On the determination of the leptonic decay constant fBc from QCD sum rules
Abstract The leptonic decay constant and the mass of the B c -meson are estimated using two versions of QCD sum rules. The predictions take into account the uncertainties due to the variations of the continuum threshold within the stability regions. Our optimal results are: f B c =300±65 MeV and M B c =6.25±0.20 GeV.
Several studies for the LHC luminosity upgrade pointed out the need for low-beta quadrupoles with apertures larger than the present baseline (70 mm). In this paper we focus on the design issues of a 130 mm aperture quadrupole. We first consider the Nb-Ti option, presenting a magnetic design with the LHC dipole and quadrupole cables. We study the electromagnetic forces and we discuss the field quality constraints. For the Nb3Sn option, we sketch three designs, two based on the LARP 10 mm width cable, and one on a larger cable with the same strand. The issue of the stress induced by the e.m. forces, which is critical for the Nb3Sn, is discussed using both scaling laws and finite element models.