correlations with a high p t trigger over a broad range n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Correlations with a high-p T trigger over a broad η range PowerPoint Presentation
Download Presentation
Correlations with a high-p T trigger over a broad η range

Loading in 2 Seconds...

play fullscreen
1 / 24

Correlations with a high-p T trigger over a broad η range - PowerPoint PPT Presentation


  • 82 Views
  • Uploaded on

Correlations with a high-p T trigger over a broad η range. G á bor Veres Eötvös Loránd University, Budapest for the collaboration. based on a PHOBOS talk at QM’2008 by E. Wenger -. Támogatók : OTKA F 49823, NKTH-OTKA H 07 -C 74248

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Correlations with a high-p T trigger over a broad η range' - joey


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
correlations with a high p t trigger over a broad range
Correlations with a high-pT triggerover a broad η range
  • Gábor Veres
  • Eötvös Loránd University, Budapest
  • for the collaboration
  • based on a PHOBOS talk at QM’2008 by E. Wenger-

Támogatók: OTKA F 49823, NKTH-OTKA H07-C 74248

Magyary Zoltán Felsőoktatási Közalapítvány

the collaboration
The Collaboration

Burak Alver, Birger Back,Mark Baker, Maarten Ballintijn, Donald Barton,

Russell Betts, Richard Bindel, Wit Busza (Spokesperson), Vasundhara Chetluru, Edmundo García, Tomasz Gburek, Joshua Hamblen, Conor Henderson,

David Hofman, Richard Hollis, Roman Hołyński, Burt Holzman, Aneta Iordanova,

Chia Ming Kuo, Wei Li, Willis Lin, Constantin Loizides, Steven Manly, Alice Mignerey,

Gerrit van Nieuwenhuizen, Rachid Nouicer, Andrzej Olszewski, Robert Pak,

Corey Reed, Christof Roland, Gunther Roland, Joe Sagerer, Peter Steinberg,

George Stephans, Andrei Sukhanov, Marguerite Belt Tonjes, Adam Trzupek,

Sergei Vaurynovich, Robin Verdier, Gábor Veres, Peter Walters, Edward Wenger,

Frank Wolfs, Barbara Wosiek, Krzysztof Woźniak, Bolek Wysłouch

ARGONNE NATIONAL LABORATORY BROOKHAVEN NATIONAL LABORATORY

INSTITUTE OF NUCLEAR PHYSICS PAN, KRAKOW MASSACHUSETTS INSTITUTE OF TECHNOLOGY

NATIONAL CENTRAL UNIVERSITY, TAIWAN UNIVERSITY OF ILLINOIS AT CHICAGO

UNIVERSITY OF MARYLAND UNIVERSITY OF ROCHESTER

motivation

high-pT azimuthal correlations

STAR, PRL 91, 072304 (2003)

Motivation

One of the most fundamental discoveries at RHIC is that

partons strongly interact as they traverse the produced medium

  • single-particle spectra, RAA

PHOBOS, PRL 96, 212301 (2006)

associated high p t particles

Beep! Beep!

Associated high-pT particles

Where does the energy go?

Look at associated particles at lower momentum!

associated low p t particles

Enhanced correlation (“ridge”) at =0 and large 

  • broadening in  of away-side compared to p+p

Au+Au

STAR, arXiv:nucl-ex/0701074v2

d+Au

  • There is no “ridge”without medium:



PHENIX, arXiv:0705.3060v2

Associated low-pT particles

Existing triggered correlation measurements show

novel features in heavy-ion collisions

interpretations of the ridge
Interpretations of the “ridge”

Different proposed mechanisms qualitatively describe “ridge” at |Δη|<2:

  • Coupling of induced radiation to longitudinal flow
  • Recombination of shower + thermal partons
  • Anisotropic plasma
  • Turbulent color fields
  • Bremsstrahlung + transverse flow + jet-quenching
  • Splashback from away-side shock
  • Momentum kick imparted on medium partons

Armesto et al., Phys. Rev. Letters 93, 242301

Hwa, Nucl. Phys. A783, 57 (2007)

Romatschke, Phys. Rev. C 75, 014901

Majumder, Muller, Bass, Phys. Rev. Lett. 99, 042301 (2007)

Shuryak, Phys. Rev. C76, 047901 (2007)

Pantuev, arXiv:0710.1882v1 [hep-ph]

Wong, Phys. Rev. C 76, 054908 (2007)

the advantage of
The advantage of
  • Can use the uniquely broad acceptance of the PHOBOS multiplicity detectors to measure the ridge at largeΔ…
  • …to constrain the possible explanations for correlated particle production far in  from a high-pT trigger

?

?

experimental layout
Experimental layout

Associated hits

Full  coverage

Broad η coverage (-3 < η < 3)

Single layer of silicon

No pTinformation

pT> 35 MeV/c (at η=0)

High pTtrigger track

pT > 2.5 GeV/c

0 < ηtrig < 1.5

Small acceptance in 

Octagonholes are filled using hits from the first layers of theSpectrometer andVertexdetectors

TRIGGER

PARTICLE

constructing the correlation

= { - a [ ] }

V = <v2trig><v2assoc>

“Background”:

Acceptance-corrected mixed-event pairs (per trigger particle)

Signal/Background.

Detector acceptance cancels in the ratio

Modulation from elliptic flow

How can these three terms be measured?

Constructing the correlation

= - · a [ ]

1 normalized background
1. Normalized background

is the mixed-event pair distribution corrected for the pair acceptance, per trigger particle

In other words, it is the single-particle distribution (dN/dη) convoluted with the ηtrigger distribution

Au+Au200 GeV

η

ηtrigger

Δη

PHOBOS: PRL 91, 052303 (2003)

2 signal and mixed events
2. Signal and mixed events

15-20% central

3mm < vz < 4mm

Au+Au



averaged over the vertex position:

-15cm < vz < 10cm



3 estimating the flow contribution
3. Estimating the flow contribution

Parametrize the published PHOBOS v2 results in a factorized form: v2(Npart,pT,η) = A(Npart) B(pT) C(η)

A(Npart)

B(pT)

C(η)

PHOBOS: PRC 72,051901

PHOBOS: PRC 72,051901

  • Correct v2(Npart,<pTtrig>,ηtrig) for occupancy and v2(Npart,<pTassoc>,ηassoc)for secondaries
  • V2 is available at any Npart, pT, η

V = <v2trig><v2assoc>

subtracting elliptic flow
Subtracting elliptic flow

-a[ ]

PHOBOS preliminary

10-30% central

-0.5 < Δη < 0.0

a



The scale factor, a, is calculated such that the yield after subtraction is zero at its minimum (ZYAM)

Ajitanand et al. PRC 72, 011902(R) (2005)

systematic uncertainties
Systematic uncertainties

PHOBOS preliminary

10-30% central

-0.5 < Δη < 0.0

  • Dominant systematic error:
  • the uncertainty of v2trig v2assoc
    • ~14% error on v2trig v2assoc (η=0)
    • ~20% error on v2trig v2assoc (η=3)
    • In the most central collisions - where flow is small compared to the correlation - the relative error on v2trig v2assoc can exceed 50%.



PHOBOS preliminary

0-6% central

-0.5 < Δη < 0.0



pythia p p reference
PYTHIA: p+p reference
  • p+p data from PHOBOS is limited by statistics
  • We will compare our Au+Au results to PYTHIA, which reproduces STAR p+p data reasonably well:

|η| < 1

4 < pTtrig < 6 GeV/c

0.15 < pTassoc < 4 GeV/c

STAR, PRL95,152301 (2005)

results
Results

pTtrig > 2.5 GeV/c

pTassoc20 MeV/c

p+p PYTHIA v6.325

Au+Au 0-30% central

PHOBOS preliminary

a closer look
A closer look…

Correlated yield, short-range (|Δη| < 1):

Au+Au

Significant broadening on the away side

the ridge extends to high
The ridge extends to high 

Correlated yield, long-range (-4 < Δη < -2):

Au+Au

Ridge

Broadening, away side

short range centrality dependence
Short-range; centrality dependence

CENTRAL

|Δη| < 1

Au+Au

The broadeningis growing withcentrality

PERIPHERAL

long range centrality dependence
Long-range; centrality dependence

CENTRAL

-4 < Δη < -2

Au+Au

PERIPHERAL

Both featuresare growing with

centrality

integrated yield of the ridge

|| < 1 rad

Integrated yield of the “ridge”

-4 <  < -2

Integrate ridge over || < 1

the extent of the ridge in
The extent of the ridge in 

Correlated yield on near-side (|| < 1):

Au+Au

Ridge persiststo high ||!

comparison to predictions

Trigger

q

Momentum kick

σy = rapidity width of partons

Comparison to predictions

||<1

C.Y. Wong, private communication

C.Y. Wong, PRC 76, 054908 (2007)

conclusions

Broadening of the away-side correlation in (relative to p+p) persists over the complete range covered

  • The near-side correlation at   0 and large  (“ridge”) extends to  4
  • The yield of the “ridge” at large  gradually disappears going from central to peripheral Au+Au collisions
Conclusions

Correlations with a high-pT trigger were measured

in an extended pseudorapidity region.

Looking forward to LHC, where similar studies willbe feasible with a comparableregion.