1 QGPWS, Jaipur, 1 st – 3 rd Feb 2008 David d'Enterria QGP Winter School Jaipur, India, Feb. 1 st - 3 rd 2008 David d’Enterria CERN High-p High-p T hadrons & jets in hadrons & jets in high-energy nuclear collisions high-energy nuclear collisions
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1QGPWS, Jaipur, 1st – 3rd Feb 2008 David d'Enterria (CERN)
2QGPWS, Jaipur, 1st – 3rd Feb 2008 David d'Enterria (CERN)
OverviewOverview
qhat = ?dNg/dy = ?cs =?
■ Suppressed highpT hadron spectra:
■ Modified highpT dihadron correlations:
■ Full jet reco, jet, modified FFs:
FastkT (D=0.4),area substraction
Hot/dense QCD matter properties via “jet quenching”
3QGPWS, Jaipur, 1st – 3rd Feb 2008 David d'Enterria (CERN)
QCD matter with heavyions: physics menuQCD matter with heavyions: physics menu
ε /T4
T/Tc
▪ Highdensity QCD at smallx: CGC
▪ QCD at hightemperature: QGP
▪ Gaugegravity duality: AdS/QCD
N = 4
SU(Nc)
BH in
AdS5 x S 5
(s tack of 4 D3 bran es)
✱ (de)confinement✱ chiral symm. restoration✱ early Universe thermodyn.
4QGPWS, Jaipur, 1st – 3rd Feb 2008 David d'Enterria (CERN)
Early-time probes of QGPEarly-time probes of QGP
▪ HE AA colls. produce expanding QGP: V~O(103 fm3) for ~10 fm/c▪ Collision dynamics: Diff. observables sensitive to diff. reaction stages
Tim
e
Penetrating
probes t~0.1 fm/c
t ~ 10 fm/c
t ~ 107 fm/c
Final state probes
Penetrating probes
5QGPWS, Jaipur, 1st – 3rd Feb 2008 David d'Enterria (CERN)
Hard probes of hot/dense QCD matterHard probes of hot/dense QCD matter
Z,
“Jet quenching”
J/Ψ & Υ suppression
direct , *, Z(control)
▪ Hard probes: largeQ2 (Q>2 GeV/c), earlytime production (~1/Q<0.1 fm/c) ▪ “Selfgenerated tomographic probes of the hottest and densest phases of AA collisions, well controlled experimentally & theoretically.”
6QGPWS, Jaipur, 1st – 3rd Feb 2008 David d'Enterria (CERN)
““Jet quenching” as a QGP probeJet quenching” as a QGP probe
All these values imply energy densities well above εcrit QCD in thermalized syst.
[BDMPS/PQM]
<q0> ~ 13.2+2.1 GeV2/fm
[Vitev & Gyulassy]
PHENIX, arxiv:0801.1655
-150
-3.2
17QGPWS, Jaipur, 1st – 3rd Feb 2008 David d'Enterria (CERN)
High pHigh pT T suppression (I): hadron “universality”suppression (I): hadron “universality”
■ Photons are unsuppressed but π0,η,h± show a common suppression pattern (magnitude, pT, centrality, ...):
■ Same flat RAA ~ 0.2 up to 10 GeV/c
■ Universal suppression for light mesons consistent with quenching at partonic level prior to q,g fragmentation into leading meson according to vacuum FFs.
PRL 96, 202301 (2006)
✔✔
18QGPWS, Jaipur, 1st – 3rd Feb 2008 David d'Enterria (CERN)
High pHigh pT T suppression (II): psuppression (II): pTTdependencedependence
■ Flat pTdependence described by parton energy loss models:
■ Underlying LPM interference for single gluon bremsstrahlung would give: ∆Eloss ~ log(pT)
■ Combination of diff. effects (convolution w/ realistic parton radiation energy distrib., local parton pT slope, nuclear PDFs ...) yields constant quenching factor.
PQM – A. Dainese, C. Loizides, G. PaicEPJ C 38, 461(2005)
GLV – I. Vitev 2005
✔✔
19QGPWS, Jaipur, 1st – 3rd Feb 2008 David d'Enterria (CERN)
High pHigh pT T suppression (III): Excitation functionsuppression (III): Excitation function
■ c.m. energy dependence in agreement with parton energy loss in increasingly dense medium:
Initial gluon density: Medium transport coeff.: SPSRHICRHIC
D.d'E., EJP C 43 (2005)295PHENIX, arXiv:0801.iii
AuAuCuCu
(less suppression in lighter systems)
✔✔
20QGPWS, Jaipur, 1st – 3rd Feb 2008 David d'Enterria (CERN)
High pHigh pT T suppression (IV): centralitydependencesuppression (IV): centralitydependence
PQM – Loizides EPJ C 38, 461(2005)
■ Increasing centrality i.e. Npart ⇒ increased L, ρ ⇒ larger suppression ■ Theory predicts: log(RAA) ∝Npart
−2/3
■ Agreement data ↔ models as expected for diff. suppressions at diff. (geometrical) parton production points.
PHENIX, arXiv:0801.iii
nEXP~0.58±0.1 consistent with nTH~2/3
✔✔
21QGPWS, Jaipur, 1st – 3rd Feb 2008 David d'Enterria (CERN)
High pHigh pT T suppression (V): pathlength dependencesuppression (V): pathlength dependence
∆φ = 0°
∆φ = 90°
No apparent Eloss for L< 2 fm“Corona effect” effect? V. Pantuev hepph/0506095
Lε
■ Parton Eloss pathlength ∝ L2 (static), L (expanding):
matter thickness
Less suppression inplane (“short” direction) More suppression outofplane (“long” direction)
~2 fm
Eloss approx. linear with L formost centralities,
PRC76, 034904 (2007)
✔✔
22QGPWS, Jaipur, 1st – 3rd Feb 2008 David d'Enterria (CERN)
High pHigh pT T suppression (VI): nonAbelian naturesuppression (VI): nonAbelian nature
■ Gluons radiate ✕2 more than quarks:
■ TEST 1: At fixed pT & increasing √s (i.e. at lower x): increased fraction of gluons ⇒ increased quenching
NonAbelian energy loss modelpreferred over “nonQCD” (qloss=gloss)
Gluon: CA = Nc = 3Quark: CF =(Nc
21)/2Nc = 4/3
pT = 5 GeV/c, √s = 105500 GeV
CA /CF=2.25}
SPS=q
RHIC=q,g
LHC=g D.d'E., EJP C 43 (2005)295qrich
q,g~50%
✔✔
23QGPWS, Jaipur, 1st – 3rd Feb 2008 David d'Enterria (CERN)
High pHigh pT T suppression (VI): nonAbelian nature ?suppression (VI): nonAbelian nature ?
■ TEST 2: A large fraction of highpT (anti)protons from gluonfragmentation ⇒ increased p over quenching
STAR, PRL 97, 152301 (2006)
■ But above 6 GeV/c, similar ,p suppression: no apparent stronger gluon energy loss
(Need new calculations, with latest baryon FF: AKK, DSS)
pT (GeV/ c)
p/ π
40% from gluons
90% p,p from gluons_
dAu
■ However, (anti)proton production not well “calibrated”: enhanced in “cold QCD matter” (extra nonpQCD mechanism ?)
✔✔
24QGPWS, Jaipur, 1st – 3rd Feb 2008 David d'Enterria (CERN)
High pHigh pT T suppression (VII): Mass effect ?suppression (VII): Mass effect ?
⇒ HeavyQ expected to lose less energy than lightq.■ HighpT e± from heavyquark decays equally suppressed as pions: RAA~0.2 above ~6 GeV/c. Radiative energy loss fails to reproduce data.
■ less bottom fraction ? Additional quenching from collisional energy loss ? ⇒ need to directly reconstruct D (and B) mesons.
■ “Deadcone” effect: Massive quarks cannot radiate gluons at low angles (causality requirement: since vQ<c)
STAR, PRL (2006)
PHENIX, PRL (2006)
[Dokshitzer & Kharzeev]
25QGPWS, Jaipur, 1st – 3rd Feb 2008 David d'Enterria (CERN)
High pHigh pT T single hadron suppression: summarysingle hadron suppression: summary
▪ Hadrons (but not ) above pT~5 GeV/c suppressed in central AuAu by a factor of ~5 wrt. “vacuum” (pp) or “cold QCD matter” (dAu) parton fragmentation.
▪ Magnitude of quenching consistent with parton energy loss model predictions in a very opaque system: dNg/dy~1400 or q~13 GeV2/fm
❤ Most observed properties of the quenching factor consistent with radiative Eloss: pT, centrality, √s, pathlength, “nonAbelianity”, ...
A few “glitches” in the canonical interpretation: ♦ no deadcone effect for heavyQ (collisional Eloss ?) ♦ ~2fm pathlength “unsuppression” (“corona” effect ?) ♦ (anti)protons not from gluon fragmentation (extra production ?)
26QGPWS, Jaipur, 1st – 3rd Feb 2008 David d'Enterria (CERN)
High pHigh pT T suppression: outlook (CMS @ LHC)suppression: outlook (CMS @ LHC)
▪ Rich phenomena at intermediate pT: Tantalizing connections to collective medium response to hard partons (speed of sound, index of refraction, ...) but theorydata comparison challenging.
41QGPWS, Jaipur, 1st – 3rd Feb 2008 David d'Enterria (CERN)
III. Jet reconstruction, III. Jet reconstruction, jet, jet, fragmentation functionsfragmentation functions
42QGPWS, Jaipur, 1st – 3rd Feb 2008 David d'Enterria (CERN)
Backup slidesBackup slides
43QGPWS, Jaipur, 1st – 3rd Feb 2008 David d'Enterria (CERN)