REVIEW
Constraining the Z' Mass in 331 Models using Direct Dark Matter Detection
High Energy Physics - Phenomenology · Submitted 30 Jul 2013 · 37 references
Pith's verdict: A real, checkable Z' mass bound from LUX in the 3-3-1LHN model, undermined mainly by an abstract that claims more scope than the body delivers.
T0 · AI review
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Referee report
The paper
The paper claims
In a 331 extension of the Standard Model, the extra Z' boson must be heavier than about 2 TeV, or its exchange would have produced a dark matter signal that LUX did not see.
The reading
What carries the argument
The load-bearing object is the $Z'$ itself, acting as both annihilation mediator and scattering mediator. On the relic-density side, the authors implement the model in a customized micrOMEGAs, including 3- and 4-body final states and coannihilation among $N_1$, $N_2$ and $N_3$ (with masses varied within 10% of each other), and exhibit the resonance funnel at $M_{N_1} = M_{Z'}/2$ for $M_{Z'} = 0.8, 1.2, 1.6, 2$ TeV. On the scattering side, the Dirac fermion $N_1$ has a vector coupling to quarks, giving a spin-independent cross section of the form $σ_0 = μ^2 B_N^2 / 64π$ with $B_N = α_V^u (A+Z) + α_V^d (2A - Z)$, whose $A^2$ coherence enhancement is what makes the spin-independent channel the strongest handle even though the spin-dependent cross section is numerically larger. The scalar and pseudoscalar states $S_1$, $S_2$ and $P_1$ are argued to be irrelevant: no resonance arises from a light $S_1$, and $P_1$ exchange is $p$-wave suppressed.
Extended reading notes
Core claim
The paper's claim is that the 3-3-1LHN model's dark matter candidate $N_1$ can reproduce the observed relic density through $Z'$-mediated annihilation (with a resonance at $M_{N_1} = M_{Z'}/2$) plus coannihilation among the heavy neutral fermions, and that the spin-independent cross section this same $Z'$ produces off nuclei is large enough that the LUX 2013 limit excludes $M_{Z'} < 2$ TeV. The authors emphasize that the exclusion is largely independent of the dark matter mass, because only gauge couplings enter the scattering: the cross section is set by the $Z'$ mass and the WIMP mass alone. Translated through the model's mass relations, the bound says the symmetry-breaking scale sits at $v_{χ'} = 4$–$5$ TeV, dragging every new fermion, quark, scalar and gauge boson of the theory up to the few-TeV range. The authors present this as complementary to collider, flavour-changing-neutral-current, electroweak-precision and muon-decay limits on the same boson, and note that the bound should carry over, at least approximately, to other 331-like models where a singlet neutral fermion is the dark matter and the $Z'$ is the mediator.
Load-bearing premise
The whole bound rests on the spin-independent cross section being set entirely by tree-level $Z'$ exchange with the couplings listed in the paper's Table I, with no $Z$–$Z'$ mixing and with scalar exchange genuinely negligible.
Editorial extensions
If this is right
- If the bound holds, the symmetry-breaking scale of the model is pushed to $v_{χ'} \simeq 4$–$5$ TeV, so all the new quarks, neutral fermions, scalars and the charged gauge bosons $V^\pm$ and $U^0$ sit at a few TeV and are, in principle, within reach of the LHC.
- For $M_{N_1} < M_{Z'}/2$ the $Z'$ decays predominantly invisibly into $N_1 \bar{N}_1$ pairs, so the dilepton searches that constrain the right-handed-neutrino version of the model lose sensitivity and missing-energy searches become the relevant channel.
- The direct-detection bound is complementary to, and of comparable reach as, limits from colliders, flavour-changing neutral currents, $S$, $T$, $U$ oblique corrections and muon decay, so a future $Z'$ discovery would need to satisfy all of them at once.
- Because the scattering is governed by gauge couplings alone, the exclusion can be stated as a bound in the $(M_{Z'}, M_{N_1})$ plane rather than as a bound at one benchmark dark matter mass.
Reading between the lines
- The quoted 2 TeV number is a factor-of-a-few statement: a $Z$–$Z'$ kinetic mixing term, never discussed in the paper, would rescale the spin-independent cross section and move the bound proportionally, so it would be worth quantifying before treating 2 TeV as a hard, model-independent threshold.
- The near-independence from the dark matter mass follows from the pure vector coupling; any scalar-mediated contribution to the cross section would reintroduce mass dependence and could reopen sub-2-TeV $Z'$ masses near the resonance, where the relic density is anyway correct.
- Since the same vacuum expectation value fixes $M_{V^\pm}$ and $M_{U^0}$, a future measurement or exclusion of the charged gauge boson at the LHC would provide an independent cross-check on the direct-detection bound, or expose a tension between the two sectors.
- A joint likelihood combining invisible-width LHC searches with the xenon recoil limit would be sharper than either alone, because the two experiments probe the same coupling in complementary kinematic regimes.
Original abstract
We investigate a so-called 331 extension of the Standard Model gauge sector which accommodates neutrino masses and where the lightest of the new neutral fermions in the theory is a viable particle dark matter candidate. In this model, processes mediated by the additional $Z^{\prime}$ gauge boson set both the dark matter relic abundance and the scattering cross section off of nuclei. We calculate with unprecedented accuracy the dark matter relic density, including the important effect of coannihilation across the heavy fermion sector, and show that indeed the candidate particle has the potential of having the observed dark matter density. We find that the recent LUX results put very stringent bounds on the mass of the extra gauge boson, $M_{Z^{\prime}} \gtrsim 2$~TeV, independently of the dark matter mass. We also comment on regime where our bounds on the $Z^{\prime}$ mass may apply to generic 331-like models, and on implications for LHC phenomenology.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
We investigate a so-called 331 extension of the Standard Model gauge sector which accommodates neutrino masses and where the lightest of the new neutral fermions in the theory is a viable particle dark matter candidate. In this model, processes mediated by the additional $Z^{\prime}$ gauge boson set both the dark matter relic abundance and the scattering cross section off of nuclei. We calculate with unprecedented accuracy the dark matter relic density, including the important effect of coannihilation across the heavy fermion sector, and show that indeed the candidate particle has the potential of having the observed dark matter density. We find that the recent LUX results put very stringent bounds on the mass of the extra gauge boson, $M_{Z^{\prime}} \gtrsim 2$~TeV, independently of the dark matter mass. We also comment on regime where our bounds on the $Z^{\prime}$ mass may apply to generic 331-like models, and on implications for LHC phenomenology.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We investigate a so-called 331 extension of the Standard Model gauge sector which accommodates neutrino masses and where the lightest of the new neutral fermions in the theory is a viable particle dark matter candidate. | background 0.66 | 0.17 | 0.03 | asserted 0.89 |
| s1 | In this model, processes mediated by the additional $Z^{\prime}$ gauge boson set both the dark matter relic abundance and the scattering cross section off of nuclei. | background 0.74 | 0.21 | 0.04 | asserted 1.00 |
| s2 | We calculate with unprecedented accuracy the dark matter relic density, including the important effect of coannihilation across the heavy fermion sector, and show that indeed the candidate particle has the potential of having the observed dark matter density. | result 0.56 | 0.97 | 0.07 | asserted 0.53 |
| s3 | We find that the recent LUX results put very stringent bounds on the mass of the extra gauge boson, $M_{Z^{\prime}} \gtrsim 2$~TeV, independently of the dark matter mass. | result 1.00 | 0.93 | 0.89 | asserted 1.00 |
| s4 | We also comment on regime where our bounds on the $Z^{\prime}$ mass may apply to generic 331-like models, and on implications for LHC phenomenology. | interpretation 0.90 | 0.64 | 0.03 | hedged possibility 0.85 |
What was examined, and what was not
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- P abstract
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Figures
Showing 5 of the paper's 7 figures. See all figures in the PDF ↗ Figures reproduced from arXiv:1307.7802 by the authors.
References
How the literature uses it
44 arXiv papers cite this in 65 sentences
Papers citing it · 46 sentences without a confident label
Compares with it 4 papers
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As we can see, the LUX constraints on elastic WIMP-nucleon scattering cross section along with the correct relic density observed by Planck are able to establish a lower bound on $Z^'$ mass, $m_Z^' ≳2400$ GeV, compatible with a model independent analysis performed in Ref. [ref] , as well as a particular 331 model with left handed neutrinos in the leptonic triplet [ref] .
Higgs mass and right-handed sneutrino WIMP in a supersymmetric 3-3-1 model · Direct Detection · 0.97
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These limits represent significant improvement compared to previous bounds on $Z^'$ from 331 Models [ref] .
Limits on 331 vector bosons from LHC proton collision data · Limits on $Z^'_331$ · 0.98
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From these results we see that $M_Z^''>M_Z^' >M_Z$, recovering the $Z^'$ of the $331_RHN$ [ref] model, and the $Z$ boson reproduces the well established massive neutral gauge boson of SM.
A compact 341 model at TeV scale · Gauge bosons mass spectrum · 0.93
Cites it as support 2 papers
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This model is also consistent with all electroweak bounds, while offering plausible explanations to many open problems in particle physics, such as dark matter [ref] and the number of particle generations [ref] .
A 331 WIMPy Dark Radiation Model · INTRODUCTION · 0.96
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The mixing of $N_1$ and charged leptons has a negligible effect on the DM phenomenology [ref] .
Dark Matter as a Source for Lepton Flavor Violation · Dark Matter · 0.96
Cites it as background 13 papers
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A new massive and neutral $$ is an interesting feature of the low-energy limit of many extensions to the SM possessing a viable DM candidate [ref] .
Dirac-Fermionic Dark Matter in $U(1)_X$ Models · Dark Matter Phenomenology · 0.86
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Typically, in dark matter models the same couplings govern the relic density and the scattering cross section [ref] .
The Semi-Hooperon: Gamma-ray and anti-proton excesses in the Galactic Center · Annihilations · 0.89
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331 models [ref] are electroweak gauge extensions of the Standard Model (SM) which might address many questions left out by SM such as the charged quantization [ref] , the number of fermions generations [ref] , neutrinos oscillations, the Galactic Center gamma-ray excess [ref] as well as obey the direct detection bounds coming from the XENON100 and LUX experiments [ref] , the dark radiation [ref] observed by Planck [ref] among others.
Flavor Changing Neutral Current Processes in a Reduced Minimal Scalar Sector · Introduction · 0.98
What it cites · 32 sentences without a confident label
Uses the method or tool of 1 paper
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Our results were obtained numerically using the micrOMEGAs package [ref] and we let all coupling constants free to vary randomly.
micrOMEGAs3.1 : a program for calculating dark matter observables · Direct Detection and bounds on the $Z^'$ · 1.00
Uses data or values from 3 papers
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The red region is excluded by LUX 2013 limits [ref] .
First results from the LUX dark matter experiment at the Sanford Underground Research Facility · Direct Detection and bounds on the $Z^'$ · 0.85
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In particular, a recent and restrictive limit was found on the mass of the $Z^'$ boson for the 3-3-1 model with right handed neutrinos using CMS data [ref] , namely, $M_Z^' > 2.2$ TeV.
Bounds on $Z^\prime$ from 3-3-1 model at the LHC energies · Mass Eigenstates · 0.84
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Assuming SM couplings with fermions, restrictive bounds were derived on the mass of the $W^'$, namely $M_W^' > 2.55$ TeV at $95%$ C.L [ref] .
ATLAS search for a heavy gauge boson decaying to a charged lepton and a neutrino in pp collisions at sqrt(s) = 7 TeV · Gauge Bosons · 0.92
Compares with 4 papers
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Moreover, these limits are complementary to other limits coming from colliders [ref] , Flavor Changing Neutral Current processes [ref] , electroweak corrections to the S,T,U parameters [ref] , and from muon decay [ref] .
Heavy quark signals from radiative corrections to the $Z^{\prime}$ boson decay in 3-3-1 models · Direct Detection and bounds on the $Z^'$ · 0.81
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Moreover, these limits are complementary to other limits coming from colliders [ref] , Flavor Changing Neutral Current processes [ref] , electroweak corrections to the S,T,U parameters [ref] , and from muon decay [ref] .
FCNC in the 3-3-1 model with right-handed neutrinos · Direct Detection and bounds on the $Z^'$ · 0.81
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Moreover, these limits are complementary to other limits coming from colliders [ref] , Flavor Changing Neutral Current processes [ref] , electroweak corrections to the S,T,U parameters [ref] , and from muon decay [ref] .
Bounds on $Z^\prime$ from 3-3-1 model at the LHC energies · Direct Detection and bounds on the $Z^'$ · 0.81
Cites as background 14 papers
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A variety limits have been placed on the mass of this boson and they come from different sources [ref] and from different models.
FCNC in the 3-3-1 model with right-handed neutrinos · Mass Eigenstates · 0.94
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A variety limits have been placed on the mass of this boson and they come from different sources [ref] and from different models.
Heavy quark signals from radiative corrections to the $Z^{\prime}$ boson decay in 3-3-1 models · Mass Eigenstates · 0.94
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The phenomenological aspects associated with the five gauge bosons in the model have been thoroughly explored in Ref. [ref] , to which we refer the interested Reader.
Vector- and Scalar-Bilepton Pair Production in Hadron Colliders · Gauge Bosons · 1.00
Discussion
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