arXiv subjects

P. Santorelli

Publications and source records attributed to P. Santorelli.

31 records · Page 2Linked to original sources

arXiv1998

Quarks and Gluons in Nucleon Polarized Structure Functions

We study the available data in polarized e-p deep inelastic scattering to test two different solutions to the so called spin crisis: one of them based on the axial gluon anomaly and consistent with the Bjorken sum rule and another one, where the defects in the spin sum rules and in the Gottfried sum rule are related. In this case a defect is also expected for the Bjorken sum rule. Experimental data, especially the very recent SLAC E154, favour the first solution and demand a gluon polarization $ΔG = 2.25 \pm 1.39$.

hep-ph↗

arXiv1998

Polarized Quarks, Gluons and Sea in Nucleon Structure Functions

We perform a NLO analysis of polarized deep inelastic scattering data to test two different solutions to the so called spin crisis: one of them based on the axial gluon anomaly and consistent with the Bjorken sum rule and another one, where the defects in the spin sum rules and in the Gottfried sum rule are related. In this case a defect is also expected for the Bjorken sum rule. The first solution is slightly favoured by the SLAC E154 results, but both options seem to be consistent with the CERN SMC data.

hep-ph↗

arXiv1998

A Positive Test for Fermi-Dirac Distributions of Quark-Partons

By describing a large class of deep inelastic processes with standard parameterization for the different parton species, we check the characteristic relationship dictated by Pauli principle: broader shapes for higher first moments. Indeed, the ratios between the second and the first moment and the one between the third and the second moment for the valence partons is an increasing function of the first moment and agrees quantitatively with the values found with Fermi-Dirac distributions.

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arXiv1997

Rare B \to K^{(*)} ν\barνDecays at B Factories

We compute the branching fraction of the decays $B \to K ν\barν$ and $B \to K^* ν\barν$ in the Standard Model. We also comment on the experimental difficulties and procedures to detect such modes at B factories.

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arXiv1997

Low x Behaviour of the Isovector Nucleon Polarized Structure Function and the Bjorken Sum Rule

The combination g_1^p(x) - g_1^n(x) is derived from SLAC data on polarized proton and deuteron targets, evaluated at Q^2 = 10 GeV^2, and compared with the results of SMC experiment. The agreement is satisfactory except for the points at the three lowest x, which have an important role in the SMC evaluation of the l.h.s. of the Bjorken sum rule.

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arXiv1996

Statistical Inspired Parton Distributions and the Violation of QPM Sum Rules

A quantum statistical parametrization of parton distributions has been considered. In this framework, the exclusion Pauli principle connects the violation of the Gottfried sum rule with the Ellis and Jaffe one, and implies a defect in the Bjorken sum rule. However, in terms of standard parametrizations of the polarized distributions a good description of the data is obtained once a large gluon polarization is provided. Interestingly, in this description there is no violation of the Bjorken sum rule.

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arXiv1996

QCD Sum Rule Analysis of the Decays $B \to K \ell^+ \ell^-$ and $B \to K^* \ell^+ \ell^-$

We use QCD sum rules to calculate the hadronic matrix elements governing the rare decays $B \to K \ell^+ \ell^-$ and $B \to K^* \ell^+ \ell^-$ induced by the flavour changing neutral current $b \to s$ transition. We also study relations among semileptonic and rare $B \to K^{(*)}$ decay form factors. The analysis of the invariant mass distribution of the lepton pair in $B \to K^{(*)} \ell^+ \ell^-$ and of the angular asymmetry in $B \to K^* \ell^+ \ell^-$ provides us with interesting tests of the Standard Model and its extensions.

hep-ph↗

arXiv1995

Does One Need the Anomaly to Describe the Polarized Structure Functions?

The SLAC data on the p, d and n polarized structure functions are fairly well reproduced with and without the contribution of the anomaly. The results are compared with a previous study based mainly on SMC data. The implications on the solution of the spin-crisis are discussed.

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arXiv1994

Nonleptonic weak decays of charmed mesons

A previous analysis of two-body Cabibbo allowed nonleptonic decays of $D^0$ mesons and of Cabibbo allowed and first-forbidden decays of $D^+$ and $D_s^+$ has been adjourned using more recent experimental data and extended to the Cabibbo forbidden decays of $D^0$. Annihilation and W-exchange contributions as well as final state interaction effects (assumed to be dominated by nearby resonances) have been included and are in fact crucial to obtain a reasonable agreement with the experimental data, which show large flavour SU(3) violations. New fitting parameters are necessary to describe rescattering effects for Cabibbo forbidden $D^0$ decays, given the lack of experimental informations on isoscalar resonances. We keep their number to a minimum - three - using phenomenologically based considerations. We also discuss CP violating asymmetries.

hep-ph↗

arXiv1994

Form Factor $A_0(q^2)$, Non Leptonic $D(B) \to PV$ Transitions and Rare $B \to K^* γ$ Decays

We use three-point function QCD sum rules to calculate the form factor $A_0(q^2)$ appearing in the matrix element of the flavour-changing axial current between the $D (B)$ state and a vector meson state. We describe the role of this form factor in nonleptonic $D (B) \to P V$ decays and analyze the light $SU(3)_F$ symmetry breaking effects. We also discuss a proposal to relate the branching ratio of $B \to K^* γ$ to the spectrum of the semileptonic $B \to ρ\ell ν$ decay.

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arXiv1993

Dependence of the Form Factors of $B \to π\ell ν$ on the Heavy Quark Mass

We use QCD sum rules to analyze the semileptonic transition $B \to π\ell ν$ in the limit $m_b \to \infty$. We derive the dependence of the form factor $F_1(0)$ on the heavy quark mass, which is compatible with the expected dependence for the simple pole model of $F_1(q^2)$.

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arXiv1993

Nonleptonic Cabibbo Favoured $B$-Decays and $CP$-Asymmetries for Charmed Final Hadron States in Isgur and Wise Theory

The Cabibbo allowed non-leptonic $B$-decays in two hadrons are studied, within the factorization hypothesis, in the framework of Isgur and Wise theory for the matrix elements of the $ΔB=-ΔC=\pm 1$ weak currents. The $SU(2)_{HF}$ symmetry relates $|ΔB|=1$ to $|ΔC|=1$ currents, which have been measured in the semileptonic strange decays of charmed particles. By assuming colour screening and allowing for $SU(3)$ invariant contributions from the annihilation terms with charmed final states one is able to comply with the present experimental knowledge.\\ The $CP$ violating asymmetries in neutral $B$ decays are given for charmed final states in terms of the $K-M$ angles. With the central values found for the annihilation parameters there is a destructive (constructive) interference between the direct and annihilation terms in the Cabibbo allowed (doubly forbidden) amplitudes for the decays into $D^{0}(D^{*0})π^0$ and $D^0ρ^0$ so that they may be of the same order. This would imply large asymmetries, for which however our present knowledge on the amplitudes does not allow to predict even their sign.\\ We have better confidence in our predictions for the charged final states than the neutral ones and can draw the conclusion that the detection of the corresponding asymmetries requires, at least, $10^6$ tagged neutral $B$-particles.

hep-ph↗

arXiv1992

CP violating asymmetries in charged D meson decays

The CP violating asymmetries for Cabibbo suppressed charged D meson decays in the standard model are estimated in the factorized approximation, using the two-loop effective hamiltonian and a model for final state interactions previously tested for Cabibbo allowed D decays. No new parameters are added. The predictions are larger than expected and not too far from the experimental possibilities.

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