Search for physics beyond the standard model in final states with a lepton and missing transverse energy in proton-proton collisions ats=8  TeV

Abstract

A search for new physics in proton-proton collisions having final states with an electron or muon and missing transverse energy is presented. The analysis uses data collected in 2012 with the CMS detector, at an LHC center-of-mass energy of 8 TeV, and corresponding to an integrated luminosity of 19.7 fb −1 . No significant deviation of the transverse mass distribution of the charged lepton-neutrino system from the standard model prediction is found. Mass exclusion limits of up to 3.28 TeV at 95% confidence level for a W 0 -boson with the same couplings as that of the standard model W-boson are determined. Results are also derived in the framework of split universal extra dimensions, and exclusion limits on Kaluza-Klein W ð2Þ KK states are found. The final state with large missing transverse energy also enables a search for dark matter production with a recoiling W-boson, with limits set on the mass and the production cross section of potential candidates. Finally, limits are established for a model including interference between a left-handed W 0 -boson and the standard model W-boson and for a compositeness model.

A call for new physics: The muon anomalous magnetic moment and lepton flavor violation

“…We assume that this new vector boson couples only to left-or RH leptons, however, we remark that in the former case there exist other constraints from collider searches and electroweak precision tests [243,244] which we disregard here. The interaction under consideration reads The term proportional to g L is not relevant for our purposes because in this case it has to be accompanied by some small mixing, which would require very large couplings in order to produce a signal in g − 2 or µ → eγ.…”

Mono-X versus direct searches: simplified models for dark matter at the LHC

“…In most cases, DM production with a jet from the initial state imposes the most stringent constraints. Even so, as dedicated searches for various mono-X channels have already been performed [48][49][50][51][52][53][54] and will be extensively carried on in the current and future LHC runs, it is important and timely to consider a relatively exhaustive set of simplified models that give rise dominantly to such mono-X signals. A systematic study considering…”

Simplified DM models with the full SM gauge symmetry: the case of t-channel colored scalar mediators

“…We introduce 3 types of new scalar bosons, Q Li , u Ri and d Ri with negative Z 2 parity, which are partners of Q Li ≡ (u Li , d Li ) T , u Ri and d Ri respectively. 5 Simplified models with colored scalar mediators that couple to the quarks have been previously studied [24,25,[43][44][45][46][47], however these studies have assumed either just an up-like SU(2) singlet [45], a down-like singlet [44], a doublet [46,48], or a simplified model similar to our proposal however with universal couplings to all generations and universal masses for up-like and down-like scalars [24,49,50]. The gauge invariant interaction Lagrangian between quarks and DM in our model is given by:…”

“…Colliders searches for mono X+ E T signatures (with X = W, g, γ, Z) at the LHC have also used this EFT approach during Run-I [2][3][4][5][6], but have also utilized UV-complete models such as Supersymmetry [7]. However, at the center-of-mass energies at the LHC this EFT approach would break down [8,9], which warrants the use of UV-complete models at the expense of introducing many more free parameters.…”