Soft sector: promises, promises...
-
Upload
illiana-hunter -
Category
Documents
-
view
39 -
download
0
description
Transcript of Soft sector: promises, promises...
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 1
Soft sector: promises, promises...
~ 10 GeV/fm3 >> C (Bjorken / hydro)
• Early thermalization (v2 / hydro)
• Tchem ~ TH ~ Tc ~ 170 MeV
b ~ 30-40 MeV -- near baryon free connection to lattice?
• further evolution (PdV work?) & expansion leading to...
• cooling and bulk collective motion (pT spectra, v2, HBT, K-)
Can we use an external probe to explore further?
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 2
Discovery and Properties: The Ideal Experiment
The first exploration of subatomic structure was undertaken by Rutherford at Manchester in 1909 using Au atoms as targets and particles as probes.
incoming electron(controlled probe)
scatteredelectron
Can we do the same at RHIC?
QGPNOBut we can get close ………
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 3
Fast Partons (Quarks & Gluons) Traversing Matter
• Jets:
– high-pT parton produced in a hard (high-Q) scattering process
– Calculable in QCD (at high-pT)
– partons fragment into many correlated white hadrons
• emitted in a cone
– created early in the collision quark
quark
hadrons
hadrons
leading particle(highest-p particle)
p+p sNN=200 GeV
PHENIX PRL 91 241803 (2003)
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 4
Fate of jets in heavy ion collisions?
p
p
?
Au+Au
idea: p+p collisions @ same sNN = 200 GeV as reference
?: what happens in Au+Au to jets which pass through medium?
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.The tail probes the bulk
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 5
The Ubiquitous RAA…
Nuclear overlap model to calculate # incoherent NN collisions (no shadowing etc)
RAA = (# seen in nuclear collision) / (# expected)
(PHENIX notation: f=centrality cut)
5x fewer high pT particles than “expected” in AuAu
Required checks:• saturation (initial-state) effect?
20
0 G
eV
0 R
AA
PHENIX (and all others) PRL2003
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 6
The control experiment: d+Au, 2003
?
Au+Au
Aud
AuAu
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 7
Centrality Dependence
• Dramatically different and opposite centrality evolution of Au+Au experiment from d+Au control.
• Jet Suppression is clearly a final state effect.
Au + Au Experiment d + Au Control Experiment
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 8
The Ubiquitous RAA…
Nuclear overlap model to calculate # incoherent NN collisions (no shadowing etc)
RAA = (# seen in nuclear collision) / (# expected)
(PHENIX notation: f=centrality cut)
5x fewer high pT particles than “expected” in AuAu
Required checks:• saturation (initial-state) effect?
• d-Au null result• hard scattering rates understood?
• measure “robust” hard processes
20
0 G
eV
0 R
AA
PHENIX (and all others) PRL2003
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 9
Hard non-mesonic (“direct”) photons & non-photonic (“charming”) electrons
NB: pT-integrated
PHENIX QM04
PHENIX 2004
• Created in earliest, hardest parton scatterings & conserved thereafter
• binary scaling √• (probably some Cronin inside errors)
• probe-once-created and creation itself in AA are “calibrated” (better than d-Au)
PHENIX
Direct photons visiblebecause 0 is suppressed!!
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 10
The Ubiquitous RAA…5x fewer high pT particles than
“expected” in AuAu
Required checks:• saturation (initial-state) effect?
• d-Au null result• hard scattering rates understood?
• measure “robust” hard processes• charm / direct follow Nbinary
20
0 G
eV
0 R
AA
PHENIX (& all others): PRL 2003
Accepted view• final state effect is partonic energy loss
in color-charge-dense(not necc. deconfined) medium
= 15 GeV/fm3 @ = 0.2 fm• ~ consistent w/ BJ and hydro…
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 11
The Ubiquitous RAA…5x fewer high pT particles than
“expected” in AuAu
Required checks:• saturation (initial-state) effect?
• d-Au null result• hard scattering rates understood?
• measure “robust” hard processes• charm / direct follow Nbinary
20
0 G
eV
0 R
AA
PHENIX (& all others): PRL 2003
Accepted view• final state effect is partonic energy loss
in color-charge-dense(not necc. deconfined) medium
= 15 GeV/fm3 @ = 0.2 fm• ~ consistent w/ BJ and hydro…
is it “jet” quenching?Go beyond leading particles
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 12
Beyond leading particles
STAR p+p event
find this…
STAR Au+Au event
…in this
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 13
Jets via azimuthal correlations
STAR p+p event• trigger: highest pT track, pT>4 GeV/c
• distribution for 2<pT<pTtrigger
• normalize to number of triggers
trigger PRL 90, 082302
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 14
Jets via azimuthal correlations
STAR Au+Au event
Try the same in Au-Au(large combinatorics)…
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 15
Azimuthal distributions in Au+Au
pedestal and flow subtracted
PRL 90, 082302
Central collisions:• strong suppressionof away-side jet
Peripheral collisions:• very similar to p+p
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 16
Further geometric detail
midcentral (20-60%) collisions
nucl-ex/0407007
Suppression depends on pathlength thru medium
This analysis: cannot be initial state effect
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 17
anything new in-between?
?
Probes of the system (hard)• interesting results• important open questions
System itself (soft)• interesting/important results• important open questions
If we bridge the gap (“firm”)?
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 18
Connecting the sectors
• hydro breaks down above~ 2 GeV/c (expected)
• mass systematic meson/baryon systematic?
•definitely not hydro!
symmetry, thermal smearing
mass syste
matic
v2 generatedby anisotropicenergy loss?
soft-firm connection: v2
P. Sorensen, SQM04
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 19
soft-firm connection: v2
• hydro breaks down above~ 2 GeV/c (expected)
• mass systematic meson/baryon systematic?
•definitely not hydro!
v2 generatedby anisotropicenergy loss?
PID-differentialmeson/baryon systematic!
hard-firm connection: RAA
BUT!…
Connecting the sectors
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 20
PR
L 92
(20
04
) 05
23
02
Non-hydro / non-E origin of firm v2?
meson/baryon (i.e. constituent quark number) systematics suggest…
coalescence (“recombination”) of already-flowing (!!) partons (*)
* well, constituent quarks
€
v2hadron (pT
hadron ) ≈ nv2quark (pT
quark )
pThadron ≈ npT
quark
PR
L 92
(20
04
) 05
23
02
P. Sorensen, SQM04
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 21
A growth industry...
Many model variantsLin, Molnar, Pratt,Fries, Bass, Mueller,Ko, Das, Levai, Hwa,Greco, Voloshin, Nonaka…
Many schemes, all describe “anomalous” B/M, RAA, v2
But, data themselves (IMHO) clearly indicate exciting, collective partonic behaviour
Hope for a “hadronization testbed”?
… for a thermal source
Baryons compete with mesons
Fragmentation wins out for a power law tail
B. Mueller TBS05
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 22
bulk, collective system ~ 10 0
Tch~ TC ~ 170 MeV; b~30 MeV
Tkin~100 MeV, flow~0.7c
hydro worksearly thermalization.sensitivity to early-stage EoS
“calibrated” probes:final state effectcolor-dense mediumnew at RHIC (?)sensible geometrical systematics ~ 10 0
baryon / meson systematicsunexpected!(constituent?) partonic collectivity?![possibility to test hadronization
mechanisms?]
high pT
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 23
Open Issues
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 24
soft sector questions
• hydro and v2
– hydro “limits” ?
– EoS - does Lattice really work
• RHIC HBT “puzzle”
– puzzle #1: failure of (otherwise-successful) dynamical models
– puzzle #0: generic “failure” - no sign of P.T.
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 25
hydro “limit”?
we have a bad history in RHI
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 26
Trends, soft sector, and RHI historyMotivation Formalism Experiment Trends Models
Art’s talk. Compiled byA. Wetzler (2005)
6 decades of E/A(2 decades of sNN)Gyulassy 1995
Just oneevent!
Finally, weunderstand it!
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 27
hydro “limit”?
Kolb, Sollfrank, Heinz, PRC62 054909 (2000)
dN/dy
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 28
Disintegration timescale
Relative momentum between pions is a vector can extract 3D shape information
p2
p1
q
12Kpp=+rrr
Rout
Rlong – along beam direction
Rout – along “line of sight”
Rside – “line of sight”
Rside
increases with emission timescale
€
rq =
r p 1 −
r p 2
€
rK =
r p 1 +
r p 2
€
↔ Rout
Rside
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 29
Disintegration timescale - expectation
3D 1-fluid Hydrodynamics Rischke & Gyulassy, NPA 608, 479 (1996)
withtransition
withtransition
“” “”
Long-standing favorite signature of QGP:
• increase in , ROUT/RSIDE due to deconfinement confinement transition
• expected to “turn on” as QGP energy threshold is reached
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 30
Disintegration timescale - observation
• no threshold effect seen
• RO/RS ~ 1
4
6
8
4
6
8
1.0
1.25
1.5R
O (
fm)
RS (
fm)
RO
/ R
S
increasing collision energy
RHIC
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 31
Disintegration timescale - observation
• no threshold effect seen
• RO/RS ~ 1
• toy model calculations suggest very short timescales
F. Retiere & MAL, PRC 70 (2004)
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 32
Disintegration timescale - observation
PCM & clust. hadronization
NFD
NFD & hadronic TM
PCM & hadronic TM
CYM & LGT
string & hadronic TM
N()
Heinz & Kolb, hep-ph/0204061
• no threshold effect seen
• RO/RS ~ 1
• toy model calculations suggest very short timescales• rapid, explosive evolution• too explosive for “real” models
which explain all other data
An important space-time“puzzle” at RHIC
- actively under study
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 33
STAR, PRL93 012301 (2004)
Measured final source shape
centralcollisions
mid-centralcollisions
peripheralcollisions
Expected evolution:
2x
2y
2x
2y
RR
RR
+−
≡
20,S
22,S
FO R
R2≈
• estimate INIT from Glauber
• from asHBT:
Shape evolution: never goes in-plane?
STAR PRL93 (2004) 012301
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 34
firm/hard sector questions
• firm
– entropy issue (I really don’t care - theorists will work it out)
– what is a “dynamical constituent quark”?
• hard
– no consistent energy loss scenario describing geometrical systematics of energy loss (Miodosewski/Tannenbaum)
– is charm quenched? What about dead cone?-- can it be gluon radiation?
– both issues do we really understand the energy loss mechanism?
– if not, how can we say we probe color density
– and, if so, what can we say besides color density (e.g. deconfined or not)
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 35
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 36
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 37
20
0 G
eV
0 R
AA
PHENIX (& all others): PRL 2003
The Ubiquitous RAA…5x fewer high pT particles than
“expected” in AuAu
Common wisdom:• d-Au null effect final state effect
• so obvious that initialdAu = AuAu?
• look at other hard probes from same initial processes, but withno final state effects…
Common wisdom II:• final state effect is energy loss in
color-charge-dense(not necc. deconfined) medium
= 15 GeV/fm3 @ = 0.2 fm• ~ consistent w/ BJ and hydro…
Important result!Several complicated (& diff) ways to get suppression?Several canceling effects?
Look closer in a more natural way…
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 38
If we are looking at energy loss…
…why quantify downward shift of spectrum (as in RAA)?
PHENIX PRL 2003
It seems more natural to quantify leftward shift.[Tannenbaum/Mioduzewski]
NB: ignores• Cronin (see jets() coming up…)• mods in FF (logical to look at shift of
partons not their fragments)
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 39
ÿ p-p 0 spectrum: power law:
€
dn
dpT
2=
A
pT
n with n = 8.1 ±0.1
ÿ p T shift , UTloss
UT
UT
ST pSpSpp )1()( −=−=
o pTU = pT with no energy loss
o pTS = pT with energy loss
o Sloss = (pTU- pT
S)/ pTU
= fraction of pT lost
)2/(11 −−= n
AAloss RS
…then let’s look at energy lossEmpirical energy loss
Tannenbaum/Mioduzewski
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 40
ÿ p-p 0 spectrum: power law:
€
dn
dpT
2=
A
pT
n with n = 8.1 ±0.1
ÿ p T shift , UTloss
UT
UT
ST pSpSpp )1()( −=−=
o pTU = pT with no energy loss
o pTS = pT with energy loss
o Sloss = (pTU- pT
S)/ pTU
= fraction of pT lost
)2/(11 −−= n
AAloss RS
Initial pathlength dependence seems to work
–Gyulassy, Vitev, Wang:
• 1D expansion, simple geometric scaling Well reproduced by experimental data.
3/2partNE ∝
PHENIX prelimAu+Au √sNN=200 GeV
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 41
Vary pathlength another way…
PHENIX prelimAu+Au √sNN=200 GeV
(deg)
qualitatively OK, now see about consistency…
PHENIX B. Cole, HardProbes 04
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 42
No universal loss versus density path?
€
dncolor
dA∝
dnpart
dA
ρρ 0init
colorcolor )( =Txr
PHENIX preliminar
y
pT > 3 GeV/c
Overlapintegral:
1Dexpansion
ρpart(x,y) vs centrality10-20% 50-60%
• Quantitative consistency required to claim “jet tomography”
• Next level of precision needed to clarify underlying quenching mechanism
• also -tagging, charm/dead-cone, q/g jet selection, correlated quenching signal versus length
• (Role of dynamics in differential analysis may be significant)• cannot just put by-hand some energy loss & find consistency w/BJ
PHENIX B. Cole, HardProbes 04
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 43
PHENIX Preliminary
RAA (2.5<pT<5.0 GeV/c)
Nu
clea
r m
odif
icat
ion
fac
tor
Converter method
Cocktail subtraction method
pT (GeV/c)
HINT of charm suppression??
Too early to tell (May05)
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 44
Backup
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 45
Parton Number Scaling of Elliptic Flow
In the recombination regime, meson and baryon v2 can be obtained from the parton v2 (using xi = 1/n):
( ) ( )
3
2
2 2
2
2
22
2
2
3v 32v2
v
1 2 v
v3 3
v
1 6 v32
and
p pt t
B
p t
Mt t
p tp t
p p
p
p
pp p
⎛ ⎞⎛ ⎞ ⎛ ⎞+⎜ ⎟ ⎜ ⎟⎜ ⎟
⎛ ⎞⎜ ⎟⎝ ⎠=
⎛ ⎞⎛ ⎞+ ⎜ ⎟⎜ ⎟
⎝
⎝ ⎠ ⎝ ⎠⎝ ⎠=⎛ ⎞⎛ ⎞
+ ⎜ ⎟⎜ ⎟⎝ ⎠⎝⎠ ⎠⎠⎝
Neglecting quadratic and cubic terms, a simple scaling law holds:
( ) ( )2 2 2 2an vv23
vd2
v 3M B ptt
tp tpp
pp
⎛ ⎞=
⎛ ⎞= ⎜ ⎟
⎝⎜⎝ ⎠ ⎠
⎟
Originally poposed by S. Voloshin
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 46
Suppression vs Collision Energy
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 47
NO suppression in d+Au!
BRAHMS
Phobos
STAR
PHENIX
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 48
Hadron dependence of high-pt suppression
• R+F model describes different RAA behavior of protons and pions
• Jet-quenching becomes universal in the fragmentation region
Mueller & Fries [Mueller TBS05]
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 49
Centrality dependence of open charm in Au+Au
Compare to (PYTHIA) an event generator tuned for pp collisions…
no largesuppression- unlike lightquarks!
Spectra of electrons from c e + anythingphotonic sources are subtracted
central
peripheral
Comparison to pp should be available this week.
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 50
inclusive ee v2
charmed ee v2
If charm quarks also flow, charm quarks are thermalized and / or suppressed (interact with matter) similarly to the light quarks.
STAR SQM04
nucl-ex/0502009
•charmed electron v2 > 0•rule out an extreme case, charm does not interact with QGP and fragment in vacuum into D meson•get charm quark v2 with quark coalescence assumption
Flowing Charm? [F. Laue TBS05]
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 51
Inclusive Single
PHENIX Preliminary
Run2 AuAu 200 GeV
Direct photons are enhanced w.r.t. production, but it’s just because is suppressed, and the direct photons are in fact binary scaled.
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 52
STAR : nucl-ex/0409033 non-flow reduced
v2{2}
v2{RP}
PHENIX Preliminary
Different ways to reduce non-flow correlation, v2 w.r.t. SMD R.P.
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 53
Sonic boom from quenched jets Casalderrey,ES,Teaney, hep-ph/0410067; H.Stocker…
• the energy deposited by jets into liquid-like strongly coupled QGP must go into conical shock waves, similar to the well known sonic boom from supersonic planes.
• We solved relativistic hydrodynamics and got the flow picture
• If there are start and end points, there are two spheres and a cone tangent to both
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 54
away <pT> dependence on angle (STAR,preliminary)
Preliminary
<pT> (phi) has a dip structure in central AA.
Mach shock wave?
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 55
Viscosity of QGP
QGP at RHIC seem to be the most idealfluid known, viscosity/entropy =.1 or so water would not flow if only a drop with 1000 molecules be made
• viscous corrections1st order correction to dist. fn.:
:Sound attenuation length
Velocity gradients
Nearly ideal hydro !? D.Teaney(’03)
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 56
Comparison Au+Au/p+p at Lower Energies
• Pb+Pb collisions at s ~ 20 GeV at CERN/SPS
Crossing at ~ 1.5 GeV/c
Transverse Momentum (GeV/c)
parton energy loss (if any) is overwhelmed by initial state soft multiple scattering(Cronin effect)
RA
A
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 57
Many measurements measure at high pT(!)
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 58
What data can tell us / what (we think) it has told us /open issues
• Hard Sector:
–incoherence of initial state
• calibration of number of initial hard scatterings (binary), which themselves have calibrated spectrum [charm, gamma, d-Au]
–early system color charge density (not deconfinement!)
• if gluonic bremstrahlung: dNg/d ~ 1000 ~BJ
• BUT… energy loss mechanism unclear (consistent scaling?)
• relevant upcoming data:–charm quench (early results limited) / dead cone effect-tagged jets
–q/g jet selection
–higher stats correlated quenching signal versus length
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 59
What data can tell us / what (we think) it has told us /open issues
• Soft sector:
–“threshold behaviour”
• no evidence: “evolution, not revolution”: too bad but not a killer
–degree to which it is system - real collectivity
• solid evidence from several observations - very important [perfect fluid?]
–global/thermodynamic properties: T, , P, • consistent with deconfinement - [but! may be P.S. dominance]
– dynamics - system response evolution and timescales
• 2x expansion, collective shape evolution
• timescales- correct dynamic signatures, wrong (x,t) evolution??
June 2005 mike lisa - Cracow School of Theoretical Physics, XLV - Zakopane Poland 60
What data can tell us / what (we think) it has told us /open issues
• Firm Sector:–“transition bulk to probe” (hadn’t really been considered…)
• clearly something new instead!• ?is there a transition? does all fit smoothly?
–first “calibration” of QGP p.s. structure• hope for well-defined ordered (x-p correlated) system of partons • can we get beyond simple models? entropy issues? connection
between constituent quarks and partons?…
My feeling: solution of open issues in hard & soft sectors willbe well worth it, if we can exploit apparent promise of firm.
Launchpad of next generation program: understanding hadronization