We compare the twist-2 and twist-4 parton distributions both in integrated and unintegrated parton distributions. We find that when x decreases the difference between the twist-2 and twist-4 patton distributions becom...We compare the twist-2 and twist-4 parton distributions both in integrated and unintegrated parton distributions. We find that when x decreases the difference between the twist-2 and twist-4 patton distributions become obvious except for the valence quark distributions. We hope the future experiments may distinguish whether the twist-4 correction is needed or not and select a reasonable unintegrated parton distribution model展开更多
A new fit of the pion parton distribution functions is provided. Only valence quark distributions are used at a low evolution scale and are evolved with the modified Dokshitzer- Gribov-Lipatov-Altarelli-Parisi equatio...A new fit of the pion parton distribution functions is provided. Only valence quark distributions are used at a low evolution scale and are evolved with the modified Dokshitzer- Gribov-Lipatov-Altarelli-Parisi equation which is briefly introduced in this work, and the sea quark and gluon distributions are only generated by the quantum chromodynamics processes. We find that the patton distributions can explain the pion-nucleon experiments data well, and it can also be compared with the data from the leading neutron data of experiments at HERA. The momentum distributions among the partons are discussed and our results are consistent with some models.展开更多
We introduce the polarized valon distributions to describe the spin dependence of parton distributions.The polarized valon distributions in the proton and polarized parton distributions inside the valon can help to ob...We introduce the polarized valon distributions to describe the spin dependence of parton distributions.The polarized valon distributions in the proton and polarized parton distributions inside the valon can help to obtain polarized parton distribution in a proton. In order to be able to obtain the spin contribution of sea quarks, we need to improve the valon model We employ the Bernstein polynomial averages to obtain the unknown parameters which exist in our calculations. Our results for the polarized proton structure function, xg1p, are in good agreement with the experimental data for some values of Q2.展开更多
The parton rescattering effect on the charged hadron forward-backward multiplicity correlation in pp collisions at √s =200 GeV is studied by a parton and hadron cascade model, PACIAE, based on the PYTHIA model. The c...The parton rescattering effect on the charged hadron forward-backward multiplicity correlation in pp collisions at √s =200 GeV is studied by a parton and hadron cascade model, PACIAE, based on the PYTHIA model. The calculated multiplicity and pseudorapidity distribution of the final state charged hadrons are well compared with the experimental data. It is found that the final state charged hadron pseudorapidity distribution is different from the initial state charged partons. The parton rescattering effect on the charged hadron forward-backward multiplicity correlation increases with the increasing parton rescattering strength in the center pseudorapidity region （｜η｜ 〈 1）. However, this effect becomes weaker in the outer pseudorapidity region （｜η｜ 〉 1）.展开更多
In this paper,we calculate the scalar a_(0)(980)-meson leading-twist wave function by using the light-cone harmonic oscillator model(LCHO),where the model parameters are determined by fitting theξ-moments■of its lig...In this paper,we calculate the scalar a_(0)(980)-meson leading-twist wave function by using the light-cone harmonic oscillator model(LCHO),where the model parameters are determined by fitting theξ-moments■of its light-cone distribution amplitudes.Then,the a_(0)(980)-meson leading-twist light-cone distribution amplitudes with three different scalesζ=(1.0,2.0,5.2)Ge V are given.After constructing the relationship between the a_(0)(980)-meson leading-twist parton distribution functions/valence quark distribution function and its LCHO wave function,we exhibit the■(x,ζ)and■(x,ζ)with different scales.Furthermore,we also calculate the Mellin moments of the a_(0)(980)-meson’s valence quark distribution function■with n=(1,2,3),i.e.■=0.027,■=0.018 and■=0.013.Finally,the scale evolution for the ratio of the Mellin moments x■are presented.展开更多
Higgs boson production in association with heavy quarks is one of the most important discovery channels for Higgs particles in the Standard Model and its super-symmetric extension at the LHC pp collider. We review the...Higgs boson production in association with heavy quarks is one of the most important discovery channels for Higgs particles in the Standard Model and its super-symmetric extension at the LHC pp collider. We review the status of the Higgs boson studies, with particular emphasis on the case bbh and tth production. We present results for the total cross section at Large Hadron Collider (LHC) in both single and double parton scattering mechanism.展开更多
Off-shell characteristics of pion generalized parton distributions(GPDs)and transverse momentum dependent parton distributions(TMDs)are examined within the framework of the Nambu–Jona-Lasinio model.In our previous st...Off-shell characteristics of pion generalized parton distributions(GPDs)and transverse momentum dependent parton distributions(TMDs)are examined within the framework of the Nambu–Jona-Lasinio model.In our previous studies,we separately investigated the properties of on-shell pion GPDs and light-front wave functions.Comparing the differences between on-shell and off-shell pion GPDs is particularly intriguing becuase it enables us to explore the effects associated with off-shellness.The absence of crossing symmetry causes the moments of GPDs to incorporate odd powers of the skewness parameter,resulting in new off-shell form factors.Through our calculations,we derived correction functions that account for modifications in pion GPDs attributed to off-shell effects.Unlike their on-shell counterparts,certain properties break down in the off-shell scenario;for example,symmetry properties and polynomiality conditions may no longer hold.In addition,we evaluate off-shell TMDs and compare them with their on-shell equivalents while also investigating their dependence on k_(⊥) .展开更多
A model for the nuclear medium modification of parton densities is presented.The approach is based on a global analysis of available deep inelastic scattering data for different nuclear targets within the rescaling mo...A model for the nuclear medium modification of parton densities is presented.The approach is based on a global analysis of available deep inelastic scattering data for different nuclear targets within the rescaling model,combined with the effects of Fermi motion.The scale dependence is implemented through the DGLAP-evolved quark and gluon densities in a proton derived analytically at the leading order of QCD coupling.By fitting the rescaling parameters to experimental data on the ratio F^(2)^(A)(x,Q^(2))/F_(2)^(A′)(x,Q^(2))for several nuclear targets A and A',we obtain predictions for nuclear parton distributions,even for unmeasured nuclei.The effects of nuclear modifications are investigated with respect to the mass number A.We highlight distinct shadowing and antishadowing behaviors for gluons and quarks.展开更多
This study investigates the form factors and impact parameter space parton distribution functions of the p meson derived from the generalized parton distributions within the Nambu-Jona-Lasinio model framework,employin...This study investigates the form factors and impact parameter space parton distribution functions of the p meson derived from the generalized parton distributions within the Nambu-Jona-Lasinio model framework,employing a proper time regularization scheme.We compare the charge G_(C),magnetic G_(M),and quadrupole G_(Q) form factors with latice data.The dressed form factors,G_(C)^(D) and G_(M)^(D),exhibit good agreement with latice results;however,G_(Q)^(D) is found to be harder than what is observed in latice calculations.The Rosenbluth cross section for elastic electron scattering on a spin-one particle can be expressed through the structure functions A(Q^(2))and B(Q^(2)).Additionally,the tensor polarization T_(20)(Q^(2),θ)can also be formulated in terms of these form factors.We analyze the structure functions A(Q2),B(Q2)and tensor polarization function T2o(Q2,);our findings quantitatively align with predicted values across various limits.In impact parameter space,we examine parton distribution functions along with their dependence on longitudinal momentum fraction x and impact parameter b+.The width distributions in impact parameter space reveal that the range of the charge distribution q_(C)(x,b_(⊥)^(2))is the most extensive.In contrast,the transverse magnetic radius falls within a moderate range,while the quadrupole distribution q_(Q)(x,b_(⊥)^(2))demonstrates the narrowest extent.展开更多
Energetic quarks and gluons lose energy as they traverse the hot and dense medium created in high-energy heavy-ion collisions at the BNL Relativistic Heavy Ion Collider(RHIC)and CERN Large Hadron Collider(LHC).The nuc...Energetic quarks and gluons lose energy as they traverse the hot and dense medium created in high-energy heavy-ion collisions at the BNL Relativistic Heavy Ion Collider(RHIC)and CERN Large Hadron Collider(LHC).The nuclear modification factor(R_(AA))of leading particles quantifies parton energy loss in such collisions,with the particle spectrum in p+p collisions as a reference.Previous R_(AA) measurements at RHIC energies have revealed an approximately constant trend at high transverse momenta(PT),implying a scenario where parton energy loss,Δ_(PT),scales proportionally with PT,a feature naively expected from energy loss dynamics in elastic collisions.In this study,we investigate the LHC R_(AA) measurements that exhibit a pronounced pT dependence of R_(AA) for various particle species,and our analysis attributes this behavior to Δ_(PT) being approximately proportional to √PT.These distinct features are consistent with model calculations of dominant radiative energy loss dynamics at LHC,in contrast to the dominance of collisional energy loss at RHIC.Additionally,the linear increase of the fractional energy loss with medium density at different PT magnitudes affirms our previous empirical observation that the magnitude of the energy loss depends more strongly on the initial entropy density than the parton's path length through the medium.Implications on the dynamical scenarios of parton energy loss and future experimental investigations arealsodiscussed.展开更多
An important feature of quantum chromodynamics(QCD)is that the strong force grows as the distance between partons increases,which confines partons into hadrons,commonly known as QCD confinement.Perturbative QCD(pQCD)d...An important feature of quantum chromodynamics(QCD)is that the strong force grows as the distance between partons increases,which confines partons into hadrons,commonly known as QCD confinement.Perturbative QCD(pQCD)does not work at large distance,such as the length scale of a hadron,which is the regime of non-perturbative QCD.The detailed QCD mechanisms through which confinement occurs from partons to hadrons(usually known as hadronization),and how it manifests itself in partonic structure of hadrons(usually known as parton distribution),remain unresolved puzzles of first-principle QCD calculations.展开更多
Pion generalized parton distributions are calculated within the framework of the Nambu-Jona-Lasinio model using different regularization schemes,including the proper time regularization scheme,the three-dimensional(3D...Pion generalized parton distributions are calculated within the framework of the Nambu-Jona-Lasinio model using different regularization schemes,including the proper time regularization scheme,the three-dimensional(3D)momentum cutoff scheme,the four-dimensional momentum cutoff scheme,and the Pauli-Villars regularization scheme.Furthermore,we check the theoretical constraints of pion generalized parton distributions required by the symmetries of quantum chromodynamics in different regularization schemes.The diagrams of pion parton distribution functions are plotted,in addition,we evaluate the Mellin moments of generalized parton distributions,which are related to the electromagnetic and gravitational form factors of pion.Pion generalized parton distributions are continuous but not differential at x=±ξ,when considering the effect of the contact contribution term,generalized parton distributions become not continuous at x=±ξin all the four regularization schemes.Generalized parton distributions in impact parameter space are considered,the width distribution of u quark in the pion and the meansquared<b_(⊥)^(2)>πu are calculated.The light-front transverse-spin distributions are studied when quark polarized in the light-front-transverse+x direction,the transverse-spin density is no longer symmetric around(bx=0,by=0),the peaks shift to(bx=0,by>0),we compare the average transverse shift<b_(⊥)^(y)>1u and<b_(⊥)^(y)>2u in different regularization schemes.The light-cone energy radius rE,LC and the light-cone charge radius rc,LC are also evaluated,we found that in the proper time regularization scheme the values of these quantities were the largest,in the 3 D momentum cutoff scheme they were the smallest.展开更多
Parton physics,when formulated as light-front correlations,are difficult to study non-perturbatively,despite the promise of lightfront quantization.Recently an alternative approach to partons have been proposed by re-...Parton physics,when formulated as light-front correlations,are difficult to study non-perturbatively,despite the promise of lightfront quantization.Recently an alternative approach to partons have been proposed by re-visiting original Feynman picture of a hadron moving at asymptotically large momentum.Here I formulate the approach in the language of an effective field theory for a large hadron momentum P in lattice QCD,LaMET for short.I show that using this new effective theory,parton properties,including light-front parton wave functions,can be extracted from lattice observables in a systematic expansion of 1/P,much like that the parton distributions can be extracted from the hard scattering data at momentum scales of a few GeV.展开更多
A symmetry-preserving continuum approach to the two valence-body bound-state problem is used to calculate the valence, glue and sea distributions within the pion; unifying them with, inter alia, electromagnetic pion e...A symmetry-preserving continuum approach to the two valence-body bound-state problem is used to calculate the valence, glue and sea distributions within the pion; unifying them with, inter alia, electromagnetic pion elastic and transition form factors. The analysis reveals the following momentum fractions at the scale ζ2:= 2GeV :〈xvalence〉 = 0.48（3）, 〈xglue〉 = 0.41（2）, 〈xsea〉 = 0.11（2）;and despite hardening induced by the emergent phenomenon of dynamical chiral symmetry breaking, the valence-quark distribution function, qπ（x）, exhibits the x ≈ 1 behaviour predicted by quantum chromodynamics（QCD）. After evolution to o ζ = 5.2 GeV, the prediction for qπ（x） matches that obtained using lattice-regularised QCD. This confluence should both stimulate improved analyses of existing data and aid in planning efforts to obtain new data on the pion distribution functions.展开更多
A systematic study on the impact of widely-used nuclear-modified parton distribution function(nPDF)parameterizations on the production of direct photons and charged hadrons is performed by employing a next-toleading o...A systematic study on the impact of widely-used nuclear-modified parton distribution function(nPDF)parameterizations on the production of direct photons and charged hadrons is performed by employing a next-toleading order Monte Carlo event generator JETPHOX in hadronic collisions at LHC energies.The nuclear modification factors of photon and charged hadron productions are studied in three types of collision systems,i.e.,small(p+p and p+Pb),medium(O+O),and large(Pb+Pb),in a wide rapidity acceptance.The results illustrate that the direct photon production process is a sensitive probe to decipher the difference of the nPDF parameterization implementations,which provides new insights for the experimental measurements to refine the nuclear modifications of the parton distributions.To provide a benchmark for searching for quark gluon plasma in the upcoming small system measurements at LHC energies,we carry out detailed studies on the cold nuclear matter effect in(O+O)collisions.Our outcomes show that the cold nuclear matter effects are negligible for the charged hadron production in(O+O)collisions,which can be used as a baseline to subtract the initial state contribution.展开更多
The precision study of W^-W^+H production with subsequent W^±→l^±vl^(-)and H→bb decays at the Large Hadron Collider(LHC)aids in the investigation of Higgs gauge couplings and the search for new physics bey...The precision study of W^-W^+H production with subsequent W^±→l^±vl^(-)and H→bb decays at the Large Hadron Collider(LHC)aids in the investigation of Higgs gauge couplings and the search for new physics beyond the standard model.In this study,we calculate the shower-matched next-to-leading order QCD and electroweak(EW)corrections from the qq annihilation and photon-induced channels to the W^-W^+H production at the 14 TeV LHC.We deal with the subsequent decays of Higgs and W^±bosons by adopting the MADSPIN method.Both the integrated cross section and some kinematic distributions of W^±,H,and their decay products are provided.We find that the QCD correction significantly enhances the leading-order differential cross section,while the EW correction from the qq annihilation channel obviously suppresses it,especially in the high energy phase-space region,due to the Sudakov effect.The qy-and yy-induced relative corrections are positive and insensitive to the transverse momenta of W^±,H,and their decay products.These photon-induced corrections compensate the negative qq-initiated EW correction,and become the dominant EW contribution as the increment of the pp colliding energy.The parton shower(PS)effects on kinematic distributions are not negligible.The relative PS correction to the b-jet transverse momentum distribution can exceed 100%in the high p_(T,b)region.Moreover,we investigate the scale and PDF uncertainties,and find that the theoretical error of the QCD+EW+qγ+γγ-corrected integrated cross section mainly originates from the renormalization scale dependence of the QCD correction.展开更多
The recent measurement of the differential γ ＋ c-jet cross section, performed at the Tevatron collider in Run II by the D0 collaboration, is studied in a next-to-leading order（NLO） global QCD analysis to assess it...The recent measurement of the differential γ ＋ c-jet cross section, performed at the Tevatron collider in Run II by the D0 collaboration, is studied in a next-to-leading order（NLO） global QCD analysis to assess its impact on the proton parton distribution functions（PDFs）. We show that these data lead to a significant change in the gluon and charm quark distributions. We demonstrate also that there is an inconsistency between the new high precision HERA I＋II combined data and Tevatron measurement. Moreover, in this study we investigate the impact of older EMC measurements of charm structure function F_c^2 on the PDFs and compare the results with those from the analysis of Tevatron data. We show that both of them have the same impact on the PDFs, and thus can be recognized as the same evidence for the inefficiency of perturbative QCD in dealing with charm production in some kinematic regions.展开更多
Jet quenching has been proposed as a probe of the properties of the strongly interacting quarkgluon-plasma in high energy heavy ion collisions.At the meantime,it is also important to study the excitation of medium by ...Jet quenching has been proposed as a probe of the properties of the strongly interacting quarkgluon-plasma in high energy heavy ion collisions.At the meantime,it is also important to study the excitation of medium by propagating jets.Based on Boltzmann equation,a Monte Carlo was constructed to simulate the elastic collisions with thermal partons by energetic jets.Medium modification due to jet-medium interaction has been studied within this model in a uniform medium.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No.10875044
文摘We compare the twist-2 and twist-4 parton distributions both in integrated and unintegrated parton distributions. We find that when x decreases the difference between the twist-2 and twist-4 patton distributions become obvious except for the valence quark distributions. We hope the future experiments may distinguish whether the twist-4 correction is needed or not and select a reasonable unintegrated parton distribution model
文摘A new fit of the pion parton distribution functions is provided. Only valence quark distributions are used at a low evolution scale and are evolved with the modified Dokshitzer- Gribov-Lipatov-Altarelli-Parisi equation which is briefly introduced in this work, and the sea quark and gluon distributions are only generated by the quantum chromodynamics processes. We find that the patton distributions can explain the pion-nucleon experiments data well, and it can also be compared with the data from the leading neutron data of experiments at HERA. The momentum distributions among the partons are discussed and our results are consistent with some models.
文摘We introduce the polarized valon distributions to describe the spin dependence of parton distributions.The polarized valon distributions in the proton and polarized parton distributions inside the valon can help to obtain polarized parton distribution in a proton. In order to be able to obtain the spin contribution of sea quarks, we need to improve the valon model We employ the Bernstein polynomial averages to obtain the unknown parameters which exist in our calculations. Our results for the polarized proton structure function, xg1p, are in good agreement with the experimental data for some values of Q2.
基金supported by National Natural Science Foundation of China (Nos. 11047142, 10975062, 11075217, and 10705012)
文摘The parton rescattering effect on the charged hadron forward-backward multiplicity correlation in pp collisions at √s =200 GeV is studied by a parton and hadron cascade model, PACIAE, based on the PYTHIA model. The calculated multiplicity and pseudorapidity distribution of the final state charged hadrons are well compared with the experimental data. It is found that the final state charged hadron pseudorapidity distribution is different from the initial state charged partons. The parton rescattering effect on the charged hadron forward-backward multiplicity correlation increases with the increasing parton rescattering strength in the center pseudorapidity region （｜η｜ 〈 1）. However, this effect becomes weaker in the outer pseudorapidity region （｜η｜ 〉 1）.
基金supported in part by the National Natural Science Foundation of China under Grant No.12265010,No.12265009the Project of Guizhou Provincial Department of Science and Technology under Grant No.ZK[2021]024the Project of Guizhou Provincial Department of Education under Grant No.KY[2021]030。
文摘In this paper,we calculate the scalar a_(0)(980)-meson leading-twist wave function by using the light-cone harmonic oscillator model(LCHO),where the model parameters are determined by fitting theξ-moments■of its light-cone distribution amplitudes.Then,the a_(0)(980)-meson leading-twist light-cone distribution amplitudes with three different scalesζ=(1.0,2.0,5.2)Ge V are given.After constructing the relationship between the a_(0)(980)-meson leading-twist parton distribution functions/valence quark distribution function and its LCHO wave function,we exhibit the■(x,ζ)and■(x,ζ)with different scales.Furthermore,we also calculate the Mellin moments of the a_(0)(980)-meson’s valence quark distribution function■with n=(1,2,3),i.e.■=0.027,■=0.018 and■=0.013.Finally,the scale evolution for the ratio of the Mellin moments x■are presented.
文摘Higgs boson production in association with heavy quarks is one of the most important discovery channels for Higgs particles in the Standard Model and its super-symmetric extension at the LHC pp collider. We review the status of the Higgs boson studies, with particular emphasis on the case bbh and tth production. We present results for the total cross section at Large Hadron Collider (LHC) in both single and double parton scattering mechanism.
基金Supported by the Scientific Research Foundation of Nanjing Institute of Technology(YKJ202352)the General Program of the Natural Science Foundation of Jiangsu Higher Education Institutions(25KJD140001)。
文摘Off-shell characteristics of pion generalized parton distributions(GPDs)and transverse momentum dependent parton distributions(TMDs)are examined within the framework of the Nambu–Jona-Lasinio model.In our previous studies,we separately investigated the properties of on-shell pion GPDs and light-front wave functions.Comparing the differences between on-shell and off-shell pion GPDs is particularly intriguing becuase it enables us to explore the effects associated with off-shellness.The absence of crossing symmetry causes the moments of GPDs to incorporate odd powers of the skewness parameter,resulting in new off-shell form factors.Through our calculations,we derived correction functions that account for modifications in pion GPDs attributed to off-shell effects.Unlike their on-shell counterparts,certain properties break down in the off-shell scenario;for example,symmetry properties and polynomiality conditions may no longer hold.In addition,we evaluate off-shell TMDs and compare them with their on-shell equivalents while also investigating their dependence on k_(⊥) .
文摘A model for the nuclear medium modification of parton densities is presented.The approach is based on a global analysis of available deep inelastic scattering data for different nuclear targets within the rescaling model,combined with the effects of Fermi motion.The scale dependence is implemented through the DGLAP-evolved quark and gluon densities in a proton derived analytically at the leading order of QCD coupling.By fitting the rescaling parameters to experimental data on the ratio F^(2)^(A)(x,Q^(2))/F_(2)^(A′)(x,Q^(2))for several nuclear targets A and A',we obtain predictions for nuclear parton distributions,even for unmeasured nuclei.The effects of nuclear modifications are investigated with respect to the mass number A.We highlight distinct shadowing and antishadowing behaviors for gluons and quarks.
基金Supported by the Scientific Research Foundation of Nanjing Institute of Technology(YKJ202352)the Natural Science Foundation of Jiangsu Province,China(BK20191472),and the China Postdoctoral Science Foundation(2022M721564)。
文摘This study investigates the form factors and impact parameter space parton distribution functions of the p meson derived from the generalized parton distributions within the Nambu-Jona-Lasinio model framework,employing a proper time regularization scheme.We compare the charge G_(C),magnetic G_(M),and quadrupole G_(Q) form factors with latice data.The dressed form factors,G_(C)^(D) and G_(M)^(D),exhibit good agreement with latice results;however,G_(Q)^(D) is found to be harder than what is observed in latice calculations.The Rosenbluth cross section for elastic electron scattering on a spin-one particle can be expressed through the structure functions A(Q^(2))and B(Q^(2)).Additionally,the tensor polarization T_(20)(Q^(2),θ)can also be formulated in terms of these form factors.We analyze the structure functions A(Q2),B(Q2)and tensor polarization function T2o(Q2,);our findings quantitatively align with predicted values across various limits.In impact parameter space,we examine parton distribution functions along with their dependence on longitudinal momentum fraction x and impact parameter b+.The width distributions in impact parameter space reveal that the range of the charge distribution q_(C)(x,b_(⊥)^(2))is the most extensive.In contrast,the transverse magnetic radius falls within a moderate range,while the quadrupole distribution q_(Q)(x,b_(⊥)^(2))demonstrates the narrowest extent.
基金supported by the U.S.Department of Energy(DE-FG02-88ER40424)by the National Natural Science Foundation of China(1835002)。
文摘Energetic quarks and gluons lose energy as they traverse the hot and dense medium created in high-energy heavy-ion collisions at the BNL Relativistic Heavy Ion Collider(RHIC)and CERN Large Hadron Collider(LHC).The nuclear modification factor(R_(AA))of leading particles quantifies parton energy loss in such collisions,with the particle spectrum in p+p collisions as a reference.Previous R_(AA) measurements at RHIC energies have revealed an approximately constant trend at high transverse momenta(PT),implying a scenario where parton energy loss,Δ_(PT),scales proportionally with PT,a feature naively expected from energy loss dynamics in elastic collisions.In this study,we investigate the LHC R_(AA) measurements that exhibit a pronounced pT dependence of R_(AA) for various particle species,and our analysis attributes this behavior to Δ_(PT) being approximately proportional to √PT.These distinct features are consistent with model calculations of dominant radiative energy loss dynamics at LHC,in contrast to the dominance of collisional energy loss at RHIC.Additionally,the linear increase of the fractional energy loss with medium density at different PT magnitudes affirms our previous empirical observation that the magnitude of the energy loss depends more strongly on the initial entropy density than the parton's path length through the medium.Implications on the dynamical scenarios of parton energy loss and future experimental investigations arealsodiscussed.
基金supported in part by the National Natural Science Foundation of China(No.12575145)the National Key Research and Development Program of China(No.2022YFA1604900)。
文摘An important feature of quantum chromodynamics(QCD)is that the strong force grows as the distance between partons increases,which confines partons into hadrons,commonly known as QCD confinement.Perturbative QCD(pQCD)does not work at large distance,such as the length scale of a hadron,which is the regime of non-perturbative QCD.The detailed QCD mechanisms through which confinement occurs from partons to hadrons(usually known as hadronization),and how it manifests itself in partonic structure of hadrons(usually known as parton distribution),remain unresolved puzzles of first-principle QCD calculations.
基金Supported by the National Natural Science Foundation of China(11775118)。
文摘Pion generalized parton distributions are calculated within the framework of the Nambu-Jona-Lasinio model using different regularization schemes,including the proper time regularization scheme,the three-dimensional(3D)momentum cutoff scheme,the four-dimensional momentum cutoff scheme,and the Pauli-Villars regularization scheme.Furthermore,we check the theoretical constraints of pion generalized parton distributions required by the symmetries of quantum chromodynamics in different regularization schemes.The diagrams of pion parton distribution functions are plotted,in addition,we evaluate the Mellin moments of generalized parton distributions,which are related to the electromagnetic and gravitational form factors of pion.Pion generalized parton distributions are continuous but not differential at x=±ξ,when considering the effect of the contact contribution term,generalized parton distributions become not continuous at x=±ξin all the four regularization schemes.Generalized parton distributions in impact parameter space are considered,the width distribution of u quark in the pion and the meansquared<b_(⊥)^(2)>πu are calculated.The light-front transverse-spin distributions are studied when quark polarized in the light-front-transverse+x direction,the transverse-spin density is no longer symmetric around(bx=0,by=0),the peaks shift to(bx=0,by>0),we compare the average transverse shift<b_(⊥)^(y)>1u and<b_(⊥)^(y)>2u in different regularization schemes.The light-cone energy radius rE,LC and the light-cone charge radius rc,LC are also evaluated,we found that in the proper time regularization scheme the values of these quantities were the largest,in the 3 D momentum cutoff scheme they were the smallest.
基金partially supported by the U.S.Department of Energy(Grant No.DE-FG02-93ER-40762)the Office of Science and Technology in Shanghai Municipal Government(Grant No.11DZ2260700)the National Natural Science Foundation of China(Grant No.11175114)
文摘Parton physics,when formulated as light-front correlations,are difficult to study non-perturbatively,despite the promise of lightfront quantization.Recently an alternative approach to partons have been proposed by re-visiting original Feynman picture of a hadron moving at asymptotically large momentum.Here I formulate the approach in the language of an effective field theory for a large hadron momentum P in lattice QCD,LaMET for short.I show that using this new effective theory,parton properties,including light-front parton wave functions,can be extracted from lattice observables in a systematic expansion of 1/P,much like that the parton distributions can be extracted from the hard scattering data at momentum scales of a few GeV.
基金Supported by the Chinese Government’s Thousand Talents Plan for Young ProfessionalsJiangsu Province Hundred Talents Plan for ProfessionalsForschungszentrum Jülich GmbH
文摘A symmetry-preserving continuum approach to the two valence-body bound-state problem is used to calculate the valence, glue and sea distributions within the pion; unifying them with, inter alia, electromagnetic pion elastic and transition form factors. The analysis reveals the following momentum fractions at the scale ζ2:= 2GeV :〈xvalence〉 = 0.48（3）, 〈xglue〉 = 0.41（2）, 〈xsea〉 = 0.11（2）;and despite hardening induced by the emergent phenomenon of dynamical chiral symmetry breaking, the valence-quark distribution function, qπ（x）, exhibits the x ≈ 1 behaviour predicted by quantum chromodynamics（QCD）. After evolution to o ζ = 5.2 GeV, the prediction for qπ（x） matches that obtained using lattice-regularised QCD. This confluence should both stimulate improved analyses of existing data and aid in planning efforts to obtain new data on the pion distribution functions.
基金Supported by the National Key Research and Development Program of China(2018YFE0104700,2018YFE0104800)the National Natural Science Foundation of China(12061141008,12175085)the Fundamental Research Funds for the Central Universities(CCNU220N003)
文摘A systematic study on the impact of widely-used nuclear-modified parton distribution function(nPDF)parameterizations on the production of direct photons and charged hadrons is performed by employing a next-toleading order Monte Carlo event generator JETPHOX in hadronic collisions at LHC energies.The nuclear modification factors of photon and charged hadron productions are studied in three types of collision systems,i.e.,small(p+p and p+Pb),medium(O+O),and large(Pb+Pb),in a wide rapidity acceptance.The results illustrate that the direct photon production process is a sensitive probe to decipher the difference of the nPDF parameterization implementations,which provides new insights for the experimental measurements to refine the nuclear modifications of the parton distributions.To provide a benchmark for searching for quark gluon plasma in the upcoming small system measurements at LHC energies,we carry out detailed studies on the cold nuclear matter effect in(O+O)collisions.Our outcomes show that the cold nuclear matter effects are negligible for the charged hadron production in(O+O)collisions,which can be used as a baseline to subtract the initial state contribution.
基金Supported in part by the National Natural Science Foundation of China(11775211 and 11535002)the Applied Basic Research Programs of Yunnan Provincial Science and Technology Department(2016FB008)the CAS Center for Excellence in Particle Physics(CCEPP)
文摘The precision study of W^-W^+H production with subsequent W^±→l^±vl^(-)and H→bb decays at the Large Hadron Collider(LHC)aids in the investigation of Higgs gauge couplings and the search for new physics beyond the standard model.In this study,we calculate the shower-matched next-to-leading order QCD and electroweak(EW)corrections from the qq annihilation and photon-induced channels to the W^-W^+H production at the 14 TeV LHC.We deal with the subsequent decays of Higgs and W^±bosons by adopting the MADSPIN method.Both the integrated cross section and some kinematic distributions of W^±,H,and their decay products are provided.We find that the QCD correction significantly enhances the leading-order differential cross section,while the EW correction from the qq annihilation channel obviously suppresses it,especially in the high energy phase-space region,due to the Sudakov effect.The qy-and yy-induced relative corrections are positive and insensitive to the transverse momenta of W^±,H,and their decay products.These photon-induced corrections compensate the negative qq-initiated EW correction,and become the dominant EW contribution as the increment of the pp colliding energy.The parton shower(PS)effects on kinematic distributions are not negligible.The relative PS correction to the b-jet transverse momentum distribution can exceed 100%in the high p_(T,b)region.Moreover,we investigate the scale and PDF uncertainties,and find that the theoretical error of the QCD+EW+qγ+γγ-corrected integrated cross section mainly originates from the renormalization scale dependence of the QCD correction.
文摘The recent measurement of the differential γ ＋ c-jet cross section, performed at the Tevatron collider in Run II by the D0 collaboration, is studied in a next-to-leading order（NLO） global QCD analysis to assess its impact on the proton parton distribution functions（PDFs）. We show that these data lead to a significant change in the gluon and charm quark distributions. We demonstrate also that there is an inconsistency between the new high precision HERA I＋II combined data and Tevatron measurement. Moreover, in this study we investigate the impact of older EMC measurements of charm structure function F_c^2 on the PDFs and compare the results with those from the analysis of Tevatron data. We show that both of them have the same impact on the PDFs, and thus can be recognized as the same evidence for the inefficiency of perturbative QCD in dealing with charm production in some kinematic regions.
基金Supported by National Natural Science Foundation of China (10975059)
文摘Jet quenching has been proposed as a probe of the properties of the strongly interacting quarkgluon-plasma in high energy heavy ion collisions.At the meantime,it is also important to study the excitation of medium by propagating jets.Based on Boltzmann equation,a Monte Carlo was constructed to simulate the elastic collisions with thermal partons by energetic jets.Medium modification due to jet-medium interaction has been studied within this model in a uniform medium.
