1,721,079 research outputs found
Minimal flavour violation waiting for precise measurements of Delta M-s, S-psi phi, A(SL)(s), vertical bar V-ub vertical bar, gamma and B-s,d(0)->mu(+)mu(-)
No full textWe emphasize that the recent measurements of the B(s)0-(B) over bar (s)0 mass difference Delta M-s by the CDF and D phi collaborations offer an important model independent test of minimal avour violation (MFV). The improved measurements of the angle in the unitarity triangle and of vertical bar Vub vertical bar from tree level decays, combined with future accurate measurements of Delta M-s, S-psi KS, S-psi phi, Br(B-d,B-s -> mu(+)mu(-)), Br( B -> X-d,X-s nu(nu) over bar), Br(K+ -> 1) and Br(K-L -> pi(0)nu(nu) over bar) and improved values of the relevant non-perturbative parameters, will allow to test the MFV hypothesis in a model independent manner to a high accuracy. In particular, the difference between the reference unitarity triangle obtained from tree level processes and the universal unitarity triangle (UUT) in MFV models would signal either new avour violating interactions and/or new local operators that are suppressed in MFV models with low tan beta with the former best tested through S-psi phi and K-L -> pi(0)nu nu. A brief discussion of non- MFV scenarios is also given. In this context we identify in the recent literature a relative sign error between Standard Model and new physics contributions to S-psi phi, that has an impact on the correlation between S-mu phi and A(SL)(s). We point out that the ratios S-psi phi/A(SL)(s) and Delta M-s/ Delta Gamma(s) will allow to determine Delta M-s/(Delta M-s)(SM). Similar proposals for the determination of Delta M-d/(Delta M-d)(SM) are also given
Littlest Higgs Model with T-Parity Confronting the New Data on D^0-\bar D^0 Mixing
No full textMotivated by the first experimental evidence of meson oscillations in the D system, we study D^0 - \bar D^0 mixing in the Littlest Higgs model with T-parity, we investigate its role in constraining the model parameters and its impact on the most interesting flavour observables. We find that the experimental data are potentially strongly constraining but at present limited by large theoretical uncertainties in the long-distance Standard Model contribution to D^0 - \bar D^0 mixing
Rare and CP-Violating K and B Decays in the Littlest Higgs Model with T-Parity
No full textWe 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
Charged lepton flavour violation and (g-2)mu in the littlest Higgs model with T-parity: a clear distinction from supersymmetry
No full textWe 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,K-S -> mu e, K-L,K-S -> pi(0)mu e and B-d,B-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 the pattern of the LFV branching rations in the LHT model differs significantly from the one encountered in the MSSM, allowing in a transparent manner to distinguish these two models with help of LFV processes. We also calculate (g-2)(mu) and find the new contributions to alpha(mu) below 1.10(-10) and consequently negligible. We compare our results with those present in the literature
Correlations between epsilon '/epsilon and rare K decays in the Littlest Higgs model with T-parity
No full textWe calculate the CP-violating ratio epsilon'/epsilon in the Littlest Higgs model with T-parity (LHT) and investigate its correlations with the braching ratios for K-L -> pi(0)vv,, K-L -> pi(0)l(+)l(-) and K+ -> pi(+)vv. The resulting correlations are rather strong in the case of K-L decays, but less pronounced in the case of K+ -> pi(0)vv. Unfortunately, they are subject to large hadronic uncertainties present in epsilon(')/epsilon, whose theoretical prediction in the Standard Model (SM) is reviewed and update here. With the matrix elements of Q(6) (gluon penguin) and Q(8) (electroweak penguin) evaluated in the large-N limit and m(s)(MS) (2 GeV) = 100 MeV from lattice QCD, (epsilon'/epsilon)(SM) turns out to be close to the data so that significant departures of Br(K-L -> pi(0)vv) and Br(K-L -> pi l(+)l(-)) from the SM expectations are unlikely, while Br(K+ -> pi(+)vv) can be enhanced even by a factor 5. On the other hand, modest departures of the relevant hadronic matrix elements from their large-N values allow for a consistent description of epsilon(')/epsilon within the LHT model accompanied by large enhancements of Br(K-L -> pi(0)l(+)l(-)) and Br(K-L -> pi(0)l(+)l(-)), but only modest enhancement of Br(K+ -> pi(+)vv)
Another look at the flavour structure of the Littlest Higgs model with T-parity
No full textWe discuss the mixing matrix VHd that describes the charged and neutral current interactions between ordinary down-quarks and up- and down-mirror quarks in the Littlest Higgs model with T-parity (LHT). We point out that this matrix in addition to three mixing angles contains three physical complex phases and not only one as used in the present literature. We explain the reason for the presence of two additional phases, propose a new standard parameterization of V-Hd and briefly comment on the relevance of these new phases for the phenomenology of FCNC processes in the LHT model. In a separate paper we present a detailed numerical analysis, including these new phases, of K and B physics, with particular attention to the most interesting rare decays. (c) 2007 Elsevier B.V. All rights reserved
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
No full textWe 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(KS) and large values of vertical bar V-ub vertical bar and to obtain for the mass difference Delta Ms 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 +/- 16)degrees 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
FCNC PROCESSES IN THE LITTLEST HIGGS MODEL WITH T-PARITY: AN UPDATE
No full textWe update our 2006-2007 results for FCNC processes in the Littlest Higgs model with T-parity (LHT). The removal of the logarithmic UV cutoff dependence in our previous results through a new contribution to the Z(0)-penguin diagrams identified by Goto et al. and del Aguila et al., while making the deviations from the SM expectations in the quark sector less spectacular, still allows for sizable new physics effects in K -> pi nu(nu) over bar and K(L) -> pi(0)l(+)l(-) decays and in the CP-asymmetry S(psi phi) with the latter unaffected by the new contribution. We extend our analysis by a study of the fine-tuning required to fit the data on epsilon(K) and by the inclusion of the decay K(L) -> mu(+)mu(-). A number of correlations can distinguish this model from the custodially protected Randall-Sundrum model analysed recently. We also reconsider lepton flavour violating decays, including now a discussion of fine-tuning. While the l(i) -> l(j)gamma decays are unaffected by the removal of the logarithmic cutoff dependence, the branching ratios for decays with three leptons in the final state, like mu -> 3e are lowered by almost an order of magnitude. In spite of this, the pattern of lepton flavour violation in the LHT model can still be distinguished from the one in supersymmetric models
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
