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F. De Fazio

Publications and source records attributed to F. De Fazio.

At least 37 records · Page 2Linked to original sources
arXiv2008

SCET sum rules for B->P and B->V transition form factors

We investigate sum rules for heavy-to-light transition form factors at large recoil derived from correlation functions with interpolating currents for light pseudoscalar or vector fields in soft-collinear effective theory (SCET). We consider both, factorizable and non-factorizable contributions at leading power in the Lambda/m_b expansion and to first order in the strong coupling constant alpha_s, neglecting contributions from 3-particle distribution amplitudes in the B-meson. We pay particular attention to various sources of parametric and systematic uncertainties. We also discuss certain form factor ratios where part of the hadronic uncertainties related to the B-meson distribution amplitude and to logarithmically enhanced alpha_s corrections cancel.

hep-ph↗
arXiv2008

FCNC $B_s$ and $Λ_b$ transitions: Standard Model versus a single Universal Extra Dimension scenario

We study the FCNC $B_s \to ϕγ, ϕν\bar ν$ and $Λ_b \to Λγ, Λν\bar ν$ transitions in the Standard Model and in a scenario with a single Universal Extra Dimension. In particular, we focus on the present knowledge of the hadronic uncertainties and on possible improvements. We discuss how the measurements of these modes can be used to constrain the new parameter involved in the extra dimensional scenario, the radius $R$ of the extra dimension, completing the information available from B-factories. The rates of these $b \to s$ induced decays are within the reach of new experiments, such as LHCb.

hep-ph↗
arXiv2008

B, D and K decays

With the advent of the LHC, we will be able to probe New Physics (NP) up to energy scales almost one order of magnitude larger than it has been possible with present accelerator facilities. While direct detection of new particles will be the main avenue to establish the presence of NP at the LHC, indirect searches will provide precious complementary information, since most probably it will not be possible to measure the full spectrum of new particles and their couplings through direct production. In particular, precision measurements and computations in the realm of flavour physics are expected to play a key role in constraining the unknown parameters of the Lagrangian of any NP model emerging from direct searches at the LHC. The aim of Working Group 2 was twofold: on one hand, to provide a coherent, up-to-date picture of the status of flavour physics before the start of the LHC; on the other hand, to initiate activities on the path towards integrating information on NP from high-pT and flavour data.

hep-ph↗
arXiv2007

Identifying $D_{sJ}(2700)$ through its decay modes

We study how to assign the recently observed $D_{sJ}(2700)$ meson to an appropriate level of the $c \bar s$ spectrum by the analysis of its decay modes in final states comprising a light pseudoscalar meson. We use an effective lagrangian approach with heavy quark and chiral symmetries, obtaining that the measurement of the $D^* K$ decay width would allow to distinguish between two possible assignments.

hep-ph↗
arXiv2007

Puzzles in charm spectroscopy

We briefly analyze aspects of open and hidden charm resonances, discussing in particular the mesons $D_{sJ}(2860)$ and X(3872).

hep-ph↗
arXiv2007

$X(3872) \to D \bar D γ$ decays and the structure of X(3872)

It has been suggested that the radiative $X \to D \bar D γ$ decay modes are useful to shed light on the structure of the meson X(3872), since the ratio $ R={Γ(X \to D^+ D^- γ) \over Γ(X \to D^0 \bar D^0 γ)}$ is expected to be small ($R \ll 1$) if $X$ is a molecular $D^{*0} \bar D^0$ state. We compute $R$ in a $\bar c c$ $J^{PC}=1^{++}$ description of $X$ finding that it is tiny in a wide range of hadronic parameters governing the decay. A discrimination between the molecular and $\bar c c$ description can be obtained through the analysis of the photon spectrum.

hep-ph↗
arXiv2007

On the light glueball spectrum in a holographic description of QCD

We investigate the spectra of light scalar and vector glueballs in a holografic description of QCD with a dilaton background bulk field. In particular, we study how the glueball masses depend on the conditions on the dilaton background and on the geometry of the bulk.

hep-ph↗
arXiv2006

Spin effects in rare $B \to X_s τ^+ τ^-$ and $B \to K^{(*)} τ^+ τ^-$ decays in a single Universal Extra Dimension scenario

We study the branching fractions and the lepton polarization asymmetries of rare $B \to X_s τ^+ τ^-$ and $B \to K^{(*)} τ^+ τ^-$ modes within the Standard Model and in the Appelquist-Cheng-Dobrescu model, which is a New Physics scenario with a single universal extra dimension. In particular, we investigate the sensitivity of the observables to the radius $R$ of the compactified extra-dimension, which is the only new parameter in this New Physics model. For the exclusive transitions we study the uncertainties due to the hadronic matrix elements using two set of form factors, finding that in many cases such uncertainties are small. In particular, we show that the $τ^-$ polarization asymmetries become free of hadronic uncertainties if Large Energy relations for the form factors, valid for low momentum transfer to the lepton pair, are used. We also consider $K^*$ helicity fractions and their sensitivity to the compactification parameter.

hep-ph↗
arXiv2006

New open and hidden charm spectroscopy

Many new results on open and hidden charm spectroscopy have been obtained recently. We present a short review of the experimental findings in the meson sector, of the theoretical interpretations and of the open problems, with a discussion on the possibility that some mesons are not quark-antiquark states.

hep-ph↗
arXiv2006

Exclusive $B \to K^{(*)} \ell^+ \ell^-$, $B \to K^{(*)} ν{\bar ν}$ and $B \to K^* γ$ transitions in a scenario with a single Universal Extra Dimension

We analyze the exclusive rare $B \to K^{(*)} \ell^+ \ell^-$, $B \to K^{(*)} ν\bar ν$ and $B \to K^* γ$ decays in the Applequist-Cheng-Dobrescu model, which is an extension of the Standard Model in presence of universal extra dimensions. In particular, we consider the case of a single universal extra dimension. We study how spectra, branching fractions and asymmetries depend on the compactification parameter 1/R, and whether the hadronic uncertainty due to the form factors obscures or not such a dependence. We find that, using present data, it is possible in many cases to put a sensible lower bound to 1/R, the most stringent one coming from $B \to K^* γ$. We also study how improved experimental data can be used to establish stronger constraints to this model.

hep-ph↗
arXiv2005

On the structure of $D_{sJ}^*(2317)$ and $D_{sJ}(2460)$

We discuss the structure of the narrow mesons with charm and strangeness $D_{sJ}^*(2317)$ and $D_{sJ}(2460)$, stressing the role of the radiative decay modes in shedding light on the quark content of these states. We argue that present experimental data favour the interpretation of the two states as ordinary $\bar c s$ mesons. We suggest the existence of resonances with similar properties and well predicted masses in the $\bar b s$ sector.

hep-ph↗
arXiv2005

Light-cone sum rules: A SCET-based formulation

We describe the construction of light-cone sum rules (LCSRs) for exclusive $B$-meson decays into light energetic hadrons from correlation functions within soft-collinear effective theory (SCET). As an example, we consider the SCET sum rule for the $B \to π$ transition form factor at large recoil, including radiative corrections from hard-collinear loop diagrams at first order in the strong coupling constant.

hep-ph↗
arXiv2005

Radiative transitions of $D^*_{sJ}(2317)$ and $D_{sJ}(2460)$

We study radiative decays of $D^*_{sJ}(2317)$ and $D_{sJ}(2460)$ using light-cone QCD sum rules. In particular, we consider the decay modes $D^*_{sJ}(2317)\to D_s^* γ$ and $D_{sJ}(2460)\to D_s^{(*)} γ, D^*_{sJ}(2317) γ$ and evaluate the hadronic parameters in the transition amplitudes analyzing correlation functions of scalar, pseudoscalar, vector and axial-vector quark currents. In the case of $D^*_{sJ}(2317)\to D_s^* γ$ we also consider determinations based on two different correlation functions in HQET. The decay widths turn out to be different than previous estimates obtained by other methods; the results favour the interpretation of $D^*_{sJ}(2317)$ and $D_{sJ}(2460)$ as ordinary $\bar c s$ mesons.

hep-ph↗
arXiv2004

Understanding $D_{sJ}^*(2317)$, $D_{sJ}(2460)$

I briefly review the experimental observations concerning the charmed mesons $D_{sJ}^*(2317)$, $D_{sJ}(2460)$ and survey on some of the interpretations proposed in order to understand their nature. I present an analysis of their decay modes in the hypothesis that they can be identified with the scalar and axial vector $s_\ell^P={1 \over 2}^+$ states of $c{\bar s}$ spectrum ($D_{s0}^*$, $D_{s1}^\prime$). The method is based on heavy quark symmetries and Vector Meson Dominance ansatz. Comparison with present data supports the interpretation.

hep-ph↗
arXiv2004

Excited Charmed Mesons: Observations, Analyses and Puzzles

We review the status of recently observed positive parity charmed resonances, both in the non-strange and in the strange sector. We describe the experimental findings, the main theoretical analyses and the open problems deserving further investigations.

hep-ph↗