# Presentation: 483986

## Radial Flow in Au-Au Collisions at 130 GeV

- J. Burward-Hoy
*Department of Physics and Astronomy, University at Stony Brook, New York*
- for the PHENIX Collaboration
- Outline of Topics
-   Motivation
-   Identifying , K, p  in PHENIX
-   mt spectra and Effective Temperature
-   Hydrodynamics-based parameterization
-   Results
-   Conclusions

- APS DNP Spring 2001                       J. Burward-Hoy

- April 28, 2001

## Motivation

- Motivation

- , K, p, anti-p
- 	carry most of energy
- 	collectively flow at t
- 	decouple at Tfo

- low pt:  soft processes
- multiple hadronic rescattering
- hydrodynamic behavior

- high pt:  hard processes
- hard scattering, jets
- pQCD

- RHIC:  Ecm = 130 GeV
- Au on Au collisions

- APS DNP Spring 2001                       J. Burward-Hoy

- April 28, 2001

## Detecting , K, p  in PHENIX

- Detecting , K, p  in PHENIX

- pt = p sin(0)

- PC1 and Event vertex
- polar angle

- DC
- main bend plane

- DC resolution
- p/p ~  1%  3.5% p

- TOF resolution  115 ps

- APS DNP Spring 2001                       J. Burward-Hoy

- April 28, 2001

## Identified particle mt-m0 Spectra

- Used MC single particles and track embedding to correct for
- 	tracking inefficiencies
- 	geometrical acceptance
- 	momentum resolution
- 	decays

- APS DNP Spring 2001                       J. Burward-Hoy

- April 28, 2001

## Effective Temperature

- In the range  mt - m0 < 1 GeV, fit
- and extract the inverse slope Teff

- APS DNP Spring 2001                       J. Burward-Hoy

- April 28, 2001

## Teff and the number of participants

- A Glauber model is used to determine for each centrality
- the number of participants Npart

- APS DNP Spring 2001                       J. Burward-Hoy

- April 28, 2001

## Hydrodynamics-based parameterization

- parameters
- 	normalization A
- 	freeze-out temperature Tfo
- 	surface velocity t

- t

- 1/mt dN/dmt = A  f()  d mT  K1( mT /Tfo cosh  ) I0( pT /Tfo sinh  )

- minimize contributions from hard processes fit mt-m0<1 GeV

- linear velocity profile t() = t
- 	surf. velocity t
- 	ave. velocity <t > = 2/3 t
- 	boost  () = atanh( t() )

- integration variable
- 	  radius  r
- 	=  r/R
- definite integral from 0 to 1
- particle density distribution f() ~ const

- APS DNP Spring 2001                       J. Burward-Hoy

- April 28, 2001

## PHENIX Preliminary

- 5% central data
- 2/NDF = 76/46 = 1.7

- Tfo ~ 100  8 MeV
- t ~ 0.73  0.04
- 	< t > ~ 0.49  0.03

- Systematic errors estimated
-  ~8% in Tfo    ~5% in t

- APS DNP Spring 2001                       J. Burward-Hoy

- April 28, 2001

## Parameter Space:  2 Contours of -K-p

- 5% central

- APS DNP Spring 2001                       J. Burward-Hoy

- April 28, 2001

## Overlap Region in Parameter Space 

- Overlap Region in Parameter Space

- Tfo ~ 125 - 83 MeV ~ 104 MeV
- t ~ 0.6 - 0.8  ~ 0.7
- 	< t> ~ 0.4 - 0.6 ~ 0.5

- CERN Pb-Pb NA49:
- T ~ 132 - 108 MeV ~ 120 MeV
- t ~ 0.43 - 0.67 ~ 0.55

- 2 contour overlap

- Systematic errors estimated  ~8% Tfo    ~5%  t

- APS DNP Spring 2001                       J. Burward-Hoy

- April 28, 2001

## Conclusions

- Fully normalized, centrality selected , K, p/pbar spectra in 130 GeV Au-Au collisions are measured in PHENIX (Summer 2000 runs)
- Teff depends on m0 for both 5% central and minimum bias events.  There seems to be less of a dependence in the 60 - 92% centrality.
- The data suggest sizeable radial flow at RHIC
- A simple model that assumes hydrodynamic behavior is fit simultaneously to the 5% central data.
- Good 2  fits for a finite range of anti-correlated parameters
- 		Tfo  ~ 125 - 83 MeV (~ 8% syst.)		t  ~  0.6 - 0.8 ( ~ 5% syst.)
- In comparison to NA49:
- 		Tfo ~ 132 - 108 MeV 		 	t ~ 0.43 - 0.67
- Use PHENIX HBT analysis results to further constrain the parameters.
- Determine overall systematic uncertainties.

- APS DNP Spring 2001                       J. Burward-Hoy

- April 28, 2001

## Effective Temperature and Linear Fit

**T****eff**** = T****fo**** + m****0**** <********t****>****2**

- Systematic errors included

- 5% central
- Tfo ~ 132 - 166 MeV
- <t> ~ 0.4 - 0.6

- Compared to hydrodynamics-based parameterization:
- 		Tfo within 30%  and <t> within 6%

- APS DNP Spring 2001                       J. Burward-Hoy

- April 28, 2001

## 2 (Tfo,t) Contours

- K

- p

- 2 (Tfo,t) Contours

- 

- positive

- negative

- PHENIX Preliminary

- PHENIX Preliminary

- PHENIX Preliminary

- PHENIX Preliminary

- PHENIX Preliminary

- PHENIX Preliminary

- APS DNP Spring 2001                       J. Burward-Hoy

- April 28, 2001

## Correction Functions

- APS DNP Spring 2001                       J. Burward-Hoy

- April 28, 2001