arXiv subjects

P. Santorelli

Publications and source records attributed to P. Santorelli.

At least 19 recordsLinked to original sources

arXiv2023

Prediction of various observables for $B_s^0 \to D_s^{(*)-}\ell^+\nu_\ell$ within covariant confined quark model

In 2020, the LHCb collaboration reported the exclusive branching fractions for the channels $B_s^0 \to D_s^{(*)-}\mu^+\nu_\mu$ for the very first time. In view of these observations, we have recently reported the form factors and branching fraction computations for these channels employing the covariant confined quark model. As different other channels corresponding to $b \to c \ell \nu_\ell$ have provided the hint for New Physics, the analysis of observables such as forward-backward asymmetry, longitudinal and transverse polarizations across the lepton flavours can serve as one of the important probes for the search for possible New Physics. In present work, we compute these observables for all the lepton flavours and compare our predictions with the other theoretical approaches.

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arXiv2017

A neutrino mass-mixing sum rule from SO(10) and neutrinoless double beta decay

Minimal SO(10) grand unified models provide phenomenological predictions for neutrino mass patterns and mixing. These are the outcome of the interplay of several features, namely: i) the seesaw mechanism; ii) the presence of an intermediate scale where B-L gauge symmetry is broken and the right-handed neutrinos acquire a Majorana mass; iii) a symmetric Dirac neutrino mass matrix whose pattern is close to the up-type quark one. In this framework two natural characteristics emerge. Normal neutrino mass hierarchy is the only allowed, and there is an approximate relation involving both light-neutrino masses and mixing parameters. This differs from what occurring when horizontal flavour symmetries are invoked. In this case, in fact, neutrino mixing or mass relations have been separately obtained in literature. In this paper we discuss an example of such comprehensive mixing-mass relation in a specific realization of SO(10) and, in particular, analyse its impact on the expected neutrinoless double beta decay effective mass parameter $\langle m_{ee} \rangle$, and on the neutrino mass scale. Remarkably a lower limit for the lightest neutrino mass is obtained ($m_{\rm lightest} \gtrsim 7.5 \times 10^{-4}$ eV, at 3 $σ$ level).

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arXiv2006

Semileptonic B decays into even parity charmed mesons

By using a constituent quark model we compute the form factors relevant to semileptonic transitions of B mesons into low-lying p-wave charmed mesons. We evaluate the q^2 dependence of these form factors and compare them with other model calculations. The Isgur-Wise functions tau(1/2) and tau(3/2) are also obtained in the heavy quark limit of our results.

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arXiv2003

Charming penguins in B => K* pi, K (rho,omega,phi) decays

We evaluate the decays B => K* pi, K (rho,omega,phi) adding the long distance charming penguin contributions to the short distance: Tree+Penguin amplitudes. We estimate the imaginary part of the charming penguin by an effective field theory inspired by the Heavy Quark Effective Theory and parameterize its real part. The final results for branching ratios depend on only two real parameters and show a significant role of the charming penguins. The overall agreement with the available experimental data is satisfactory.

hep-ph↗

arXiv2002

Charming penguin contributions to charmless B decays into two pseudoscalar mesons

We present estimates of the charming penguin contribution to B => K pi, pi pi,K eta, K eta' decays due to intermediate charmed meson states. We find that this contribution is indeed significant for B => K pi decays, and its inclusion, together with the tree and penguin terms, produces large branching ratios in agreement with data, though the analysis is affected by large theoretical uncertainties. On the other hand, for B => pi pi, K eta, K eta' decays, the effect of the charming penguin contribution is more modest. We also compute CP asymmetries for B => K pi, pi pi decays and we obtain rather large results.

hep-ph↗

arXiv2001

Charming penguin contributions to B => K π

We present calculations of the charming-penguin long-distance contributions to B => K πdecays due to intermediate charmed meson states. Our calculation is based on the Chiral Effective Lagrangean for light and heavy mesons, corrected for the hard pion and kaon momenta. We find that the charming-penguin contributions increase significantly the B => K πdecay rates in comparison with the short-distance contributions, giving results in better agreement with experimental data.

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arXiv2000

The semileptonic decays of the B_c meson

We study the semileptonic transitions B_c to η_c, J/ψ, D, D^*, B, B^*, B_s, B_s^* in the framework of a relativistic constituent quark model. We use experimental data on leptonic J/ψdecay, lattice and QCD sum rule results on leptonic B_c decay, and on radiative η_c transitions to adjust the quark model parameters. We compute all form factors of the above semileptonic B_c-transitions and give predictions for various semileptonic B_c decay modes including their τ-modes when they are kinematically accessible. The implications of heavy quark symmetry for the semileptonic decays are discussed and are shown to be manifest in our explicit relativistic quark model calculation. A comparison of our results with the results of other calculations is performed.

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arXiv2000

A search for Z' in muon neutrino associated charm production

In many extensions of the Standard Model the presence of an extra neutral boson, Z', is invoked. A precision study of weak neutral-current exchange processes involving only second generation fermions is still missing. We propose a search for Z' in muon neutrino associated charm production. This process only involves Z' couplings with fermions from the second generation. An experimental method is thoroughly described using an ideal detector. As an application, the accuracy reachable with present and future experiments has been estimated.

hep-ph↗

arXiv2000

B and B_s decays into three pseudoscalar mesons and the determination of the angle gamma of the unitarity triangle

We reconsider two classical proposals for the determination of the angle gamma of the unitarity triangle: B^\pm => chi_{c0} π^\pm => π^+π^-π^\pm and B_s => rho^0 K_S => π^+ π^- K_S. We point out the relevance, in both cases, of non resonant amplitudes, where the π^+ π^- pair is produced by weak decay of a B^* (J^P=1^-) or B_0 (J^P=0^+) off-shell meson. In particular, for the B decay channel, the inclusion of the B_0 pole completes some previous analyses and confirms their conclusions, provided a suitable cut in the Dalitz plot is performed; for the B_s decay the inclusion of the B^*, B_0 amplitudes enhances the role of the tree diagrams as compared to penguin amplitudes, which makes the theoretical uncertainty related to the B_s => rho^0 K_S decay process less significant. While the first method is affected by theoretical uncertainties, the second one is cleaner, but its usefulness will depend on the available number of events to perform the analysis.

hep-ph↗

arXiv2000

Measuring B -> rho pi decays and the unitarity angle alpha

The decay mode B -> rho pi is currently studied as a channel allowing, in principle, to measure without ambiguities the angle alpha of the unitarity triangle. It is also investigated by the CLEO Collaboration where a branching ratio larger than expected for the decay mode B+/- -> rho0 pi+/- has been found. We investigate the role that the B* and B(0+) resonances play in these analyses.

hep-ph↗

arXiv1999

Decay Constants and Semileptonic Form Factors of Pseudoscalar Mesons

A relativistic constituent quark model is adopted to give an unified description of the leptonic and semileptonic decays of pseudoscalar mesons (π, K, D, D_s, B, B_s). The calculated leptonic decay constants and form factors are found to be in good agreement with available experimental data and the results of other approaches. Eventually, the model is found to reproduce the scaling behaviours of spin-flavor symmetry in the heavy-quark limit.

hep-ph↗

arXiv1999

B => ππ\ell νdecays in a QCD relativistic potential model

In the framework of a QCD relativistic potential model we evaluate the form factors describing the exclusive decay B => ππ\ell ν. The calculation is performed in a phase space region far away from the resonances and therefore is complementary to other decay mechanisms where the pions are produced by intermediate particles, e.g. in the chiral approach. We give an estimate of the contribution of the non resonant channel of the order of BR(B- => π+ π- \ell ν) \approx 2.2 x 10^(-4).

hep-ph↗

arXiv1999

A direct evaluation of the Lambda_c^+ absolute branching ratios: a new approach

A novel method for a direct measurement of the exclusive Lambda_c^+ branching ratios is here described. The approach is based on the peculiar topology of the quasi-elastic charm neutrino-induced events on nucleons. The intrinsic potentiality of the method is thoroughly discussed using a "perfect detector". As an application, the statistical accuracy reachable with existing data sample has been estimated. From a theoretical point of view, such measurement provides a better understanding of the baryonic b-decays.

hep-ph↗

arXiv1999

The semileptonic form factors of B and D mesons in the Quark Confinement Model

The form factors of the weak currents, which appear in the semileptonic decays of the heavy pseudoscalar mesons, are calculated within the quark confinement model by taking into account, for the first time, the structure of heavy meson vertex and the finite quark mass contribution in the heavy quark propagators. The results are in quite good agreement with the experimental data.

hep-ph↗

arXiv1999

Leptonic and Semileptonic Decays of Pseudoscalar Mesons

We employ the relativistic constituent quark model to give a unified description of the leptonic and semileptonic decays of pseudoscalar mesons (π, K, D, D_s, B, B_s). The calculated leptonic decay constants and form factors are found to be in good agreement with available experimental data and other approaches. We reproduce the results of spin-flavor symmetry in the heavy quark limit.

hep-ph↗

arXiv1999

Semileptonic and rare B meson decays into a light pseudoscalar meson

In the framework of a QCD relativistic potential model we evaluate the form factors describing the exclusive decays B => πl nu and B => K l+ l-. The present calculation extends a previous analysis of B meson decays into light vector mesons. We find results in agreement with the data, when available, and with the theoretical constraints imposed by the Callan-Treiman relation and the infinite heavy quark mass limit.

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arXiv1998

Semileptonic and Rare $B$-meson transitions in a QCD relativistic potential model

Using a QCD relativistic potential model, previously applied to the calculation of the heavy meson leptonic constants, we evaluate the form factors governing the exclusive decays $B\toρ\ellν$, $B\to K^*γ$ and $B\to K^*\ell^+\ell^-$. In our approach the heavy meson is described as a $Q\bar q$ bound state, whose wave function is solution of the relativistic Salpeter equation, with an instantaneous potential displaying Coulombic behaviour at small distances and linear behaviour at large distances. The light vector meson is described by using a vector current interpolating field, according to the Vector Meson Dominance assumption. A Pauli-Villars regularized propagator is assumed for the quarks not constituting the heavy meson. Our procedure allows to avoid the description of the light meson in terms of wave function and constituent quarks, and consequently the problem of boosting the light meson wave function. Assuming as an input the experimental results on $B\to K^*γ$, we evaluate all the form factors describing the $B\to ρ, K^*$ semileptonic and rare transitions. The overall comparison with the data, whenever available, is satisfactory.

hep-ph↗

arXiv1998

Phenomenological Bounds on B to Light Semileptonic Form Factors

The form factors for the weak currents between B and light mesons are studied by relating them to the corresponding D form factors at q^2_{max} according to HQET, by evaluating them at q^2=0 by QCD sum rules, and by assuming a polar q^2 dependence. The results found are consistent with the information obtained from exclusive non-leptonic two-body decays and, with the only exception of A_1, with lattice calculations.

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