Constraints on a scalar-tensor theory with an intermediate-range force by binary pulsars

Searching for an intermediate-range force has been considerable interests in gravity experiments. In this paper, aiming at a scalar-tensor theory with an intermediate-range force, we have derived the metric and equations of motion (EOMs) in the first post-Newtonian (1PN) approximation for general matter without specific equation of state and N point masses firstly. Subsequently, the secular periastron precession (omega) over dot of binary pulsars in harmonic coordinates is given. After that, (omega) over dot of four binary pulsars data (PSR B1913 + 16, PSR B1534 + 12, PSR J0737-3039 and PSR B2127 + 11C) have been used to constrain the intermediate-range force, namely, the parameters alpha and lambda. alpha and lambda respectively represent the strength of the intermediate-range force coupling and its length scale. The limits from four binary pulsars data are respectively lambda = (4.95 +/- 0.02) x 10(8) m and alpha = (2.30 +/- 0.01) x 10(-8) if beta = 1, where beta is a parameter like standard parametrized post-Newtonian parameter beta(PPN). When three degrees of freedom (alpha, lambda and (beta) over bar beta - 1) in 1 sigma confidence level are considered, it yields alpha = (4.21 +/- 0.01) x 10(-4), lambda = (4.51 +/- 0.01) x 10(7) m and (beta) over bar = (-3.30 +/- 0.01) x 10(-3). Through our research on the scalar-tensor theory with the intermediate-range force, it shows that the parameter a is directly related to the parameter gamma (alpha = (1 - gamma)/(1 + gamma)). Thus, this presents the constraints on 1 - gamma by binary pulsars which is about 10(-4) for three degrees of freedom.