Removing gaps in the exclusion of top squark parameter space.

Light stops are a hallmark of the most natural realizations of weak-scale supersymmetry. While stops have been extensively searched for, there remain open gaps around and below the top mass, due to similarities of stop and top signals with current statistics. We propose a new fast-track avenue to improve light stop searches for R-parity-conserving supersymmetry by comparing top cross section measurements to the theoretical prediction. Stop masses below ∼180 GeV can now be ruled out for a light neutralino. The possibility of a stop signal contaminating the top mass measurement is also briefly addressed.

Light nondegenerate squarks at the LHC.

Experimental bounds on squarks of the first two generations assume their masses to be eightfold degenerate and consequently constrain them to be heavier than ∼1.4 TeV when the gluino is lighter than 2.5 TeV. The assumption of squark-mass universality is neither a direct consequence of minimal flavor violation (MFV), which allows for splittings within squark generations, nor a prediction of supersymmetric alignment models, which allow for splittings between generations. We reinterpret a recent CMS multijet plus missing energy search allowing for deviations from U(2) universality and find significantly weakened squark bounds: A 400 GeV second-generation squark singlet is allowed, even with exclusive decays to a massless neutralino, and, in an MFV scenario, the down-type squark singlets can be as light as 600 GeV, provided the up-type singlets are pushed up to 1.8 TeV, for a 1.5 TeV gluino and decoupled doublet squarks.

Odd tracks at hadron colliders.

New physics that exhibits irregular tracks such as kinks, intermittent hits, or decay in flight may easily be missed at hadron colliders. We demonstrate this by studying viable models of light, O(10 GeV), colored particles that decay predominantly inside the tracker. Such particles can be produced at staggering rates, and yet, may not be identified or triggered on at the LHC, unless specifically searched for. In addition, the models we study provide an explanation for the original measurement of the anomalous charged track distribution by CDF. The presence of irregular tracks in these models reconcile that measurement with the subsequent reanalysis and the null results of ATLAS and CMS. Our study clearly illustrates the need for a comprehensive study of irregular tracks at the LHC.

Implications of the dimuon CP asymmetry in B(d,s) decays.

The D0 Collaboration reported a 3.2σ deviation from the standard model (SM) prediction in the like-sign dimuon asymmetry. Assuming that new physics contributes only to B(d,s) mixing, we show that the data can be analyzed without using the theoretical calculation of ΔΓ(s), allowing for robust interpretations. We find that this framework gives a good fit to all measurements, including the recent CDF Collaboration S(ψϕ) result. The data allow universal new physics with similar contributions relative to the SM in the B(d) and B(s) systems, but favors a larger deviation in B(s) than in B(d) mixing. The general minimal flavor violation framework with flavor diagonal CP violating phases can account for the former case and remarkably even for the latter case. This observation makes it simpler to speculate about which extensions with general flavor structure may also fit the data.

Fastlim: a fast LHC limit calculator.

Fastlim is a tool to calculate conservative limits on extensions of the Standard Model from direct LHC searches without performing any Monte Carlo event generation. The program reconstructs the visible cross sections (cross sections after event selection cuts) from pre-calculated efficiency tables and cross section tables for simplified event topologies. As a proof of concept of the approach, we have implemented searches relevant for supersymmetric models with R-parity conservation. Fastlim takes the spectrum and coupling information of a given model point and provides, for each signal region of the implemented analyses, the visible cross sections normalised to the corresponding upper limit, reported by the experiments, as well as the [Formula: see text] value. To demonstrate the utility of the program we study the sensitivity of the recent ATLAS missing energy searches to the parameter space of natural SUSY models. The program structure allows the straightforward inclusion of external efficiency tables and can be generalised to R-parity violating scenarios and non-SUSY models. This paper serves as a self-contained user guide and indicates the conventions and approximations used.

Implications of the measurement of the Bs(0)Bs(0) mass difference.

We analyze the significant new model independent constraints on extensions of the standard model (SM) that follow from the recent measurements of the Bs(0)Bs(0) mass difference. The time-dependent CP asymmetry in Bs-->psiphi, S(psiphi), will be measured with good precision in the first year of CERN Large Hadron Collider (LHC) data taking, which will further constrain the parameter space of many extensions of the SM, in particular, next-to-minimal flavor violation. The CP asymmetry in semileptonic Bs decay, ASL(s), is also important to constrain these frameworks, and could give further clues to our understanding the flavor sector in the LHC era. We point out a strong correlation between S(psiphi) and ASL(s) in a very broad class of new physics models.

Infrared Lorentz violation and slowly instantaneous electricity.

We study a modification of electromagnetism which violates Lorentz invariance at large distances. In this theory, electromagnetic waves are massive, but the static force between charged particles is Coulomb, not Yukawa. At very short distances the theory looks just like QED. But for distances larger than 1/m the massive dispersion relation of the waves can be appreciated, and the Coulomb force can be used to communicate faster than the speed of light. In fact, electrical signals are transmitted instantly, but take a time approximately 1/m to build up to full strength. After that, undamped oscillations of the electric field are set in and continue until they are dispersed by the arrival of the Lorentz-obeying part of the transmission. Experimental constraints imply that the Compton wavelength of the photon may be as small as 6000 km. This bound is weaker than for a Lorentz-invariant mass, essentially because the Coulomb constraint is removed.