Source-linked AI summary
New Production Mechanism for Heavy Neutrinos at the LHC
P. S. Bhupal Dev, Apostolos Pilaftsis, Un-ki Yang
TL;DR
The paper addresses how to probe heavy-neutrino masses and light-to-heavy mixing at colliders despite limited sensitivity in conventional seesaw searches. It introduces infrared-enhanced t-channel photon-fusion production and finds substantially stronger direct mixing limits when this channel is included.
Problem
Collider tests of the seesaw require accessible heavy neutrinos with significant light-to-heavy mixing, while conventional probes may not simultaneously establish their Majorana nature and mixing.
Source: p. 1Method
The paper analyzes t-channel photon-mediated heavy-neutrino production, including the electroweak contributions needed for a gauge-invariant result and evaluating collider cross sections and limits.
Source: pp. 2–3Results
Including the new production mechanism improves existing ATLAS limits on |VµN|2 by almost 50% and by at least a factor of five at √s = 14 TeV.
Source: p. 4Takeaways & Limitations
The new production channel must be included in current and future LHC heavy-neutrino analyses to obtain the best direct mixing limits.
Source: p. 4The equivalent-photon approximation and factorization-scale choice introduce a 10–20% uncertainty for alternative pγ →Nℓ±j cross sections, although the dominant pp →Nℓ±jj contribution is unaffected for the main results.
Source: p. 3
Abstract
from arXiv · showhide
We study a new production mechanism for heavy neutrinos at the LHC, which dominates over the usually considered $s$-channel $W$-exchange diagram for heavy-neutrino masses larger than 100 - 200 GeV. The new mechanism is infrared-enhanced by $t$-channel $W\gamma$-fusion processes. This has important implications for experimental tests of the seesaw mechanism of neutrino masses, and in particular, for the ongoing heavy neutrino searches at the LHC. We find that the direct collider limits on the light-to-heavy neutrino mixing can be significantly improved, when this new production channel is properly taken into account. The scope of this new mechanism can equally well be extended to other exotic searches at the LHC.