Parton Rescattering Effect on the Charged Hadron Forward-Backward Multiplicity Correlation in pp Collisions at s～(1/2)=200 GeV

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）.

Double Parton Scattering in Associate Higgs Boson Production with Heavy Quarks at the LHC

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.

QCD Predictions for Spin Dependence of Parton Distributions

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.

组分夸克模型中随Q^2演化的强子的Parton分布函数

用牛顿一拉夫逊方法求出了Q_0~2时价子中的Parton分布函数,且采用把微分积分方程组形式的QCD演化方程离散为常微分方程组的方法,求出了任意Q^2>Q_0~2时价子中的Paerton分布函数,最后通过卷积,得到了组分夸克模型中随Q^2演化的强子中的Parton分布函数。

Integrated and Unintegrated Parton Distributions

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 parton 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.

Reconstructing parton distribution function based on maximum entropy method

A new method based on the maximum entropy principle for reconstructing the parton distribution function(PDF)from moments is proposed.Unlike traditional methods,the new method does not require any artificial assumptions.For the case of moments with errors,we introduce Gaussian functions to soften the constraints of moments.Through a series of tests,the effectiveness and reconstruction efficiency of this new method are evaluated comprehensively,demonstrating that this method is reasonable and can achieve high-quality reconstruction with at least the first six moments as input.Finally,we select a set of lattice quantum chromodynamics(QCD)results regarding moments as input and provide reasonable reconstruction results for the pion.

Systematic studies on the nuclear parton distribution with photon and hadron productions in nuclear collisions at the LHC

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.

Searching for a_(0)(980)-meson parton distribution function

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.

Regularization dependence of pion generalized parton distributions

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.

Precision study of W^-W^+H production including parton shower effects at CERN Large Hadron Collider

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.

Uncertainty of parton distribution functions due to physical observables in a global analysis

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.

Drawing insights from pion parton distributions

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,q^π(x),exhibits the x≈1 behaviour predicted by quantum chromodynamics(QCD).After evolution to ζ=5.2 GeV,the prediction for q^π(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.

Effect of parton cascade to medium

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.

Parton distribution functions and nuclear EMC effect in a statistical model

A new and simple statistical approach is performed to calculate the parton distribution functions （PDFs） of the nucleon in terms of light-front kinematic variables.Analytic expressions of x-dependent PDFs are obtained in the whole x region.And thereafter,we treat the temperature T as a parameter of the atomic number A to explain the nuclear EMC effect in the region x ∈ [0.2,0.7].We give the predictions of PDF ratios,and they are very different from those by other models,thus experiments aiming at measuring PDF ratios are suggested to provide a discrimination of different models.

Production of γγ+2 jets from double parton scattering in proton-proton collisions at the LHC

Cross sections for the production of pairs of photons plus two additional jets produced from double parton scattering in high-energy proton-proton collisions at the LHC are calculated for the first time. The estimates are based on the theoretical perturbative QCD predictions for the productions of γγ at next-to-next-to-leading-order, jet＋jet and γ＋jet at next-to-leading-order, for their corresponding single-scattering cross sections. The cross sections and expected event rates for γγ＋2 jets from double parton scattering, after typical acceptance and selections, are given for proton-proton collisions with the collision energy s=13 TeV and integrated luminosity of 100 fb-1 planned for the following years, and also s=14 TeV with 3000 fb 1 of integrated luminosity as the LHC design.

Gaussian-weighted parton quasi-distribution(Lattice Parton Physics Project(LP^3))

Recent years have witnessed rapid progress in calculating parton distribution functions (PDFs), rather than just their moments, from lattice QCD [1-9]. The most remarkable aspect of such calculations is that one can connect appropriately chosen Euclidean correlation functions calculable on the lattice to PDFs through a perturbative matching relation. This can be understood in the framework of the large-momentum effective theory (LaMET)[10, 11].

Drell-Yan nuclear modification due to nuclear effects of nPDFs and initial-state parton energy loss

By globally analyzing nuclear Drell-Yan data including all incident energies,the nuclear effects of nuclear parton distribution functions(nPDFs)and initial-state parton energy loss are investigated.Based on the Landau-Pomeranchuk-Migdal(LPM)regime,the calculations are carried out by means of analytic parametrizations of quenching weights derived from the Baier-Dokshitzer-Mueller-Peigné-Schiff(BDMPS)formalism and using the new EPPS16 nPDFs.It is found that the results are in good agreement with the data and the role of the energy loss effect in the suppression of Drell-Yan ratios is prominent,especially for low-mass Drell-Yan measurements.Thenuclear effects of nPDFs become more obvious with increasing nuclear mass number A,the same as the energy loss effect.By a global fit,the transport coefficient extracted is q=0.26±0.04 GeV^(2)/fm.In addition,to avoid diminishing the QCD NLO correction to the data form of Drell-Yan ratios,separate calculations of the Compton differentialcross section ratios RFe(W)/C(xF)at 120 GeV are performed,which provides a feasible way to better distinguish the gluon energy loss in Compton scattering.It is found that the role of the initial-state gluon energy loss in the suppression of Compton scattering ratios is not very important and disappears with the increase of xF.

Pion parton distribution function in light-front holographic QCD

The valence-quark distribution function of the pion has been of interest for decades;particularly,the profile it should adopt when x→1(the large-x behavior)has been the subject of a long-standing debate.In the light-front holographic QCD(LFHQCD)approach,this behavior is controlled by the so-called reparametrization function,wτ(x),which is not fully determined from first principles.We show that,owing to the flexibility of wτ(x),the large-x profile u^π(x)∼(1−x)^2 can be contained within the LFHQCD formalism.This is in contrast to a previous LFHQCD study(Guy F.de Teramond et al.,Phys.Rev.Lett.,120(18),2018)in which u^π(x)∼(1−x)^1 was found instead.Given our observations,augmented by perturbative QCD and recent lattice QCD results,we state that the large-x exponent of“2”cannot be excluded.

Revealing pion and kaon structure via generalised parton distributions

Clear windows onto emergent hadron mass(EHM)and modulations thereof by Higgs boson interactions are provided by observable measures of pion and kaon structure,many of which are accessible via generalised parton distributions(GPDs).Beginning with algebraic GPD Ansätze,constrained entirely by hadron-scaleπand K valence-parton distribution functions(DFs),in whose forms both EHM and Higgs boson influences are manifest,numerous illustrations are provided.They include the properties of electromagnetic form factors,impact parameter space GPDs,gravitational form factors and associated pressure profiles,and the character and consequences of allorders evolution.The analyses predict that mass-squared gravitational form factors are stiffer than electromagnetic form factors;reveal that K pressure profiles are tighter than profiles,with both mesons sustaining near-core pressures at magnitudes similar to that expected at the core of neutron stars;deliver parameter-free predictions for and K valence,glue,and sea GPDs at the resolving scale l=2GeV;and predict that at this scale the fraction of meson mass-squared carried by glue and sea combined matches that lodged with the valence degrees-of-freedom,with a similar statement holding for mass-squared radii.

昂高:长期致力于色彩可持续性和创新解决方案——专访昂高酸性、分散及活性染料部门全球产品营销经理Keith Parton先生

在2016年第十六届中国国际染料工业及有机颜料、纺织化学品展览会(China Interdye 2016)展会现场,就昂高创新性的各项技术以及行业未来发展等问题,昂高酸性、分散及活性染料部门全球产品营销经理Keith Parton先生接受了《上海纺织科技》等行业著名媒体的专访。