NiharRanjan Sahoo...1 Semi-inclusive γ+jet and h+jetin STAR experimentNiharRanjan Sahoo Shandong...

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

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 )

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

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

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

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

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

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

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

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

IAA(x) =Y Au+Au(x)

Y p+p(x)


STAR: PLB 760 (2016) 689


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


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.


Semi-inclusive γ+jet and π0+jetusing jet reconstruction

Ongoing work in the STAR experiment:

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


One trigger event

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.

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


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



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.

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


+jet0p +jetdirg

5 10 15 20 251−10

1

PYTH


= 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;

• Same level of suppression for γdir+jet and π0+jetNihar Sahoo (SDU) 18

Rjet = 0.2

STAR: Nihar Sahoo, HP2018,QM2019

Nuclear Modification factor: Au+Au 200 GeV

2 4 6 8 10 12 14 16 18 20

1-10

1

PYTH


= 0.2jet RTanti-kSTAR Preliminary

< 15 GeV/cconst.T


2 4 6 8 10 12 14 16 18 20 [GeV/c]ch

T,jetp

1-10

1

PYTH

IAAAI

< 15 GeV/cconst.T


+jet0p +jetdirg

5 10 15 20 251−10

1

PYTH


= 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


Rjet = 0.2 Rjet = 0.5

STAR: Nihar Sahoo, HP2018,QM2019

In-medium recoil jet suppression at RHIC and LHC


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.]

Dijet Δφ angular correlation:A large angle deflection in HICs

21Nihar Sahoo (SDU)

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

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


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


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!

Backup



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

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



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


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


NiharRanjan Sahoo...1 Semi-inclusive γ+jet and h+jetin STAR experimentNiharRanjan Sahoo Shandong...

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