Measuring the Higgs Boson Self Coupling at the LHC and Finite Top Mass Matrix Elements

Abstract

Inclusive Standard Model Higgs boson pair production and subsequent decay to same-sign dileptons via weak gauge W bosons at the CERN Large Hadron Collider has the capability to determine the Higgs boson self-coupling, lambda. The large top quark mass limit is found not to be a good approximation for the signal if one wishes to utilize differential distributions in the analysis. We find that it should be possible at the LHC with design luminosity to establish that the Standard Model Higgs boson has a non-zero self-coupling and that lambda/lambda(SM) can be restricted to a range of 0--3.7 at 95% confidence level if its mass is between 150 and 200 GeV.

Figures (4)

• Figure 1: Minimum separation between jets, $\Delta R(jj)_{\rm min}$, for the $M_H = 180\;{\rm GeV}$, signal with exact matrix elements (solid line) and in the large $m_t$ limit (dot-dashed line), and the $WWWjj$ (dashed line) and $t\bar{t}W$ backgrounds (dotted line). Qualitatively similar results are obtained for other values of the Higgs boson mass in the range $150~{\rm GeV}\leq M_H\leq 200$ GeV.
• Figure 2: Distribution of the invariant mass of all observable final state particles, $m_{vis}$, after all cuts, for the signal with a) $M_H=160\;{\rm GeV}$ and b) $M_H=200\;{\rm GeV}$, and the dominant backgrounds. The $m_{vis}$ distribution of the signal evaluated in the large $m_t$ limit is also shown.
• Figure 3: The $m_{vis}$ distribution of the signal for $M_H=180$ GeV in the SM (solid curve), for $\lambda_{HHH}=\lambda/\lambda_{SM}=0$ (dashed line) and for $\lambda_{HHH}=2$ (dotted line). The dot-dashed line shows the SM cross section in the large $m_t$ limit. Qualitatively similar results are obtained for other values of $M_H$.
• Figure 4: Limits achievable at $95\%$ CL for $\Delta\lambda_{HHH}=\lambda_{HHH}-1$ ($\lambda_{HHH}=\lambda/\lambda_{SM}$) in $pp\to\ell^\pm{\ell'}^\pm+4j$ at the LHC. Bounds are shown for integrated luminosities of 300 fb$^{-1}$ (solid lines), 600 fb$^{-1}$ (dashed lines) and 3000 fb$^{-1}$ (dotted lines). The allowed region is between the two lines of equal texture. The Higgs boson self-coupling vanishes for $\Delta\lambda_{HHH}=-1$.