christina markert 22 nd winter workshop, san diego, march 2006 1 christina markert kent state...

Christina Markert 22nd Winter Workshop, San Diego, March 2006 1

Christina Markert Kent State University

Resonance Production in RHIC collisions

• Motivation• Resonance in hadronic phase RAA, elliptic flow v2• Chiral symmetry restoration (Future plans)• Summary

for the STAR Collaboration

Christina Markert 22nd Winter Workshop, San Diego, March 2006 2

Why Resonances ?

2212

21 ppEEminv

Bubble chamber, BerkeleyM. Alston (L.W. Alvarez) et al., Phys. Rev. Lett. 6 (1961) 300.

Invariant mass (K0+) [MeV/c2]

K*-(892)

640 680 720 760 800 840 880 920

Num

ber o

f eve

nts

0

2

4

6

8

10

Luis Walter Alvarez 1968 Nobel Prize for

“ resonance particles ” discovered 1960

K* from K-+p collision system Kp p

K

Resonances are: • Excited state of a ground state hadron.• With higher mass but same quark content.• Decay strongly short life time (~10-23 seconds = few fm/c ), width = reflects lifetime • Can be formed in collisions between the hadrons into which they decay.

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

RHIC: No strong indication of medium modification (mass, width)But: Indication of extended lifetime of hadronic medium.

= h/t

STAR

Christina Markert 22nd Winter Workshop, San Diego, March 2006 3

Thermal Models Describe Hadronic Yieldshadron-chemistry: particle ratios chemical freeze-out properties

• Tch ≈ TC ≈ 165 ± 10 MeVChemical freeze-out ≈ hadronization.

• s ~ u, d Strangeness is chemically equilibrated.

Thermalized system of hadrons can be described by

statistical model(mass dependence)

~75% pions~15% kaons~10% baryons

STAR white paperNucl Phys A757 (05) 102

Average multiplicity of hadron j (Boltzmann)

)/exp2

12 223

3 TmppdJ

n jj

j

TchemicalTchemical

Christina Markert 22nd Winter Workshop, San Diego, March 2006 4

Hadronic Re-scattering and Regeneration

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

time

chem

ical

free

ze-

out

p

pp

signal lost

kine

tic fr

eeze

-out

signal measured late decay

signal measured

re-scattering

regeneration

[1] Soff et al., J.Phys G27 (2001) 449[2] M.Bleicher et al. J.Phys G30 (2004) 111

Depends on:• hadronic phase density • hadronic phase lifetime Regeneration: statistical hadronic recombination

UrQMD:Signal loss in invariant mass reconstruction (1520) SPS (17 GeV) [1] 50% 26%RHIC (200GeV) [2] 30% 23%

Christina Markert 22nd Winter Workshop, San Diego, March 2006 5

(1520) Results in p+p and Pb+Pb at SPS (1520)/ in p+p and Pb+Pb

C. Markert for the NA49 collaboration, QM2001

NA49 Experiment

Fit to NA49 data[Becattini et al.: hep-ph/0310049hep-ph/0310049]Thermal model does not described

(1520)/ ratio

UrQMD: rescattering of decay particle

signal loss in invariant mass reconstruction

(1520) = 50% , = 26%

Hadronic phase after chemical freeze-out

preliminary

Christina Markert 22nd Winter Workshop, San Diego, March 2006 6

Resonance Signals in p+p and Au+Au collisions from STAR

K(892)

(1520)

p+p

p+p

Au+Au

Au+Au (1385)

p+pAu+Au

(1020) p+p

Au+Au

p+p

K(892) K+

(1232) p+ (1020) K + K(1520) p + K(1385) +

Christina Markert 22nd Winter Workshop, San Diego, March 2006 7

* and* show rescattering * shows regenerationRegeneration/Rescattering cross section:p)

Interactions of Resonance in Hadronic Nuclear 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] :

Preliminary

UrQMD =10±3 fm/c

Christina Markert 22nd Winter Workshop, San Diego, March 2006 8

Temperature and “Life-time” fromK* and * (STAR)

Model includes: • Temperature at chemical freeze-out• “Life-time” between chemical and thermal freeze-out• By comparing two particle ratios (no regeneration)

Lambda1520 T= 160 MeV > 4 fm/c K(892) T = 160 MeV > 1.5 fm/c

(1520)/ = 0.039 0.015 at 10% most central Au+Au

K*/K- = 0.23 0.05 at 0-10% most central Au+Au

G. Torrieri and J. Rafelski, Phys. Lett. B509 (2001) 239

Life time:K(892) = 4 fm/c (1520) = 13 fm/c

Christina Markert 22nd Winter Workshop, San Diego, March 2006 9

Lifetime of Nuclear Medium

TchemicalTchemical

t > 4 fm/cresonances

t ~ 10 fm/c(HBT)

Partonic phase < 6 fm/c

C. Markert, G. Torrieri, J. Rafelski, hep-ph/0206260 + STAR delta lifetime > 4fm/c

Lifetime from:Balance function ?

Christina Markert 22nd Winter Workshop, San Diego, March 2006 10

Signal Loss in Low pT Region

Inverse slope increase from p+p to Au+Au collisions. UrQMD predicts signal loss at low pT due to rescattering of decay daughters. Inverse slopes T and mean pT are higher.Flow would increase pT of higher masse particles stronger.

pT UrQMD 140 MeV 90 MeV 35 MeV

p+p

Au+Au

K(892)

flowpT

Preliminary

Christina Markert 22nd Winter Workshop, San Diego, March 2006 11

RAA of Resonances (with rescattering)

K(892) are lower than Ks0 (and

pt < 2.0 GeV factor of 2K(892) more suppressed in AA than Ks0

Christina Markert 22nd Winter Workshop, San Diego, March 2006 12

Nuclear Modification Factor RdAu

1. K* is lower than Kaons in low pt d+Au no medium no rescattering why K* suppression in d+Au ?

* follows h+- and lower than protons .

Christina Markert 22nd Winter Workshop, San Diego, March 2006 13

Mean pT ≠ early freeze-out ?

Resonance are regenerating close to kinetic feeze-out we measure late produced (1385)How is elliptic flow v2 effected ?

Christina Markert 22nd Winter Workshop, San Diego, March 2006 14

Resonances v2 and NCQ Scaling TestEl

lipti

c flo

w v

2

pT (GeV) Fluid dynamics calculations (zero viscosity) describe data pT < 2 GeV Do Resonances show same mass splitting ? Number of Constituent Quark (NCQ) scaling at intermediate pT (2= mesons, 3= baryons) indication of partonic degrees of freedomRegenerated resonances–final state interactions NCQ = 5 (* = + =3+2)

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

Christina Markert 22nd Winter Workshop, San Diego, March 2006 15

elliptic flow v2 in minbias Au+Au 200 GeV

2(-)

2( -)

dN

/d(

-)

dN/

d(-

)

signal

Bg of invmass

v2=12±2%

v2=16±0.04%

pT = 1.0-1.5 GeV

Inv mass (K+ K-)

Inv mass (K+ K-)

Elliptic flow

)](2cos[21 2 RvddN

Reaction plane

Kaon p < 0.6 GeV

Christina Markert 22nd Winter Workshop, San Diego, March 2006 16

v2 of phi resonance in Au+Au 200GeV

has long lifetime 45fm/c less rescattering or regenerationElliptic flow of Φ-meson is close to Ks Delta resonance ?

STAR PreliminarySTAR Preliminary

Christina Markert 22nd Winter Workshop, San Diego, March 2006 17

Resonance Response to Medium

Tc

par

tons

ha

dron

s

Baryochemical potential (Pressure)

Temperature

Quark Gluon Plasma ( perfect liquid)

Hadron Gas

T Freeze

Shuryak QM04Resonances below and above Tc: Gluonic bound states (e.g. Glueballs) Shuryak hep-ph/0405066 Survival of mesonic heavy quark

resonances Rapp et al., hep-ph/0505080 Initial deconfinement conditions:

Determine T initial through J/ and state (+resonance states)

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 22nd Winter Workshop, San Diego, March 2006 18

Chiral Symmetry Restoration

Ralf Rapp (Texas A&M) J.Phys. G31 (2005) S217-S230

Vacuum At Tc: Chiral Restoration

Hendrik van Hees (talk)Measure chiral partnersNear critical temperature Tc (e.g. and a1)

Data: ALEPH Collaboration R. Barate et al. Eur. Phys. J. C4 409 (1998)

a1 +

TOF cut |1/-1| < 0.03

STAR: electron hadron separation with Time of Flight upgrade

STAR Experiment

Christina Markert 22nd Winter Workshop, San Diego, March 2006 19

Resonances from Jets to Probe Chirality

Bourquin and GaillardNucl. Phys. B114 (1976)

T=170 MeV, T=0 Leadinghadrons

Mediumaway

near

• In p+p collisions resonances are predominantly formed as “leading particles” in jets. • Comparison of mass, width and yield of resonances from jets (no medium) with resonances from bulk (medium)

jets ?

Christina Markert 22nd Winter Workshop, San Diego, March 2006 20

Summary

• Hadronic resonances help to separate hadronic from partonic lifetime

• Ranking of rescattering over regeneration cross section in medium.

•Low pt RAA behavior confirms rescattering hypothesis. (RdAu puzzle?)

• v2 of long lived resonances seems to follow stable particle trends (confirmation of NCQ scaling)

• Exciting future program: resonance in jets.