An effective Lagrangian for scalar bound states in a dense medium

TL;DR

This paper proposes a nonlocal Lagrangian framework to describe scalar bound states in dense media, relevant for high-energy physics experiments, using a 1/N expansion approach to manage nonrenormalizable interactions.

Contribution

It introduces a novel nonlocal Lagrangian model for scalar interactions in dense media, employing a finite set of parameters and a 1/N expansion to handle nonrenormalizability.

Findings

The model can be renormalized with limited parameters.

Parameters are finite expansion coefficients, not independent couplings.

Constraints on coefficients are derived order by order.

Abstract

Recent analyses suggest that in TeV scales that will be made accessible at the LHC copious amounts of color scalar parton bound states may be produced. Would this be the case, the scalars would leave long enough to interact and this could lead to new physics. These interaction could be direct, but also take place with a mediation of the dense parton medium through which they propagate. Since multiple processes would have to be included, the latter case is too convoluted to be treated with perturbative methods applied to the Standard Model. We explore a possibility of describing such interaction by a nonlocal Lagrangian which is an infinite polynomial in the field variables, momentum and mass. We treat all scalars as identical, use a O(N)-symmetric Lagrangian, where N is the number of scalars and discuss the problem in 1/N expansion. Nonrenormalizable by all traditional criteria, such model still requires only a limited set of multiplicative renormalizations, provided that the parameters in the Lagrangian are not treated as an infinite set of independent coupling constants, but as finite expansion coefficients of the Lagrangian in powers of field variables, mass and momenta. The necessary constraints on the relative magnitudes of these coefficients can be determined order by order in a double series in the single coupling constant and 1/N.