We perform a general computational analysis of possible post-collision mass distributions in high... more We perform a general computational analysis of possible post-collision mass distributions in high-speed galaxy cluster collisions in the presence of self-interacting dark matter. Using this analysis, we show that astrophysically weakly self-interacting dark matter can impart subtle yet measurable features in the mass distributions of colliding galaxy clusters even without significant disruptions to the dark matter halos of the colliding galaxy clusters themselves. Most profound such evidence is found to reside in the tails of dark matter halos' distributions, in the space between the colliding galaxy clusters. Such features appear in our simulations as shells of scattered dark matter expanding in alignment with the outgoing original galaxy clusters, contributing significant densities to projected mass distributions at large distances from collision centers and large scattering angles of up to 90 •. Our simulations indicate that as much as 20% of the total collision's mass may be deposited into such structures without noticeable disruptions to the main galaxy clusters. Such structures at large scattering angles are forbidden in purely gravitational high-speed galaxy cluster collisions. Convincing identification of such structures in real colliding galaxy clusters would be a clear indication of the self-interacting nature of dark matter. Our findings may offer an explanation for the ring-like dark matter feature recently identified in the long-range reconstructions of the mass distribution of the colliding galaxy cluster CL0024+017.
Page 1. PHYSICAL REVIEW C VOLUME 48, NUMBER 3 SEPTEMBER 1993 Kinematically accessible vector meso... more Page 1. PHYSICAL REVIEW C VOLUME 48, NUMBER 3 SEPTEMBER 1993 Kinematically accessible vector meson res@nance enhancements in p(R, e+e )A, Z, A(1405) Robert A. Williams, Chueng-Ryong Ji, and Stephen ...
We analyze the high energy cross sections and spin asymmetry of pseudoscalar and vector meson pai... more We analyze the high energy cross sections and spin asymmetry of pseudoscalar and vector meson pair production in two photon annihilation, using perturbative QCD (PQCD). For the neutral meson pair production the PQCD result is compared to the Pomeron exchange contribution, for which we consider both the two-gluon Pomeron model and the phenomenological Pomeron. The dominance of each contribution is
For the inclusive production process of heavy pseudoscalar and vector mesons in e+e- annihilation... more For the inclusive production process of heavy pseudoscalar and vector mesons in e+e- annihilation, we have improved the analytic calculation of the fragmentation function of heavy quarks up to tau2ln(tau2) where tau2=4m2/s, m is the meson mass, and s is the square of the total c.m. energy.
By resorting to previous results on flavor mixing in Quantum Field Theory, we show how to consist... more By resorting to previous results on flavor mixing in Quantum Field Theory, we show how to consistently define flavor states of mixed neutrinos as eigenstates of the flavor charge operators.
We discuss flavor charges and states for interacting mixed neutrinos in QFT. We show that the Pon... more We discuss flavor charges and states for interacting mixed neutrinos in QFT. We show that the Pontecorvo states are not eigenstates of the flavor charges. This implies that their use in describing the flavor neutrinos produces a violation of lepton charge conservation in the production/detection vertices. The flavor states defined as eigenstates of the flavor charges give the correct representation of mixed neutrinos in charged current weak interaction processes.
Proceedings of QCD Evolution 2017 — PoS(QCDEV2017)
We discuss the interface between the current theoretical framework based on generalized parton di... more We discuss the interface between the current theoretical framework based on generalized parton distributions (GPDs) and experimental measurements of deeply virtual Compton scattering (DVCS) observables. We point out that the theoretical framework of GPDs relying on handbag dominance is not sufficient to cover the kinematic region of DVCS experiment with the 12 GeV upgrade at Jefferson Lab. For the general theoretical framework to cover the current and future DVCS experiments, we propose the method of finding the most general hadronic tensor structure with the Lorentz and gauge invariant Compton form factors (CFFs).
The importance and usefulness of crossing is emphasized for both kaon scattering and kaon product... more The importance and usefulness of crossing is emphasized for both kaon scattering and kaon production reactions. It is argued, and numerically demonstrated for a chiral Lagrangian, that crossing provides powerful, comprehensive constraints which are often neglected in the evaluation of dynamical models. Cross section calculations are presented for two distinct sets of crossing related reactions: (1) K-p-->K-p, K+p-->K+p and p¯p-->K-K+ (2) K-p-->gammaLambda and gammap-->K+Lambda. The crossing relations require that the same hadronic Lagrangian, including coupling constants, govern all of these reactions, and results show that different reactions exhibit different sensitivity to coupling constant uncertainty. Because crossed reactions always entail different kinematic regions of the S matrix, it is expected that such sensitivity is not just representative of the current model but rather a general feature that should be exploited when investigating all relativistic theories.
Proceedings of QCD Evolution 2016 — PoS(QCDEV2016), Feb 10, 2017
We refine the computation of thed −ū flavor asymmetry in the proton sea with a complementary effo... more We refine the computation of thed −ū flavor asymmetry in the proton sea with a complementary effort to reveal the dynamics of pion exchange in high-energy processes. In particular, we discuss the efficacy of pion exchange models to simultaneously describe leading neutron electroproduction at HERA along with thed −ū flavor asymmetry in the proton. A detailed χ 2 analysis of the ZEUS and H1 cross sections, when combined with constraints on the pion flux from Drell-Yan data, allows regions of applicability of one-pion exchange to be delineated. The analysis disfavors several models of the pion flux used in the literature, and yields an improved extraction of the pion structure function and its uncertainties at parton momentum fractions in the pion of 4 × 10 −4 x π 0.05 at a scale of Q 2 = 10 GeV 2. Based on the fit results, we also address a possible estimate for leading proton structure functions in upcoming tagged deep-inelastic scattering experiments at Jefferson Lab on the deuteron with forward protons.
PROCEEDINGS OF THE 15TH INTERNATIONAL CONFERENCE ON MESON-NUCLEON PHYSICS AND THE STRUCTURE OF THE NUCLEON
The two-dimensional quantum chromodynamics (QCD 2) in the limit of infinite number of colors, kno... more The two-dimensional quantum chromodynamics (QCD 2) in the limit of infinite number of colors, known as 't Hooft model, was originally formulated in the Light Front Dynamics (LFD). The theory is exactly solvable, while still bearing some resemblance to the four-dimensional real world QCD in aspects such as confinement and m ass g ap, as well as the spontaneous breaking of chiral symmetry. The work in the Instant Form Dynamics (IFD) was done in 1978 by Bars and Green. The quarkantiquark bound state equation was derived and solved in each of the two forms, i.e., 't Hooft equation and Bars-Green equations, respectively, and they give the same discrete meson mass spectrum independent of the quantization form as expected. Introducing an interpolation angle parameter δ , in this work, we link the two distinct forms of dynamics, IFD and LFD, by letting the spacetime axes rotate from the ordinary equal-time form {t, x} to the light front form {x + , x − }, as δ varies from 0 to π/4. We unify the 't Hooft and Bars-Green equations into one formula, and by numerically solving it we confirm the independence of the meson mass spectra on the interpolation angle δ. We note that the quark condensate is quantization angle independent. This indicates a non-trivial vacuum structure even in the light-front form.
Proceedings of LIGHT CONE 2008 Relativistic Nuclear and Particle Physics — PoS(LC2008)
We discuss recent progress of light-front quark model (LFQM) phenomenology. In particular, we pre... more We discuss recent progress of light-front quark model (LFQM) phenomenology. In particular, we present the scalar glueball candidate from the LFQM analysis and the consistency of our result with the chiral suppression of the scalar glueball decay to a pair of quark and antiquark. Our LFQM also supports the recent findings from the AdS/QCD correspondence checking the dispersion relation for the timelike pion form factor.
We discuss the use of light-front field theory in the descriptions of hadrons. In particular, we ... more We discuss the use of light-front field theory in the descriptions of hadrons. In particular, we clarify the confusion in the prevailing notion of the equivalence between the infinite momentum frame and the light-front dynamics and the advantage of the lightfront dynamics in hadron physics. As an application, we present our recent work on the flavor asymmetry in the proton sea and identify the presence of the delta-function contributions associated with end-point singularities arising from the chiral effective theory calculation. The results pave the way for phenomenological applications of pion cloud models that are manifestly consistent with the chiral symmetry properties of QCD.
We construct a 3P0 light-front quark model wavefunction which is used to investigate various radi... more We construct a 3P0 light-front quark model wavefunction which is used to investigate various radiative scalar meson decays. Specifically, we look at decays involving f0(1370), f0(1500), and f0(1710) which are assumed to be glueball-qq mixtures, as well as a0(980) and f0(980) which are assumed to be qq. Although our results for the scalar mesons above 1 GeV are not inconsistent
We perform a general computational analysis of possible post-collision mass distributions in high... more We perform a general computational analysis of possible post-collision mass distributions in high-speed galaxy cluster collisions in the presence of self-interacting dark matter. Using this analysis, we show that astrophysically weakly self-interacting dark matter can impart subtle yet measurable features in the mass distributions of colliding galaxy clusters even without significant disruptions to the dark matter halos of the colliding galaxy clusters themselves. Most profound such evidence is found to reside in the tails of dark matter halos' distributions, in the space between the colliding galaxy clusters. Such features appear in our simulations as shells of scattered dark matter expanding in alignment with the outgoing original galaxy clusters, contributing significant densities to projected mass distributions at large distances from collision centers and large scattering angles of up to 90 •. Our simulations indicate that as much as 20% of the total collision's mass may be deposited into such structures without noticeable disruptions to the main galaxy clusters. Such structures at large scattering angles are forbidden in purely gravitational high-speed galaxy cluster collisions. Convincing identification of such structures in real colliding galaxy clusters would be a clear indication of the self-interacting nature of dark matter. Our findings may offer an explanation for the ring-like dark matter feature recently identified in the long-range reconstructions of the mass distribution of the colliding galaxy cluster CL0024+017.
Page 1. PHYSICAL REVIEW C VOLUME 48, NUMBER 3 SEPTEMBER 1993 Kinematically accessible vector meso... more Page 1. PHYSICAL REVIEW C VOLUME 48, NUMBER 3 SEPTEMBER 1993 Kinematically accessible vector meson res@nance enhancements in p(R, e+e )A, Z, A(1405) Robert A. Williams, Chueng-Ryong Ji, and Stephen ...
We analyze the high energy cross sections and spin asymmetry of pseudoscalar and vector meson pai... more We analyze the high energy cross sections and spin asymmetry of pseudoscalar and vector meson pair production in two photon annihilation, using perturbative QCD (PQCD). For the neutral meson pair production the PQCD result is compared to the Pomeron exchange contribution, for which we consider both the two-gluon Pomeron model and the phenomenological Pomeron. The dominance of each contribution is
For the inclusive production process of heavy pseudoscalar and vector mesons in e+e- annihilation... more For the inclusive production process of heavy pseudoscalar and vector mesons in e+e- annihilation, we have improved the analytic calculation of the fragmentation function of heavy quarks up to tau2ln(tau2) where tau2=4m2/s, m is the meson mass, and s is the square of the total c.m. energy.
By resorting to previous results on flavor mixing in Quantum Field Theory, we show how to consist... more By resorting to previous results on flavor mixing in Quantum Field Theory, we show how to consistently define flavor states of mixed neutrinos as eigenstates of the flavor charge operators.
We discuss flavor charges and states for interacting mixed neutrinos in QFT. We show that the Pon... more We discuss flavor charges and states for interacting mixed neutrinos in QFT. We show that the Pontecorvo states are not eigenstates of the flavor charges. This implies that their use in describing the flavor neutrinos produces a violation of lepton charge conservation in the production/detection vertices. The flavor states defined as eigenstates of the flavor charges give the correct representation of mixed neutrinos in charged current weak interaction processes.
Proceedings of QCD Evolution 2017 — PoS(QCDEV2017)
We discuss the interface between the current theoretical framework based on generalized parton di... more We discuss the interface between the current theoretical framework based on generalized parton distributions (GPDs) and experimental measurements of deeply virtual Compton scattering (DVCS) observables. We point out that the theoretical framework of GPDs relying on handbag dominance is not sufficient to cover the kinematic region of DVCS experiment with the 12 GeV upgrade at Jefferson Lab. For the general theoretical framework to cover the current and future DVCS experiments, we propose the method of finding the most general hadronic tensor structure with the Lorentz and gauge invariant Compton form factors (CFFs).
The importance and usefulness of crossing is emphasized for both kaon scattering and kaon product... more The importance and usefulness of crossing is emphasized for both kaon scattering and kaon production reactions. It is argued, and numerically demonstrated for a chiral Lagrangian, that crossing provides powerful, comprehensive constraints which are often neglected in the evaluation of dynamical models. Cross section calculations are presented for two distinct sets of crossing related reactions: (1) K-p-->K-p, K+p-->K+p and p¯p-->K-K+ (2) K-p-->gammaLambda and gammap-->K+Lambda. The crossing relations require that the same hadronic Lagrangian, including coupling constants, govern all of these reactions, and results show that different reactions exhibit different sensitivity to coupling constant uncertainty. Because crossed reactions always entail different kinematic regions of the S matrix, it is expected that such sensitivity is not just representative of the current model but rather a general feature that should be exploited when investigating all relativistic theories.
Proceedings of QCD Evolution 2016 — PoS(QCDEV2016), Feb 10, 2017
We refine the computation of thed −ū flavor asymmetry in the proton sea with a complementary effo... more We refine the computation of thed −ū flavor asymmetry in the proton sea with a complementary effort to reveal the dynamics of pion exchange in high-energy processes. In particular, we discuss the efficacy of pion exchange models to simultaneously describe leading neutron electroproduction at HERA along with thed −ū flavor asymmetry in the proton. A detailed χ 2 analysis of the ZEUS and H1 cross sections, when combined with constraints on the pion flux from Drell-Yan data, allows regions of applicability of one-pion exchange to be delineated. The analysis disfavors several models of the pion flux used in the literature, and yields an improved extraction of the pion structure function and its uncertainties at parton momentum fractions in the pion of 4 × 10 −4 x π 0.05 at a scale of Q 2 = 10 GeV 2. Based on the fit results, we also address a possible estimate for leading proton structure functions in upcoming tagged deep-inelastic scattering experiments at Jefferson Lab on the deuteron with forward protons.
PROCEEDINGS OF THE 15TH INTERNATIONAL CONFERENCE ON MESON-NUCLEON PHYSICS AND THE STRUCTURE OF THE NUCLEON
The two-dimensional quantum chromodynamics (QCD 2) in the limit of infinite number of colors, kno... more The two-dimensional quantum chromodynamics (QCD 2) in the limit of infinite number of colors, known as 't Hooft model, was originally formulated in the Light Front Dynamics (LFD). The theory is exactly solvable, while still bearing some resemblance to the four-dimensional real world QCD in aspects such as confinement and m ass g ap, as well as the spontaneous breaking of chiral symmetry. The work in the Instant Form Dynamics (IFD) was done in 1978 by Bars and Green. The quarkantiquark bound state equation was derived and solved in each of the two forms, i.e., 't Hooft equation and Bars-Green equations, respectively, and they give the same discrete meson mass spectrum independent of the quantization form as expected. Introducing an interpolation angle parameter δ , in this work, we link the two distinct forms of dynamics, IFD and LFD, by letting the spacetime axes rotate from the ordinary equal-time form {t, x} to the light front form {x + , x − }, as δ varies from 0 to π/4. We unify the 't Hooft and Bars-Green equations into one formula, and by numerically solving it we confirm the independence of the meson mass spectra on the interpolation angle δ. We note that the quark condensate is quantization angle independent. This indicates a non-trivial vacuum structure even in the light-front form.
Proceedings of LIGHT CONE 2008 Relativistic Nuclear and Particle Physics — PoS(LC2008)
We discuss recent progress of light-front quark model (LFQM) phenomenology. In particular, we pre... more We discuss recent progress of light-front quark model (LFQM) phenomenology. In particular, we present the scalar glueball candidate from the LFQM analysis and the consistency of our result with the chiral suppression of the scalar glueball decay to a pair of quark and antiquark. Our LFQM also supports the recent findings from the AdS/QCD correspondence checking the dispersion relation for the timelike pion form factor.
We discuss the use of light-front field theory in the descriptions of hadrons. In particular, we ... more We discuss the use of light-front field theory in the descriptions of hadrons. In particular, we clarify the confusion in the prevailing notion of the equivalence between the infinite momentum frame and the light-front dynamics and the advantage of the lightfront dynamics in hadron physics. As an application, we present our recent work on the flavor asymmetry in the proton sea and identify the presence of the delta-function contributions associated with end-point singularities arising from the chiral effective theory calculation. The results pave the way for phenomenological applications of pion cloud models that are manifestly consistent with the chiral symmetry properties of QCD.
We construct a 3P0 light-front quark model wavefunction which is used to investigate various radi... more We construct a 3P0 light-front quark model wavefunction which is used to investigate various radiative scalar meson decays. Specifically, we look at decays involving f0(1370), f0(1500), and f0(1710) which are assumed to be glueball-qq mixtures, as well as a0(980) and f0(980) which are assumed to be qq. Although our results for the scalar mesons above 1 GeV are not inconsistent
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