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Understanding Jet quenching and Medium-response via dihadron correlations. Df. Jiangyong Jia Stony Brook University & BNL. Thanks Fuqiang Wang for inputs. Medium. Jet. ?. Mostly based on PHENIX paper: nucl-ex/0801.4545. Deer’s antler. 四不像 The “four-unlikes” Pere david’s deer. - PowerPoint PPT Presentation
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1Jiangyong Jia, QM2008, Feb. 8, Jaipur
Understanding Jet quenching and Medium-response via dihadron correlations
Jiangyong Jia Stony Brook University & BNL
Medium
Jet
?
Mostly based on PHENIX paper: nucl-ex/0801.4545
Thanks Fuqiang Wang for inputs
2Jiangyong Jia, QM2008, Feb. 8, Jaipur
Deer’s antler
Horse’s head
Cow’s hoof
Donkey’s tail
四不像The “four-unlikes”
Pere david’s deer
3Jiangyong Jia, QM2008, Feb. 8, Jaipur
Jet quenching & medium response
53
RA
A
pT
1
Jet fragmentation
Flow+Recombination
0.2
d+Au Au+Au 0-5%8 < pT(trig) < 15 GeV/cpT(assoc)>6 GeV
Fragmentation of jets with minimal eloss Dissipation of lost energy in medium
Jet + ridgeSuppressed Jet + hump
The mechanisms for single hadron production are important for dihadron and vice versa
*
4Jiangyong Jia, QM2008, Feb. 8, Jaipur
pT Scan: evolution of jet quenching and medium response
Study the pTa x pT
b dependence of the four components
pTa
pTb
Soft region (medium)
Hard region (jet)
(rad)
Head region (suppressed jet) Shoulder region (hump)
Near region (jet+ridge)
5Jiangyong Jia, QM2008, Feb. 8, Jaipur
pT Scan: evolution of jet quenching and medium response
Can all the features fit in the four-components picture?
Incr
ease
trig
ger p
TIncrease partner pT
Dip develops
Jet reemerges
Yield enhanced
Yield suppressed
6Jiangyong Jia, QM2008, Feb. 8, Jaipur
pt,a pt,b>5
Hard region (jet)
1<pt,a pt,a<4
Soft region (medium)
1<pTa,b < 4 -> RHS<1 -> Shoulder region dominant!
pTa or b >5 -> RHS>1 -> Head region dominant!
pTa or b < 1 -> RHS~1
Competition between “Head” (Suppression) and “shoulder” (enhancement)
Shoulder is important up to ~4 GeV/c
Away-side pT ScanRHS = Head_yield/shoulder_yield (area normalized)
pTa
pTb
RHS<1
RHS>1
7Jiangyong Jia, QM2008, Feb. 8, Jaipur
Near-side pT Scan
For low pT region Au+Au shape in is b
roader than for pp Au+Au yield is enhanc
ed, especially at large .
For high pT region shape/yield is simil
ar between Au+Au and pp
The ridge component is important to ~4 GeV/c
Jet fragmentation takes over at higher pT.
8Jiangyong Jia, QM2008, Feb. 8, Jaipur
Spectra slope at shoulder region
2<pTa<3
3<pTa<4
4<pTa<5
Mean-pT at intermediate pT (1<pTb< 5)
Shoulder slope ~0.45 GeV/c, independent of trigger pT
arxiv:0705.3238 [nucl-ex] Phys.Rev.C77:011901,2008
9Jiangyong Jia, QM2008, Feb. 8, Jaipur
Near-side slope
Ridge slope is slightly harder than the shoulder
J. Putschke QM06
John Chen poster
JetRidge
0.44 GeV/c
0.36 GeV/c
10Jiangyong Jia, QM2008, Feb. 8, Jaipur
Connection between ridge and shoulder
Ridge and shoulder persist up to pTa,pT
b~4 GeV/c They have similar slope (ridge is slightly harder)
0712.3033 nucl-ex
Near-side Away-side
Their particle compositions are similar to bulk. Ridge & Shoulder energies are roughly balanced in a given slice.
Aw
ay_e
nerg
yN
ear_
en
erg
y
0.5<0.7
John Chen poster
0.5<0.7
*
11Jiangyong Jia, QM2008, Feb. 8, Jaipur
Energy dependence for shoulder & ridge
CM<0.7
Head200 GeV Head17.2 GeV Shoulder200 GeV 2x Shoulder17.2 GeV
Near200 GeV 8 x Near17.2 GeV
||<0.35
At SPS Smaller jet quenching+Stronger Cronin
-> Less suppression in Head Smaller medium component
-> Smaller ridge/ Shoulder
RAA at SPS is totally different, dominated by Cronin effect
Ridge is almost gone at SPS energy, the shoulder due to kT broadening?Energy scan is important!
*
12Jiangyong Jia, QM2008, Feb. 8, Jaipur
= per-trig yield
Quantify the medium modifications
Pair Yieldper-trig yield=
Trig Yield
per-jet yield
per-trig yield
AA
pp
per-trig yieldI =
per-trig yieldAA
IAA is a good quantity at high pT(per-trigger yield = per-jet yield) but is diluted by soft triggers at low pT.
Both scales with Ncoll
PairYield
PairYieldAA
AAcoll pp
JN
TrigYield
TrigYieldAA
AAcoll pp
RN
( , )( , )
( )
a ba b AA T T
AA T T aAA T
J p pI p p
R p
( , ) ( , )AA AA
a b b aT T T TJ p p J p p
*
13Jiangyong Jia, QM2008, Feb. 8, Jaipur
Low pT triggerIaa vs pT
Dilution of soft triggers: T-T recombination / triggering on medium response.
Near side
High pT trigger
IAA~1
IAA~ RAAAway side
I AA
14Jiangyong Jia, QM2008, Feb. 8, Jaipur
Dilution of soft triggers
IAA not symmetric wrt trigger/partner pT selection
Near-side
Since one particle is high pT, hadron pair come from jets emitted near surface The second particle in the pair also comes from surface.
But the low pT triggers in per-trigger yield include all soft hadrons.
15Jiangyong Jia, QM2008, Feb. 8, Jaipur
Dilution to ridge
scaledscaled
Scale up the Au+Au by 1/IAA(pTa), then subtract pp
Near-side
~consistent with pp jet + roughly flat ridge
*
16Jiangyong Jia, QM2008, Feb. 8, Jaipur
Another example: Dilution effect in dAu1/
N trig
dN/
d(Δ)
STAR Preliminary
Aud
Large xSmall x
Triggers: ~0, 3 GeV/c partners: ~3, 0.2 GeV/c
g
q
Forward
g
q
Backward
Per-trigger yield
p-p : 1/2
Dilution effect due to trigger counting! Do not need recombination
CGC suppress num. of forward-scattering
Au-side: 1/3d-side: 2/3
Small xLarge x
*
Fuqiang
17Jiangyong Jia, QM2008, Feb. 8, Jaipur
d+Au Au+Au 0-5%8 < pT(trig) < 15 GeV/cpT(assoc)>6 GeV
Geometrical bias?
High pT correlated pairs
Surface emission
Low pT correlated pairs
Bulk emission
Mach cone
ridge
*
18Jiangyong Jia, QM2008, Feb. 8, Jaipur
d+Au Au+Au 0-5%8 < pT(trig) < 15 GeV/cpT(assoc)>6 GeV
Geometrical bias?
High pT correlated pairs
Surface emission
Low pT correlated pairs
Bulk emission
• Low pT triggers may from cone/ridge surface bias reduced!• Each side contain both ridge and cone contributions
19Jiangyong Jia, QM2008, Feb. 8, Jaipur
Jet contribution @ low pT
Quantify the jet contribution in two-particle momentum spaceHelp understand the particle production mechanism
J AA
pTa,pT
b
1
Medium response increase the pair yield at low pT
PairYield
PairYieldAA
AAcoll pp
JN
53
RA
A
pT
1
Jet fragmentation
Flow+Recombination
0.2
TrigYield
TrigYieldAA
AAcoll pp
RN
*
20Jiangyong Jia, QM2008, Feb. 8, Jaipur
Near side pair yield modification: JAA
Approximately scales with pTsum=pT
a+pTb (since coming from same jet)
Reach same level (RAA) at High pTb
PairYield
PairYieldAA
AAcoll pp
JN
Pair yield scale faster than Ncoll at low pTa+pT
b
These pairs are remnants of quenched jets.
21Jiangyong Jia, QM2008, Feb. 8, Jaipur
JAA @ away-side head region Low pT pair yield is not suppressed! Away-side JAA ~ RAA
2 at large pT. away-side jet IAA ~ inclusive jets RAA
J AA(p
Ta ,pTb )
22Jiangyong Jia, QM2008, Feb. 8, Jaipur
3-p correlation telling the same story?
Au+Au Central 0-12% Triggered
2D
D~1.1 D~1.36
Exclusive process selects verydifferent kinematical region and phase space
*
23Jiangyong Jia, QM2008, Feb. 8, Jaipur
RP dependence at low pT Rich dependence patterns of medium response on trigger orientation
PHENIX show jet function, need to ~x (1+2v2trigcos2) to compare. V2/V4 systematics are clearly important!! (enter linearly)
3<pTtrig<4GeV/c & 1.0<pT
asso<1.5GeV/c 20-60%STAR
M. McCumber, A.Feng, Session VIII, Feb. 5
24Jiangyong Jia, QM2008, Feb. 8, Jaipur
Models for medium response Production mechanisms of associated hadrons
New particle creation: feedback of shower gluons, cerenkov gluons
Local heating: bending jet, momentum kick, Mach cone, backsplash, Glasma bending, coupling to transverse or longitudinal flow etc.
Residual correlations with geometry: elliptic flow (subtracted), correlation between radial flow boosted beam and surfaced emitted transverse jet.
Easier to generate large yield by pickup from the bulk (since no particle production is required)
We know the pair yield is enhanced at low pt. Supported by the property of the ridge/cone (PID, slope etc)
Mechanisms for ridge and shoulder may well be related.
*
25Jiangyong Jia, QM2008, Feb. 8, Jaipur
Final remarks: Jet quenching & medium response
Jet @ High pT, surface biased, eloss mechanism is constrained indirectly from those with little eloss
Medium response @ Low pT, no surface bias, directly sensitive to energy loss process.
The energy loss mechanism affects characteristics of medium response, example:
collisional/radiative <-> momentum kick/gluon feedback. Different medium response mechanism may require diffe
rent energy loss scenario. Energy loss and energy dissipation to the medium
are modeled separately. But there shouldn’t be a strict separation of scale, especially for intermediate pT.
Need a unified framework that include both jet quenching & medium response, and can describe correlation data at all pT.
More details:M. McCumber, Session VIII, Feb. 5H.Pei, A.Adare, SessionIX, Feb.8
Poster 23,24
26Jiangyong Jia, QM2008, Feb. 8, Jaipur
Backup
27Jiangyong Jia, QM2008, Feb. 8, Jaipur
Constraining the eloss dynamics
Shift to left
Case I
pT
Yield p+p
A+A
AbsorptionDownward shift
Case II
Absorption Longer path for away-side jet, IAA<RAA Independent of spectra shape
Left shift Stronger energy loss, IAA>RAA Flatter away-side spectra IAA<RAA
Data suggests IAA ~ RAA Flatter spectra compensated by bigger energy
loss By combing IAA and RAA, one gain some
sensitivity on energy loss.
dn/dpt ~(1/pt)9 for single spectra
dn/dpt ~(1/pt)5 for away-side spectra
8.1 2
1( )1 ( ) 0.23T
AA TT
E pR p
p
4.8 1
1( )1 ( ) 0.35T
AA TT
E pI p
p
50% bigger
nucl-ex/0703047
28Jiangyong Jia, QM2008, Feb. 8, Jaipur
d+Au Au+Au 0-5%
Per
-trig
ger
yiel
d
8 < pT(trig) < 15 GeV/c pT(assoc)>6 GeV
High pT: jet fragmentation
Observed jet are those “do not” suffer much energy loss.
Near-side: surface emission Away-side: tangential/punch-through emission.
Iaa~Raa, consistent with energy loss calculation
H. Zhang, J.F. Owens, E. Wang and
X.-N. Wang , PRL 98(2007)212301
29Jiangyong Jia, QM2008, Feb. 8, Jaipur
Low pT: medium response to jet Away-side: strongly modified shape and yield
Suppressed jet (head region) + medium-induced component (Shoulder region)
Near-side: elongated structure in , enhancement in yield. Surface Jet + medium-induced component (ridge)
STAR
(rad)
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