# Presentation: 593106

## Neutral pions in proton-protoncollisions at s of 200 GeV with PHENIX

- S. Belikov
- for the PHENIX Collaboration

- DNP2002, NSCL/MSU

## Kyoto University, Kyoto, Japan

- Nagasaki Institute of Applied Science, Nagasaki-shi, Nagasaki, Japan
- RIKEN, Institute for Physical and Chemical Research, Hirosawa, Wako, Japan
- University of Tokyo, Bunkyo-ku, Tokyo 113, Japan
- Tokyo Institute of Technology, Ohokayama, Meguro, Tokyo, Japan
- University of Tsukuba, Tsukuba, Japan
- Waseda University, Tokyo, Japan
- Cyclotron Application Laboratory, KAERI, Seoul, South Korea
- Kangnung National University, Kangnung 210-702, South Korea
- Korea University, Seoul, 136-701, Korea
- Myong Ji University, Yongin City 449-728, Korea
- System Electronics Laboratory, Seoul National University, Seoul, South Korea
- Yonsei University, Seoul 120-749, KOREA
- Institute of High Energy Physics (IHEP-Protvino or Serpukhov), Protovino, Russia
- Joint Institute for Nuclear Research (JINR-Dubna), Dubna, Russia
- Kurchatov Institute, Moscow, Russia
- PNPI, St. Petersburg Nuclear Physics Institute, Gatchina, Leningrad, Russia
- Lund University, Lund, Sweden
- Abilene Christian University, Abilene, Texas, USA
- Brookhaven National Laboratory (BNL), Upton, NY 11973
- University of California - Riverside (UCR), Riverside, CA 92521, USA
- Columbia University, Nevis Laboratories, Irvington, NY 10533, USA
- Florida State University (FSU), Tallahassee, FL 32306, USA
- Georgia State University (GSU), Atlanta, GA, 30303, USA
- Iowa State University (ISU) and Ames Laboratory, Ames, IA 50011, USA
- Los Alamos National Laboratory (LANL), Los Alamos, NM 87545, USA
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA 94550, USA
- University of New Mexico, Albuquerque, New Mexico, USA
- New Mexico State University, Las Cruces, New Mexico, USA
- Department of Chemistry, State University of New York at Stony Brook (USB), Stony Brook, NY 11794, USA
- Department of Physics and Astronomy, State University of New York at Stony Brook (USB), Stony Brook, NY 11794, USA
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN 37831, USA
- University of Tennessee (UT), Knoxville, TN 37996, USA
- Vanderbilt University, Nashville, TN 37235, USA

- University of São Paulo, São Paulo, Brazil
- Academia Sinica, Taipei 11529, China
- China Institute of Atomic Energy (CIAE), Beijing, P. R. China
- Laboratoire de Physique Corpusculaire (LPC), Universite de Clermont-Ferrand, F-63170 Aubiere, Clermont-Ferrand, France
- Dapnia, CEA Saclay, Bat. 703, F-91191, Gif-sur-Yvette, France
- IPN-Orsay, Universite Paris Sud, CNRS-IN2P3, BP1, F-91406, Orsay, France
- LPNHE-Palaiseau, Ecòle Polytechnique, CNRS-IN2P3, Route de Saclay, F-91128, Palaiseau, France
- SUBATECH, Ecòle des Mines at Nantes, F-44307 Nantes, France
- University of Muenster, Muenster, Germany
- Banaras Hindu University, Banaras, India
- Bhabha Atomic Research Centre (BARC), Bombay, India
- Weizmann Institute, Rehovot, Israel
- Center for Nuclear Study (CNS-Tokyo), University of Tokyo, Tanashi, Tokyo 188, Japan
- Hiroshima University, Higashi-Hiroshima 739, Japan
- KEK, Institute for High Energy Physics, Tsukuba, Japan

- DNP2002, NSCL/MSU

## Physics Motivation

-  Cross Section **pp**)
-  Provides a testing ground for next-to-leading order pQCD
-  Data baseline for heavy ion physics
-  Transverse Asymmetries (A**N**):
-  Sivers Effect
-  Collins-Heppelmann Effect
-  Higher-Twist Effect(s)
-  Longitudinal Asymmetries (A**LL**):
-  Measurement ofG via leading hadron in jet

- DNP2002, NSCL/MSU

## PHENIX at RHIC

**RHIC run2002 proton-proton run**
- Integrated luminosity 0.15pb-1
- Analyzed luminosity  0.03pb-1
- half of runs are analyzed.
- Vertex position cut +/-30cm
- Sample Size: 140M events
**EMCalorimeter**
- 2 Arm  4 sectors
- Lead Scintillator (PbSc)
- 	6 sectors (15552 channels)
- Lead Glass (PbGl)
- 	2 sectors  (9216 channels)
- ~5m distance from collision point
- ||<0.38  = 180
**Analysis**
- 5 sectors PbSc is used in this analysis
- 1 PbSc/2 PbGl need fine tuning of calibration

- DNP2002, NSCL/MSU

## MIN BIAS Trigger

**Beam – Beam Counters:**
- Two arms, 64 PMTs in each
- ± 1.5 m from the center of  the PHENIX detector.
**Local Level 1 Trigger System:**
-   Determines number of hit PMTs
-  Calculates Vertex position.
- Makes cut on Vertex and hit multiplicity
**LL1 settings in PP run:**
- Nhits>=1 in each arm
- |Vertex| < 75 cm

- DNP2002, NSCL/MSU

## EMCal-RICH level 1 Trigger

- EMCal part has two sums to collect photon shower
- 2x2 towers non-overlapping sum (threshold at 0.8GeV)
- 4x4 towers overlapping sum (thresholds at 2 and 3GeV)
- 0 measurement w/_**2x2 trigger**_ is shown in this talk
- Enhances high-pT 0 by a factor of 90 over min-bias sample.

- 2x2

- 4x4

- 1 PMT

- DNP2002, NSCL/MSU

## 0 Measurement

- Invariant mass spectrum
- The background is smaller than that of heavy ion collisions
- 1-1.5GeV/c N/S = 200%
- pT>5GeV/c  N/S = 10%
- 2x2 trigger worked very well
- Rejection Factor = 90
- Measured 1-15GeV/c 0
- 30 0 at 10-12GeV/c
- 10 0 at 12-15GeV/c

- DNP2002, NSCL/MSU

## Analysis Procedure

- High pT trigger

- True cross section

- Min. Bias  trigger

*N****0**(High)**C****0**reco**(p**T**)*

- DNP2002, NSCL/MSU

## C0reco(pT) : Fast MC Tuning

- Generate 0 at given pT, and decay into two photon
- 0 pT distribution from UA1 (h++h-)/2
- One photon makes one cluster
- Energy resolution
- 		E/E=8.1%/E 2.1%		Tuning 	8.8%/E 4.7%
- Measured by electron and tracking momentum.
- Absolute energy
- 		E/E=+2.5% higher
- Consistent with 0 mass, Ionization energy by h+-, and  E/p by electron
- Position resolution
- 		 =(1.4mm + 5.9mm/E)   20mmcos()	Tuning
- 					(6.4mm + 5.9mm/E)   20mmcos()
- Threshold effect
- Simulate photon shower shape and impose tower energy threshold.

- DNP2002, NSCL/MSU

## C0reco(pT) : Example of Systematic Error Estimation

- Absolute energy calibration compared with 0 mass

- Position resolution compared with 0 width

- Absolute energy
- 	+3.5%
- 	+2.5%
- 	+1.5%

- Position resolution
- 	+1.0cm
- 	+0.5cm
- 	+0.0cm

- DNP2002, NSCL/MSU

## 0(High)(pT) : Trigger threshold

*****0**(High)**(p**T**)* : Trigger threshold

- Direct measurement
- They are consistent
- <10%
- The trigger efficiency saturates at >3GeV/c
- Min. Bias data for 1-3GeV/c
- 2x2 trigger for 3-15GeV/c

- Fast MC
- 10% of 0 data.

- Min. Bias range

- 13GeV/c

- 0 trigger efficiency

- DNP2002, NSCL/MSU

## 0(MB)(pT) : 0 Efficiency in MB Trigger

- 0 slope correction in Min. Bias(MB) trigger
- Since the 4x4 trigger is a self trigger, systematic errors might be
- Multiple hits
- Beam gas/cosmic ray
-  Small effects

- DNP2002, NSCL/MSU

## pT Dependent Systematic Error

- N0		Run dependence			10% (Min. Bias)
- 							  6% (2x2 ERT)
- 			Background subtraction		  5%
- 			Excluded Hot/Bad towers	 	 2-3%
- Creco(pT)		Energy non-linearity		 0-10%
- 			Fast MC statistical error		  1%
- 			Edge tower			  5%
- 			Position resolution		 0-1%
- 			Energy absolute calibration	 3-8%
- 			Energy resolution constant term	 <2%
- 			Energy resolution fluctuation term 	 <2%
-  02x2(pT)	2x2 High pT trigger threshold	 10%

- DNP2002, NSCL/MSU

## 0(MB) : Normalization

- Two methods of luminosity measurement
- PYTHIA/GEANT simulation
- To estimate Min. Bias(MB) trigger efficiency
- Luminosity  = NMB / (**pp**  **MB**)
- van der Meer/Vernier Scan
- Measurement of transverse size of the beam
- By combination of beam current luminosity
- Comparison gauges the systematic error
- There are still some corrections which need to be finalized.
- In this talk, we assigned 30% systematic error
- Because 30% is maximum error for p+p cross section to reach total (inelastic + elastic) cross section

- DNP2002, NSCL/MSU

## Cross section measured over 8 orders of magnitude.
1-13GeV/c
Two triggers
Minimum Bias(MB) trigger
2x2 trigger
They are consistent within systematic error.

- 1-13GeV/c
- Two triggers
- Minimum Bias(MB) trigger
- 2x2 trigger
- They are consistent within systematic error.

- 0 Inclusive Cross Section

- PHENIX Preliminary

*p**T** dependent systematic error*

*Normalization error of 30% not shown.*

*MB trigger*

*2x2 trigger*

- DNP2002, NSCL/MSU

## Comparison with UA1 Fitting

- UA1 data are only up to 6GeV/c and extrapolated to higher pT
- The extrapolation is below our data at high pT
- Now have pp data to use as important reference for Au+Au collision and jet quenching measurement.

- PHENIX Preliminary

- UA1 data

*extrapolation*

*p**T** dependent systematic error*

*Normalization systematic error 30% is not included here.*

- DNP2002, NSCL/MSU

## NLO pQCD calculation
CTEQ5M pdf
Potter-Kniehl-Kramer fragmentation function
 = pT/2, pT, 2pT
Consistent with data within the scale dependence.

- NLO pQCD calculation
- CTEQ5M pdf
- Potter-Kniehl-Kramer fragmentation function
-  = pT/2, pT, 2pT
- Consistent with data within the scale dependence.

- Comparison with QCD Calculation

- PHENIX Preliminary

*p**T** dependent systematic error*

*Normalization error of  30% not shown.*

- DNP2002, NSCL/MSU

## Conclusion

- Measured 0 cross section.
- p**T** from 1 to 13 GeV/c, 8 orders of magnitude change
- results from two triggers (Min. Bias and 2x2) are consistent within systematic error
- Comparison with pQCD with NLO calculation
-     - pQCD calculation agree with data
- Will have A**N**** **at low x**F** / high p**T** from RUN-02
-  A**LL**  (G) in RUN-03

- DNP2002, NSCL/MSU