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Alessandro Papa

Publications and source records attributed to Alessandro Papa.

At least 109 records · Page 6Linked to original sources
arXiv2013

Flux tubes and coherence length in the SU(3) vacuum

An estimate of the London penetration and coherence lengths in the vacuum of the SU(3) pure gauge theory is given downstream an analysis of the transverse profile of the chromoelectric flux tubes. Within ordinary superconductivity, a simple variational model for the magnitude of the normalized order parameter of an isolated vortex produces an analytic expression for magnetic field and supercurrent density. In the picture of SU(3) vacuum as dual superconductor, this expression provides us with the function that fits the chromoelectric field data. The smearing procedure is used in order to reduce noise.

hep-lat↗
arXiv2013

Critical properties of 3D Z(N) lattice gauge theories at finite temperature

The phase structure of three-dimensional Z(N>4) lattice gauge theories at finite temperature is investigated. Using the dual formulation of the models and a cluster algorithm we locate the critical points of the two transitions, determine various critical indices and compute average action and specific heat. Results are consistent with two transitions of infinite order, belonging to the universality class of two-dimensional Z(N) vector spin models.

hep-lat↗
arXiv2013

Mueller-Navelet small-cone jets at LHC in next-to-leading BFKL

We consider within QCD collinear factorization the process $p+p\to {\rm jet} +{\rm jet} +X$, where two forward high-$p_T$ jets are produced with a large separation in rapidity $Δy$ (Mueller-Navelet jets). In this case the (calculable) hard part of the reaction receives large higher-order corrections $\sim α^n_s (Δy)^n$, which can be accounted for in the BFKL approach with next-to-leading logarithmic accuracy, including contributions $\sim α^n_s (Δy)^{n-1}$. We calculate several observables related with this process, using the next-to-leading order jet vertices, recently calculated in the approximation of small aperture of the jet cone in the pseudorapidity-azimuthal angle plane.

hep-ph↗
arXiv2012

Inclusive production of a pair of identified, rapidity-separated hadrons in proton collisions

We consider the inclusive process where a pair of identified hadrons having large transverse momenta is produced in high-energy proton-proton collisions. We concentrate on the kinematics where the two identified hadrons in the final state are separated by a large interval of rapidity. In this case the cross section receives large higher-order corrections, which can be resummed in the BFKL approach. We provide a theoretical input for the resummation of such contributions with next-to-leading logarithmic accuracy. This process has much in common with the widely discussed Mueller-Navelet jets production and can be also used to access the BFKL dynamics at proton colliders.

hep-ph↗
arXiv2012

NLO forward jet vertex

We calculate in the BFKL approach the jet vertex relevant for the production of Mueller-Navelet jets in proton-proton collisions. We consider both cases of incoming quark and gluon and show explicitly that all infrared divergences cancel when renormalized parton densities are considered. Finally we compare our expression for the vertex with a previous calculation [1].

hep-ph↗
arXiv2012

Chromoelectric flux tubes and coherence length in QCD

The transverse profile of the chromoelectric flux tubes in SU(2) and SU(3) pure gauge theories is analyzed by a simple variational ansatz using a strict analogy with ordinary superconductivity. Our method allows to extract the penetration length and the coherence length of the flux tube.

hep-lat↗
arXiv2012

The jet vertex for Mueller-Navelet and forward jet production

We calculate in next-to-leading order BFKL the jet vertex relevant for the production of Mueller-Navelet jets in proton collisions and of forward jets in deep inelastic scattering. Starting from the definition of the totally inclusive quark and gluon impact factors in the BFKL approach and suitably considering the parton densities and the jet selection functions, we show that an infrared-free result can be found for the jet vertex. Finally we compare our expression for the vertex with the previous calculation of Refs. 1.

hep-ph↗
arXiv2012

Inclusive production of a pair of hadrons separated by a large interval of rapidity in proton collisions

We consider within QCD collinear factorization the inclusive process $p+p\to h_1+h_2+X$, where the pair of identified hadrons, $h_1,h_2$, having large transverse momenta is produced in high-energy proton-proton collisions. In particular, we concentrate on the kinematics where the two identified hadrons in the final state are separated by a large interval of rapidity $Δy$. In this case the (calculable) hard part of the reaction receives large higher order corrections $\sim α^n_s Δy^n$. We provide a theoretical input for the resummation of such contributions with next-to-leading logarithmic accuracy (NLA) in the BFKL approach. Specifically, we calculate in NLA the vertex (impact-factor) for the inclusive production of the identified hadron. This process has much in common with the widely discussed Mueller-Navelet jets production and can be also used to access the BFKL dynamics at proton colliders. Another application of the obtained identified-hadron vertex could be the NLA BFKL description of inclusive forward hadron production in DIS.

hep-ph↗
arXiv2012

Chiral Symmetry Breaking in Planar QED in External Magnetic Fields

We investigate planar quantum electrodynamics (QED) with two degenerate staggered fermions in an external magnetic field on the lattice. We argue that in external magnetic fields there is dynamical generation of mass for two-dimensional massless Dirac fermions in the weak-coupling region. We extrapolate our lattice results to the quantum Hall effect in graphene.

hep-lat↗
arXiv2012

The next-to-leading order forward jet vertex in the small-cone approximation

We consider within QCD collinear factorization the process p+p to jet + jet +X, where two forward high-$p_T$ jets are produced with a large separation in rapidity $Δy$ (Mueller-Navelet jets). In this case the (calculable) hard part of the reaction receives large higher-order corrections $\sim α^n_s (Δy)^n$, which can be accounted for in the BFKL approach. In particular, we calculate in the next-to-leading order the impact factor (vertex) for the production of a forward high-$p_T$ jet, in the approximation of small aperture of the jet cone in the pseudorapidity-azimuthal angle plane. The final expression for the vertex turns out to be simple and easy to implement in numerical calculations.

hep-ph↗
arXiv2011

Critical properties of 2D Z(N) vector models for N>4

We investigate the critical properties of two-dimensional Z(N) vector models for N larger than 4. In particular, critical points of the two phase transitions are located and some critical indices are determined. We study also the behavior of the helicity modulus and the dependence of the critical points on N.

hep-lat↗
arXiv2011

Hard inclusive production of a pair of rapidity-separated hadrons in proton collisions

We discuss the process $p+p\to h_1+h_2+X$, where the identified hadrons $h_1$ and $h_2$ have large transverse momenta and are produced in high-energy proton-proton collisions with a large rapidity gap between them. In this case the (calculable) hard part of the reaction receives large higher order corrections $\sim α^n_s\ln^n Δy$, which can be accounted for in the BFKL approach. Specifically, we describe in the next-to-leading order the calculation of the vertex (impact-factor) for the inclusive production of the identified hadron.

hep-ph↗
arXiv2011

Flux tubes in the SU(3) vacuum

We analyze the distribution of the chromoelectric field generated by a static quark-antiquark pair in the SU(3) vacuum. We find that the transverse profile of the flux tube resembles the dual version of the Abrikosov vortex field distribution and give an estimate of the London penetration length in the confined vacuum.

hep-lat↗
arXiv2011

Lattice Planar QED in external magnetic field

We investigate planar Quantum ElectroDynamics (QED) with two degenerate staggered fermions in an external magnetic field on the lattice. Our preliminary results indicate that in external magnetic fields there is dynamical generation of mass for two-dimensional massless Dirac fermions in the weak coupling region. We comment on possible implications to the quantum Hall effect in graphene.

hep-lat↗
arXiv2011

Numerical study of the phase transitions in the two-dimensional Z(5) vector model

We investigate the critical properties of the two-dimensional Z(5) vector model. For this purpose, we propose a new cluster algorithm, valid for Z(N) models with odd values of N. The two-dimensional Z(5) vector model is conjectured to exhibit two phase transitions with a massless intermediate phase. We locate the position of the critical points and study the critical behavior across both phase transitions in details. In particular, we determine various critical indices and compare the results with analytical predictions.

hep-lat↗
arXiv2011

Critical properties of the 2D Z(5) vector model

The two-dimensional Z(5) vector model is investigated through the determination of critical points and one critical index. To this purpose a new cluster algorithm has been developed valid for 2D Z(N) models with odd values of N. Results are compared with analytical predictions.

hep-lat↗
arXiv2010

Critical behaviour of the compact 3d U(1) gauge theory at finite temperature

Critical properties of the compact three-dimensional U(1) lattice gauge theory are explored at finite temperatures. The critical point of the deconfinement phase transition, critical indices and the string tension are studied numerically on lattices with temporal extension N_t = 8 and spatial extension ranging from L = 32 to L = 256. The critical indices, which govern the behaviour across the deconfinement phase transition, are generally expected to coincide with the critical indices of the two-dimensional XY model. It is found that the determination of the infinite volume critical point differs from the pseudo-critical coupling at L = 32, found earlier in the literature and implicitly assumed as the onset value of the deconfined phase. The critical index $ν$ computed from the scaling of the pseudocritical couplings agrees well with the value $ν$ = 1/2 of the XY model. The computation of the index $η$ brings to a value larger than expected. The possible reasons for such behaviour are discussed.

hep-lat↗