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On Partial Compositeness and the CP asymmetry in charm decays

Boaz Keren-Zur, Paolo Lodone, Marco Nardecchia, Duccio Pappadopulo, Riccardo Rattazzi, Luca Vecchi

TL;DR

This paper examines whether Partial Compositeness can account for the observed direct CP asymmetry in charm decays while remaining compatible with flavor constraints. It analyzes two realizations: Composite Higgs models with a flavor scale around $m_\rho\sim10$ TeV and Supersymmetric implementations where the flavor structure is encoded in Yukawas and soft terms, including R-parity violation. The main finding is that CH with $m_\rho\sim10$ TeV can accommodate $\Delta a_{CP}$ but faces lepton-sector tensions, whereas SUSY PC with TeV-scale superpartners can saturate the CP asymmetry via LR chromomagnetic operators and offers distinctive collider and CP-violating signatures, including robust predictions for the neutron EDM and lepton flavor violation. The work emphasizes testable implications for EDMs, rare decays like $K^+\to\pi^+\nu\nu$, and LHC/RPV collider phenomenology, helping connect the flavor puzzle to the weak scale and guiding future experimental probes.

Abstract

Recently, the LHCb and CDF collaborations reported the measure of an unexpectedly large direct CP asymmetry in D meson decays. In this paper we ask if new physics associated with Partial Compositeness could plausibly explain this result. We find that Composite Higgs models with mass scale around 10 TeV can account for it, while marginally satisfying all other flavor constraints in the quark sector. The minimal framework is however inadequate in the lepton sector due to the strong constraint from μ to e γ. This tension can be efficiently alleviated by realizing Partial Compositeness within Supersymmetry. The resulting models can saturate the CP asymmetry in D decays for superpartner masses close to the TeV scale and somewhat large A-terms. The supersymmetric realization of Partial Compositeness also offers a predictive and phenomenologically viable organizing principle for R-Parity violation, and may result in very distinctive signatures at hadron colliders. With or without Supersymmetry, the neutron EDM is expected to be around the present experimental sensitivity.

On Partial Compositeness and the CP asymmetry in charm decays

TL;DR

This paper examines whether Partial Compositeness can account for the observed direct CP asymmetry in charm decays while remaining compatible with flavor constraints. It analyzes two realizations: Composite Higgs models with a flavor scale around TeV and Supersymmetric implementations where the flavor structure is encoded in Yukawas and soft terms, including R-parity violation. The main finding is that CH with TeV can accommodate but faces lepton-sector tensions, whereas SUSY PC with TeV-scale superpartners can saturate the CP asymmetry via LR chromomagnetic operators and offers distinctive collider and CP-violating signatures, including robust predictions for the neutron EDM and lepton flavor violation. The work emphasizes testable implications for EDMs, rare decays like , and LHC/RPV collider phenomenology, helping connect the flavor puzzle to the weak scale and guiding future experimental probes.

Abstract

Recently, the LHCb and CDF collaborations reported the measure of an unexpectedly large direct CP asymmetry in D meson decays. In this paper we ask if new physics associated with Partial Compositeness could plausibly explain this result. We find that Composite Higgs models with mass scale around 10 TeV can account for it, while marginally satisfying all other flavor constraints in the quark sector. The minimal framework is however inadequate in the lepton sector due to the strong constraint from μ to e γ. This tension can be efficiently alleviated by realizing Partial Compositeness within Supersymmetry. The resulting models can saturate the CP asymmetry in D decays for superpartner masses close to the TeV scale and somewhat large A-terms. The supersymmetric realization of Partial Compositeness also offers a predictive and phenomenologically viable organizing principle for R-Parity violation, and may result in very distinctive signatures at hadron colliders. With or without Supersymmetry, the neutron EDM is expected to be around the present experimental sensitivity.

Paper Structure

This paper contains 20 sections, 100 equations, 3 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Partial Compositeness
  3. Flavor Violation in Composite Higgs Models
  4. The CP Asymmetry in D Meson Decays
  5. Partial Compositeness and Supersymmetry
  6. The CP Asymmetry in D Meson Decays
  7. R-Parity Violation
  8. Collider Phenomenology
  9. Conclusions
  10. Standard Model inputs
  11. Phenomenological Constraints in the Composite case
  12. Dipole Operators
  13. Penguin Operators
  14. $\Delta F=2$ Transitions
  15. Top flavor changing neutral currents
  16. ...and 5 more sections

Figures (3)

  • Figure 1: Central value and $1\sigma$ band for the size of the scale $\Lambda/\sqrt{\hbox{Im}(c_{12,g}^{qu})}$ (see definition in Eq. (\ref{['eq:gen:1']})) that is needed in order to reproduce (\ref{['eq:deltaAcp']}) as a function of the SM contribution and taking Im$(\Delta R^{NP})=0.2$, see Eq. (\ref{['GenericACP']}).
  • Figure 2: Central value and $1\sigma$ band for the size of $\tilde{m}\sqrt{\tilde{m}/A_0 {\rm Im}(c_{12}^{u})_{LR}}$ required in order to reproduce (\ref{['eq:deltaAcp']}) as a function of the SM contribution and taking Im$(\Delta R^{NP})=0.2$, see Eq. (\ref{['SUSYACP']}).
  • Figure 3: A prototypical spectrum with R-handed up squark LSP avoiding missing energy signals and isolated lepton events. See text for details.