Just a Taste: Lectures on Flavor Physics

We review the flavor structure of the Standard Model and the ways in which the flavor parameters are measured. This is an extended writeup of the TASI 2016 lectures on flavor physics. Earlier versions of these lectures were presented at pre-SUSY 2015 and Cornell University's Physics 7661 course in 2010.Comment: 138 pages, includes problems and solutions. To be published in the proceedings of TASI 201

One-Loop MSSM predictions for Bs,d→ℓ+ℓ−B_{s,d} \rightarrow \ell^+\ell^- at low tan β\beta

One of the most promising signals of new physics at colliders is the rare decay B(^0_s) â μ+μ(^-).The LHC will be the first experiment to directly probe this loop- and helicity- suppressed decay channel down to the Standard Model prediction. Deviations from the predicted branching ratio are a signature of new particles in the loops. In particular, it is well known that the MSSM prediction scales as tan(^6) β due to the supersymmetric Higgs penguin diagrams, making this a fertile testing ground for SUSY. In this study we analyse the MSSM prediction for the general B(_s,d) â â+â in the hertofore unexplored low tan beta region of the MSSM parameter space where interference with the box and Z-penguin diagrams could cause the branching ratio to dip below the Standard Model prediction. This decay is particularly important since it could be the first unambigious signal of new physics at the LHC and also guide the future LHCb upgrade

Exotic spin-dependent forces from a hidden sector

New dynamics from hidden sectors may manifest as long-range forces between visible matter particles. The well-known case of Yukawa-like potentials occurs via the exchange of a single virtual particle. However, more exotic behavior is also possible. We present three classes of exotic potentials that are generated by relativistic theories: (i) quantum forces from the loop-level exchange of two virtual particles, (ii) conformal forces from a conformal sector, and (iii) emergent forces from degrees of freedom that only exist in the infrared regime of the theory. We discuss the complementarity of spin-dependent force searches in an effective field theory framework. We identify well-motivated directions to search for exotic spin-dependent forces

Neutron stars at the dark matter direct detection frontier

Neutron stars capture dark matter efficiently. The kinetic energy transferred during capture heats old neutron stars in the local galactic halo to temperatures detectable by upcoming infrared telescopes. We derive the sensitivity of this probe in the framework of effective operators. For dark matter heavier than a GeV, we find that neutron star heating can set limits on the effective operator cutoff that are orders of magnitude stronger than possible from terrestrial direct detection experiments in the case of spin-dependent and velocity-suppressed scattering.Comment: 6 pages, 3 figure

Dark Photons from the Center of the Earth: Smoking-Gun Signals of Dark Matter

Dark matter may be charged under dark electromagnetism with a dark photon that kinetically mixes with the Standard Model photon. In this framework, dark matter will collect at the center of the Earth and annihilate into dark photons, which may reach the surface of the Earth and decay into observable particles. We determine the resulting signal rates, including Sommerfeld enhancements, which play an important role in bringing the Earth's dark matter population to their maximal, equilibrium value. For dark matter masses $m_X \sim$ 100 GeV - 10 TeV, dark photon masses $m_{A'} \sim$ MeV - GeV, and kinetic mixing parameters $\varepsilon \sim 10^{-10} - 10^{-8}$, the resulting electrons, muons, photons, and hadrons that point back to the center of the Earth are a smoking-gun signal of dark matter that may be detected by a variety of experiments, including neutrino telescopes, such as IceCube, and space-based cosmic ray detectors, such as Fermi-LAT and AMS. We determine the signal rates and characteristics, and show that large and striking signals---such as parallel muon tracks---are possible in regions of the $(m_{A'}, \varepsilon)$ plane that are not probed by direct detection, accelerator experiments, or astrophysical observations.Comment: 26 pages, 10 figures. v2: minor revisions to match published version; v3: updated direct detection and CMB constraints and corrected decay length in code, moving the region of experimental sensitivity to values of epsilon that are lower by an order of magnitud

The Same-Sign Dilepton Signature of RPV/MFV SUSY

The lack of observation of superpartners at the Large Hadron Collider so far has led to a renewed interest in supersymmetric models with R-parity violation (RPV). In particular, imposing the Minimal Flavor Violation (MFV) hypothesis on a general RPV model leads to a realistic and predictive framework. Naturalness suggests that stops and gluinos should appear at or below the TeV mass scale. We consider a simplified model with these two particles and MFV couplings. The model predicts a significant rate of events with same-sign dileptons and b-jets. We re-analyze a recent CMS search in this channel and show that the current lower bound on the gluino mass is about 800 GeV at 95% confidence level, with only a weak dependence on the stop mass as long as the gluino can decay to an on-shell top-stop pair. We also discuss how this search can be further optimized for the RPV/MFV scenario, using the fact that MFV stop decays often result in jets with large invariant mass. With the proposed improvements, we estimate that gluino masses of up to about 1.4 TeV can be probed at the 14 TeV LHC with a 100 fb^-1 data set.Comment: 18 pages, 6 figures; v2: References adde

Kaluza-Klein gluons at 100 TeV: NLO corrections

We explore the reach of a 100 TeV proton collider to discover KK gluons in a warped extra dimension. These particles are templates for color adjoint vectors that couple dominantly to the top quark. We examine their production rate at NLO in the six-flavor m-ACOT scheme for a variety of reference models defining their coupling to quarks, largely inspired by the RS model of a warped extra dimension. In agreement with previous calculations aimed at lower energy machines, we find that the NLO corrections are typically negative, resulting in a $K$-factor of around 0.7 (depending on the model) and with a residual scale dependence on the order of $\pm 20\%$, greater than the variation from the scale exhibited by the na\"{i}ve LO estimate.Comment: 33 pages, 5 figures, 2 table