Catalog · Collider RS · CR006

CR006 $pp \to W_{KK}^{(1)} \to \ell \nu, tb$

Charged-current high-mass resonance (KK W)

Status REVIEWED VERIFIED High Code: NO Priority Medium

PDG / equivalent values

Observable	Value	Year	Experiment / source	Provenance
$m(W'_{SSM}$) lower bound in pp $ \to $ W' $ \to $ e $\nu$	> 6.0 TeV 95% CL (lower_limit)	2025	ATLAS	source ↑
$m(W'_{SSM}$) lower bound in pp $ \to $ W' $ \to \mu \nu$	> 5.6 TeV 95% CL (lower_limit)	2025	CMS	source ↑
$m(W'_{SSM}$) lower bound in combined pp $ \to $ W' $ \to $ e $\nu$ and $\mu \nu$	> 5.7 TeV 95% CL (lower_limit)	2022	CMS	source ↑
$m(W'_R$) lower bound in pp $ \to $ W' $ \to $ tb, leptonic top final states	> 4.3 TeV 95% CL (lower_limit)	2024	CMS	source ↑
$m(W'_L$) lower bound in pp $ \to $ W' $ \to $ tb, leptonic top final states	> 3.9 TeV 95% CL (lower_limit)	2024	CMS	source ↑

Why this constrains the RS scan

This collider-RS resonance search plays a different role from the low-energy flavor constraints already in the catalog. The current quark-scan methodology note quotes the anarchic-flavor benchmark crossing \[ M_{\rm KK}^{\min}(p50,\; g_s^\star=3) = 47.26~{\rm TeV}, \] with a 95\% acceptance crossing at $127.13$ TeV. Direct LHC searches for charged high-mass resonances therefore do not lead the constraint hierarchy in anarchic quark-flavor RS. Instead, CR006 is a cross-check and a handle on non-anarchic or deliberately lighter custodial-RS spectra where the flavor bound is weakened, aligned, or not imposed. The mapping to an RS charged KK gauge boson is model-dependent. The $\ell\nu$ limits assume sizable couplings to light quarks and leptons, a light invisible neutrino final state, and the SSM-like production rate and branching ratio. A realistic custodial $W^{(1)}_{\rm KK}$ can have suppressed light-fermion couplings and enhanced $tb$, $WZ$, or $Wh$ decays, so the SSM $\ell\nu$ limit is usually an aggressive proxy rather than a literal $M_{\rm KK}$ bound. The $tb$ searches are closer to the Agashe-style warped charged-gauge signal, but still require assumptions about the chiral coupling, total width, production coupling to initial-state light quarks, and whether the $tb$ branching fraction is saturated.

What's changed since the original paper

The post-2010 LHC history is a progression from earlier and partial-Run-2 searches to full-Run-2 leptonic and $tb$ limits. ATLAS $\ell\nu$, arXiv:1906.05609, is the key leptonic milestone: with 139 fb$^{-1}$ at 13 TeV it pushed the SSM $e\nu$ mass exclusion to 6.0 TeV and provided the companion ATLAS $\mu\nu$ channel bound. CMS $\ell\nu$, arXiv:2202.06075, used 138 fb$^{-1}$ at 13 TeV and excluded a combined SSM $W'$ below 5.7 TeV, while PDG records CMS as setting the strongest $\mu\nu$-specific 5.6 TeV limit. For $W'\to tb$, ATLAS arXiv:1801.07893 established a boosted all-hadronic Run-2 analysis with top-jet substructure. ATLAS arXiv:1807.10473 covered the lepton-plus-jets topology and combined it with the all-hadronic result, improving the right-handed benchmark reach. CMS arXiv:2104.04831 updated the all-hadronic channel with full-Run-2 data and deep-learning top/bottom tagging. CMS arXiv:2310.19893 is the current $tb$ anchor for this entry: with 138 fb$^{-1}$, it excludes narrow left- and right-handed $W'$ bosons below 3.9 and 4.3 TeV, respectively, and also publishes width-dependent limits.

Validity and model dependence

The experimental exclusions are robust statements about their stated signal models. Their RS reinterpretation is not automatic. The leptonic SSM limits assume SM-like $W'$ couplings to light quarks and charged leptons, an ordinary neutrino final state, and a line shape close to the benchmark used in the transverse-mass search. They lose force in leptophobic or third-generation-philic RS variants, and they can shift if $W'$-SM $W$ interference, heavy-neutrino decays, or large total widths are important. The $tb$ limits are closer to custodial-RS charged-vector phenomenology, but they still assume a simplified chiral $W'$ benchmark and a specified width. An RS implementation must compute the production coupling to the incoming partons, the $tb$, $WZ$, $Wh$, and exotic-fermion branching fractions, and the detector-level acceptance before using these as hard scan cuts.

Code coverage in this repo

NO. Greps over quarkConstraints/, qcd/, flavorConstraints/, neutrinos/, yukawa/, warpConfig/, solvers/, scanParams/, and tests/ found no $W'$, $W_{\rm KK}$, collider resonance, $\ell\nu$, or $tb$ direct-search implementation. The only ATLAS/CMS-like hit in those paths is tests/test\_alpha\_s.py:88--89, a CMS/RunDec running-coupling example unrelated to collider limits. Adjacent evidence confirms that the scan stores $M_{\rm KK}$ and evaluates low-energy constraints, not direct LHC searches: quarkConstraints/scan.py:418--439 writes $M_{\rm KK}$ and $\Delta F=2$ ratios, scanParams/scan.py:524--535 applies only the $\mu\to e\gamma$ LFV check, and quarkConstraints/deltaf2.py:316--560 matches and evaluates $\Delta F=2$ Wilson coefficients at $M_{\rm KK}$.

Implementation difficulty

HIGH. A faithful CR006 implementation requires a collider reinterpretation layer rather than a new scalar observable formula: signal generation or tabulated production cross sections for the chosen custodial-RS charged vector, branching-ratio calculation including heavy fermion partners, finite-width and interference handling, detector acceptance, and a likelihood or limit recast. A practical implementation would probably call an external recasting tool such as CheckMATE, MadAnalysis5, SModelS, or collaboration simplified-likelihood material rather than trying to reproduce the ATLAS/CMS selection internally.

Reason: Needs a collider reinterpretation workflow: RS charged-vector production and decays, branching fractions to tb/WZ/Wh/exotics, finite-width/interference handling, detector acceptance, and ATLAS/CMS likelihood or recast machinery.

Key references

Process-local source keys before bibliography consolidation are PDG2025\_WprimeSearches, ATLAS2019\_WprimeLnu, CMS2022\_WprimeLnu, CMS2024\_WprimeTbLeptonic, CMS2021\_WprimeTbHadronic, ATLAS2018\_WprimeTbLeptonJets, ATLAS2018\_WprimeTbHadronic, Agashe2008\_WarpedChargedGauge, and AgasheServant2004\_WarpedUnification.

display > 6.0 TeV

RESOLVED

Match snapshot line 14

L11: indirectly on the W' couplings). These limits are set for M_W' in the
L12: 0.15 - 7 TeV range and are based on approximately 140 fb^-1 at sqrt(s) =
L13: 13 TeV [18,21], with the most stringent limits reproduced in Fig. 85.1.
L14: ATLAS sets the strongest mass limit M_W' > 6.0 TeV in the Sequential SM
L15: (all limits in this mini-review are at the 95% CL)."
L16: 
L17: "In the mu nu channel, ATLAS and CMS set rate limits for M_W' in the

display > 5.6 TeV

RESOLVED

Match snapshot line 19

L16: 
L17: "In the mu nu channel, ATLAS and CMS set rate limits for M_W' in the
L18: 0.15 - 7 TeV range [18,21], with the strongest mass lower limit of
L19: 5.6 TeV in the Sequential SM set by CMS [21] using 138 fb^-1 of
L20: sqrt(s) = 13 TeV data, as shown in Fig. 85.1. When combined with the
L21: e nu channel assuming lepton universality, the upper limit on the
L22: sqrt(s) = 13 TeV cross section times branching fraction to l nu varies

display > 5.7 TeV

RESOLVED

Match snapshot line 20

L17: Model-independent limits are set on the production cross section of W'
L18: bosons decaying into lepton-plus-neutrino final states. In the sequential
L19: standard model, combining electron and muon decay channels excludes a W'
L20: boson with mass less than 5.7 TeV at 95% confidence level. Results on a
L21: Standard Model precision test, the oblique electroweak W parameter, are
L22: also presented using LHC data.

display > 4.3 TeV

RESOLVED

Match snapshot line 21

L18: with a relative decay width of 1%, with local and global significances of
L19: 2.6 and 2.0 standard deviations. Upper limits on production cross sections
L20: of W' bosons decaying to top and bottom quarks are set. Left- and
L21: right-handed W' bosons with m_W' below 3.9 and 4.3 TeV, respectively, are
L22: excluded at the 95% confidence level under the narrow-width assumption.
L23: Limits are also set for relative decay widths up to 30%.

display > 3.9 TeV

RESOLVED

Match snapshot line 21

L18: with a relative decay width of 1%, with local and global significances of
L19: 2.6 and 2.0 standard deviations. Upper limits on production cross sections
L20: of W' bosons decaying to top and bottom quarks are set. Left- and
L21: right-handed W' bosons with m_W' below 3.9 and 4.3 TeV, respectively, are
L22: excluded at the 95% confidence level under the narrow-width assumption.
L23: Limits are also set for relative decay widths up to 30%.