Neutrino Oscillations from Supersymmetry without R-parity - Its Implications on the Flavor Structure of the Theory

We discuss here some flavor structure aspects of the complete theory of supersymmetry without R-parity addressed from the perspective of fitting neutrino oscillation data based on the recent Super-Kamiokande result. The single-VEV parametrization of supersymmetry without R-parity is first reviewed, illustrating some important features not generally appreciated. For the flavor structure discussions, a naive, flavor model independent, analysis is presented, from which a few interesting things can be learned.Comment: 1+10 pages latex, no figure; Invited talk at NANP 99 conference, Dubna (Jun 28 - Jul 3) --- submission for the proceeding

Flavor Changing Scalar Interactions

The smallness of fermion masses and mixing angles has recently been been attributed to approximate global $U(1)$ symmetries, one for each fermion type. The parameters associated with these symmetry breakings are estimated here directly from observed masses and mixing angles. It turns out that although flavor changing reaction rates may be acceptably small in electroweak theories with several scalar doublets without imposing any special symmetries on the scalars themselves, such theories generically yield too much CP violation in the neutral kaon mass matrix. Hence in these theories CP must also be a good approximate symmetry. Such models provide an alternative mechanism for CP violation and have various interesting phenomenological features.Comment: 18 pages. UTTG-22-92; LBL 33016; UCB 92/3

The Anomalous Magnetic Moment of the Muon and Higgs-Mediated Flavor Changing Neutral Currents

In the two-Higgs doublet extension of the standard model, flavor-changing neutral couplings arise naturally. In the lepton sector, the largest such coupling is expected to be $\mu-\tau-\phi#. We consider the effects of this coupling on the anomalous magnetic moment of the muon. The resulting bound on the coupling, unlike previous bounds, is independent of the value of other unknown couplings. It will be significantly improved by the upcoming E821 experiment at Brookhaven National Lab.Comment: 7 pages Latex, 2 figure

Approximate Flavor Symmetries in the Lepton Sector

Approximate flavor symmetries in the quark sector have been used as a handle on physics beyond the Standard Model. Due to the great interest in neutrino masses and mixings and the wealth of existing and proposed neutrino experiments it is important to extend this analysis to the leptonic sector. We show that in the see-saw mechanism, the neutrino masses and mixing angles do not depend on the details of the right-handed neutrino flavor symmetry breaking, and are related by a simple formula. We propose several ans\"{a}tze which relate different flavor symmetry breaking parameters and find that the MSW solution to the solar neutrino problem is always easily fit. Further, the $\nu_\mu - \nu_\tau$ oscillation is unlikely to solve the atmospheric neutrino problem and, if we fix the neutrino mass scale by the MSW solution, the neutrino masses are found to be too small to close the Universe.Comment: 12 pages (no figures), LBL-3459

Protecting the Primordial Baryon Asymmetry From Erasure by Sphalerons

If the baryon asymmetry of the universe was created at the GUT scale, sphalerons together with exotic sources of $(B-L)$-violation could have erased it, unless the latter satisfy stringent bounds. We elaborate on how the small Yukawa coupling of the electron drastically weakens previous estimates of these bounds.Comment: 41 pp., 4 latex figures included and 3 uuencoded or postscript figures available by request, UMN-TH-1213-9

On Preserving a B+L Asymmetry Produced in the Early Universe

One of the most efficient mechanisms for producing the baryon asymmetry of the Universe is the decay of scalar condensates in a SUSY GUT as was first suggested by Affleck and Dine. We show that given a large enough asymmetry, the baryon number will be preserved down to low temperatures even if B - L = 0, because the baryon number carrying scalars form bose condensates that give the W a mass. We derive the conditions on the condensate needed to suppress electroweak sphaleron interactions which would otherwise drive the baryon asymmetry to zero when B - L = 0.Comment: 10 pages, LaTeX, UMN-TH-1240, CfPA-TH-94-13, LBL-3527

Probing flavor changing interactions in hadron collisions

The subprocess $gg \to t\bar{c}+\bar{t}c$ in the two-Higgs-doublet model with flavor-changing scalar couplings is examined at the one loop level. With perturbative QCD factorization theorem, the corresponding cross sections for hadron-hadron collisions are computed numerically. The results are applicable to the whole mass range of the weakly coupled Higgs bosons. In case we could efficiently exclude the severe backgrounds of the $t\bar{c}(\bar{t}c)$ production signal, probing the flavor-changing top-charm-scalar vertex at hadron colliders would be very promising and accessible experimentally.Comment: LaTex file, 14 pages, 8 EPS figure

Flavor at the TeV Scale with Extra Dimensions

Theories where the Standard Model fields reside on a 3-brane, with a low fundamental cut-off and extra dimensions, provide alternative solutions to the gauge hierarchy problem. However, generating flavor at the TeV scale while avoiding flavor-changing difficulties appears prohibitively difficult at first sight. We argue to the contrary that this picture allows us to lower flavor physics close to the TeV scale. Small Yukawa couplings are generated by ``shining'' badly broken flavor symmetries from distant branes, and flavor and CP-violating processes are adequately suppressed by these symmetries. We further show how the extra dimensions avoid four dimensional disasters associated with light fields charged under flavor. We construct elegant and realistic theories of flavor based on the maximal U(3)^5 flavor symmetry which naturally generate the simultaneous hierarchy of masses and mixing angles. Finally, we introduce a new framework for predictive theories of flavor, where our 3-brane is embedded within highly symmetrical configurations of higher-dimensional branes.Comment: 40 pages, 8 figure

h→μτh\to \mu\tau at Hadron Colliders

We study the observability for a lepton flavor-changing decay of a Higgs boson $h\to \mu\tau$ at hadron colliders. Flavor-changing couplings of a Higgs boson exist at tree level in models with multiple Higgs doublets. The $h\mu\tau$ coupling is particularly motivated by the favorable intepretation of $\nu_\mu-\nu_\tau$ oscillation. We find that at the Tevatron Run II the unique $\mu\tau$ signature could serve as the Higgs discovery channel, surpassing expectations for Higgs boson searches in the SM and in a large parameter region of the MSSM. The sensitivity will be greatly improved at the LHC, beyond the coverage at a muon collider Higgs factory.Comment: Version to appear in PR

CP violating polarizations in semileptonic heavy meson decays

We study the $T$-violating lepton transverse polarization ($P^\perp_l$) in three body semileptonic heavy meson decays to pseudoscalar mesons and to vector mesons. We calculate these polarizations in the heavy quark effective limit, which simplifies the expressions considerably. After examining constraints from $CP$ conserving (including $b \rightarrow s \gamma$) and $CP$ violating processes, we find that in $B$ decays, $P^\perp$ of the muon in multi-Higgs doublet models can be of order $10\%$, while $P^\perp$ of the $\tau$ can even approach unity. In contrast, $P^\perp_\mu$ in $D$ decays is at most 1.5\%. We discuss possibilities for detection of $P^\perp_l$ at current and future $B$ factories. We also show that $P^\perp_l$ in decays to vector mesons, unlike in decays to pseudoscalars, can get contributions from left-right models. Unfortunately, $P^\perp_l$ in that case is proportional to $W_L$-$W_R$ mixing, and is thus small.Comment: 32pp plain LATEX, 3 figs (by EMAIL request), TRI-PP-94-1