We calculate the valence quark transverse momentum-dependent parton distributions (TMDs) of the lightest pseudoscalar meson, pions, in isospin asymmetric nuclear matter at zero temperature by employing a light-cone quark model. The medium modifications in the pion unpolarized TMDs are induced through the effective quark masses computed using the chiral SU($3$) quark mean field model. The spin densities at different momentum fraction ($x$) have also been calculated at different baryonic densities.
{"title":"Does nuclear medium affect the transverse momentum-dependent parton distributions of valence quark of pions?","authors":"Navpreet Kaur, Satyajit Puhan, Reetanshu Pandey, Arvind Kumar, Suneel Dutt, Harleen Dahiya","doi":"arxiv-2409.05394","DOIUrl":"https://doi.org/arxiv-2409.05394","url":null,"abstract":"We calculate the valence quark transverse momentum-dependent parton\u0000distributions (TMDs) of the lightest pseudoscalar meson, pions, in isospin\u0000asymmetric nuclear matter at zero temperature by employing a light-cone quark\u0000model. The medium modifications in the pion unpolarized TMDs are induced\u0000through the effective quark masses computed using the chiral SU($3$) quark mean\u0000field model. The spin densities at different momentum fraction ($x$) have also\u0000been calculated at different baryonic densities.","PeriodicalId":501573,"journal":{"name":"arXiv - PHYS - Nuclear Theory","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206532","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dominik Stamen, Jan Luca Dammann, Yannis Korte, Bastian Kubis
The polarizabilities of light pseudoscalar mesons can be extracted from differential cross sections for Compton scattering near threshold. While this has been accomplished for charged pions employing Primakoff reactions, a corresponding measurement for kaons will be affected by the presence of the $K^*(892)$ resonance not too far from threshold. We propose a method to extend the energy range serviceable for this purpose by reconstructing the $K^*(892)$ contribution model-independently from its $Kpi$ intermediate state, using dispersion theory. We point out that, in contrast to the charged-pion analog, there is likely no strong hierarchy between sum and difference of electric and magnetic dipole polarizabilities; we discuss the sensitivity to disentangling both by improved experimental angular coverage.
{"title":"Polarizabilities from kaon Compton scattering","authors":"Dominik Stamen, Jan Luca Dammann, Yannis Korte, Bastian Kubis","doi":"arxiv-2409.05955","DOIUrl":"https://doi.org/arxiv-2409.05955","url":null,"abstract":"The polarizabilities of light pseudoscalar mesons can be extracted from\u0000differential cross sections for Compton scattering near threshold. While this\u0000has been accomplished for charged pions employing Primakoff reactions, a\u0000corresponding measurement for kaons will be affected by the presence of the\u0000$K^*(892)$ resonance not too far from threshold. We propose a method to extend\u0000the energy range serviceable for this purpose by reconstructing the $K^*(892)$\u0000contribution model-independently from its $Kpi$ intermediate state, using\u0000dispersion theory. We point out that, in contrast to the charged-pion analog,\u0000there is likely no strong hierarchy between sum and difference of electric and\u0000magnetic dipole polarizabilities; we discuss the sensitivity to disentangling\u0000both by improved experimental angular coverage.","PeriodicalId":501573,"journal":{"name":"arXiv - PHYS - Nuclear Theory","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206523","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We propose novel superfluids induced by the parity-doubled baryons. The parity-doubled baryons, i.e., a nucleon $N(940)$ with spin-parity $J^{P}=1/2^{+}$ and an excited nucleon $N^{ast}(1535)$ with $J^{P}=1/2^{-}$ in vacuum, become degenerate at sufficiently high density where the chiral symmetry is restored. In this study, we extend the conventional $mathrm{U}(1)$ chiral symmetry to the higher dimensional symmetries, dubbed emergent chiral symmetries, including the naive and mirror assignments as their subgroups. Starting with the Lagrangian up to four-point interactions among the neutron $n$ and its chiral partner $n^{ast}$, neutral components in $N$ and $N^{ast}$, in pure neutron matter, we investigate the properties of the ground state with a pairing gap generated by the $n$ and $n^{ast}$ in the mean-field approximation. We find vector-type condensates that induce the dynamical breaking of a new class of internal symmetries, emergent chiral symmetries, as well as the baryon number and the rotational symmetries of the real space, indicating the appearance of massless Nambu-Goldstone bosons consisting of six quarks: emergent pions, superfluid phonons, and magnons, respectively. We also study the fermionic excitation modes at low-energy scales, and show that they exhibit a spatial anisotropy of the propagation at the Dirac cone in momentum space. Some phenomenological implications are advocated, shedding new light on the properties of neutron stars.
{"title":"Emergent chirality and superfluidity of parity-doubled baryons in neutron stars","authors":"Shigehiro Yasui, Muneto Nitta, Chihiro Sasaki","doi":"arxiv-2409.05670","DOIUrl":"https://doi.org/arxiv-2409.05670","url":null,"abstract":"We propose novel superfluids induced by the parity-doubled baryons. The\u0000parity-doubled baryons, i.e., a nucleon $N(940)$ with spin-parity\u0000$J^{P}=1/2^{+}$ and an excited nucleon $N^{ast}(1535)$ with $J^{P}=1/2^{-}$ in\u0000vacuum, become degenerate at sufficiently high density where the chiral\u0000symmetry is restored. In this study, we extend the conventional $mathrm{U}(1)$\u0000chiral symmetry to the higher dimensional symmetries, dubbed emergent chiral\u0000symmetries, including the naive and mirror assignments as their subgroups.\u0000Starting with the Lagrangian up to four-point interactions among the neutron\u0000$n$ and its chiral partner $n^{ast}$, neutral components in $N$ and\u0000$N^{ast}$, in pure neutron matter, we investigate the properties of the ground\u0000state with a pairing gap generated by the $n$ and $n^{ast}$ in the mean-field\u0000approximation. We find vector-type condensates that induce the dynamical\u0000breaking of a new class of internal symmetries, emergent chiral symmetries, as\u0000well as the baryon number and the rotational symmetries of the real space,\u0000indicating the appearance of massless Nambu-Goldstone bosons consisting of six\u0000quarks: emergent pions, superfluid phonons, and magnons, respectively. We also\u0000study the fermionic excitation modes at low-energy scales, and show that they\u0000exhibit a spatial anisotropy of the propagation at the Dirac cone in momentum\u0000space. Some phenomenological implications are advocated, shedding new light on\u0000the properties of neutron stars.","PeriodicalId":501573,"journal":{"name":"arXiv - PHYS - Nuclear Theory","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206581","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We propose a three-flavor nonlocal NJL model of quark matter with the scalar attractive, vector repulsive and diquark pairing interaction channels. The model is treated within the separable approximation to obtain the EoS of cold quark matter. The analysis of the high density asymptotics of the model allows us to conclude about its qualitative agreement with the perturbative QCD. Particularly, a color superconducting CFL state is found to be the ground one at high densities. The conformal limit of speed of sound and dimensionless interaction measure are also shown to be reached from below and above, respectively. The model is applied to modelling NSs within the scenario of early quark deconfinement triggered by the gravitational instability of the NS matter due to the BEC of a spin-color-flavor singlet three-diquark bound state, the light sexaquark, stable against the weak and strong decays. A conservative estimate of the sexaquark mass based on the most up-to-date results from QCD sum rules and a constituent quark model assumes an early quark deconfinement with the onset mass below $1~rm M_odot$. The scenario is shown to be consistent with the present observational constraints on the mass-radius relation and tidal deformability of NSs. Given the fact that the proposed model by construction exhibits an asymptotically conformal behavior, we consider the question about approximately conformal quark matter in NSs. We report a non-perturbative energy density range, which is inaccessible in NSs and where the speed of sound and dimensionless interaction measure of the CFL quark matter simultaneously attain the conformal values.
{"title":"Asymptotically conformal CFL quark matter within a nonlocal chiral quark model","authors":"Oleksii Ivanytskyi","doi":"arxiv-2409.05859","DOIUrl":"https://doi.org/arxiv-2409.05859","url":null,"abstract":"We propose a three-flavor nonlocal NJL model of quark matter with the scalar\u0000attractive, vector repulsive and diquark pairing interaction channels. The\u0000model is treated within the separable approximation to obtain the EoS of cold\u0000quark matter. The analysis of the high density asymptotics of the model allows\u0000us to conclude about its qualitative agreement with the perturbative QCD.\u0000Particularly, a color superconducting CFL state is found to be the ground one\u0000at high densities. The conformal limit of speed of sound and dimensionless\u0000interaction measure are also shown to be reached from below and above,\u0000respectively. The model is applied to modelling NSs within the scenario of\u0000early quark deconfinement triggered by the gravitational instability of the NS\u0000matter due to the BEC of a spin-color-flavor singlet three-diquark bound state,\u0000the light sexaquark, stable against the weak and strong decays. A conservative\u0000estimate of the sexaquark mass based on the most up-to-date results from QCD\u0000sum rules and a constituent quark model assumes an early quark deconfinement\u0000with the onset mass below $1~rm M_odot$. The scenario is shown to be\u0000consistent with the present observational constraints on the mass-radius\u0000relation and tidal deformability of NSs. Given the fact that the proposed model\u0000by construction exhibits an asymptotically conformal behavior, we consider the\u0000question about approximately conformal quark matter in NSs. We report a\u0000non-perturbative energy density range, which is inaccessible in NSs and where\u0000the speed of sound and dimensionless interaction measure of the CFL quark\u0000matter simultaneously attain the conformal values.","PeriodicalId":501573,"journal":{"name":"arXiv - PHYS - Nuclear Theory","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206528","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jia Jie LiSWU, Chongqing, Armen SedrakianFrankfurt U., FIAS and U. Wroclaw, Mark AlfordWashington U., St. Louis
The (re)analysis of data on the X-ray emitting pulsars PSR J0030+0451 and PSR J0740+6620, as well as new results on PSR J0437-4715, are confronted with the predictions of the equation of state (EoS) models allowing for strong first-order phase transition for the mass-radius ($M$-$R$) diagram. We use models that are based on a covariant density functional (CDF) EoS for nucleonic matter at low densities and a quark matter EoS, parameterized by the speed of sound, at higher densities. To account for the variations in the ellipses for PSR J0030+0451 obtained from different analyses, we examined three scenarios to assess their consistency with our models, focusing particularly on the potential formation of twin stars. We found that in two scenarios, where the ellipses for PSR J0030+0451 and PSR J0437-4715 with masses close to the canonical mass $sim 1.4,M_{odot}$ are significantly separated, our models allow for the presence of twin stars as a natural explanation for potential differences in the radii of these stars.
对 X 射线发射脉冲星 PSR J0030+0451 和 PSRJ0740+6620 数据的（重新）分析，以及 PSR J0437-4715 的新结果，都与质量-半径（$M$-$R$）图中允许强一阶相变的状态方程（EoS）模型的预测相冲突。我们使用的模型是基于低密度核物质的协变密度函数（CDF）EoS 和高密度夸克物质的以声速为参数的 EoS。为了解释不同分析得到的PSR J0030+0451椭圆的变化，我们研究了三种情况，以评估它们与我们的模型的一致性，尤其侧重于孪生星的潜在形成。我们发现，在两种情况下，质量接近标准质量$sim 1.4,M_{odot}$ 的PSR J0030+0451和PSR J0437-4715的椭圆明显分离，我们的模型允许孪生星的存在，这是对这些恒星半径潜在差异的一种自然解释。
{"title":"Confronting new NICER mass-radius measurements with phase transition in dense matter and compact twin stars","authors":"Jia Jie LiSWU, Chongqing, Armen SedrakianFrankfurt U., FIAS and U. Wroclaw, Mark AlfordWashington U., St. Louis","doi":"arxiv-2409.05322","DOIUrl":"https://doi.org/arxiv-2409.05322","url":null,"abstract":"The (re)analysis of data on the X-ray emitting pulsars PSR J0030+0451 and PSR\u0000J0740+6620, as well as new results on PSR J0437-4715, are confronted with the\u0000predictions of the equation of state (EoS) models allowing for strong\u0000first-order phase transition for the mass-radius ($M$-$R$) diagram. We use\u0000models that are based on a covariant density functional (CDF) EoS for nucleonic\u0000matter at low densities and a quark matter EoS, parameterized by the speed of\u0000sound, at higher densities. To account for the variations in the ellipses for\u0000PSR J0030+0451 obtained from different analyses, we examined three scenarios to\u0000assess their consistency with our models, focusing particularly on the\u0000potential formation of twin stars. We found that in two scenarios, where the\u0000ellipses for PSR J0030+0451 and PSR J0437-4715 with masses close to the\u0000canonical mass $sim 1.4,M_{odot}$ are significantly separated, our models\u0000allow for the presence of twin stars as a natural explanation for potential\u0000differences in the radii of these stars.","PeriodicalId":501573,"journal":{"name":"arXiv - PHYS - Nuclear Theory","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206533","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The two-body strong decays of the $f_0(1500)$, $f_0(1710)$, $a_0(1710)$, $f_2(1270)$, $f_2'(1525)$, and $K_2^*(1430)$ resonances are investigated, assuming them as dynamically generated states of two vector mesons via $s$-wave interactions. The partial decay widths of all the possible two-body pseudoscalar meson-pseudoscalar meson final states are calculated considering the triangular diagrams. It is found that the ratios of branching fractions are similar to the previous results for most channels, which were obtained by using the real-axis method and considering the box diagrams. However, there are also differences. In addition, our focus is on the partial decay widths. More precise experimental measurements are needed to test the model calculations and determine the nature of these scalar and tensor mesons. It is anticipated that the BESuppercaseexpandafter{romannumeral3}, Belleuppercaseexpandafter{romannumeral2} and LHCb collaborations will conduct these measurements in the future.
{"title":"Strong decays of $a_0$, $f_0$, $f_2$, and $K^*_2$ resonances as dynamically generated states of two vector mesons","authors":"Qing-Hua Shen, Li-Sheng Geng, Ju-Jun Xie","doi":"arxiv-2409.05302","DOIUrl":"https://doi.org/arxiv-2409.05302","url":null,"abstract":"The two-body strong decays of the $f_0(1500)$, $f_0(1710)$, $a_0(1710)$,\u0000$f_2(1270)$, $f_2'(1525)$, and $K_2^*(1430)$ resonances are investigated,\u0000assuming them as dynamically generated states of two vector mesons via $s$-wave\u0000interactions. The partial decay widths of all the possible two-body\u0000pseudoscalar meson-pseudoscalar meson final states are calculated considering\u0000the triangular diagrams. It is found that the ratios of branching fractions are\u0000similar to the previous results for most channels, which were obtained by using\u0000the real-axis method and considering the box diagrams. However, there are also\u0000differences. In addition, our focus is on the partial decay widths. More\u0000precise experimental measurements are needed to test the model calculations and\u0000determine the nature of these scalar and tensor mesons. It is anticipated that\u0000the BESuppercaseexpandafter{romannumeral3},\u0000Belleuppercaseexpandafter{romannumeral2} and LHCb collaborations will\u0000conduct these measurements in the future.","PeriodicalId":501573,"journal":{"name":"arXiv - PHYS - Nuclear Theory","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206534","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Perturbative expansions for atoms in QED are developed around interacting states, typically defined by the Schr"odinger equation. Calculations are nevertheless done using the standard Feynman diagram expansion around free states. The classical $-alpha/r$ potential is then obtained through an infinite sum of ladder diagrams. The complexity of this approach may have contributed to bound states being omitted from QFT textbooks, restricting the field to select experts. The confinement scale 1 fm of QCD must be introduced without changing the Lagrangian. This can be done via a boundary condition on the gauge field, which affects the bound state potential. The absence of confinement in Feynman diagrams may be due to the free field boundary condition. Poincar'e invariance is realized dynamically for bound states, i.e., the interactions are frame dependent. Gauge theories have instantaneous interactions, due to gauge fixing at all points of space at the same time. In bound state perturbation theory each order must have exact Poincar'e invariance. This is non-trivial even for atoms at lowest order. I summarize a perturbative approach to equal time bound states in QED and QCD, using a Fock expansion in temporal ($A^0=0$) gauge. The longitudinal electric field $E_L$ is instantaneous and need not vanish at spatial infinity for the constituents of color singlet states in QCD. Poincar'e covariance determines the boundary condition for $E_L$ up to a universal scale, characterised by the gluon field energy density of the vacuum. A non-vanishing density contributes a linear term to the $qbar{q}$ potential, while $qqq, qbar{q}g$ and $gg$ color singlet states get analogous confining potentials.
原子在 QED 中的惯性展开是围绕相互作用态展开的，通常由 Schr"odinger 方程定义。尽管如此，计算仍使用围绕自由态的标准费曼图展开。经典的 $-alpha/r$ 势是通过梯形图的无限和得到的。这种方法的复杂性可能导致束缚态在 QFT 教科书中被省略，使这一领域仅限于部分专家。必须在不改变拉格朗日的情况下引入 QCD 的约束尺度 1 fm。这可以通过影响束缚态势的轨距场边界条件来实现。自由场边界条件可能会导致费曼迪格图中没有约束。对于束缚态，Poincar'e 不变性是动态实现的，也就是说，相互作用与框架有关。量规理论具有瞬时相互作用，这是由于量规同时固定在空间的所有点上。入射态扰动理论的每个阶都必须具有精确的Poincar/'einvariance。即使对于最低阶的原子来说，这也是非难的。我总结了 QED 和 QCD 中等时间束缚态的扰动方法，使用的是时间（$A^0=0$）规的福克展开。纵向电场$E_L$是瞬时的，对于QCD中彩色单子态的成分来说，它不需要在空间无穷大时消失。Poincar'e协变决定了E_L$的边界条件，它达到了一个普遍尺度，以真空的胶子场能量密度为特征。非万向密度为$qbar{q}$势贡献了一个线性项，而$qqq, qqbar{q}g$和$gg$彩色单子态则得到了类似的约束势。
{"title":"Bound state basics","authors":"Paul Hoyer","doi":"arxiv-2409.05660","DOIUrl":"https://doi.org/arxiv-2409.05660","url":null,"abstract":"Perturbative expansions for atoms in QED are developed around interacting\u0000states, typically defined by the Schr\"odinger equation. Calculations are\u0000nevertheless done using the standard Feynman diagram expansion around free\u0000states. The classical $-alpha/r$ potential is then obtained through an\u0000infinite sum of ladder diagrams. The complexity of this approach may have\u0000contributed to bound states being omitted from QFT textbooks, restricting the\u0000field to select experts. The confinement scale 1 fm of QCD must be introduced without changing the\u0000Lagrangian. This can be done via a boundary condition on the gauge field, which\u0000affects the bound state potential. The absence of confinement in Feynman\u0000diagrams may be due to the free field boundary condition. Poincar'e invariance is realized dynamically for bound states, i.e., the\u0000interactions are frame dependent. Gauge theories have instantaneous\u0000interactions, due to gauge fixing at all points of space at the same time. In\u0000bound state perturbation theory each order must have exact Poincar'e\u0000invariance. This is non-trivial even for atoms at lowest order. I summarize a perturbative approach to equal time bound states in QED and\u0000QCD, using a Fock expansion in temporal ($A^0=0$) gauge. The longitudinal\u0000electric field $E_L$ is instantaneous and need not vanish at spatial infinity\u0000for the constituents of color singlet states in QCD. Poincar'e covariance\u0000determines the boundary condition for $E_L$ up to a universal scale,\u0000characterised by the gluon field energy density of the vacuum. A non-vanishing\u0000density contributes a linear term to the $qbar{q}$ potential, while $qqq,\u0000qbar{q}g$ and $gg$ color singlet states get analogous confining potentials.","PeriodicalId":501573,"journal":{"name":"arXiv - PHYS - Nuclear Theory","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206531","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Inspired by the EMC effect, the Cd puzzle and the SU3-IBM, a hypothesis can be given for a nucleus, that only the nucleus itself is a trivial (0,0) representation of the SU(3) group, which leads to a simple conclusion that spherical nucleus does not exist and the spherical mean field is not allowed. The key conclusion is that the color degree of freedom is required even at the low energy excitation of the nucleus.
{"title":"A simple explanation for the absence of the spherical nuclei","authors":"Tao Wang","doi":"arxiv-2409.05723","DOIUrl":"https://doi.org/arxiv-2409.05723","url":null,"abstract":"Inspired by the EMC effect, the Cd puzzle and the SU3-IBM, a hypothesis can\u0000be given for a nucleus, that only the nucleus itself is a trivial (0,0)\u0000representation of the SU(3) group, which leads to a simple conclusion that\u0000spherical nucleus does not exist and the spherical mean field is not allowed.\u0000The key conclusion is that the color degree of freedom is required even at the\u0000low energy excitation of the nucleus.","PeriodicalId":501573,"journal":{"name":"arXiv - PHYS - Nuclear Theory","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206524","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In relativistic heavy-ion collisions, the formation of a deconfined and thermalized state of partons, known as quark-gluon plasma, leads to enhanced production of strange hadrons in contrast to proton-proton (pp) collisions, which are taken as baseline. This observation is known as strangeness enhancement in heavy-ion collisions and is considered one of the important signatures that can signify the formation of QGP. However, in addition to strangeness enhancement, recent measurements hint at observing several heavy-ion-like features in high-multiplicity pp collisions at the LHC energies. Alternatively, event shape observables, such as charged particle multiplicity, transverse spherocity, transverse sphericity, charged particle flattenicity, and relative transverse activity classifiers, can fundamentally separate hard interaction-dominated jetty events from soft isotropic events. These features of event shape observables can probe the observed heavy-ion-like features in pp collisions with significantly reduced selection bias and can bring all collision systems on equal footing. In this article, we present an extensive summary of the strange particle ratios to pions as a function of different event classifiers using the PYTHIA~8 model with color reconnection and rope hadronization mechanisms to understand the microscopic origin of strangeness enhancement in pp collisions and also prescribe the applicability of these event classifiers in the context of strangeness enhancement. Charged-particle flattenicity is found to be most suited for the study of strangeness enhancement, and it shows a similar quantitative enhancement as seen for the analysis based on the number of multi-parton interactions.
{"title":"Probing strangeness with event topology classifiers in pp collisions at the LHC with rope hadronization mechanism in PYTHIA","authors":"Suraj Prasad, Bhagyarathi Sahoo, Sushanta Tripathy, Neelkamal Mallick, Raghunath Sahoo","doi":"arxiv-2409.05454","DOIUrl":"https://doi.org/arxiv-2409.05454","url":null,"abstract":"In relativistic heavy-ion collisions, the formation of a deconfined and\u0000thermalized state of partons, known as quark-gluon plasma, leads to enhanced\u0000production of strange hadrons in contrast to proton-proton (pp) collisions,\u0000which are taken as baseline. This observation is known as strangeness\u0000enhancement in heavy-ion collisions and is considered one of the important\u0000signatures that can signify the formation of QGP. However, in addition to\u0000strangeness enhancement, recent measurements hint at observing several\u0000heavy-ion-like features in high-multiplicity pp collisions at the LHC energies.\u0000Alternatively, event shape observables, such as charged particle multiplicity,\u0000transverse spherocity, transverse sphericity, charged particle flattenicity,\u0000and relative transverse activity classifiers, can fundamentally separate hard\u0000interaction-dominated jetty events from soft isotropic events. These features\u0000of event shape observables can probe the observed heavy-ion-like features in pp\u0000collisions with significantly reduced selection bias and can bring all\u0000collision systems on equal footing. In this article, we present an extensive\u0000summary of the strange particle ratios to pions as a function of different\u0000event classifiers using the PYTHIA~8 model with color reconnection and rope\u0000hadronization mechanisms to understand the microscopic origin of strangeness\u0000enhancement in pp collisions and also prescribe the applicability of these\u0000event classifiers in the context of strangeness enhancement. Charged-particle\u0000flattenicity is found to be most suited for the study of strangeness\u0000enhancement, and it shows a similar quantitative enhancement as seen for the\u0000analysis based on the number of multi-parton interactions.","PeriodicalId":501573,"journal":{"name":"arXiv - PHYS - Nuclear Theory","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206530","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. A. Flett, J. P. Lansberg, S. Nabeebaccus, M. Nefedov, P. Sznajder, J. Wagner
We perform the first complete one-loop study of exclusive photoproduction of vector quarkonia off protons in Collinear Factorisation (CF) including the scale evolution of the Generalised Parton Distributions (GPDs). We confirm the perturbative instability of the cross section at high photon-proton-collision energies (W_gamma+p) at Next-to-Leading Order (NLO) in alpha_s and solve this issue by resumming higher-order QCD corrections, which are enhanced by a logarithm of the parton energies, using High-Energy Factorisation (HEF) in the Doubly-Logarithmic Approximation (DLA) matched to CF. Our NLO CF + DLA HEF results are in agreement with the latest HERA data, show a smaller sensitivity to the factorisation and renormalisation scales compared to Born-order results. Quark-induced channels via interference with gluon ones are found to contribute at most 20% of the cross section for W_gamma+p > 100 GeV. Our results also show that such exclusive cross sections cannot be accurately obtained from the square of usual Parton Distribution Functions (PDFs) and clearly illustrate the importance of quarkonium exclusive photoproduction to advance our understanding of the 3D content of the nucleon in terms of gluons. Our work provides an important step towards a correct interpretation of present and future experimental data collected at HERA, the EIC, the LHC and future experiments.
我们首次在共线因数化（CF）中对质子外的矢量夸克独占光生成进行了完整的一回路研究，包括广义粒子分布（GPD）的尺度演化。我们证实了高光子-质子对撞能量（W_gamma+p）下α_s的截面在次领先阶（NLO）时的扰动不稳定性，并通过重和高阶QCD修正来解决这个问题，高阶QCD修正通过与CF相匹配的双对数近似（DLA）中的高能量因式分解（HEF）来增强。我们的 NLO CF + DLA HEF 结果与最新的 HERA 数据一致，与伯恩阶结果相比，显示出对因式分解和重正化尺度较小的敏感性。我们的结果还表明，这种排他性截面不能从通常的粒子分布函数（PDF）的平方中准确地获得，并清楚地说明了夸克排他性光生成对于推动我们理解核子的胶子三维内容的重要性。我们的工作为正确解释目前和未来在 HERA、EIC、大型强子对撞机和未来实验中收集的实验数据迈出了重要的一步。
{"title":"Exclusive vector-quarkonium photoproduction at NLO in alpha_s in collinear factorisation with evolution of the generalised parton distributions and high-energy resummation","authors":"C. A. Flett, J. P. Lansberg, S. Nabeebaccus, M. Nefedov, P. Sznajder, J. Wagner","doi":"arxiv-2409.05738","DOIUrl":"https://doi.org/arxiv-2409.05738","url":null,"abstract":"We perform the first complete one-loop study of exclusive photoproduction of\u0000vector quarkonia off protons in Collinear Factorisation (CF) including the\u0000scale evolution of the Generalised Parton Distributions (GPDs). We confirm the\u0000perturbative instability of the cross section at high photon-proton-collision\u0000energies (W_gamma+p) at Next-to-Leading Order (NLO) in alpha_s and solve this\u0000issue by resumming higher-order QCD corrections, which are enhanced by a\u0000logarithm of the parton energies, using High-Energy Factorisation (HEF) in the\u0000Doubly-Logarithmic Approximation (DLA) matched to CF. Our NLO CF + DLA HEF\u0000results are in agreement with the latest HERA data, show a smaller sensitivity\u0000to the factorisation and renormalisation scales compared to Born-order results.\u0000Quark-induced channels via interference with gluon ones are found to contribute\u0000at most 20% of the cross section for W_gamma+p > 100 GeV. Our results also show\u0000that such exclusive cross sections cannot be accurately obtained from the\u0000square of usual Parton Distribution Functions (PDFs) and clearly illustrate the\u0000importance of quarkonium exclusive photoproduction to advance our understanding\u0000of the 3D content of the nucleon in terms of gluons. Our work provides an\u0000important step towards a correct interpretation of present and future\u0000experimental data collected at HERA, the EIC, the LHC and future experiments.","PeriodicalId":501573,"journal":{"name":"arXiv - PHYS - Nuclear Theory","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206529","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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