ar X iv : h ep - p h / 00 05 21 1 v 1 2 2 M ay 2 00 0 UT - 895 Bulk U ( 1 ) Messenger

We propose a new U(1) gauge interaction in the bulk in higher dimensional spacetime, which transmits supersymmetry-breaking effects on the hidden brane to the observable our brane. We find that rather small gauge coupling constant of U(1)bulk, αbulk ≃ 5× 10−4, is required for a successful phenomenology. This result implies the compactification length L of the extra dimension to be L−1 ≃ 2×1015 GeV for (4+1)dimensional spacetime. This large compactification length L is a crucial ingredient to suppress unwanted flavor-changing neutral currents and hence our proposal is very consistent with the Randall-Sundrum brane-world scenario. Most of supersymmetry (SUSY) breaking models in supergravity (even including gauge mediation models) assume a separation of the SUSY-breaking and the SUSY standardmodel sectors [1, 2]. However, the origin of the separation is not well understood, although such a separation is crucial to obtain phenomenologically consistent spectra for SUSY particles. The brane world proposed by Randall and Sundrum [3] provides a beautiful geometric explanation for the separation. That is, the hidden and observable sectors live on different three-dimensional branes separated by a gravitational bulk [4] in higher dimensional spacetime. It has been, recently, claimed [5, 3] that this brane separation produces the hidden and observable separation in the “conformal” frame in supergravity, which was proposed long time ago from a phenomenological ground [6]. It is a crucial observation in Ref. [6] that the above separation in the “conformal” frame induces a no-scale type Kähler potential in the Einstein frame, K(Φobs,Φ † obs,Φhid,Φ † hid) = −3 log ( 1− 1 3 fO(Φobs,Φ † obs)− 1 3 fH(Φhid,Φ † hid) )