Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Leptogenesis and Neutrino Masses Via Pseudo-Dirac Gauginos

Cem Murat Ayber, Tammi Chowdhury, Seyda Ipek

TL;DR

This work develops a leptogenesis scenario within a $U(1)_{R-L}$-symmetric SUSY framework where pseudo-Dirac bino and wino act as right-handed neutrinos. The baryon asymmetry arises from CP-violating bino–antibino oscillations with out-of-equilibrium decays, while light neutrino masses are generated predominantly by the wino sector through a hybrid Type I + III inverse seesaw mechanism. Achieving both goals favors a decoupled spectrum with $M_{ ilde{B}} \sim \mathcal{O}(\mathrm{TeV})$, $M_{\rm sf} \gtrsim 50$ TeV, and a messenger scale $\Lambda_M \sim \mathcal{O}(10^7-10^8\,\mathrm{TeV})$, yielding potentially observable displaced-vertex signals at the LHC and future detectors. The study integrates a density-matrix Boltzmann treatment of bino oscillations with collider phenomenology, linking neutrino physics, baryogenesis, and long-lived particle searches in a testable supersymmetric framework.

Abstract

In a $U(1)_{R-L}$-symmetric supersymmetric model, pseudo-Dirac bino and wino can act like right-handed neutrinos, generating the light neutrino masses through a hybrid Type I + III inverse seesaw mechanism. We investigate such a model to accommodate the baryon asymmetry of the universe together with neutrino masses. A pseudo-Dirac gaugino goes under particle-antiparticle oscillations. Possible $CP$ violation in bino decays, induced by mixing with the neutrinos, can be enhanced in bino--antibino oscillations. Focusing on a long-lived bino, we show that its oscillations and decays can generate the observed baryon asymmetry while the wino is responsible for generating the neutrino masses. This mechanism requires a decoupled mass spectrum with a bino of mass $M_{\tilde{B}}\sim O({\rm TeV})$ and sfermions with mass $M_{\rm sf}\gtrsim 25$ TeV. Furthermore, for the bino to decay out-of-equilibrium before the electroweak sphalerons turn off, the messenger scale needs to be $Λ_M \sim O(10^7~ {\rm TeV})$. We discuss the displaced vertex signals at the LHC resulting from such a high messenger scale.

Leptogenesis and Neutrino Masses Via Pseudo-Dirac Gauginos

TL;DR

This work develops a leptogenesis scenario within a -symmetric SUSY framework where pseudo-Dirac bino and wino act as right-handed neutrinos. The baryon asymmetry arises from CP-violating bino–antibino oscillations with out-of-equilibrium decays, while light neutrino masses are generated predominantly by the wino sector through a hybrid Type I + III inverse seesaw mechanism. Achieving both goals favors a decoupled spectrum with , TeV, and a messenger scale , yielding potentially observable displaced-vertex signals at the LHC and future detectors. The study integrates a density-matrix Boltzmann treatment of bino oscillations with collider phenomenology, linking neutrino physics, baryogenesis, and long-lived particle searches in a testable supersymmetric framework.

Abstract

In a -symmetric supersymmetric model, pseudo-Dirac bino and wino can act like right-handed neutrinos, generating the light neutrino masses through a hybrid Type I + III inverse seesaw mechanism. We investigate such a model to accommodate the baryon asymmetry of the universe together with neutrino masses. A pseudo-Dirac gaugino goes under particle-antiparticle oscillations. Possible violation in bino decays, induced by mixing with the neutrinos, can be enhanced in bino--antibino oscillations. Focusing on a long-lived bino, we show that its oscillations and decays can generate the observed baryon asymmetry while the wino is responsible for generating the neutrino masses. This mechanism requires a decoupled mass spectrum with a bino of mass and sfermions with mass TeV. Furthermore, for the bino to decay out-of-equilibrium before the electroweak sphalerons turn off, the messenger scale needs to be . We discuss the displaced vertex signals at the LHC resulting from such a high messenger scale.

Paper Structure

This paper contains 9 sections, 42 equations, 5 figures, 1 table.

Table of Contents

  1. Introduction
  2. The Model
  3. Bino--Antibino Oscillations in the Early Universe
  4. Bino oscillations
  5. Other bino interactions
  6. Oscillations in the early universe
  7. The Baryon Asymmetry Of the Universe
  8. Signals
  9. Conclusions and Outlook

Figures (5)

  • Figure 1: Regions of bino decay widths relevant for leptogenesis with respect to the bino mass $M_{\tilde{B}}$ and the messenger scale $\Lambda_M$. Here we take $\tilde{m}=0.2 M_{\tilde{B}}$. In the bottom purple region, bino decays at a temperature above its mass, $T>M_{\tilde{B}}$. In the upper green region, bino lives long enough to decay below $T_{\rm EW}\simeq 130$ GeV, when sphalerons are no longer active.
  • Figure 2: The bino (orange) and antibino (purple) abundances for an initial asymmetry of zero. For $CP$ violating parameter we take $r=0.2$ and $\sin\phi=1$. With $M_{\tilde{B}}=1$ TeV and $\Lambda_M=4\times 10^7$ TeV, we have $\Gamma_{\tilde{B}}\simeq 2.5\times 10^{-5}$ eV.
  • Figure 3: The parameter space, $M_{\tilde{B}}$ vs the Majorana mass $m$, for which bino oscillations start between $T=M_{\tilde{B}}$ and $T_{\rm dec}$ for $\Lambda_M=4\times 10^7$ TeV with varying $T_{\rm dec}$ (upper) and $T_{\rm dec}\simeq 162.5$ GeV with varying $\Lambda_M$ (lower). (See \ref{['eq:moscregion']} and the accompanying text.) Dashed/blue and dashed-dotted/purple lines are for $M_{\rm sf}=50, {\rm ~and~}100$ TeV, respectively. In the bottom-shaded region, bino oscillations start after sphalerons turn off, whereas in the upper-shaded regions, oscillations are expected to start while bino is relativistic, $T>M_{\tilde{B}}$.
  • Figure 4: Lines of constant $\Delta_B$ for $\Lambda_M=4\times10^7$ TeV (upper) and $T_{\rm dec}\simeq 162$ GeV (lower) with $M_{\rm sf}=100$ TeV, $r=0.2$ and $\phi=\pi/2$. The observed value is $\sim 8\times 10^{-11}$.
  • Figure 5: The baryon asymmetry as a function of the Majorana mass $m$ for benchmark parameters $M_{\tilde{B}} =2$ TeV and $r\sin\phi=0.2$. The horizontal dashed line represents the observed yield of BAU, $\Delta B\sim 8.7\times 10^{-11}$. Solid/purple lines are for fixed $\Lambda_M=4\times 10^7$ TeV, and dotdashed/blue lines are for fixed bino lifetime $T_{\rm dec}=1.25\, T_{\rm sph}\simeq160 {\rm\, GeV}$, corresponding to $\Lambda_M\simeq 10^8$ TeV for $M_{\rm sf}=50,~75,{~\rm and~}100~ \rm TeV$. The lines are cut off using the condition in \ref{['eq:moscregion']}.