Edited by HyeSung Lee
This is an online "The Z' Hunter's Guide" to provide a basic
but uptodate review to people who are interested in Z' physics.
At this point, it is just a collection of the links to some Z'
papers I personally think useful.
I plan to keep updating and refining it until it becomes a
comprehensive review of the Z' physics.
Please let me know your ideas and suggestions to improve this site.
We define our Z' as the new force carrier of an additional U(1)
gauge symmetry unless otherwise indicated.
Overview Software package for Z'
Some printed reviews on Z'
Z' meetings
Useful links
Hunting fields (Direct Z' resonance search)
 Tevatron (at Fermilab)
 LHC (at CERN)
 CEBAF (at JLab)
 Microtron (at Institute of Nuclear Physics in Mainz)
 ILC (Future)
 CLIC (Futre)
General Discussions
Possible sources of resonances (Z'like signals)
 U(1)' (additional U(1) symmetry)
 Part of nonAbelian gauge symmetry such as SU(2)_R (the
third component)
 KaluzaKlein excitations in extra dimension.
 String resonance
Sources of U(1)'
 GUT
 Extra Dimension
 Superstring

Classification of Flat Directions in Perturbative Heterotic Superstring Vacua with Anomalous U(1) [G. Cleaver, M. Cvetic, J.R. Espinosa, L.L. Everett, P. Langacker (1997)]

Physics Implications of Flat Directions in Free Fermionic Superstring Models I: Mass Spectrum and Couplings [G. Cleaver, M. Cvetic, J.R. Espinosa, L.L. Everett, P. Langacker, J. Wang (1998)]

Physics Implications of Flat Directions in Free Fermionic Superstring Models II: Renormalization Group Analysis [G. Cleaver, M. Cvetic, J.R. Espinosa, L.L. Everett, P. Langacker, J. Wang (1998)]

New Gauge Bosons from String Models [M. Cvetic, P. Langacker (1996)]

Toward Realistic Intersecting DBrane Models [R. Blumenhagen, M. Cvetic, P. Langacker, G. Shiu (2005)]
 Strong Dynamics
 Little Higgs

Electroweak symmetry breaking from dimensional deconstruction [N. ArkaniHamed, A.G. Cohen, H. Georgi (2001)]

The Minimal Moose for a Little Higgs [N. ArkaniHamed, A.G. Cohen, E. Katz, A.E. Nelson, T. Gregoire, J.G. Wacker (2002)]

Phenomenology of the Little Higgs Model [T. Han, H.E. Logan, B. McElrath, L.T. Wang (2003)]
 Stueckelberg mechanism

How Stueckelberg Extends the Standard Model and the MSSM [B. Kors, P. Nath (2004)]

A Supersymmetric Stueckelberg U(1) Extension of the MSSM [B. Kors, P. Nath (2004)]

Aspects of the Stueckelberg Extension [B. Kors, P. Nath (2005)]

The Stueckelberg Z Prime at the LHC: Discovery Potential, Signature Spaces and Model Discrimination [D. Feldman, Z. Liu, P. Nath (2006)]

Extraweakly Interacting Dark Matter [D. Feldman, B. Kors, P. Nath (2006)]

Hidden fermion as millicharged dark matter in Stueckelberg Z' model [K. Cheung, T.C. Yuan (2007)]

The Stueckelberg Extension and Milli Weak and Milli Charge Dark Matter [D. Feldman, Z. Liu, P. Nath (2007)]
U(1)' Symmetry Breaking at TeVscale
 One or more additional scalar fields are required to break the U(1)' symmetry.
 U(1)' symmetry breaking can be related to the EWSB and
SUSY breaking especially when they are broken at TeVscale.
 Especially, the TeVscale U(1)' model can explain the
muproblem.

The muterm in the MSSM (Minimal Supersymmetric Standard
Model) is the only dimensionful parameter in the
supersymmetry conserving sector.
To have the electroweak symmetry breaking at the
rightorder, mu should be of the same order of supersymmetry
breaking (TeVscale) but the MSSM does not explain its
origin.
The mu in a U(1)' model is the vacuum expectation value of
the singlet Higgs that is broken at TeV scale.
Since it is the continuous gauge symmetry, it does not have
the domain wall problem which is invoked in the
NMSSM (NexttoMinimal Supersymmetric Standard Model) that
has the singlet with the discrete symmetry.

There are more explicit models for the TeVscale supersymmetric U(1)' that solve the muproblems.
 BottomUp rationale for the TeVscale Z'
 TopDown rationale for the TeVscale Z'
 SUSY breaking and U(1)'
 Anomalous Z' model (Z' > Z Z, gamma Z)
Other Solutions to the muproblem
besides the nonanomalous U(1)' symmetry at TeVscale

Another solution of the muproblem: The muterm is absent by
a symmetry but an effective muterm is
generated by nonrenormalizable operators

A number of string models possess nonrenormalizable terms
in the Kahler potential, which are proportional to H1 H2,
and may thus provide a resolution to the muproblem.

In Erice 1992 Proceedings From Superstrings to Super
gravity (World Scientific 1994, M. Duff et al., eds.), p
234. [V. Kaplunovsky, J. Louis]

Effective MuTerm in Superstring Theory [I. Antoniadis, E. Gava, K.S. Narain, T.R. Taylor (1994)]

Moduli spaces and target space duality symmetries in (0,2) Z_N orbifold theories with continuous Wilson lines [G. Lopes Cardoso, D. Luest, T. Mohaupt (1994)]

Another solution of the muproblem: With an anomalous U(1)'
symmetry

This anomalous U(1)' symmetry was originally introduced to explain the
Yukawa textures.

The anomaly may be cancelled by the GreenSchwarz mechanism.

Common solution of the muproblem and strong CPproblem.
Challenges in TeVscale Z' model building
 The U(1)' charge assignments should be careful chosen to make
the model anomalyfree. (GUToriginated U(1)'s are
automatically anomalyfree.)
 It is not easy to embed a TeVscale U(1)' in a GUT model.
The E6 GUT, for example, cannot provide the TeVscale Z'
since the E6 exotics of the TeVscale would induce a fast
proton decay.

Stringderived models also have exotics (such as color
triplets) that could mediate a too fast proton decay.
 If the righthanded neutrinos are charged by U(1)' of
TeVscale, the neutrinos would be Dirac neutrinos unless in
the limit the righthanded neutrinos charges are zero.
It loses the advantage of the simplicity of the seesaw
mechanism available for the Majorana neutrinos.
 Electroweak precision data is already well explained by the
Standard Model.
U(1)' and Proton Decay and also exotic fields
 U(1)' may protect the proton decay
 The U(1)' anomaly cancellation may require the exotic fields. Their coupling and masses can get the cosmological constraints.
Problems in the exotics
 U(1)' anomaly cancellation may require the exotic quarks and
More Z' Models
 Anomalyfree U(1) family symmetry
 Familydependent U(1)' charge and the nonholomorphic
soft terms can provide anomalyfree U(1)' model.
 Massless Z' is possible through a high dimensional operator.
 Milicharged particles from the kinetic mixing of photon and another U(1)_ex gauge boson may explain the PVLAS experiment.
 Z' Model building is posible without an exotic particle that couples to SM
gauge bosons
 A new longrange force coupling is constrained to be
small.
 A peculiar extra U(1) with anomaly cancellation in an economical way
 Proton decay and chirality issue
 Rparity may not be necessary.
 Generic Dbrane string models predict U(1)'.
 U(1)' in NonCommutative physics

U(1)_x model that solves the tachyonic slepton problem of AMSB.

U(1) gauge field localed on brane can have a milicharge.

The generalization of the BL symmetry with generationdependent lepton
charges leads to neutrino masses induced by operators of high
dimensionality.

Shadow Higgs
 331 model
 U(1)_B
General Z' properties LandauYang theorem: Z' (massive vector boson) cannot decay into 2 photons (massless vector boson)
 Z' > ZZ decay is possible.
 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.
Heavy Z' (mZ' ~ EW/TeV scale)
Implications of Z' [General]
Direct Implications of Z'
 Direct Collider search of the Resonance
The direct discovery channel of the Z' would be the observation of the resonance peak of the Z' in difermion channels. Especially the dilepton channel provides very clean signals without much background.
 Various analysis techniques for direct Z' resonance search
 Combined limit on spin1 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 cdcu 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)

Zprime 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'WW coupling

HEAVY Z BOSON DECAYS TO W, Z AND HIGGS BOSONS IN E(6) SUPERSTRING MODELS [V.D. Barger, K. Whisnant (1987)]

HeavyZboson 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 BL extension of the Standard Model at LHC [W. Emam, S. Khalil (2007)]

Likesign dilepton signals from a leptophobic Z' boson [F. del Aguila, J.A. AguilarSaavedra (2007)]
 Physics performances for Z' searches at 3 TeV and 1.5 TeV CLIC [J. Blaising, J.D. Wells (2012)]
 The mixing angle of ZZ'
 ForwardBackward Asymmetry to distinguish the models
The ForwardBackward 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 (dotteddashed), 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 ElectronPositron Pairs (slides) [G. Veramendi (2004)]

New heavy gauge bosons in p p and p antip collisions [P. Langacker, R.W. Robinett, J.L. Rosner (1984)]

ForwardBackward Asymmetries in Hadronically Produced Lepton Pairs [J.L. Rosner (1995)]

Production, decays, and forwardbackward asymmetries of extra gauge bosons in E6 [V.D. Barger, N.G. Deshpande, J.L. Rosner, K. Whisnant (1987)]

The forwardbackward 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
 Atomic Parity Violation
 Z' decay
Nontrivial Collider signatures of Z' Z' can be a factory of new and old particles. Especially, multilepton 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.
 4lepton Z' resonance (via sneutrino)
 6lepton Z' resonance (via heavy Higgs)
 2lepton + 2b Z' resonance (via light Higgs)
Leptophobic (or Baryonic) Z'
 If Z' does not couple to leptons, its constraint is significantly weaker and relatively light Z' is O(100 GeV) is possible.
Implications of Z' [EWPT sector]
 Electroweak Precision Test
 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.

FlavourChanging 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. MarchRussell (1996)]
Implications of Z' [CP and FCNC sector]
 FCNC (Flavor Changing Neutral Current) and CP violation
The family nonuniversal coupling of the Z' may be
possible, especially in a certain stringmotivated
models.
In that case, the treelevel FCNC mediated by Z' is
possible.
The recent Bdecay anomalies such as B > phi K_S and B
> pi K can be successfully explained with the enhanced electroweak
penguin sector provided by the flavorchanging Z'
without conflicts with B > eta' K_S or Mercury EDM constraints.
Further, the flavorchanging 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 flavorchanging Z'
[B_S > mu mu] mediated by flavorchanging 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 NonUniversal Couplings [P. Langacker, M. Plumacher (2000)]
 The impact of leptonflavor violating Z' bosons on muon g2 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 FlavorChanging 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 Zprime model [B.B. Sirvanli (2007)]

K+ > pi+ nu nu(bar) and FCNC from nonuniversal Z' bosons [X.G. He, G. Valencia (2004)]

Dbar D mixing constraints on FCNC with a nonuniversal Z' [X.G. He, G. Valencia (2007)]
Leptophobic models can have a sizable
flavorchanging in the quark sector even if the recent
measurement of B > K(*) l+ l constrains flavorchaning
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 Zprime 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
 Flavorchanging Z' in top quark physics
 Flavorchanging SM Z
Implications of Z' [Neutrino sector]
 Dirac/Majorana Neutrino
 Primordial Nucleosynthesis
The Big Bang Nucleosynthesis (BBN) can provide the most
stringent limits on the Z' mass (multiTeV range) when
the righthanded neutrinos are charged by TeVscale U(1)'.
For the E6 angle where righthanded 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
Implications of Z' [Neutralino sector]
 Neutralino Spectrum
 Singlinodominated Neutralino
 Neutralino Relic Density
Neutralino relic density in a U(1)' model and the MSSM
 Direct detection of the neutralino dark matter in a U(1)' model
 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 g2
Muon g2 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 TeVscale 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 (g2) involves
the loops of charginos and neutralinos.
The 2.4 sigma muon g2 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 righthanded 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)
 B, L asymmetry
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 (MSSMlike), bottom: mostly singlet]. The points under the
LEP curve are allowed (Mh < 114 GeV is possible). The UMSSM is a
U(1)'extended MSSM.

Higgs at collider
Implications of Z' [Et Cetra]
Light Z' (mZ' << EWscale)
Early studies Some of the earliest papers about light Z'
Motivations from dark matter explanation to astrophysical anomalies 511 keV gamma ray (observed by INTEGRAL satellite)
 Positron excess (observed by ATIC balloon and PAMELA satellite)
Direct Implications of Z'
 LHC search of dark photons
Parity Violation Atomic Parity Violation limit on light Z'
 Polarized electron scattering with low momentum transfer
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').
LongRange Interaction (mZ' ~ massless)
Constraints Lee and Yang's paper first discussed that gravitational equivalence tests (Eotvostype experiments) can constrain a longrange interaction with baryon number
 Okun explored the lepton number case
 Review article on longrange interaction
Effect on neutrino oscillation
Connections to astrophysical anomaly 
