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Quakonium and Related Observables from Proton-Proton to Heavy-Ion Collisions

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Quakonium and Related Observables from Proton-Proton to Heavy-Ion Collisions SnowMass2021 Workshop on Opportuni5es in Hadron Spectroscopy Quakonium and related observables from proton-proton to heavy-ion collisions Elena G. Ferreiro IGFAE, Universidade de San2ago de Compostela, Spain E. G. Ferreiro USC Quarkonium & related observables from pp to AA SnowMass2021 16/12/2020 Old paradigm: the three systems (understanding before 2012) Hot QCD maer: This is where we expect the QGP to be created in central collisions QCD baseline: This is the baseline for “standard” QCD phenomena Cold QCD maer: This is to isolate nuclear effects in absence of QGP, e.g. nuclear pdfs E. G. Ferreiro USC Quarkonium & related observables from pp to AA 1 SnowMass2021 16/12/2020 New paradigm: small systems Totally unexpected: the discovery of correlaons –ridge, flow- in small systems pA & pp • Smooth conOnuaon of heavy ion phenomena to small systems and low density • Small systems as pA and pp show QGP-like features Two serious contenders remain today: • iniOal state: quantum correlaons as calculated by CGC • final state: with (hydrodynamics) or without equilibraon The old paradigm that • we study hot & dense maer properOes in heavy ion AA collisions • cold nuclear maer modificaons in pA • and we use pp primarily as comparison data appears no longer sensible We should examine a new paradigm, where the physics underlying collecOve signals can be the same in all high energy reacOons, from pp to central AA E. G. Ferreiro USC Quarkonium & related observables from pp to AA 2 SnowMass2021 16/12/2020 Why quarkonia? A liWle bit of history PotenOal between q-anO-q pair 4 α V(r) = − s + kr V(r) grows linearly at large distances 3 r Screening of long range confining potenOal r at high enough temperature or density. Debye screening radius λD(T) depends on temperature What happens when the range of the binding force becomes smaller than the radius of the V(r) state? r > λD different states “melOng” at different temperatures due to different binding energies: Debye screening Quarkonia as a QGP thermometer E. G. Ferreiro USC Quarkonium & related observables from pp to AA 3 SnowMass2021 16/12/2020 5.2 Nuclear modification factor RAA 9 where the relevant initial conditions are changed by varying the viscosity to entropy ratio, h/s, and the initial momentum-spaceMeasuring nuclear anisotropy.effects The initial: the temperature nuclear is determinedmodificaon by requir- factor AA ing agreement with charged particle multiplicity and elliptic flow measurements. The model of Du, He, and Rapp usesNuclear a kinetic-ratemodificaon equation factor R to simulateAA the time evolution of bottomo- • RAA<1: suppression nium abundances in ultra-relativistic heavy2 p� ion collisions. It considers medium effects with temperature-dependent binding energies,� � and/�� a� lattice-QCD-based�� equation• R ofAA=1: no nuclear state for the effects fireball evolution. Within� the current = theoretical and experimental uncertainties, both models AA 2 pp • RAA>1: enhancement are in agreement with the results. Ncoll � � /����� PbPb 368/464 µb-1, pp 28.0 pb-1 (5.02 TeV) p < 30 GeV Original moOvaon to measure quarkonium 1.2 T CMS |y| < 2.4 Υ Cent.in nuclear collisions (AA): Signal of QGP 1 68% CL 95% CL 0-100%Observable: RAA vs energy density ϒ(1S) ϒ(2S) ϒ(2S) 0.8 ϒ(2S) ϒ(3S) ϒ(3S) AA • The 3 upsilon states are suppressed R 0.6 Υ with increasing centrality 0.4 0.2 RAA[Υ(1S)] > RAA[Υ(2S)] > RAA[Υ(3S)] 0 0 50 100 150 200 250 300 350 400 => SequenOal melOng <Npart> Figure 5: Nuclear modificationE. G. Ferreiro USC factors for the U( 1S ), UQuarkonium & related observables from pp to AA (2S) and U(3S) mesons as a function 4 of SnowMass2021 16/12/2020 N . The boxes at the dashed line at unity represent global uncertainties: the open box for h parti the integrated luminosity in pp collisions and NMB in PbPb collisions, while the full boxes show the uncertainties of pp yields for U(1S) and U(2S) states (with the larger box corresponding to the excited state). For the U(3S) meson, the upper limits at 68% (green box) and 95% (green arrow) CL are shown. Figure 7 compares centrality-integrated RAA values at psNN = 2.76 TeV to those at 5.02 TeV. The centrality-integrated R for U(1S) is measured to be 0.376 0.013 (stat) 0.035 (syst), to AA ± ± be compared with the result at 2.76 TeV, 0.453 0.014 (stat) 0.046 (syst) [21]. The suppression ± ± at 5.02 TeV is larger by a factor of 1.20 0.15 (in which only the T uncertainty was consid- ⇠ ± AA ered correlated and therefore removed), although the two RAA values are compatible within the uncertainties. The centrality-integrated results for the U(2S) and U(3S) states at 5.02 TeV are R (U(2S)) = 0.117 0.022 (stat) 0.019 (syst) and R (U(3S)) = 0.022 0.038 (stat) AA ± ± AA ± ± 0.016 (syst) (<0.096 at 95% CL). Despite having a bigger binding energy than the already mea- sured y(2S) meson [18, 19, 27], no U(3S) meson signal is found in the PbPb data, in any of the studied kinematic regions. This suggests a pT- and binding-energy-dependent interplay of different phenomena affecting quarkonium states that is yet to be fully understood [49]. Since the suppression is expected to be larger for higher temperatures in the medium, the RAA results for the U(1S) meson at the two different collision energies can provide information on the medium temperature. The temperatures reported in the model of Krouppa and Strickland shown in Fig. 6 are T = 641, 631, and 629 MeV corresponding to 4ph/s = 1, 2, and 3, respec- tively. For the model of Du, He, and Rapp, the temperatures are in the range T = 550–800 MeV. The models, which are also in agreement with the results at 2.76 TeV [12, 50], predict increases ...but the situaon is by far much more complicate pA 1.4 pPb p-Pb sNN = 8.16 TeV R • There are other effects, not related to 1.2 ALICE inclusive J/ψ LHCb prompt J/ψ (PLB 774 (2017) 159 ) colour screening, that induce suppression 1 of quarkonium states 0.8 • These effects are not all mutually 0.6 EPS09NLO + CEM (R. Vogt) nCTEQ15 (J. Lansberg et al.) exclusive EPPS16 (J. Lansberg et al.) 0.4 CGC + NRQCD (R. Venugopalan et al.) CGC + CEM (B. Ducloue et al.) • They should be also taken into account in 0.2 Energy loss (F. Arleo et al.) Transport (P. Zhuang et al.) AA collisions Comovers (E. Ferreiro) 0 −5 −4 −3 −2 −1 0 1 2 3 4 5 y cms Figure 30: Comparison of the• ALICEModificaon [598] and LHCb of [599the] measurements gluon flux of the ini2al-state nuclear modification effect factor ofw J/ Nuclearproduction PDF in in nuclei: nPDF shadowing pPb collisions at psnn = 8.16 TeV with several model calculations [25, 75, 600–604]. Note that the curves labelled nCTEQ15 and EPPS16 are obtained after reweighting the corresponding nuclear PDF sets using LHC heavy-flavour data. Figurew fromGluon Ref. saturaon [598]. at low x: CGC Warning (by JPL): The J.Lansberg et al curves are reweighted nPDF;this should be state; and in fact I am not the first author ... Warning (by MW): point taken. However,• I lookedParton up and propagaon the reference is arxiv: in medium 1610.05382, where inial you/final are firsteffect author w Coherent energy loss Warning (by JPL): Well the reference is incorrect. Just look : nCTEQ and EPPS16 have the same uncertainties; it’s only possible after •reweighting. Quarkonium- I will try to updatehadron the plot interacOon with Acrobat. The final- correctstate ref is [effect26]. w Comover interacOon w Nuclear break-up 1700 It is worth making remarks on some essential issues in the model calculations. Firstly, the fundamental 1701 mechanisms of the heavy-quark• QGP- pairlike production effects? in pA collisions could be quite di↵erent from that in pp 1702 collisions. In particular, when PT (mQ) or less and when one specifically addressed PT dependent E. G. Ferreiro USC ⇡O Quarkonium & related observables from pp to AA 5 SnowMass2021 16/12/2020 1703 quantities as oppose to integrated ones, the perturbative QCD collinear factorisation approach for quarko- 1704 nium production is no longer the most reliable theoretical approach [51, 52]. Remark (by JPL): Please verify 1705 the relevance of [51]. To simplify I would cite review. Maybe [35].As discussed in Secs. 2.2 and 4, the trans- 1706 verse momentum dependent (TMD) factorisation framework should take over the collinear factorisation for 1707 heavy-quark pair production when P m , which makes the nPDFs e↵ect unclear. T ⌧ Q 1708 For evaluating nuclear e↵ects in the TMD factorisation approach, we must clarify how to include 1/3 1709 nuclear size or A enhanced power corrections [605–607] into the leading-twist TMD factorisation ap- 1710 proach [608], although the power corrections in hadronic collisions cannot be factorised beyond the sub- 1711 leading power [67, 609], in general. Besides, we must understand how nuclear dependence comes into 1712 non-perturbative TMD distributions [610]. Interestingly, it has been clarified that the leading-twist TMD 1713 factorisation framework can be recovered by getting rid of higher body scattering corrections in the CGC 1714 framework [542, 611, 612]. Therefore, precautions are required to compare nPDFs with parton saturation 1715 e↵ects. We can study higher twist e↵ects by considering “clean” processes, such as Drell-Yan process in 1716 pA collisions, and semi-inclusive nuclear DIS at the Electron-Ion Collider.
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