# Presentation: 867770

## The Strange Physics Occurring at RHIC

- Workshop on Strangeness and Exotica
- R. Bellwied, H. Caines, C.Pinkenburg, J. Velkovska
- RHIC & AGS Annual Users Meeting
- BNL
- May 10-14th  2004

**A theoretical view of the collision**** **

- Tc – Critical temperature for transition to QGP
- Tch– Chemical freeze-out (Tch  Tc) : inelastic scattering stops
- Tfo – Kinetic freeze-out     (Tfo  Tch): elastic scattering stops

-  Hadronic ratios.
- Resonance production.
-  pT spectra.
-  Partonic collectivity.
-  High pT measurements.

- 2

## Baryon transport to mid-rapidity

**Baryon transport to mid-rapidity**

-  Clear systematic trend with collision energy

-  Very similar trend between heavy ion and p-p

-  62.4 GeV data fits into pattern

- R. Witt

- E866 -

## Resonance ratios

**Resonance ratios**

**Thermal model [1]:**
- Tch = 177 MeV
- B = 29 MeV

- [1] P. Braun-Munzinger et.al., PLB 518(2001) 41  D.Magestro, private communication
- [2] Marcus Bleicher and Jörg Aichelin
-       Phys. Lett. B530 (2002) 81-87.
-       M. Bleicher, private communication

- Need >4fm between Tch and Tfo

- UrQMD [2]

**Life time [fm/c] :**
** ********     ****=  40 **
** *********   =  13 **
** ****K*  =    4**** **
** **

- Small centrality dependence:
- 	 little difference in lifetime!

- Nch

- NOT ENOUGH

- O. Barranikova

## Resonance Feed-down

**********-******** ********- ****+********n**

- Particle mass close to pdg value

- Width ~ 10MeV

******+******** ********+ ****+********n**

-   + +p ?
- p misidentified asn

- Phenix Preliminary

- Might finally be able to answer  question about  contamination of 

- C. Pinkenburg

## Measuring through both channels

- Φ  K+K- (min bias 200 GeV)
- Mass and width agree within errors
-              with  PDG values

**Yield**

**Mass (GeV/c****2****)**

- Φ  e+e- (min bias 200 GeV)

- D. Mukhopadhyay

## Modeling the Spectra

-  K0s upper
-  lower
-  Centrality (0-5%)
-  HIJING/BBar v2.0 right
-  HIJING v1.37 left

-  Also reasonable ratios
- as function of centrality

- V. Topor-Pop

- Need extra strings and rope breaking to obtain strange particle yields

##  Low pT results

- -1 for mesons
- +1 for baryons

- Au+Au sNN = 200 GeV

**PHENIX - open symbols**
**PHOBOS –closed symbols**

- Solid line = fit to PHENIX spectra
- Dashed line = extrapolation of fit

- This fit extrapolates smoothly to the low-pT points
-  No enhancement of low-pT particle yields

- PHENIX spectra for mT < 1GeV/c2 fit with:

- Low pT results are vital for
-  getting spectral shapes

- C. Henderson

## pT vs Mass

-  ISR parameterization fails for heavy particles
-  Same <pT> for p-p and Au-Au for heavy particles?

-  Different <pT> with Nch, heavier particles different mult. bias

- R. Witt

## Phase space suppression less at RHIC

**Phase space suppression less at RHIC**

-   See drop in “enhancement” at higher energy for 
-   Enhancement values not as predicted by model
-   Correlation volume not well modeled by Npart

- 130 GeV

- STAR Preliminary 200 GeV

- H. Oeschler

## Suppression of identified particles

- Two groups (2<pT<6GeV/c): - K0s, K, K*, PHENIXhave mesons - 	                       baryons

- Rcp

- Clearly not mass dependence
- Higher stats. this run get  and 

- Come together again
- at pT ~ 6 GeV?
- “standard” fragmentation?

-  show different
- behaviour to  K
-   Suppression of** **K sets
-  in at lower pT

****

**K**

- Mass or meson/baryon
- effect?

- C. Mironov

## Parton coalescence and medium pT

**Parton coalescence and medium p****T**

- recombining partons:
- p1+p2=ph

-  When slope exponential:
-                    coalescence wins
-  When slope power law:
-                          fragmentation wins

- fragmenting parton:
- ph = z p, z<1

- Mesons

- Baryons

- Recombination
-      p(baryons) > p(mesons) >  p(quarks)
-     (coalescence from thermal quark
-                                       distribution ...)
- Pushes soft physics for baryons out to
-       4-5 GeV/c
- Reduces effect of jet quenching

- Do soft and hard partons recombine or just soft+soft ?
-                       Explore correlations with leading baryons and mesons

- C. Nonaka

## v2 and coalescence model

**v****2**** and coalescence model**

- Hadronization via quark coalescence:
- v2 of a hadron at a given pT is the partonic v2 at pT/n scaled by the # of quarks (n).

-  Works for K0s,  & 
-   v2s ~ v2u,d ~ 7%

- D. Molnar, S.A. Voloshin Phys. Rev. Lett. 91, 092301 (2003)
- V. Greco, C.M. Ko, P. Levai Phys. Rev. C68, 034904 (2003)
- R.J. Fries, B. Muller, C. Nonaka, S.A. Bass Phys. Rev. C68, 044902 (2003)
- Z. Lin, C.M. Ko Phys. Rev. Lett. 89, 202302 (2002)

**Au+Au ********s****NN****=200 GeV**

- R. Seto

## What about Strangeness in p-p?

- p-p is not necessarily the best baseline
- Phase space suppression of strangeness in p-p

- C. Mironov

## Pentaquarks at RHIC

**Pentaquarks at RHIC**

|    +n+K- |
| --- |
|      +  p +K0 |
| p  |
|  |

- Au-Au Minbias
- STAR Preliminary

- Some possible peaks need more investigation

- STAR Preliminary

- S. Kabana, C. Ko, L. Guo, C. Pinkenburg

## Summary

**Summary**

- pQCD

- ReCo

- Hydro

- Different physics for different scales

- Strange particles are useful probes for each scale

-   All evidence suggest RHIC creates a hot and dense
- medium with partonic degrees of freedom.
-  Only just beginning to understand the rich physics of RHIC.
-  Lots more to come and much already on TAPE!

## Agenda

-  STAR strangeness bulk properties – O. Barannikova
-  STAR strangeness pp results – R. Witt
-  Phi Production in PHENIX – D. Mukhopadhay
-  Strangeness production in PHOBOS – C. Henderson
-                               Break
- Thermal Model calculations for RHIC/SPS – H. Oeschler
-  HIJING model calculations – V.Topor-Pop
-  Intermediate pT results in PHENIX – R. Seto
-                              Lunch
-  Intermediate pT results in STAR – C. Mirinov
-  Recombination model calculations – C. Nonaka
-  Pentaquark results from JLAB – L. Guo
-  Pentaquark results from PHENIX – C. Pinkenburg
-                               Break
-  Pentaquark results from STAR – S. Kabana
-  Pentaquark production – theory input – C.M. Ko
-  Roundtable – What’s next for Strangeness – All
-                              Adjorn

- BACK UP

## Determining spin and parity

- 	         K+ d  + p
-  Intrinsic parity    -   +      +?   +

- 	         K+ p  + +
- Intrinsic parity    -   +     +?   -

- Parity Conserved  1= (-1)L n1n2
- L =  If – Ii

- L = Odd

- L = Even

-                    K+ d  +     p
- spin                      0  1     1⁄2(?)  1⁄2

-               K+ p  +     +
- spin          0  1     1⁄2(?)  0

- L = 1

- L = 0

- L determines the decay angular distribution

- Determination of spin and parity will help select between theories

- Correlated quark & Chiral soliton models predicts Jpc=1⁄2+ (p-wave)
- Quark model naïve expectation is Jpc=1⁄2− (s-wave)

**Interpretation of the ********+**

## Thermal model reproduces data

- Data – Fit (s)                         Ratio

- Do resonances
- destroy
- the hypothesis?

- Used in fit

- Created a Large System in Local Chemical Equilibrium

## Experimental Evidence for +

- Currently 6 Experiments have identified a peak

- CLAS p->
- +K*

- Spring-8

- Diana
- KXe->+N

- Saphir

- p-> **+** Ks0

- ITEP
- Ne->K0sp+

- Hermes

## Kinetic Freeze-out

-  ,K,p: Tkin decreases with centrality
-   Tkin = const., coincides with Tch !
- Large flow, lots of re-interactions, thermalization likely

- *A. Baran et al.; nucl-th/0305075.

## <pT> Systematics in p-p at 200 GeV

- p+p at 23 GeV

- Mass dependence even in p-p. Not flow!

## Temperature and Lifetime Centrality Dependence

_**Model includes: **_
-   Temperature at chemical freeze-out
-   Lifetime between chemical and thermal freeze-out
-   By comparing two particle ratios (no regeneration)
** **_**results between : **_
** ****T= 160 MeV  => ********  > 4  fm/c  ****(lower limit !!!)**
** ******** ****= 0 fm/c    => T= 110-130 MeV **

******(1520)/******** = 0.034 ******** 0.011 ******** 0.013  **

**K*/K****- ****= 0.20 ******** 0.03 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**

## Quantifying the Correlation Strength

- Correlation difference defined as : ***N******same***** - *****N******back***

-   Suppression of  as a function of pT is   slightly different from the , K0s and primaries.
-   Under investigation whether this is an experimental effect or whether there is indeed sensitivity to quenching or production mechanism effects

## What Does a RHIC Collision Look Like?

- A Central  Au+Au Collision:
- Npart  sNN       = 40 TeV
- 	             ~ 6 Joule
- Our Ears are sensitive to
- 		 ~10-11 ergs			= 10-18 Joule
-                       = 10-12 Joule
- If a RHIC Collision was converted solely into noise that‘s one

- BIG BANG!

- HI Collisions converted into COPIOUS particle production

## mT Scaling 

- _data / power law_

**m****T**** Scaling **

- In p-p

- Not in Au-Au

##  Charged Particle Trends

**200/130 ratios:**
**Consistent with being flat: **
**	**
**<N****ch****> ratio: 1.19********0.05 (sys)**
******p****t******** ****ratio: 0.99 ********0.02 (sys) **

- No increase of <pt>   loss of early information?
- Maximum Missing Information  thermalization?

- Only true for ,  need detailed PID information...

- STAR Preliminary

## Hydro Calculation of v2

- P. Kolb, J. Sollfrank, and U. Heinz

-  ** **Large v2 is an indication of early thermalization

- Heavy-Ion Collisions create a system which approaches hydrodynamic limit** **

- A pressure build up ->  Explosion
- 	zero for central events
- 	self quenching
- Elliptic flow observable sensitive to early evolution of system
- Collective motion + large energy density 	**->**Hydrodynamics
-     Assumes continuum matter with      local equilibrium, “thermalization”

**Equal Energy Density lines**

## Hadron Suppression for Identified Particles

- STAR Prelimimary

****

**********s**

- Seem to come together at ~6GeV/c  - “standard” fragmentation?

- Is this a mass effect or a baryon/meson effect ?

## Different Physics for Different Regions

- pT

- pQCD

- Hydro

- 2-3 GeV/c

- 6-7 GeV/c ?

**Soft**

**Fragmentation and quenching**** of jets**

- 0

**What do we think we know ?**

**What are the mechanism(s) at****intermediate p****T****?**

## Baryon/Meson Ratios vs Collision Centrality

-  /K0s ratio increases with increasing centrality
- peaks in the intermediate pT region.
- turns over and appears to tend to the same value for all centralities for pT ~ 5-6 GeV/c.
- Therefore pT range of baryon excess is limited  to < 5-6 GeV/c.
- Not yet down to level in pp data

-  Strong baryon/meson modification in Au + Au for in /K0s ratio  as reco.  predicts

## The STAR Detector

**Magnet**
**Coils**
**Central **
**Trigger**
**Barrel **
**(CTB)**
**ZCal**
**Time **
**Projection **
**Chamber**
**(TPC)**
**Year 2000**

**Barrel EM Cal (BEMC)**
**Silicon Vertex Tracker (SVT)****Silicon Strip Detector (SSD)********Vertex Detector**
**FTPC****Endcap EM Cal****FPD**
**TOFp, TOFr****Year 2001/2003**
**Year 2006+**

## Flow of multi-strange baryons 

-  , K, p: Common thermal freeze-out at Tfo   ~ 90 MeV
-         <> ~ 0.60 c
-  : Shows different thermal freeze-out behavior:
-          Tfo     ~ 160 MeV
-         <> ~ 0.45 c

- But:
- Already some radial flow!

- Tfo ~ Tch Instantaneous Freeze-out of multi-strange particles?
- Early Collective Motion?

- Higher temperature
- Lower transverse flow
- Probe earlier stage of collision?