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Preview of ATLAS results

This preview provides an overview of the ATLAS results presented at QM2017, covering topics such as quarkonium production, flow in large systems, jet quenching, and photonuclear processes at various collision energies. The results shed light on the initial state dynamics of heavy ion collisions and provide insights into the properties of the quark-gluon plasma.

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Preview of ATLAS results

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  1. Preview of ATLAS results Jiangyong Jia for the ATLAS Collaboration Stony Brook University and Brookhaven National Laboratory

  2. ATLAS results in QM2017 Initial state Quarkonium • Charmonium 5 TeV PbPb • Bottomonium 5 TeV pPb • nPDFs • Photo-nuclear 5 TeV • Z/W production 5 TeV • vn harmonics 5 TeV • Longitudinal dynamics2.76,5 TeV Flow in large systems Jet quenching • RAA of spectra • Jet RAA 5 TeV • Charged particle RAA 5 TeV Collectivity in small systems • Incl. & azimuthal dep. HBT • Ridge via 2PC • Heavy-flavor muon ridge • Ridge via standard cumulants • Ridge via subeventcumulants • FB multi. fluctuation • Jet structure & correlation • Fragmentation 2.76 & 5 TeV • Dijet asymmetry 2.76 TeV • Gamma-jet 5 TeV • γ+γ scattering in UPC • γγμ+μ-, γγγγ 5 TeV

  3. ATLAS results in QM2017 Initial state Quarkonium • Charmonium 5 TeV PbPbJorge Lopez (Tue) • Bottomonium 5 TeV pPb–J. Chen poster –S. Tapia poster • nPDFs • Photo-nuclear 5 TeV – A. Angerami (Tue) • Z/W production 5 TeV – Z. Citron (Wed) Flow in large systems • vn harmonics 5 TeV–S.Mohapatra(Wed) • Longitudinal dynamics 2.76,5 TeV – M.Dumancicposter • RAA of spectra • Jet RAA 5 TeV M. Spousta (Tue) • Charged particle RAA 5 TeV– R. Slovak (Tue) Jet quenching –S.Mohapatra(Wed) – P. Huo poster Collectivity in small systems L. Havener poster – A. Milov poster • Incl. & azimuthal dep. HBT • Ridge via 2PC • Heavy-flavor muon ridge • Ridge via standard cumulants • Ridge via subeventcumulants • FB multi. fluctuation–M. Zhou (Wed) • Jet structure & correlation • Fragmentation 2.76 & 5 TeV • Dijet asymmetry 2.76 TeV • Gamma-jet 5 TeV –M. Clark (Wed) – X. Tu poster –R. Slovak (Tue) –B. Cole (Wed) – L. Havener poster –A.Trzupek (Tue) –P. Steinberg (Wed) –M. Zhou (Wed) – A. Behera poster 12 talks + 11 posters • γ+γ scattering in UPC • γγμ+μ-, γγγγ 5 TeV - M. Dyndal (Tue)

  4. Initial state Photon-photon scalttering in 5 TeV PbPbCONF-2016-025, CONF-2016-111 Photonuclear dijetproduction in 5TeV PbPbCONF-2017-011 Z/W bosons in 5.02 TeV pPb, PbPbCONF-2016-107CONF-2017-010 M. Dyndal (Tue) A. Angerami (Tue) Z. Citron (Wed) M.Dumancicposter

  5. Photon-Photon scattering in UPC 5 TeV PbPb Require simple final state signal w/o any other event activity cross-section ~ αem2 Small cross-section ~ αem4 CONF-2016-025 CERN-EP-2016-316 back-to-back γ (12 and 11 GeV), mγγ=24 GeV 13 events observed, significance: 4.4σ (3.8σ expected) Well described by LO QED (StarLight) Photon flux well calibrated Coherent production σ enhanced by Z4 ~ 4.5x107relative to pp

  6. nPDFs: γ(*)+Pbdijets+Xin UPC 5 TeV PbPb 0 neutron in ZDC many neutrons in ZDC • Sensitive to the nPDF at low x arXiv:1612.05741 • σ measured in dijet kinematic variables • Covers new region of x/Q2 ! Bjorken x in Pb EΥ /Ebeam Proxy for Q2 • Shape described by Pythia+STARlight

  7. nPDFs: Z boson in 5 TeV pPband PbPb Pb+Pb p+Pb EPS09 Z boson as “Glauber baseline”for other hard processes? pPb: RpPb shows slight FB asymmetry consistent with nPDF effects. PbPb: RAA shows no modification in |y| and centrality

  8. Jet quenching Jet RAAin PbPb 5 TeV CONF-2017-009 M. Spousta (Tue) L. Havener poster Jet fragmentation in 2.76/5 TeV PbPb, 5 TeV pPbarXiv:1702.00674, CONF-2017-004, CONF-2017-005 Charged hadron RAA in 5.02 TeV PbPbCONF-2017-012 R. Slovak (Tue) A. Milov poster Gamm-jet 5 TeV PbPbCONF-2016-110 P. Steinberg (Wed)

  9. First measurement: jet RAA in 5 TeV PbPb • 0-10% central jet RAA measured in100 -1 TeV • Clear increase with pT and flattens above 200-300 GeV

  10. First measurement: jet RAA in 5 TeV PbPb • 0-10% central jet RAA measured in 100 -1 TeV • Clear increase with pT and flattens above 200-300 GeV • Consistent with 2.76 TeV results, but much reduced uncertainty • Thanks to the 5 TeV pp reference data taken with same detector condition

  11. Jet RAA: rapidity evolution Double RAA ratio to quantify the suppression relative to mid-rapidity. Interplay between y-dependent flavorcomposition & spectral shape low pT:flat with rapidity High pT: more suppression at forward rapidity first observation!

  12. Comparing to charged hadronRAA 5 TeV PbPb h± RAA measured 1-300 GeV, not inconsistent with flat at high pT Slightly higher than Jet RAA

  13. Jet modification in min-bias pPb? 5 TeV Phys. Lett. B 748 (2015) 392 • Previously, we observe jet RpPb is not modified ATLAS

  14. Jet modification in min-bias pPb? 5 TeV Phys. Lett. B 748 (2015) 392 • Previously, we observe jet RpPb is not modified • Precision 5 TeV pp ref. data allow us to make same statement of no modification for: ATLAS Jet fragmentation function Charged hadron RpPb CONF-2017-004 CONF-2016-108

  15. Modification of Jet fragmentation in PbPb arXiv:1702.00674 ~20% enhancement at high z Enhancement at low z ~10-20% suppression at z~ 0.1

  16. Compare to 5 TeV PbPb arXiv:1702.00674 ~20% enhancement at high z Enhancement at low z ~20% suppression at z~ 0.1 5 TeV

  17. Jet pT dep. of fragmentation in 5 TeV PbPb CONF-2017-005 PbPb 5.02 TeV No jet pTdependenceobserved

  18. Jet quenching with γ-jet 5 TeV PbPb γ-Jet CONF-2016-110 pp Central PbPb • γ provides calibration of jet energy before quenching • medium effects via xJγ= pT,jet/pT,γandΔϕdecorrelation • Central 0-10% PbPb compare to pp • <xJγ> shifted towards lower value Strong energy loss for associated jet.

  19. Jet quenching with γ-jet 5 TeV PbPb γ-Jet CONF-2016-110 pp Central PbPb • γ provides calibration of jet energy before quenching • medium effects via xJγ= pT,jet/pT,γandΔϕdecorrelation • Central 0-10% PbPb compare to pp • <xJγ> shifted towards lower value Strong energy loss for associated jet. • Δϕ distribution consistent with pp data  Little modification of the jet direction.

  20. Quarkonium PbPb 5.02TeV J/Ψand Ψ(2S) CONF-2016-109 Jorge Lopez (Tue) S. Tapia poster pPb5.02TeV J/Ψ,Ψ(2S) & ΥCONF-2015-050, CONF-2015-023 J. Chen poster

  21. Charmonium in 5 TeV PbPb • J/Ψ shows strong yield suppression for both components • Prompt show pT dependence, while non-prompt does not! 0-80% 0-80% Mass or flavor dependence of energy loss? Non-prompt J/ΨRAA Prompt J/ΨRAA • ATLAS measure J/Ψ and Ψ(2s) for pT>9 GeV • Separate prompt, non-prompt (bfeeddown)contributions via Pseudo-proper decay time

  22. Charmonium in 5 TeV PbPb • J/Ψ shows strong yield suppression for both components • Prompt show pT dependence, while non-prompt does not! • J/Ψ and Ψ(2s) are suppressed differently • Prompt: Ψ(2s) is more suppressed,smaller binding energy • Non-prompt: similar since both are created outside QGP from b decay. Prompt Non-prompt • ATLAS measure J/Ψ and Ψ(2s) for pT>9 GeV • Separate prompt, non-prompt (bfeeddown) contributions via Pseudo-proper decay time

  23. Collective flow in large system longitudinal flow decorrelations2.76 & 5 TeV CONF-2017-003 Flow harmonics 5 TeV CONF-2016-105 S.Mohapatra(Wed) P. Huo poster

  24. Longitudinal flow fluctuation in PbPb Particle distribution from one hydro event dN/dϕdη Flow fluctuations in longitudinal direction Both magnitude and phase fluctuate in η asymmetry Event-by-event flow fluctuations in transverse direction EP Twist p(vn,vm) p(Φn,Φm), p(Φn,Φm,ΦL) p(vn) JHEP11(2013)183 PRC 90 (2014) 024905 PRC 92 (2015) 034903

  25. √s dependence of vndecorrelation CMS observable quantify the decorrelation between -η and η Decorrelation of v2,v3 & v4 is 10-20% stronger in 2.76 TeV Extensive set of new observables also measured CONF-2017-003 • p.d.f. of longitudinal decorrelation • Separating vn asymmetry and event-plane twist • Longitudinal decorrelation between vn and vm S.Mohapatra(Wed) P. Huo poster

  26. Collectivity in small systems Inclusive& azimuthal dep. HBT in 5 TeV pPbCONF-2016-027, CONF-2017-008 M. Clark (Wed) Heavy-flavor muonridge in 8 TeV pPbCONF-2017-006 B. Cole (Wed) Ridge via standard cumulants in pp, pPb, PbPbCONF-2017-007 A.Trzupek (Tue) Ridge via subeventcumulants in pp,pPbCONF-2017-002 M. Zhou (Wed) A. Behera poster vn from two-particle corr. in pp,pPb PRL116(2016)172301, arXiv:1609.06213 X. Tu poster

  27. pPbgeometry: pion HBT correlation CONF-2016-027 V Sensitive to modeling of initial geometry, e.g. proton color fluctuation Observe a small but significant FB-asymmtry for the source Comprehensive study of the 3D source: Ro/s/l(kT,Npart, dN/dy, y).

  28. Azimuthal dependent HBT in pPb CONF-2017-008 • Event-shape engineering to further study dependence on forward q2 • Many observables, e.g. Rout/Rside(ϕ-Ψ2), have been measured Smaller ratio in-plane • Source expands more explosively along the event plane • Qualitatively similar to A+A, consistent with hydro-picture

  29. Long-range ridge in pp via 2PC PRL116 (2016)172301 arXiv: 1609.06213 Y(Δϕ)cent= FY(Δϕ)peri+Acos2Δϕ+C First 8 TeV pPb result! No dependence on √s but clear dependence on collision system Dijet backgroundremove via template-fit (improved peripheral sub)

  30. Heavy-flavor μ ridge in 8 TeV pPb h-h μ-h μ-h ridge smaller than h-h ridge • v2μ < v2h, implication on heavy quark thermalization? Uncertainty dominated by hadron background Correlation of 4-6 GeVmuonfrom c & b decay with charged particles CONF-2017-006

  31. Long-range ridge in pp from cumulants PRL116 (2016)172301 arXiv: 1609.06213 Y(Δϕ)cent= FY(Δϕ)peri+Acos2Δϕ+C • Multi-particle cumulant reduces non-flow in pp, but by how much? Clear bias of nonflow Dijet backgroundremove via template-fit (improved peripheral sub)

  32. Long-range collectivity via subeventcumulants arXiv:1701.03830 removes intra-jet correlations removes inter-jet correlations Alternative definition of collectivity? Standard cumulant: collimated azimuthal emission of many particles Subeventcumulant: collimated azimuthal emission of many particles from multiple, distinct η ranges

  33. Long-range collectivity via subeventcumulants arXiv:1701.03830 removes intra-jet correlations removes inter-jet correlations standard 2subevt 4% v2 pPb 5 TeV pp13 TeV 3subevt pPb: methods consistent for Nch>100, but split below that

  34. Long-range collectivity via subeventcumulants arXiv:1701.03830 removes intra-jet correlations removes inter-jet correlations standard 2subevt 4% v2 pPb 5 TeV pp5TeV 3subevt pPb: methods consistent for Nch>100, but split below that pp: 3-subevent gives negative c2{4} in broad range of Nch First observation of c2{4}<0 in 5 TeV pp

  35. v2{4} 3-subevent vs.v2{2} template fit pp 5 TeV pp 13 TeV pPb 5 TeV PRL112,082301(2014) • v2{4}three-subevent< v2{2}template fit as expected • Fluc. of ε2(therefore v2) is driven by fluc. of independent sources • Number of sources Ns can be estimate from v2{4}/v2{2}

  36. Relate to the initial geometry 1606.08170 CONF-2017-002 Sources driving thetransverse flow Source for particle production which drives FB multiplicity fluc. NS? Are these two sources related?

  37. Summary 12 talks and 11 posters • Provides: • New information on the initial state of pPb and PbPb • Detailed study of medium response to hard and soft probes in PbPb • Improved understanding of collectivity in small systems https://twiki.cern.ch/twiki/bin/view/AtlasPublic/HeavyIonsPublicResults • 12 new results will be presented in • Comprehensive study of PbPb, pPb and ppsystems

  38. ATLAS results in QM2017 Initial state Quarkonium • Charmonium 5 TeV PbPbJorge Lopez (Tue) • Bottomonium 5 TeV pPb–J. Chen poster –S. Tapia poster • nPDFs • Photo-nuclear 5 TeV – A. Angerami (Tue) • Z/W production 5 TeV – Z. Citron (Wed) Flow in large systems • vn harmonics 5 TeV–S.Mohapatra(Wed) • Longitudinal dynamics 2.76,5 TeV – M.Dumancicposter • RAA of spectra • Jet RAA 5 TeV M. Spousta (Tue) • Charged particle RAA 5 TeV– R. Slovak (Tue) Jet quenching –S.Mohapatra(Wed) – P. Huo poster Collectivity in small systems L. Havener poster – A. Milov poster • Incl. & azimuthal dep. HBT • Ridge via 2PC • Heavy-flavor muon ridge • Ridge via standard cumulants • Ridge via subeventcumulants • FB multi. fluctuation–M. Zhou (Wed) • Jet structure & correlation • Fragmentation 2.76 & 5 TeV • Dijet asymmetry 2.76 TeV • Gamma-jet 5 TeV –M. Clark (Wed) – X. Tu poster –R. Slovak (Tue) –B. Cole (Wed) – L. Havener poster –A.Trzupek (Tue) –P. Steinberg (Wed) –M. Zhou (Wed) – A. Behera poster 12 talks + 11 posters • γ+γ scattering in UPC • γγμ+μ-, γγγγ 5 TeV - M. Dyndal (Tue)

  39. BACKUP

  40. Longitudinal dynamics • Forward-backward multiplicity correlation initial system size vsη Number of sources same in pp, pPb and PbPb collisions, control by Nch.

  41. Compare with PYTHIA8 and EPOS-LHC • Tuned to dN/dη and Nch distribution via MPI • Models: • Over-estimate the SRC • Under-estimate the LRC

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