21 research outputs found
The Impact of Universal Extra Dimensions on FCNC Processes
We review the results of two papers on FCNC processes in the Appelquist,
Cheng and Dobrescu (ACD) model with one universal extra dimension.Comment: Invited talk at the Workshop on the CKM Unitarity Triangle, IPPP
Durham, April 2003 (eConf C0304052). 7 pages LaTeX, 5 eps figure
Charged Lepton Flavour Violation and (g-2)_mu in the Littlest Higgs Model with T-Parity: a clear Distinction from Supersymmetry
We calculate the rates for the charged lepton flavour violating decays l_i ->
l_j gamma, tau -> l pi, tau -> l eta, tau -> l eta', mu^- -> e^- e^+ e^-, the
six three body leptonic decays tau^- -> l_i^- l_j^+ l_k^- and the rate for mu-e
conversion in nuclei in the Littlest Higgs model with T-Parity (LHT). We also
calculate the rates for K_{L,S} -> mu e, K_{L,S} -> pi^0 mu e and B_{d,s} ->
l_i l_j. We find that the relative effects of mirror leptons in these
transitions are by many orders of magnitude larger than analogous mirror quark
effects in rare K and B decays analyzed recently. In particular, in order to
suppress the mu -> e gamma and mu^- -> e^- e^+ e^- decay rates and the mu-e
conversion rate below the experimental upper bounds, the relevant mixing matrix
in the mirror lepton sector V_Hl must be rather hierarchical, unless the
spectrum of mirror leptons is quasi-degenerate. We find that the pattern of the
LFV branching ratios in the LHT model differs significantly from the one
encountered in the MSSM, allowing in a transparent manner to distinguish these
two models with the help of LFV processes. We also calculate (g-2)_mu and find
the new contributions to a_mu below 10^{-10} and consequently negligible. We
compare our results with those present in the literature.Comment: 57 pages, 19 figures, 3 tables. Note added on the omitted term in
Z-penguin contribution. For an updated analysis see arXiv:0906.545
Rare and CP-Violating K and B Decays in the Littlest Higgs Model with T-Parity
We calculate the most interesting rare and CP-violating K and B decays in the
Littlest Higgs model with T-parity. We give a collection of Feynman rules
including v^2/f^2 contributions that are presented here for the first time and
could turn out to be useful also for applications outside flavour physics. We
adopt a model-independent parameterization of rare decays in terms of the gauge
independent functions X_i,Y_i,Z_i (i=K,d,s), which is in particular useful for
the study of the breaking of the universality between K, B_d and B_s systems
through non-MFV interactions. Performing the calculation in the unitary and 't
Hooft-Feynman gauge, we find that the final result contains a divergence which
signals some sensitivity to the ultraviolet completion of the theory. Including
an estimate of this contribution, we calculate the branching ratios for the
decays , , , , and , paying particular attention to non-MFV contributions
present in the model.
Imposing all available constraints we find that the decay rates for and can be enhanced by at most
50% and 35% relative to the SM values, while and
can be both as high as .
Significant enhancements of the decay rates are also
possible. Simultaneously, the CP-asymmetries and
can be enhanced by an order of magnitude, while the electroweak
penguin effects in turn out to be small, in agreement with the
recent data.Comment: 65 pages, 19 figures. Note added on omitted term in Z-penguin
contribution. For an updated analysis see arXiv:0906.545
Rare K and B Decays in the Littlest Higgs Model without T-Parity
We analyze rare K and B decays in the Littlest Higgs (LH) model without
T-parity. We find that the final result for the Z^0-penguin contribution
contains a divergence that is generated by the one-loop radiative corrections
to the currents corresponding to the dynamically broken generators. Including
an estimate of these logarithmically enhanced terms, we calculate the branching
ratios for the decays K^+ -> pi^+ nu bar nu, K_L -> pi^0 nu bar nu, B_{s,d} ->
mu^+ mu^- and B -> X_{s,d} nu bar nu. We find that for the high energy scale
f=O(2-3) TeV, as required by the electroweak precision studies, the enhancement
of all branching ratios amounts to at most 15% over the SM values. On the
technical side we identify a number of errors in the existing Feynman rules in
the LH model without T-parity that could have some impact on other analyses
present in the literature. Calculating penguin and box diagrams in the unitary
gauge, we find divergences in both contributions that are cancelled in the sum
except for the divergence mentioned above.Comment: 39 pages, 8 figures, typos corrected, comment on (2.17) and (2.18)
added, references added, results unchange
Climate targets in European timber-producing countries conflict with goals on forest ecosystem services and biodiversity
The role of increased timber harvests in reaching climate mitigation targets for European countries will be limited if the protection of forest ecosystem services and biodiversity is to be achieved, suggests an empirical forest model driven by future scenarios to limit warming to 1.5 degrees C in 2100.The European Union (EU) set clear climate change mitigation targets to reach climate neutrality, accounting for forests and their woody biomass resources. We investigated the consequences of increased harvest demands resulting from EU climate targets. We analysed the impacts on national policy objectives for forest ecosystem services and biodiversity through empirical forest simulation and multi-objective optimization methods. We show that key European timber-producing countries - Finland, Sweden, Germany (Bavaria) - cannot fulfil the increased harvest demands linked to the ambitious 1.5 degrees C target. Potentials for harvest increase only exists in the studied region Norway. However, focusing on EU climate targets conflicts with several national policies and causes adverse effects on multiple ecosystem services and biodiversity. We argue that the role of forests and their timber resources in achieving climate targets and societal decarbonization should not be overstated. Our study provides insight for other European countries challenged by conflicting policies and supports policymakers
Particle-Antiparticle Mixing, epsilon_K, Delta Gamma_q, A_SL^q, A_CP(B_d -> psi K_S), A_CP(B_s -> psi phi) and B -> X_{s,d} gamma in the Littlest Higgs Model with T-Parity
We calculate a number of observables related to particle-antiparticle mixing
in the Littlest Higgs model with T-parity (LHT). The resulting effective
Hamiltonian for Delta F=2 transitions agrees with the one of Hubisz et al., but
our phenomenological analysis goes far beyond the one of these authors. In
particular, we point out that the presence of mirror fermions with new flavour
and CP-violating interactions allows to remove the possible Standard Model (SM)
discrepancy between the CP asymmetry S_{psi K_S} and large values of |V_ub| and
to obtain for the mass difference Delta M_s < (Delta M_s)_SM as suggested by
the recent result by the CDF collaboration. We also identify a scenario in
which simultaneously significant enhancements of the CP asymmetries S_{phi psi}
and A_SL^q relative to the SM are possible, while satisfying all existing
constraints, in particular from the B -> X_s gamma decay and A_CP(B -> X_s
gamma) that are presented in the LHT model here for the first time. In another
scenario the second, non-SM, value for the angle gamma=-(109+-6) from tree
level decays, although unlikely, can be made consistent with all existing data
with the help of mirror fermions. We present a number of correlations between
the observables in question and study the implications of our results for the
mass spectrum and the weak mixing matrix of mirror fermions. In the most
interesting scenarios, the latter one turns out to have a hierarchical
structure that differs significantly from the CKM one.Comment: 51 pages, 20 figures, 1 table. Extended discussion of the phases in
the new mixing matrix V_Hd, some references added or updated, conclusions
unchanged. Final version published in JHE
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.Comment: Main latex-file, 8 figures, 41 page