Physics at SuperB

Flavour will play a crucial role in understanding physics beyond the Standard Model. Progress in developing a future programme to investigate this central area of particle physics has recently passed a milestone, with the completion of the conceptual design report for SuperB, a very high luminosity, asymmetric ee collider. This article summarizes the important role of SuperB in understanding new physics in the LHC era. The major challenge facing particle physics in the next decade is to go beyond the Standard Model (SM) of elementary particles. Historically, progress in the field has been achieved through advances on two parallel approaches – the energy frontier and the luminosity frontier. While the LHC will soon deliver the much anticipated leap forwards in available centre-of-mass energy, a comparable advance from the current world record luminosities achieved by the B factories will allow complementary research into new physics (NP).1 This is a simple consequence of the fact that quantum physics allows for the virtual production of heavy particles, which influence processes at energies much below their masses. Therefore, to investigate NP through quantum effects, high precision, rather than high energy, is required. The flavour sector is well-suited to search for quantum effects of NP since flavour changing neutral currents, neutral meson-antimeson mixing and CP violation all occur at the loop level in the SM, with quark flavour violation further suppressed by the small mixing angles, Since there is no a priori reason for NP to share these features, the quark sector is potentially subject to large NP effects. Similar arguments apply in the lepton sector, where the theoretical interest is even greater, since the physics behind neutrino oscillations remains an open question. Many observables in the flavour sector are generically sensitive to NP effects, including rates and asymmetries of rare leptonic or loop-induced K, D and B decays, mixing and CP violating phenomena in the K0, D0, B0 d and B 0 s systems, electric and magnetic dipole moments of charged leptons and lepton flavour violating μ and τ decays. While certain models focus attention onto particular channels, there is no single “golden mode” – rather, the flavour sector can be thought of as a treasure chest of NP-sensitive observables. Indeed, the plethora of measurements that can be made adds significantly to the physics programme, enhancing the sensitivity to NP. Moreover, correlations between observables can distinguish between different NP models. A coherent programme for particle physics research in the next decade should therefore allow as many flavour observables as possible to be studied. No single experimental facility can cover them all. However, a “Super Flavour Factory”, i.e. a high luminosity, asymmetric e+e− collider has a very wide-reaching potential, allowing for comprehensive studies of charm (D0, D+ and 1 The development of high luminosity machines is also clearly beneficial for the health of accelerator-based physics, as discussed in the EPS-ECFA joint session at EPS2007. Table 1. Expected precision of some of the most important measurements that can be performed at SuperB with 75 ab. Numbers quoted as percentages are relative precisions. Values given for rare tau decays are the 90% confidence level upper limits expected in the absence of signal. Measurements marked (†) will be systematics limited; those marked (∗) will be theoretically limited. In many of these cases, there exist data driven methods of reducing the errors. Observable Precision sin(2β) (J/ψK0) 0.005 (†) α (ππ, ρπ, ρρ combined) 1–2 (∗) γ (B → DK, combined) 1–2 |Vub| (inclusive) 2.0% (∗) S(φK0) 0.02 (∗) S(η′K0) 0.01 (∗) S(K0 SK 0 SK 0 S) 0.02 (∗)