2004), (Nov. 2004) [P. Langacker]
  • From Zero to Z (talk) [P. Langacker (2004)]
  • Alternative Supersymmetric Spectra [L. Everett, P. Langacker, M. Plumacher, J. Wang (2000)]
  • Z' Phenomenology and the LHC (TASI lecture) [T.G. Rizzo (2006)]

Direct Implications of Z'

• ICHEP 2012 ATLAS Exotic Searches Summary

• ICHEP 2012 CMS Exotic Searches Summary

• The most recent CDF Z' mass bounds from Z' -> mu mu channel

• Various analysis techniques for direct Z' resonance search
• Combined limit on spin-1 particles from the electron and muon channel. (Search for New Particles Decaying to High Mass [CDF collaboration (2004)])

Excluded regions from the current 95% C.L. limit from dilepton search in the cd-cu plane [M. Carena (2004)]


• Searches for New Physics at the Tevatron (slides) [D. Stuart (2004)]
• Searches for New Physics in High Mass Dimuon Channel in CDF Run II Data (plots) [M.K. Unel, M. Schmitt, K. Maeshima, K. Ikado, T. Nelson (2004)]
• Discovery and Measurement of Sleptons, Binos, and Winos with a Z' [M. Baumgart, T. Hartman, C. Kilic, L.T. Wang (2006)]
• New Physics at TeV scale and Precision Electroweak (slides) [S. Godfrey (2005)]
• Search for Z' with ATLAS (multiple slides)
• Search for New Gauge Bosons (multiple slides)
• Z-prime Gauge Bosons at the Tevatron [M. Carena, A. Daleo, B.A. Dobrescu, T.M.P. Tait (2004)]
• Prospects of a Search for a New Massless Neutral Gauge Boson at the ILC [E. Boos, V. Bunichev, H.J. Schreiber (2007)]
• How to study weakly coupled neutral vector bosons [A. Freitas (2004)]
• Z' Discovery Limits For Supersymmetric E_6 Models [J. Kang, P. Langacker (2004)]
  : Z' discovery by jets may be improved by the prescale.
• E_6 multiplets and unification in extra dimensions [B. Brahmachari (2002)]
  : E6 exotics may exist at m_t scale.
• Physics with Jets at the LHC [J.W. Rohlf (2005)]
• A search for Z' bosons using dielectron mass & angular distribution at CDF (talk) [G. Veramendi (2005)]
  : PHENO2005 talk from CDF collaboaration on Z' search
• Some effects of a Z' vector boson (talk) [J. Boersma (2005)]
  : Z'_SM and Z'-W-W coupling
• HEAVY Z BOSON DECAYS TO W, Z AND HIGGS BOSONS IN E(6) SUPERSTRING MODELS [V.D. Barger, K. Whisnant (1987)]
  
• Heavy-Z-boson decays to two bosons in E6 superstring models [V.D. Barger, K. Whisnant (1987)]
• Z' studies at the LHC: an update [M. Dittmar, A.S. Nicollerat, A. Djouadi (2003)]
• Distinguishing Between Models with Extra Gauge Bosons at the ILC [S. Godfrey, P. Kalyniak, A. Tomkins (2005)]
  : Using e-, e+ polarizations, Z' couplings can be measured precisely.
• Determination of Z' Gauge Couplings to Quarks and Leptons at Future Hadron Colliders [F. del Aguila, M. Cvetic, P. Langacker (1993)]
• Review of Z' Physics at Future Colliders [F. del Aguila, M. Cvetic, P. Langacker (1993)]
• Reconstruction of the Extended Gauge Structure from Z' Observables at Future Colliders [F. del Aguila, M. Cvetic, P. Langacker (1995)]
• Z' signal from the LEP2 data [A.V. Gulov, V.V. Skalozub (2006)]
• Probing a Very Narrow Z' Boson with CDF and D0 Data [D. Feldman, Z. Liu, P. Nath (2006)]
• Higgs and Z' Phenomenology in B-L extension of the Standard Model at LHC [W. Emam, S. Khalil (2007)]
• Like-sign dilepton signals from a leptophobic Z' boson [F. del Aguila, J.A. Aguilar-Saavedra (2007)]
  
• Physics performances for Z' searches at 3 TeV and 1.5 TeV CLIC [J. Blaising, J.D. Wells (2012)]
• The mixing angle of Z-Z'
  The mixing angle of Z-Z' is constrained to be theta < (a few) * 0.001 by the precision measurement of the coupling constants at the Z pole at LEP.
  
  • ZZ' Mixing in Presence of Standard Weak Loop Corrections [A. Leike, S. Riemann, T. Riemann (1998)]
  • Use of Z lepton asymmetry to determine mixing between Z boson and Z' boson of E6 superstring theory [V.D. Barger, K. Whisnant (1987)]
• Forward-Backward Asymmetry to distinguish the models
  The Forward-Backward asymmetry of the vector boson contains the information of the charge assignments. It is useful in identifying gauge bosons.
  
  
  
  
  
  A_FB versus E6 mixing angle for M_Z' = 0.2 TeV (dotted-dashed), 0.3 TeV (dotted) at p pbar and M_Z' = 0.5 TeV (solid) and 1 TeV (dashed) at p p hadron colliders; A_FB versus rapidity for M_Z' = 1 TeV at p p collider
  
  
  • The Measurement of FB Asymmetry in Electron-Positron Pairs (slides) [G. Veramendi (2004)]
  • New heavy gauge bosons in p p and p anti-p collisions [P. Langacker, R.W. Robinett, J.L. Rosner (1984)]
  • Forward-Backward Asymmetries in Hadronically Produced Lepton Pairs [J.L. Rosner (1995)]
  • Production, decays, and forward-backward asymmetries of extra gauge bosons in E6 [V.D. Barger, N.G. Deshpande, J.L. Rosner, K. Whisnant (1987)]
  • The forward-backward asymmetry with Z' effects in the process e^{+} e^{-} --> mu^{+} mu^{-} [W.G. Ma, L.Z. Sun, Y.Y. Liu, Y. Jiang, C.H. Chang (1994)]
  • Les Houches "Physics at TeV Colliders 2003" BSM Working Group: Summary Report (See Part XX) [BSM WG (2004)]
• Distinguishing the Resonances
  Distinguishing the resonance from new gauge boson from that of the KK excited states
  • Distinguishing Indirect Signatures of New Physics at the NLC: Z' Versus R-Parity Violation [T.G. Rizzo (1998)]
  • Distinguishing Kaluza-Klein Resonances From a Z' in Drell-Yan Processes at the LHC [T.G. Rizzo (2001)]
  • Kaluza-Klein/Z' Differentiation at the LHC and Linear Collider [T.G. Rizzo (2003)]
• Atomic Parity Violation
  The Z' interaction between the nucleus and the electrons in an atom can result the atomic parity violation.
  • Role of Present and Future Atomic Parity Violation Experiments in Precision Electroweak Tests [J.L. Rosner (2001)]
• Z' decay
• Supersymmetric Contributions to the Decay of an Extra Z Boson [T. Gherghetta, T.A. Kaeding, G.L. Kane (1998)]
• Z' mass limits, masses and coupling of higgs bosons, and Z' decays in an E6 superstring based model [J.F. Gunion, L. Roszkowski, H.E. Haber (1987)]
• Z' signal from the LEP2 data [A.V. Gulov, V.V. Skalozub (2006)]

---

Nontrivial Collider signatures of Z'

• Z' can be a factory of new and old particles. Especially, multi-lepton Z' resonance can enjoy both resonance and clean lepton signals at the hadron collider experiments, revealing the effect of new particles between the Z' and final leptons.

• New physics search at the LHC via Z' resonance [H.S. Lee (2010)]
  

• 4-lepton Z' resonance (via sneutrino)

Leptophobic (or Baryonic) Z'

Implications of Z' [EWPT sector]

• Electroweak Precision Test
  The existence of the Z' would change the electroweak precision test, for an example, through Z-Z' mixing. The TeV-scale Z' boson with a family-nonuniversal coupling may improve the EW Precision Data fitting.
  • Indications for an Extra Neutral Gauge Boson in Electroweak Precision Data [J. Erler, P. Langacker (1999)]
  • Electroweak Precision Data and a Heavy Z' [A. Kundu (1995)]
  • Constraints on additional Z bosons [P. Langacker, M. Luo (1992)]
  • Implications of Generalized Z-Z' Mixing [K.S. Babu, C. Kolda, J. March-Russell (1997)]
  • Constraints on Extended Neutral Gauge Structures [J. Erler, P. Langacker (1999)]
  • The Z' reconsidered [A. Ferroglia, A. Lorca, J.J. van der Bij (2006)]
• Leptophobic Z'
  If Z' is leptophobic the dileptonic decay modes would not make a resonance peak. Also the large mixing between Z and Z' would be possible. Since the current experimental lower limit on Z' mass is based on the leptonic channels, less bound would be allowed for the leptophobic Z' gauge boson.
  • Flavour-Changing Neutral Currents and Leptophobic Z' Gauge Bosons Authors: Karine Leroux [K. Leroux, D. London (2001)]
  • Limits on a Light Leptophobic Gauge Boson [A. Aranda, C.D. Carone (1998)]
  • Constraints on leptophobic Z' models from electroweak experiments [Y. Umeda, G.C. Cho, K. Hagiwara (1998)]
  • Baryonic Z' connection of LEP R_{b,c} data with Tevatron (W,Z,\gamma)b\bar b events [V.D. Barger, K. Cheung, P. Langacker (1996)]
  • Gauge Kinetic Mixing and Leptophobic Z' in E_6 and SO(10) [T.G. Rizzo (1998)]
  • Leptophobic U(1)'s and the R_b - R_c Crisis [K.S. Babu, C. Kolda, J. March-Russell (1996)]

Implications of Z' [CP and FCNC sector]

• FCNC (Flavor Changing Neutral Current) and CP violation
  The family non-universal coupling of the Z' may be possible, especially in a certain string-motivated models. In that case, the tree-level FCNC mediated by Z' is possible. The recent B-decay anomalies such as B --> phi K_S and B --> pi K can be successfully explained with the enhanced electroweak penguin sector provided by the flavor-changing Z' without conflicts with B --> eta' K_S or Mercury EDM constraints. Further, the flavor-changing Z' can be source of the 2.5 sigma deviation of A_b (See PDG EWPT review [J. Erler, P. Langacker (2003)])
  
  [B --> pi K] and [B --> phi K_S] mediated by flavor-changing Z'
  
  
  
  [B_S --> mu mu] mediated by flavor-changing Z'
  
  
  • String Consistency for Unified Model Building [S. Chaudhuri, S.W. Chung, G. Hockney, J. Lykken (1995)]
  • Flavor Changing Effects in Theories with a Heavy Z' Boson with Family Non-Universal Couplings [P. Langacker, M. Plumacher (2000)]
  • The impact of lepton-flavor violating Z' bosons on muon g-2 and other muon observables [B. Murakami (2002)]
  • CP Violation in Supersymmetric U(1)' Models [D.A. Demir, L.L. Everett (2004)]
  • Explicit CP violation in a MSSM with an extra U(1)' [S.W. Ham, E.J. Yoo, S.K. OH (2007)]
  • Z' Mediated Flavor Changing Neutral Currents in B Meson Decays [V. Barger, C.W. Chiang, P. Langacker, H.S. Lee (2004)]
  • Solution to the B --> pi K Puzzle in a Flavor-Changing Z' Model [V. Barger, C.W. Chiang, P. Langacker, H.S. Lee (2004)]
  • Exclusive B-> M \nu \bar{\nu} (M= \pi, K, \rho, K^*) Decays and Leptophobic Z' Model [J.H. Jeon, C.S. Kim, J. Lee, C. Yu (2006)]
  • Nonuniversal Z' couplings in B decays [C.H. Chen, H. Hatanaka (2006)]
  • Semileptonic Lambda(b)-->Lambda neutrino antineutrino decay in the Leptophobic Z-prime model [B.B. Sirvanli (2007)]
  • K+ -> pi+ nu nu(bar) and FCNC from non-universal Z' bosons [X.G. He, G. Valencia (2004)]
  • D-bar D mixing constraints on FCNC with a non-universal Z' [X.G. He, G. Valencia (2007)]
    Leptophobic models can have a sizable flavor-changing in the quark sector even if the recent measurement of B --> K(*) l+ l- constrains flavor-chaning Z' significantly.
  • Electroweak Penguin and Leptophobic Z' model [S. Baek, J.H. Jeon, C.S. Kim, C. Yu (2006)]
  • New physics upper bound on the branching ratio of B_s --> l+ l- [A.K. Alok, S.U. Sankar (2005)]
  • Family nonuniversal Z-prime and b to s Gamma decay [R. Sever, A. Aydemir (2003)]
  • Constraints on heavy Z' couplings from \Delta S = 2 B^- -> K^- K^- \pi^+ decay [S. Fajfer, P. Singer (2001)]
    
• Z' coupling to limited particles
  • On the phenomenology of a Z' coupling only to third-family fermions [A.A. Andrianov, P. Osland, A.A. Pankov, N.V. Romanenko, J. Sirkka (1998)]
  • Finding Z' bosons coupled preferentially to the third family at CERN LEP and the Fermilab Tevatron [K.R. Lynch, M. Narain, E.H. Simmons, S. Mrenna (2000)]
  • Flavour-changing neutral currents and leptophobic Z' gauge bosons [K. Leroux, D. London (2001)]
• Flavor-changing Z' in top quark physics
  • Effects of an extra Z' gauge boson on the top quark decay t --> c gamma [A. Cordero-Cid, G. Tavares-Velasco, J.J. Toscano (2005)]
  • Single Top-Quark Production in Flavor-Changing Z' Models [A. Arhrib, K. Cheung, C.W. Chiang, T.C. Yuan (2006)]
• Flavor-changing SM Z
  • Phenomenology of non-standard Z couplings in exclusive semileptonic b -> s transitions [G. Buchalla, G. Hiller, G. Isidori (2000)]

Implications of Z' [Neutrino sector]

• Dirac/Majorana Neutrino
  When the right-handed neutrinos have the U(1)' charge, the neutrinos are Dirac. However, there may be a mechanism to decouple the right-handed neutrinos from the U(1)' naturally when there are multiple U(1)' symmetries.
  • Neutrino Masses in Supersymmetric SU(3)_C x SU(2)_L x U(1)_Y x U(1)' Models [J. Kang, P. Langacker, T. Li (2004)]
  • Alternatives to the Seesaw: Extra Z's and Constraints on Large Extra Dimensions [P. Langacker (2003)]
  • Neutrino Physics (theory) [P. Langacker (2004)]
  • Neutrinoless Double Beta Decay and New Physics (slides) [J.W.F. Valle (2003)]
• Primordial Nucleosynthesis
  The Big Bang Nucleosynthesis (BBN) can provide the most stringent limits on the Z' mass (multi-TeV range) when the right-handed neutrinos are charged by TeV-scale U(1)'. For the E6 angle where right-handed neutrinos almost decouple from the Z', small Z' masses are also allowed.
  
  • Primordial Nucleosynthesis Constraints on Z' Properties [V. Barger, P. Langacker, H.S. Lee (2003)]
    
    
    
    
    BBN Constraint on Z' mass with the mixing angle of 2 U(1)'s in E6
    
    
  • Primordial nucleosynthesis corners the Z' [J.L. Lopez, D.V. Nanopolous (1990)]
    
• Supernova
  • Mini Z' Burst from Relic Supernova Neutrinos and Late Neutrino Masses [H. Goldberg, G. Perez, I. Sarcevic (2005)]
    

Implications of Z' [Neutralino sector]

• Neutralino Spectrum
  The neutralino in the U(1)' model has additional components such as Z'-ino and singlino. The additions can affect the neutralino coupling and the mass significantly. For an example, the lightest one can be very light and singlet dominated.
  • Neutralinos in E_6 inspired supersymmetric U(1)' models [S. Hesselbach, F. Franke, H. Fraas (2001)]
  • The Neutralino Sector in the U(1)-Extended Supersymmetric Standard Model [S.Y. Choi, H.E. Haber, J. Kalinowski, P.M. Zerwas (2006)]
    
    Neutralino components ratio for the low tan(beta) in a U(1)' model and the MSSM
    
    
• Singlino-dominated Neutralino
  • Supersymmetric extra U(1) models with a singlino dominated LSP [S. Nakamura, D. Suematsu (2006)]
  • Singlino dominating CDM in supersymmetric extra U(1) models [D. Suematsu (2005)]
  • Singlino-dominated Neutralinos in Extended Supersymmetric Models [S. Hesselbach, F. Franke (2002)]
  • Production of singlino dominated neutralinos in extended supersymmetric models [F. Franke, S. Hesselbach (2001)]
• Neutralino Relic Density
  In the U(1)' model, the lightest neutralino can give acceptable relic density through channels like Z-pole.
  • Cold Dark Matter Candidate in a Class of Supersymmetric Models with an Extra U(1) [B. de Carlos, J.R. Espinosa (1997)]
  • Electroweak Baryogenesis and Dark Matter in the nMSSM [A. Menon, D.E. Morrissey, C.E.M. Wagner (2004)]
  • Neutralino Relic Density in a Supersymmetric U(1)' Model [V. Barger, C. Kao, P. Langacker, H.S. Lee (2004)]
  
  Neutralino relic density in a U(1)' model and the MSSM
  
  
• Direct detection of the neutralino dark matter in a U(1)' model
  • Recoil Detection of the Lightest Neutralino in MSSM Singlet Extensions [V. Barger, P. Langacker, I. Lewis, M. McCaskey, G. Shaughnessy, B. Yencho (2007)]
  
  
• More dark matter in U(1)' models
  A SM singlet fermion can be a dark matter under a U(1)'.
  • U(1)' dark matter [D.E. Brahm, L.J. Hall (1990)]
  
  
• Muon g-2
  Muon g-2 provides the most stringent constraints to many new physics models. If the deviation of 2.4 ~ 2.7 sigma between the SM and the BNL E821 experiments is real, a viable TeV-scale model should be able to explain it. The supersymmetric Z' model (both one singlet and multiple singlets model) can explain it.
  • Muon Anomalous Magnetic Moment in a Supersymmetric U(1)' Model [V. Barger, C. Kao, P. Langacker, H.S. Lee (2004)]
    
    
    
    The supersymmetric contributions to muon (g-2) involves the loops of charginos and neutralinos.
    
    
    The 2.4 sigma muon g-2 deviation solution (orange) along with the CDM relic density solution (black square). The multiple singlets model is used with small tan beta value of 2.5.
    
    

Implications of Z' [Sneutrino sector]

• Sneutrino dark matter
  A right-handed sneutrino coupled to Z' can serve as a viable dark matter candidate satisfying all experimental constraints.
  
  • Revival of the Thermal Sneutrino Dark Matter [H.S. Lee, K.T. Matchev, S. Nasri (2007)]
    
    
    

    
    Relic density and direct detection constraints on sneutrino dark matter
    

Implications of Z' [Baryogenesis sector]

• Electroweak Baryogenesis (EWBG)
  A U(1)' model can provide a sufficiently large first order phase transition in the Electroweak phase transition.
  • Electroweak phase transitions in the MSSM with an extra U(1)' [S.W. Ham, E.J. Yoo, S.K. Oh (2007)]
  • Electroweak phase transition in MSSM with U(1)-prime in explicit CP violation scenario [S.W. Ham, S.K. Oh (2007)]
  • Electroweak Baryogenesis in a Supersymmetric U(1)' Model [J. Kang, P. Langacker, T. Li, T. Liu (2004)]
  • Z' boson and electroweak phase transition [B.B. Deo, L. Maharana (2001)]
    For a review talk of the Electroweak Phase Transition at Supersymmetric models, see:
  • Electroweak Phase Transition in the Supersymmetric Models (slides) [K. Funakubo (2004)]
  • TeV leptogenesis in Z-prime models and its collider probe [E.J. Chun(2005)]
    
    
    The first order phase transition of the EWBG in a U(1)' model
    
    
• B, L asymmetry
  • mu-term as the origin of baryon and lepton number asymmetry [D. Suematsu (2002)]

Implications of Z' [Higgs sector]

• Higgs spectrum
  Because of the mixing of the singlet and doublet Higgses, the LEP2 constraint of m_h > 104 GeV does not apply directly. A much smaller mass of the Higgs is allowed while not violating the LEP2 results. Higgs sector is one of the most sensitively altered sectors with a U(1)' symmetry and its breaking singlet Higgs.
  • Higgs Sector in Extensions of the MSSM [V. Barger, P. Langacker, H.S. Lee, G. Shaughnessy (2006)]
    
    
    
    
  The lightest Higgs mass spectrum in various MSSM extensions [top: doublet only (MSSM-like), bottom: mostly singlet]. The points under the LEP curve are allowed (Mh < 114 GeV is possible). The UMSSM is a U(1)'-extended MSSM.
  
  
  • The Higgs Sector in a U(1)' Extension of the MSSM [T. Han, P. Langacker, B. McElrath (2004)]
  • Higgs sector in the E_6 inspired SUSY model with extra U(1) factor (talk) [S.F. King, S. Moretti, R.B. Nevzorov (2005)]
  • Spectrum of Higgs particles in the ESSM [S.F. King, S. Moretti, R.B. Nevzorov (2006)]
  • CP Violation in Supersymmetric U(1)' Models [D.A. Demir, L.L. Everett (2005)]
  • Radiative Corrections to Higgs Masses in Z' Models [H. Amini (2003)]
  • Mass bound of the lightest neutral Higgs scalar in the extra U(1) models [Y. Daikoku, D. Suematsu (2000)]
  • One-Loop Effects in Supergravity Models with an Additional U(1) [D.A. Demir, N.K. Pak (1998)]
  
  
• Higgs at collider
  • Production and detection of the Higgs bosons of the simplest E6-based superstring-inspired model [J.F. Gunion, L. Roszkowski, H.E. Haber (1988)]
  • LEP Indications for Two Light Higgs Bosons and U(1)' Model [D.A. Demir, L. Solmaz, S. Solmaz (2005)]

Implications of Z' [Et Cetra]

• Cosmology
  • Z-Z' mixing and bounds on new neutral gauge bosons from SN 1987A data [T.G. Rizzo (1991)]

•  Dark Photon (vector coupling only) limits from [R.D. McKeown (2011)]

• Dark Photon explanation of the muon g-2 anomaly is ruled out [NA48/2 Collaboration (2015)]

• LHC search of dark photons
• Search for Light Resonances Decaying into Pairs of Muons as a Signal of New Physics [CMS (2011)]

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Parity Violation

• Atomic Parity Violation limit on light Z'
• Parity Violation Effects Induced By A New Gauge Boson [P. Fayet (1980)]
• Constraints on the parity-violating couplings of a new gauge boson [C. Bouchiat, P. Fayet (2005)]
• Polarized electron scattering with low momentum transfer
• "Dark" Z implications for Parity Violation, Rare Meson Decays, and Higgs Physics [H. Davoudiasl, H.S. Lee, W.J. Marciano (2012)]
• Muon Anomaly and Dark Parity Violation [H. Davoudiasl, H.S. Lee, W.J. Marciano (2012)]

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Axion approximation

• When light Z' has axial coupling, its production is similar to the axion (light pseudo Goldstone boson), as the Goldstone boson equivalence theorem says, which is often larger than gauge coupling. This can happen, for examples, in rare meson decays (K -> pi Z', B-> K Z') or Higgs decays (H -> Z Z', Z' Z').

 

• "Dark" Z implications for Parity Violation, Rare Meson Decays, and Higgs Physics [H. Davoudiasl, H.S. Lee, W.J. Marciano (2012)]
• Vector Higgs-portal dark matter and the invisible Higgs [O. Lebedev, H.M. Lee, Y. Mambrini (2012)]

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Long-Range Interaction  (mZ' ~ massless)

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Constraints

•  Lee and Yang's paper first discussed that gravitational equivalence tests (Eotvos-type experiments) can constrain a long-range interaction with baryon number
• Conservation of Heavy Particles and Generalized Gauge Transformations [T.D. Lee, C.N. Yang (1955)]
• Okun explored the lepton number case
• Leptons and Photons [L. Okun (1996)]
• Review article on long-range interaction
• Long range forces in the universe [A.D. Dolgov (1999)]

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Effect on neutrino oscillation

• Long-range interaction can affect neutrino oscillation if its coupling to each species is different.
• Constraints on flavour-dependent long-range forces from atmospheric neutrino observations at Super-Kamiokande [A.S. Joshipura, S. Mohanty (2004)]
• Neutrino oscillations in the Sun probe long-range leptonic forces [J.A. Grifols, E. Masso (2004)]
• Explanation of MINOS anomaly in nu_mu, anti-nu_mu disappearance (anomaly is gone now).
• Gauged L_mu - L_tau and different Muon Neutrino and Anti-Neutrino Oscillations: MINOS and beyond [J. Heeck, W. Rodejohann (2011)]
• Long-Range Lepton Flavor Interactions and Neutrino Oscillations [H. Davoudiasl, H.S. Lee, W.J. Marciano (2011)] 

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Connections to astrophysical anomaly

• Radiatively decaying scalar dark matter through U(1) mixings and the Fermi 130 GeV gamma-ray line [J.C. Park, S.C. Park (2012)]