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Andreas Weiler

Publications and source records attributed to Andreas Weiler.

59 records · Page 4Linked to original sources
arXiv2005

Upper Bounds on Rare K and B Decays from Minimal Flavour Violation

We study the branching ratios of rare K and B decays in models with minimal flavour violation, using the presently available information from the universal unitarity triangle analysis and from the measurements of Br(B -> X_s gamma), Br(B -> X_s l^+l^-) and Br(K^+ -> pi^+ nu nubar). We find the following upper bounds: Br(K^+ -> pi^+ nu nubar)< 11.9 10^{-11}, Br(K_L -> pi^0 nu nubar)< 4.6 10^{-11}, Br(K_L -> mu mubar)_{SD}< 1.4 10^{-9}, Br(B -> X_s nu nubar)< 5.2 10^{-5}, Br(B -> X_d nu nubar)< 2.2 10^{-6}, Br(B_s -> mu mubar)< 7.4 10^{-9}, Br(B_d -> mu mubar)< 2.2 10^{-10} at 95 % probability. We analyze in detail various possible scenarios with positive or negative interference of Standard Model and New Physics contributions, and show how an improvement of experimental data corresponding to the projected 2010 B factory integrated luminosities will allow to disentangle and test these different possibilities. Finally, anticipating that subsequently the leading role in constraining this kind of new physics will be taken over by the rare decays K^+ -> pi^+ nu nubar, K_L -> pi^0 nu nubar and B_{s,d} -> mu mubar, that are dominated by the Z^0 -penguin function C, we also present plots for several branching ratios as functions of C . We point out an interesting triple correlation between K^+ -> pi^+ nu nubar, B -> X_s gamma and B -> X_s l^+l^- present in MFV models.

hep-ph↗
arXiv2004

Wilson Lines in Warped Space: Dynamical Symmetry Breaking and Restoration

The dynamics of Wilson lines integrated along a warped extra dimension has been unknown. We study a five dimensional SU(N) pure gauge theory with Randall-Sundrum warped compactification on S^1/Z_2. We clarify the notion of large gauge transformations that are non-periodic on the covering space for this setup. We obtain Kaluza-Klein expansions of gauge and ghost fields for the most general twists and background gauge field configurations, which break the gauge symmetry at classical level in general. We calculate the one-loop effective potential and find that the symmetry corresponding to the subgroup allowing continuous Wilson lines is dynamically restored. The presented method can be directly applied to include extra fields. The connection to dynamical Scherk-Schwarz supersymmetry breaking in warped space is discussed.

hep-ph↗
arXiv2003

The Impact of Universal Extra Dimensions on B -> X_s gamma, B -> X_s gluon, B -> X_s mu^+ mu^-, K_L -> pi^0 e^ +e^-, and epsilon'/epsilon

We calculate the contributions of the Kaluza-Klein (KK) modes to the gamma-penguins, gluon-penguins, gamma-magnetic penguins and chromomagnetic penguins in the Appelquist, Cheng and Dobrescu (ACD) model with one universal extra dimension. Together with our previous calculation of Z^0 penguin diagrams (See http://arxiv.org/abs/hep-ph/0212143) this allows to study the impact of the KK modes on the decays B -> X_s gamma, B -> X_s gluon, B -> X_s mu^+ mu^- and K_L -> pi^0 e^+ e^- and on the CP-violating ratio epsilon'/epsilon. For the compactification scale 1/R= 300 GeV the perturbative part of the branching ratio for B -> X_s mu^+ mu^- is enhanced by 12 % while the zero in the A_FB asymmetry is shifted from \hat s_0=0.162 to \hat s_0=0.142. The sizable suppressions of Br(B -> X_s gamma) ~ 20 % and Br(B -> X_s gluon) ~ 40 % could have interesting phenomenological implications on the lower bound on 1/R provided the experimental and theoretical uncertainties will be decreased. Similar comments apply to epsilon'/epsilon that is suppressed relative to the Standard Model expectations with the size of the suppression depending sensitively on the hadronic matrix elements. The impact on K_L -> pi^0 e^+ e^- is below 10 %. We point out a correlation between the zero \hat s_0 in the A_FB asymmetry and Br(B -> X_s gamma) that should be valid in most models with minimal flavour violation.

hep-ph↗
arXiv2003

The Impact of Universal Extra Dimensions on the Unitarity Triangle and Rare K and B Decays

We calculate the contributions of the Kaluza-Klein (KK) modes to the K_L-K_S mass difference ΔM_K, the parameter ε_K, the B^0_{d,s}-\bar B^0_{d,s} mixing mass differences ΔM_{d,s} and rare decays K^+\to π^+ν\barν, K_L\to π^0ν\barν, K_L\toμ\barμ, B\to X_{s,d}ν\barνand B_{s,d}\toμ\barμin the Appelquist, Cheng and Dobrescu (ACD) model with one universal extra dimension. For the compactification scale 1/R= 200 GeV the KK effects in these processes are governed by a 17% enhancement of the ΔF=2 box diagram function S(x_t,1/R) and by a 37% enhancement of the Z^0 penguin diagram function C(x_t/1/R) relative to their Standard Model (SM) values. This implies the suppressions of \vtd by 8%, of \barηby 11% and of the angle γin the unitarity triangle by 10^\circ. ΔM_s is increased by 17%. ΔM_K is essentially uneffected. All branching ratios considered in this paper are increased with a hierarchical structure of enhancements: K^+\to π^+ν\barν(16%), K_L\to π^0ν\barν(17%), B\to X_{d}ν\barν(22%), (K_L\toμ\barμ)_{\rm SD} (38%), B\to X_{s}ν\barν(44%), B_{d}\toμ\barμ(46%) and B_{s}\toμ\barμ(72%). For 1/R= 250 (300) GeV all these effects are decreased roughly by a factor of 1.5 (2.0). We give the relevant Feynman rules for the five dimensional ACD model. We also emphasize that a consistent calculation of branching ratios has to take into account the modifications in the values of the CKM parameters. As a byproduct we confirm the dominant \ord (g_2 G_F m_t^4 R^2) correction from the KK modes to the $Z^0 b\bar b$ vertex calculated recently in the large m_t limit.

hep-ph↗