Serendipity in dark photon searches (1801.04847v2)

Abstract: Searches for dark photons provide serendipitous discovery potential for other types of vector particles. We develop a framework for recasting dark photon searches to obtain constraints on more general theories, which includes a data-driven method for determining hadronic decay rates. We demonstrate our approach by deriving constraints on a vector that couples to the $B!-!L$ current, a leptophobic $B$ boson that couples directly to baryon number and to leptons via $B$-$\gamma$ kinetic mixing, and on a vector that mediates a protophobic force. Our approach can easily be generalized to any massive gauge boson with vector couplings to the Standard Model fermions, and software to perform any such recasting is provided at https://gitlab.com/philten/darkcast .

• The paper introduces a novel recasting framework that extends dark photon search results to constrain generalized vector boson models including B-L, leptophobic B, and protophobic vectors.
• The methodology leverages data-driven calculations and reinterprets diverse production mechanisms, such as bremsstrahlung and meson decays, to derive experimental constraints.
• The framework provides practical analytical tools that enable the particle physics community to explore Standard Model extensions and guide future experimental designs.

An Analytical Overview of "Serendipity in Dark Photon Searches"

The paper "Serendipity in Dark Photon Searches" introduces a strategic framework for expanding the utilization of dark photon search results to investigate a broader class of vector particles. This research leverages the discovery potential of dark photon experiments by developing a methodology to reinterpret their data, allowing constraints to be placed on more generalized theories beyond the specific dark photon model.

The authors provide a detailed analysis of three particular models: (i) a vector coupling to the \BL (baryon minus lepton) current, (ii) a leptophobic $B$ boson that interacts with baryon number and mixes kinetically with the photon (B--$\gamma$ mixing), and (iii) a vector mediating a protophobic force (one that interacts minimally with protons). These vector particles offer a rich domain of exploration due to their potential couplings with Standard Model (SM) fermions, which could manifest in numerous detectable experimental scenarios.

Framework for Recasting Experimental Searches

A significant contribution of this work is the development of a robust recasting framework. This framework enables the reinterpretation of experimental data originally collected for dark photon searches. Key components of this framework include:

• A data-driven method to compute hadronic decay rates, essential for low-mass vector bosons where perturbative predictions are unreliable.
• The ability to recalculate constraints on vector particles based on their production mechanisms, decay channels, and coupling constants relative to those of the dark photon.

In applying this methodology, the authors elaborate on several production mechanisms such as bremsstrahlung in electron and proton beams, electron-positron annihilation, Drell-Yan processes, meson decays, and vector meson mixing. These mechanisms are foundational for determining how constraints can be transferred from dark photon searches to the broader range of vector models considered.

Analytical Reapplication to Vector Boson Models

The exemplary application of the recasting framework to three models reinforces its versatility and generalizability. For instance, in the \BL model where coupling to neutrinos is inherent, searches initially aimed at invisible dark photon decays remain highly applicable. Notably, the constraints on the \BL model from dark photon searches present the most stringent limits across a significant portion of the parameter space.

The analysis of the $B$ boson model underscores the framework's capability to address anomalous current interactions—characterizing processes like $B_{u,d} \to KX$ decays with constraints recalculated in light of previous dark photon searches. For the protophobic vector model, which exhibits sensitivity to a distinct set of experimental conditions, the method remains consistent, adequately covering its unique phenomenological predictions.

Future Implications and Research Directions

The paper underscores the practicality of its approach in extending the scope of dark photon searches. By furnishing software and analytical tools for the particle physics community, this research prompts new investigations into SM extensions with vector particles. The capability to reinterpret existing experimental data prolifically cuts down the extensive resource requirements typically associated with conducting new experiments.

The ongoing alignment of particle phenomenology with experimental searches is vital given the vast parameter spaces involved. This research can be anticipated to catalyze further studies in vector boson phenomenology, especially in uncharted territories such as flavor-violating and CP-violating interactions, which were not covered here.

In conclusion, the work done in "Serendipity in Dark Photon Searches" links experimental ingenuity with theoretical innovation, significantly enhancing the capacity to discover new physics in the universe. Such advancements pave the way for future experimental design and theoretical model selection, ultimately contributing to our understanding of fundamental particles.