Pedro Bicudo - Academia.edu (original) (raw)

Papers by Pedro Bicudo

arXiv (Cornell University), Dec 13, 2014

We discuss a method to extract the Källén-Lehmann spectral density of a particle (be it elementar... more We discuss a method to extract the Källén-Lehmann spectral density of a particle (be it elementary or bound state) propagator and apply it to compute gluon spectral densities from lattice data. Furthermore, we also consider the interpretation of the Landau-gauge gluon propagator at finite temperature as a massive-type bosonic propagator.

arXiv (Cornell University), Oct 30, 2012

We discuss how the steepest descent method with Fourier acceleration for Laudau gauge fixing in l... more We discuss how the steepest descent method with Fourier acceleration for Laudau gauge fixing in lattice SU(3) simulations can be implemented using CUDA. The scaling of the gauge fixing code was investigated using a Tesla C2070 Fermi architecture, and compared with a parallel CPU gauge fixing code.

slft, 2011

The colour fields created by the static tetraquark and pentaquark systems are computed in quenche... more The colour fields created by the static tetraquark and pentaquark systems are computed in quenched SU(3) lattice QCD, with gauge invariant lattice operators, in a 24 3 ×48 lattice at β = 6.2. We generate our quenched configurations with GPUs, and detail the respective benchmanrks in different SU(N) groups. While at smaller distances the coulomb potential is expected to dominate, at larger distances it is expected that fundamental flux tubes, similar to the flux-tube between a quark and an antiquark, emerge and confine the quarks. In order to minimize the potential the fundamental flux tubes should connect at 120o angles. We compute the square of the colour fields utilizing plaquettes, and locate the static sources with generalized Wilson loops and with APE smearing. The tetraquark system is well described by a double-Y-shaped flux-tube, with two Steiner points, but when quark-antiquark pairs are close enough the two junctions collapse and we have an X-shaped flux-tube, with one Steiner point. The pentaquark system is well described by a three-Y-shaped flux-tube where the three flux the junctions are Steiner points.

Physical review, Jun 12, 2023

arXiv (Cornell University), Mar 27, 2023

Proceedings of The 39th International Symposium on Lattice Field Theory — PoS(LATTICE2022), Nov 14, 2022

We investigate = 0 bottomonium bound states and resonances in S, P, D and F waves using lattice Q... more We investigate = 0 bottomonium bound states and resonances in S, P, D and F waves using lattice QCD static-static-light-light potentials. We consider five coupled channels, one confined quarkonium and four open (*)¯(*) and (*)¯(*) meson-meson channels and use the Born-Oppenheimer approximation and the emergent wave method to compute poles of the T matrix. We discuss results for masses and decay widths and compare them to existing experimental results. Moreover, we determine the quarkonium and meson-meson composition of these states to clarify, whether they are ordinary quarkonium or should rather be interpreted as tetraquarks.

arXiv (Cornell University), Aug 27, 2016

We show the flux tubes produced by static quark-antiquark, quark-quark and quark-gluon charges at... more We show the flux tubes produced by static quark-antiquark, quark-quark and quark-gluon charges at finite temperature. The sources are placed in the lattice with fundamental and adjoint Polyakov loops. We compute the square densities of the chromomagnetic and chromoelectric fields above and below the phase transition. Our results are gauge invariant and produced in pure gauge SU(3). The codes are written in CUDA and the computations are performed with GPUs.

arXiv (Cornell University), Sep 22, 2015

Covariant R ξ gauge fixing is notoriously difficult for large lattice volumes, large ξ and small ... more Covariant R ξ gauge fixing is notoriously difficult for large lattice volumes, large ξ and small N c. We thoroughly test different convergence techniques, which allows the gauge fixing of lattice configurations with a total volume of (3.25 fm) 4 , up to ξ = 0.5. We are able to study the gluon propagator in the infrared region and its dependence on the gauge fixing parameter ξ. As expected, the longitudinal gluon dressing functions stay constant at their tree-level value ξ. Similar to the Landau gauge, the transverse R ξ gauge gluon propagators saturate at a non-vanishing value in the deep infrared for all values of ξ studied. We compare with very recent continuum studies and perform a simple analysis of the found saturation with a dynamically generated effective gluon mass.

arXiv (Cornell University), Oct 10, 2010

The interpretation of the Landau gauge lattice gluon propagator as a massive type bosonic propaga... more The interpretation of the Landau gauge lattice gluon propagator as a massive type bosonic propagator is investigated for i) an infrared constant gluon mass; ii) an ultraviolet constant gluon mass; iii) a momentum dependent mass. We find that the infrared data can be associated with a massive propagator with a constant gluon mass of 651(12) MeV, but the ultraviolet lattice data is not compatible this type of propagator. The scenario of a momentum dependent gluon mass gives a decreasing mass with the momentum, starting from a value of ∼ 630 MeV in the infrared region and suggesting a q 2 ln q 2 dependence for momenta above 1 GeV.

Physical review, Oct 24, 2017

We revisit the static potential for the QQQQ system using SU(3) lattice simulations, studying bot... more We revisit the static potential for the QQQQ system using SU(3) lattice simulations, studying both the colour singlets groundstate and first excited state. We consider geometries where the two static quarks and the two anti-quarks are at the corners of rectangles of different sizes. We analyse the transition between a tetraquark system and a two meson system with a two by two correlator matrix. We compare the potentials computed with quenched QCD and with dynamical quarks. We also compare our simulations with the results of previous studies and analyze quantitatively fits of our results with anzatse inspired in the string flip-flop model and in its possible colour excitations.

arXiv (Cornell University), Oct 21, 2013

We address the interpretation of the Landau gauge gluon propagator at finite temperature as a mas... more We address the interpretation of the Landau gauge gluon propagator at finite temperature as a massive type bosonic propagator. Using pure gauge SU(3) lattice simulations at a fixed lattice volume ∼ (6.5f m) 3 , we compute the electric and magnetic form factors, extract a gluon mass from Yukawa-like fits, and study its temperature dependence. This is relevant both for the Debye screening at high temperature T and for confinement at low T .

arXiv (Cornell University), Jan 7, 2014

arXiv (Cornell University), Oct 7, 2010

We discuss the CUDA approach to the simulation of pure gauge Lattice SU(2). CUDA is a hardware an... more We discuss the CUDA approach to the simulation of pure gauge Lattice SU(2). CUDA is a hardware and software architecture developed by NVIDIA for computing on the GPU. We present an analysis and performance comparison between the GPU and CPU with single precision. Analysis with single and multiple GPU's, using CUDA and OPENMP, are also presented. In order to obtain a high performance, the code must be optimized for the GPU architecture, i.e., an implementation that exploits the memory hierarchy of the CUDA programming model. Using GPU texture memory and minimizing the data transfers between CPU and GPU, we achieve a speedup of 200× using 2 NVIDIA 295 GTX cards relative to a serial CPU, which demonstrates that GPU's can serve as an efficient platform for scientific computing. With multi-GPU's we are able, in one day computation, to generate 1 000 000 gauge configurations in a 48 4 lattice with β = 6.0 and calculate the mean average plaquette. We present results for the mean average plaquette in several lattice sizes for different β. Finally we present results for the mean average Polyakov loop at finite temperature.

arXiv (Cornell University), Oct 5, 2010

The colour fields, created by a static gluon-quark-antiquark system, are computed in quenched SU(... more The colour fields, created by a static gluon-quark-antiquark system, are computed in quenched SU(3) lattice QCD, in a 24 3 × 48 lattice at β = 6.2 and a = 0.07261(85) f m. We study two geometries, one with a U shape and another with an L shape. The particular cases of the two gluon glueball and quark-antiquark are also studied, and the Casimir scaling is investigated in a microscopic perspective. This also contributes to understand confinement with flux tubes and to discriminate between the models of fundamental versus adjoint confining strings, analogous to type-II and type-I superconductivity.

Proceedings of The 38th International Symposium on Lattice Field Theory — PoS(LATTICE2021)

We study = 0 quarkonium resonances decaying into pairs of heavy-light mesons using staticstatic-l... more We study = 0 quarkonium resonances decaying into pairs of heavy-light mesons using staticstatic-light-light potentials from lattice QCD. To this end, we solve a coupled channel Schrödinger equation with a confined quarkonium channel and channels with a heavy-light meson pair to compute phase shifts and T matrix poles for the lightest decay channel. We discuss our results for , , and wave states in the context of corresponding experimental results, in particular for Υ(10753) and Υ(10860).

arXiv (Cornell University), Oct 5, 2010

We develop a formalism to study tetraquarks using the generalized flip-flop potential, which incl... more We develop a formalism to study tetraquarks using the generalized flip-flop potential, which include the tetraquark potential component. Technically this is a difficult problem, needing the solution of the Schrödinger equation in a multidimensional space. Since the tetraquark may at any time escape to a pair of mesons, here we study a simplified twovariable toy model and explore the analogy with a cherry in a glass, but a broken one where the cherry may escape from. We also compute the decay width in this two-variable picture, solving the Schrödinger equation for the outgoing spherical wave.

arXiv (Cornell University), Apr 1, 2010

The colour fields, created by a static gluon-quark-antiquark system, are computed in quenched SU(... more The colour fields, created by a static gluon-quark-antiquark system, are computed in quenched SU(3) lattice QCD, in a 24 3 × 48 lattice at β = 6.2 and a = 0.07261(85) f m. We compute the hybrid Wilson Loop including the cases when the gluon and the antiquark are superposed, i. e., the quark-antiquark case and when the quark and antiquark are superposed, i. e., the gluon-gluon case. The Casimir scaling is investigated, in the two gluon glueball case the Casimir scaling is consistent with the formation of an adjoint string. Measuring the decay of the tail in the mid section of the flux tube for the two gluon glueball and for the quark-antiquark meson, we determine the penetration length and present a gauge invariant effective dual gluon mass of 0.905 ± 0.163 GeV. We also try to determine the coherence length comparing our results with the dual Ginzburg-Landau approach. With the penetration length and the possible coherence length we determine a putative Ginzburg-Landau dimensionless parameter, which is possibly consistent with a type II superconductor picture. These results are obtained at fixed quark-antiquark distance of 0.58 fm.

arXiv (Cornell University), May 27, 2021

Spectra with full towers of levels are expected due to the quantization of the string vibrations,... more Spectra with full towers of levels are expected due to the quantization of the string vibrations, however different theoretical models exist for the excitation spectra. First principle computations are important to test the different models and to search for novel phenomena, but so far only a few excited states of QCD flux tubes have been studied with pure gauge SU(3) lattice QCD in 3+1 dimensions. We thus aim to study a spectrum of flux tubes with static quark and antiquark sources up to a significant number of excitations. We specialize in the most symmetric case, the Sigmag+\Sigma_g^+Sigmag+, where up to two levels are already published in the literature. To achieve the highest possible excitation level, we construct a large set of operators with the correct symmetry, solve the generalized eigenvalue problem and compare the results of different lattice QCD gauge actions with different lattice spacings and anisotropies.

EPJ Web of Conferences, 2018

We present colour field density profiles for some of the first SU(3) gluonic excitations of the f... more We present colour field density profiles for some of the first SU(3) gluonic excitations of the flux tube in the presence of a static quark-antiquark pair. The results are obtained from a large set of gluonic operators.

arXiv (Cornell University), Dec 13, 2014

We discuss a method to extract the Källén-Lehmann spectral density of a particle (be it elementar... more We discuss a method to extract the Källén-Lehmann spectral density of a particle (be it elementary or bound state) propagator and apply it to compute gluon spectral densities from lattice data. Furthermore, we also consider the interpretation of the Landau-gauge gluon propagator at finite temperature as a massive-type bosonic propagator.

arXiv (Cornell University), Oct 30, 2012

We discuss how the steepest descent method with Fourier acceleration for Laudau gauge fixing in l... more We discuss how the steepest descent method with Fourier acceleration for Laudau gauge fixing in lattice SU(3) simulations can be implemented using CUDA. The scaling of the gauge fixing code was investigated using a Tesla C2070 Fermi architecture, and compared with a parallel CPU gauge fixing code.

slft, 2011

The colour fields created by the static tetraquark and pentaquark systems are computed in quenche... more The colour fields created by the static tetraquark and pentaquark systems are computed in quenched SU(3) lattice QCD, with gauge invariant lattice operators, in a 24 3 ×48 lattice at β = 6.2. We generate our quenched configurations with GPUs, and detail the respective benchmanrks in different SU(N) groups. While at smaller distances the coulomb potential is expected to dominate, at larger distances it is expected that fundamental flux tubes, similar to the flux-tube between a quark and an antiquark, emerge and confine the quarks. In order to minimize the potential the fundamental flux tubes should connect at 120o angles. We compute the square of the colour fields utilizing plaquettes, and locate the static sources with generalized Wilson loops and with APE smearing. The tetraquark system is well described by a double-Y-shaped flux-tube, with two Steiner points, but when quark-antiquark pairs are close enough the two junctions collapse and we have an X-shaped flux-tube, with one Steiner point. The pentaquark system is well described by a three-Y-shaped flux-tube where the three flux the junctions are Steiner points.

Physical review, Jun 12, 2023

arXiv (Cornell University), Mar 27, 2023

Proceedings of The 39th International Symposium on Lattice Field Theory — PoS(LATTICE2022), Nov 14, 2022

We investigate = 0 bottomonium bound states and resonances in S, P, D and F waves using lattice Q... more We investigate = 0 bottomonium bound states and resonances in S, P, D and F waves using lattice QCD static-static-light-light potentials. We consider five coupled channels, one confined quarkonium and four open (*)¯(*) and (*)¯(*) meson-meson channels and use the Born-Oppenheimer approximation and the emergent wave method to compute poles of the T matrix. We discuss results for masses and decay widths and compare them to existing experimental results. Moreover, we determine the quarkonium and meson-meson composition of these states to clarify, whether they are ordinary quarkonium or should rather be interpreted as tetraquarks.

arXiv (Cornell University), Aug 27, 2016

We show the flux tubes produced by static quark-antiquark, quark-quark and quark-gluon charges at... more We show the flux tubes produced by static quark-antiquark, quark-quark and quark-gluon charges at finite temperature. The sources are placed in the lattice with fundamental and adjoint Polyakov loops. We compute the square densities of the chromomagnetic and chromoelectric fields above and below the phase transition. Our results are gauge invariant and produced in pure gauge SU(3). The codes are written in CUDA and the computations are performed with GPUs.

arXiv (Cornell University), Sep 22, 2015

Covariant R ξ gauge fixing is notoriously difficult for large lattice volumes, large ξ and small ... more Covariant R ξ gauge fixing is notoriously difficult for large lattice volumes, large ξ and small N c. We thoroughly test different convergence techniques, which allows the gauge fixing of lattice configurations with a total volume of (3.25 fm) 4 , up to ξ = 0.5. We are able to study the gluon propagator in the infrared region and its dependence on the gauge fixing parameter ξ. As expected, the longitudinal gluon dressing functions stay constant at their tree-level value ξ. Similar to the Landau gauge, the transverse R ξ gauge gluon propagators saturate at a non-vanishing value in the deep infrared for all values of ξ studied. We compare with very recent continuum studies and perform a simple analysis of the found saturation with a dynamically generated effective gluon mass.

arXiv (Cornell University), Oct 10, 2010

The interpretation of the Landau gauge lattice gluon propagator as a massive type bosonic propaga... more The interpretation of the Landau gauge lattice gluon propagator as a massive type bosonic propagator is investigated for i) an infrared constant gluon mass; ii) an ultraviolet constant gluon mass; iii) a momentum dependent mass. We find that the infrared data can be associated with a massive propagator with a constant gluon mass of 651(12) MeV, but the ultraviolet lattice data is not compatible this type of propagator. The scenario of a momentum dependent gluon mass gives a decreasing mass with the momentum, starting from a value of ∼ 630 MeV in the infrared region and suggesting a q 2 ln q 2 dependence for momenta above 1 GeV.

Physical review, Oct 24, 2017

We revisit the static potential for the QQQQ system using SU(3) lattice simulations, studying bot... more We revisit the static potential for the QQQQ system using SU(3) lattice simulations, studying both the colour singlets groundstate and first excited state. We consider geometries where the two static quarks and the two anti-quarks are at the corners of rectangles of different sizes. We analyse the transition between a tetraquark system and a two meson system with a two by two correlator matrix. We compare the potentials computed with quenched QCD and with dynamical quarks. We also compare our simulations with the results of previous studies and analyze quantitatively fits of our results with anzatse inspired in the string flip-flop model and in its possible colour excitations.

arXiv (Cornell University), Oct 21, 2013

We address the interpretation of the Landau gauge gluon propagator at finite temperature as a mas... more We address the interpretation of the Landau gauge gluon propagator at finite temperature as a massive type bosonic propagator. Using pure gauge SU(3) lattice simulations at a fixed lattice volume ∼ (6.5f m) 3 , we compute the electric and magnetic form factors, extract a gluon mass from Yukawa-like fits, and study its temperature dependence. This is relevant both for the Debye screening at high temperature T and for confinement at low T .

arXiv (Cornell University), Jan 7, 2014

arXiv (Cornell University), Oct 7, 2010

We discuss the CUDA approach to the simulation of pure gauge Lattice SU(2). CUDA is a hardware an... more We discuss the CUDA approach to the simulation of pure gauge Lattice SU(2). CUDA is a hardware and software architecture developed by NVIDIA for computing on the GPU. We present an analysis and performance comparison between the GPU and CPU with single precision. Analysis with single and multiple GPU's, using CUDA and OPENMP, are also presented. In order to obtain a high performance, the code must be optimized for the GPU architecture, i.e., an implementation that exploits the memory hierarchy of the CUDA programming model. Using GPU texture memory and minimizing the data transfers between CPU and GPU, we achieve a speedup of 200× using 2 NVIDIA 295 GTX cards relative to a serial CPU, which demonstrates that GPU's can serve as an efficient platform for scientific computing. With multi-GPU's we are able, in one day computation, to generate 1 000 000 gauge configurations in a 48 4 lattice with β = 6.0 and calculate the mean average plaquette. We present results for the mean average plaquette in several lattice sizes for different β. Finally we present results for the mean average Polyakov loop at finite temperature.

arXiv (Cornell University), Oct 5, 2010

The colour fields, created by a static gluon-quark-antiquark system, are computed in quenched SU(... more The colour fields, created by a static gluon-quark-antiquark system, are computed in quenched SU(3) lattice QCD, in a 24 3 × 48 lattice at β = 6.2 and a = 0.07261(85) f m. We study two geometries, one with a U shape and another with an L shape. The particular cases of the two gluon glueball and quark-antiquark are also studied, and the Casimir scaling is investigated in a microscopic perspective. This also contributes to understand confinement with flux tubes and to discriminate between the models of fundamental versus adjoint confining strings, analogous to type-II and type-I superconductivity.

Proceedings of The 38th International Symposium on Lattice Field Theory — PoS(LATTICE2021)

We study = 0 quarkonium resonances decaying into pairs of heavy-light mesons using staticstatic-l... more We study = 0 quarkonium resonances decaying into pairs of heavy-light mesons using staticstatic-light-light potentials from lattice QCD. To this end, we solve a coupled channel Schrödinger equation with a confined quarkonium channel and channels with a heavy-light meson pair to compute phase shifts and T matrix poles for the lightest decay channel. We discuss our results for , , and wave states in the context of corresponding experimental results, in particular for Υ(10753) and Υ(10860).

arXiv (Cornell University), Oct 5, 2010

We develop a formalism to study tetraquarks using the generalized flip-flop potential, which incl... more We develop a formalism to study tetraquarks using the generalized flip-flop potential, which include the tetraquark potential component. Technically this is a difficult problem, needing the solution of the Schrödinger equation in a multidimensional space. Since the tetraquark may at any time escape to a pair of mesons, here we study a simplified twovariable toy model and explore the analogy with a cherry in a glass, but a broken one where the cherry may escape from. We also compute the decay width in this two-variable picture, solving the Schrödinger equation for the outgoing spherical wave.

arXiv (Cornell University), Apr 1, 2010

The colour fields, created by a static gluon-quark-antiquark system, are computed in quenched SU(... more The colour fields, created by a static gluon-quark-antiquark system, are computed in quenched SU(3) lattice QCD, in a 24 3 × 48 lattice at β = 6.2 and a = 0.07261(85) f m. We compute the hybrid Wilson Loop including the cases when the gluon and the antiquark are superposed, i. e., the quark-antiquark case and when the quark and antiquark are superposed, i. e., the gluon-gluon case. The Casimir scaling is investigated, in the two gluon glueball case the Casimir scaling is consistent with the formation of an adjoint string. Measuring the decay of the tail in the mid section of the flux tube for the two gluon glueball and for the quark-antiquark meson, we determine the penetration length and present a gauge invariant effective dual gluon mass of 0.905 ± 0.163 GeV. We also try to determine the coherence length comparing our results with the dual Ginzburg-Landau approach. With the penetration length and the possible coherence length we determine a putative Ginzburg-Landau dimensionless parameter, which is possibly consistent with a type II superconductor picture. These results are obtained at fixed quark-antiquark distance of 0.58 fm.

arXiv (Cornell University), May 27, 2021

Spectra with full towers of levels are expected due to the quantization of the string vibrations,... more Spectra with full towers of levels are expected due to the quantization of the string vibrations, however different theoretical models exist for the excitation spectra. First principle computations are important to test the different models and to search for novel phenomena, but so far only a few excited states of QCD flux tubes have been studied with pure gauge SU(3) lattice QCD in 3+1 dimensions. We thus aim to study a spectrum of flux tubes with static quark and antiquark sources up to a significant number of excitations. We specialize in the most symmetric case, the Sigmag+\Sigma_g^+Sigmag+, where up to two levels are already published in the literature. To achieve the highest possible excitation level, we construct a large set of operators with the correct symmetry, solve the generalized eigenvalue problem and compare the results of different lattice QCD gauge actions with different lattice spacings and anisotropies.

EPJ Web of Conferences, 2018

We present colour field density profiles for some of the first SU(3) gluonic excitations of the f... more We present colour field density profiles for some of the first SU(3) gluonic excitations of the flux tube in the presence of a static quark-antiquark pair. The results are obtained from a large set of gluonic operators.