We present a collection of signatures for physics beyond the standard model that need to be explored at the LHC. The signatures are organized according to the experimental objects that appear in the final state, and in particular the number of high pT leptons. Our report, which includes brief experimental and theoretical reviews as well as original results, summarizes the activities of the "New Physics'' working group for the "Physics at TeV Colliders" workshop (Les Houches, France, 11-29 June, 2007).

Report of the Higgs working group for the Workshop `Physics at TeV Colliders', Les Houches, France, 21 May - 1 June 2001. It contains 7 separate sections: A. Theoretical Developments B. Higgs Searches at the Tevatron C. Experimental Observation of an invisible Higgs Boson at LHC D. Search for the Standard Model Higgs Boson using Vector Boson Fusion at the LHC E. Study of the MSSM channel $A/H \to \tau \tau$ at the LHC F. Searching for Higgs Bosons in $t\bar t H$ Production G. Studies of Charged Higgs Boson Signals for the Tevatron and the LHC

Abstract: The ratio of branching ratios of the W boson to muons and electrons, $$R_W^{\mu /e}=\mathcal{B}(W\to \mu u)$$ R W μ / e = B ( W → μ ν ) /$$\mathcal{B}(W\to eu)$$ B ( W → e ν ) , has been measured using $$140{\text{ fb}}^{-1}$$ 140 fb - 1 of pp collision data at $$\sqrt{s}=13$$ s = 13  $$\text{T}\text{e}\text{V}$$ Te V collected with the ATLAS detector at the LHC, probing the universality of lepton couplings. The ratio is obtained from measurements of the $$t\overline{t}$$ t t ¯ production cross-section in the ee, $$e\mu$$ e μ and $$\mu \mu$$ μ μ dilepton final states. To reduce systematic uncertainties, it is normalised by the square root of the corresponding ratio $$R_Z^{\mu \mu /ee}$$ R Z μ μ / e e for the Z boson measured in inclusive $$Z\to ee$$ Z → e e and $$Z\to \mu \mu$$ Z → μ μ events. By using the precise value of $$R_Z^{\mu \mu /ee}$$ R Z μ μ / e e determined from $$e^{+}{e}^{-}$$ e + e - colliders, the ratio $$R_W^{\mu /e}$$ R W μ / e is determined to be $$\begin{array}{rl}{R}_W^{\mu /e}& =0.9995\pm 0.0022(\mathrm{stat})\pm 0.0036(\mathrm{syst})\\ & \pm 0.0014(\mathrm{ext}).\end{array}$$ R W μ / e = 0.9995 ± 0.0022 ( stat ) ± 0.0036 ( syst ) ± 0.0014 ( ext ) . The three uncertainties correspond to data statistics, experimental systematics and the external measurement of $$R_Z^{\mu \mu /ee}$$ R Z μ μ / e e , giving a total uncertainty of 0.0045, and confirming the Standard Model assumption of lepton flavour universality in W-boson decays at the 0.5% level.

A search is performed for resonant and non-resonant Higgs boson pair production in the γ γ bb¯ final state. The data set used corresponds to an integrated luminosity of 36.1 fb−1 of proton-proton collisions at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. No significant excess relative to the Standard Model expectation is observed. The observed limit on the non-resonant Higgs boson pair cross-section is 0.73 pb at 95% confidence level. This observed limit is equivalent to 22 times the predicted Standard Model cross-section. The Higgs boson self-coupling (κλ = λHHH/λHHHSM) is constrained at 95% confidence level to −8.2 < κλ < 13.2. For resonant Higgs boson pair production through X→ HH→ γ γ bb¯ , the limit is presented, using the narrow-width approximation, as a function of mX in the range 260 GeV < mX < 1000 GeV. The observed limits range from 1.1 pb to 0.12 pb over this mass range.