charles gale mcgill hard probes 2004 in-medium effects on electromagnetic probes hard probes 2004...

Hard Probes 2004 Charles Gale

McGill

In-medium effects on electromagnetic probes

Hard Probes 2004

International Conference onHard and Electromagnetic Probes of High Energy Nuclear Collisions

McGill

In-medium: what medium?

DOE/NSF NSACLong Range Plan

Phase-space trajectory goes through qualitatively different media

McGill

The information carried by EM radiation

fk 2| |fi

4 ˆ| ( ) ( ) |fiS f d x J x A x i [photons]

4 4 ˆ| ( ) ( ) ( ) |efiS f d xd yJ x D x y J y i

[dileptons]

4(2 ) ( ) ( )2

ˆ ˆ| | | |

fi i f i f

gR P k P P k P

f J i i J f

[photons]

absorption emission

McGill

Info carried out, II

Thermal rates: avg over initial

states & sum over final

1(2 ) ( )

2 (2 )

ˆ ˆ| | | |

g d kdR e p p k

j J i i J f

Thermal ensemble average of the current-current correlation function

McGill

Info, III

1( ) (2 ) ( )

ˆ ˆ| | | |

f k e p p kZ

f J i i J f

Isolate the correlation

Function:

Spectral representation

2( ) Im ( )

( 1)Rf k k

A direct connection to the in-medium photon self-energy

McGill

Info, IV

1Im ( )

(2 ) 1

d R gk

Emission rates:

[photons]

3 3 6 4

2 1 1Im ( )

(2 ) 1

d R eE E L k

d p d p k e

[dileptons]

2( )lL p p p p g p p m

McGill

Info, V

A model for the hadronic electromagnetic current: VMD

2 2 2e e eJ m m m

The current-field identity(J. J. Sakurai)

Im Im ImVMD

TT TJ J D Spectral density

The photon/dilepton signal can tell us about the in-medium

spectral densities of vector mesons

McGill

Vector Meson Spectral Densities: A Sample Calculation I

Ralf Rapp and Charles Gale, Phys. Rev. C 60, 024003 (1999)

McGill

The interaction is constrained by basic hadronic phenomenology

Chiral U(3)L x U(3)R Massive Yang-Mills:

2 † 2 †

1 1Tr Tr M U + U

Tr Tr2non-minimal terms

L L R R L R R

F D UD U F

F F F F m A A A A

Parameters and form factors are constrained by hadronic phenomenology:•Masses & strong decay widths•Electromagnetic decay widths•Other hadronic observables:

• e.g. 1 /a D S

McGill

Vector Meson Spectral Densities

The spectral density is flattened

and broadened

McGill

Vector Meson Spectral Densities, IV(adding baryons)

R. Rapp & Wambach, 1999

McGill

Vector spectral densities from data

c.m.c.m.

1 exp( )1( )

12 4 sin2

apR a PR

q r if s W s

q sM s i

3( , ) 4 ( ) ( )

(2 )a a a

d k sE p n k f s

•Should hold near the mass-shell•Adler decoupling enforced

E. V.Shuryak, Nucl. Phys. A 533, 761 (1991); V. L. Eletsky and V. L.Ioffe, Phys. Lett. B 401, 327 (1997); Eletsky, Belkacem, Ellis, Kapusta,Phys. Rev. C 64, 035202 (2001)

McGill

Two approaches:

•Rates are also constrained by nuclear photoabsorption data•Mass shifts & broadening are related by dispersion relations

Rapp & WambachEletsky, Ioffe, Kapusta

McGill

Vector Meson Spectral Densities, VI

V. Eletsky, et al., PRC 2001 Teodorescu, Dutt-Mazumder, Gale, PRC 2002

McGill

Fold in With a Dynamical Evolution Model

Huovinen et al., 2002

What’s new? Photons…

McGill

The intermediate mass sector

• Direct connection to Hard Probes• Off-shell effects are potentially important for

effective hadronic interactions Gao & Gale, PRC 57, 254 (1998)

• A lot of data already exists!

NA50Pb-Pb 158 GeV

central collisions

charm DY

McGill

e+ e- Data: A Wealth of Information

• OLYA

• CMD

• DM-1(2)

• ARGUS

• M3N

McGill

4( / ) ( ) ( ) ( )

2 2em VdR

MT K M T M M MdM

I. Kvasnikova, C. Gale, and D. K. Srivastava, PRC 65, 064903 (2002)

Z. Huang, PL B361, 131 (1995)

McGill

A larger comparison

Agreement across approaches

McGill

Li and Gale, PRC (1998)

Intermediate mass data

A. L. S. Angelis et al. (Helios 3), Eur. Phys. J. (1998)

R. Rapp & E. Shuryak, PLB (2000)

McGill

NA50 Data (cont’nd)

I. Kvasnikova, C. Gale, and

D. K. Srivastava, PRC 2002

•In agreement with multiplicity dependence•Includes detector acceptance & efficiency

(O. Drapier, NA50)

McGill

Intermediate masses: partial summary

• Agreement across models: thermal dileptons are seen

• Case for charm enhancement: weak

• QGP: at most 15-20%

• DY? (J. Qiu)

• NA60

McGill

Electromagnetic radiation from the partonic sector

“Basic” approaches

McLerran, Toimela (1986); Kajantie, Kapusta, McLerran, Mekjian (1986)Baier, Pire, Schiff (1988); Altherr, Ruuskanen (1992)

Rates diverge: 2ln( / 0)s T q

HTLresummation

McGill

• HTL program: Klimov (1981), Weldon (1982)

Braaten & Pisarski (1990); Frenkel & Taylor (1990)

2Im lnR

Kapusta, Lichard, Seibert (1991)Baier, Nakkagawa, Niegawa, Redlich (1992)

Going to two loops: Aurenche, Kobes, Gelis, Petitgirard (1996) Aurenche, Gelis, Kobes, Zaraket (1998)

Co-linear singularities:2

2s sth

McGill

Singularities can be re-summed

Arnold, Moore, and Yaffe

JHEP 12, 009 (2001); JHEP 11, 057 (2001)

• Incorporates LPM

• Complete leading order in S

• Inclusive treatment of collinear enhancement, photon and gluon

emission

Can be expressed in terms of the solution to a linear integral equation

McGill

How big (small) is this?

PhenomenologicalExploration…

Turbide, Rapp & Gale (2004)

McGill

Photons?

Sinha & Srivastava, 2001 Huovinen et al., 2002

No baryons

McGill

• Same spectral densities as low mass dileptons• Same dynamical model; same boundary conditions• Cronin contribution estimated from pA data (E629, NA3)• QGP: small

Turbide, Rapp & GalePRC 2004

McGill

WA98: new analysis

Low pT spectrum sensitive to thepion-pion cross section in the

scalar-scalar channel: Chiral symmetry?

Turbide, Rapp & Gale, in preparation

McGill

@ RHIC

• There is a window

Turbide, Rapp & Gale PRC (2004)

McGill

–Isospin mixing–G-parity violation

Exotica? (squeezing dileptons out of broken symmetries, part I)

• Medium-induced symmetry breaking:– Lorentz symmetry scalar-vector mixing

( )S. A. Chin (1977); A. Weldon (1992); Saito, Tsushima, Thomas, Williams (1998); Wolf, Friman, Soyeur (1998)

McGill

Mixing Enables a Hybrid Correlator

• Vanishes in vacuum

• Non-zero in matter

4 . . { ( ) (0)} . .iq x V Sd xe g s T j x j g s

0 (980)

( ) :1 (0 )G PC

New channels:

McGill

0a Polarization

2 3 22 *

0, 3 * 4 2

( )( ) 2 (2 )

2 ( ) 4( )a

qk k q

g g q d k qq q q m

m E k q k q

•Axis: q=(q0,0,0,qz)

•Current conservation:

•One indep. Component

•Static limit

•Recall:

lim 0q

0, 0( 0) ( ,0)L Tq q

McGill

A New Resonant Structure

0a NN e e

The coupling to the a0 generates a peak that is completely absent in the vacuum dilepton spectrum: a genuine in-medium signature

McGill

Is This Observable?At the GSI, HADES has the required resolution, and the energy is appropriate to maximize the effect

Teodorescu, Dutt-Mazumder, Gale (2002)

McGill

Squeezing dileptons out of broken symmetries, part II

• Furry’s theorem at finite T:

1 2 2 1

En A A A n e

1 2 2 1

En A A A n e

Sum over all states contains:1 2 2 1

En A A A n e

McGill

Squeezing dileptons out of broken symmetries, part II

• Furry’s theorem at finite T and charge density:

1 2 2 1 1 2 2 1

( ) ( )n n n n

E Q E Qn A A A n e n A A A n e

• The mirror term this time is

1 2 2 1

( )n n

E Qn A A A n e

McGill

So What?• Then: gg e e

1Tr[ ] Tr[ ]

( ) ( )

d qT eg t t

q p k q q p

Electromagnetic signature of early gluon densities!Majumder, Bourque, Gale PRC (2004), and

In progress

McGill

Quenching = Jet-Plasma interaction

The plasma mediates a jet-photon conversion

Fries, Mueller & Srivastava, PRL 90, 132301 (2003)

McGill

Jet-plasma interactions: EM signatures

• Real photons from quark-antiquark annihilation

• Small t and u dominate the phase space, leading to

9s qed u t

dt s t u

andq qp p p p

1( ) ( ) ( )

dE s p p p p

The process can be visualized as q (q)

McGill

Photons from QCD Compton2

23s qed u s

dt s s u

( ) ( )q

dE s p p

Photon yield from the jet-plasma interaction:( )

4 3 61

23 ( )

( 4 )(

)[1 ( )] ( ) ( )2

d xd p

s s md p

f p f p s q qE E

4 3 61

23 ( )

( )[1 ( )] ( ) ( )2

d xd p

p f p f p s q qE E

McGill

Jet characteristics are calculable

McGill

Photon sources• Hard direct photons

• EM bremsstrahlung

• Thermal photons from hot medium

• Jet-photon conversion

McGill

Results (photons)•RHIC

McGill

Results (photons)•LHC

Fries, Mueller & Srivastava, PRL 90, 132301 (2003)

McGill

Energy loss in the jet-photon conversion? Jet bremsstrahlung?

Use the approach of Arnold, Moore, and Yaffe

JHEP 12, 009 (2001); JHEP 11, 057 (2001)

• Incorporates LPM

• Complete leading order in S

• Inclusive treatment of collinear enhancement, photon and gluon

emission

Can be expressed in terms of the solution to a linear integral equation

McGill

E loss/gain: some systematics

( , )qqg k p k

( ) ( , ) ( , )( ) ( )

( , )2 ( )

q qq qg qg

dP p d p k k d p kP p k P p

dt dk dt dk dt

d p k kP p k

( ) ( , ) ( , )( ) ( )

( , )( ) (2 )

q gg qg gg

g gqq gg

dP p d p k p d p k kP p k P p k

dt dk dt dk dt

d p k dP p k p

dk dt dk dt

•Includes E gain•Evolves the whole distribution function

McGill

Time-evolution of quark distribution

Time-evolution of an initially monoenergetic ensemble of quarks. Evolution of only the avg. Eis also shownS.Jeon and G. Moore, hep-ph/0309332

The entiredistribution isevolved by the collision Kernel(s)

Turbide, Gale, Jeon, and Moore (2004)

McGill

Energy loss: hadrons

• Energy loss systematics not in conflict with experimental data

Turbide, Gale, Jeon, and Moore (2004)

McGill

Jet-bremss.:

RHIC jet-plasma photons

With E loss

McGill

E loss: photons

McGill

McGillFries, Srivastava, Gale (2004)

McGill

Jet-plasma interactions: measurable EM signatures!

• RHIC:– Jet-plasma interaction is the dominant source of

photons up to pT ~ 6 GeV. – Conclusions unchanged by energy-loss considerations– Dilepton signal competes with Drell-Yan (NLO)

• LHC:– Jet-plasma photon signal is still important– Large mass lepton pairs dominate over Drell-Yan

emission.

Towards a consistent treatment of jets & EM radiation

McGill

Summary & Conclusion• Low and intermediate mass dileptons: theory is in

good shape: NA60• Soft real photons: a (first) window to chiral symmetry?• There are measurable electromagnetic signatures of

jet-plasma interaction: those constitute complementary observables that would signal the existence of conditions suitable for jet-quenching to take place.

• EM radiation and hard probes: the start of a beautiful friendship…

McGill

International workshop on electromagnetic probes of relativistic nuclear collisions

June 2-12, 2005P. Braun-Munzinger, C. Gale, R. Rapp (coordinator)

ECT*EUROPEAN CENTRE FOR THEORETICAL

STUDIES IN NUCLEAR PHYSICS AND RELATED AREASTRENTO, ITALY

charles gale mcgill hard probes 2004 in-medium effects on electromagnetic probes hard probes 2004...

Documents

using “hard probes” – high pt particle & jet...

hard probes 2008, june 8-14th, galicia, spain

review of electromagnetic probes o. drapier llr-École...

study of - hypernuclei with electromagnetic probes at...

a bright future status and perspectives of electromagnetic...

hard probes and the event generator...

electromagnetic probes: messengers from the hot and dense

hard probes in heavy ion collisions at the lhc: pdfs ... ·...

hard probes in pb-pb collisions at...

hard probes at rhic: past, present, and future

the 6 th international conference of hard and...

hard probes at star

hard probes

electromagnetic probes of strongly interacting matter in...

hard probes of the quark gluon plasma lecture i...

hard probes of hot and dense matter concepts formalism...

do we understand interactions of hard probes with dense...

hard probes at lhc theoretical perspective

electromagnetic probes 1 - institute for nuclear...

the future of hard and electromagnetic probes at the sps