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E. Di Salvo

Publications and source records attributed to E. Di Salvo.

At least 19 recordsLinked to original sources
arXiv2025

Hydrodynamics in generalized electronic two-band systems

In this paper, we derive the Euler and Navier-Stokes equations for electronic two-band systems in arbitrary dimension and with generic power-law dispersion relations. We focus on the hydrodynamic transport regime, where such systems offer a unique tunability between a Fermi-liquid type regime at high doping and the inherent two-band physics of the low-density system close to the Dirac-type band-touching point. For a generic dispersion, the absence of Euclidean or Lorentzian invariance leads to novel types of hydrodynamic equations. We characterize these novel hydrodynamic regimes through dimensionless numbers, such as the Prandtl and Lorenz numbers, or the ratio between shear viscosity and entropy density. In all cases, we provide a derivation of the physics of the long-wavelength plasmonic modes.

cond-mat.str-el↗
arXiv2024

Topological phases of the interacting Su-Schrieffer-Heeger model: An analytical study

The interacting SSH model provides an ideal ground to study the interplay between topologically insulating phases and electron-electron interactions. We study the polarization density as a topological invariant and provide an analytic treatment of its behavior in the low-energy sector of the one-dimensional interacting SSH model. By formulating the topological invariant in terms of Green's functions, we use the low-energy field theory of the Thirring model to derive the behavior of the polarization density. We show that the polarization density in the continuum theory describes the usual topological insulating phases. Still, it contains an extra factor from the fields' scaling dimensions in the low-energy quantum field theory. We interpret this as a measure of the modified charge of the new excitations in the system. We find two distinct contributions: a renormalization of the electronic charge $e$ of a Fermi liquid because of quasiparticle smearing and an additional contribution coming from the topological charge of the soliton arising in the bosonized version of the Thirring model, the sine-Gordon model.

cond-mat.str-el↗
arXiv2023

Searching for New Physics in the Differential Decay Width of a Lambda_b Semi-leptonic Decay

We propose to investigate the effects of new physics in the semi-leptonic sequential decay $Λ_b \to Λ_c (\to Λπ) τ{\bar ν}_τ$. Firstly, we write the general, model independent, non-covariant expression of the differential decay width of the process. Then, we calculate that observable according to three different types of new physics interactions, which might explain the tension of data with the standard model predictions. We find that some coefficients of the differential decay width are sensitive to the kind of interaction that is assumed. The measurements that we suggest seem to be feasible.

hep-ph↗
arXiv2019

Polarization in (quasi-)two-body decays and new physics

We consider two-body and quasi-two-body decays of the type $f_1 \to f_2 B$, where $f_1$ and $f_2$ are spin-1/2 fermions and $B$ a spin-0 or spin-1 boson. After recalling the non-covariant formalism for decay amplitudes, we derive the expression of the differential decay width and of the polarizations of the final spinning particles, both on- and off-shell. We find an intriguing geometrical interpretation of the results about the polarization. We also illustrate some methods for measuring the polarizations of the resonances and for optimizing data analysis. Then we propose applications to semi-leptonic weak decays, with a major attention to the $T$-odd component of the polarization; this may help to find, simultaneously, possible time-reversal violations and hints to physics beyond the standard model. We suggest also a $CPT$ test. Last, we discuss some $T$-odd observables for the production process of $f_1$ and for the study of the strong final state interactions of non-leptonic decays.

hep-ph↗
arXiv2018

Detailed Study of the Decay Lambda_b --> Lambda_c tau {\bar ν}_τ

We examine in detail the semi-leptonic decay $Λ_b \to Λ_c τ{\bar ν}_τ$, which may confirm previous hints, from the analogous $B$ decay, of a new physics beyond the standard model. First of all, starting from rather general assumptions, we predict the partial width of the decay. Then we analyze the effects of five possible new physics interactions, adopting in each case five different form factors. In particular, for each term beyond the standard model, we find some constraints on the strength and phase of the coupling, which we combine with those found by other authors in analyzing the analogous semi-leptonic decays of $B$. Our analysis involves some dimensionless quantities, substantially independent of the form factor, but which, owing to the constraints, turn out to be strongly sensitive to the kind of non-standard interaction. We also introduce a criterion thanks to which one can discriminate among the various new physics terms: the left-handed current and the two-higgs-doublet model appear privileged, with a neat preference for the former interaction. Lastly, we suggest a differential observable that could, in principle, help to distinguish between the two cases.

hep-ph↗
arXiv2013

Asymmetries in Three-Body Decays of the B-Meson

We suggest to analyze the three-body decays B+- to $K+- p pbar$ and to $K+- ππ$ by means of two different asymmetries. The former asymmetry, a T-odd one, vanishes and is proposed as a test for excluding biases in the experimental data. The latter asymmetry, which is T-even, may be useful in singling out time reversal odd contributions to the decay, and, possibly, hints at physics beyond the standard model.

hep-ph↗
arXiv2012

Interference Effects, Time Reversal Violation and Search for New Physics in Hadronic Weak Decays

We propose some methods for studying hadronic sequential two-body decays involving more spinning particles. It relies on the analysis of T-odd and T-even asymmetries, which are related to interference terms. The latter asymmetries turn out to be as useful as the former ones in inferring time reversal violating observables; these in turn may be sensitive, under some particular conditions, to possible contributions beyond the standard model. Our main result is that one can extract such observables even after integrating the differential decay width over almost all of the available angles. Moreover we find that the correlations based exclusively on momenta are quite general, since they provide as much information as those involving one or more spins. We generalize some methods already proposed in the literature for particular decay channels, but we also pick out a new kind of time reversal violating observables. Our analysis could be applied, for example, to data of LHCb experiment.

hep-ph↗
arXiv2012

Deep Inelastic Processes and the Equations of Motion

We show that the Politzer theorem on the equations of motion implies approximate constraints on the quark correlator, restricting considerably, for sufficiently large Q^2, the number of independent distribution functions that characterize the internal structure of the nucleon, and of independent fragmentation functions. This result leads us to suggesting an alternative method for determining transversity. Moreover our approach implies predictions on the Q^2-dependence of some azimuthal asymmetries, like Sivers, Qiu-Sterman and Collins asymmetry. Lastly, we discuss some implications on the Burkhardt-Cottingham and Efremov-Leader-Teryaev sum rules.

hep-ph↗
arXiv2008

Model Independent Tests for Time Reversal and CP Violations and for CPT Theorem in Λ_b and \barΛ_b Two Body Decays

Weak decays of beauty baryons like Λ_b (\barΛ_b) into Λ(\barΛ) and V (J^P = 1^-), where both decay products are polarized, offer interesting opportunities to perform tests of time reversal and CP violations and of CPT invariance. We propose a model independent parametrization of the angular distribution and of the polarization of the final resonances, by means of the spin density matrix. The transverse component of the polarization is sensitive to time reversal violations, moreover CP-and CPT-sensitive observables are defined.

hep-ph↗
arXiv2007

Testing Time-Reversal: Lambda_b Decays into Polarized Resonances

Weak decays of beauty baryons like Lambda_b into Lambda V(J^P=1^-), where the produced resonances are polarized, offer interesting opportunity to perform tests of Time-Reversal Invariance. This paper emphasizes the particular role of the resonance polarization-vectors and their physical properties by symmetry transformations. In particular, it is shown that the normal component of a polarization-vector, as defined in the Jackson's frame, is Lorentz invariant and could get large values, notably in the case of J/psi production.

hep-ph↗
arXiv2005

The Quark-Quark Correlator: Theory and Phenomenology

New properties of the quark correlator are found via equations of motion. As a first result, approximate relations can be established among the "soft" functions; one such relation may help in determining the quark transversity in a nucleon. Secondly, the Q^2 dependence of the T-odd functions is deduced; the result is compared to unpolarized Drell-Yan data. Lastly, important remarks are made about the contributions to g_2(x).

hep-ph↗
arXiv2004

Q^2 Dependence of the azimuthal Asymmetry in Unpolarized Drell-Yan

We study the azimuthal asymmetry of the unpolarized Drell-Yan in the framework of the T-odd functions. We find, on the basis of quite general arguments, that for |{\bf q}_{\perp}| << Q such an asymmetry decreases as Q^{-2}, where {\bf q}_{\perp} and Q are respectively the transverse momentum and the center-of-mass energy of the muon pair. The experimental results support this conclusion.

hep-ph↗
arXiv2003

A rigorous bound on quark distributions in the nucleon

I deduce an inequality between the helicity and the transversity distribution of a quark in a nucleon, at small energy scales. Then I establish, thanks to the positivity constraint, a rigorous bound on longitudinally polarized valence quark densities, which finds nontrivial applications to d-quarks. This, in turn, implies a bound for the distributions of the longitudinally polarized sea, which is probably not SU(3)-symmetric. Some model predictions and parametrizations of quark distributions are examined in the light of these results.

hep-ph↗
arXiv2002

Role of T-odd functions in high energy hadronic collisions

I propose a simple model for predicting the enegy behavior of T-odd, chiral odd function $h_1^{\perp}$. Furthermore I illustrate a method for extracting $h_1^{\perp}$ and the transversity function from Drell-Yan. The method may be applied also to other reactions.

hep-ph↗
arXiv2002

Transverse momentum, factorization and the HERMES experiment

I present some results about transverse momentum dependent distribution and fragmentation functions. Firstly I illustrate a simple model, with predictive power about the energy behavior, for T-odd, chiral odd functions. Moreover I propose a slight modification in extracting transversity from HERMES data, so as to apply correctly factorization. Lastly I suggest a method for determining the quark transverse polarization in an unpolarized or spinless hadron.

hep-ph↗
arXiv2002

The transversity function and double spin asymmetry in semi-inclusive DIS

We show that the spin asymmetry in semi-inclusive deep inelastic scattering between a longitudinally polarized lepton beam and a transversely polarized proton target is sensitive to the proton transversity function. The asymmetry, which is twist 3, is estimated to be more than 10% under the most favourable conditions. The experiment we suggest is feasible at facilities like DESY, CERN and JLAB.

hep-ph↗
arXiv1998

Perspectives for Direct CP Violation Tests in Hyperon Decays

We discuss the perspectives of measuring direct CP violation parameters in hyperon decays by measurements with proton and/or antiproton beams, to be carried out at various facilities, and in particular we propose new experiments at the Tevatron and at the LHC.

hep-ph↗