# Presentation: 000306

## /K/p production and Cronin effect from p+p, d+Au and Au+Au at sNN =200 GeVfrom the PHENIX  experiment

- /K/p production and Cronin effect from p+p, d+Au and Au+Au at *s**NN *=200 GeVfrom the PHENIX  experiment

- Felix Matathias

- The Seventeenth International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (Quark Matter 2004)
- Oakland, January 11-17, 2004

## Overview.

- The role of identified particles.
- Final results from Au+Au collisions.
- The d+Au and p+p run: Initial state and how to disentangle cold vs. hot nuclear matter effects.
- Comparisons: What remains the same, what is different.
- Cronin effect in d+Au.
- Conclusions.

## Production of particles in a dense medium.

- Striking differences between protons and pions.
- Protons scale with Ncoll above pt~1.5 GeV.
- Pions stay suppressed even at pt~7 GeV.
- Particle composition inconsistent with known fragmentation functions 2-5Gev.
- _Exciting Possibility_: a new dominant source for protons from recombination requiring a dense partonic system.
- Other candidates: Baryon junctions, strong radial flow.

- Greco, Ko, Levai: nuclt-th/0301093

- PHENIX: PRL 91, 172301 (2003), nucl-ex/0305036
- PHENIX: Phys. Rev. C, nucl-ex/0307022

## The Cronin Effect & Initial State

- Copious production of hadrons in proton-nucleus collisions.
- R=1  in absence of nuclear effects.
- Bound nucleons “cooperate” producing high-pT particles.
- Suppression at small pT.
- Explained by initial multiple scattering.

- P.B.Straub et al., Phys.Rev.Lett., **68**,452(1992)

- J.Cronin et al. Phys.Rev. D11, 3105(1975)

- Why is it important to know the size of the effect ?
- _Because_:
- A)Cronin.
-        B)Shadowing.
-       C)Saturation.
- constitute the initial state effects that provide the reference for Au+Au calculations.

- A survey of theoretical models: A.Accardi, hep-ph/0212148

## PHENIX RUN03: the d+Au run

- Time of Flight Particle Identification.
- Same techniques and analyses in p+p,d+Au, Au+Au.
- TOF resolution ~135ps
- /K <   2  GeV/c
- K/p < 3.5 GeV/c
- Acceptance: =/8  ,    = 0.7
- 14.3M Events, 30 cm vertex cut.

- 

- 

- p

## Minimum Bias d+Au

- Completely different behavior from central Au+Au.
- Protons do not cross the pions.
- Remarkable agreement with neutral pions.
- Phenix measures pions up to 10 orders of magnitude.

- Mark Harvey: Identified Charged Hadrons at Midrapidity in p+p collisions at RHIC.

## Centrality determination in d+Au

- BBCS (Au-side)  response scales with the number of participants in the Au nucleus.
- Use Negative binomial distributions weighted by a Glauber model to reproduce the BBC charge distribution.
- Assumption is validated by the excellent description of the BBC charge distribution.

**0-20 %   :  15.0 ± 1.0**
**20-40 % :  10.4 ± 0.7**
**40-60 % :    6.9 ± 0.6**
**60-88 % :    3.2 ± 0.3**

- Ncoll

- Poster by Sasha Milov.

## Antimatter over Matterthe 200 GeV case

- A Journey through Quark Matter.

- Phenix beam pipe

## Antimatter over Matterthe 200 GeV case

- p

- p

- Antimatter over Matterthe 200 GeV case

## Antimatter over Matterthe 200 GeV case

- d

- Au

- Antimatter over Matterthe 200 GeV case

## m

- Au

- Au

- Antimatter over Matterthe 200 GeV case

## Antimatter over Matterthe 200 GeV case

- Au

- Au

- Antimatter over Matterthe 200 GeV case

- Independent of colliding system, ~flat in pT  at midrapidity

## d+Au is     following peripheral   Au+Au.
p+p is lower.
Notice:                 Not Feed-down corrected.
Assumes that    /p ratio is  similar in d+Au and Au+Au.
Neutral pions  used to extend    the pt range.

- Proton to Pion Ratio.

- d+Au is     following peripheral   Au+Au.
- p+p is lower.
- Notice:                 Not Feed-down corrected.
- Assumes that    /p ratio is  similar in d+Au and Au+Au.
- Neutral pions  used to extend    the pt range.

## Nuclear Modification from d+Au: Cronin

- Strikingly different behavior in Au+Au and d+Au.
- Clearly pion suppression is a final state effect from a new state of matter.
- d+Au measurement establishes once and for all the initial state at RHIC: shadowing, Cronin, saturation scenarios at y=0.

## Centrality dependence of Cronin.

- Importance of multiple centrality classes.
- Probing the response of _**cold**_ nuclear matter with increased number of collisions.
- Propagation of quarks through the color field of a nucleus.

- Qualitative agreement with model by Accardi and Gyulassy.                     Partonic Glauber-Eikonal approach:                                sequential multiple partonic collisions.         nucl-th/0308029

## Pion RCP from 3 different detectors.

- Charged pions from TOF.
- Neutral pions from EMCAL.
- Charged pions from RICH+EMCAL.

- H. Buesching: Centrality Dependence of Neutral Pion Production in d+Au collisions at 200 GeV
- J.Jia: High pT  production and correlation in d+Au/p+p collisions at s = 200 GeV

## Another Microscopic Mechanism: Saturated Cronin or not ?

- Another Microscopic Mechanism: Saturated Cronin or not ?

- A different approach to the Cronnin effect:
- Intrinsic momentum broadening in the excited projectile proton:
- hpA: average number of collisions:

- X.N.Wang, Phys.Rev.C 61 (2000): no upper limit.
- Zhang, Fai, Papp, Barnafoldi & Levai, Phys.Rev.C 65 (2002): n=4 due to proton                                                                                   d                                                                                                          dissociation.

## Summary

- Properties of identified particle production have been presented for all available colliding systems at RHIC so far.
- Antimatter to matter ratios are independent of colliding systems and consistent with flat in pt at midrapidity.
- Centrality, pt and species dependence of Cronin effect in d+Au fully studied.
- Cronin enhancement increases with centality, quantitative constraints for theoretical models of   multiple scattering.
- Proton Cronin higher than pions but can not explain factor of 5 baryonic enhancement in central Au+Au.
- d+Au looks very similar to peripheral Au+Au.
- Initial state effects in Au nuclei are established at y=0.
- d+Au collisions strongly point towards interpreting Au+Au phenomena as final-state within a dense partonic medium.

##  12 Countries;  58 Institutions;  480 Participants*

**             ****Brookhaven National Laboratory, Upton, NY **
**             ****University of California - Riverside, Riverside, CA**
**             ****University of Colorado, Boulder, CO**
**             ****Columbia University, Nevis Laboratories, Irvington, NY**
**             ****Florida State University, Tallahassee, FL**
**             ****Florida Technical University, Melbourne, FL**
**             ****Georgia State University, Atlanta, GA**
**             ****University of Illinois Urbana Champaign, Urbana-Champaign, IL**
**             ****Iowa State University and Ames Laboratory, Ames, IA**
**             ****Los Alamos National Laboratory, Los Alamos, NM**
**             ****Lawrence Livermore National Laboratory, Livermore, CA**
**             ****University of New Mexico, Albuquerque, NM **
**             ****New Mexico State University, Las Cruces, NM**
**             ****Dept. of Chemistry, Stony Brook Univ., Stony Brook, NY**
**             ****Dept. Phys. and Astronomy, Stony Brook Univ., Stony Brook, NY  **
**             ****Oak Ridge National Laboratory, Oak Ridge, TN**
**             ****University of Tennessee, Knoxville, TN  **
**             ****Vanderbilt University, Nashville, TN****	**

**Brazil        University of São Paulo, São Paulo**
**China        Academia Sinica, Taipei, Taiwan**
**                  ****China Institute of Atomic Energy, Beijing**
**                  ****Peking University, Beijing**
**France      LPC, University de Clermont-Ferrand, Clermont-Ferrand**
**                  ****Dapnia, CEA Saclay, Gif-sur-Yvette**
**                  ****IPN-Orsay, Universite Paris Sud, CNRS-IN2P3, Orsay          **
**                  ****LLR, Ecòle Polytechnique, CNRS-IN2P3, Palaiseau**
**                  ****SUBATECH, Ecòle des Mines at Nantes, Nantes**
**Germany  University of M****ü****nster, M****ü****nster**
**Hungary   Central Research Institute for Physics (KFKI), Budapest**
**                  ****Debrecen University, Debrecen**
**                  ****Eötvös Loránd University (ELTE), Budapest **
**India         Banaras Hindu University, Banaras**
**                  ****Bhabha Atomic Research Centre, Bombay**
**Israel        Weizmann Institute, Rehovot**
**Japan       Center for Nuclear Study, University of Tokyo, Tokyo**
**                  ****Hiroshima University, Higashi-Hiroshima **
**                  ****KEK, Institute for High Energy Physics, Tsukuba **
**                  ****Kyoto University, Kyoto**
**                  ****Nagasaki Institute of Applied Science, Nagasaki**
**                  ****RIKEN, Institute for Physical and Chemical Research, Wako**
**                                               ****RIKEN-BNL Research Center, Upton, NY              **
**	****     ****Rikkyo University, Tokyo, Japan             **
**                  ****Tokyo Institute of Technology, Tokyo**
**                  ****University of Tsukuba, Tsukuba **
**                  ****Waseda University, Tokyo                    **
**S. Korea   Cyclotron Application Laboratory, KAERI, Seoul**
**                  ****Kangnung National University, Kangnung**
**                  ****Korea University, Seoul **
**                  ****Myong Ji University, Yongin City **
**                  ****System Electronics Laboratory, Seoul Nat. University, Seoul**
**                  ****Yonsei University, Seoul**
**Russia      Institute of High Energy Physics, Protovino **
**                  ****Joint Institute for Nuclear Research, Dubna **
**                  ****Kurchatov Institute, Moscow**
**                  ****PNPI, St. Petersburg Nuclear Physics Institute, St. Petersburg**
**                  ****St. Petersburg State Technical University, St. Petersburg**
**Sweden    Lund University, Lund**

*** ******12 Countries;  58 Institutions;  480 Participants****

***as of January 2004**

## backups

## Comparison with neutral pions

## Number of collisions in d+Au.