# Presentation: 268663

## Rcp Measurements Using the PHENIX Muon Arms for √sNN=200 GeV d+Au Collisions. 

- Rcp Measurements Using the PHENIX Muon Arms for √sNN=200 GeV d+Au Collisions.

- Andrew GlennUniversity of Coloradofor the PHENIX collaborationFebruary 9, 2005

- Andrew Glenn University of Colorado

- 21st Winter Workshop on Nuclear Dynamics

## Motivation: Understanding the Initial State

- Jet suppression in Au+Au collisions at RHIC is seen as a possible evidence for deconfinement.
- Collisions of small with large nuclei can help us to quantify whether or not this is due to initial state effects/parton saturation or final state effects.

- Andrew Glenn University of Colorado

- 21st Winter Workshop on Nuclear Dynamics

## Nuclear Modification Factor: RAA

- We define the nuclear modification factor as:
- At mid-rapidity (for pions)
- RAA<<1 for Au+Au
- RdA>1 for d+Au
- Supporting evidence for “jet quenching”. d+Au was needed to show final state effect.

- Andrew Glenn University of Colorado

- 21st Winter Workshop on Nuclear Dynamics

## PHENIX Muon Detectors

- Muon arms
- 1.2<|η|<2.4
- Δφ=2π
- P>2 GeV/c
- Triggers
- “Muons”
- Stopped hadrons
- Light meson decays
- Heavy decays

- Two ways for Muon armsto study hadrons.

- Andrew Glenn University of Colorado

- 21st Winter Workshop on Nuclear Dynamics

## Interacting Hadrons

- Hadrons interactelectromagneticallyAND strongly.

- Stopped muons (peak)

**steel**

- Interacting Hadrons (tail)

- Andrew Glenn University of Colorado

- 21st Winter Workshop on Nuclear Dynamics

## Muons from Light Meson Decays

- Muon event collision vertex distribution

- 

- 

- Muon
- detector

- absorber

- Muon pT ~ 0.85 parent pT

- η > 0

- Detector

-  D   c = 0.03 cm      Decays before absorber
-      c = 780  cm     Most are absorbed, but some decay first
-  K    c = 371 cm      Most are absorbed, but some decay first
- γcτ >> 80cm

- 

- Andrew Glenn University of Colorado

- 21st Winter Workshop on Nuclear Dynamics

## RCP measurement

- RCP measurement

- Andrew Glenn University of Colorado

- 21st Winter Workshop on Nuclear Dynamics

## Centrality and Nbin   

- Event centralities are defined as hard cut regions of BBC south hit distribution by the percentages of total dAu inelastic cross section
- Number of hits in south BBC is proportional to Au participants. The relation between them follows Negative Binominal Distribution.
- By comparing the number of hits distribution from data and the NBD, a hard cut region of BBC hit distribution can be mapped to an nbinary distribution.

- Andrew Glenn University of Colorado

- 21st Winter Workshop on Nuclear Dynamics

## Bias due to BBC response

**      ****BBC as a detector responds to different physics processes in different ways.**
-  _***Effect one***_ : Inelastic collisions with a hadron in our central or muon arm acceptance are more likely to fire the BBC detector than an unbiased inelastic collision. This causes a _*trigger bias*_ in the yield because BBC+hadron events can be seen by BBC more easily than BBC events.
_***Effect two***_ : In general, hard binary collisions produce more particles. BBC may see more tracks. This causes  the mapping from BBC nhit to nbinary different for different event categories. We call it _*bin shifting*_.
- For Rcp measurement, we need to take care both of trigger bias and bin shifting .
- Results in 0-7% corrections

- Andrew Glenn University of Colorado

- 21st Winter Workshop on Nuclear Dynamics

## PHENIX Results

- PTH = Punch Through HadronsHDM = Hadronic Decay Muon

*nucl-ex/0411054 (accepted by PRL)*

- Andrew Glenn University of Colorado

- 21st Winter Workshop on Nuclear Dynamics

## PHENIX Results II

- Au

- d

- Au

**1.5 > p****T**** (GeV/c) > 4.0**

- Suppression at forward η. Slight enhancement in the backward η?

- Andrew Glenn University of Colorado

- 21st Winter Workshop on Nuclear Dynamics

## Compare with BRAHMS

- Basically consistent. Systematically somewhat more forward suppression?

- Andrew Glenn University of Colorado

- 21st Winter Workshop on Nuclear Dynamics

## Physics at forward rapidities

- New regime of parton physics at low-x.
-  Can be reached by going to large rapidities.

- For Au nuclei
- (Going N to S)

- For deuterons
- (Going S to N)

- Andrew Glenn University of Colorado

- 21st Winter Workshop on Nuclear Dynamics

## Coherent Multiple Scattering 

- Depletion of small-x partons in a nucleus compared to those in a nucleon (_Shadowing_).
- Coherent multiple scattering can lead to dynamical nuclear shadowing.
- Leads to suppression at forward rapidities/more central events.

*Qiu & Vitev hep-ph/0405068*

- Andrew Glenn University of Colorado

- 21st Winter Workshop on Nuclear Dynamics

## Direct Comparison with FGS

- SGFS,ρ

- SFGS,WS

- Calculation for BRAHMSRCP which has a different centrality definition.
- (R. Vogt arXiv:hep-ph/0405060)
- The FGS shadowing parameterization does not reproduce the data well.

- Hadron Punch Through

- Andrew Glenn University of Colorado

- 21st Winter Workshop on Nuclear Dynamics

## Recombination 

- Recombination of soft and shower partons leads to a reduction of the soft parton density in the deuteron side.
- Explains the forward backward asymmetry and why RCP (protons) > RCP (mesons) at midrapidity.

*Hwa, Yang and Fries nucl-ex/0410111*

- BRAHMS data

- Andrew Glenn University of Colorado

- 21st Winter Workshop on Nuclear Dynamics

## Color Glass Condensate

- Color Glass Condensate

- Parton model => nucleon consists of “free” point-like constituents: quarks and gluons.
- _Color__ __Glass__ __Condensate_ is a QCD based theory for the dense partonic matter at small-x and predicts depletion of scattering centers through gluon fusion processes (gluon saturation).

***k****** ****is transverse momentum of partons *
***Q******s**** **is saturation scale*

*D. Kharzeev hep-ph/0307037*

*Increasing y*

- Andrew Glenn University of Colorado

- 21st Winter Workshop on Nuclear Dynamics

## CGC Model Comparison

- Hadron Punch Through

- Centrality and rapidity dependence are roughly correct.
- This calculation does a slightly better job of reproducing the BRAHMS data.

- Calculation from* Kharzeev *arXiv:hep-ph/0405045

- Andrew Glenn University of Colorado

- 21st Winter Workshop on Nuclear Dynamics

## Summary

- We have measured charged hadron RCP using the PHENIX Muon Arms for d+Au collisions.
- Much care is required for d+Au centrality.
- We observe:
- Slight enhancement on the Gold going direction (South Arm).
- Suppression on the Deuteron going direction     (North Arm).
- Forward suppression is qualitatively consistent with several theories from shadowing/saturation type effects. Various possible contributions.
- Slight enhancement at backward rapidity is not well understood (anti-shadowing).

- Andrew Glenn University of Colorado

- 21st Winter Workshop on Nuclear Dynamics

##  12 Countries;  58 Institutions;  480 Participants*

**USA   Abilene Christian University, Abilene, TX **
**             ****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****	**

*** ******12 Countries;  58 Institutions;  480 Participants****
***                          ******* as of January 2004***

**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 Münster, Münster**
**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**

- Andrew Glenn University of Colorado

- 21st Winter Workshop on Nuclear Dynamics

## Decay Muons

-  Light hadrons like pions and kaons can decay into muons before reaching the MuID.
- The decay probability of a meson with momentum p is proportional to the distance (L) between collision vertex and absorber:
- Hence by looking at the the z-vertex distribution for events with single muon candidates, we can separate the muons that come from pions/kaons from other contributions.

- Andrew Glenn University of Colorado

- 21st Winter Workshop on Nuclear Dynamics

## Muon Production

- Origins of muons
- PYTHIA p+p @ √s=200GeV
- low PT:
- light hadron decays
- high PT:
- Heavy quark decays

- Muon PT distribution

- Andrew Glenn University of Colorado

- 21st Winter Workshop on Nuclear Dynamics

## QM’04

- Andrew Glenn University of Colorado

- 21st Winter Workshop on Nuclear Dynamics

## Physics at forward rapidities

- New regime of parton physics at low-x.
-  Can be reached by going to large rapidities.

- For Au nuclei
- (Going N to S)

- For deuterons
- (Going S to N)

- Andrew Glenn University of Colorado

- 21st Winter Workshop on Nuclear Dynamics