Signatures of spherical compactification at the CERN LHC

TeV-scale extra dimensions may play an important role in electroweak or supersymmetry breaking. We examine the phenomenology of such dimensions, compactified on a sphere $S^n$, $n\ge 2$, and show that they possess distinct features and signatures. For example, unlike flat toroidal manifolds, spheres do not trivially allow fermion massless modes. Acceptable phenomenology then generically leads to “nonuniversal” extra dimensions with “pole-localized” 4D fermions; the bosonic fields can be in the bulk. Because of spherical symmetry, some Kaluza-Klein (KK) modes of bulk gauge fields are either stable or extremely long-lived, depending on the graviton KK spectrum. Using precision electroweak data, we constrain the lightest gauge field KK modes to lie above $\simeq 4\mathrm{TeV}$. We show that some of these KK resonances are within the reach of the LHC in several different production channels. The models we study can be uniquely identified by their collider signatures.

Figure 1

Lifetime for the decay $B_{1\pm 1}\to G_{1\pm 1}\gamma$ as a function of the mass splitting, for $M_G=3–5\mathrm{TeV}$. Note that the $M_G$ mass dependence within the thickness of the curve cannot be resolved over the plot’s range.

Figure 2

Drell-Yan production rate as a function of the dilepton pair invariant mass of the neutral electroweak KK resonances at the LHC. The upper(lower) plot corresponds to the case where the lightest KK has a mass of 4(5) TeV. The yellow histogram in both panels is the SM background while the blue(red,green) histogram corresponds to the case of $S^2(S^1/Z_2,T^2/Z_2)$. Fermions are assumed to be completely localized at either the North or South Poles. The bin size is 1% of the dilepton invariant mass.

Figure 3

Same as the previous figure but now for the LHC upgrade with an order of magnitude higher integrated luminosity.

Figure 4

Transverse mass distributions for $W_{l0}^{\pm }$ production at the LHC. The lowest, steeply falling histogram is the SM background. The top (lower) triplet of signal histograms is for a lightest $W_{10}^{\pm }$ KK mass of 4 (5) TeV. The upper (middle, lower) member of each pair is for the $T^2/Z_2(S^2,S^1/Z_2)$ model.

Figure 5

Dijet pair mass at the LHC applying the cut $|\eta |\le 1$ and $p_{Tj}\ge 0.4M_{jj}$. The lowest histogram in both panels is the SM QCD background. In the top panel, a $g_{10}$ mass of 4 TeV has been assumed with the upper (middle, lower) signal histogram corresponding, on the right-hand side of the figure, to the $S^2(T^2/Z_2,S^1/Z_2)$ model. In the lower panel the top(middle) three histograms are for the $S^2(S^1/Z_2)$ model assuming, from top to bottom, KK masses of 5, 6 or 7 TeV, respectively. Couplings between the KK states and SM zero-mode gluons have been neglected.