Alaa Abd El-Hady | Zagazig University (original) (raw)
Papers by Alaa Abd El-Hady
We calculate the elastic form factors and the Generalized Parton Distributions (GPDs) for four lo... more We calculate the elastic form factors and the Generalized Parton Distributions (GPDs) for four low-lying bound states of a demonstration fermion-antifermion system, strong coupling positronium (e¯ e), using Basis Light-Front Quantization (BLFQ). Using this approach, we also calculate the impact-parameter dependent GPDs q(x, b ⊥) to visualize the fermion density in the transverse plane (b ⊥). We compare selected results with corresponding quantities in the non-relativistic limit to reveal relativistic effects. Our results establish the foundation within BLFQ for investigating the form factors and the GPDs for hadronic systems.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2014
Simulations of the dynamics of ions trapped in a Paul trap with terms in the potential up to the ... more Simulations of the dynamics of ions trapped in a Paul trap with terms in the potential up to the order 10 have been carried out. The power series method is used to solve numerically the equations of motion of the ions. The stability diagram has been studied and the buffer gas cooling has been implemented by a Monte Carlo method. The dipole excitation was also included. The method has been applied to an existing trap and it has shown good agreement with the experimental results and previous simulations using other methods.
Journal of Physics A-mathematical and General, 2002
We study the effect of gradual symmetry breaking in a non-integrable system on the level fluctuat... more We study the effect of gradual symmetry breaking in a non-integrable system on the level fluctuation statistics. We consider the case when the symmetry is represented by a quantum number that takes one of two possible values, so that the unperturbed system has a spectrum composed of two independent sequences. When symmetry-breaking perturbation is represented by a random matrix with an adjustable strength, the shape of the spectrum monotonously evolves towards the Wigner distribution as the strength parameter increases. This contradicts the observed behaviour of the acoustic resonance spectra in quartz blocks during the breaking of a point-group symmetry that has two eigenvalues, where the system changes in the beginning towards the Poisson statistics then turns back to the GOE statistics. This behaviour is explained by assuming that the symmetry breaking perturbation removes the degeneracy of a limited number of levels, thus creating a third chaotic sequence. As symmetry breaking increases, the new sequence grows at the expense of the initial pair until it overwhelms the whole spectrum when the symmetry completely disappears. The calculated spacing distribution and spectral rigidity are able to describe the evolution of the observed acoustic resonance spectra.
We apply Tsallis's q-indexed nonextensive entropy to formulate a random matrix theory (RM... more We apply Tsallis's q-indexed nonextensive entropy to formulate a random matrix theory (RMT), which may be suitable for systems with mixed regular-chaotic dynamics. We consider the super-extensive regime of q<1. We obtain analytical expressions for the level-spacing distributions, which are strictly valid for 2 X2 random-matrix ensembles, as usually done in the standard RMT. We compare the results with spacing
Physical Review D, 2006
It is pointed out that if the molecular interpretation of the recently observed resonance X(3872)... more It is pointed out that if the molecular interpretation of the recently observed resonance X(3872) is valid, then nature may have prepared a good laboratory for us to examine the phenomenon of superradiance and subradiance of Dicke. The superradiance and supradiance factors are evaluated and the effects on the electromagnetic radiative decay of X(3872) are discussed. Our results using coordinate space representation is similar to the momentum space results of Voloshin.
We use two relativistic quasi-potential equations to fit meson spectra. A global fit of 45 mesons... more We use two relativistic quasi-potential equations to fit meson spectra. A global fit of 45 mesons is achieved with an rams deviation from experiment of 43 MeV, and we compare meson two-photon decay widths calculated using the model wave functions with experimentally measured widths. We give an example calculation of in-medium (high temperature) effects that may be incorporated in the models.
Physical Review D, 2005
We evaluate the complete spectrum of the B c mesons, below the open flavor BD threshold, in a Bet... more We evaluate the complete spectrum of the B c mesons, below the open flavor BD threshold, in a Bethe-Salpeter model. We make predictions for the radiative decay widths of the B c excited states. We compare our results with those of other models.
Physical Review D, 1997
We calculate the form factors for the semileptonic decays of the B meson to D and D* mesons in a ... more We calculate the form factors for the semileptonic decays of the B meson to D and D* mesons in a Bethe-Salpeter model. We show that our model is consistent with the constraints of heavy quark effective theory (HQET) and we extract the matrix elements that represent the 1/mQ corrections to the form factors in HQET. We obtain Λ¯~0.55 GeV which is consistent with QCD sum rules but higher than its estimate in nonrelativistic quark model calculations. With available data, we obtain Vcb=(31.9+/-1.4)×10-3.
We study the |∆I| = 3/2 amplitudes of hyperon non-leptonic decays of the form B → B ′ π in the co... more We study the |∆I| = 3/2 amplitudes of hyperon non-leptonic decays of the form B → B ′ π in the context of chiral perturbation theory. The lowest-order predictions are determined in terms of only one unknown parameter and are consistent within errors with current data. We investigate the theoretical uncertainty of these predictions by calculating the leading nonanalytic corrections. We also present an estimate for the size of the S-wave Λ and Ξ decays which vanish at leading order. We find that the corrections to the lowest-order predictions are within the expectations of naive power counting and, therefore, that this picture can be tested more accurately with improved measurements.
The bound state of a bottom and a charm quark (B_c) is of great theoretical and experimental inte... more The bound state of a bottom and a charm quark (B_c) is of great theoretical and experimental interest. Its weak decay is expected to yield a large branching fraction to final states containing J/ψ. We have evaluated the spectrum of different channels and calculated the corresponding wave functions using reductions of Bethe-Salpeter Equation (BSE), namely the so-called Thompson reduction and another one, named ``new'' reduction. The interaction kernel used consists of a one-gluon exchange in the ladder approximation, and, a phenomenological, long range confinement potentials in momentum space. The mass parameters and the coupling parameters used, are taken from previous work which reproduce the known results consistently. These wave functions can be used to study different decay channels of Bc meson. Specifically the leptonic decay constant and the semileptonic form factors can be used to study the leptonic and the semileptonic decay channels. The ground state Bc mass thus obtained is 6.356 GeV, well within the agreement of recently CDF observed value, 6.4 ± 0.39 ± 0.13 GeV^[1]. [1] CDF collaboration, F. Abe et al. al., hep-ex/9804014; V. Papadimitriou (Private communication).
Physical Review D, 1999
We apply our Bethe-Salpeter model for mesons to the Bc family with parameters fixed in our previo... more We apply our Bethe-Salpeter model for mesons to the Bc family with parameters fixed in our previous investigation. We evaluate the mass of the pseudoscalar Bc meson as 6.356 and 6.380 GeV/c2 and the lifetime as 0.47 and 0.46 ps, respectively, in two reductions of the Bethe-Salpeter equation, in good agreement with the recently reported mass of 6.40+/-0.39 (stat) +/-0.13 (syst) GeV/c2 and lifetime of 0.46+0.18-0.16 (stat) +/-0.03 (syst) ps by the CDF Collaboration. We evaluate the decay constant of the Bc meson and compare different contributions to its decay width.
Physical Review D, 1995
We calculate the Isgur-Wise function from the solutions of the Bethe-Salpeter equations. The shap... more We calculate the Isgur-Wise function from the solutions of the Bethe-Salpeter equations. The shape of the Isgur-Wise function thus calculated is a prediction of the Bethe-Salpeter equations and does not depend on undetermined parameters. We develop an analytical approximation to our Isgur-Wise function in the form ξ(ω) = η[1 − ρ 2 η (ω − 1) + a(ω − 1) 3/2 ] where ρ 2 = 1.279, a = .91, η = .9942 and ω is the recoil velocity. The Isgur-Wise function is then used to obtain V cb from the recent experimental data ofB → D * ℓν decay. Our best estimate of V cb is (34.7 ± 2.5) × 10 −3 , which is comparable to some of the latest estimates in the literature.
Physical Review D, 1998
We evaluate the decay constants for the B and D mesons and the form factors for the semileptonic ... more We evaluate the decay constants for the B and D mesons and the form factors for the semileptonic decays of the B meson to D and D* mesons in a Bethe-Salpeter model. From data we extract Vcb=0.039+/-0.002 from B¯-->D*lν¯ and Vcb=0.037+/-0.004 from B¯-->Dlν¯ decays. The form factors are then used to obtain non-leptonic decay partial widths for B-->Dπ(K) and B-->DD(Ds) in the factorization approximation.
The authors calculate the Isgur-Wise function from solutions of the Bethe-Salpeter equations. The... more The authors calculate the Isgur-Wise function from solutions of the Bethe-Salpeter equations. These equations have a kernel consisting of one gluon exchange and linear confinement adjusted to give a good phenomenological description of meson mass spectra. The shape of the calculated Isgur-Wise function is thus a prediction of the Beth-Salpeter equations and does not depend on undetermined parameters. The authors
Physical Review D, 2000
We recalculate the leading nonanalytic contributions to the amplitudes for hyperon nonleptonic de... more We recalculate the leading nonanalytic contributions to the amplitudes for hyperon nonleptonic decays in chiral perturbation theory. Our results partially disagree with those calculated before, and include new terms previously omitted in the P-wave amplitudes. Although these modifications are numerically significant, they do not change the well-known fact that good agreement with experiment cannot be simultaneously achieved using one-loop S-and P-wave amplitudes.
Physics Letters B, 1995
We extend our earlier model of qq mesons using relativistic quasipotential (QP) wave equations to... more We extend our earlier model of qq mesons using relativistic quasipotential (QP) wave equations to include open-flavor states and running quark-gluon coupling effects. Global fits to meson spectra are achieved with rms deviations from experiment of 43-50 MeV. We examine in-medium effects through their influence on the confining interaction and predict the confining strength at which the masses of certain mesons fall below the threshold of their dominant decay channel.
Physical Review D, 1999
We apply our Bethe-Salpeter model for mesons to the B c family with parameters fixed in our previ... more We apply our Bethe-Salpeter model for mesons to the B c family with parameters fixed in our previous investigation. We evaluate the mass of the pseudo-scalar B c meson as 6.356 GeV/c 2 and 6.380 GeV/c 2 and the lifetime as 0.47 ps and 0.46 ps respectively in two reductions of the Bethe-Salpeter Equation, in good agreement with the recently reported mass of 6.40 ± 0.39 (stat.) ± 0.13 (syst.) GeV/c 2 and lifetime of 0.46 +0.18 −0.16 (stat.) ± 0.03 (syst.) ps by the CDF Collaboration. We evaluate the decay constant of the B c meson and compare different contributions to its decay width.
Physical Review D, 1995
We calculate the Isgur-Wise function from the solutions of the Bethe-Salpeter equations. The shap... more We calculate the Isgur-Wise function from the solutions of the Bethe-Salpeter equations. The shape of the Isgur-Wise function thus calculated is a prediction of the Bethe-Salpeter equations and does not depend on undetermined parameters. We develop a best fit to the numerically computed Isgur-Wise function in the form ξ(ω)=η[1-ρ2/η(ω-1)+a(ω-1)3/2], where ρ2=1.279, a=0.91, η=0.9942, and ω is the recoil velocity. The Isgur-Wise function is then used to obtain Vcb from the recent experimental data of B¯-->D*lν¯ decay. Our best estimate of Vcb is (34.7+/-2.5)×10-3, which is comparable to some of the latest estimates in the literature.
Physical Review D, 2000
We make predictions for the exclusive semileptonic and nonleptonic decay widths of the Bc meson. ... more We make predictions for the exclusive semileptonic and nonleptonic decay widths of the Bc meson. We evaluate the Bc semileptonic form factors for different decay channels in a relativistic model, and use factorization to obtain the nonleptonic decay widths.
We calculate the elastic form factors and the Generalized Parton Distributions (GPDs) for four lo... more We calculate the elastic form factors and the Generalized Parton Distributions (GPDs) for four low-lying bound states of a demonstration fermion-antifermion system, strong coupling positronium (e¯ e), using Basis Light-Front Quantization (BLFQ). Using this approach, we also calculate the impact-parameter dependent GPDs q(x, b ⊥) to visualize the fermion density in the transverse plane (b ⊥). We compare selected results with corresponding quantities in the non-relativistic limit to reveal relativistic effects. Our results establish the foundation within BLFQ for investigating the form factors and the GPDs for hadronic systems.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2014
Simulations of the dynamics of ions trapped in a Paul trap with terms in the potential up to the ... more Simulations of the dynamics of ions trapped in a Paul trap with terms in the potential up to the order 10 have been carried out. The power series method is used to solve numerically the equations of motion of the ions. The stability diagram has been studied and the buffer gas cooling has been implemented by a Monte Carlo method. The dipole excitation was also included. The method has been applied to an existing trap and it has shown good agreement with the experimental results and previous simulations using other methods.
Journal of Physics A-mathematical and General, 2002
We study the effect of gradual symmetry breaking in a non-integrable system on the level fluctuat... more We study the effect of gradual symmetry breaking in a non-integrable system on the level fluctuation statistics. We consider the case when the symmetry is represented by a quantum number that takes one of two possible values, so that the unperturbed system has a spectrum composed of two independent sequences. When symmetry-breaking perturbation is represented by a random matrix with an adjustable strength, the shape of the spectrum monotonously evolves towards the Wigner distribution as the strength parameter increases. This contradicts the observed behaviour of the acoustic resonance spectra in quartz blocks during the breaking of a point-group symmetry that has two eigenvalues, where the system changes in the beginning towards the Poisson statistics then turns back to the GOE statistics. This behaviour is explained by assuming that the symmetry breaking perturbation removes the degeneracy of a limited number of levels, thus creating a third chaotic sequence. As symmetry breaking increases, the new sequence grows at the expense of the initial pair until it overwhelms the whole spectrum when the symmetry completely disappears. The calculated spacing distribution and spectral rigidity are able to describe the evolution of the observed acoustic resonance spectra.
We apply Tsallis's q-indexed nonextensive entropy to formulate a random matrix theory (RM... more We apply Tsallis's q-indexed nonextensive entropy to formulate a random matrix theory (RMT), which may be suitable for systems with mixed regular-chaotic dynamics. We consider the super-extensive regime of q<1. We obtain analytical expressions for the level-spacing distributions, which are strictly valid for 2 X2 random-matrix ensembles, as usually done in the standard RMT. We compare the results with spacing
Physical Review D, 2006
It is pointed out that if the molecular interpretation of the recently observed resonance X(3872)... more It is pointed out that if the molecular interpretation of the recently observed resonance X(3872) is valid, then nature may have prepared a good laboratory for us to examine the phenomenon of superradiance and subradiance of Dicke. The superradiance and supradiance factors are evaluated and the effects on the electromagnetic radiative decay of X(3872) are discussed. Our results using coordinate space representation is similar to the momentum space results of Voloshin.
We use two relativistic quasi-potential equations to fit meson spectra. A global fit of 45 mesons... more We use two relativistic quasi-potential equations to fit meson spectra. A global fit of 45 mesons is achieved with an rams deviation from experiment of 43 MeV, and we compare meson two-photon decay widths calculated using the model wave functions with experimentally measured widths. We give an example calculation of in-medium (high temperature) effects that may be incorporated in the models.
Physical Review D, 2005
We evaluate the complete spectrum of the B c mesons, below the open flavor BD threshold, in a Bet... more We evaluate the complete spectrum of the B c mesons, below the open flavor BD threshold, in a Bethe-Salpeter model. We make predictions for the radiative decay widths of the B c excited states. We compare our results with those of other models.
Physical Review D, 1997
We calculate the form factors for the semileptonic decays of the B meson to D and D* mesons in a ... more We calculate the form factors for the semileptonic decays of the B meson to D and D* mesons in a Bethe-Salpeter model. We show that our model is consistent with the constraints of heavy quark effective theory (HQET) and we extract the matrix elements that represent the 1/mQ corrections to the form factors in HQET. We obtain Λ¯~0.55 GeV which is consistent with QCD sum rules but higher than its estimate in nonrelativistic quark model calculations. With available data, we obtain Vcb=(31.9+/-1.4)×10-3.
We study the |∆I| = 3/2 amplitudes of hyperon non-leptonic decays of the form B → B ′ π in the co... more We study the |∆I| = 3/2 amplitudes of hyperon non-leptonic decays of the form B → B ′ π in the context of chiral perturbation theory. The lowest-order predictions are determined in terms of only one unknown parameter and are consistent within errors with current data. We investigate the theoretical uncertainty of these predictions by calculating the leading nonanalytic corrections. We also present an estimate for the size of the S-wave Λ and Ξ decays which vanish at leading order. We find that the corrections to the lowest-order predictions are within the expectations of naive power counting and, therefore, that this picture can be tested more accurately with improved measurements.
The bound state of a bottom and a charm quark (B_c) is of great theoretical and experimental inte... more The bound state of a bottom and a charm quark (B_c) is of great theoretical and experimental interest. Its weak decay is expected to yield a large branching fraction to final states containing J/ψ. We have evaluated the spectrum of different channels and calculated the corresponding wave functions using reductions of Bethe-Salpeter Equation (BSE), namely the so-called Thompson reduction and another one, named ``new'' reduction. The interaction kernel used consists of a one-gluon exchange in the ladder approximation, and, a phenomenological, long range confinement potentials in momentum space. The mass parameters and the coupling parameters used, are taken from previous work which reproduce the known results consistently. These wave functions can be used to study different decay channels of Bc meson. Specifically the leptonic decay constant and the semileptonic form factors can be used to study the leptonic and the semileptonic decay channels. The ground state Bc mass thus obtained is 6.356 GeV, well within the agreement of recently CDF observed value, 6.4 ± 0.39 ± 0.13 GeV^[1]. [1] CDF collaboration, F. Abe et al. al., hep-ex/9804014; V. Papadimitriou (Private communication).
Physical Review D, 1999
We apply our Bethe-Salpeter model for mesons to the Bc family with parameters fixed in our previo... more We apply our Bethe-Salpeter model for mesons to the Bc family with parameters fixed in our previous investigation. We evaluate the mass of the pseudoscalar Bc meson as 6.356 and 6.380 GeV/c2 and the lifetime as 0.47 and 0.46 ps, respectively, in two reductions of the Bethe-Salpeter equation, in good agreement with the recently reported mass of 6.40+/-0.39 (stat) +/-0.13 (syst) GeV/c2 and lifetime of 0.46+0.18-0.16 (stat) +/-0.03 (syst) ps by the CDF Collaboration. We evaluate the decay constant of the Bc meson and compare different contributions to its decay width.
Physical Review D, 1995
We calculate the Isgur-Wise function from the solutions of the Bethe-Salpeter equations. The shap... more We calculate the Isgur-Wise function from the solutions of the Bethe-Salpeter equations. The shape of the Isgur-Wise function thus calculated is a prediction of the Bethe-Salpeter equations and does not depend on undetermined parameters. We develop an analytical approximation to our Isgur-Wise function in the form ξ(ω) = η[1 − ρ 2 η (ω − 1) + a(ω − 1) 3/2 ] where ρ 2 = 1.279, a = .91, η = .9942 and ω is the recoil velocity. The Isgur-Wise function is then used to obtain V cb from the recent experimental data ofB → D * ℓν decay. Our best estimate of V cb is (34.7 ± 2.5) × 10 −3 , which is comparable to some of the latest estimates in the literature.
Physical Review D, 1998
We evaluate the decay constants for the B and D mesons and the form factors for the semileptonic ... more We evaluate the decay constants for the B and D mesons and the form factors for the semileptonic decays of the B meson to D and D* mesons in a Bethe-Salpeter model. From data we extract Vcb=0.039+/-0.002 from B¯-->D*lν¯ and Vcb=0.037+/-0.004 from B¯-->Dlν¯ decays. The form factors are then used to obtain non-leptonic decay partial widths for B-->Dπ(K) and B-->DD(Ds) in the factorization approximation.
The authors calculate the Isgur-Wise function from solutions of the Bethe-Salpeter equations. The... more The authors calculate the Isgur-Wise function from solutions of the Bethe-Salpeter equations. These equations have a kernel consisting of one gluon exchange and linear confinement adjusted to give a good phenomenological description of meson mass spectra. The shape of the calculated Isgur-Wise function is thus a prediction of the Beth-Salpeter equations and does not depend on undetermined parameters. The authors
Physical Review D, 2000
We recalculate the leading nonanalytic contributions to the amplitudes for hyperon nonleptonic de... more We recalculate the leading nonanalytic contributions to the amplitudes for hyperon nonleptonic decays in chiral perturbation theory. Our results partially disagree with those calculated before, and include new terms previously omitted in the P-wave amplitudes. Although these modifications are numerically significant, they do not change the well-known fact that good agreement with experiment cannot be simultaneously achieved using one-loop S-and P-wave amplitudes.
Physics Letters B, 1995
We extend our earlier model of qq mesons using relativistic quasipotential (QP) wave equations to... more We extend our earlier model of qq mesons using relativistic quasipotential (QP) wave equations to include open-flavor states and running quark-gluon coupling effects. Global fits to meson spectra are achieved with rms deviations from experiment of 43-50 MeV. We examine in-medium effects through their influence on the confining interaction and predict the confining strength at which the masses of certain mesons fall below the threshold of their dominant decay channel.
Physical Review D, 1999
We apply our Bethe-Salpeter model for mesons to the B c family with parameters fixed in our previ... more We apply our Bethe-Salpeter model for mesons to the B c family with parameters fixed in our previous investigation. We evaluate the mass of the pseudo-scalar B c meson as 6.356 GeV/c 2 and 6.380 GeV/c 2 and the lifetime as 0.47 ps and 0.46 ps respectively in two reductions of the Bethe-Salpeter Equation, in good agreement with the recently reported mass of 6.40 ± 0.39 (stat.) ± 0.13 (syst.) GeV/c 2 and lifetime of 0.46 +0.18 −0.16 (stat.) ± 0.03 (syst.) ps by the CDF Collaboration. We evaluate the decay constant of the B c meson and compare different contributions to its decay width.
Physical Review D, 1995
We calculate the Isgur-Wise function from the solutions of the Bethe-Salpeter equations. The shap... more We calculate the Isgur-Wise function from the solutions of the Bethe-Salpeter equations. The shape of the Isgur-Wise function thus calculated is a prediction of the Bethe-Salpeter equations and does not depend on undetermined parameters. We develop a best fit to the numerically computed Isgur-Wise function in the form ξ(ω)=η[1-ρ2/η(ω-1)+a(ω-1)3/2], where ρ2=1.279, a=0.91, η=0.9942, and ω is the recoil velocity. The Isgur-Wise function is then used to obtain Vcb from the recent experimental data of B¯-->D*lν¯ decay. Our best estimate of Vcb is (34.7+/-2.5)×10-3, which is comparable to some of the latest estimates in the literature.
Physical Review D, 2000
We make predictions for the exclusive semileptonic and nonleptonic decay widths of the Bc meson. ... more We make predictions for the exclusive semileptonic and nonleptonic decay widths of the Bc meson. We evaluate the Bc semileptonic form factors for different decay channels in a relativistic model, and use factorization to obtain the nonleptonic decay widths.