K→πννˉK\to\pi\nu\bar\nu and ϵ′/ϵ\epsilon'/\epsilon in Simplified New Physics Models

The decays $K^+\to\pi^+\nu\bar\nu$ and $K_L\to\pi^0\nu\bar\nu$, being the theoretically cleanest rare decays of mesons, are very sensitive probes of New Physics. In view of the excellent prospects of reaching the Standard Model sensitivity for $K^+\to\pi^+\nu\bar\nu$ by the NA62 experiment at CERN and for $K_L\to\pi^0\nu\bar\nu$ by the KOTO experiment at J-PARC, we study them in the simplest extensions of the SM in which stringent correlations between these two decays and other flavour observables are present. We first consider simple models with tree-level Z and Z' contributions in which either MFV or a $U(2)^3$ symmetry is imposed on the quark flavour-violating couplings. We then compare the resulting correlations with those present in generic models in which the latter couplings are arbitrary, subject to constraints from $\Delta F=2$ processes, electroweak and collider data. Of particular interest are the correlations with $\epsilon'/\epsilon$ and $K_L\to\mu^+\mu^-$ which limit the size of NP contributions to $K^+\to\pi^+\nu\bar\nu$ and $K_L\to\pi^0\nu\bar\nu$, depending on the Dirac structure of couplings and the relevant operators. But in MFV also the constraint from $B_s\to\mu^+\mu^-$ turns out to be important. We take into account the recent results from lattice QCD and large N approach that indicate $\epsilon'/\epsilon$ in the SM to be significantly below the data. While in many models the enhancement of $\epsilon'/\epsilon$ implies a suppression of $K_L\to\pi^0\nu\bar\nu$, we present two models in which these observables can be simultaneously enhanced relative to SM predictions. A correlation between $K^+\to\pi^+\nu\bar\nu$ and $B\to K(K^*)\mu^+\mu^-$, found by us in the simple models considered here, should be of interest for NA62 and LHCb experimentalists at CERN in the coming years. The one with $B\to K(K^*)\nu\bar\nu$ will be tested at Belle II.Comment: 32 pages, 6 figures, 1 table. v2: updated analysis in section 4, matches version published in JHE

Strategies for Fixing the CKM-angle γ\gamma and Obtaining Experimental Insights into the World of Electroweak Penguins

Using the $SU(3)$ flavour symmetry of strong interactions, we propose strategies for extracting both the CKM-angle $\gamma$ and the $\bar b\to\bar uu\bar s$ tree-level amplitude $T'$. We present also an approximate approach using the branching ratios for the modes $B^+\to\pi^+ K^0$, $B^0_d\to\pi^- K^+$, $\bar B^0_d\to\pi^+ K^-$ and $B^+\to\pi^+\pi^0$ which should be rather promising from the experimental point of view. The quantities $\gamma$ and $T'$ determined this way may well be used as an input to control electroweak penguins in nonleptonic $B$-decays as has been discussed in previous work. Following these lines, we propose strategies for obtaining quantitative insights into the physics of the electroweak penguin operators and performing some consistency checks. As a by-product, we derive an upper bound of $6^\circ$ for the uncertainty originating from electroweak penguins in the $\alpha$-determination by means of $B\to\pi\pi$ decays.Comment: 15 pages, LaTeX, Figures not include

Towards the Control over Electroweak Penguins in Nonleptonic B-Decays

We present strategies for determining electroweak penguins from experimental data. Using the CKM-angle $\gamma$ as one of our central inputs and making some reasonable approximations, we show that the $\bar b\to\bar s$ electroweak penguin amplitude can be determined in a two-step procedure involving i) BR$(B^+\to\pi^0K^+)$, BR$(B^-\to\pi^0K^-)$, BR$(B^+\to\pi^+K^0)$ and ii) either BR$(B^0_d\to\pi^-K^+)$, BR$(\bar B^0_d\to\pi^+K^-)$ or \acp(t) of the mode $B_s\to K^+K^-$. The determination employing the $B\to\pi K$ transitions is not affected by $SU(3)$-breaking effects. Relating the $\bar b\to\bar s$ electroweak penguin amplitude to the $\bar b\to\bar d$ case through $SU(3)$ symmetry arguments, we are in a position to estimate the electroweak penguin uncertainty affecting the extraction of the CKM-angle $\alpha$ by using isospin relations among $B\to\pi\pi$ decays. Our results allow in principle the determination of CKM-phases in a variety of $B$-decays.Comment: 14 pages, LaTeX, Figures not include

Exploring CP Violation through B Decays

The B-meson system provides many strategies to perform stringent tests of the Standard-Model description of CP violation. In this brief review, we discuss implications of the currently available B-factory data on the angles alpha, beta and gamma of the unitarity triangle, emphasize the importance of Bs studies at hadronic B experiments, and discuss new, theoretically clean strategies to determine gamma.Comment: 22 pages, 4 figures, invited brief review for Modern Physics Letters

Influence of aerosols, clouds, and sunglint on polarization spectra of Earthshine

Ground-based observations of the Earthshine, i.e., the light scattered by Earth to the Moon, and then reflected back to Earth, simulate space observations of our planet and represent a powerful benchmark for the studies of Earth-like planets. Earthshine spectra are strongly linearly polarized, owing to scattering by molecules and small particles in the atmosphere of the Earth and surface reflection, and may allow us to measure global atmospheric and surface properties of planet Earth. Aims. We aim to interpret already published spectropolarimetric observations of the Earthshine by comparing them with new radiative transfer model simulations including a fully realistic three-dimensional (3D) surface-atmosphere model for planet Earth. We used the highly advanced Monte Carlo radiative transfer model MYSTIC to simulate polarized radiative transfer in the atmosphere of the Earth without approximations regarding the geometry, taking into account the polarization from surface reflection and multiple scattering by molecules, aerosol particles, cloud droplets, and ice crystals. We have shown that Earth spectropolarimetry is highly sensitive to all these input parameters, and we have presented simulations of a fully realistic Earth atmosphere-surface model including 3D cloud fields and two-dimensional (2D) surface property maps. Our modeling results show that scattering in high ice water clouds and reflection from the ocean surface are crucial to explain the continuum polarization at longer wavelengths as has been reported in Earthshine observations taken at the Very Large Telescope in 2011 (3.8 % and 6.6 % at 800 nm, depending on which part of Earth was visible from the Moon at the time of the observations). We found that the relatively high degree of polarization of 6.6 % can be attributed to light reflected by the ocean surface in the sunglint region

B -> pi pi, New Physics in B -> pi K and Implications for Rare K and B Decays

The measured B -> pi pi, pi K branching ratios exhibit puzzling patterns. We point out that the B -> pi pi hierarchy can be nicely accommodated in the Standard Model (SM) through non-factorizable hadronic interference effects, whereas the B -> pi K system may indicate new physics (NP) in the electroweak (EW) penguin sector. Using the B -> pi pi data and the SU(3) flavour symmetry, we may fix the hadronic B -> pi K parameters, which allows us to show that any currently observed feature of the B -> pi K system can be easily explained through enhanced EW penguins with a large CP-violating NP phase. Restricting ourselves to a specific scenario, where NP enters only through Z^0 penguins, we derive links to rare K and B decays, where an enhancement of the K_L-> pi^0 nu nu_bar rate by one order of magnitude, with BR(K_L -> pi^0 nu nu_bar) > BR(K^+ -> pi^+ nu nu_bar), BR(K_L -> pi^0 e^+ e^-)=O(10^{-10}), (\sin2\beta)_{pi nu nu_bar} K* mu^+ mu^-, are the most spectacular effects. We address also other rare K and B decays, epsilon'/epsilon and B_d -> phi K_S.Comment: 6 pages, LaTeX, reference added and a few typos correced, to appear in Physical Review Letter

Can we reach the Zeptouniverse with rare K and B_{s,d} decays?

The Large Hadron Collider will directly probe distance scales as short as 10^{-19}m, corresponding to energy scales at the level of a few TeV. In order to reach even higher resolutions before the advent of future high-energy colliders, it is necessary to consider indirect probes of New Physics (NP), a prime example being Delta F=2 neutral meson mixing processes, which are sensitive to much shorter distance scales. However Delta F=2 processes alone cannot tell us much about the structure of NP beyond the LHC scales. To identify for instance the presence of new quark flavour-changing dynamics of a left-handed (LH) or right-handed (RH) nature, complementary results from Delta F=1 rare decay processes are vital. We therefore address the important question of whether NP could be seen up to energy scales as high as 200 TeV, corresponding to distances as small as 10^{-21}m -- the Zeptouniverse -- in rare K and B_{s,d} decays, subject to present Delta F=2 constraints and perturbativity. We focus in particular on a heavy Z' gauge boson. If restricted to purely LH or RH Z' couplings to quarks, we find that rare K decays, in particular KL-> pi^0 nu nubar and K^+->pi^+ nu nubar, allow us to probe the Zeptouniverse. On the other hand rare B_s and B_d decays, which receive stronger Delta F=2 constraints, allow us to reach about 15 TeV. Allowing for both LH and RH couplings a loosening of the Delta F=2 constraints is possible, and we find that the maximal values of M_Z' at which NP effects that are consistent with perturbative couplings could be found are approximately 2000 TeV for K decays and 160 TeV for rare B_{s,d} decays. Finally we present a simple idea for an indirect determination of M_Z' that could be realised at the next linear e^+e^- or mu^+ mu^- collider and with future precise flavour data.Comment: 43 pages, 10 figures, 6 tables; new section on the role of heavy neutral scalars in reaching Zeptouniverse added; clarifying comments and references adde