Rope Hadronization is a model extending the Lund string hadronization model to describe environments with many overlapping strings, such as high multiplicity pp collisions or $AA$ collisions. Including effects of Rope Hadronization drastically improves description of strange/non-strange hadron ratios as function of event multiplicity in all systems from $e^+ e^-$ to $AA$. Implementation of Rope Hadronization in the MC event generators DIPSY and Pythia8 is discussed, as well as future prospects for jet studies and studies of small systems.
The observation of long range ridge-like structure in the near-side region of the two particle $Δη-Δϕ$ correlations as measured by LHC experiments in high multiplicity p$-$p collisions indicated towards the presence of collective effects which are similar to that observed in p$-$A(nucleon-nucleus) and A$-$A (nucleus-nucleus) collisions. The two particle correlation between the charged particles in $Δη-Δϕ$ for p$-$p collisions at $\sqrt{s}$ = 7 TeV and 13 TeV is studied using Pythia 8 event generator within the framework of final-state partonic color reconnection effects as well as the microsco…
We present novel rope hadronization results for strange hadron enhancement in pp, pPb, and PbPb collisions using PYTHIA/Angantyr at LHC energies. With the rope model for string fragmentation, we find that the strangeness and baryon enhancement has a coherent increase across all collision systems as a function of average charged central multiplicity, in qualitative agreement with LHC data. In AA collisions, we find that the baryonic yields overshoot data at high multiplicities, and we discuss how a combination of rope hadronization with other string interactions may tame this rise.
We present the microscopic model for collective effects, built on string-string interactions (string shoving and rope hadronization), recently implemented in the PYTHIA 8 and DIPSY event generators. Rope hadronization is shown to give a good description of strangeness enhancement across pp, pA and AA collisions systems, while string shoving qualitatively describes the ridge observed in pp collisions.
Core-corona procedure and microcanonical hadronization to understand strangeness enhancement in proton-proton and heavy ion collisions in the EPOS4 framework
Boost-invariant hadron production in high energy collisions occurs in causally disconnected regions of finite space-time size. As a result, globally conserved quantum numbers (charge, strangeness, baryon number) are conserved locally in spatially restricted correlation clusters. Their size is determined by two time scales: the equilibration time specifying the formation of a quark-gluon plasma, and the hadronization time, specifying the onset of confinement. The expected values for these scales provide the theoretical basis for the suppression observed for strangeness production in elementary …
Strangeness Production in Heavy-Ion Collisions: Color Ropes or Hydrodynamic Evolution?
Frankfurt Institute for Advanced Studies（法兰克福高级研究所）；Institute for Theoretical Physics, Goethe University（歌德大学理论物理研究所）；GSI Helmholtzzentrum für Schwerionenforschung（GSI亥姆霍兹重离子研究中心）；Helmholtz Research Academy Hesse for FAIR (HFHF)（黑森FAIR亥姆霍兹研究院）
Strangeness and charm in quark-gluon hadronization
本文对相对论性重离子碰撞中的软强子产生进行了理论研究。我们探讨了膨胀的QGP火球强子化的原理，并了解它的性质。大部分正在进行的努力是证明一个QGP强子化模型的有效性，该模型准确地描述了粒子产生数据。我们从RHIC上62.4GeV的Au-Au碰撞中的多奇异强子的中心性研究开始。我们发现统计强子化模型（SHM）很好地描述了QGP强子化中的粒子产生。对于所有的中心性，物理性质是相容的，较早提出的临界强子化压力建议普遍强子化条件QGP。LHC中的重离子碰撞对SHM在TeV能量尺度上描述粒子产生提出了新的挑战。我们表明，化学非平衡模型给出了一个很好的描述在铅-铅碰撞在2.76 TeV的强子生产一致的中心性的函数。此外，模型参数假设的预期值建议在较低的能量以前的研究。夸克-胶子等离子体火球在相同的强子化条件下发生强子化，即共同的临界压力、熵和能量密度。在大型强子对撞机的能量下，预计会产生大量的粲，因此将粲纳入目前对粒子产生的描述是至关重要的。我们提出了一个升级的SHARE与CHARM计划，量化的魅力的影响，较轻的强子的产额和物理性质的强子化火球。除了光味（$u,d,s$），SHARE with CHARM还描述了粲强子的产生和衰变。我们观察到，根据目前的实验结果，粲衰变主要影响多奇异粒子的产额。
The unified set of yields of particles produced in proton-proton collisions at $\sqrt{s}$ = 17.3 GeV (laboratory beam momentum 158 GeV/c) is evaluated, combining the experimental results of the NA49 and NA61/SHINE collaborations at the CERN SPS. With the statistical hadronization code Thermal-Fist we confirm the unacceptably high value of $χ^2$, both in the canonical and grand canonical - strangeness canonical approach, and the common volume for all the hadrons. The use of the energy-dependent width of the Breit-Wigner parametrization for the mass distributions of unstable particles improves t…
Enhancement in strangeness yields in heavy-ion collisions is regarded as one of the attributes of the Quark-Gluon Plasma (QGP) along with jet quenching and final-state collectivity. To reproduce these effects in the MC implementation of the Lund string model in \pythia, the inclusion of non-perturbative mechanisms like string shoving and rope hadronization is crucial. In this proceeding, we discuss our latest implementation of these mechanisms and the preliminary results for the strangeness enhancement in high-multiplicity p-p, p-Pb and Xe-Xe. We conclude with remarks on the ongoing developmen…
In this work, the relative Underlying Event (UE) transverse multiplicity activity classifier ($R_{\rm {T}}$) is used to study the strange and multi-strange hadron production in proton-proton collisions. Our study with $R_{\rm {T}}$ would allow to disentangle these particles, which are originating from the soft and hard QCD processes. We have used the PYTHIA 8 Monte-Carlo (MC) with a different implementation of color reconnection and rope hadronization models to demonstrate the proton-proton collisions data at $\sqrt{s}$ = 13 TeV. The relative production of strange and multi-strange hadrons are…
We apply a quark combination model to study yield densities and transverse momentum ($p_{T}$) spectra of strange (anti-)hadrons at mid-rapidity in central Au+Au collisions at $\sqrt{s_{NN}}=$ 7.7, 11.5, 19.6, 27, 39 and 200 GeV. We show that experimental data for $p_{T}$ spectra of (anti-)hadrons in these collisions can be systematically described by the equal velocity combination of constituent quarks and antiquarks at hadronization. We obtain $p_{T}$ spectra of quarks and antiquarks at hadronization and study their collision energy dependence. We also reproduce the yield densities of hadrons…
We show that the data of $p_{T}$ spectra of $Ω^{-}$ and $ϕ$ at midrapidity in inelastic events in $pp$ collisions at $\sqrt{s}=$ 13 TeV exhibit a constituent quark number scaling property, which is a clear signal of quark combination mechanism at hadronization. We use a quark combination model under equal velocity combination approximation to systematically study the production of identified hadrons in $pp$ collisions at $\sqrt{s}$= 13 TeV. The midrapidity data of $p_{T}$ spectra of proton, $Λ$, $Ξ^{-}$, $Ω^{-}$, $ϕ$ and $K^{*}$ in inelastic events are simultaneously well fitted by the model. …
Probing strangeness with event topology classifiers in pp collisions at energies available at the CERN Large Hadron Collider with the rope hadronization mechanism in PYTHIA
Strangeness production in high multiplicity events gives indications on the transverse size fluctuactions in nucleus-nucleus ($AA$), proton-nucleus ($pA$) and proton-proton ($pp$) collisions. In particular the behavior of strange particle hadronization in "small" ($pp,pA$) and "large" ($AA$) initial configurations of the collision can be tested for the specific particle species, for different centralities and for large fluctuations of the transverse size in $pA$ and $pp$ by using the recent ALICE data. A universality of strange hadron production emerges by introducing a dynamical variable prop…
In the string melting version of a multiphase transport model, the hadronization algorithm has been improved by favoring parton combinations close in not only coordinate space but also momentum space. Formation probabilities of mesons, baryons, and antibaryons during hadronization are determined by their corresponding Wigner functions for the valence parton combinations with no free parameters, and the net baryon, electric, and strangeness charges are conserved during quark coalescence. Effects of the hadronization on anisotropic flows, collision energy dependence of the proton directed flow, …
An extension of the rope hadronization model, which has previously provided good descriptions of hadrochemistry in high multiplicity pp collisions, is presented. The extension includes a dynamically generated transverse pressure, produced by the excess energy from overlapping strings. We find that this model can qualitatively reproduce soft features of Quark Gluon Plasma in small systems, such as higher $\langle p_\perp \rangle$ for heavier particles and long range azimuthal correlations forming a ridge. The effects are similar to those obtained from a hydrodynamic expansion, but without assum…
Elliptic flow of $ϕ$ meson and strange quark collectivity at RHIC
基于多相输运（AMPT）模型，我们在布鲁克海文国家实验室（Brookhaven National Laboratory）的相对论重离子对撞机（Heavy Ion Collider）上，从重建的$K^{+}K^{-}$衰变通道中研究了$ϕ$介子的椭圆流$v_{2}$.给出了$v_{2}$对横动量$p_T$和碰撞中心度的依赖关系，并研究了$ϕ$介子在强子相中的再散射效应.结果表明，对$ϕ$介子的$v_{2}$的实验测量可以保留$ϕ$衰变前的早期碰撞信息，并且$ϕ$ $v_2$值服从组分夸克数标度，这与对其它介子和重子的测量结果一致.研究表明，$ϕ$ $v_2$主要反映了在核-核碰撞早期发展的部分子集体性，奇异和轻的上/下夸克在强子化时也发展了类似的角各向异性性质.
在简要回顾了200 A GeV以下重离子碰撞实验的成就之后，我们深入讨论了奇异粒子的产生在这些对撞中寻找新相物质的作用。特别是，我们发现，所观察到的增强模式，否则很少产生multisquite反重子可以一贯地解释假设在本地化的，迅速瓦解的强子源的颜色deconconfinement。我们发展的理论描述这个源，特别是研究QCD为基础的过程中的奇异生产的退禁闭，热夸克-胶子等离子体阶段，允许接近化学平衡和动力学演化。我们还处理热魅力生产。利用快速强子化模型，我们得到了最终态粒子产额，提供了详细的理论预测奇异粒子谱和产额作为重离子能量的函数。我们的介绍是全面的，自成一体的：我们相当详细地介绍了数据解释中使用的程序，讨论了选定的实验结果的特别重要性，并展示了它们如何影响理论的发展。
Using a covariant quark coalescence model combined with a blast-wave-like analytical parametrization for (anti-)strange quark phase-space freeze-out configuration, we extract information on strange quark freeze-out dynamics in Pb+Pb collisions at $\sqrt{s_{NN}}$=2.76 TeV by fitting the measured transverse momentum spectra and elliptic flows ($v_2$) of $ϕ$ mesons and $Ω$ baryons. We find that although both the measured and calculated $v_2$ of $ϕ$ and $Ω$ satisfy the number-of-constituent-quark (NCQ) scaling, the NCQ-scaled $v_2$ is significantly smaller than the $v_2$ of strange quarks, implyin…
D-meson production via sequential hadronization in high-energy nuclear collisions
Central China Normal University（华中师范大学）；China University of Geosciences（中国地质大学）；GSI Helmholtz Center for Heavy Ion Physics（德国重离子研究中心）；Johann Wolfgang Goethe-Universität（约翰·沃尔夫冈·歌德法兰克福大学）；Yantai University（烟台大学）；Tsinghua University（清华大学）；Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所）
By analyzing the available data on strange hadrons in central Pb+Pb collisions from the NA49 Collaboration at the Super Proton Synchrotron (SPS) and in central Au+Au collisions from the STAR Collaboration at the Relativistic Heavy-Ion Collider (RHIC) in a wide collision energy range from $\sqrt{s_{\rm NN}}$ = 6.3 GeV to 200 GeV, we find a possible non-monotonic behavior in the ratio $\mathcal{O}_\text{K-$Ξ$-$ϕ$-$Λ$}$= $\frac{N(K^+)N(Ξ^-)}{N(ϕ)N(Λ)}$ of $K^+$, $Ξ^-$, $ϕ$, and $Λ$ yields as a function of $\sqrt{s_{\rm NN}}$. Based on the quark coalescence model, which can take into account the e…
Yield ratios of identified hadrons observed in high multiplicity p+p and p+Pb collisions at LHC show remarkable similarity with those in Pb+Pb collisions, indicating some important and universal underlying dynamics in hadron production for different quark gluon final states. We use the quark combination model to explain the data of yield ratios in these three collision systems. The observed $p/π$ and $Λ/K_s^0$ can be reproduced simultaneously by quark combination, and these two ratios reflect the rate of baryon production at hadronization which is the same in light sector and strange sector an…
We propose that the charged-particle multiplicity dependence of the charm-baryon-to-meson ratio observed in high-energy $pp$ collisions can be explained by canonical treatment of quantum charges in the statistical hadronization model (SHM). Taking the full particle listings of PDG complemented by additional charm-baryon states from relativistic quark model predictions, we evaluate the canonical partition function and the charm-hadron chemical factors that measure the canonical suppression arising from the requirement of strict conservation of quantum charges. We demonstrate that, while charm n…
