arXiv subjects

Enrico Lunghi

Publications and source records attributed to Enrico Lunghi.

47 records · Page 3Linked to original sources

arXiv2008

Possible Indications of New Physics in Bd-mixing and in sin(2 beta) Determinations

Using the hadronic matrix elements from the lattice, B_K and xi_s, involving only the 4-quark operators for Delta flavor (F) = 2 Hamiltonian relevant for K, B_d and B_s mixing, along with V_cb, we deduce a non-trivial constraint on the SM, sin (2 beta) = 0.87+-0.09. This deviates from direct experimental measurements via the tree process, b -> c c s as well as the one via the penguin-loop b -> s decays by around 2.1 and 2.7 sigma respectively. If these deviations are confirmed they would imply the presence of new physics rather pervasively in both B_d mixing (i.e. very likely in b -> d) as well as in b -> s transitions requiring a beyond the SM CP-odd phase. Consequently, improvements in the relevant lattice calculations should be given a high priority.

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arXiv2008

Logarithmically Enhanced Corrections to the Decay Rate and Forward Backward Asymmetry in anti-B --> X(s) l+ l-

We study logarithmically enhanced electromagnetic corrections to the decay rate in the high dilepton invariant mass region as well as corrections to the forward backward asymmetry (FBA) of the inclusive rare decay $\bar{B} \to X_s \ell^+ \ell^-$. As expected, the relative effect of these corrections in the high dilepton mass region is around -8% for the muonic final state and therefore much larger than in the low dilepton mass region. We also present a complete phenomenological analysis, to improved NNLO accuracy, of the dilepton mass spectrum and the FBA integrated in the low dilepton mass region, including a new approach to the zero of the FBA. The latter represents one of the most precise predictions in flavour physics with a theoretical uncertainty of order 5%. We find $(q_0^2)_{μμ} = (3.50 \pm 0.12) \gev^2$. For the high dilepton invariant mass region, we have ${\cal B}(\bar B\to X_sμμ)_{\rm high} = (2.40^{+0.69}_{-0.62}) \times 10^{-7}$. The dominant uncertainty is due to the $1/m_b$ corrections and can be significantly reduced in the future. For the low dilepton invariant mass region, we confirm previous results up to small corrections.

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arXiv2008

Light charged Higgs at the beginning of the LHC era

The terascale will be explored with the start of the LHC. One of the most fundamental questions which we expect to be answered is the root of electroweak symmetry breaking and whether the Higgs mechanism is realized in nature or not. In this context we pose the question if existing experimental data still allow for a light non-minimal Higgs sector. We tackle this question first in the context of the two Higgs doublet model and then we concentrate in two supersymmetric models, the constrained MSSM and the MSSM with non-universal Higgs masses. In both supersymmetric scearios, light pseudoscalar and light charged-Higgs bosons are still viable provided tan beta is large. In this regime, we emphasize the importance of the constraints provided by the decay B to tau nu mediated by the charged-Higgs at tree-level. In addition we comment on generic predictions for hadronic colliders and indirect searches in such scenarios.

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arXiv2007

Kinetic corrections to B -> X_c l nu at one loop

We evaluate the one-loop corrections to the Wilson coefficient of the kinetic operator in the operator product expansion of the differential B -> X_c l nu decay rate. With a moderate cut on the lepton energy, the one-loop terms change the kinetic operator contributions to spectral moments by about 20%. This amounts to a small correction for leptonic and hadronic moments, except for those which vanish at the lowest order, where the effect can be sizable. Together with a two-loop calculation of the leading-power rate and an evaluation of the one-loop corrections to the Wilson coefficient of the chromo-magnetic operator, our results will allow for a high-precision determination of |V_cb| and the b- and c-quark masses.

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arXiv2007

Footprints of the Beyond in flavor physics: Possible role of the Top Two Higgs Doublet Model

The B-factories results provide an impressive confirmation of the Standard Model (SM) description of flavor and CP violation. Nevertheless, as more data were accumulated, deviations in the 2.5-3.5 sigma range have emerged pointing to the exciting possibility of new CP-odd phase(s) and flavor violating parameters in B-decays. Primarily this seems to be the case in the time dependent CP asymmetries in penguin dominated modes (e.g. B -> phi (eta') Ks). We discuss these and other deviations from the SM and, as an illustration of possible new physics scenarios, we examine the role of the Top Two Higgs Doublet Model. This is a simple extension of the SM obtained by adding second Higgs doublet in which the Yukawa interactions of the two Higgs doublets are assigned in order to naturally account for the large top-quark mass. Of course, many other extensions of the Standard Model could also account for these experimental deviations. Clearly if one takes these deviations seriously then some new particles in the 300 GeV to few TeV with associated new CP-odd phase(s) are needed.

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arXiv2006

Analysis of enhanced tan(beta) corrections in MFV GUT scenarios

We analyse a minimal supersymmetric standard model (MSSM) taking a minimal flavour violation (MFV) structure at the GUT scale. We evaluate the parameters at the electroweak scale taking into account the full flavour structure in the evolution of the renormalization group equations. We concentrate mainly on the decay Bs -> mu mu and its correlations with other observables like b -> s gamma, b -> s l l, Delta M_Bs and the anomalous magnetic moment of the muon. We restrict our analysis to the regions in parameter space consistent with the dark matter constraints. We find that the BR(Bs -> mu mu) can exceed the current experimental limit in the regions of parameter space which are allowed by all other constraints thus providing an additional bound on supersymmetric parameters. This holds even in the constrained MSSM. Assuming an hypothetical measurement of BR(Bs -> mu mu) ~ 10^-7 we analyse the predicted MSSM spectrum and flavour violating decay modes of supersymmetric particles which are found to be small.

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arXiv2006

Subleading collinear operators and their matrix elements

We discuss the most general form of the leading power suppressed collinear operators in the soft-collinear effective theory. Such operators appear in the description of power corrections to exclusive heavy flavor decays into energetic light hadrons. Reparametrization invariance in the SCET provides powerful constraints on the Wilson coefficients of the subleading collinear operators. We present explicit results for the matrix elements of these operators on pseudoscalar and vector mesons, which are expressed in terms of twist-2 and twist-3 light-cone wave functions. We consistently include the effects of three-particle light-cone distribution amplitudes and find that their impact could be of phenomenological relevance.

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arXiv2003

On Exclusive and Inclusive Rare B Decays: CKM Phenomenology and New Physics Reach

We report recent results in rare B decays. Our focus will be on b -> d gamma and b -> s l^+ l^- transitions. We discuss their impact on the CKM phenomenology and their role within our search for new physics. In particular, we analyse the impact of a recent lattice QCD estimate of the B -> K* form factor at zero recoil. We also briefly discuss the presently available optimal theoretical tools for the inclusive and exclusive modes.

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arXiv2002

Factorization in leptonic radiative B -> gamma eνdecays

We discuss factorization in exclusive radiative leptonic B->γeνdecays using the soft-collinear effective theory. The form factors describing these decays can be expanded in a power series in Lambda/E_γwith E_γthe photon energy. We write down the most general operators in the effective theory which contribute to the form factors at leading order in Lambda_QCD/E_γ, proving their factorization into hard, jet and soft contributions, to all orders in alpha_s.

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arXiv2002

Implications of B -> rho gamma measurements in the Standard Model and Supersymmetric Theories

We study the implications of the recently improved upper limits on the branching ratios for the decays B -> rho gamma, expressed as R(rho gamma/K^* gamma) = BR(B -> rho gamma)/BR(B -> K^* gamma) <0.047. We work out the constraints that the current bound on R(rho gamma/K^* gamma) implies on the parameters of the quark mixing matrix in the standard model (SM). Using the present profile of the unitarity triangle, we predict this ratio to be R(rho gamma/K^* gamma) = 0.023 +/- 0.012. We also work out the correlations involving R(rho gamma/K^* gamma), the isospin-violating ratio Delta (rho gamma), and the direct CP-violating asymmetry A_CP (rho gamma) in B -> rho gamma decays in the SM, in the minimal supersymmetric extension of the SM (MSSM), and in an extension of the MSSM involving an additional flavor-changing structure in b -> d transitions.

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arXiv2000

CP Violation in rare semileptonic B decays and supersymmetry

We study the effect of new flavor changing SUSY phases arising in the squark mass matrix in semileptonic decays B->Xs ll and B->K(*) ll (l=e,mu). SUSY effects are parametrized using the mass insertion approximation formalism. Constraints on SUSY contributions coming from other processes (e.g. b->s gamma, B->K* ll) are taken into account. Chargino and gluino contributions to photon and Z-mediated decays are included and non-perturbative corrections are considered. We study the correlation between the CP (and forward--backward) asymmetries and the expected value of the inclusive branching ratio. Several possible scenarios are distinguished and discussed according to the mass insertion that is considered.

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