# Presentation: 848019

## Study of Cronin effect and nuclearmodification of strange particles in d-Au and Au-Au collisions at 200 GeV in PHENIX 

- Dmitri Kotchetkov
*(University of California at Riverside)*
- for PHENIX Collaboration

- Quark Matter’04, Oakland, January 16th, 2004.

##  Strangeness at PHENIX

- Motivations:
- Strange particles as a tool to quantify the effects of medium modification
- Strangeness observables to look into initial (gluon saturation) or final state (quark recombination, flow)
- Effects of strangeness on energy loss
- PHENIX ongoing analyses:
- single

##  Nuclear enhancement and suppression 

- Parallel Session talk
- “/K/p production and
- Cronin effect from p-p,
- d-Au and Au-Au
- collisions at 200 GeV”
- by Felix Matathias

##  Mesons vs. baryons or heavier vs. lighter?

- In central Au-Au collisions:
- No suppression of protons at Pt > 2.0 GeV
- Suppression of 0 up to measurement limits (~10 GeV)

- In central d-Au collisions:
- Nuclear enhancement (Cronin) is larger for protons

##  How strangeness affects nuclear modification?

- Effect of strange quarks on Rcp
- Strange baryons and antibaryons vs. strange mesons (number of quarks)
- Mass dependence of Rcp among strange particles

## Detectors

- Drift Chambers

- Pad Chambers

- PbSc Electromagnetic
- Calorimeter

- Beam-Beam
- Counters

- Time of flight
- Counters

- 900

- 450

- 5.1m

- 2m

- Beam direction

- 0.35...+0.35

- West Arm

- East Arm

## Hadron’s time of flight

- In Time of flight Counters (TOF):

- In Electromagnetic Calorimeter (EMC):

- time of flight resolution:
- TOF: 115 ps			      EMC: 700 ps (average)
- 					  function of energy of a cluster

- P+

- P-

- K-

- K+

- +

- -

- P+

- P-

- K+

- K-

- -

- +

- time of flight  (ns)

- time of flight  (ns)

- charge/momentum (c/GeV)

- charge/momentum (c/GeV)

- high asymmetry of decay
- mean P of  from  decay equals 0.3 GeV
- detect protons in high resolution TOF (up to 3 GeV)
- reconstruct protons into pairs with any hadron detected
- 	either in TOF or EMC
- event mixing technique to build a combinatorial
- 	background

-   reconstruction

##  p invariant mass from d-Au collisions

- From
- 63 x 106 minimum bias d-Au
- collisions:
- 
- Counts = 24395+/-373(stat)
- bar
- Counts = 9744+/-229(stat)

- invariant mass  (GeV/c2)

- invariant mass  (GeV/c2)

- 
- S/B =  1/5
- bar
- S/B = 1/4

- counts/2.5(MeV/c2)

- counts/2.5(MeV/c2)

- Signal+Background

- Background

- Signal

- 

- 

##  p invariant mass from Au-Au collisions

- From
- 20 x 106 minimum bias Au-Au
- collisions:
- 
- Counts = 62786+/-1580(stat)
- bar
- Counts = 48377+/-1358(stat)

- counts      /5(MeV/c2)

- counts /5(MeV/c2)

- 
- S/B =  1/33
- bar
- S/B = 1/33

- Signal

- Signal+Background

- Background

- invariant mass  (GeV/c2)

- invariant mass  (GeV/c2)

- 

- 

-  p invariant mass from Au-Au collisions

##  Detector acceptance normalization 

- Single particle generator (K0S, , e t.c.)
- Simulation of PHENIX detector response
- Extract particle yields as for real data

- Pt  (GeV/c)

- Pt  (GeV/c)

- K0S

- acceptance

- acceptance

##    and -bar Pt spectra in d-Au Minimum bias collisions at 200 GeV

- Poster Strangeness 5
- Arkadij Taranenko

- -> K+K- channel
- identify kaons either in TOF or EMC
- event mixing technique to build a combinatorial
- 	background

-   reconstruction

##  K+K- invariant mass from Au-Au collisions

- From
- 19 x 106 minimum bias
- Au-Au collisions:
- 
- Counts = 5560+/-240(stat)

- S/B = 1/8.5

- counts/1(MeV/c2)

- Posters:
- Strangeness 14
- by Charles Maguire
- Flow 7 by Debsankar
- Mukhopadhyay

- counts/1(MeV/c2)

- invariant mass  (GeV/c2)

- invariant mass  (GeV/c2)

## mt spectra in Au-Au collisions at 200 GeV

- dN/dy=1.340.09(stat) 0.20(syst)
- T=366 11(stat) 18(syst) MeV

- 0-10%

- 10-40%

- 40-92%

- 1/2mT dN/dmTdy (GeV/c2)-2

- MT(GeV/c2)

- PHENIX

- K+K-

- mt spectra in Au-Au collisions at 200 GeV

- 0-10% on correct
- scale, others offset
- by factors of 10

- Parallel Session talk “Light vector
- mesons () in d-Au collisions in
- PHENIX”
- by Richard Seto

## Cronin effect in d-Au collisions

##  Rcp of identified hadrons (0-20% d-Au central collisions) at 200 GeV

- Only statistical errors shown for 

##  Rcp of identified hadrons (20-40% d-Au central collisions) at 200 GeV

- ‘s Rcp modification is very similar to one of the proton

##  Rcp of identified hadrons (40-60% d-Au central collisions) at 200 GeV

- Mass of  is close to one of a proton

## Nuclear modification in Au-Au collisions

##  Rcp of identified hadrons (0-10% Au-Au central collisions) at 200 GeV

-  Rcp of identified hadrons (0-10% Au-Au central collisions) at 200 GeV

- pt (GeV/c)

- Rcp

- nucl-ex/0307022

- (0-10%)/(60-92%)

##  Rcp of  (0-10% Au-Au central collisions) at 200 GeV

-  Rcp of  (0-10% Au-Au central collisions) at 200 GeV

- Mass of  is close to one of a proton

##  Summary

- 	Are differences in Rcp attributable to mass or quark
- 	number?
- There is no evidence for mass dependence of Rcp
- Strangeness seems to have no effect on Rcp
- There is a difference in Rcp for mesons and baryons
- (see STAR results of ’s Rcp in Au-Au)

##  Outlook

- Rcp results from K0S and from  (Au-Au)
- Analysis of multi-strange baryons ( and others)

## Extracted K0S signal

- Extracted K0S signal

- invariant mass  (GeV/c2)

- invariant mass  (GeV/c2)

- counts/2.5(MeV/c2)

- From
- 48.85 x 106 minimum bias p-p collisions:     Counts = 16630+/-605(stat)
- 62.20 x 106 minimum bias d-Au collisions:   Counts = 116397+/-2627(stat)

- d-Au

- p-p

- counts/2.5(MeV/c2)