We investigate left-right symmetric extensions of the standard model based on open strings ending on D-branes, with gauge bosons due to strings attached to stacks of D-branes and chiral matter due to strings stretching between intersecting D-branes. The left-handed and right-handed fermions transform as doublets under $Sp(1{)}_L$ and $Sp(1{)}_R$, and so their masses must be generated by the introduction of Higgs fields in a bifundamental $(\mathbf{2},\mathbf{2})$ representation under the two $Sp(1)$ gauge groups. For such D-brane configurations the left-right symmetry must be broken by Higgs fields in the doublet representation of $Sp(1{)}_R$ and therefore Majorana mass terms are suppressed by some higher physics scale. The left-handed and right-handed neutrinos pair up to form Dirac fermions which control the decay widths of the right-handed $W^{\prime }$ boson to yield comparable branching fractions into dilepton and dijet channels. Using the most recent searches at LHC13 Run II with 2016 data we constrain the $(g_R,m_{W^{\prime }})$ parameter space. Our analysis indicates that independent of the coupling strength $g_R$, gauge bosons with masses $m_{W^{\prime }}\gtrsim 3.5\mathrm{TeV}$ are not ruled out. As the LHC is just beginning to probe the TeV scale, significant room for $W^{\prime }$ discovery remains.

• Received 12 December 2016

DOI:https://doi.org/10.1103/PhysRevD.95.026011