[Paper Review] 130 GeV Gamma Ray Signal in NMSSM by Internal Bremsstrahlung

Gaurav Tomar, Subhendra Mohanty+1 more|arXiv (Cornell University)|Jun 16, 2013

Particle Detector Development and Performance3 citations

TL;DR

This paper proposes a 130 GeV bino dark matter candidate in the Next-to-Minimal Supersymmetric Standard Model (NMSSM) that explains the Fermi-LAT 130 GeV gamma-ray excess via internal bremsstrahlung ($\chi\chi\rightarrow f\bar{f}\gamma$). The model achieves correct relic density through stau coannihilation, satisfies the 125 GeV Higgs mass, evades XENON100 constraints, and predicts a detectable signal in XENON1T with a required boost factor of ~590.

ABSTRACT

There is a possible γ-ray signal at 130 GeV coming from the Galactic Center as seen by Fermi-LAT experiment. We give a SUSY dark matter model to explain this γ-ray feature in NMSSM. We show that in NMSSM, one can have a benchmark set in which the γ-ray signal arises from final state γ's in the $χχ o f \bar f γ$ annihilation of a 130 GeV bino dark matter requiring a boost factor of ~590 to fit the γ-ray signal. In addition, this benchmark set also gives the correct relic density, lightest Higgs mass of 125 GeV and is consistent with constraints on SUSY from LHC. This dark matter model evades the XENON100 constraint but is testable in a future XENON1T experiment.

Motivation & Objective

• To explain the 130 GeV gamma-ray signal from the Galactic Center observed by Fermi-LAT using a supersymmetric dark matter model.
• To construct a natural NMSSM scenario where the 130 GeV bino LSP produces the signal via internal bremsstrahlung without requiring fine-tuned resonances.
• To satisfy cosmological and collider constraints, including the correct relic density, 125 GeV Higgs mass, and consistency with LHC data.
• To ensure the model evades current direct detection limits (XENON100) while remaining testable in future experiments like XENON1T.
• To verify that the model does not overproduce electron-positron or antiproton fluxes beyond cosmic-ray background.

Proposed method

• Uses the NMSSM framework to introduce a singlet superfield, enabling natural higgsino mass generation via singlino-higgsino mixing.
• Employs internal bremsstrahlung ($\chi\chi\rightarrow f\bar{f}\gamma$) to enhance the photon final state, overcoming helicity suppression without requiring large mixing.
• Sets benchmark parameters with a 130 GeV bino LSP, low stau mass (~135 GeV), and large $\lambda \sim -0.62$ coupling to achieve correct relic density and Higgs mass.
• Applies micrOMEGAs 3.1 to compute annihilation cross-sections and fluxes, which are then fed into GALPROP for propagation in the Galaxy.
• Imposes an isothermal dark matter density profile and a boost factor of ~590 to match the Fermi-LAT gamma-ray signal.
• Evaluates direct detection cross-sections using effective Lagrangians and compares predictions with XENON100 and XENON1T experimental limits.

Experimental results

Research questions

• RQ1 Can the 130 GeV Fermi-LAT gamma-ray excess be explained by a 130 GeV bino dark matter candidate in the NMSSM via internal bremsstrahlung?
• RQ2 Is it possible to achieve the correct relic density and 125 GeV Higgs mass in this model without fine-tuning the $\mu$ parameter?
• RQ3 Does the model remain consistent with constraints from electron-positron and antiproton fluxes from cosmic rays?
• RQ4 Can the model evade current XENON100 direct detection limits while remaining detectable in XENON1T?
• RQ5 What is the required boost factor to fit the Fermi-LAT signal without overproducing other cosmic-ray species?

Key findings

• The 130 GeV bino dark matter model explains the Fermi-LAT 130 GeV gamma-ray signal via internal bremsstrahlung with a required boost factor of ~590.
• The model achieves the correct relic density through stau coannihilation, with stau mass near 135 GeV.
• The 125 GeV Higgs mass is realized with $\lambda \sim -0.62$ coupling in the scalar potential.
• The spin-independent direct detection cross-section is $\sigma^{p}_{\rm SI} = 5.8 \times 10^{-10}$ pb, below the XENON100 limit but within reach of XENON1T.
• The spin-dependent cross-section is $\sigma^{p}_{\rm SD} = 6.21 \times 10^{-6}$ pb, well below current bounds from Super-K and IceCube.
• The model does not overproduce electron-positron or antiproton fluxes, remaining consistent with Fermi-LAT and other cosmic-ray data.