Two “particle” correlations at...

41
Two “particle” correlations at RHIC JET Workshop - LBNL Helen Caines - Yale University June 18 th 2010 Outline: hadron-hadron gamma-hadron jet-hadron Friday, June 18, 2010

Transcript of Two “particle” correlations at...

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Two “particle” correlations at RHIC

JET Workshop - LBNLHelen Caines - Yale University

June 18th 2010

Outline:hadron-hadrongamma-hadronjet-hadron

Friday, June 18, 2010

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JET Workshop - June 18th 2010Helen Caines

Di-hadron correlations in 1976

2

P. Darriulat et al. NPB107 (1976) 429 ISR √s=53 GeVEvent-by-event analysis of rapidity correlation

Trigger: π0 pT>2 GeV/c

Assoc: Charged particle |180-Φ|<350

px>1.5 GeV/c(px component along π0 axis)

“Structure of Final States with a high pT π0 in p-p collisions”

“..these properties are surprisingly reminiscent of the co-planar two-jet picture first given by Berman, Bjorken & Kogut in the

frame of quark parton models”

Friday, June 18, 2010

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JET Workshop - June 18th 2010Helen Caines

Di-hadron correlations in 1982

3

pT,Trig > 4 GeV/ca) pT,Assoc > 0 GeV/cb) pT,Assoc > 1 GeV/cc) pT,Assoc > 2 GeV/c

(note the lack of axis labels)

UA1 PL 118B (1982) 173

“1st observation of correlations between high pT charged particle at the SppS”-

“As at the ISR, hard scattering and fragmentation of partons offers a possible explanation”

Friday, June 18, 2010

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JET Workshop - June 18th 2010Helen Caines

Di-hadron correlations in 2003

4

p-p correlations form 3 distinct regions:near-side, away-side, transverse region (underlying event)

Same is true in d-Au

Scattered parton approximated by high pT particle

steeply falling jet spectrum at RHIC behind this assumption

PRL 90, 082302

Di-hadron correlations still used as proxy for jet reconstruction

Friday, June 18, 2010

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JET Workshop - June 18th 2010Helen Caines

Di-hadron in A-A - new features

5

After background subtraction:

PRC 78 (2008) 014901

PHENIX

“Mach Cones” “Ridges”

Medium response to hard scattered partons?Results of energy lost by hard scattered partons?

Something else?

PRC 80 (2009) 064912

STAR

Friday, June 18, 2010

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Chen HP08

JET Workshop - June 18th 2010Helen Caines

“Ridge” and “Shoulder” properties

6

STAR Preliminary

PHENIX

M. McCumber QM2008 pTassoc (GeV/c)

McCumber QM08

Similar in spectral shape and flavor composition to bulk

Friday, June 18, 2010

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Chen HP08

JET Workshop - June 18th 2010Helen Caines

“Ridge” and “Shoulder” properties

6

STAR Preliminary

PHENIX

M. McCumber QM2008 pTassoc (GeV/c)

McCumber QM08

Similar in spectral shape and flavor composition to bulkRidge ∝ Npart independent of system

C.NattrassQM08

Friday, June 18, 2010

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Chen HP08

JET Workshop - June 18th 2010Helen Caines

“Ridge” and “Shoulder” properties

6

STAR Preliminary

PHENIX

M. McCumber QM2008 pTassoc (GeV/c)

McCumber QM08

Similar in spectral shape and flavor composition to bulk

Ridge/Jet yield same for √s=62 and 200 GeV

C.NattrassQM08

Ridge ∝ Npart independent of system

C.NattrassQM08

Friday, June 18, 2010

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JET Workshop - June 18th 2010Helen Caines

Two component model - ZYAM

7

Analyses assume correlations can be split into two sources the “jet” and the “background”

(rad)!"-1 0 1 2 3 4

!"

/dA

B d

NA

1/N

0.8

1

1.2

1.4

1.6

1.8

2

2.2

Narrow peaks: well-separated

bkg

N.S. + bkg

A.S. + bkg

N.S. + A.S. + bkg

Narrow peaks: well-separated

Simulation A. Adare

(rad)!"-1 0 1 2 3 4

!"

/dA

B d

NA

1/N

0.8

1

1.2

1.4

1.6

1.8

2

2.2

Broad peaks overlap: ZYAM bkg. too high

bkgN.S. + bkg

A.S. + bkg

N.S. + A.S. + bkg 10%)±

2ZYAM bkg (v

Broad peaks overlap: ZYAM bkg. too high

Simulation A. Adare

ZYAM incorrect for broad jet peaksBackground subtraction is non-trivial

PHENIX now use an absolute background normalization A. Sickles et al. PRC 81 014908 (2010)

Friday, June 18, 2010

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Bo(1 + 2vAB2 cos2!!)

JET Workshop - June 18th 2010Helen Caines

Two component model - Flow contribution

8

Analyses assume correlations can be split into two sources the “jet” and the “background”

Background approximated via:

DIHADRON AZIMUTHAL CORRELATIONS IN Au+Au . . . PHYSICAL REVIEW C 78, 014901 (2008)

elliptic flow. The pair distribution can be expressed as

N same(!") = #!1 + 2va

2vb2 cos 2!"

"Nmixed(!") + Jet(!")

(10)

Where the Jet(!") represents all pairs from (di)jets. Theintegral of N same can be written as

#d!"N same(!") = Nevts!nanb" +

#d!"Jet(!"). (11)

Comparing to Eq. (9), we obtain

# = !nanb"!na"!nb"

. (12)

Thus, # is simply the ratio of the trigger-partner combinatoricrate in the same event to that in mixed events, which canbe bigger than unity because of centrality smearing (seediscussion in Sec. III E). An alternative approach used to fix #is to assume that the jet function has zero yield at its minimum!"min (ZYAM) [18,52].

Finally, the ratio of jet-induced pairs to combinatoric pairsfrom mixed events, the jet-induced hadron-pair ratio (JPR) isgiven by

JPR(!") # Jet(!")Nmixed(!")

= N same(!")Nmixed (!")

$ #!1 + 2va

2vb2 cos 2!"

". (13)

A representative correlation function is given in Fig. 2 for 0–5% Au+Au collisions and for triggers and partners in 2–3 and1–2 GeV/c, respectively. It shows a peak around !" % 0 and abroad structure around !" % $ . The dashed line indicates theestimated elliptic flow modulated background via the ZYAMmethod. The area between the data points and the dashed linereflects the jet-induced pair ratio. It is only a few percentrelative to the background level.

We define %a, %b as the single particle efficiency withinthe PHENIX pseudorapidity acceptance (|&| < 0.35). The truenumbers of triggers and partners are given by

$na

0

%=

$na%&%a;

$nb

0

%=

$nb

%&%b. (14)

(rad)!"0 2 4

)!"C

(

0.99

1

1.01

1.02

1.030-5%

<3 GeV/caT

<2<pbT

1<p

FIG. 2. (Color online) Correlation function for 2 < paT < 3, 1 <

pbT < 2 GeV/c in 0–5% Au+Au collisions. The dashed line represents

the estimated elliptic flow modulated combinatoric background usingzero yield at minimum (ZYAM) method (see Sec. III E).

For uncorrelated sources, the triggers and partners are uniformin azimuth. Thus the true combinatoric pair distribution formixed events is flat with !" with a density of !na

0"!nb0"/(2$ ).

The yield of jet-induced pairs per event (JPY) is given as theproduct of the combinatoric pair rate and the hadron-pair ratio,

JPY(!") =$na

0

%$nb

0

%

2$JPR(!") = !na"!nb"

2$%a%bJPR(!")

='

d!"Nmixed(!")2$Nevts%a%b

(N same(!")Nmixed(!")

$ #!1 + 2va

2vb2 cos 2!"

"). (15)

Thus far, we have made no distinction between triggerand partner hadrons. As discussed earlier in Sec. II, thecorrelation function, hadron-pair ratio, and hadron-pair yieldare symmetric between the trigger and partner pT , i.e.,

C!pa

T , pbT

"= C

!pb

T , paT

",

JPR!pa

T , pbT

"= JPR

!pb

T , paT

", (16)

JPY!pa

T , pbT

"= JPY

!pb

T , paT

".

The associated partner yield per trigger, Yjet ind(!") is ob-tained by dividing the hadron-pair yield per event with thenumber of triggers per event,

Yjet ind(!") = JPY(!")na

0=

'd!"Nmixed(!")

2$Na%b

&(

N same(!")Nmixed(!")

$ #!1 + 2va

2vb2 cos 2!"

").

(17)

Yjet ind is often referred to as the per-trigger yield or conditionalyield. It is clearly not invariant to the exchange of trigger andpartner pT .

The analysis proceeds in the following steps. We firstmeasure the correlation function of Eq. (8). We then obtainthe efficiency for partner hadrons (%b) and the elliptic flowcoefficients for the two hadron categories (va

2 , vb2 ). We then

determine the background level (# ) via the ZYAM backgroundsubtraction method (see Sec. III E), followed by a calculationof the per-trigger yield according to Eq. (17). Subsequently,we obtain the hadron-pair yield by multiplying the per-triggeryield with the inclusive charged hadron yield [6] integrated inthe corresponding trigger pT range.

According to Eq. (6), the hadron-pair yields calculatedfrom the per-trigger yields are independent of which hadron,from the pair, is used as trigger. We used this fact to cross-checkthe efficacy of our analysis. Figure 3 compares the hadron-pairyields obtained when the trigger and partner pT is exchangedin p + p collisions (in pa

T ' pbT ). The open symbols indicate

the results for low-pT trigger hadrons in association withhigh-pT partners. The filled symbols show the converse. Asimilar comparison for 0–20% Au+Au collisions is shownin Fig. 4. Overall good agreement is indicated by thesedistributions. It is important to emphasize here that there isno a priori reason for these distributions to be identical, sincethe cuts on trigger and partner hadrons are a little different(cf. Sec. III B) and therefore could lead to somewhat different

014901-7

PRC 78 014901 (2008)

Higher moments of the expansion ignored

Friday, June 18, 2010

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Bo(1 + 2vAB2 cos2!!)

JET Workshop - June 18th 2010Helen Caines

Two component model - Flow contribution

8

Analyses assume correlations can be split into two sources the “jet” and the “background”

Background approximated via:

DIHADRON AZIMUTHAL CORRELATIONS IN Au+Au . . . PHYSICAL REVIEW C 78, 014901 (2008)

elliptic flow. The pair distribution can be expressed as

N same(!") = #!1 + 2va

2vb2 cos 2!"

"Nmixed(!") + Jet(!")

(10)

Where the Jet(!") represents all pairs from (di)jets. Theintegral of N same can be written as

#d!"N same(!") = Nevts!nanb" +

#d!"Jet(!"). (11)

Comparing to Eq. (9), we obtain

# = !nanb"!na"!nb"

. (12)

Thus, # is simply the ratio of the trigger-partner combinatoricrate in the same event to that in mixed events, which canbe bigger than unity because of centrality smearing (seediscussion in Sec. III E). An alternative approach used to fix #is to assume that the jet function has zero yield at its minimum!"min (ZYAM) [18,52].

Finally, the ratio of jet-induced pairs to combinatoric pairsfrom mixed events, the jet-induced hadron-pair ratio (JPR) isgiven by

JPR(!") # Jet(!")Nmixed(!")

= N same(!")Nmixed (!")

$ #!1 + 2va

2vb2 cos 2!"

". (13)

A representative correlation function is given in Fig. 2 for 0–5% Au+Au collisions and for triggers and partners in 2–3 and1–2 GeV/c, respectively. It shows a peak around !" % 0 and abroad structure around !" % $ . The dashed line indicates theestimated elliptic flow modulated background via the ZYAMmethod. The area between the data points and the dashed linereflects the jet-induced pair ratio. It is only a few percentrelative to the background level.

We define %a, %b as the single particle efficiency withinthe PHENIX pseudorapidity acceptance (|&| < 0.35). The truenumbers of triggers and partners are given by

$na

0

%=

$na%&%a;

$nb

0

%=

$nb

%&%b. (14)

(rad)!"0 2 4

)!"C

(

0.99

1

1.01

1.02

1.030-5%

<3 GeV/caT

<2<pbT

1<p

FIG. 2. (Color online) Correlation function for 2 < paT < 3, 1 <

pbT < 2 GeV/c in 0–5% Au+Au collisions. The dashed line represents

the estimated elliptic flow modulated combinatoric background usingzero yield at minimum (ZYAM) method (see Sec. III E).

For uncorrelated sources, the triggers and partners are uniformin azimuth. Thus the true combinatoric pair distribution formixed events is flat with !" with a density of !na

0"!nb0"/(2$ ).

The yield of jet-induced pairs per event (JPY) is given as theproduct of the combinatoric pair rate and the hadron-pair ratio,

JPY(!") =$na

0

%$nb

0

%

2$JPR(!") = !na"!nb"

2$%a%bJPR(!")

='

d!"Nmixed(!")2$Nevts%a%b

(N same(!")Nmixed(!")

$ #!1 + 2va

2vb2 cos 2!"

"). (15)

Thus far, we have made no distinction between triggerand partner hadrons. As discussed earlier in Sec. II, thecorrelation function, hadron-pair ratio, and hadron-pair yieldare symmetric between the trigger and partner pT , i.e.,

C!pa

T , pbT

"= C

!pb

T , paT

",

JPR!pa

T , pbT

"= JPR

!pb

T , paT

", (16)

JPY!pa

T , pbT

"= JPY

!pb

T , paT

".

The associated partner yield per trigger, Yjet ind(!") is ob-tained by dividing the hadron-pair yield per event with thenumber of triggers per event,

Yjet ind(!") = JPY(!")na

0=

'd!"Nmixed(!")

2$Na%b

&(

N same(!")Nmixed(!")

$ #!1 + 2va

2vb2 cos 2!"

").

(17)

Yjet ind is often referred to as the per-trigger yield or conditionalyield. It is clearly not invariant to the exchange of trigger andpartner pT .

The analysis proceeds in the following steps. We firstmeasure the correlation function of Eq. (8). We then obtainthe efficiency for partner hadrons (%b) and the elliptic flowcoefficients for the two hadron categories (va

2 , vb2 ). We then

determine the background level (# ) via the ZYAM backgroundsubtraction method (see Sec. III E), followed by a calculationof the per-trigger yield according to Eq. (17). Subsequently,we obtain the hadron-pair yield by multiplying the per-triggeryield with the inclusive charged hadron yield [6] integrated inthe corresponding trigger pT range.

According to Eq. (6), the hadron-pair yields calculatedfrom the per-trigger yields are independent of which hadron,from the pair, is used as trigger. We used this fact to cross-checkthe efficacy of our analysis. Figure 3 compares the hadron-pairyields obtained when the trigger and partner pT is exchangedin p + p collisions (in pa

T ' pbT ). The open symbols indicate

the results for low-pT trigger hadrons in association withhigh-pT partners. The filled symbols show the converse. Asimilar comparison for 0–20% Au+Au collisions is shownin Fig. 4. Overall good agreement is indicated by thesedistributions. It is important to emphasize here that there isno a priori reason for these distributions to be identical, sincethe cuts on trigger and partner hadrons are a little different(cf. Sec. III B) and therefore could lead to somewhat different

014901-7

PRC 78 014901 (2008)

Higher moments of the expansion ignored

Recent work indicates that v3 may be important!

B. Alver & G. Roland PRC 81 (2010) 054905

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B. Alver & G. Roland PRC 81 (2010) 054905

dN

d!=

N

2"(1 +

!2vncos(n(!!!n)))

v2 = !cos(2(! " !2))#, v3 = !cos(3(! " !3))#

JET Workshop - June 18th 2010Helen Caines

“Triangular” flow

9

B. Alver & G. Roland PRC 81 (2010) 054905 Triangular anisotropic initial conditions

→ v3 of particles in final state

What’s So Odd About the Ridge and Cone?

15

low pT ridge yield

STAR Preliminary

Mv32

Y. Pandit and P. Sorensen:

Fourier Transform of data from STAR,

Phys. Rev. Lett. 95 (2005) 152301

Large possible <v32> component in intermediate pT data

Centrality dependence is similar to the low pT ridge

P. Sorensen and Y. Pandit SQM2009

Npart

Fourier transform STAR data PRL95 (2005) 152301

v3sizable even in central events

Friday, June 18, 2010

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JET Workshop - June 18th 2010Helen Caines

v3 effect on measured correlations

10

After subtracting 1st 3 fourier components: residuals in large Δη almost flat i.e.

the non-triggered ridge appears to have disappeared

B. Alver & G. Roland PRC 81 (2010) 054905

arXiv:0806.0513

Since v3 peaks at 1200 could also explain the “mach cone”Could also explain why ridge and shoulder are so “bulk like”

“simple” explanation - Needs further verification

Friday, June 18, 2010

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JET Workshop - June 18th 2010Helen Caines

High pT di-hadron correlations

11

7

!"

dN

/dtr

ig1/N

0

0.5

1

< 3.0 GeV/ctrig

T2.5 < p

< 1.0 GeV/cassoc

T0.5 < p

0

0.2

0.4

< 1.5 GeV/cassoc

T1.0 < p

0

0.2

0.4

< 2.5 GeV/cassoc

T1.5 < p

-1 0 1 2 3 4 5

0

0.1

0.2

< 4.0 GeV/cassoc

T2.5 < p

0

0.5

1

< 4.0 GeV/ctrig

T3.0 < p

0

0.2

0.4

Au+Au 0-12%| < 0.7#"Au+Au |

d+Au

0

0.2

0.4

-1 0 1 2 3 4 5

0

0.1

0.2

0

0.5

1

< 6.0 GeV/ctrig

T4.0 < p

0

0.2

0.4

0

0.2

0.4

-1 0 1 2 3 4 5

0

0.1

0.2

0

0.5

1

< 10.0 GeV/ctrig

T6.0 < p

0

0.2

0.4

0

0.2

0.4

!"-1 0 1 2 3 4 5

0

0.1

0.2

FIG. 3: Background-subtracted azimuthal angle di!erence distributions for di!erent ptrigT (columns) and passocT (rows) in 0-12%central Au+Au collisions (solid circles) and d+Au reference results (open circles). The rapidity range is |!| < 1 and as a resultthe rapidity-di!erence |"!| < 2. Open red squares show results for a restricted acceptance of |"!| < 0.7, using tracks with|!| < 1

. The solid and dashed histograms show the upper and lower range of the systematic uncertainty due to the v2 modulation ofthe subtracted background.

smaller than in d+Au. For 6 < ptrigT < 10 GeV/c (right-most column in Fig. 3), a narrow peak appears at largepassocT in Au+Au, similar to what is seen in d+Au colli-sions and at higher pT in Au+Au collisions [7].

Although the shape of the away-side distributionchanges with ptrigT and passocT , there seems to be no grad-ual broadening as a function of pT : the rising flanks of

the away-side distribution are at similar !! in the entirerange 0.5 < passocT < 2.5 GeV/c and 2.5 < ptrigT < 6. Infact, it could be argued that the away-side distributionis as broad as possible; there is no !! region withoutcorrelation signal.

The broad away-side correlation structure in Au+Aucollisions is a truly remarkable observation. Although

At high pT trigger and assoc. particles:

BG small errors in ZYAM, v2, v3,... become negligible

STARarXiV:1004.2377

For higher pT triggers (stronger jet bias)away side “mach cone” no longer visible

Modification/redistribution of jet energy apparent

Friday, June 18, 2010

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JET Workshop - June 18th 2010Helen Caines

π0-h correlations

12

PHENIX arXiv:1002.1077v2, Accepted by PRL

0

0.1

0.2

0.3

0

0.1

0.2

0.3 0.5-1 GeV/c!4-5

0

0.2

0.4

0

0.2

0.4 1-2 GeV/c!5-7

0 2 4

0

0.2

0.4

0.6

0 2 4

0

0.2

0.4

0.6 1-2 GeV/c!7-9

2-3 GeV/c!4-5 (x 3.0)

0-20% Au+Aup+p

3-5 GeV/c!5-7 (x 3.0)

2 3 4

0 2 40 2 4

3-5 GeV/c!7-9 (x 2.0)

2 3 4

"#

/d

pair

dN

0 $1/

N

(rad)"#

0

0.1

0.2

0.3

0

0.1

0.2

0.3 0.5-1 GeV/c!4-5

0

0.2

0.4

0

0.2

0.4 1-2 GeV/c!5-7

0 2 4

0

0.2

0.4

0.6

0 2 4

0

0.2

0.4

0.6 1-2 GeV/c!7-9

2-3 GeV/c!4-5 (x 3.0)

0-20% Au+Aup+p

3-5 GeV/c!5-7 (x 3.0)

2 3 4

0 2 40 2 4

3-5 GeV/c!7-9 (x 2.0)

2 3 4

"#

/d

pair

dN

0 $1/

N

(rad)"#

0

0.1

0.2

0.3

0

0.1

0.2

0.3 0.5-1 GeV/c!4-5

0

0.2

0.4

0

0.2

0.4 1-2 GeV/c!5-7

0 2 4

0

0.2

0.4

0.6

0 2 4

0

0.2

0.4

0.6 1-2 GeV/c!7-9

2-3 GeV/c!4-5 (x 3.0)

0-20% Au+Aup+p

3-5 GeV/c!5-7 (x 3.0)

2 3 4

0 2 40 2 4

3-5 GeV/c!7-9 (x 2.0)

2 3 4

"#

/d

pair

dN

0 $1/

N

(rad)"#

π0 correlations same as h± correlations

Friday, June 18, 2010

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JET Workshop - June 18th 2010Helen Caines

π0-h correlations

12

At high pT:

Away-side suppressed

PHENIX arXiv:1002.1077v2, Accepted by PRL

0

0.1

0.2

0.3

0

0.1

0.2

0.3 0.5-1 GeV/c!4-5

0

0.2

0.4

0

0.2

0.4 1-2 GeV/c!5-7

0 2 4

0

0.2

0.4

0.6

0 2 4

0

0.2

0.4

0.6 1-2 GeV/c!7-9

2-3 GeV/c!4-5 (x 3.0)

0-20% Au+Aup+p

3-5 GeV/c!5-7 (x 3.0)

2 3 4

0 2 40 2 4

3-5 GeV/c!7-9 (x 2.0)

2 3 4

"#

/d

pair

dN

0 $1/

N

(rad)"#

0

0.1

0.2

0.3

0

0.1

0.2

0.3 0.5-1 GeV/c!4-5

0

0.2

0.4

0

0.2

0.4 1-2 GeV/c!5-7

0 2 4

0

0.2

0.4

0.6

0 2 4

0

0.2

0.4

0.6 1-2 GeV/c!7-9

2-3 GeV/c!4-5 (x 3.0)

0-20% Au+Aup+p

3-5 GeV/c!5-7 (x 3.0)

2 3 4

0 2 40 2 4

3-5 GeV/c!7-9 (x 2.0)

2 3 4

"#

/d

pair

dN

0 $1/

N

(rad)"#

π0 correlations same as h± correlations

Shape the same

Friday, June 18, 2010

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JET Workshop - June 18th 2010Helen Caines

away

head

Away-side IAA vs RAA

13

At high pT, IAA > RAA

PHENIX arXiv:1002.1077v2, Accepted by PRL

-110

1

= 4-5 GeV/cT p0!

0-20% Au+Au5-7 GeV/c6% scale uncertainty

/2)!| < ! - "#away (|/6)!| < ! - "#head (|

0 1 2 3 4 5 6 7-110

1

7-9 GeV/c > 5 GeV/c

T p0

!, $ AA R% = 1.68 GeV/fm0&ZOWW,

0.6±ACHNS, K = 4.1

0 1 2 3 4 5 6 7

9-12 GeV/c

(GeV/c)T

partner p

AAII A

A=

(Nta

/Nt )

Au+

Au

(Nta

/Nt )

p+

p

Friday, June 18, 2010

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JET Workshop - June 18th 2010Helen Caines

away

head

Away-side IAA vs RAA

13

At high pT, IAA > RAA

PHENIX arXiv:1002.1077v2, Accepted by PRL

-110

1

= 4-5 GeV/cT p0!

0-20% Au+Au5-7 GeV/c6% scale uncertainty

/2)!| < ! - "#away (|/6)!| < ! - "#head (|

0 1 2 3 4 5 6 7-110

1

7-9 GeV/c > 5 GeV/c

T p0

!, $ AA R% = 1.68 GeV/fm0&ZOWW,

0.6±ACHNS, K = 4.1

0 1 2 3 4 5 6 7

9-12 GeV/c

(GeV/c)T

partner p

AAII A

A=

(Nta

/Nt )

Au+

Au

(Nta

/Nt )

p+

p

< 5 GeV/cAT4 < p

partN

< 7 GeV/cBT3 < p

Inclusive

(GeV

/c)’>

T

Head

Reg

ion

<p

0.5

1

1.5

3002001000 400

PHENIX PRC 78 (2008) 014901

Away-side spectrum harder than bulk Same ΔE, IAA > RAA

Friday, June 18, 2010

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JET Workshop - June 18th 2010Helen Caines

Theoretical Comparison

14

-110

1

= 4-5 GeV/cT p0!

0-20% Au+Au5-7 GeV/c6% scale uncertainty

/2)!| < ! - "#away (|/6)!| < ! - "#head (|

0 1 2 3 4 5 6 7-110

1

7-9 GeV/c > 5 GeV/c

T p0

!, $ AA R% = 1.68 GeV/fm0&ZOWW,

0.6±ACHNS, K = 4.1

0 1 2 3 4 5 6 7

9-12 GeV/c

(GeV/c)T

partner p

AAI

ZOWW

Reasonable agreement with data

ACHNS

Consistently falls below data

ASW energy loss + full hydro evolution

Uses a simple hard sphere geometry

Is energy loss mechanism or medium geometry the crucial difference?

PHENIX arXiv:1002.1077v2, Accepted by PRL

Both model calculations fit RAA

Uses simple hard sphere geometry

Friday, June 18, 2010

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JET Workshop - June 18th 2010Helen Caines

Npart dependence

15

T*dN/dz

trig

1/N

-110

1

d-AuCu-Cu 0-10%Cu-Cu 20-40%Cu-Cu 40-60%Au-Au 0-12%p-p MFMCu-Cu 0-10% MFMCu-Cu 20-40% MFMCu-Cu 40-60% MFM

Tz0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

) T(z

AAI

0

0.5

1

1.5

Figure 5: Away-side associated particle distribution and IAA for 6 <ptrig

T <10 GeV/c. The error bars represent statistical errors and the boxesrepresent the total systematic errors. The lines represent calculations in MFMmodel.

collisions, indicated by di!erent line styles in the figure.For the lower trigger selection, 4 GeV/c < ptrig

T < 6 GeV/c, the ModifiedFragmentation Model predicts a smaller suppression than observed in the data,whereas PQM cannot explain Cu+Cu or Au+Au results in a consistent fashion.The disagreement between the models and the data suggests that the e!ectof kinematic limits (energy loss cannot be larger than the jet energy) and non-perturbative e!ects, which are not explicitly treated in the model, are significantin this pT -range. For the higher trigger pT range, 6 GeV/c < ptrig

T < 10 GeV/c,a better agreement between the data and MFM is observed. There is an obviousdi!erence between the system size dependence in the two models. While MFMobtains IAA values that are independent on the system at a certain Npart,PQM shows a clear di!erence between the two systems for similar Npart, whenusing a common scaling of the medium density (represented by line styles inthe figure). Further model studies are needed to clarify whether the di!erentscaling behavior in MFM and PQM is mainly a result of the di!erent quenchingformalisms or rather due to di!erences between the medium density models.

In Figs. 2 and 4 we have presented results for a single selection of asso-ciated hadrons, passoc

T > 3 GeV/c. A more di!erential measurement is pre-

10

MFMUses simple hard sphere geometrySeems to get trend of data correct

STAR PLB 683 (2010) 123 6<pTtrig<10 GeV/c

partN0 50 100 150 200 250 300 350

AAI

-110

1Au-Au Cu-Cu

=4qAu-Au PQM =3qCu-Cu PQM

=7qAu-Au PQM q=5.5Cu-Cu PQM

=14qAu-Au PQM =9qCu-Cu PQM

Au-Au MFM Cu-Cu MFM

(a)

partN0 50 100 150 200 250 300 350

AAI

-110

1Au-Au Cu-Cu

=4qAu-Au PQM =3qCu-Cu PQM

=7qAu-Au PQM q=5.5Cu-Cu PQM

=14qAu-Au PQM =9qCu-Cu PQM

Au-Au MFM Cu-Cu MFM

(b)

Figure 4: Npart dependence of the away-side associated-particle yield for

two trigger pT ranges: (a) 4 GeV/c < ptrigT < 6 GeV/c (b) 6 GeV/c <

ptrigT < 10 GeV/c. For both panels 3 GeV/c < passoc

T < ptrigT . The error bars

represent statistical errors and the boxes represent the point-to-point systematicerrors. The gray band represents the correlated error due to the statistical errorin the d+Au data. The lines represent calculations in PQM and MFM models.The values of q̂ are expressed in GeV2/fm.

pression factor IAA = Y awayAA /Y away

dAu , where Y awayAA(dAu) is the away-side di-hadron

correlation strength in heavy-ion and d+Au collisions, respectively. Figure 4shows the results for IAA as a function of number of participants for Cu+Cuand Au+Au collisions. The away-side yield suppression increases with Npart,as expected. The Cu+Cu results show a similar suppression (IAA) at the samenumber of participants as the Au+Au results, despite possible di!erences indensity and path length distributions.

Figure 4 also shows two model calculations implementing the same kine-matic cuts as our analysis.1 One calculation, the Parton Quenching Model(PQM) [5, 26], uses the Salgado-Wiedemann quenching weights [27] with aGlauber-overlap geometry in which the local density scales with the local den-sity of binary collisions !coll. The other model uses a next-to-leading order QCDcalculation with modified fragmentation functions from a higher-twist formal-ism [28] and a hard-sphere geometry where the density scales with the localparticipant density !part [6]. We refer to this model as the Modified Fragmen-tation Model (MFM). The MFM authors used previous data on the suppressionof high-pT away-side yields in central Au+Au collisions [4] to tune their model.The PQM authors present 3 calculations, based on 3 values of q̂ in central

1The model calculations use p+p as the reference, which is expected to be equivalent tothe d+Au measurement used in the data.

9

PQMGlauber overlap geometryMisses Cu-Cu dataNpart scaling of energy loss, frag. as in vacuum for high zT

Friday, June 18, 2010

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JET Workshop - June 18th 2010Helen Caines

Path length dependence studies

16

Studying different centralities probes differing path lengthsbut may also vary medium properties

Alternate method:Correlations vs reaction plane

Trigger 12<pT<20 GeV/c

x (fm)

y (fm

)

x (fm)

b=7.5fmb=7.5fm

In-plane Out-of-plane

Trigger Trigger

T.Renk PRC78:034904,2008

b=7.5fmb=7.5fm

In-plane Out-of-plane

Trigger Trigger

y (fm

)

Trigger 12<pT<20, Away 4<pT<6 GeV/c

Calculation indicates there is difference in production points of measured triggers for in- vs out-of-plane

If pTassoc too high production bias

is “lost”

Friday, June 18, 2010

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JET Workshop - June 18th 2010Helen Caines

Reaction plane dependence

17

AB!"

0 0.5 1 1.5 2 2.5 3

) (ar

b. u

nits

)AB!

"J(

-0.2

0

0.2

0.4

0.6

0.8

1

1.20# [4.0,7.0] GeV $

TAp

± [3.0,4.0] GeV h$ TBp

= 200 GeV - Cent 20-60%NNsAu+Au

= 0.66(3)"

]°,15° [0$| A!-%|

]°,90° [75$| A!-%|In-plane

Out-of-plane

4<pTTrig <7, 3<pTAssoc<4 GeV/c

M.McCumber RHIC/AGS Users 2010

Friday, June 18, 2010

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JET Workshop - June 18th 2010Helen Caines

Reaction plane dependence

17

AB!"

0 0.5 1 1.5 2 2.5 3

) (ar

b. u

nits

)AB!

"J(

-0.2

0

0.2

0.4

0.6

0.8

1

1.20# [4.0,7.0] GeV $

TAp

± [3.0,4.0] GeV h$ TBp

= 200 GeV - Cent 20-60%NNsAu+Au

= 0.66(3)"

]°,15° [0$| A!-%|

]°,90° [75$| A!-%|In-plane

Out-of-plane

(rad)s!0 0.2 0.4 0.6 0.8 1 1.2 1.4

Near

PTY

(arb

. uni

ts)

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

]"183 [0,# !$

0.06 (stat+sys)± = 0.94 in/PTYoutPTY

-correctedrp%

0" [4.0,7.0] GeV # TAp

± [3.0,4.0] GeV h# TBp

= 200 GeV - Cent 20-60%NNsAu+Au

in-plane out-plane

(rad)s!0 0.2 0.4 0.6 0.8 1 1.2 1.4

Away

PTY

(arb

. uni

ts)

-0.05

0

0.05

0.1

0.15

Renk - Phys.Rev.C78:034904,2008Pantuev - private communication

]","97 [# !$

0.25 (stat+sys)± = 0.60 in/PTYoutPTY

-correctedrp%

0" [4.0,7.0] GeV # TAp

± [3.0,4.0] GeV h# TBp

= 200 GeV - Cent 20-60%NNsAu+Au

in-plane out-plane

20-60% Away-side yield out-of-plane< in-planeAway-side yield out-of-plane ~ in-plane0-20%Away-side yield out-of-plane ~ in-plane

Only weak path length dependence

4<pTTrig <7, 3<pTAssoc<4 GeV/c

M.McCumber RHIC/AGS Users 2010

Friday, June 18, 2010

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JET Workshop - June 18th 2010Helen Caines

More direct access to partonic energy

18

γdir → partonic energy

S/B low due to large π0 backgroundγfrag/γdir ~30-40% at pTγ> 8 GeV

Need high pT for clean sample Statistical sample

W.Vogelsang

Au

Au

γ h±

Friday, June 18, 2010

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JET Workshop - June 18th 2010Helen Caines

More direct access to partonic energy

18

γdir → partonic energy

S/B low due to large π0 backgroundγfrag/γdir ~30-40% at pTγ> 8 GeV

Need high pT for clean sample Statistical sample

W.Vogelsang

Au

Au

γ h±PRC 80 024908 (2009)

arXiv:0912.1871

γdir near-side peak non-zero - remaining contamination

- fragmentation photons

Away-side peak - clear suppression

Friday, June 18, 2010

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JET Workshop - June 18th 2010Helen Caines

IAA of away-side γ-hadron correlation

19

π0-h and γ-h display comparable suppressionNo large path length effects in range/accuracy of measurementData disfavors model where energy distributed to low pT at large

angles (Renk-YaJEM)

zT=pTh/pTγ…notethatz≈1forγs,whilez<1forπ0s.

Need more accurate data over wider range to make firm statements

arXiv:0912.1871

M.Connors QM09

Friday, June 18, 2010

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JET Workshop - June 18th 2010Helen Caines

Higher-statistics: Jet-hadron correlations

20

Reconstruct jet:Anti-kT, R=0.4, pt,cut>2 GeV and pt,rec(jet)>20 GeVCorrelate jet direction with hadrons in event Δϕ=ϕJet − ϕassoc., ϕJet = jet-axis found Jet trigger creates large bias - surface?

Δϕ1

Recoiljet

Triggerjet

Δϕ2

Friday, June 18, 2010

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JET Workshop - June 18th 2010Helen Caines

Higher-statistics: Jet-hadron correlations

20

Reconstruct jet:Anti-kT, R=0.4, pt,cut>2 GeV and pt,rec(jet)>20 GeVCorrelate jet direction with hadrons in event Δϕ=ϕJet − ϕassoc., ϕJet = jet-axis found Jet trigger creates large bias - surface?

Increases S/BDecreases background correlations

Δϕ1

Recoiljet

Triggerjet

Δϕ2

Friday, June 18, 2010

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0.2<pt,assoc<1.0 GeV 1.0<pt,assoc<2.5 GeV

pt,assoc>2.5 GeV

Open symbols p+p

STAR Preliminary0-20% Au+Au

STAR Preliminary0-20% Au+Au

STAR Preliminary0-20% Au+Au

J.Putschke RHIC/AGS 2009

JET Workshop - June 18th 2010Helen Caines

Jet-hadron correlations Au-Au vs. p-p

21

High Tower Trigger (HT): tower 0.05x0.05 (ηxϕ) with Et> 5.4 GeV

Open symbols p+p

Open symbols p+p

J.Putschke RHIC/AGS Users 2009

Friday, June 18, 2010

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0.2<pt,assoc<1.0 GeV 1.0<pt,assoc<2.5 GeV

pt,assoc>2.5 GeV

Open symbols p+p

STAR Preliminary0-20% Au+Au

STAR Preliminary0-20% Au+Au

STAR Preliminary0-20% Au+Au

J.Putschke RHIC/AGS 2009

JET Workshop - June 18th 2010Helen Caines

Jet-hadron correlations Au-Au vs. p-p

21

High Tower Trigger (HT): tower 0.05x0.05 (ηxϕ) with Et> 5.4 GeV

Broadening - recoil-side

Softening - recoil-side

Caveat: “Jet v2” effects still under investigation

Direct measurement of

modified fragmentation

Open symbols p+p

Open symbols p+p

J.Putschke RHIC/AGS Users 2009

Friday, June 18, 2010

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!"#$%&'&(("($#)$*%$

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$!"#$%"'+",-./0(&'$#)$*%$

1234$%'"(.5.,&'6$

JET Workshop - June 18th 2010Helen Caines

Preliminary look at jet v2

22

Path length dependence of energy loss?Jet influencing event plane?

A.Ohlson Jet Summer School

Jet appears to be correlated with the event plane

Friday, June 18, 2010

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STAR Preliminary !"##!$%&'(#)*!+*),!-.!/%#(0#%-)!1$!

!2)-!/.3)!4)5.6),!

!4%3,.5!2)-!/.3)!4)5.6),!

!78)(9:(!2)-!/.3)!4)5.6),!

!2)-!/.3)!%-!;9<)&)3-!=!4)5.6),!

JET Workshop - June 18th 2010Helen Caines

Preliminary look at jet v2

22

Jet presence modifies the event planeNeed to calc. event plane using forward detectors

Path length dependence of energy loss?Jet influencing event plane?

A.Ohlson Jet Summer School

Jet appears to be correlated with the event plane

Friday, June 18, 2010

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STAR Preliminary !"##!$%&'(#)*!+*),!-.!/%#(0#%-)!1$!

!2)-!/.3)!4)5.6),!

!4%3,.5!2)-!/.3)!4)5.6),!

!78)(9:(!2)-!/.3)!4)5.6),!

!2)-!/.3)!%-!;9<)&)3-!=!4)5.6),!

JET Workshop - June 18th 2010Helen Caines

Preliminary look at jet v2

22

Jet presence modifies the event planeNeed to calc. event plane using forward detectors

Path length dependence of energy loss?Jet influencing event plane?

A.Ohlson Jet Summer School

Jet appears to be correlated with the event plane pT (GeV/c)

π0 v

2

PHENIX PRC80:054907 (2009)

Friday, June 18, 2010

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JET Workshop - June 18th 2010Helen Caines

Modification of recoil jet

23

Out-of-cone energy R>0.4:10<pt,jet trig <15 GeV/c = 2.47 GeV15<pt,jet trig <20 GeV/c = 2.98 GeV20<pt,jet trig <50 GeV/c = 2.99 GeV

low pTassoc : azimuthal width: Au-Au > p-p

high pTassoc : azimuthal width: Au-Au ~ p-p

J.Putschke RHIC/AGS Users 2009

Friday, June 18, 2010

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JET Workshop - June 18th 2010Helen Caines

Modification of recoil jet

23

Out-of-cone energy R>0.4:10<pt,jet trig <15 GeV/c = 2.47 GeV15<pt,jet trig <20 GeV/c = 2.98 GeV20<pt,jet trig <50 GeV/c = 2.99 GeV

low pTassoc : azimuthal width: Au-Au > p-p

high pTassoc : azimuthal width: Au-Au ~ p-p

low pTassoc : assoc. yield Au-Au > assoc. yield p-p

high pTassoc : assoc. yield Au-Au < assoc. yield p-p

J.Putschke RHIC/AGS Users 2009

Friday, June 18, 2010

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JET Workshop - June 18th 2010Helen Caines

Modification of recoil jet

23

Out-of-cone energy R>0.4:10<pt,jet trig <15 GeV/c = 2.47 GeV15<pt,jet trig <20 GeV/c = 2.98 GeV20<pt,jet trig <50 GeV/c = 2.99 GeV

low pTassoc : azimuthal width: Au-Au > p-p

high pTassoc : azimuthal width: Au-Au ~ p-p

Energy outside R=0.4 ~ accounts for di-jet suppressionEnergy gained at low pT ~ that lost at high pT

low pTassoc : assoc. yield Au-Au > assoc. yield p-p

high pTassoc : assoc. yield Au-Au < assoc. yield p-p

J.Putschke RHIC/AGS Users 2009

Friday, June 18, 2010

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(rad)!"-1 0 1 2 3 4

!"

/dA

B d

NA

1/N

40

41

42

43

44

2.5-3.0 GeV/cA

Tp

0.5-1.0 GeV/cB

Tp

(rad)!"-1 0 1 2 3 4

su

btr

acte

d)

2 (

v!

"/d

AB

dN

A1/N

0

1

2

3

4

R < 0.4"0-10% HT Au+Au:

R cut"0-10% HT Au+Au: no

R < 0.4"HT p+p:

R cut"HT p+p: no

STAR preliminary

v2 = STAR event-plane, v2{4} average

JET Workshop - June 18th 2010Helen Caines

Hybrid-approach: hjet-h

24

Blue: All htrig-hassoc pairs in event Red: htrig-hassoc pairs in event with htrig within ΔR=<0.4 of jet

Same v2 used for both as initial estimationZYAM applied

How to interpret enhanced correlation?- sampling higher Q2 events- removing non-jet background?

Select only events with jet>10GeV, R=0.4, pTpart>2GeV/cLook at h-h correlations

A.Adare RHIC/AGS Users meeting 2010

Au-Au yields larger than p-p at low pTB...qualitatively consistent with

measured h-h IAA.

Friday, June 18, 2010

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(rad)!"-1 0 1 2 3 4

!"

/dA

B d

NA

1/N

40

41

42

43

44

2.5-3.0 GeV/cA

Tp

0.5-1.0 GeV/cB

Tp

(rad)!"-1 0 1 2 3 4

su

btr

acte

d)

2 (

v!

"/d

AB

dN

A1/N

0

1

2

3

4

R < 0.4"0-10% HT Au+Au:

R cut"0-10% HT Au+Au: no

R < 0.4"HT p+p:

R cut"HT p+p: no

(rad)!"-1 0 1 2 3 4

!"

/dA

B d

NA

1/N

40

41

42

43

44 3.0-4.0 GeV/cA

Tp

0.5-1.0 GeV/cB

Tp

(rad)!"-1 0 1 2 3 4

su

btr

acte

d)

2 (

v!

"/d

AB

dN

A1/N

0

0.5

1

1.5

2

2.5

3

3.5

4R < 0.4"0-10% HT Au+Au:

R cut"0-10% HT Au+Au: no

R < 0.4"HT p+p:

R cut"HT p+p: no

STAR preliminary

v2 = STAR event-plane, v2{4} average

JET Workshop - June 18th 2010Helen Caines

Hybrid-approach: hjet-h

24

Blue: All htrig-hassoc pairs in event Red: htrig-hassoc pairs in event with htrig within ΔR=<0.4 of jet

Same v2 used for both as initial estimationZYAM applied

How to interpret enhanced correlation?- sampling higher Q2 events- removing non-jet background?

Select only events with jet>10GeV, R=0.4, pTpart>2GeV/cLook at h-h correlations

A.Adare RHIC/AGS Users meeting 2010

Au-Au yields larger than p-p at low pTB...qualitatively consistent with

measured h-h IAA.

Friday, June 18, 2010

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(rad)!"-1 0 1 2 3 4

!"

/dA

B d

NA

1/N

40

41

42

43

44

2.5-3.0 GeV/cA

Tp

0.5-1.0 GeV/cB

Tp

(rad)!"-1 0 1 2 3 4

su

btr

acte

d)

2 (

v!

"/d

AB

dN

A1/N

0

1

2

3

4

R < 0.4"0-10% HT Au+Au:

R cut"0-10% HT Au+Au: no

R < 0.4"HT p+p:

R cut"HT p+p: no

(rad)!"-1 0 1 2 3 4

!"

/dA

B d

NA

1/N

40

41

42

43

44 3.0-4.0 GeV/cA

Tp

0.5-1.0 GeV/cB

Tp

(rad)!"-1 0 1 2 3 4

su

btr

acte

d)

2 (

v!

"/d

AB

dN

A1/N

0

0.5

1

1.5

2

2.5

3

3.5

4R < 0.4"0-10% HT Au+Au:

R cut"0-10% HT Au+Au: no

R < 0.4"HT p+p:

R cut"HT p+p: no

(rad)!"-1 0 1 2 3 4

!"

/dA

B d

NA

1/N

39.5

40

40.5

41

41.5

42

42.5 4.0-6.0 GeV/cA

Tp

0.5-1.0 GeV/cB

Tp

(rad)!"-1 0 1 2 3 4

su

btr

acte

d)

2 (

v!

"/d

AB

dN

A1/N

0

0.5

1

1.5

2

2.5

3

R < 0.4"0-10% HT Au+Au:

R cut"0-10% HT Au+Au: no

R < 0.4"HT p+p:

R cut"HT p+p: no

STAR preliminary

v2 = STAR event-plane, v2{4} average

JET Workshop - June 18th 2010Helen Caines

Hybrid-approach: hjet-h

24

Blue: All htrig-hassoc pairs in event Red: htrig-hassoc pairs in event with htrig within ΔR=<0.4 of jet

Same v2 used for both as initial estimationZYAM applied

How to interpret enhanced correlation?- sampling higher Q2 events- removing non-jet background?

Select only events with jet>10GeV, R=0.4, pTpart>2GeV/cLook at h-h correlations

A.Adare RHIC/AGS Users meeting 2010

Au-Au yields larger than p-p at low pTB...qualitatively consistent with

measured h-h IAA.

Friday, June 18, 2010

Page 40: Two “particle” correlations at RHICstar.physics.yale.edu/~caines/Presentations/CainesDiHadronGivenJET… · Helen Caines JET Workshop - June 18th 2010 ... method. The area between

(rad)!"-1 0 1 2 3 4

!"

/dA

B d

NA

1/N

40

41

42

43

44

2.5-3.0 GeV/cA

Tp

0.5-1.0 GeV/cB

Tp

(rad)!"-1 0 1 2 3 4

su

btr

acte

d)

2 (

v!

"/d

AB

dN

A1/N

0

1

2

3

4

R < 0.4"0-10% HT Au+Au:

R cut"0-10% HT Au+Au: no

R < 0.4"HT p+p:

R cut"HT p+p: no

(rad)!"-1 0 1 2 3 4

!"

/dA

B d

NA

1/N

40

41

42

43

44 3.0-4.0 GeV/cA

Tp

0.5-1.0 GeV/cB

Tp

(rad)!"-1 0 1 2 3 4

su

btr

acte

d)

2 (

v!

"/d

AB

dN

A1/N

0

0.5

1

1.5

2

2.5

3

3.5

4R < 0.4"0-10% HT Au+Au:

R cut"0-10% HT Au+Au: no

R < 0.4"HT p+p:

R cut"HT p+p: no

(rad)!"-1 0 1 2 3 4

!"

/dA

B d

NA

1/N

39.5

40

40.5

41

41.5

42

42.5 4.0-6.0 GeV/cA

Tp

0.5-1.0 GeV/cB

Tp

(rad)!"-1 0 1 2 3 4

su

btr

acte

d)

2 (

v!

"/d

AB

dN

A1/N

0

0.5

1

1.5

2

2.5

3

R < 0.4"0-10% HT Au+Au:

R cut"0-10% HT Au+Au: no

R < 0.4"HT p+p:

R cut"HT p+p: no

(rad)!"-1 0 1 2 3 4

!"

/dA

B d

NA

1/N

39.2

39.4

39.6

39.8

40

40.2

40.4

40.6

40.8

41

41.2

41.4 6.0-10.0 GeV/cA

Tp

0.5-1.0 GeV/cB

Tp

(rad)!"-1 0 1 2 3 4

su

btr

acte

d)

2 (

v!

"/d

AB

dN

A1/N

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8R < 0.4"0-10% HT Au+Au:

R cut"0-10% HT Au+Au: no

R < 0.4"HT p+p:

R cut"HT p+p: no

STAR preliminary

v2 = STAR event-plane, v2{4} average

JET Workshop - June 18th 2010Helen Caines

Hybrid-approach: hjet-h

24

Blue: All htrig-hassoc pairs in event Red: htrig-hassoc pairs in event with htrig within ΔR=<0.4 of jet

Same v2 used for both as initial estimationZYAM applied

How to interpret enhanced correlation?- sampling higher Q2 events- removing non-jet background?

Select only events with jet>10GeV, R=0.4, pTpart>2GeV/cLook at h-h correlations

A.Adare RHIC/AGS Users meeting 2010

Au-Au yields larger than p-p at low pTB...qualitatively consistent with

measured h-h IAA.

Friday, June 18, 2010

Page 41: Two “particle” correlations at RHICstar.physics.yale.edu/~caines/Presentations/CainesDiHadronGivenJET… · Helen Caines JET Workshop - June 18th 2010 ... method. The area between

JET Workshop - June 18th 2010Helen Caines

Summary

25

Two particle correlations have long given access to jet physics “Triangular” flow could explain “Ridge” and “Mach-cone”

similarity with the bulk matter propertiesfurther study needed

At high pT ridge and mach cone disappearaway-side jet reduced but shape similar to p-p energy redistributed to to low pT

Modeling RAA doesn’t guarantee prediction of IAAGeometry or energy loss mechanisms more important?

Reaction plane analysis hints at path length energy lossJet may show v2

path length dependent energy loss or biased event-plane?γ-h suppression like h-h in pT range exploredJet-h indicate away-side energy broadened and softenedhjet-h although biased give cleaner correlations

Friday, June 18, 2010