Firooz Arash | Tafresh University (original) (raw)
Papers by Firooz Arash
Phys Lett B, 2003
Partonic structure of constituent quark (or valon) in the next-to-leading order is used to calcul... more Partonic structure of constituent quark (or valon) in the next-to-leading order is used to calculate pion structure function. This is a further demonstration of the finding that the constituent quark structure is universal, and once it is calculated, the structure of any hadron can be predicted thereafter, using a convolution method, without introducing any new free parameter. The results are compared with the pion structure function from ZEUS Collaboration leading neutron production in e+p collisions at HERA. We found good agreement with the experiment. A resolution for the issue of normalization of the experimental data is suggested. In addition, the proportionality of F2pi and F2p, which have caused confusion in the normalization of ZEUS data is discussed and resolved.
A polarization test is applied to determine the spin and the parity of the observed resonance at ... more A polarization test is applied to determine the spin and the parity of the observed resonance at LHC, which is believed to be the expected "Higgs" particle. The test is based on very general principles and is completely independent of dynamical assumptions. We have also identified a set of observables that discriminate resonances with JP=0+,0−,2−J^P=0^+,0^-, 2^-JP=0+,0−,2− and 2+2^+2+. Furthermore, the same set can be used to gain useful and important information on the magnitude of each helicity amplitude contributing to the ggrightarrowgammagammagg\rightarrow \gamma\gammaggrightarrowgammagamma process .
Physical Review D, Aug 1, 1994
The valon model description of the proton is used to calculate contributions of the constituents ... more The valon model description of the proton is used to calculate contributions of the constituents of the proton to its spin. It is shown that the results of the model calculation agree rather well with the EMC results. It is conjectured that in probing the nucleon with high Q2 one actually probes its valon structure. It is further conjectured that the valence quark contribution to the proton spin cancels out the sea contribution, and gluons almost exclusively carry the spin of the proton. Our results satisfy various theoretical constraints on the sea polarization.
Phys Rev D, 1995
We describe the nucleon as a bound state of three constituent objects, called ``valons,'' which t... more We describe the nucleon as a bound state of three constituent objects, called ``valons,'' which themselves have structure. At high enough Q2 it is the valon structure, governed by QCD, which is probed and, thus, the nucleon structure is described in terms of its partonic distributions, while at low Q2 the nucleon is described in terms of its valon distributions, independent of a probe and controlled by nonperturbative QCD. The implications of this phenomenological model, then, are applied to the New Muon Collaboration (NMC) data for Fn2/Fp2 and on the Gottfried sum rule. It is shown that the model successfully reproduces the experimental value of the Gottfried sum rule SG[0<=x1,=4 GeV2]=0.243, consistent with the experimental results as well as the ratio Fn2/Fp2 down to the lowest x value.
Mathematical Physics, Apr 1, 2005
It is shown that there is a basic structure common to all hadrons, which is generated perturbativ... more It is shown that there is a basic structure common to all hadrons, which is generated perturbatively in QCD. Basically, it is a valence quark with its own cloud of quarks and gluons, a quasi-particle that we will call it a valon. In the valon representation, structure functions of nucleon and pion are calculated and is shown that there is an excellent agreement between the data and the model results in a wide range of kinematics. Calculation of the polarized structure functions also shows that there is a sizeable orbital angular momentum contribution to the spin of a valon coming from the partonic cloud.
The structure of a dressed quark is utilized to evaluate the structure function of proton and pio... more The structure of a dressed quark is utilized to evaluate the structure function of proton and pion. It is found that there is a simple relationship between F2pF_{2}^{p}F2p and F2piF_{2}^{\pi}F2pi. The ambiguity in the normalization of F2piF_{2}^{\pi}F2pi is discussed. Furthermore, the polarization structure function of the constituent (dressed) quark is calculated in the leading order. While, it does produce all the available data on polarized hadronic structure, it requires a significant contribution to the proton spin from the orbital angular momentum.
Physical review D: Particles and fields, 1995
ABSTRACT We describe the nucleon as a bound state of three constituent objects, called ‘‘valons,’... more ABSTRACT We describe the nucleon as a bound state of three constituent objects, called ‘‘valons,’’ which themselves have structure. At high enough Q2 it is the valon structure, governed by QCD, which is probed and, thus, the nucleon structure is described in terms of its partonic distributions, while at low Q2 the nucleon is described in terms of its valon distributions, independent of a probe and controlled by nonperturbative QCD. The implications of this phenomenological model, then, are applied to the New Muon Collaboration (NMC) data for F2n/F2p and on the Gottfried sum rule. It is shown that the model successfully reproduces the experimental value of the Gottfried sum rule SG[0≤x1,〈Q2〉=4 GeV2]=0.243, consistent with the experimental results as well as the ratio F2n/F2p down to the lowest x value.
In this dissertation we have utilized polarization phenomena in particle reactions to study the r... more In this dissertation we have utilized polarization phenomena in particle reactions to study the revealing features of the reaction. First, it is shown that it is impossible to design a non-dynamical null-experiment to test the time-reversal invariant. Second, the optimal formalism representation is used to determine proton-proton elastic scattering amplitudes at 579 MeV and 800 MeV. It is shown that, despite an extensive set of data at 579 MeV, the resulting amplitudes have a four-fold ambiguity. At 800 MeV, however, we managed to obtain a unique solution. Thirdly, the polarization structure of two-body reaction in a collinear configuration is investigated, and it is demonstrated that the structure becomes much simpler than it was for the general configuration. It is shown that in a collinear reaction all observables in which only one particle is polarized vanish. The results of this study are also applicable to all models in which helicity conservation holds, since they are formall...
Physical Review D, 1994
Proton spin in the valon model. Firooz Arash Centre for Theoretical Physics and Mathematics, Atom... more Proton spin in the valon model. Firooz Arash Centre for Theoretical Physics and Mathematics, Atomic Energy Organization of Iran (AEOI), PO Box 11365-8486, Tehran, Iran and Physics Department, Amir Kabir University of Technology, Hafez Avenue, Tehran, Iran. ...
Nuclear Physics B - Proceedings Supplements, 2005
AIP Conference Proceedings, 2009
We use the so‐called valon model, to describe the spin structure of the nucleon. We show that abo... more We use the so‐called valon model, to describe the spin structure of the nucleon. We show that about 40% of the nucleon spin is carried by the polarized valence quarks. The remaining part comes from the gluon polarization and the orbital angular momentum. It is shown that the ...
AIP Conference Proceedings, 2007
Polarized Structure Function of Nucleon and Orbital Angular Momentum. [AIP Conference Proceedings... more Polarized Structure Function of Nucleon and Orbital Angular Momentum. [AIP Conference Proceedings 915, 470 (2007)]. Firooz Arash, Fatemeh Taghavi‐Shahri. Abstract. We have utilized the concept of valon model to calculate the spin structure function of a constituent quark. ...
We have improved and examined the applicability of the valon model where the structure of any had... more We have improved and examined the applicability of the valon model where the structure of any hadron is determined by the structure of its constituent quarks. Nucleon structure functions are calculated within this model in the Next-to-Leading order. The results compare well with the experimental data. The model handles the bound state problem and the calculations show a flat or almost flat behavior for F2F_{2}F2 which sets in at some region of xleq10−5x\leq 10^{-5}xleq10−5at fixed Q2Q^{2}Q2. The emergence of this behavior is a consequence of the model and was not put in a priori as a theoretical guess. It seems that such a flatness can be inferred from HERA data, although, not completely confirmed yet. A set of parton distributions are given and their evolutions are tested. Some qualitative implications of the model for the spin structure of the proton is discussed.
We have used the notion of the constituent quark model of nucleon, where a constituent quark carr... more We have used the notion of the constituent quark model of nucleon, where a constituent quark carries its own internal structure, and applied it to determine nuclear structure functions ratios. It is found that the description of experimental data require the inclusion of strong shadowing effect for x<0.01x<0.01x<0.01. Using the idea of vector meson dominance model and other ingredients this effect is calculated in the context of the constituent quark model. It is rather striking that the constituent quark model, used here, gives a good account of the data for a wide range of atomic mass number from A=4 to A=204.
Physical Review C Nuclear Physics, 2010
The spin dependent structure function, g2ww(x,Q^2), is calculated in the valon model. A simple ap... more The spin dependent structure function, g2ww(x,Q^2), is calculated in the valon model. A simple approach is given for the determination of the twist-3 part of the g2(x, Q^2) in Mellin space; thus, enabling us to obtain the full transverse structure function, g2(x, Q^2) for proton, neutron and the deuteron. In light of the new data, we have further calculated the transversely polarized structure function of g23He(x, Q^2). Our results are checked against the experimental data and nice agreements are observed.
Phys Lett B, 2003
Partonic structure of constituent quark (or valon) in the next-to-leading order is used to calcul... more Partonic structure of constituent quark (or valon) in the next-to-leading order is used to calculate pion structure function. This is a further demonstration of the finding that the constituent quark structure is universal, and once it is calculated, the structure of any hadron can be predicted thereafter, using a convolution method, without introducing any new free parameter. The results are compared with the pion structure function from ZEUS Collaboration leading neutron production in e+p collisions at HERA. We found good agreement with the experiment. A resolution for the issue of normalization of the experimental data is suggested. In addition, the proportionality of F2pi and F2p, which have caused confusion in the normalization of ZEUS data is discussed and resolved.
A polarization test is applied to determine the spin and the parity of the observed resonance at ... more A polarization test is applied to determine the spin and the parity of the observed resonance at LHC, which is believed to be the expected "Higgs" particle. The test is based on very general principles and is completely independent of dynamical assumptions. We have also identified a set of observables that discriminate resonances with JP=0+,0−,2−J^P=0^+,0^-, 2^-JP=0+,0−,2− and 2+2^+2+. Furthermore, the same set can be used to gain useful and important information on the magnitude of each helicity amplitude contributing to the ggrightarrowgammagammagg\rightarrow \gamma\gammaggrightarrowgammagamma process .
Physical Review D, Aug 1, 1994
The valon model description of the proton is used to calculate contributions of the constituents ... more The valon model description of the proton is used to calculate contributions of the constituents of the proton to its spin. It is shown that the results of the model calculation agree rather well with the EMC results. It is conjectured that in probing the nucleon with high Q2 one actually probes its valon structure. It is further conjectured that the valence quark contribution to the proton spin cancels out the sea contribution, and gluons almost exclusively carry the spin of the proton. Our results satisfy various theoretical constraints on the sea polarization.
Phys Rev D, 1995
We describe the nucleon as a bound state of three constituent objects, called ``valons,'' which t... more We describe the nucleon as a bound state of three constituent objects, called ``valons,'' which themselves have structure. At high enough Q2 it is the valon structure, governed by QCD, which is probed and, thus, the nucleon structure is described in terms of its partonic distributions, while at low Q2 the nucleon is described in terms of its valon distributions, independent of a probe and controlled by nonperturbative QCD. The implications of this phenomenological model, then, are applied to the New Muon Collaboration (NMC) data for Fn2/Fp2 and on the Gottfried sum rule. It is shown that the model successfully reproduces the experimental value of the Gottfried sum rule SG[0<=x1,=4 GeV2]=0.243, consistent with the experimental results as well as the ratio Fn2/Fp2 down to the lowest x value.
Mathematical Physics, Apr 1, 2005
It is shown that there is a basic structure common to all hadrons, which is generated perturbativ... more It is shown that there is a basic structure common to all hadrons, which is generated perturbatively in QCD. Basically, it is a valence quark with its own cloud of quarks and gluons, a quasi-particle that we will call it a valon. In the valon representation, structure functions of nucleon and pion are calculated and is shown that there is an excellent agreement between the data and the model results in a wide range of kinematics. Calculation of the polarized structure functions also shows that there is a sizeable orbital angular momentum contribution to the spin of a valon coming from the partonic cloud.
The structure of a dressed quark is utilized to evaluate the structure function of proton and pio... more The structure of a dressed quark is utilized to evaluate the structure function of proton and pion. It is found that there is a simple relationship between F2pF_{2}^{p}F2p and F2piF_{2}^{\pi}F2pi. The ambiguity in the normalization of F2piF_{2}^{\pi}F2pi is discussed. Furthermore, the polarization structure function of the constituent (dressed) quark is calculated in the leading order. While, it does produce all the available data on polarized hadronic structure, it requires a significant contribution to the proton spin from the orbital angular momentum.
Physical review D: Particles and fields, 1995
ABSTRACT We describe the nucleon as a bound state of three constituent objects, called ‘‘valons,’... more ABSTRACT We describe the nucleon as a bound state of three constituent objects, called ‘‘valons,’’ which themselves have structure. At high enough Q2 it is the valon structure, governed by QCD, which is probed and, thus, the nucleon structure is described in terms of its partonic distributions, while at low Q2 the nucleon is described in terms of its valon distributions, independent of a probe and controlled by nonperturbative QCD. The implications of this phenomenological model, then, are applied to the New Muon Collaboration (NMC) data for F2n/F2p and on the Gottfried sum rule. It is shown that the model successfully reproduces the experimental value of the Gottfried sum rule SG[0≤x1,〈Q2〉=4 GeV2]=0.243, consistent with the experimental results as well as the ratio F2n/F2p down to the lowest x value.
In this dissertation we have utilized polarization phenomena in particle reactions to study the r... more In this dissertation we have utilized polarization phenomena in particle reactions to study the revealing features of the reaction. First, it is shown that it is impossible to design a non-dynamical null-experiment to test the time-reversal invariant. Second, the optimal formalism representation is used to determine proton-proton elastic scattering amplitudes at 579 MeV and 800 MeV. It is shown that, despite an extensive set of data at 579 MeV, the resulting amplitudes have a four-fold ambiguity. At 800 MeV, however, we managed to obtain a unique solution. Thirdly, the polarization structure of two-body reaction in a collinear configuration is investigated, and it is demonstrated that the structure becomes much simpler than it was for the general configuration. It is shown that in a collinear reaction all observables in which only one particle is polarized vanish. The results of this study are also applicable to all models in which helicity conservation holds, since they are formall...
Physical Review D, 1994
Proton spin in the valon model. Firooz Arash Centre for Theoretical Physics and Mathematics, Atom... more Proton spin in the valon model. Firooz Arash Centre for Theoretical Physics and Mathematics, Atomic Energy Organization of Iran (AEOI), PO Box 11365-8486, Tehran, Iran and Physics Department, Amir Kabir University of Technology, Hafez Avenue, Tehran, Iran. ...
Nuclear Physics B - Proceedings Supplements, 2005
AIP Conference Proceedings, 2009
We use the so‐called valon model, to describe the spin structure of the nucleon. We show that abo... more We use the so‐called valon model, to describe the spin structure of the nucleon. We show that about 40% of the nucleon spin is carried by the polarized valence quarks. The remaining part comes from the gluon polarization and the orbital angular momentum. It is shown that the ...
AIP Conference Proceedings, 2007
Polarized Structure Function of Nucleon and Orbital Angular Momentum. [AIP Conference Proceedings... more Polarized Structure Function of Nucleon and Orbital Angular Momentum. [AIP Conference Proceedings 915, 470 (2007)]. Firooz Arash, Fatemeh Taghavi‐Shahri. Abstract. We have utilized the concept of valon model to calculate the spin structure function of a constituent quark. ...
We have improved and examined the applicability of the valon model where the structure of any had... more We have improved and examined the applicability of the valon model where the structure of any hadron is determined by the structure of its constituent quarks. Nucleon structure functions are calculated within this model in the Next-to-Leading order. The results compare well with the experimental data. The model handles the bound state problem and the calculations show a flat or almost flat behavior for F2F_{2}F2 which sets in at some region of xleq10−5x\leq 10^{-5}xleq10−5at fixed Q2Q^{2}Q2. The emergence of this behavior is a consequence of the model and was not put in a priori as a theoretical guess. It seems that such a flatness can be inferred from HERA data, although, not completely confirmed yet. A set of parton distributions are given and their evolutions are tested. Some qualitative implications of the model for the spin structure of the proton is discussed.
We have used the notion of the constituent quark model of nucleon, where a constituent quark carr... more We have used the notion of the constituent quark model of nucleon, where a constituent quark carries its own internal structure, and applied it to determine nuclear structure functions ratios. It is found that the description of experimental data require the inclusion of strong shadowing effect for x<0.01x<0.01x<0.01. Using the idea of vector meson dominance model and other ingredients this effect is calculated in the context of the constituent quark model. It is rather striking that the constituent quark model, used here, gives a good account of the data for a wide range of atomic mass number from A=4 to A=204.
Physical Review C Nuclear Physics, 2010
The spin dependent structure function, g2ww(x,Q^2), is calculated in the valon model. A simple ap... more The spin dependent structure function, g2ww(x,Q^2), is calculated in the valon model. A simple approach is given for the determination of the twist-3 part of the g2(x, Q^2) in Mellin space; thus, enabling us to obtain the full transverse structure function, g2(x, Q^2) for proton, neutron and the deuteron. In light of the new data, we have further calculated the transversely polarized structure function of g23He(x, Q^2). Our results are checked against the experimental data and nice agreements are observed.