J. Peláez - Academia.edu (original) (raw)
Papers by J. Peláez
Proceedings of International Workshop on Effective Field Theories: from the pion to the upsilon — PoS(EFT09), 2009
We report our progress on the data analysis of ππ scattering data in terms of Forward Dispersion ... more We report our progress on the data analysis of ππ scattering data in terms of Forward Dispersion Relations (FDR), as well as Roy equations (RE) and their once-subtracted counterpart, GKPY equations. The first part of the analysis consists of independent fits to the different ππ channels. The GKPY equations provide a more stringent consistency check for the parametrizations of the S0-wave data in the region from 400 to 1100 MeV, In the second part we present our preliminary analysis where the fits are constrained to satisfy all dispersion relations within errors, including the new GKPY Eqs., thus providing a very precise and model independent description of data using just analyticity, causality and crossing.
International Journal of Modern Physics A, 2009
We present a set of once subtracted dispersion relations which implement crossing symmetry condit... more We present a set of once subtracted dispersion relations which implement crossing symmetry conditions for the ππ scattering amplitudes below 1 GeV. We compare and discuss the results obtained for the once and twice subtracted dispersion relations, known as Roy's equations, for three ππ partial JI waves, S0, P and S2. We also show that once subtracted dispersion relations provide a stringent test of crossing and analyticity for ππ partial wave amplitudes, remarkably precise in the 400 to 1.1 GeV region, where the resulting uncertainties are significantly smaller than those coming from standard Roy's equations, given the same input.
International Journal of Modern Physics A, 2005
We have recently presented a Regge description of ππ total cross sections valid above 1.4 GeV, co... more We have recently presented a Regge description of ππ total cross sections valid above 1.4 GeV, consistent with the few existing experiments, factorization and crossing symmetry. In this note we show how it also describes a further large data sample obtained from an analysis of experiments on π±p→XΔ++ and π±n→Xp.
Physical Review D, 2008
We complete and improve the fits to experimental ππ scattering amplitudes, both at low and high e... more We complete and improve the fits to experimental ππ scattering amplitudes, both at low and high energies, that we performed in the previous papers of this series. We then verify that the corresponding amplitudes satisfy analyticity requirements, in the form of partial wave analyticity at low energies, forward dispersion relations (FDR) at all energies, and Roy equations belowKK threshold; the first by construction, the last two, inside experimental errors. Then we repeat the fits including as constraints FDR and Roy equations. The ensuing central values of the various scattering amplitudes verify very accurately FDR and, especially, Roy equations, and change very little from what we found by just fitting data, with the exception of the D2 wave phase shift, for which one parameter moves by 1.5 σ. These improved parametrizations therefore provide a reliable representation of pion-pion amplitudes with which one can test various physical relations. We also present a list of low energy parameters and other observables. In particular, we find a (0) 0
AIP Conference Proceedings, 2001
We report on our one-loop calculation of all the two meson scattering amplitudes within SU(3) Chi... more We report on our one-loop calculation of all the two meson scattering amplitudes within SU(3) Chiral Perturbation Theory, i.e. with pions, kaons and etas. Once the amplitudes are imitarized with the coupled channel Inverse Amplitude Method, they satisfy simultaneously the correct low-energy chiral constraints and unitarity. We obtain a remarkable description of meson-meson scattering data up to 1.2 GeV including the scattering lengths and seven light resonances.
AIP Conference Proceedings, 2005
Our results on obtaining the Regge trajectory of a resonance from its pole in a scattering proces... more Our results on obtaining the Regge trajectory of a resonance from its pole in a scattering process and from analytic constraints in the complex angular momentum plane are presented. The method, suited for resonances that dominate an elastic scattering amplitude, has been applied to the ρ(770), f 2 (1270), f 2 (1525) and f 0 (500) resonances. Whereas for the first three we obtain linear Regge trajectories, characteristic of ordinary quark-antiquark states, for the latter we find a nonlinear trajectory with a much smaller slope at the resonance mass. We also show that if a linear trajectory with a slope of typical size is imposed for the f 0 (500), the corresponding amplitude is at odds with the data. This provides a strong indication of the non-ordinary nature of the sigma meson.
Lecture Notes in Physics
This is the summary of the working group on Goldstone Boson Production and Decay of the Chiral Dy... more This is the summary of the working group on Goldstone Boson Production and Decay of the Chiral Dynamics Workshop in Mainz, September 1-5, 1997. For the production aspects we discuss π 0 and η production in nucleon-nucleon collisions and the behaviour of hadrons in various sum rules. For the decays we present a discussion on various K, η and π decay channels. Other aspects discussed are a new treatment of meson-meson scattering, the light-by-light contribution to the muon anomalous magnetic moment and progress in various aspects of the p 6 generating functional in the mesonic sector.
![Research paper thumbnail of N[sub c] and m[sub π] dependence of ρ and σ mesons from unitarized Chiral Perturbation Theory](https://attachments.academia-assets.com/88117056/thumbnails/1.jpg)
](We review our work on the ρ and σ resonances derived from the Inverse Amplitude Method. In partic... more We review our work on the ρ and σ resonances derived from the Inverse Amplitude Method. In particular, we study the leading 1/N c behavior of the resonances masses and widths and their evolution with changing m π. The 1/N c expansion gives a clear definition ofqq states, which is neatly satisfied by the ρ but not by the σ , showing that its dominant component is notqq. The m π dependence of the resonance properties is relevant to connect with lattice studies. We show that our predictions compare well with some lattice results and we find that the ρππ coupling constant is m π independent, in contrast with the σ ππ coupling, that shows a strong m π dependence.
The mini-proceedings of the Light Meson Dynamics Workshop held in Mainz from February 10 th to 12... more The mini-proceedings of the Light Meson Dynamics Workshop held in Mainz from February 10 th to 12 th , 2014, are presented.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 2005
We discuss the thermal behaviour of the pion vector form factors and calculate them in one-loop C... more We discuss the thermal behaviour of the pion vector form factors and calculate them in one-loop Chiral Perturbation Theory. The perturbative result is used to analyze the T-dependent electromagnetic pion charge radius, obtaining a rough estimate of the deconfinement critical temperature. Imposing thermal unitarity, we generate the ρ resonance pole for the form factor in the center of mass frame. The ρ peak height in the modulus of the form factor decreases for increasing temperature, while its width increases and the peak position is slightly shifted downwards for T ≃ 150 MeV. These results point in the direction suggested by many analysis of dilepton production data in relativistic heavy ion collisions.
Progress in Particle and Nuclear Physics, 2000
By means of a coupled channel non-perturbative unitary approach, it is possible to extend the str... more By means of a coupled channel non-perturbative unitary approach, it is possible to extend the strong constrains of Chiral Perturbation Theory to higher energies. In particular, it is possible to reproduce the lowest lying resonances in mesonmeson scattering up to 1.2 GeV using the parameters of the O(p 2) and O(p 4) Chiral Lagrangian. The meson baryon sector can also be tackled along similar lines. We report on an update of these results showing some examples of photon induced reactions where the techniques have been recently applied.
Physical Review D, 1997
Within the chiral Lagrangian formalism it is possible to describe the general strongly coupled sy... more Within the chiral Lagrangian formalism it is possible to describe the general strongly coupled symmetrybreaking sector in terms of a few parameters. Based on a dispersive approach we study the resonance spectrum up to 3 TeV in chiral parameter space. This procedure could also be useful to extract higher energy resonant behavior from low-energy collider data. It is also shown how the method reproduces the correct pole structure of resonances as well as other analytic features. The results also hint at a possible excluded region of parameter space. ͓S0556-2821͑97͒02307-2͔
Nuclear Physics B - Proceedings Supplements, 2009
We show how the new precise data on kaon decays together with forward dispersion relations, sum r... more We show how the new precise data on kaon decays together with forward dispersion relations, sum rules and once-and twice-subtracted Roy's equations allow for a precise determination of the sigma meson pole position. We present a comparison and a study of the different sources of uncertainties when using either once-or twicesubtracted Roy's equations to analyze the data. Finally we present a preliminary determination of the σ pole from the constrained dispersive data analysis.
Modern Physics Letters A, 2004
By means of unitarized Chiral Perturbation Theory it is possible to obtain a remarkable descripti... more By means of unitarized Chiral Perturbation Theory it is possible to obtain a remarkable description of meson–meson scattering amplitudes up to 1.2 GeV, and generate poles associated to scalar and vector resonances. Since Chiral Perturbation Theory is the QCD low energy effective theory, it is then possible to study its large-N c limit where [Formula: see text] states are easily identified. The vectors thus generated follow closely a [Formula: see text] behavior, whereas the light scalar poles follow the large-N c behavior expected for a dominant tetraquark or two-meson structure.
The low energy dynamics of the general strongly interacting symmetry breaking sector can be easil... more The low energy dynamics of the general strongly interacting symmetry breaking sector can be easily described using effective chiral Lagrangians. Indeed, the enhancement in WW scattering at LHC, that would imply the existence of such an strong interaction, can be described with just two chiral parameters. These techniques have been shown to reproduce remarkably well the low-energy pion-pion scattering data, which follows a similar formalism. In this work we first review the LHC sensitivity to those two chiral parameters (in the hardest case of non-resonant low-energy WW scattering). Later it is shown how we can predict the general resonance spectrum of the strongly interacting symmetry breaking sector. For that purpose, we use the inverse amplitude method which is also very successful reproducing the lightest hadronic resonances from data in the lowenergy non resonant region. We thus present an study of the regions in parameter space where one, two or no resonances may appear. Contribution to the XXXIInd Rencontres de Moriond: "Electroweak Interactions and Unified Theories"
We present a new technique for the calculation of helicity ±1/2 gravitino production during prehe... more We present a new technique for the calculation of helicity ±1/2 gravitino production during preheating. It is based on the equivalence between goldstinos and helicity ±1/2 gravitinos at high energies. The problem is thus reduced to the standard (Majorana) fermion production after inflation. Comparison with the results obtained in the unitary gauge is also presented.
We report on recent results on the decay of the φ into π + π − and φ radiative decays into π 0 π ... more We report on recent results on the decay of the φ into π + π − and φ radiative decays into π 0 π 0 γ and π 0 ηγ, which require the consideration of the final state interaction of a pair of mesons in a region inaccessible to Chiral Perturbation Theory. By using nonperturbative chiral unitary methods for the meson meson interaction we can obtain the corresponding decay widths and the results are compared with recent experimental data. 1 The φ → π + π − decay The φ decay into π + π − is an example of isospin violation. The φ has isospin I = 0, spin J = 1, and hence it does not couple to the π + π − system in the isospin limit, which implies the rule I + J = even. The experimental situation on this decay is rather confusing. There are two older results whose central
Proceedings of International Workshop on Effective Field Theories: from the pion to the upsilon — PoS(EFT09), 2009
We report our progress on the data analysis of ππ scattering data in terms of Forward Dispersion ... more We report our progress on the data analysis of ππ scattering data in terms of Forward Dispersion Relations (FDR), as well as Roy equations (RE) and their once-subtracted counterpart, GKPY equations. The first part of the analysis consists of independent fits to the different ππ channels. The GKPY equations provide a more stringent consistency check for the parametrizations of the S0-wave data in the region from 400 to 1100 MeV, In the second part we present our preliminary analysis where the fits are constrained to satisfy all dispersion relations within errors, including the new GKPY Eqs., thus providing a very precise and model independent description of data using just analyticity, causality and crossing.
International Journal of Modern Physics A, 2009
We present a set of once subtracted dispersion relations which implement crossing symmetry condit... more We present a set of once subtracted dispersion relations which implement crossing symmetry conditions for the ππ scattering amplitudes below 1 GeV. We compare and discuss the results obtained for the once and twice subtracted dispersion relations, known as Roy's equations, for three ππ partial JI waves, S0, P and S2. We also show that once subtracted dispersion relations provide a stringent test of crossing and analyticity for ππ partial wave amplitudes, remarkably precise in the 400 to 1.1 GeV region, where the resulting uncertainties are significantly smaller than those coming from standard Roy's equations, given the same input.
International Journal of Modern Physics A, 2005
We have recently presented a Regge description of ππ total cross sections valid above 1.4 GeV, co... more We have recently presented a Regge description of ππ total cross sections valid above 1.4 GeV, consistent with the few existing experiments, factorization and crossing symmetry. In this note we show how it also describes a further large data sample obtained from an analysis of experiments on π±p→XΔ++ and π±n→Xp.
Physical Review D, 2008
We complete and improve the fits to experimental ππ scattering amplitudes, both at low and high e... more We complete and improve the fits to experimental ππ scattering amplitudes, both at low and high energies, that we performed in the previous papers of this series. We then verify that the corresponding amplitudes satisfy analyticity requirements, in the form of partial wave analyticity at low energies, forward dispersion relations (FDR) at all energies, and Roy equations belowKK threshold; the first by construction, the last two, inside experimental errors. Then we repeat the fits including as constraints FDR and Roy equations. The ensuing central values of the various scattering amplitudes verify very accurately FDR and, especially, Roy equations, and change very little from what we found by just fitting data, with the exception of the D2 wave phase shift, for which one parameter moves by 1.5 σ. These improved parametrizations therefore provide a reliable representation of pion-pion amplitudes with which one can test various physical relations. We also present a list of low energy parameters and other observables. In particular, we find a (0) 0
AIP Conference Proceedings, 2001
We report on our one-loop calculation of all the two meson scattering amplitudes within SU(3) Chi... more We report on our one-loop calculation of all the two meson scattering amplitudes within SU(3) Chiral Perturbation Theory, i.e. with pions, kaons and etas. Once the amplitudes are imitarized with the coupled channel Inverse Amplitude Method, they satisfy simultaneously the correct low-energy chiral constraints and unitarity. We obtain a remarkable description of meson-meson scattering data up to 1.2 GeV including the scattering lengths and seven light resonances.
AIP Conference Proceedings, 2005
Our results on obtaining the Regge trajectory of a resonance from its pole in a scattering proces... more Our results on obtaining the Regge trajectory of a resonance from its pole in a scattering process and from analytic constraints in the complex angular momentum plane are presented. The method, suited for resonances that dominate an elastic scattering amplitude, has been applied to the ρ(770), f 2 (1270), f 2 (1525) and f 0 (500) resonances. Whereas for the first three we obtain linear Regge trajectories, characteristic of ordinary quark-antiquark states, for the latter we find a nonlinear trajectory with a much smaller slope at the resonance mass. We also show that if a linear trajectory with a slope of typical size is imposed for the f 0 (500), the corresponding amplitude is at odds with the data. This provides a strong indication of the non-ordinary nature of the sigma meson.
Lecture Notes in Physics
This is the summary of the working group on Goldstone Boson Production and Decay of the Chiral Dy... more This is the summary of the working group on Goldstone Boson Production and Decay of the Chiral Dynamics Workshop in Mainz, September 1-5, 1997. For the production aspects we discuss π 0 and η production in nucleon-nucleon collisions and the behaviour of hadrons in various sum rules. For the decays we present a discussion on various K, η and π decay channels. Other aspects discussed are a new treatment of meson-meson scattering, the light-by-light contribution to the muon anomalous magnetic moment and progress in various aspects of the p 6 generating functional in the mesonic sector.
We review our work on the ρ and σ resonances derived from the Inverse Amplitude Method. In partic... more We review our work on the ρ and σ resonances derived from the Inverse Amplitude Method. In particular, we study the leading 1/N c behavior of the resonances masses and widths and their evolution with changing m π. The 1/N c expansion gives a clear definition ofqq states, which is neatly satisfied by the ρ but not by the σ , showing that its dominant component is notqq. The m π dependence of the resonance properties is relevant to connect with lattice studies. We show that our predictions compare well with some lattice results and we find that the ρππ coupling constant is m π independent, in contrast with the σ ππ coupling, that shows a strong m π dependence.
The mini-proceedings of the Light Meson Dynamics Workshop held in Mainz from February 10 th to 12... more The mini-proceedings of the Light Meson Dynamics Workshop held in Mainz from February 10 th to 12 th , 2014, are presented.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 2005
We discuss the thermal behaviour of the pion vector form factors and calculate them in one-loop C... more We discuss the thermal behaviour of the pion vector form factors and calculate them in one-loop Chiral Perturbation Theory. The perturbative result is used to analyze the T-dependent electromagnetic pion charge radius, obtaining a rough estimate of the deconfinement critical temperature. Imposing thermal unitarity, we generate the ρ resonance pole for the form factor in the center of mass frame. The ρ peak height in the modulus of the form factor decreases for increasing temperature, while its width increases and the peak position is slightly shifted downwards for T ≃ 150 MeV. These results point in the direction suggested by many analysis of dilepton production data in relativistic heavy ion collisions.
Progress in Particle and Nuclear Physics, 2000
By means of a coupled channel non-perturbative unitary approach, it is possible to extend the str... more By means of a coupled channel non-perturbative unitary approach, it is possible to extend the strong constrains of Chiral Perturbation Theory to higher energies. In particular, it is possible to reproduce the lowest lying resonances in mesonmeson scattering up to 1.2 GeV using the parameters of the O(p 2) and O(p 4) Chiral Lagrangian. The meson baryon sector can also be tackled along similar lines. We report on an update of these results showing some examples of photon induced reactions where the techniques have been recently applied.
Physical Review D, 1997
Within the chiral Lagrangian formalism it is possible to describe the general strongly coupled sy... more Within the chiral Lagrangian formalism it is possible to describe the general strongly coupled symmetrybreaking sector in terms of a few parameters. Based on a dispersive approach we study the resonance spectrum up to 3 TeV in chiral parameter space. This procedure could also be useful to extract higher energy resonant behavior from low-energy collider data. It is also shown how the method reproduces the correct pole structure of resonances as well as other analytic features. The results also hint at a possible excluded region of parameter space. ͓S0556-2821͑97͒02307-2͔
Nuclear Physics B - Proceedings Supplements, 2009
We show how the new precise data on kaon decays together with forward dispersion relations, sum r... more We show how the new precise data on kaon decays together with forward dispersion relations, sum rules and once-and twice-subtracted Roy's equations allow for a precise determination of the sigma meson pole position. We present a comparison and a study of the different sources of uncertainties when using either once-or twicesubtracted Roy's equations to analyze the data. Finally we present a preliminary determination of the σ pole from the constrained dispersive data analysis.
Modern Physics Letters A, 2004
By means of unitarized Chiral Perturbation Theory it is possible to obtain a remarkable descripti... more By means of unitarized Chiral Perturbation Theory it is possible to obtain a remarkable description of meson–meson scattering amplitudes up to 1.2 GeV, and generate poles associated to scalar and vector resonances. Since Chiral Perturbation Theory is the QCD low energy effective theory, it is then possible to study its large-N c limit where [Formula: see text] states are easily identified. The vectors thus generated follow closely a [Formula: see text] behavior, whereas the light scalar poles follow the large-N c behavior expected for a dominant tetraquark or two-meson structure.
The low energy dynamics of the general strongly interacting symmetry breaking sector can be easil... more The low energy dynamics of the general strongly interacting symmetry breaking sector can be easily described using effective chiral Lagrangians. Indeed, the enhancement in WW scattering at LHC, that would imply the existence of such an strong interaction, can be described with just two chiral parameters. These techniques have been shown to reproduce remarkably well the low-energy pion-pion scattering data, which follows a similar formalism. In this work we first review the LHC sensitivity to those two chiral parameters (in the hardest case of non-resonant low-energy WW scattering). Later it is shown how we can predict the general resonance spectrum of the strongly interacting symmetry breaking sector. For that purpose, we use the inverse amplitude method which is also very successful reproducing the lightest hadronic resonances from data in the lowenergy non resonant region. We thus present an study of the regions in parameter space where one, two or no resonances may appear. Contribution to the XXXIInd Rencontres de Moriond: "Electroweak Interactions and Unified Theories"
We present a new technique for the calculation of helicity ±1/2 gravitino production during prehe... more We present a new technique for the calculation of helicity ±1/2 gravitino production during preheating. It is based on the equivalence between goldstinos and helicity ±1/2 gravitinos at high energies. The problem is thus reduced to the standard (Majorana) fermion production after inflation. Comparison with the results obtained in the unitary gauge is also presented.
We report on recent results on the decay of the φ into π + π − and φ radiative decays into π 0 π ... more We report on recent results on the decay of the φ into π + π − and φ radiative decays into π 0 π 0 γ and π 0 ηγ, which require the consideration of the final state interaction of a pair of mesons in a region inaccessible to Chiral Perturbation Theory. By using nonperturbative chiral unitary methods for the meson meson interaction we can obtain the corresponding decay widths and the results are compared with recent experimental data. 1 The φ → π + π − decay The φ decay into π + π − is an example of isospin violation. The φ has isospin I = 0, spin J = 1, and hence it does not couple to the π + π − system in the isospin limit, which implies the rule I + J = even. The experimental situation on this decay is rather confusing. There are two older results whose central