Search

A conventional approach to precision calculations of Higgs boson observables uses quark masses mc and mb as inputs. However, quark masses are single numbers that hide a variety of low-energy data from which they are extracted, and also hide the various sources of theoretical uncertainties and correlations with additional input parameters such as αs. Higher-precision calculations, which are needed to give meaning to future measurements, require more direct engagement with the low-energy data in a global analysis. We present an initial calculation in this direction, which illustrates the procedure and reveals some of the theory uncertainties that challenge subpercent determinations of Higgs boson partial widths. [ABSTRACT FROM AUTHOR]

We show that gauge coupling unification in supersymmetry (SUSY) models can make a nontrivial interconnection between collider and proton decay experiments. Under the assumption of precise gauge coupling unification in the Minimal Supersymmeric Standard Model, with negligible grand unified theories threshold corrections, the low energy SUSY spectrum and the unification scale are intertwined, and the lower bound on the proton lifetime can be translated into upper bounds on SUSY masses. We find that the current limit on τ(P→p0e+) already excludes gluinos heavier than ~70 (120 and 200) TeV if their mass ratio to winos, R=M3/M2, is ~1 (3 and 7), respectively. Next generation nucleon decay experiments are expected to bring these upper bounds down to ~5 (10 and 15) TeV for R~1 (3 and 7). [ABSTRACT FROM AUTHOR]

The discovery of the Higgs boson, with mass known to better than the percent level, enables for the first time precision Higgs boson analyses. Toward this goal, we define an expansion formalism of the Higgs boson partial widths and branching fractions that facilitates such studies. This expansion yields the observables as a perturbative expansion around reference values of Standard Model input observables (quark masses, QCD coupling constant, etc.). We compute the coefficients of the expansion using state-of-the-art results. We also study the various sources of uncertainties in computing the partial widths and branching fractions more precisely. We discuss the impact of these results with efforts to discern new physics through precision Higgs boson studies. [ABSTRACT FROM AUTHOR]

There are strong similarities between charge-parity (CP) violating observables in hadronic B decays (in particular Δ A - C P in B → K π) and direct CP violation in kaon decays (ε′): All these observables are very sensitive to new physics (NP) which is at the same time CP and isospin violating (i.e., NP with complex couplings which are different for up quarks and down quarks). Intriguingly, both the measurements of ε′ and ΔACP show deviations from their Standard Model predictions, calling for a common explanation (the latter is known as the B → K π puzzle). For addressing this point, we parametrize NP using a gauge invariant effective field theory approach combined with a global U (2)³ flavor symmetry in the quark sector (also known as less-minimal flavor violation). We first determine the operators which can provide a common explanation of ε′ and Δ A - C P and then perform a global fit of their Wilson coefficients to the data from hadronic B decays. Here we also include e.g., the recently measured CP asymmetry in Bs → K K as well as the purely isospin violating decay B s → ϕρ0, finding a consistent NP pattern providing a very good fit to data. Furthermore, we can at the same time explain ε ′ / ε for natural values of the free parameters within our U(2)³ flavor approach, and this symmetry gives interesting predictions for hadronic decays involving b → d transitions. [ABSTRACT FROM AUTHOR]

LHCb has reported deviations from the Standard Model in b → τ±μ+μ- transitions for which a new neutral gauge boson is a prime candidate for an explanation. As this gauge boson has to couple in a flavor nonuniversal way to muons and electrons in order to explain RK, it is interesting to examine the possibility that also lepton flavor is violated, especially in the light of the CMS excess in h →τ±μ≠. In this article, we investigate the perspectives to discover the lepton-flavor violating modes B → K(*)τ±μ≠, Bs → τ±μ≠ and B → K(*)μ±e≠, Bs→ μ±e≠. For this purpose we consider a simplified model in which new-physics effects originate from an additional neutral gauge boson (Z') with generic couplings to quarks and leptons. The constraints from τ → 3μ, → μν..., μ → eγ, gμ 2, semileptonic b → sμ+μ- decays, B → K(*)ν... and Bs-...s mixing are examined. From these decays, we determine upper bounds on the decay rates of lepton-flavor violating B decays. Br (B → Kν...) limits the branching ratios of lepton-flavor violating B decays to be smaller than 8 x 10-5 (2 x 10-5) for vectorial (left-handed) lepton couplings. However, much stronger bounds can be obtained by a combined analysis of Bs-...s, τ → 3μ, τ → μν... → μν... and other rare decays. The bounds depend on the amount of fine-tuning among the contributions to Bs-...s mixing. Allowing for a fine-tuning at the percent level we find upper bounds of the order of 10-6 for branching ratios into τμ final states, while Bs → μ±e≠ is strongly suppressed and only B → K(*)μ±e≠ can be experimentally accessible (with a branching ratio of order 10-7). [ABSTRACT FROM AUTHOR]

We present a systematic study of the different mechanisms leading to WW pair production at the Large Hadron Collider (LHC), both in the same-sign and opposite-sign channels, and we emphasize that the former offers much better potential for investigating non-resonant WLWL scattering. We propose a new kinematic variable to isolate the WLWL scattering component in same-sign WW production at the LHC. Focusing on purely leptonic W decay channels, we show that it considerably improves the LHC capabilities to shed light on the electroweak symmetry breaking mechanism after collecting 100 fb-1 of data at √ = 14 TeV. The new variable is less effective in the opposite-sign WW channel due to different background composition. [ABSTRACT FROM AUTHOR]