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Gian F. Giudice
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In this talk I make some remarks about the search for the origin of the electroweak scale.
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Major new experimental efforts on detecting CP violation in $B$ decays will very soon go on the air. Recent developments suggest that final state interaction phases in exclusive decays of $B$ are unlikely to be small indicating the possibility of observable direct CP asymmetries in these channels. CLEO results on charmless hadronic modes suggest penguin amplitudes are rather big implying that the extraction of $alpha$ from $B^0$-$bar B^0$ alone will be difficult, thus necessitating also information from direct CP ull. Importance of $B(B_s)$ decays to two vectors for model independent tests of electroweak penguins and for extraction of $alpha(gamma)$ is emphasized. Inclusive $bto sg^ast$ and related modes, e.g. $Bto eta^prime X_s$, are very good probes of CP-odd phase(s) due to beyond the standard model physics. On the other hand, $bto dg^ast$ and related modes, e.g. $Bto eta^prime X_d$ are more suitable for CP violation due to the CKM phase. Two body $b$-quark decays: $bto Mq_f$ leading to semi-inclusive, $B$ decays, $Bto MX$ (with $2lsim E_Mlsim2.8$ GeV), are very interesting and important. Their theory is relatively clean; partial rate asymmetries may be large in several cases (e.g. $M=K^ast, K, rho, pi...$) and a few cases provide very good probe of electroweak penguins.
Axion-like particles (ALPs) provide a promising direction in the search for new physics, while a wide range of models incorporate ALPs. We point out that future neutrino experiments, such as DUNE, possess competitive sensitivity to ALP signals. The high-intensity proton beam impinging on a target can not only produce copious amounts of neutrinos, but also cascade photons that are created from charged particle showers stopping in the target. Therefore, ALPs interacting with photons can be produced (often energetically) with high intensity via the Primakoff effect and then leave their signatures at the near detector through the inverse Primakoff scattering or decays to a photon pair. Moreover, the high-capability near detectors allow for discrimination between ALP signals and potential backgrounds, improving the signal sensitivity further. We demonstrate that a DUNE-like detector can explore a wide range of parameter space in ALP-photon coupling $g_{agamma}$ vs ALP mass $m_a$, including some regions unconstrained by existing bounds; the cosmological triangle will be fully explored and the sensitivity limits would reach up to $m_asim3-4$ GeV and down to $g_{agamma}sim 10^{-8} {rm GeV}^{-1}$.
I give my perspective on promising directions for high energy physics in coming years.
We investigate the behavior of energy momentum tensor correlators in strongly coupled large-N_c Yang-Mills theory at nonzero temperature, working within the Improved Holographic QCD model. In particular, we determine the spectral functions and corresponding imaginary time correlators in the bulk and shear channels, and compare the results to recent perturbative and lattice calculations where available. For the bulk channel imaginary time correlator, for which all three results exist, lattice data is seen to favor the holographic prediction over the perturbative one over a wide range of temperatures.
We discuss F-theory SU(5) GUTs in which some or all of the quark and lepton families are assigned to different curves and family symmetry enforces a leading order rank one structure of the Yukawa matrices. We consider two possibilities for the suppression of baryon and lepton number violation. The first is based on Flipped SU(5) with gauge group SU(5)times U(1)_chi times SU(4)_{perp} in which U(1)_{chi} plays the role of a generalised matter parity. We present an example which, after imposing a Z_2 monodromy, has a U(1)_{perp}^2 family symmetry. Even in the absence of flux, spontaneous breaking of the family symmetry leads to viable quark, charged lepton and neutrino masses and mixing. The second possibility has an R-parity associated with the symmetry of the underlying compactification manifold and the flux. We construct an example of a model with viable masses and mixing angles based on the gauge group SU(5)times SU(5)_{perp} with a U(1)_{perp}^3 family symmetry after imposing a Z_2 monodromy.
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