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 Flow in large systems
γ+γ scattering in UPC
γγμ+μ-, γγγγ 5 TeV
Charmonium 5 TeV PbPb
Bottomonium 5 TeV pPb
nPDFs
Photo-nuclear 5 TeV
Z/W production 5 TeV
vn harmonics 5 TeV
Longitudinal dynamics 2.76,5 TeV
Flow in large systems
Jet quenching
Jet structure & correlation
Fragmentation 2.76 & 5 TeV
Dijet asymmetry 2.76 TeV
Gamma-jet 5 TeV
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 subevent cumulants
FB multi. fluctuation

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

4. Initial state M. Dyndal (Tue) A. Angerami (Tue) Z. Citron (Wed)
Photon-photon scalttering in 5 TeV PbPb CONF , CONF
Photonuclear dijet production in 5TeV PbPb CONF
Z/W bosons in 5.02 TeV pPb, PbPb CONF CONF
M. Dyndal (Tue)
A. Angerami (Tue)
Z. Citron (Wed)
M.Dumancic poster

5. Photon-Photon scattering in UPC 5 TeV PbPb
Coherent production σ enhanced by Z4 ~ 4.5x107 relative to pp
Require simple final state signal w/o any other event activity
Well described by LO QED (StarLight)
Photon flux well calibrated
cross-section ~ αem2
CONF
Small cross-section ~ αem4
13 events observed, significance:
4.4σ (3.8σ expected)
CERN-EP
back-to-back γ (12 and 11 GeV), mγγ=24 GeV

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

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

8. Jet quenching Jet RAA in PbPb 5 TeV CONF-2017-009
M. Spousta (Tue)
L. Havener poster
Jet fragmentation in 2.76/5 TeV PbPb, 5 TeV pPb arXiv: , CONF , CONF
Charged hadron RAA in 5.02 TeV PbPb CONF
R. Slovak (Tue)
A. Milov poster
Gamm-jet 5 TeV PbPb CONF
P. Steinberg (Wed)

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

10. First measurement: jet RAA in 5 TeV PbPb
0-10% central jet RAA measured in TeV
Clear increase with pT and flattens above 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.
low pT: flat with rapidity
High pT: more suppression at forward rapidity
first observation!
Interplay between y-dependent flavor composition & spectral shape

12. Comparing to charged hadron RAA 5 TeV PbPb
h± RAA measured 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
CONF
CONF
Charged hadron RpPb

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

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

17. Jet pT dep. of fragmentation in 5 TeV PbPb
CONF
PbPb 5.02 TeV
Similar to 2.76 TeV
No jet pT dependence observed

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

19. Jet quenching with γ-jet 5 TeV PbPb
γ provides calibration of jet energy before quenching
medium effects via xJγ= pT,jet/pT,γ and Δϕ decorrelation
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.
γ-Jet
CONF pp
Central PbPb

20. Quarkonium PbPb 5.02TeV J/Ψ and Ψ(2S) CONF-2016-109 Jorge Lopez (Tue)
S. Tapia poster
pPb 5.02TeV J/Ψ, Ψ(2S) & Υ CONF , CONF
J. Chen poster

21. Charmonium in 5 TeV PbPb 0-80% 0-80%
ATLAS measure J/Ψ and Ψ(2s) for pT>9 GeV
Separate prompt, non-prompt (b feeddown) contributions via Pseudo-proper decay time
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/Ψ RAA
Prompt J/Ψ RAA

22. Charmonium in 5 TeV PbPb Prompt Non-prompt
ATLAS measure J/Ψ and Ψ(2s) for pT>9 GeV
Separate prompt, non-prompt (b feeddown) contributions via Pseudo-proper decay time
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

23. Collective flow in large system
longitudinal flow decorrelations 2.76 & 5 TeV CONF
Flow harmonics 5 TeV CONF
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
EP Twist
Event-by-event flow fluctuations in transverse direction
p(vn,vm)
p(Φn,Φm), p(Φn,Φm,ΦL)
p(vn)
JHEP11(2013)183
PRC 90 (2014)
PRC 92 (2015)

25. √s dependence of vn decorrelation
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
p.d.f. of longitudinal decorrelation
Separating vn asymmetry and event-plane twist
Longitudinal decorrelation between vn and vm
CONF
S.Mohapatra(Wed)
P. Huo poster

26. Collectivity in small systems
Inclusive & azimuthal dep. HBT in 5 TeV pPb CONF , CONF
M. Clark (Wed)
Heavy-flavor muon ridge in 8 TeV pPb CONF
B. Cole (Wed)
Ridge via standard cumulants in pp, pPb, PbPb CONF
A.Trzupek (Tue)
Ridge via subevent cumulants in pp, pPb CONF
M. Zhou (Wed)
A. Behera poster
vn from two-particle corr. in pp, pPb PRL116(2016)172301, arXiv:
X. Tu poster

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

28. Azimuthal dependent HBT in pPb
CONF
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
Dijet background remove via template-fit (improved peripheral sub)
PRL116 (2016)172301
arXiv:
Y(Δϕ)cent = FY(Δϕ)peri+Acos2Δϕ+C
First 8 TeV pPb result!
No dependence on √s but clear dependence on collision system

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

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

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

33. Long-range collectivity via subevent cumulants
arXiv:
removes intra-jet correlations
removes inter-jet correlations
pp 13 TeV
standard
2subevt
4% v2
pPb 5 TeV
3subevt
pPb: methods consistent for Nch>100, but split below that

34. Long-range collectivity via subevent cumulants
arXiv:
removes intra-jet correlations
removes inter-jet correlations
standard
2subevt
4% v2
pPb 5 TeV
pp 5 TeV
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
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}
PRL112,082301(2014)

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

37. Summary 12 new results will be presented in 12 talks and 11 posters
Comprehensive study of PbPb, pPb and pp systems
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

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

39. BACKUP

40. Longitudinal dynamics
Forward-backward multiplicity correlation initial system size vs η
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