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CMS-PAS-HIN-20-002
Elliptic anisotropy measurement of the f$_0$(980) hadron in proton-lead collisions and evidence of its quark-antiquark composition by CMS
Abstract: Despite its discovery half a century ago, the question about the quark content of the $ \rm{f}_0(980) $ hadron has not been settled, whether its being an ordinary quark-antiquark meson, a tetraquark exotic state, a kaon-antikaon molecule, or a quark-antiquark-gluon hybrid. In this note, evidence that the $ \rm{f}_0(980) $ hadron is an ordinary quark-antiquark meson is reported, by employing the number-of-constituent-quark (NCQ) scaling of elliptic flow anisotropies ($ v_2 $), empirically established by conventional hadrons up to transverse momentum ($ p_{\rm {T}} $) of about 10 GeV/$ c $ in relativistic heavy ion collisions. The $ \rm{f}_0(980) $ is reconstructed via the invariant mass of its main decay channel $ {\rm{f}_0(980)} \to \pi ^ + \pi ^ - $ in proton-lead collisions recorded by the CMS experiment at the LHC. The $ \rm{f}_0(980) $ yield is measured relative to the second-order symmetry plane as reconstructed from the energy deposited in the forward/backward region of the CMS detector, and its $ v_2 $ parameter is extracted as a function of $ p_{\rm {T}} $. It is found that the $ \rm{f}_0(980) $ explanation as an ordinary quark-antiquark state is preferred over a tetraquark or $ {\rm{K}\overline{K}} $ molecule hypothesis at 7.7, 6.3, or 3.1 standard deviations in the $ p_{\rm {T}} < $ 10, 8, or 6 $ \rm{GeV/c} $ ranges, respectively. The quark-antiquark hypothesis is also preferred by 3.5 standard deviations over the $ p_{\rm {T}} < $ 8 GeV/$c$ range for $ n_{\rm{q}}= $ 3, characteristic of a quark-antiquark-gluon hybrid state. The first determination of the $ \rm{f}_0(980) $ state quark content with high confidence using this novel approach advances the study of quantum chromodynamics, the fundamental theory governing the physics of hadrons.
Figures & Tables Summary References CMS Publications
Figures

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Figure 1:
This picture illustrates the formation of hadrons in heavy ion collisions in the coalescence model. Hadrons are formed only when the constituent quarks have similar positions and momenta.

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Figure 2:
The same-sign combinatorial background subtracted invariant mass spectrum for pair transverse momentum 4 $ < p_{\mathrm{T}} < $ 6 GeV/$ c $ and azimuthal angle 0 $ < \phi-\psi_2 < \pi/ $ 12 in high-multiplicity (185 $ \leq N_{\rm trk}^{\rm offline} < $ 250) pPb collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}= $ 8.16 TeV. The solid blue curve is the fit result where the blue dashed lines indicate the fitting range; the orange dashed curve represents the residual background, and the violet dashed line represents the total background. Solid red curve represent $ \rm{f}_0(980)$ signal, while the dashed deep violet and green curves represent the background contributions from $ \rho(770) $ and $ \mathrm{f}_2(1270) $, respectively. The ratio between data and fit is shown in the bottom panel. Error bars show statistical uncertainties.

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Figure 3:
The $ \rm{f}_0(980)$ yield for 4 $ < p_{\mathrm{T}} < $ 6 GeV/$ c $ as a function of $ \phi-\psi_2 $ in high-multiplicity pPb collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}= $ 8.16 TeV. Error bars show statistical uncertainties. The red curve is a fit to Eq. (1) with only the $ n= $ 2 term.

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Figure 4:
The elliptic anisotropy $ v_2 $ and the nonflow-subtracted $ v_2^{\rm sub} $ of the $ \rm{f}_0(980)$ as functions of $ p_{\mathrm{T}} $ within pseudorapidity $ |\eta| < $ 2.4 in high-multiplicity 185 $ \leq N_{\rm trk }^{\rm offline} < $ 250 pPb collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}= $ 8.16 TeV. Error bars show statistical uncertainties, while the shaded areas represent systematic uncertainties.

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Figure 4-a:
The elliptic anisotropy $ v_2 $ and the nonflow-subtracted $ v_2^{\rm sub} $ of the $ \rm{f}_0(980)$ as functions of $ p_{\mathrm{T}} $ within pseudorapidity $ |\eta| < $ 2.4 in high-multiplicity 185 $ \leq N_{\rm trk }^{\rm offline} < $ 250 pPb collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}= $ 8.16 TeV. Error bars show statistical uncertainties, while the shaded areas represent systematic uncertainties.

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Figure 4-b:
The elliptic anisotropy $ v_2 $ and the nonflow-subtracted $ v_2^{\rm sub} $ of the $ \rm{f}_0(980)$ as functions of $ p_{\mathrm{T}} $ within pseudorapidity $ |\eta| < $ 2.4 in high-multiplicity 185 $ \leq N_{\rm trk }^{\rm offline} < $ 250 pPb collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}= $ 8.16 TeV. Error bars show statistical uncertainties, while the shaded areas represent systematic uncertainties.

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Figure 5:
The $ v_2^{\rm sub}/n_\mathrm{q} $ of $ \rm{f}_0(980)$ (with $ n_\mathrm{q}= $ 2 and 4) as functions of $ p_{\mathrm{T}}/n_\mathrm{q} $ (left panel) and $ E_{\mathrm{T}}/n_\mathrm{q} $ (right panel), compared with those of other hadrons ($ \mathrm{K^0_S} $, $ \Lambda $, $ \Xi^{-} $, $ \Omega ^- $ strange hadrons) in high-multiplicity 185 $ \leq N_{\rm trk }^{\rm offline} < $ 250 pPb collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}= $ 8.16 TeV. Error bars show statistical uncertainties, while the shaded areas represent systematic uncertainties. The red curves are the NCQ scaling parameterizations to the data of the other hadrons.

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Figure 5-a:
The $ v_2^{\rm sub}/n_\mathrm{q} $ of $ \rm{f}_0(980)$ (with $ n_\mathrm{q}= $ 2 and 4) as functions of $ p_{\mathrm{T}}/n_\mathrm{q} $ (left panel) and $ E_{\mathrm{T}}/n_\mathrm{q} $ (right panel), compared with those of other hadrons ($ \mathrm{K^0_S} $, $ \Lambda $, $ \Xi^{-} $, $ \Omega ^- $ strange hadrons) in high-multiplicity 185 $ \leq N_{\rm trk }^{\rm offline} < $ 250 pPb collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}= $ 8.16 TeV. Error bars show statistical uncertainties, while the shaded areas represent systematic uncertainties. The red curves are the NCQ scaling parameterizations to the data of the other hadrons.

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Figure 5-b:
The $ v_2^{\rm sub}/n_\mathrm{q} $ of $ \rm{f}_0(980)$ (with $ n_\mathrm{q}= $ 2 and 4) as functions of $ p_{\mathrm{T}}/n_\mathrm{q} $ (left panel) and $ E_{\mathrm{T}}/n_\mathrm{q} $ (right panel), compared with those of other hadrons ($ \mathrm{K^0_S} $, $ \Lambda $, $ \Xi^{-} $, $ \Omega ^- $ strange hadrons) in high-multiplicity 185 $ \leq N_{\rm trk }^{\rm offline} < $ 250 pPb collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}= $ 8.16 TeV. Error bars show statistical uncertainties, while the shaded areas represent systematic uncertainties. The red curves are the NCQ scaling parameterizations to the data of the other hadrons.

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Figure 6:
The log-likelihood ratio distributions for hypotheses $ n_\mathrm{q}= $ 2 and $ n_\mathrm{q}= $ 4 from the pseudoexperiments and the observed value (0 $ < p_{\mathrm{T}} < $ 10 GeV/c).

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Figure 7:
The $ \chi^2 $ of the $ \rm{f}_0(980)$ elliptic flow data from the NCQ-scaling parameterization, scanned in steps of $ n_\mathrm{q} $.

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Figure 8:
Same as Fig. 6 but using $ \rm{f}_0(980)v_2^{\rm sub} $ data within restricted $ p_{\mathrm{T}} $ ranges of $ p_{\mathrm{T}} < $ 8 GeV/$ c $ (left panel) and $ p_{\mathrm{T}} < $ 6 GeV/$ c $ (right panel).

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Figure 8-a:
Same as Fig. 6 but using $ \rm{f}_0(980)v_2^{\rm sub} $ data within restricted $ p_{\mathrm{T}} $ ranges of $ p_{\mathrm{T}} < $ 8 GeV/$ c $ (left panel) and $ p_{\mathrm{T}} < $ 6 GeV/$ c $ (right panel).

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Figure 8-b:
Same as Fig. 6 but using $ \rm{f}_0(980)v_2^{\rm sub} $ data within restricted $ p_{\mathrm{T}} $ ranges of $ p_{\mathrm{T}} < $ 8 GeV/$ c $ (left panel) and $ p_{\mathrm{T}} < $ 6 GeV/$ c $ (right panel).

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Figure 9:
The log-likelihood ratio distributions for hypotheses $ n_\mathrm{q}= $ 2 and $ n_\mathrm{q}= $ 3 from the pseudoexperiments and the observed value.

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Figure 10:
The $ \chi^2 $ of the $ \rm{f}_0(980)$ elliptic flow data from the NCQ-scaling parameterization, scanned in steps of $ n_\mathrm{q} $. The three curves correspond to using $ \rm{f}_0(980)$ data from $ p_{\mathrm{T}} < $ 6 GeV/$ c $, $ p_{\mathrm{T}} < $ 8 GeV/$ c $, and $ p_{\mathrm{T}} < $ 10 GeV/$ c $, respectively.
Tables

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Table 1:
Sources and magnitudes of the uncertainties in the extracted $ n_\mathrm{q} $ of the $ \rm{f}_0(980)$ with data from $ p_{\mathrm{T}} < $ 10 GeV/$ c $.
Summary
In summary, the $ \rm{f}_0(980)$ yields are extracted at midrapidity ($ |\eta| < $ 2.4) from the invariant mass spectra of its main $ \pi^+\pi^- $ decay channel in high-multiplicity pPb collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}= $ 8.16 TeV by the CMS experiment at the LHC. The elliptic flow anisotropy $ v_2 $ of the $ \rm{f}_0(980)$ is measured as a function of $ p_{\mathrm{T}} $ up to 10 GeV/c, with respect to the second-order harmonic plane reconstructed from forward/backward energies. Nonflow contamination is estimated from $ \mathrm{K^0_S} $ measurements and is subtracted. By comparing the nonflow-subtracted $ v_2^{\rm sub} $ of the $ \rm{f}_0(980)$ to those of $ \mathrm{K^0_S} $, $ \Lambda $, $ \Xi^{-} $, and $ \Omega $ under the NCQ scaling hypothesis, we found evidence that the $ \rm{f}_0(980)$ hadron is a normal quark-antiquark state. The $ \rm{f}_0(980)$ is 7.7 standard deviations away from being a $ n_\mathrm{q}= $ 4 tetraquark state or $ {\mathrm{K}\overline{\mathrm{K}}} $ molecule. The significance is 6.3 $ \sigma $ and 3.1 $ \sigma $ respectively, if only the restricted $ p_{\mathrm{T}} $ range of $ p_{\mathrm{T}} < $ 8 GeV/c and $ p_{\mathrm{T}} < $ 6 GeV/$c$ is considered. The $ \rm{f}_0(980)$ data in $ p_{\mathrm{T}} < $ 8 GeV/$ c $ are found to be 3.5 $ \sigma $ away from the NCQ scaling with $ n_\mathrm{q}= $ 3, characteristic of a quark-antiquark-gluon hybrid state. The number of constituent quarks $ n_\mathrm{q} $ of the $ \rm{f}_0(980)$ is also extracted, and is consistent with the value of 2. Our experimental determination of the quark content of the $ \rm{f}_0(980)$ with high confidence under this novel approach is expected to stimulate further experimental investigations as well as theoretical studies. Those future endeavors will likely advance our understanding of QCD and Nature.
References
1 M. Gell-Mann A Schematic Model of Baryons and Mesons PL 8 (1964) 214
2 G. Zweig An SU(3) model for strong interaction symmetry and its breaking. Version 2 in Developments in the Quark Theory of Hadrons, Vol. 1, 1964-1978
link
3 R. L. Jaffe Perhaps a Stable Dihyperon PRL 38 (1977) 195
4 R. L. Jaffe Exotica Phys. Rept. 409 (2005) 1 hep-ph/0409065
5 Belle Collaboration Observation of a narrow charmonium-like state in exclusive $ B^\pm \to K^\pm \pi^+ \pi^- J/\psi $ decays PRL 91 (2003) 262001 hep-ex/0309032
6 LHCb Collaboration Observation of $ J/\psi p $ Resonances Consistent with Pentaquark States in $ \Lambda_b^0 \to J/\psi K^- p $ Decays PRL 115 (2015) 072001 1507.03414
7 LHCb Collaboration Observation of a narrow pentaquark state, $ P_c(4312)^+ $, and of two-peak structure of the $ P_c(4450)^+ $ PRL 122 (2019) 222001 1904.03947
8 LHCb Collaboration Observation of $ B^0_{(s)} \to J/\psi p \overline{p} $ decays and precision measurements of the $ B^0_{(s)} $ masses PRL 122 (2019) 191804 1902.05588
9 LHCb Collaboration Observation of an exotic narrow doubly charmed tetraquark Nature Phys. 18 (2022) 751 2109.01038
10 LHCb Collaboration Study of the doubly charmed tetraquark $ T_{cc}^{+} $ Nature Commun. 13 (2022) 3351 2109.01056
11 H.-X. Chen, W. Chen, X. Liu, and S.-L. Zhu The hidden-charm pentaquark and tetraquark states Phys. Rept. 639 (2016) 1 1601.02092
12 A. Esposito, A. Pilloni, and A. D. Polosa Multiquark Resonances Phys. Rept. 668 (2017) 1 1611.07920
13 N. Brambilla et al. The $ XYZ $ states: experimental and theoretical status and perspectives Phys. Rept. 873 (2020) 1 1907.07583
14 S. D. Protopopescu et al. $ \pi\pi $ Partial Wave Analysis from Reactions $ \pi^+ p \to \pi^+ \pi^- \Delta^{++} $ and $ \pi^+ p \to K^+ K^- \Delta^{++} $ at 7.1 GeV/$ c $ PRD 7 (1973) 1279
15 B. Hyams et al. $ \pi\pi $ Phase Shift Analysis from 600-MeV to 1900-MeV NPB 64 (1973) 134
16 G. Grayer et al. High Statistics Study of the Reaction $ \pi^{-} p \to \pi^{-} \pi^{+} n$: Apparatus, Method of Analysis, and General Features of Results at 17 GeV/$c$ NPB 75 (1974) 189
17 R. L. Jaffe Multi-Quark Hadrons. 1. The Phenomenology of (2 Quark 2 anti-Quark) Mesons PRD 15 (1977) 267
18 J. D. Weinstein and N. Isgur K anti-K Molecules PRD 41 (1990) 2236
19 F. E. Close and N. A. Tornqvist Scalar mesons above and below 1-GeV JPG 28 (2002) R249 hep-ph/0204205
20 C. Amsler and N. A. Tornqvist Mesons beyond the naive quark model Phys. Rept. 389 (2004) 61
21 L. Maiani, F. Piccinini, A. D. Polosa, and V. Riquer A New look at scalar mesons PRL 93 (2004) 212002 hep-ph/0407017
22 D. V. Bugg Four sorts of meson Phys. Rept. 397 (2004) 257 hep-ex/0412045
23 E. Klempt and A. Zaitsev Glueballs, Hybrids, Multiquarks. Experimental facts versus QCD inspired concepts Phys. Rept. 454 (2007) 1 0708.4016
24 G. 't Hooft et al. A Theory of Scalar Mesons PLB 662 (2008) 424 0801.2288
25 J. R. Pelaez From controversy to precision on the sigma meson: a review on the status of the non-ordinary $ f_0(500) $ resonance Phys. Rept. 658 (2016) 1 1510.00653
26 F.-K. Guo et al. Hadronic molecules Rev. Mod. Phys. 90 (2018) 015004 1705.00141
27 T. Barnes Two Photon Decays Support the (K anti-K) Molecule Picture of the S* (975) and Delta (980) PLB 165 (1985) 434
28 Z. P. Li, F. E. Close, and T. Barnes Relativistic effects in gamma gamma decays of P wave positronium and q anti-q systems PRD 43 (1991) 2161
29 R. Delbourgo, D.-s. Liu, and M. D. Scadron s anti-s dominance of the f(0)(980) meson PLB 446 (1999) 332 hep-ph/9811474
30 J. L. Lucio Martinez and M. Napsuciale a(0)(980) $ \to $ gamma gamma and f(0)(980) $ \to $ gamma gamma: A Consistent description PLB 454 (1999) 365 hep-ph/9903234
31 T. Branz, T. Gutsche, and V. E. Lyubovitskij f0(980) meson as a K anti-K molecule in a phenomenological Lagrangian approach --317, 2008
Eur. Phys. J. A 37 (2008) 303
0712.0354
32 C. Hanhart, Y. S. Kalashnikova, A. E. Kudryavtsev, and A. V. Nefediev Two-photon decays of hadronic molecules PRD 75 (2007) 074015 hep-ph/0701214
33 R. H. Lemmer Calculation of the two-photon decay width of the f(0)(980) scalar meson PLB 650 (2007) 152 hep-ph/0701027
34 M. R. Pennington, T. Mori, S. Uehara, and Y. Watanabe Amplitude Analysis of High Statistics Results on gamma gamma $ \to $ pi+ pi- and the Two Photon Width of Isoscalar States EPJC 56 (2008) 1 0803.3389
35 M. Boglione and M. R. Pennington Determination of radiative widths of scalar mesons from experimental results on gamma gamma $ \to $ pi pi EPJC 9 (1999) 11 hep-ph/9812258
36 N. N. Achasov and G. N. Shestakov Lightest scalar and tensor resonances in gamma gamma $ \to $ pi pi after the Belle experiment PRD 77 (2008) 074020 0712.0885
37 M. N. Achasov et al. The phi(1020) $ \to $ pi0 pi0 gamma decay PLB 485 (2000) 349 hep-ex/0005017
38 M. Boglione and M. R. Pennington Towards a model independent determination of the phi $ \to $ f0 gamma coupling EPJC 30 (2003) 503 hep-ph/0303200
39 KLOE Collaboration Study of the decay $ \phi \to f(0)(980) \gamma \to \pi^+ \pi^- \gamma $ with the KLOE detector PLB 634 (2006) 148 hep-ex/0511031
40 KLOE Collaboration Dalitz plot analysis of $ e^+ e^- \to \pi^0 \pi^0 \gamma $ events at $ \sqrt{s} $ approximately M($ \phi $) with the KLOE detector EPJC 49 (2007) 473 hep-ex/0609009
41 A. Deandrea et al. The s anti-s and K anti-K nature of f0(980) D(s) decays PLB 502 (2001) 79 hep-ph/0012120
42 CLEO Collaboration Study of the semileptonic decay D(s)+ $ \to $ f0(980) e+ nu and implications for B(s) $ \to $ J/psi f(0) PRD 80 (2009) 052009 0907.3201
43 S. Stone and L. Zhang Use of $ B\to J/\psi f_0 $ decays to discern the $ q \bar{q} $ or tetraquark nature of scalar mesons PRL 111 (2013) 062001 1305.6554
44 LHCb Collaboration Measurement of resonant and CP components in $ \bar{B}_s^0\to J/\psi\pi^+\pi^- $ decays PRD 89 (2014) 092006 1402.6248
45 LHCb Collaboration Measurement of the resonant and CP components in $ \overline{B}^0\to J/\psi \pi^+\pi^- $ decays PRD 90 (2014) 012003 1404.5673
46 J. T. Daub, C. Hanhart, and B. Kubis A model-independent analysis of final-state interactions in $ {\overline{B}}_{d/s}^0\to J/\psi \pi \pi $ JHEP 02 (2016) 009 1508.06841
47 B. S. Zou and D. V. Bugg Is f0 (975) a narrow resonance? PRD 48 (1993) R3948
48 Z.-Q. Wang, X.-W. Kang, J. A. Oller, and L. Zhang Analysis on the composite nature of the light scalar mesons f0(980) and a0(980) PRD 105 (2022) 074016 2201.00492
49 Particle Data Group Collaboration Review of Particle Physics Spectroscopy of Light Meson Resonances, Scalar Mesons below 1 GeV,
PTEP 2022 (2022) 083C01
50 CMS Collaboration Evidence for X(3872) in Pb-Pb Collisions and Studies of its Prompt Production at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}} $=5.02\,\,TeV PRL 128 (2022) 032001 CMS-HIN-19-005
2102.13048
51 STAR Collaboration Collaboration Experimental and theoretical challenges in the search for the quark gluon plasma: The STAR Collaboration's critical assessment of the evidence from RHIC collisions Nucl.Phys. A 757 (2005) 102 nucl-ex/0501009
52 PHENIX Collaboration Collaboration Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration Nucl.Phys. A 757 1(2005) 84 nucl-ex/0410003
53 G. Roland, K. Safarik, and P. Steinberg Heavy-ion collisions at the LHC Prog. Part. Nucl. Phys. 77 (2014) 70
54 S. T. Butler and C. A. Pearson Deuterons from High-Energy Proton Bombardment of Matter PR 129 (1963) 836
55 C. B. Dover, U. W. Heinz, E. Schnedermann, and J. Zimanyi Relativistic coalescence model for high-energy nuclear collisions Phys. Rev. C 44 (1991) 1636
56 R. J. Fries, B. Muller, C. Nonaka, and S. A. Bass Hadron production in heavy ion collisions: Fragmentation and recombination from a dense parton phase Phys. Rev. C 68 (2003) 044902 nucl-th/0306027
57 R. J. Fries, B. Muller, C. Nonaka, and S. A. Bass Hadronization in heavy ion collisions: Recombination and fragmentation of partons PRL 90 (2003) 202303 nucl-th/0301087
58 V. Greco, C. M. Ko, and P. Levai Parton coalescence and anti-proton / pion anomaly at RHIC PRL 90 (2003) 202302 nucl-th/0301093
59 V. Greco, C. M. Ko, and P. Levai Parton coalescence at RHIC Phys. Rev. C 68 (2003) 034904 nucl-th/0305024
60 R. C. Hwa and C. B. Yang Scaling behavior at high $ p_{\mathrm{T}} $ and the p/$ \pi $ ratio Phys. Rev. C 67 (2003) 034902 nucl-th/0211010
61 R. C. Hwa and C. B. Yang Recombination of shower partons at high $ p_{\mathrm{T}} $ in heavy ion collisions Phys. Rev. C 70 (2004) 024905 nucl-th/0401001
62 R. J. Fries, V. Greco, and P. Sorensen Coalescence Models For Hadron Formation From Quark Gluon Plasma Ann. Rev. Nucl. Part. Sci. 58 (2008) 177 0807.4939
63 V. Minissale, F. Scardina, and V. Greco Hadrons from coalescence plus fragmentation in AA collisions at energies available at the BNL Relativistic Heavy Ion Collider to the CERN Large Hadron Collider Phys. Rev. C 92 (2015) 054904 1502.06213
64 J.-Y. Ollitrault Anisotropy as a signature of transverse collective flow PRD 46 (1992)
65 A. Gu, T. Edmonds, J. Zhao, and F. Wang Elliptical flow coalescence to identify the $ f_{0} $(980) content Phys. Rev. C 101 (2020) 024908 1902.07152
66 S. Voloshin and Y. Zhang Flow study in relativistic nuclear collisions by Fourier expansion of Azimuthal particle distributions Z. Phys. C 70 (1996) 665 hep-ph/9407282
67 D. Molnar and S. A. Voloshin Elliptic flow at large transverse momenta from quark coalescence PRL 91 (2003) 092301 nucl-th/0302014
68 L. Maiani, A. D. Polosa, V. Riquer, and C. A. Salgado Counting valence quarks at RHIC and LHC PLB 645 (2007) hep-ph/0606217
69 ExHIC Collaboration Multi-quark hadrons from Heavy Ion Collisions PRL 106 (2011) 212001 1011.0852
70 A. Gu and F. Wang Transverse momentum spectra of $ f_0(980) $ from coalescence model 2306.08584
71 STAR Collaboration Particle type dependence of azimuthal anisotropy and nuclear modification of particle production in Au + Au collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}} = $ 200 GeV PRL 92 (2004) 052302 nucl-ex/0306007
72 STAR Collaboration Azimuthal anisotropy in Au+Au collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}} = $ 200 GeV Phys. Rev. C 72 (2005) 014904 nucl-ex/0409033
73 STAR Collaboration Multi-strange baryon elliptic flow in Au + Au collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}} = $ 200 GeV PRL 95 (2005) 122301 nucl-ex/0504022
74 PHENIX Collaboration Scaling properties of azimuthal anisotropy in Au+Au and Cu+Cu collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}} = $ 200 GeV PRL 98 (2007) 162301 nucl-ex/0608033
75 STAR Collaboration Partonic flow and phi-meson production in Au + Au collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}} = $ 200 GeV PRL 99 (2007) 112301 nucl-ex/0703033
76 STAR Collaboration Elliptic flow of identified hadrons in Au+Au collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}= $ 7.7-62.4 GeV Phys. Rev. C 88 (2013) 014902 1301.2348
77 ALICE Collaboration Elliptic flow of identified hadrons in Pb-Pb collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}= $ 2.76 TeV JHEP 06 (2015) 190 1405.4632
78 ALICE Collaboration Anisotropic flow of identified particles in Pb-Pb collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}= $ 5.02 TeV JHEP 09 (2018) 006 1805.04390
79 CMS Collaboration Long-range two-particle correlations of strange hadrons with charged particles in pPb and PbPb collisions at LHC energies PLB 742 (2015) 200 CMS-HIN-14-002
1409.3392
80 CMS Collaboration Elliptic flow of charm and strange hadrons in high-multiplicity pPb collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}} = $ 8.16 TeV PRL 121 (2018) 082301 CMS-HIN-17-003
1804.09767
81 ALICE Collaboration Non-linear flow modes of identified particles in Pb-Pb collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}} = $ 5.02 TeV JHEP 06 (2020) 147 1912.00740
82 ALICE Collaboration Anisotropic flow of identified hadrons in Xe-Xe collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}} = $ 5.44 TeV JHEP 10 (2021) 152 2107.10592
83 ALICE Collaboration Anisotropic flow and flow fluctuations of identified hadrons in Pb-Pb collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}} = $ 5.02 TeV JHEP 05 (2023) 243 2206.04587
84 CMS Collaboration The CMS Experiment at the CERN LHC JINST 3 (2008) S08004
85 CMS Collaboration The CMS trigger system no.~01, P0, 2017
JINST 12 (2017)
CMS-TRG-12-001
1609.02366
86 CMS Collaboration Observation of Correlated Azimuthal Anisotropy Fourier Harmonics in $ pp $ and $ p+Pb $ Collisions at the LHC no.~9, 092301, 2018
PRL 120 (2018)
CMS-HIN-16-022
1709.09189
87 CMS Collaboration Constraints on the chiral magnetic effect using charge-dependent azimuthal correlations in pPb and PbPb collisions at the CERN Large Hadron Collider Phys. Rev. C 97 (2018) 044912 CMS-HIN-17-001
1708.01602
88 CMS Collaboration Description and performance of track and primary-vertex reconstruction with the CMS tracker no.~10, P9, 2014
JINST 9 (2014)
CMS-TRK-11-001
1405.6569
89 M. Gyulassy and X.-N. Wang HIJING 1.0: A Monte Carlo program for parton and particle production in high-energy hadronic and nuclear collisions Comput. Phys. Commun. 83 (1994) 307 nucl-th/9502021
90 GEANT4 Collaboration GEANT4--a simulation toolkit NIM A 506 (2003)
91 A. M. Poskanzer and S. A. Voloshin Methods for analyzing anisotropic flow in relativistic nuclear collisions Phys. Rev. C 58 (1998) 1671 nucl-ex/9805001
92 V. Weisskopf and E. P. Wigner Calculation of the natural brightness of spectral lines on the basis of Dirac's theory Z. Phys. 63 (1930)
93 H. Hull and G. Breit Coulomb Wave Functions Springer Berlin Heidelberg, Berlin, Heidelberg, 1959
link
94 STAR Collaboration Rho0 production and possible modification in Au+Au and p+p collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}} = $ 200 GeV PRL 92 (2004) 092301 nucl-ex/0307023
95 R. Barlow Systematic errors: Facts and fictions in Conference on Advanced Statistical Techniques in Particle Physics, 2002 hep-ex/0207026
96 P. T. Matthews and A. Salam Relativistic theory of unstable particles. 2 PR 115 (1959)
97 R. A. Kycia and S. Jadach Relativistic Voigt profile for unstable particles in high energy physics J. Math. Anal. Appl. 463 (2018) 2 1711.09304
98 PHENIX Collaboration Deviation from quark-number scaling of the anisotropy parameter $ v_2 $ of pions, kaons, and protons in Au+Au collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}} = $ 200 GeV Phys. Rev. C 85 (2012) 064914 1203.2644
99 ALICE Collaboration Higher harmonic flow coefficients of identified hadrons in Pb-Pb collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}} = $ 2.76 TeV JHEP 09 (2016) 164 1606.06057
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