Precision test of the SM with Kl2 and Kl3 decays at KLOE

Kaon decay studies seeking new-physics (NP) effects in leptonic (K_l2) or semileptonic (K_l3) decays are discussed. A unitarity test of the first row of the CKM mixing matrix is obtained from the KLOE precision measurements of Kl3 widths for K^+-, K_L, and (unique to KLOE) K_S, complemented with the absolute branching ratio for the K_mu2 decay. KLOE results lead to constraints for NP models and can probe possible charged Higgs exchange contribution in SM extensions with two Higgs doublets. The main focus in the present document is set on a new measurement of R_K=Gamma(K_e2)/Gamma(K_mu2) with an accuracy at the % level, aiming at finding evidence of deviations from the SM prediction induced by lepton-flavor violation NP effects.Comment: Contributed to Rencontres de Moriond EW 2009, La Thuile, Italy, 7-14 March 200

The rare decay B --> X_s l^+ l^- to NNLL precision for arbitrary dilepton invariant mass

We present a new phenomenological analysis of the inclusive rare decay $B \to X_s \ell^+\ell^-$. In particular, we present the first calculation of the NNLL contributions due to the leading two-loop matrix elements, evaluated for arbitrary dilepton invariant mass. This allows to obtain the first NNLL estimates of the dilepton mass spectrum and the lepton forward-backward asymmetry in the high $M^2_{\ell^+ \ell^-}$ region, and to provide an independent check of previously published results in the low $M^2_{\ell^+ \ell^-}$ region. The numerical impact of these NNLL corrections in the high-mass region ($M^2_{\ell^+ \ell^-} > 14.4 GeV^2$) amounts to -13% in the integrated rate, and leads to a reduction of the scale uncertainty to $\pm 3$. The impact of non-perturbative contributions in this region is also discussed in detail.Comment: 40 pages, 12 figures. v2: extended phenomenological discussion; results unchanged; published versio

Higgs-Mediated tau -> 3 mu in the Supersymmetric Seesaw Model

Recent observations of neutrino oscillations imply non-zero neutrino masses and flavor violation in the lepton sector, most economically explained by the seesaw mechanism. Within the context of supersymmetry, lepton flavor violation (LFV) among the neutrinos can be communicated by renormalization group flow to the sleptons and from there to the charged leptons. We show that LFV can appear in the couplings of the neutral Higgs bosons, an effect that is strongly enhanced at large tan(beta). In particular, we calculate the branching fraction for tau -> 3 mu and mu -> 3 e mediated by Higgs and find that they can be as large as 10^{-7} and 5x10^{-14} respectively. These modes, along with B^0 -> mu mu, can provide important evidence for supersymmetry before direct discovery of supersymmetric partners occurs. Along with tau -> mu gamma and mu -> e gamma, they can also provide key insights into the form of the neutrino Yukawa mass matrix.Comment: 9 pages LaTeX, 2 figures. Added a discussion of mu -> 3e and its ramifications for probing neutrino mass matrix. Also added references, fixed typos, and made one notational chang

New NNLL Results on the Decay B --> X(s) L+ L-

We present here new NNLL predictions on the inclusive rare decay B --> X(S) L+ L- based on our new two-loop QCD analysis of the four-quark operators.Comment: typo in (1) fixed, input parameters slightly change

Kaon physics with a high-intensity proton driver

We study opportunities for future high-precision experiments in kaon physics using a high-intensity proton driver, which could be part of the front-end of a muon storage ring complex. We discuss in particular the rare decays $K_L\to\pi^0\nu\bar\nu$, $K^+\to\pi^+\nu\bar\nu$, $K_L\to\pi^0e^+e^-$, and lepton-flavour violating modes such as $K_L\to\mu e$ and $K\to\pi\mu e$. The outstanding physics potential and long-term interest of these modes is emphasized. We review status and prospects of current and planned experiments for the processes under consideration, and indicate possible improvements and strategies towards achieving the necessary higher sensitivity. Finally, we outline the machine requirements needed to perform these high-precision kaon experiments in the context of a muon storage ring facility.Comment: 26 pages, 12 figures; report of the kaon physics working group for the ECFA studies on neutrino factory and muon storage rings at CERN, G. Buchalla (convener); references update

Physics Opportunities with the FCC-hh Injectors

In this chapter we explore a few examples of physics opportunities using the existing chain of accelerators at CERN, including potential upgrades. In this context the LHC ring is also considered as a part of the injector system. The objective is to find examples that constitute sensitive probes of New Physics that ideally cannot be done elsewhere or can be done significantly better at theCERN accelerator complex. Some of these physics opportunities may require a more flexible injector complex with additional functionality than that just needed to inject protons into the FCC-hh at the right energy, intensity and bunch structure. Therefore it is timely to discuss these options concurrently with the conceptual design of the FCC-hh injector system.Comment: 13 pages, chapter 5 in Physics at the FCC-hh, a 100 TeV pp collide

Strong rescattering in K-> 3pi decays and low-energy meson dynamics

We present a consistent analysis of final state interactions in ${K\rightarrow 3\pi}$ decays in the framework of Chiral Perturbation Theory. The result is that the kinematical dependence of the rescattering phases cannot be neglected. The possibility of extracting the phase shifts from future $K_S-K_L$ interference experiments is also analyzed.Comment: 14 pages in RevTex, 3 figures in postscrip

On B_s -> mu+ mu- and Cold Dark Matter Scattering in the MSSM with Non-Universal Higgs Masses

We show that present experimental constraints on B_s -> mu+ mu- decay and the CDMS upper limit on the cold dark matter elastic scattering cross section already have significant impact on the parameter space of the minimal supersymmetric extension of the Standard Model (MSSM) with non-universal supersymmetry-breaking scalar masses for the Higgs multiplets (NUHM). The relaxation of scalar universality in the MSSM allows the possibility of a relatively light mass M_A for the pseudoscalar Higgs boson. The present upper limit on B_s -> mu+ mu- already excludes much of the scope for this possibility in the NUHM, in contrast to the constrained MSSM with universal scalar masses (CMSSM), where B_s -> mu+ mu- decay does not exclude any ranges of parameters not already excluded by b -> s \gamma decay. Cold dark matter scattering is also enhanced for small M_A, but the impact of present upper limit on B_s -> mu+ mu- on the NUHM parameter space is in many cases greater than that of the CDMS scattering limit, particularly at large tanb.Comment: 17 pages, 14 eps figure

Higgs-Mediated tau --> mu and tau --> e transitions in II Higgs doublet Model and Supersymmetry

We study the phenomenology of the mu-tau and e-tau lepton flavour violation (LFV) in a general two Higgs Doublet Model (2HDM) including the supersymmetric case. We consider several LFV decay modes of the charged fermion tau, namely tau-> l_jgamma, tau->l_j l_k l_k and tau-> l_jeta. The predictions and the correlations among the rates of the above processes are computed. In particular, it is shown that tau->l_jgamma processes are the most sensitive channels to Higgs-mediated LFV specially if the splitting among the neutral Higgs bosons masses is not below the 10% level.Comment: v2=published version: 13 pages, 4 figures, text improved and reference added. Two loop effects (relevant for tau->l_jgamma) added. Conclusions unchange

Implications on SUSY breaking mediation mechanisms from observing Bs→μ+μ−B_s \to \mu^+ \mu^- and the muon (g−2)(g-2)

We consider $B_s \to \mu^+ \mu^-$ and the muon $(g-2)_\mu$ in various SUSY breaking mediation mechanisms. If the decay $B_s \to \mu^+ \mu^-$ is observed at Tevatron Run II with a branching ratio larger than $\sim 2 \times 10^{-8}$, the noscale supergravity (including the gaugino mediation), the gauge mediation scenario with small number of messenger fields and low messenger scale, and a class of anomaly mediation scenarios will be excluded, even if they can accommodate a large muon $(g-2)_\mu$. On the other hand, the minimal supergravity scenario and similar mechanisms derived from string models can accommodate this observation.Comment: 4 pages, 3 figure