Transverse and Longitudinal Dynamics at RHIC

Transverse and LongitudinalDynamics at RHIC

Paweł Staszel, Marian Smoluchowski Institute of Physics

Jagiellonian University

SQM 2007 Levoča, 24–29.06.2007

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2P. Staszel - Jagiellonian University, KrakówSQM 2007, Levoča 2007

BRAHMS

Outline

• General (bulk) characteristics of nucleus-nucleus reactions.

• Nuclear effects at mid- and forward rapidity (RAA and p/)

• Elliptic Flow

• Testing pQCD at large rapidities in p+p

• Summary.


BRAHMS

Particle production and energy loss

Energy density: Bjorken 1983

eBJ = 3/2 (<Et>/ R20) dNch/d

assuming formation time t0=1fm/c:

>5.0 GeV/fm3 for AuAu @ 200 GeV

>4.4 GeV/fm3 for AuAu @ 130 GeV

>3.7 GeV/fm3 for AuAu @ 62.4 GeV

p

p

y

y

BB

yT dyydy

dNm cosh)(

Total E=25.72.1TeV72GeV per participant


BRAHMS

Primary versus produced matter

• longitudinal net-kaon evolution similar as net-proton in |y|< 3 at RHIC (AuAu @ 200 GeV)• strong “association”: net-kaon / net-lambda /net-

proton?

BRAHMS

NA49

AGS

primary matter is concentrated around y3 (y2.0)

At 200GeVcreated matter is picked at y=0

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BRAHMS

Nuclear effects

AuAu @200GeV

Scaled N+N reference

RAA =Yield(AA)

NCOLL(AA) Yield(NN)

Nuclear Modification Factor

RAA<1 Suppression relative to scaled NN reference


BRAHMS

Energy and system dependent nuclear modification factors at h~0 and 1

• R AuAu (200 GeV) < RAuAu(63 GeV) < RCuCu(63 GeV) for charged hadrons

• p+p at 63 GeV is ISR Data (NPB100), RHIC-Run6 will provide better reference

pT [GeV/c]

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BRAHMS

RAuAu(y=0) ~ RAuAu(y~3)

for central Au+Au at √s = 200 GeV

• R AuAu (y=0) ~ RAuAu(y~3) for pions and protons: accidental?

• Rapidity dependent interplay of Medium effect + Hydro + baryon transport

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BRAHMS

Interpretation of suppression at forward y

• G. G. Barnafoldi et al. Eur. Phys. J. C49 (2007)333

• pQCD + GLV fit to RAA → L/λ

• assuming λ=1fm • L~4/1.5fm at mid/forward

rapidity


BRAHMS

Strong energy absorption model - static 2D source. (Insprired by A.Dainese (Eur.Phys.J C33,495) and A.Dainese , C.Loizides and G.Paic (hep-ph/0406201) )

• Parton spectrum using pp reference spectrum• Parton energy loss dE ~ q.L**2• q adjusted to give observed RAA at h~1.

The change in dN/d will result in slowly rising RAA .

The modification of reference pp spectrum causes the RAA to be approximately constant as function of .


BRAHMS

Strong rapiditydependence

CuCu data consistent with AuAu for the same Npart

pp

pp

pbar/- scaling with Npart

sNN=200GeV

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BRAHMS

K/ ratios at y~1 and y~3, Au+Au @200GeV

At y~0 negative and positive ratios behave similar

K/decreases by factor of 2/3 when going from y~0 to y~3, however, enhancement over p+p increases. In accord to pbar/

K/at y~0 is similar that at y~3, however, enhancement over p+p increases

K/ K/

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BRAHMS

Examine d+Au at all rapidities

Cronin enhancement Cronin enhancement suppression suppression

I. Arsene et al., BRAHMS PRL 93 (2004) 242303.

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BRAHMS

RdAu centrality dependence for +

20-40%

40-80%

0-20%

BRBRAHMS PRELIMINARY

At y~3 RdAu for + reflects stronger suppression for more central collisions – same trend as for h

y=3.0

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BRAHMS

Differential flow at forward rapidity

Hydro calculations (red symbols) by T. Hirano

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BRAHMS

p+p at 200GeV – examine pQCD at large yPRL 98 (2007) 252001

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BRAHMS

Large y: pQCD versus data

μ=μF=μR=pT. CTEQ6 parton distribution functions. KKP modified to obtain FFs for specific charges: Dπ+

u = (1+z)Dπ0u ; D

π-u =

(1-z)Dπ0u

AKK reproduce STAR p+pbar at y~0, at large y gluons contribute in > 80%KKP under predict p+pbar by factor of 10.

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BRAHMS

Does baryon number transport extend to high pT?

yb=5.4y

b=-5.4

y

pT

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BRAHMS

p+p @ 62GeV results

BRAHMS PRELIMINARY


BRAHMS

Summary for A+A

• K/p reflects stronger enhancement at forward rapidity as compared to mid-rapidity.

• K/ drops when going form mid to forward rapidity whereas K/ shows weak dependency on rapidity

• RdAu for decreases with increasing centrality and for 0-20% centrality reaches value of ~0.5 (3 < pT < 4)


BRAHMS

Summary for p+p

• At 200 GeV pbar/p is below 0.1 at high pT (~4GeV/c) and y~3.

• This strong asymmetry in p and pbar production can not be described by known FFs.

•Explanation of data require new mechanism that will be able to transport baryon number to high pT

(recombination soft-shower?)

• At the same y but lower energy (62GeV) the effect is stronger by an order of magnitude (both for kaons and protons)

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BRAHMS

I.Arsene7, I.G. Bearden6, D. Beavis1, S. Bekele6 , C. Besliu9, B. Budick5, H. Bøggild6 , C. Chasman1, C. H. Christensen6, P. Christiansen6, R. Clarke9,

R.Debbe1, J. J. Gaardhøje6, K. Hagel7, H. Ito10, A. Jipa9, J. I. Jordre9, F. Jundt2, E.B.

Johnson10, C.E.Jørgensen6, R. Karabowicz3, N. Katryńska3, E. J. Kim4, T.M.Larsen11, J. H.

Lee1, Y. K. Lee4, S.Lindal11, G. Løvhøjden2, Z. Majka3, M. Murray10, J. Natowitz7,

B.S.Nielsen6, D. Ouerdane6, R.Planeta3, F. Rami2, C. Ristea6, O. Ristea9, D. Röhrich8, B. H. Samset11, D. Sandberg6, S. J. Sanders10, R.A.Sheetz1, P. Staszel3, T.S. Tveter11, F.Videbæk1, R. Wada7, H. Yang6, Z. Yin8, and I. S. Zgura9

1Brookhaven National Laboratory, USA, 2IReS and Université Louis Pasteur, Strasbourg, France3Jagiellonian University, Cracow, Poland,

4Johns Hopkins University, Baltimore, USA, 5New York University, USA6Niels Bohr Institute, University of Copenhagen, Denmark

7Texas A&M University, College Station. USA, 8University of Bergen, Norway 9University of Bucharest, Romania, 10University of Kansas, Lawrence,USA

11 University of Oslo Norway

48 physicists from 11 institutions

The BRAHMS Collaboration

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BRAHMS

BACKUP SLIDES

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BRAHMS

q

q

hadronsleadingparticle

leading particle

Schematic view of jet production Particles with high pt’s (above ~2GeV/c) are primarily produced in hard scattering processes early in the collision

Experimentally depletion of the high pt region in hadron spectra

In A-A, partons traverse the medium Probe of the dense and hot stage

p+p experiments hard scattered partons fragment into jets of hadrons

If QGP partons will lose a large part of their energy (induced gluon radiation) suppression of jet production Jet Quenching

High pt suppression jet quenching

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BRAHMS

RAA versus centrality

•Similar level of suppression for central collisions•At forward rapidity RAA shows stronger rise towards peripheral coll. (surface -> volume emission)

preliminary

BE: = 3/2 (<Et>/ S0) dNch/d S is transverse area of overlapping region <Et> derived from and K spectra

New pp data @62GeV will allow for various comparisons at the same rapidities

preliminary

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BRAHMS

RdAu and RAA for anti-protons and pions @200

BRAHMS PRELIMINARY

• suppression for - but stronger for AuAu• both RdA and RAA show enhancement for p-bar


BRAHMS

K-/K+ and antihyperon/hyperon

K-/K+ = exp((2s - 2u,d)/T)pbar/p = exp(-6u,d/T)s=0 K-/K+ = (pbar/p)1/3

Fit shows that K-/K+ = (pbar/p)1/4

s= ¼ u,d

How s= ¼ u,d will work for

hyperons?Hbar/H = (pbar/p)3/4 for Lambdas = (pbar/p)1/2 for Xis = (pbar/p)1/4 for Omegas


BRAHMS

Statistical model and s vserus u,d

Fits with statistical model provide similar u,d/s ratio with weak dependency on y.

This result is consistent with local net-strangeness conservation red line - s = 0black line – fit to BRAHMS data

B. Bieron and W. Broniowski Phys. Rev. C75 (2007) 054905

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BRAHMS

Control measurement: d+Au @ sNN=200

Excludes alternative interpretation in terms of Initial State Effects Supports the Jet Quenching for central Au+Au collisions+ back-to-back azimuthal correlation and jet structure by STAR and PHENIX

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BRAHMS

P/pi ratio: p+p @ sNN=62

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BRAHMS

Nuclear modification factors (RCP, RAuAu) for p,K,p at y~3.1

• Suppression for pions and kaons: RAuAu: < K < p

• RAuAu ≠ Rcp (<Ncoll>,<Npart> for 40-60% ~ 70,56)

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BRAHMS

Flow at forward rapidity

• missing low-pt fraction is important for integrated v2 from FS (can explain about 20% change)

dN 1ddpt 2(1 + 2v1cos +

2v2(,pt)cos2)

dN ddptd

=

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BRAHMS

Constituent quark scaling

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BRAHMS

RAuAu 200 GeV

BRAHMS, PRL 91, 072305 (2003)

Cronin enhancement Cronin enhancement

suppression at high pT

significant medium effects

suppression at high pT

significant medium effects

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BRAHMS

Summary Large hadron multiplicities Almost a factor of 2 higher than at SPS energy( higher ) Much higher than pp scaled results( medium effects)

p/ show strong dependency for given energy depend only on Npar

High-pT

suppression increases with energy for given centrality bin weak dependency on rapidity of RAA which is consistent with surface jet emission RCP can hide or enhance nuclear effects At y=3.2 RAA shows larger suppression than RdA

Identified hadron spectra Good description by statistical model Large transverse flow consistent with high initial density

v2(pt) is seem to not depend on rapidity

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BRAHMS

RdAu Update: Identified Particle RdAu at y~3

• RdAu of identified particle consistent with published h- results• dAu(-)/dAu(+): Valance quark isospin dominates in pp?

BR

AH

MS

P

relim

inary

+ blue- red

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BRAHMS

Limiting FragmentationShift the dNch/d distribution by the beam rapidity, and scale by Npart. Lines up with lower energy limiting fragmentation

Au+Au sNN=200GeV (0-5% and 30-40%)Au+Au sNN=130GeV (0-5%)Pb+Pb sNN=17GeV (9.4%)

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BRAHMS

Other characteristics versus pbar/p

pbar/p controls not only anti-particle to particle ratios but also K/π ratios and K slopes

Transverse and Longitudinal Dynamics at RHIC

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