3 December 1998 Ž . Physics Letters B 442 1998 369–373 Chiral parameters in a QCD-motivated model with confined and massive gluons A.A. Natale 1 , P.S. Rodrigues da Silva 2 Instituto de Fisica Teorica, UniÕersidade Estadual Paulista, Rua Pamplona 145, 01405-900 Sao Paulo, SP, Brazil ´ ˜ Received 15 April 1998; revised 10 September 1998 Editor: M. Cvetic ˇ Abstract A one parameter model of a confined-gluon propagator has been formulated by Frank and Roberts recently, which has a great success explaining p y and r ymeson observables. We show, computing few chiral parameters, that a small variation of this model considering an infrared finite gluon propagator with a dynamically generated gluon mass, can also fit data related to the chiral symmetry breaking. This allows a direct interpretation for the unique parameter involved in the model as the gluon mass scale. q 1998 Elsevier Science B.V. All rights reserved. PACS: 14.40.Aq; 12.38.Lg; 12.39.Pn; 12.40.Yx The numerical study of QCD with the help of Ž . Schwinger-Dyson equations SDE , as well as Ž . Bethe-Salpeter equation BSE , provides a powerful nonperturbative method to tackle the problems of dynamical chiral symmetry breaking, and several other aspects of the hadronic physics, as has been wx recently reviewed in Ref. 1 . This method can be understood as a fully relativistic constituent quark model, and there are many recent calculations exem- wx plifying the remarkable success of this procedure 2 . It relates the hadronic properties to the Schwinger functions of quarks and gluons, therefore, when comparing the theoretical calculations to some low energy data, pseudoscalars masses and decay con- 1 E-mail: natale@ift.unesp.br 2 E-mail: fedel@ift.unesp.br stants for instance, we are learning how is the in- frared behavior of the quark and gluon propagators. As the time goes on this semi phenomenological tool may reveal to be even more successful than the relativistic quark model or the bag model. The phenomenological studies of SDE and BSE employ the present knowledge on the quark and gluon propagators in the full range of momenta. Ž. Although above a momentum of O 1 GeV we can rely on perturbative QCD, we do need some model- ing of the low-momentum region of the propagators. Moreover, it has been verified that quantities like the pion decay constant are dominated by the low-en- wx ergy behavior of the gluon propagator 3 . Therefore, their computation are extremely useful to estimate the infrared behavior of the gluon propagator. wx Recently Frank and Roberts 4 proposed a model of confined-gluon propagator based on an unique 0370-2693r98r$ - see front matter q 1998 Elsevier Science B.V. All rights reserved. Ž . PII: S0370-2693 98 01207-6