The Treiman-Yang Criterion: validating the Trojan Horse Method by experimentally probing the reaction mechanism

S S Perrotta ,A Cvetinović,T Parascandolo,R G Pizzone,I Indelicato,M La Commara,G G Rapisarda,S Romano,M Gulino,I Kres,A Di Pietro,M La Cognata,P Figuera,L Guardo,M Mazzocco,O Trippella ,R Spartá ,S Cherubini ,L Lamia ,D Lattuada ,C Spitaleri,G D’agata ,I Lombardo ,М Латтуада ,D Dell’aquila ,А Туміно

doi:10.1051/epjconf/201818402012

Abstract

Proper selection of the quasi-free (QF) break-up channel in a three-body reaction is a key aspect for the applicability of the Trojan Horse Method (THM). The Treiman-Yang (TY) Criterion is a model-independent experimental test for the dominance of the QF mechanism, and hence constitutes one of the strongest validity tests of the THM. An experiment was performed at LNS to apply the test to the d(10B, 7Be α)n reaction. Here, the criterion is described and some preliminary data from the experiment are shown.

Highlights

The quasi-free break-up mechanism, depicted in figure 1a for the d + 10B → 7Be + α + n reaction, can be described as the virtual interaction of the incident particle with only a cluster of the other reactant, named ‘participant’, emitted in a virtual decay, while the other cluster remains undisturbed
For instance if the participant is non-relativistic and has spin 1/2, the spin-averaged square-modulus amplitude |M|2 for the QF channel can be factorized into the amplitudes for the two virtual processes and the propagator
It is pivotal to correctly select the kinematical locus where the QF channel dominates: several validity tests are usually employed in the Trojan Horse Method (THM) analysis, but none of them is sufficient to completely ensure the dominance of the QF mechanism

Summary

Introduction

The quasi-free break-up mechanism, depicted in figure 1a for the d + 10B → 7Be + α + n reaction, can be described as the virtual interaction (here p + 10B → 7Be + α) of the incident particle (here 10B) with only a cluster (here p) of the other reactant, named ‘participant’, emitted in a virtual decay (here d → p + n), while the other cluster remains undisturbed. (figure 1b), but in principle many other mechanisms can contribute to the reaction amplitude. It is pivotal to correctly select the kinematical locus where the QF channel dominates: several validity tests are usually employed in the THM analysis (see [2, 3]), but none of them is sufficient to completely ensure the dominance of the QF mechanism

The Treiman-Yang Criterion

The Experiment