Jet medium interactions in heavy ion collisions
This presentation is the property of its rightful owner.
Sponsored Links
1 / 22

Jet-medium interactions in heavy ion collisions PowerPoint PPT Presentation


  • 103 Views
  • Uploaded on
  • Presentation posted in: General

Jet-medium interactions in heavy ion collisions. Olga Evdokimov for the STAR Collaboration. Outline. STAR detector Detector components Specifics of Heavy Ion jet studies Jet quenching in heavy ion collisions: Angular correlations for jet studies Full jet reconstruction for HI collisions

Download Presentation

Jet-medium interactions in heavy ion collisions

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Jet medium interactions in heavy ion collisions

Jet-medium interactions in heavy ion collisions

Olga Evdokimov

for the STAR Collaboration


Outline

Outline

  • STAR detector

    • Detector components

    • Specifics of Heavy Ion jet studies

  • Jet quenching in heavy ion collisions:

    • Angular correlations for jet studies

    • Full jet reconstruction for HI collisions

  • Summary & Outlook

Olga Evdokimov

University of Illinois at Chicago


The star detector

The STAR detector

ToF

EMC

FPD

TPC

PMD

FMS

  • Uniform 2p azimuthal acceptance

  • Extended rapidity coverage

  • Excellent identification capabilities

Olga Evdokimov

University of Illinois at Chicago


Hi collisions the environment

HI collisions: the environment

Data:

High multiplicities

→ background levels

→ new techniques for jet studies

Physics:

Strongly-interacting partonic medium

(ask me how we know)

→ modified jets

Olga Evdokimov

University of Illinois at Chicago


Jet medium interactions

Hard parton scattering

leading

particle

hadrons

q

leading

particle

hadrons

q

q

hadrons

q

leading particle

hadrons

leading particle

Jet-medium interactions

  • Why?

  • How to spot?

    • Correlations and hadron distributions

      High pT spectra and RAA

      Triggered and inclusive correlations: pp vs. AA

    • Reconstructed jets

      Cross-sections and RAAJet

      Shape modifications (broadening)

      Jet-jet, hadron-jet correlations

Olga Evdokimov

University of Illinois at Chicago


Jet medium interactions in heavy ion collisions

Jet quenching: the discovery

PRL 91 (2003)

072303

  • High pT hadron suppression:

    • Final state effect in Au+Au collisions

    • Observation extends to all accessible pT range

4<pTtrig<6 GeV/c 2<pTassoc<pTtrig

  • Signature two-particle correlation result:

    • “Disappearance” of the away-side jet in central Au+Au collisions

    • (for associated hadrons pTassoc>2)

    • Effect vanishes in peripheral/d+Au collisions

PRL 91 (2003)

072304

Olga Evdokimov

University of Illinois at Chicago


Angular pair correlations

Angular pair-correlations

proton-proton

84-93%

74-84%

64-74%

55-64%

46-55%

φΔ

ηΔ

STAR Preliminary

18-28%

9-18%

28-38%

5-9%

0-5%

φΔ

ηΔ

Evolution of several correlation structures is observed

Shown are 200 GeV minimum bias Au+Au data

Similar analysis performed for 200 GeV Cu+Cu, and 62 GeV Au+Au and Cu+Cu data

Olga Evdokimov

University of Illinois at Chicago


Transverse momentum scan

Transverse momentum scan

Zoom in on jets: follow pT evolution

pT>0.3 GeV/c

pT>0.5 GeV/c

pT>1.1 GeV/c

pT>1.5 GeV/c

STAR Preliminary

diminishing e+e-

Unlike-charge-sign pairs from 10% most central 200 GeV Cu+Cu data

Fit same-side with asymmetric 2D Gaussian + symmetric 2D Gaussian

f width

amplitude

h width

amplitude

width

0 0.6 1.2

pT(GeV/c)

0 0.6 1.2

pT(GeV/c)

0 0.6 1.2

pT(GeV/c)

0 0.6 1.2

pT(GeV/c)

0 0.6 1.2

pT(GeV/c)

Olga Evdokimov

University of Illinois at Chicago


Triggered correlations

“Triggered” correlations

3 < pT,trigger< 4 GeV/c

P RC 80 (2009) 064912

pt,assoc. > 2 GeV/c

  • Near-side correlation structure:

    • Central Au+Au: cone-like + ridge-like

    • Ridge correlated with jet direction

    • Approximately independent of Dhand trigger pT

Olga Evdokimov

University of Illinois at Chicago


What is same side ridge

200 GeV

62 GeV

What is same-side ridge?

3.0 < pTtrigger 6.0 GeV/c;

1.5 < pTassoc < pTtrigger

  • Medium modified jet ?

    • Correlated with jet and persists to highest trigger pT

    • Jet yield decreases with beam energy, consistent with pQCD

    • Ridge/jet ratio consistent between 200 and 62 GeV data

Olga Evdokimov

University of Illinois at Chicago


What is same side ridge1

90º

What is same-side ridge?

  • Jet modified medium?

    • Ridge pt-spectra are ‘bulk-like’ and approx. independent of pTtrig

    • Ridge decreases from in-plane to out-of-plane

Olga Evdokimov

University of Illinois at Chicago


Di jets through correlations

assoc.

trig2

trig1

Di-jets through correlations

Trig1 is highest pT particle in event with 5-10 GeV/c

Trig2 (pT > 4 GeV/c) is back-to-back with Trig1

Associated particles pT > 1.5 GeV/c

200 GeV Au+Au and d+Au

same-side

away-side

associated particle

pT spectra

STAR Preliminary

  • No evidence of medium modificationsDi-jets observed - all tangential?

Olga Evdokimov

University of Illinois at Chicago


Jet energy calibration

Jet-energy calibration

Direct g - hadron correlations

arXiv:0912.1871

STAR Preliminary

  • Similar medium effect on the away-side of 0 and dir

  •  is this due to tangential emission?

  • rich sample has lower near-side

  • yields compared to those of the

  • 0 different bias

Olga Evdokimov

University of Illinois at Chicago


Full jet reconstruction

Full jet reconstruction

  • Why?

    • High pT hadrons bias towards non-interacting jets

    • Full jet reconstruction reduces the bias

    • Hadronization

  • Why just now?

    • Very complex due to underlying event

    • Algorithmic biases

    • Data driven correction schemes

Pythia

smeared

Unfolding

unfolded

Olga Evdokimov

University of Illinois at Chicago


Inclusive jet measurements

Inclusive jet measurements

Central Au+Au: background correction leads to a factor of 2 uncertainty in cross-section

Olga Evdokimov

University of Illinois at Chicago


Inclusive jet ratios

Inclusive jet ratios

R=0.4

RAAJet

Yields: R=0.2/R=0.4

RAA of pions ~ 0.2

RAAJet> RAAp: recover larger fraction of cross-section, but not all

Significant ratio suppression wrt. pp

→ medium induced ET broadening

Olga Evdokimov

University of Illinois at Chicago


Jet hadron correlations

Jet-hadron correlations

1.0<pTassoc<2.5 GeV/c

STAR Preliminary

  • 0-20% Au+Au

  • pp

STAR Preliminary

flat BG subtraction

STAR Preliminary

  • Au+Au vs. pp:

  • Softer momentum distribution for recoil hadrons

  • Significant away-side broadening

Olga Evdokimov

University of Illinois at Chicago


Jet medium interactions in heavy ion collisions

Summary &Outlook:

  • Jet quenching discovered at RHIC has been extensively studied for years:

    • Modification of angular shapes, production rates, transverse momentum and energy distributions

  • Evolution of jet studies in HI:

    • Inclusive hadron measurements → di-hadron correlations → multi-particle correlations → full jets

  • Outlook:

    • Towards “theory-ready” (partonic) energy loss measurements

    • Disentangling experimental biases

Olga Evdokimov

University of Illinois at Chicago


Back up

Back-Up

Olga Evdokimov

University of Illinois at Chicago


Low p t ridge

peak η width

peak amplitude

STAR Preliminary

STAR Preliminary

200 GeV

62 GeV

83-94%

55-65%

0-5%

46-55%

STAR Preliminary

STAR Preliminary

STAR Preliminary

STAR Preliminary

Transverse particle density

ηΔ width

Low pT ridge

Same-side evolution

  • Sharp transition in both amplitude and width at ρ ~ 2.5

  • Similar ρ-trends at 62 and 200GeV

Olga Evdokimov

University of Illinois at Chicago


Jet medium interactions in heavy ion collisions

90º

in-plane fS=0

out-of-plane fS=90o

Path-length effects

3<pTtrig<4GeV/c

  • Same-side yield

    • Jet: d+Au ~ Au+Au

  • Ridge decreases from in-plane to out-of-plane

    • Elliptic flow effects?

STAR Preliminary

Olga Evdokimov

University of Illinois at Chicago


Jet reconstruction algorithms

KT jet

Cone jet

Jet reconstruction algorithms

  • Cone algorithms

    • Mid Point Cone (merging + splitting)

    • SISCone (seedless, infra-red safe)

  • Sequential recombination algorithms

    • kT

    • anti-kT

    • Cambridge/ Aachen

Jet

by P. Jacobs

Fragmentation

Hard scatter

Olga Evdokimov

University of Illinois at Chicago


  • Login