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Gino Isidori

Publications and source records attributed to Gino Isidori.

At least 127 records · Page 7Linked to original sources
arXiv2008

Constraints on New Physics in MFV models: a model-independent analysis of Delta F=1 processes

We analyse the constraints on dimension-six Delta F=1 effective operators in models respecting the MFV hypothesis, both in the one-Higgs doublet case and in the two-Higgs doublet scenario with large tan beta. The constraints are derived mainly from the b -> s inclusive observables measured at the B factories. The implications of these bounds in view of improved measurements in exclusive and inclusive observables in b -> s l^+ l^- and s -> d nu nubar transitions are discussed.

hep-ph↗
arXiv2008

Heavy Vectors in Higgs-less models

One or more heavy spin-1 fields may replace the Higgs boson in keeping perturbative unitarity up to a few TeV. By means of two prototype chiral models for the heavy spin-1 bosons, a "composite" model or a "gauge" model, we discuss if and how the sole exchange of the same fields can also account for the ElectroWeak Precision Tests. While this proves impossible in the gauge model, the composite model hints to a positive solution, which we exploit to constrain the phenomenological properties of the heavy vectors.

hep-ph↗
arXiv2008

Solving the flavour problem with hierarchical fermion wave functions

We investigate the flavour structure of generic extensions of the SM where quark and lepton mass hierarchies and the suppression of flavour-changing transitions originate only by the normalization constants of the fermion kinetic terms. We show that in such scenarios the contributions to quark FCNC transitions from dimension-six effective operators are sufficiently suppressed without (or with modest) fine tuning in the effective scale of new physics. The most serious challenge to this type of scenarios appears in the lepton sector, thanks to the stringent bounds on LFV. The phenomenological consequences of this scenarios in view of improved experimental data on quark and lepton FCNC transitions, and its differences with respect to the Minimal Flavour Violation hypothesis are also discussed.

hep-ph↗
arXiv2008

Flavour Physics: Now and in the LHC era

We present an overview of what we learned so far from low-energy flavour observables, concerning physics beyond the Standard Model, and what we could still learn from further studies in flavour physics in the next few years.

hep-ph↗
arXiv2007

Soft-photon corrections in multi-body meson decays

The effects due to soft-photon emission (and the related virtual corrections) in multi-body decays of B, D, and K mesons are analysed. We present analytic expressions for the universal O(alpha) correction factors which can be applied to all multi-body decay modes where a tight soft-photon energy cut in the decaying-particle rest-frame is applied. All-order resummations valid in the limit of small and large velocities of the final-state particles are also discussed. The phenomenological implications of these correction factors in the distortion of Dalitz-plot distributions of K -> 3 pi decays are briefly analysed.

hep-ph↗
arXiv2007

Gravitational corrections to Standard Model vacuum decay

We refine and update the metastability constraint on the Standard Model top and Higgs masses, by analytically including gravitational corrections to the vacuum decay rate. Present best-fit ranges of the top and Higgs masses mostly lie in the narrow metastable region. Furthermore, we show that the SM potential can be fine-tuned in order to be made suitable for inflation. However, SM inflation results in a power spectrum of cosmological perturbations not consistent with observations.

hep-ph↗
arXiv2007

Quantum Resonant Leptogenesis and Minimal Lepton Flavour Violation

It has been recently shown that the quantum Boltzmann equations may be relevant for the leptogenesis scenario. In particular, they lead to a time-dependent CP asymmetry which depends upon the previous dynamics of the system. This memory effect in the CP asymmetry is particularly important in resonant leptogenesis where the asymmetry is generated by the decays of nearly mass-degenerate right-handed neutrinos. We study the impact of the non-trivial time evolution of the CP asymmetry in the so-called Minimal Lepton Flavour Violation framework where the charged-lepton and the neutrino Yukawa couplings are the only irreducible sources of lepton-flavour symmetry breaking and resonant leptogenesis is achieved. We show that significant quantitative differences arise with respect to the case in which the time dependence of the CP asymmetry is neglected.

hep-ph↗
arXiv2007

Large tan(beta) effects in flavour physics

After a short introduction to the SUSY flavour problem, we focus the attention on the MSSM with MFV and large $\tanβ$. The theoretical motivations and the general features of this scenario are briefly reviewed. The possible signatures in low-energy flavour-violating observables are discussed, with particular attention to the role played by $\BR(P\to\ellν)$, $\BR(B_{s,d}\to \ell^+\ell^-)$ and $\BR(μ\to e γ)$

hep-ph↗
arXiv2007

Flavour physics at large tan(beta) with a Bino-like LSP

The MSSM with large tan(beta) and heavy squarks is a theoretically well motivated and phenomenologically interesting extension of the SM. This scenario naturally accommodates the (g-2)_μanomaly and the upper bound on the Higgs boson mass. In a wide region of the parameter space, visible non-standard effects are expected in a few low-energy observables, such as BR(B->tau nu), BR(B->l+ l-), BR(B->Xs gamma), and BR(mu->e gamma). We analyse the correlations of these non-standard effects under the additional assumption that the relic density of a Bino-like LSP accommodates the observed dark matter distribution.

hep-ph↗
arXiv2007

Hints of large tan(beta) in flavour physics

Motivated by the first evidence of the B -> tau nu transition reported by Belle and by the precise DeltaM_{B_s} measurement by CDF, we analyse these and other low-energy observables in the framework of the MSSM at large tan(beta). We show that for heavy squarks and A terms (M_squarks, A_U > 1 TeV) such scenario has several interesting virtues. It naturally describes: i) a suppression of BR(B->tau nu) of (10-40)%, ii) a sizable enhancement of (g-2)_mu, iii) a heavy SM-like Higgs (m_h ~ 120 GeV), iv) small non-standard effects in DeltaM_{B_s} and BR(B -> X_s gamma) (in agreement with present observations). The possibilities to find more convincing evidences of such scenario, with improved data on BR(B -> tau nu), BR(B -> l+ l-) and other low-energy observables, are briefly discussed.

hep-ph↗
arXiv2007

Shedding light on flavour symmetries with rare decays of quarks and leptons

The impact of rare lepton decays ($μ\to e γ$, $τ\to μγ$, >...) and rare $B$ and $K$ decays ($B\to \ell^+\ell^-$, $B\to \ellν$, $K\to πνν$, $K\to\ellν$, ...) in probing the existence of an underlying flavour symmetry is reviewd. Particualar emphasis is deveoted to the connections between quark and lepton flavour strucutres, in the context of generic effective field theory approach to physics beyond the SM.

hep-ph↗
arXiv2007

The smallest neutrino mass

We consider models where one Majorana neutrino is massless at tree level (like the see saw with two right-handed neutrinos), and compute the contribution to its mass m generated by two-loop quantum corrections. The result is m \sim 10^{-13}eV in the SM and m \sim 10^{-10} eV (tanBeta/10)^4 in the MSSM, compatible with the restricted range suggested by Affleck-Dine baryogenesis.

hep-ph↗
arXiv2006

CP violation and Leptogenesis in models with Minimal Lepton Flavour Violation

We investigate the viability of leptogenesis in models with three heavy right-handed neutrinos, where the charged-lepton and the neutrino Yukawa couplings are the only irreducible sources of lepton-flavour symmetry breaking (Minimal Lepton Flavour Violation hypothesis). We show that in this framework a specific type of resonant leptogenesis can be successfully accomplished. For natural values of the free parameters, this mechanism requires a high right-handed neutrino mass scale ($M_ν\gsim 10^{12}$ GeV). By means of a general effective field theory approach, we analyse the impact of the CP violating phases responsible for leptogenesis on the low-energy FCNC observables and derive bounds on the scale of flavour violating new physics interactions. As a result of the high value of the scale of total lepton-number violation, in this class of models the $μ\to eγ$ decay is expected to be close to the present exclusion limit (under the additional assumption of new particles carrying lepton flavour at the TeV scale).

hep-ph↗
arXiv2006

Grand Unification and the Principle of Minimal Flavor Violation

Minimal Flavor Violation is an attractive approach to suppress unacceptably large flavor changing neutral currents from beyond the standard model physics at the TeV scale. It can be used in theories with low energy supersymmetry, multi Higgs doublet theories and other extensions of the minimal standard model. We show how minimal flavor violation can be implemented in Grand Unified theories.

hep-ph↗
arXiv2006

Flavor Physics with light quarks and leptons

The impact of rare K decays and lepton-flavor violating processes in shedding light on physics beyond the Standard Model is reviewd. To this purpose, I first recall the formulation of the Minimal Flavor Violation hypothesis --both in the quark and in the lepton sector-- and then use it as guiding principle in comparing the new-physics sensitivity of different rare processes. On the phenomenological side, the discussion is focused mainly on the impact of K -> pi nu nu-bar, mu -> e gamma, and lepton-flavor universality tests with Kl2 and Pl2 decays.

hep-ph↗
arXiv2006

Exploring the flavour structure of the MSSM with rare K decays

We present an extensive analysis of rare K decays, in particular of the two neutrino modes K+->pi+ nu nu-bar and KL->pi0 nu nu-bar, in the Minimal Supersymmetric extension of the Standard Model. We analyse the expectations for the branching ratios of these modes, both within the restrictive framework of the minimal flavour violation hypothesis and within a more general framework with new sources of flavour-symmetry breaking. In both scenarios, the information that can be extracted from precise measurements of the two neutrino modes turn out to be very useful in restricting the parameter space of the model, even after taking into account the possible information on the mass spectrum derived from high-energy colliders, and the constraints from B-physics experiments. In the presence of new sources of flavour-symmetry breaking, additional significant constraints on the model can be derived also from the two KL->pi0 l+l- modes.

hep-ph↗
arXiv2006

The e+ e- -> P1 P2 gamma processes close to the Phi peak: toward a model-independent analysis

We discuss the general decomposition and possible general parameterizations of the processes $e^+ e^- \to γ^* \to P_1 P_2 γ$, where $P_1 P_2=π^0 π^0$, $π^0η$, or $π^+π^-$, for $\sqrt{s}\approx M_Φ$. Particular attention is devoted to the amplitude where the two pseudoscalar mesons are in a $J^{CP}= 0^{++}$ state, where we propose a general parameterization which should help to shed light on the nature of light scalar mesons.

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