Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 1

Resonances at RHIC and LHC

Christina MarkertUniversity of Texas at Austin

• Motivation• Resonances in hadronic phase System size/energy dependence• Chiral symmetry restoration Leptonic decays, jets• Resonances at the LHC • Conclusions

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 2

Why Resonances ?

Resonances are:

• Excited state of a ground state hadron.• With same quark content but higher mass • Decay strongly short life time (~10-23 seconds = few fm/c ), width = reflects lifetime

Why Resonances?:• Short lifetime decay in medium • Surrounding nuclear medium may change resonance properties• Chiral symmetry restoration: Dropping mass -> width, branching ratio

= h/t

Resonance Lifetime [fm/c] decays e+e-

pp+Ke+e-

Jccbar)e+e- +-

bbbare+e- +-

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 3

Resonance formation in heavy ion reactions

1.) Resonances created at the beginning of the collision before it melts into a Quark Gluon Plasma (QGP)

potentially survive in partonic matter (QGP)2.) Most resonances are formed when partonic matter

transitions back into hadronic matter sensitive to phase transition properties i.e.

deconfinement, chiral symmetry restoration.3.) Sensitive to hadronic matter due re-scattering and

regeneration

3.)

Preequili-brium

QGP Mixedphase

0

0.1

0.2

0.3

0.4

0.5

1 2 3 4 5 6 7 8 9 10

Protons Lambdas

Lam

bda

Delt

a

0 dir

ect

dir

ect

* 0

% o

f to

tal yie

ld

1.)

2.)

Hadron gas

temperature

TcTi TkinTchem

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 4

Resonances are the Key Probe for QCD Phase Resonances are the Key Probe for QCD Phase Transition(s)Transition(s)

Because of lifetime and strong interactions with the medium, light vector mesons are the only probe of

chiral symmetry restoration

Because of color screening in the medium, heavy vector mesons are the most sensitive probe of

deconfinement conditions

BR K+K-/BR e+e-

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 5

Resonance response to medium

Tc

part

on

s

had

ron

s

Baryochemical potential (Pressure)

Temperature

Quark Gluon Plasma

Hadron Gas

T Freeze

Shuryak QM04

Resonances below and above Tc:

Initial deconfinement conditions: Determine T initial through

J/ and state dissociation

Chiral symmetry restoration Mass and width of resonances

Hadronic phase evolution From hadronization (chemical freeze-out) to kinetic freeze-out.

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 6

Hadronic re-scattering and regenerationch

em

ical

free

ze-

out

p

p p

kin

etic

fre

eze

-out

re-scattering

regeneration

e+

e-leptonic decay

hadronic decay

+X Y (*)

+X Y (K*)

+X Y (*)

UrQMD calculations

Sascha Vogel, WWND 2006 hep-ph/0607242

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 7

Lifetime of nuclear medium

TchemicalTchemical

resonances

time ~ 10 fm/c2 particle correlation Partonic phase

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 8

Interactions of resonances in hadronic medium

[1] P. Braun-Munzinger et.al.,PLB 518 (2001) 41,priv. communication[2] Marcus Bleicher and Jörg Aichelin Phys. Lett. B530 (2002) 81. M. Bleicher and Horst Stöcker J. Phys.G30 (2004) 111.

Life-time [fm/c] :

Regeneration/Rescattering cross section:p)

Lifetime of hadronic medium:C. Markert, G. Torrieri and J. Rafelski, hep-ph/0206260T= 160 MeV > 4 fm/c (lower limit)UrQMD: = 13 ± 3 fm/c

Phys. Rev. Lett. 97 (2006) 132301

In agreement with UrQMD calculations

[1] [2]

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 9

Resonance suppression (system size dependence)

Phys. Rev. Lett. 97 (2006) 132301 Phys. Rev. C71 (2005) 064902See S. Dash SQM2007

Life-time [fm/c] :K(892) = 4.0 =(1520) = 13 (1020) = 45

STAR Preliminary

A Lordanova SQM2007

From statistical modeland blastwave fits of ,K,p

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 10

Resonance suppression (energy dependence)

STAR preliminary

Phys. Rev. C71 (2005) 064902nucl-ex/0703033See S. Dash SQM2007

Life-time [fm/c] K(892) = 4.0 (1020) = 45

STAR preliminary

M. Bleicher et al.

statistical errors only !

Less re-scattering at lower energies in peripheral collisionsSame volume but,• Lower density smaller interactions cross section?• Shorter hadronic lifetime less hadronic interactions ?

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 11

(1520) signal in Cu+Cu 200 GeV

Signal significance = 14

Study system size dependence of (1520)

Breit-Wigner-fit: m = 1514 1 4 MeV/c2 = 18 MeV/c2 (fixed)

Particle Data Group:1519.5 1.0 MeV/c2

15.6 1.0 MeV/c2

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 12

Resonance response to medium

Tc

part

on

s

had

ron

s

Baryochemical potential (Pressure)

Temperature

Quark Gluon Plasma

Hadron Gas

T Freeze

Shuryak QM04Resonances below and above

Tc:

Initial deconfinement conditions: Determine T initial through

J/ and state dissociation

Chiral symmetry restoration Mass and width of resonances ( e.g. leptonic vs hadronic decay, chiral partners and a1)

Hadronic time evolution From hadronization (chemical freeze-out) to kinetic freeze-out.

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 13

Measurable effects of chiral symmetry restoration

Mass shift

Width broadening

Branching ratio change

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 14

PDG K*0

PDG K*±

STAR Preliminary

MC

No evidence for chiral symmetry restoration

- small mass shifts in all system sizesK*

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 15

Leptonic decay vs hadronic decay (PHENIX)

QM2006 nucl-ex/0702022

(1020) yield from leptonic decay looks higher than from hadronic decay

What happened to the mass and the

width?

leptonic decay

hadronic decay

What about leptonic decay contribution from regenerated resonances ?

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 16

near-side

STAR Preliminary

near

away

Study Chiral Symmetry Restoration by comparing resonance production in event classes based on azimuthal distribution:

We expect high pT resonances from the away side jet to be medium modified due to the high density and temperature of the partonic and pre-equilibrium hadronic medium

CM: arXiv:nucl-ex/0706.0724

Resonances from jets to probe chirality

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 17

Formation of hadronic resonances (from jets) in a chiral medium

side 1

side 2

near

away

Low pt High pt

Near side

No medium or late hadronic medium

No medium

Away side

Late hadronic medium

Partonic or early hadronic medium (depend on formation time) CSR ?

Side 1&2

Late hadonic medium

Early hadronic medium

5GeV/c

10GeV/c

20GeV/c

Heavier particles of same momentum

formed earlierHigh momentum

particles formed later

Need to determine the right momenta for trigger and resonance particle

CM, R. Bellwied, I. Vitev in preparation

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 18

Hadron - resonance correlation in Au+Au

of h-(1020) – C • h-(1020) mixed event

QM2006 M.Horner

STAR preliminary

ZYAM = zero yield at minimum

Hadron trigger pT > 4 GeV (1020) <pT > ~ 0.9 GeV ( need higher pt )

Not corrected for acceptanceSystematic BG normalization error not included

Not corrected for v2

51385±2369

64498±2400

No mass shift or width broadening visible No evidence for chiral symmetry restoration at low pt resonances

Look at higher momentum resonances

near - side

away- side

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 19

Resonances at the LHC

Higher initial temperature Tc: Larger Partonic lifetime. What is the hadronic lifetime ? hadronic decay of resonances

Larger cross section of hard scattering processes

Resonance Program requires:

1.) Good particle identification capability

ALICE detector

PID: TOF, TPC, TRD, EMCAL 2.) And jet reconstruction capability: EMCAL + fast trigger 10-100 enhancement of jets

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 20

Resonances from Jets

30M di-jets (pT > 30 GeV/c)per year in EMCAL

Resonance production from EMCAL triggered jets pT > 30 GeV/c (in one year)500K (1020) at pT = 4 GeV/c

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 21

Jet/hadron - resonances correlation (Pythia)

of h-(1020) – C • h-(1020) mixed event

Including realistic background of(1020) resonance of sig/bg =2%

hadron trigger pT > 15 GeV/cassociated (1020) pT > 4 GeV

jet trigger pT > 30 GeV/cassociated (1020) pT > 4 GeV

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 22

Resonance Reconstruction at ALICE

(1020)

A. Badalà- SQM07

(1520)

Institutes at LHC – ALICE working on resonances (,K*,L*)INFN Sezione di Catania- ItalyUniversity of Athens, Greece

Hadronic lifetime

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 23

Conclusion

• Low momentum resonances provide information regarding the lifetime of the hadronic stage, and therefore determine indirectly the partonic lifetime of the system.

• The re-scattering cross section exhibits same system size dependency in Au+Au and Cu+Cu collisions.

• Lower collision energy results in less hadronic interactions.

• High momentum resonances from jets could be used as a tool to trigger on early produced resonances and test chiral symmetry restoration

• New STAR TOF detector will help to study higher pT resonance and leptonic decays.

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 24

LHCHigher initial temperature Hadronic lifetime ?Larger cross section for jet production

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 25

Time of Flight upgrade detector at STAR

STAR: Time of Flight detector upgrade:• PID at higher momentum • Electron hadron separation• Installation completed in 2-3 years

STAR Experiment

|1/β-1|<0.03

J.WU QM2006

Improves reconstruction of hadronic and leptonic decay channels:K* K+, p*p

ee

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 26

New idea: Resonances from jets to probe chirality

Bourquin and GaillardNucl. Phys. B114 (1976) • In p+p collisions resonances are

predominantly formed in jets.

jets ?

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 27

Regeneration might increase elliptic flow

C. Nonaka, et al.,Phys.Rev.C69:031902,2004

Data suggest small regeneration for K* (need smaller errors !)

minbias 200 GeV Au+Au

Partonic resonance generation:Number of Constituent Quark (NCQ) scaling at intermediate pT (meson NCQ = 2)

Hadronic resonance (re)generation:Regenerated resonances–final state interactions NCQ = 4 (* = + =2+2)

Phys. Rev. C71 (2005) 064902

Recombination model

15% increase

Christina Markert 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas,5-12 April 2008 28

di-electron invariant mass distribution from PHENIX

A significant excess is observed at low mass (m<1GeV/c) in Au+Au minimum bias

p+p Au+Au minimum bias

arXiv:0706.3034 [nucl-ex]

Hugo Pereira Da Costa SQM2007(Alberica Toia QM2005)

What about leptonic decay contribution from regenerated resonances ?

Talk by B. Llope The STAR Time of Flight detector (better PID)