niharranjan sahoo...1 semi-inclusive γ+jet and h+jetin star experimentniharranjan sahoo shandong...
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1
Semi-inclusive γ+jet and h+jet in STAR experiment
Nihar Ranjan SahooShandong University (SDU), Qingdao, China
Nihar Sahoo (SDU)
High Energy Nuclear Physics in China (HENPIC), 27 Feb 2020
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Jet quenching at RHIC
• Suppression of inclusive charged/neutral hadrons at high-pT• No suppression of vector-bosons (γ, W, Z) • Away-side jet suppression
Indication of Hot-dense QCD medium (QGP)
Early RHIC measurements
Nihar Sahoo, SDU 2
1/N
trig
dN/d
φ
STAR: PRL 91, 072304 (2003 )
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Jet Quenching Inclusive jet
Semi-Inclusive jet
Jet shapeDijet imbalanceDihadron correlations
Softdrop grooming
Jet mass
Inclusive hadron pT spectrum
γ+jetπ0+jet hadron+jet Jet+hadron correlation
Jet-like correlation
Jet Fragmentation Functions
Z+jet
A+A p+pDijetzg
Rg
Large angle deflectionγ+hadron correlation
XJ
Jet splitting
Jet substructure
Dijet acoplanarity
RAA Nuclear modification factorIAA
Jet geometry engineering
Quark/gluon jet
Jet ChargeHeavy flavor-jet
RCPICP
RpA Jet v2
Jet modification in p+p high multiplicity events
3
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Jet as a tool to study QCD at collider experiments
Nihar Sahoo (SDU) 4
In hot-dense QCD medium:
• Quantitative estimation of parton energy loss Its dependence on path length, Casmiri factor, initial parton energy, etc.
• Redistribution of lost energy inside the medium [Jet R]
• RHIC vs. LHC [dependence on temp. and initial gluon density] What about lower beam energy or small system in HIC?
• Modification of jet shape inside a hot QCD medium RHIC vs. LHC
• Deflection of recoil jet
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Nihar Sahoo (SDU) 5
Contents:
• γ+jet and π0+jet in Heavy-Ion collisions• Jet-R dependence of Jet-quenching • Large angle deflection of π0+jet
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γ+jet and h+jet in A+A/p+p collisions
Nihar Sahoo (SDU) 6
Dijet/h+jet: qg ! gqqq ! qqq̄q ! q̄qgg ! gg
...
AAACTHicbZDNS8MwGMbT+TXrV9Wjl+AQPJVWBnocevE4wX3AWkaaZV1Y2rRJqoyyP9CLB2/+FV48KCKYbj3swxcCT37P++bjCRJGpXKcd6Oysbm1vVPdNff2Dw6PrOOTtuSZwKSFOeOiGyBJGI1JS1HFSDcRBEUBI51gfFf4nSciJOXxo5okxI9QGNMhxUhp1LdwGkJP0HCkkBD8GYap55lpusSKrWd6ARJ5OoXL3gL1zHDlrFAz27b7Vs2xnVnBdeGWogbKavatN2/AcRaRWGGGpOy5TqL8HAlFMSNT08skSRAeo5D0tIxRRKSfz8KYwgtNBnDIhV6xgjO6OJGjSMpJFOjOCKmRXPUK+J/Xy9Twxs9pnGSKxHh+0TBjUHFYJAsHVBCs2EQLhAXVb4V4hATCSudv6hDc1S+vi/aV7dbt+kO91rgt46iCM3AOLoELrkED3IMmaAEMXsAH+ALfxqvxafwYv/PWilHOnIKlqmz/Adp3sx0=
qg ! q�qq̄ ! g�
AAACI3icbVDLSsNAFJ34rPVVdelmsAiuSiIFxVXRjcsK9gFNKDfTSTp0JklnJkoJ/Rc3/oobF0px48J/cdpmYVsPDBzOOZc79/gJZ0rb9re1tr6xubVd2Cnu7u0fHJaOjpsqTiWhDRLzWLZ9UJSziDY005y2E0lB+Jy2/MHd1G89UalYHD3qUUI9AWHEAkZAG6lbuhniELuShX0NUsbPeIjdEIQA7LpFw32Q2XC8kAjzRLdUtiv2DHiVODkpoxz1bmni9mKSChppwkGpjmMn2stAakY4HRfdVNEEyABC2jE0AkGVl81uHONzo/RwEEvzIo1n6t+JDIRSI+GbpADdV8veVPzP66Q6uPYyFiWpphGZLwpSjnWMp4XhHpOUaD4yBIhk5q+Y9EEC0abWoinBWT55lTQvK061Un2olmu3eR0FdIrO0AVy0BWqoXtURw1E0At6Qx/o03q13q2J9TWPrln5zAlagPXzCx9So/s=
γ+jet:
γ
JetJet
γ
Nihar Sahoo
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Challenges in heavy-ion collisions to study jet
In Heavy-Ion collisions, Soft background energy fluctuationsand uncorrelated jet contributions make it difficult.
Recently, in RHIC/LHC experiments many techniques/tools are developed to overcome this hurdle
• Jet+hadron, γ+hadron, h+Jet, γ+Jet, Dijet, Inclusive jet, SoftDrop-grooming, etc.
Nihar Sahoo (SDU) 7
p+ p ! jet + jet Au + Au ! X
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Jet study in heavy-ion collisions
Nihar Sahoo (SDU) 8
• Inclusive hadron spectrum ( RAA )• Jet-like azimuthal correlation (IAA : Di-hadron, γ+hadron, Z+hadron (LHC) correlations )• Semi-inclusive recoil jet (IAA: h+jet, γ+jet, Z+jet, etc)• Inclusive jet measurement (RAA)
Difference between RAA and IAA :
Different ways to study jet-quenching:
Hot and dense QCD medium
VacuumAAACGXicbVDLSgMxFM34rPVVdekmWARXZcYHuizWRZct2Ae0pWQyd9rQJDMkGaEM7We48VfcuFDEpa78G9PHQlsPXO7hnHtJ7vFjzrRx3W9nZXVtfWMzs5Xd3tnd288dHNZ1lCgKNRrxSDV9ooEzCTXDDIdmrIAIn0PDH5QmfuMBlGaRvDfDGDqC9CQLGSXGSt2c21YCt0NFaFqODB4TGeBxAFIDHldLd3gsIGCJGKV1QhPbcTeXdwvuFHiZeHOSR3NUurnPdhDRRIA0lBOtW54bm05KlGGUwyjbTjTEhA5ID1qWSiJAd9LpZSN8apUAh5GyJQ2eqr83UiK0HgrfTgpi+nrRm4j/ea3EhDedlMk4MSDp7KEw4dhEeBITDpgCavjQEkIVs3/FtE9sTMaGmbUheIsnL5P6ecG7KFxVL/PF23kcGXSMTtAZ8tA1KqIyqqAaougRPaNX9OY8OS/Ou/MxG11x5jtH6A+crx+FB6Ck
�hardAB = �hardpp
AAACIHicbVDLSsNAFJ3UV62vqEs3g0VwVVItVhdCrRuXFewDmlomk2k7dCYJMxOhhPgnbvwVNy4U0Z1+jZM0iloPDBzOuffOvccJGJXKst6N3Nz8wuJSfrmwsrq2vmFubrWkHwpMmthnvug4SBJGPdJUVDHSCQRB3GGk7YzPE799Q4SkvnelJgHpcTT06IBipLTUN6t2OiMSxI1tSYcc9aOzenwdjZBwY3gKb7/UINCqLThMnb5ZtEpWCjhLyhkpggyNvvlmuz4OOfEUZkjKbtkKVC9CQlHMSFywQ0kChMdoSLqaeogT2YvS5WK4pxUXDnyhn6dgqv7siBCXcsIdXcmRGsm/XiL+53VDNTjuRdQLQkU8PP1oEDKofJikBV0qCFZsognCgupdIdb3I6x0poU0hJMER98nz5LWQal8WKpcVoq1ehZHHuyAXbAPyqAKauACNEATYHAHHsATeDbujUfjxXidluaMrGcb/ILx8QkLMqTi
à RAA
à IAA
⇠ OA+B(pT , ⌘,�)Op+p(pT , ⌘,�)
AAACKHicbVDLSsNAFJ3UV62vqks3g0WotJTEB7qz1o07K/QFTQmT6aQdOkmGmYlQQj7Hjb/iRkSRbv0Sp20W2nrgwuGce7n3HpczKpVpTozMyura+kZ2M7e1vbO7l98/aMkwEpg0cchC0XGRJIwGpKmoYqTDBUG+y0jbHd1N/fYTEZKGQUONOen5aBBQj2KktOTkb2xJfdsTCMcPTnxbqiVF7sSNpGwThcrQ5kN6mkwtXuL/WU6+YFbMGeAysVJSACnqTv7d7oc48kmgMENSdi2Tq16MhKKYkSRnR5JwhEdoQLqaBsgnshfPHk3giVb60AuFrkDBmfp7Ika+lGPf1Z0+UkO56E3F/7xupLzrXkwDHikS4PkiL2JQhXCaGuxTQbBiY00QFlTfCvEQ6dSUzjanQ7AWX14mrbOKdV65fLwoVGtpHFlwBI5BEVjgClTBPaiDJsDgGbyCD/BpvBhvxpcxmbdmjHTmEPyB8f0D+Cil6A==
�hardAB = TAB �hardpp
AAACJ3icbVDLSgMxFM3UV62vUZdugkVwVWZ8oBul1o3LCn1Bpw6ZTKYNTWaGJCOUYfwaN/6KG0FFdOmfmE4raPVA4OSce5N7jxczKpVlfRiFufmFxaXicmlldW19w9zcaskoEZg0ccQi0fGQJIyGpKmoYqQTC4K4x0jbG16O/fYtEZJGYUONYtLjqB/SgGKktOSa507+RiqInzmS9jly04tadpMOkPAzeAYb+R3efZtxrE1HcJgXuGbZqlg54F9iT0kZTFF3zWfHj3DCSagwQ1J2bStWvRQJRTEjWclJJIkRHqI+6WoaIk5kL81nzOCeVnwYREKfUMFc/dmRIi7liHu6kiM1kLPeWPzP6yYqOO2lNIwTRUI8+ShIGFQRHIcGfSoIVmykCcKC6lkh1vsjrHS0JR2CPbvyX9I6qNiHlePro3K1No2jCHbALtgHNjgBVXAF6qAJMLgHj+AFvBoPxpPxZrxPSgvGtGcb/ILx+QUMaKdF
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Jet-like γdir+hadron and π0+hadron correlations STAR: PLB 760 (2016) 689
p+p 200 GeV collisions Au+Au 200 GeV collisions
• γrich enriched sample of γdir• In p+p collisions, uncorrelated background is negligible compared to Au+Au
Mid-rapidity: |η| < 1.0 12 < pTγ/π0 < 20 GeV/c
Nihar Sahoo (SDU) 9
Δφ = φtrig - φhadron
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γdir+hadron and π0+hadron correlations
IAA(x) =Y Au+Au(x)
Y p+p(x)
Nihar Sahoo (SDU) 10
• Soft associated particles are less suppressed compared with high pT• Within uncertainty, no trigger (γdir/ π0) bias can be observed
STAR: PLB 760 (2016) 689
Nuclear Modification factor
LHC: Dennis V. Perepelitsa, QM19
xh,γ/Z = pTch / pTγ/Z
zT = pTtrigpT,ihadron
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IAA(x) =Y Au+Au(x)
Y p+p(x)
Nihar Sahoo (SDU) 11
STAR: PLB 760 (2016) 689
Nuclear Modification factor
LHC: Dennis V. Perepelitsa, QM19
xh,γ/Z = pTch / pTγ/Z
γ/Z + jet: RHIC vs. LHC
LHC vs. RHIC: Almost same suppression(Caveat: centrality, phase space, etc.)
zT = pTtrigpT,ihadron
• Soft associated particles are less suppressed compared with high pT• Within uncertainty, no trigger (γdir/ π0) bias can be observed
γdir+hadron and π0+hadron correlations
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Nihar Sahoo (SDU) 12
Jet transport and jet-induced medium excitation in CoLBT-hydro simulations.
γdir+hadron: Theoretical development (CoLBT-hydro)
Depletion of soft hadrons in γ direction→ Diffusion wake left behind by the jet in QGP.
W. Chen et al., PLB 777 (2018) 86–90
Data can be well reproducible by this model.
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Nihar Sahoo (SDU) 13
Semi-inclusive γ+jet and π0+jetusing jet reconstruction
Ongoing work in the STAR experiment:
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π0/γ
Recoil jet region
Trigger tower
STAR TPC charged tracks
STAR BEMC hits
1-0.5-
00.5
1h
3- 2-1-
0 12
3
f
0
2
4
6
8
10
[GeV
/c]
Tp
-Trigger EventgAu+Au 200 GeV [2014], Event number=37362, Run number=15098037
Jet study in a high soft-background energy environment
In Heavy-Ion collisions: Soft-background energy fluctuations and uncorrelated jet background contributions make life difficult.
γ
Nihar Sahoo (SDU) 14
One trigger event
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15Nihar Sahoo (SDU)
Signal + Bg.
Bg.
Mixed event: Uncorrelated jet subtraction
Same Event (SE) and Mixed Event (ME): same background energy density
An important tool to study semi-inclusive jet measurement at mid- and forward-rapidity.
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6-10
5-10
4-10
3-10
2-10
1-10
1
10
]-1) [
(GeV
/c)
jet
h d
reco
,ch
T,je
t/(d
pje
tsN2
) dtri
g(1
/N
Au+Au 200 GeV, 0-15% = 0.2jet RTanti-k
+jetrichg
< 11 GeV [SE]Ttrig9 < E
< 15 GeV [SE]Ttrig11 < E
ME
= 0.5jetR
10- 0 10 20 30 A) [GeV/c]× r - raw,ch
T,jet (= preco,ch
T,jetp
1
10
ME
SE
10- 0 10 20 30 A) [GeV/c]× r - raw,ch
T,jet (= preco,ch
T,jetp
1
10
STAR PreliminarySTAR Preliminary
γrich+jet at mid-rapidity in Au+Au collisions
A clear trigger dependence can be seen.• γrich enriched sample of γdir
Rjet = 0.2 Rjet = 0.5
Recoil charged jet spectrums for different trigger ET windows
STAR: NiharSahoo, QM2019
Nihar Sahoo (SDU) 16
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Nihar Sahoo (SDU) 17
γdir+jet
π0+jet
γdir+jet/π0+jet at mid-rapidity in Au+Au collisions
STAR: Nihar SahooHP2018, QM2019
After full correction: uncorrelated jet bkg. and detector effects
Recoil charged jet spectrums for different trigger ET windows and jet radii
Work is underway to improve systematic uncertainties and also 15 < ETtrig < 20 GeV.
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2 4 6 8 10 12 14 16 18 20
1-10
1
PYTH
IAAAI Au+Au 200 GeV, 0-15%
= 0.2jet RTanti-kSTAR Preliminary
< 15 GeV/cconst.T
< 11 GeV, ptrigT9 < E
2 4 6 8 10 12 14 16 18 20 [GeV/c]ch
T,jetp
1-10
1
PYTH
IAAAI
< 15 GeV/cconst.T
< 15 GeV, ptrigT11 < E
+jet0p +jetdirg
5 10 15 20 251−10
1
PYTH
IAAAI Au+Au 200 GeV, 0-15%
= 0.5jet RTanti-k
STAR Preliminary
< 11 GeVtrigT9 < E
5 10 15 20 25 [GeV/c]ch
T,jetp
1−10
1
PYTH
IAAAI
< 15 GeVtrigT11 < E +jet0π +jet
dirγ
Nuclear Modification factor
Compelling observations at RHIC:• Recoil jet with Rjet =0.2 à strong suppression;
• Same level of suppression for γdir+jet and π0+jetNihar Sahoo (SDU) 18
Rjet = 0.2
STAR: Nihar Sahoo, HP2018,QM2019
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Nuclear Modification factor: Au+Au 200 GeV
2 4 6 8 10 12 14 16 18 20
1-10
1
PYTH
IAAAI Au+Au 200 GeV, 0-15%
= 0.2jet RTanti-kSTAR Preliminary
< 15 GeV/cconst.T
< 11 GeV, ptrigT9 < E
2 4 6 8 10 12 14 16 18 20 [GeV/c]ch
T,jetp
1-10
1
PYTH
IAAAI
< 15 GeV/cconst.T
< 15 GeV, ptrigT11 < E
+jet0p +jetdirg
5 10 15 20 251−10
1
PYTH
IAAAI Au+Au 200 GeV, 0-15%
= 0.5jet RTanti-k
STAR Preliminary
< 11 GeVtrigT9 < E
5 10 15 20 25 [GeV/c]ch
T,jetp
1−10
1
PYTH
IAAAI
< 15 GeVtrigT11 < E +jet0π +jet
dirγ
Compelling observations at RHIC:• Recoil jet with Rjet =0.2 à strong suppression;
whereas for Rjet=0.5 à relatively less suppression. • Same level of suppression for γdir+jet and π0+jet
Nihar Sahoo (SDU) 19
Rjet = 0.2 Rjet = 0.5
STAR: Nihar Sahoo, HP2018,QM2019
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In-medium recoil jet suppression at RHIC and LHC
Nihar Sahoo (SDU) 20
Larger medium-induced recoil jet yield suppression for R=0.2 than for R=0.5
From this γdir+jet and π0+jet measurement and h+jet [PRC 96, 024905 (2017)];What do we observe?
R=0.5
R=0.2
In-medium parton shower
This level of recovery in jet suppression at RHIC energy has not been yetobserved at the LHC.• Different techniques for measuring jet in different experiments• Does it indicate that jet-quenching at RHIC and LHC are different?
Jet-shape modification
[We are exploring in current measurement to address this in some extent.]
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Dijet Δφ angular correlation:A large angle deflection in HICs
21Nihar Sahoo (SDU)
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22
F. D’Eramo, K. Rajagopal, Y. Yin: JHEP01(2019)172
Single scattering in a brick of QGP
In hot-dense QCD • Can we observe this effect?• What is the parton momentum range? • What is the QCD medium response? Equally important to study this effect in the cold QCD matter?
Nihar Sahoo (SDU)
Rutherford Scattering like, ggàgg
QCD Molière Scattering:A rare large angle scattering
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Δφ
MGyulassy QM2019
• Convolution of Vaccum Sudakov and Medium induced transverse deflection; J. P. Blaizot,L. D. McLerran, PRD34, 2739 (1986)
• Color Magnetic Monopole: J. Liao and E. Shuryak , PRL102 (2009)
Δφ
Dijet acopanarity
Nihar Sahoo (SDU) 23
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24
Search for the large angle deflection
Scattering of a recoil-jet off quasi-particlesin the QGP à Intra-jet broadening (Δφ)
Nihar Sahoo (SDU)
At small angle Gaussian ShapeAt large angle Rutherford Scattering
Dijet in p+p and Au+Au
• No significant yield at large angular deviation in p+p
• STAR Exp.- Data analysis is underway in Au+Au collision
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Nihar Sahoo (SDU) 25
Summary and outlook• STAR has produced compelling results on γdir+ hadron correlations and
recent γdir+ jet (and π0+jet) measurement at the top RHIC energy.• Provide very important information on in-medium parton energy loss at
RHIC.• “Larger medium-induced recoil jet yield suppression for R=0.2 than for R=0.5
in γdir+ jet and π0+jet (h+jet)”This is an important observation at RHIC that needs further study at both
RHIC and LHC experiments, and in theory.
• Large angle deflection: a detail study is ongoing in STAR to understandthe QGP medium response
• In addition, work is underway using semi-inclusive γdir+ jet and h+jetmeasurement at Mid-rapidity and in upcoming STAR forward detectorupgrade to study the cold QCD matter [not covered in this talk]
Thank you!
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Backup
Nihar Sahoo (SDU) 26
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Nihar Sahoo (SDU) 27
γdir+hadron correlations: Fragmentation Function π0+hadron correlations at mid-rapidity
• Per trigger yield is modified• Away-side yields show suppression in
Au+Au collisions as compared with p+p zT = pTtrigpT,ihadron
D(zT) : integrated away-side and near-side charged-hadron yields per trigger
STAR: PLB 760 (2016) 689
γdir+hadron and π0+hadron correlationsMid-rapidity: |η| < 1.0
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Nihar Sahoo (SDU) 28
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6-10
5-10
4-10
3-10
2-10
1-10
1
10]-1
) [(G
eV/c
)je
th
dre
co,c
hT,
jet
/(d p
jets
N2) d
trig
(1/N
Au+Au 200 GeV, 0-15% = 0.2jet RTanti-k
+jet0p
< 11 GeV [SE]Ttrig9 < E
< 15 GeV [SE]Ttrig11 < E
ME
= 0.5jetR
10- 0 10 20 30 A) [GeV/c]× r - raw,ch
T,jet (= preco,ch
T,jetp
1
10
ME
SE
10- 0 10 20 30 A) [GeV/c]× r - raw,ch
T,jet (= preco,ch
T,jetp
1
10
STAR Preliminary STAR Preliminary
π0+Jet at mid-rapidity in Au+Au collisionsRecoil charged Jet spectrums for different trigger ET windows
Rjet = 0.2 Rjet = 0.5
A clear trigger dependence can been seen.STAR: NiharSahoo, QM2019
Nihar Sahoo (SDU) 29
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p+p collision scenarioγdir+jet π0+jet
• Not enough trigger statistics for the precision γdir/π0 +Jet measurement • However, within uncertainty, corrected data consistent with Pythia8• PYTHIA8 is used as p+p baseline for Au+Au collisions
• 9 < ETtrig < 11 GeV• Rjet = 0.2• Charged jets
Derek Anderson, ISMD2019
Nihar Sahoo (SDU) 30
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