1. Jet Event Topology as a probe of QGP in heavy-ion collisions
Shi-Yong Chen
(Central China Normal University)
in collaboration with :Ben-Wei Zhang, En-Ke Wang and Wei Dai
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2. Outline: Motivation event shape in pp and PbPb collisions
Results and discussion
Summary and outlook
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3. Motivation
Xin - Nian Wang, M.Gyulassy, PRL68(1992)1480
Quenching of full jet observable is one of the most valuable hard probe, leading and subleading jets, what about the modification of third or forth jets...?
Show jet quenching effect manifest itself on global obsverables: event shape.
J. KAPUSTA and D. STROTTMAN, PLB (1982) 106 (1) :33-37
G. Hanson, G. S. Abrams, et. al... Phys. Rev. Lett. 35, 1609
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4. Definition of event shape
transverse Thrust
transverse Sphericity
The individual eigenvalues are normalized
and ordered such that
J. KAPUSTA and D. STROTTMAN, PLB (1982) 106 (1) :33-37
G. Hanson, G. S. Abrams, et. al... Phys. Rev. Lett. 35, 1609
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5. . event shape jet like sphere like
both thrust and sphericity describe the isotropy distribution of energy-momentum in a collision
final state hadrons and full jets
J. KAPUSTA and D. STROTTMAN, PLB (1982) 106 (1) :33-37
G. Hanson, G. S. Abrams, et. al... Phys. Rev. Lett. 35, 1609
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6. event shape measurement in pp:
many uses: 1, Fit strong coupling constant; 2, Fit Colour factor; 3, Tuning of Monte Carlos models; 4, Study analytical hadronization models. CDF： thrust, hadrons. arXiv: ALICE: sphericity, charged hadrons. arXiv: ATLAS：sphericity, thrust, jets. arXiv: thrust, sphericity, hadrons. arXiv: CMS: thrust, charged hadrons. arXiv: thrust,charged jets. arXiv:
NNLL and NLO+Resummation
arXiv: arXiv:
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7. pp baseline:POWHEG+PYTHIA
NLO partonic QCD dijet process: POWHEG
The POWHEG BOX is a general computer framework for implementing NLO calculations in shower Monte Carlo programs according to the POWHEG method. Homepage for POWHEG:
parton shower and hadronization: pythia6
full jets reconstruction: Fastjet
our baseline are compare with ATLAS data.
S. Alioli, K. Hamilton, P. Nason, C. Oleari and E. Re, JHEP 1104 (2011) 081
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8. pp baseline:POWHEG+PYTHIA
our baseline are compared with ATLAS data.
arXiv:
arXiv:
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9. parton energy loss:
the radiative energy loss during t1,t2 by probability:
gluon radiate spructurm:
the collisional energy loss: Hard Thermal Loop calculation
Xiao-feng Guo , Xin-Nian Wang Phys. Rev. Lett. 85 (2000)
Ben-Wei Zhang , Xin-Nian Wang Phys. Rev. Lett. 93 (2004)
Medium expansion:
2+1 D viscose hydrodynamic
Comput. Phys.Commun 199(2016) 61
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10. event shape in PbPb event selection:
the symmetrical characteristic in pp collisions is modified
low region: enhancement high region: suppression
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11. event shape in PbPb initial jet prodtion position：
the symmetrical characteristic of events may be modified by:
initial jet prodtion position：
jets transport through QGP with different lengh
flavour dependence of parton energy loss
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12. initial jet prodtion position
partons produced at central point ：r0(0,0,0)
Glauber model
the modification for transverse sphericity is slightly weaker
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13. process dependence of event shape:
to clarify the modifications from flavour dependence of parton energy loss , we categorize the full events to:
quark jets dominant process
gluon jets dominant process
quark & gluon jets process
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14. process dependence of event shape:
Distinct behaviour can be found among these three processes. Gluon jets dominant events are much more spherical.
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15. process dependence of event shape:
nuclear modification ratio for these three processes:
all the three processes are more spherical, opposite to full process.
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16. number of jets in event:
quark jets dominant process:
quark & gluon jets process:
gluon jets dominant process:
the portion for the three process is changed
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17. different energy loss pattern of quark and gluon:
previous calculations is based on:
other parton energy loss pattern and fit inclusive jet Raa:
case 1: hybrid model
case 2:
Jorge Casalderrey-Solana, Doga Can Gulhan .et .al JHEP10(2014)019
Xiaofang Chen , Hanzhong Zhang , Ben-Wei Zhang, Enke Wang J.Phys. 37 (2010)
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18. different energy loss pattern of quark and gluon:
nuclear modification ratio from different energy loss pattern:
event shape is sensitive to the portion of quark and gluon jets dominat process, providing opportunity to study flavour dependence of parton energy loss
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19. Summy and outlook
transverse Thrust and transverse sphericity can be sucessfully described
by POWHEG+PYTHIA
distinct behaviour can be found between quark and gluon dominant process
medium modification of event shape is sensitive to the portion of quark and gluon jets dominat process, providing opportunity to study flavour dependence of parton energy loss
our calculations are base on QCD dijet process, what about boson tagged jets events or heavy flavour jets events?
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20. Thank you for your attention !
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