# Presentation: 655388

## Study of Charged Hadrons Spectra with the Time Expansion Chamber of the PHENIX Experiment at the Relativistic Heavy Ion Collider

- Dmitri Kotchetkov
*University of California at Riverside*

## The Relativistic Heavy Ion Collider (RHIC)

- Project objectives:
- To detect and study a new
- state of matter, quark-
- gluon plasma (QGP)
- from Au-Au collisions:
- in 2000 at C.M. energy of 130 GeV;
- in 2001 at C.M. energy of 200 GeV (design);
- To understand the spin
- structure of the nucleon
- from proton-proton
- collisions:
- in 2001 at C.M. energy of 200 GeV.

**N**

**S**

## Pioneering High Energy Nuclear Interaction eXperiment (PHENIX)

- To study signatures of QGP
- through kinematical and dynamic
- properties of electrons, muons,
- hadrons, and photons coming out
- of the collision point.
- Array of 11 subsystems for
- unbiased research.
- 2000: 4 million Au-Au minimum
- bias (all impact parameters)
- events recorded;
- 2001: 170 million Au-Au minimum
- bias events recorded (with 92
- million minimum bias and 14
- million rare events available for
- analysis) and 190 million p-p
- events.

**N**

**S**

**W**

**E**

- The Time
- Expansion
- Chamber

## Passage of a Track through the PHENIX East Central Arm

- Multiplicity Vertex Detector

- Drift Chamber

- Pad Chamber 1

- Ring Imaging Cherenkov Detector

- Time Expansion Chamber

- Pad Chamber 3

- Time of Flight

- Electromagnetic Calorimeter

- East

- Beam Line

- 5 cm

- 205 cm

- 245 cm

- 410 cm

- 260 cm

- 480 cm

- 500 cm

- 510 cm

- Distances are closest to the vertex, not scaled

- 400

## Functions of the Time Expansion Chamber (TEC) in the PHENIX

- A) Measures charged particle ionization
-     energy losses (dE/dx):
-     Separation of electrons from pions:
-     1) over a momentum range 0.25 -3 GeV (e/ is 5% at 500 MeV),
-     2)	after upgraded to the Transition Radiation Detector (TRD), over a momentum range 0.25-50 GeV via transition X-radiation detection (e/is 1.5% at 500 MeV).
- B) Tracks all charged particles and produces
-     direction vectors that match tracking
-     information from the Drift and Pad
-     Chambers to complete track determination
-     in the PHENIX.
-     Single point track resolution of 250 m and
-     two track separation of 2 mm.
- C) Measuring the transverse momentum of
-     a charged particle.

- PHENIX East Central Arm

- TEC

## Geometry of the TEC

- 2000

- 2001

## Design Parameters of the TEC

- 1) Arranged in 6-plane 4 sectors (in 2000
- and 2001 only 4 planes were
- instrumented electronically).
- 2) Covers 900 of the PHENIX azimuthal
- angle and 0.35 units of pseudorapidity
- (approximately 400 of the polar angle
- ).
- 3) Distance from the collision vertex
- approximately R = 410-457 cm.
- 4) 64,080 wires and 20,480 readout
- channels.

- 5) Filled with Ar-CH4 (P-10) gas (90% of
- argon and 10% of methane) with the
- effective gas gain of 10000 (in 2000
- and 2001 the effective gas gain was
- 2000-5000). (Gain is the number of
- electrons produced in a signal wire by
- one electron knocked out by a charged
- track).
- 6) Dimensions of the planes:
- 3.00 m x 1.69 m for the smallest and
- 3.49 x 1.90 m for the largest.
- 7) 320 Front-End Modules (FEM) and 640
- Preamplifier/Shaper Boards (PS)
- (in 2001 216 FEMs and 432 PS Boards).

- TEC six-plane sector

## Mechanical Design of the Plane

- 68 mm

- 30 mm

- 4 mm

- Electric field

- Filled with
- Ar-CH4
- (P-10) gas

- Cu-Mylar
- windows

- 8 mm

- cathode
- (Au-Cu-Be)

- anode
- (Au-W-Re)

- To be filled with
- TRD fiber radiator

- Drift velocity
- 15-50 mm/s

- beam
- direction

- East

- charged
- particle

- 6 mm

## Electronics chain

- From
- anode

- 95 ns preamplifier

- Tail cancellation

- Gain x25

- Gain x5

- dE/dx

- TR

- 32 channel Preamp/Shaper board

- Flash Analog-
- Digital
- Converter

- Digital Memory
- Unit
- Data Delay and
- Buffering

- Data
- Formatter
-  PHENIX
- format

- To PHENIX
- Data
- Collection
- Module

- FPGA
- Data format

- Timing and mode bits

- ArcNET
- Board configuration
- Digital parameters

- Communication

- 64 channel
- Front-End
- Module

## Signal sampling

- 28 level ADC (dE/dx)

- 3 level ADC (TR)

- Analog
- voltage

- Gain x25
- dE/dx

- Gain x5
- TR

- Encoder

- 3 bits

- 28 bits

- 5 bits

- To Digital
- Memory
- Unit

- FADC

- dE/dx signal: 0.2-0.3 keV (MIP in Xe)
- TR signal: 3-10 keV (X-rays in Xe)

- Timing distributions
- for reconstructed charged
- particles

## Track reconstruction

- y

- x (East)

- azimuthal
- angle

- inclination angle

- charged particle

- TEC

- reference circle
- R = 450 cm

- 

- 

- beam
- direction

- Hit pairs on the same track have the same and 
- A peak in the  space indicates the track.

- Transverse momentum as a function of :
- pt = 1/(21.5*.

- In 2000 the transverse momentum resolution is 4.8%+5.5%*pt

**Studied by A.Lebedev, S. Bhagavatula, and M. Rosati*

## Analysis motivations

- Third paper published by PHENIX deals with suppression of hadrons at high pt. Analysis was done on Run-2000 data with tracks reconstructed exclusively in the PHENIX Drift Chamber.
- 2.    It is reasonable to do similar analysis of high pt hadrons reconstructed exclusively from the TEC tracks.
- That makes cross-check and correctness estimate on the PHENIX published result.
- Estimate how well the Time Expansion Chamber can perform as a tracking device.

## Data Sample from the Run-2000

- PHENIX East Central Arm

- Time Expansion Chamber

- Electromagnetic Calorimeter

- Time of Flight

- Pad Chamber 3

- Pad Chamber 1

- Tracks reconstructed in the Time
- Expansion Chamber in association
- with hits in the Pad Chamber 1
- (PC1), Pad Chamber 3 (PC3),
- Time of Flight (TOF), and
- Electromagnetic Calorimeter (EMC).
- No Drift Chamber Tracks.

## TEC Tracks in 2000

- Sector 2
- (4 planes)

- Sector 1
- (4 planes)

- Data taken

- Data in
- analysis

- Analysis centrality selection:
- 1) Minimum bias;
- 2) 0-5%;
- 3) 5-15%;
- 4) 15-30%;
- 5) 30-60%;
- 6) 60-92%.;
- 7) 0-10%.

- Analysis is performed separately for positive
- and negative particles for each centrality bin.

- 1.3 million minimum bias events and
- 11 million tracks

## Corrections

- 1. Ghost tracks, i. e. “unphysical” background is found though Z-flip
-     method of subsystem’s hit and performing track association with
-     flipped hit.
- 2. Association cut efficiency.
- 3. Acceptance.
- 4. Surviving probability.
- 5. Physical background.
- 6. Momentum resolution 4.8%+5.5*pt%.
- 7. Tracking efficiency.
- 8. Track splitting and merging (negligible in TEC, found as ratio of angles
-     Phi between two tracks from mixed events and the same events.

## Acceptance

- Fiducial area

- Fiducial area

- Vertex range:
- -30cm<Z<30cm

- Hardware acceptance:
- dead areas are 8%

## Track association and tracking efficiency

-  Background

- Signal +
- background

- Measure closest distances between TEC
- tracks and associated hits in PC1, PC3,
- TOF, EMC, and between projection of
- the tracks to the collision vertex and
- the vertex for 60-80% peripheral events.

- Tracking efficiency found as a ratio of the number of found simulated tracks
- embedded into data tracks to the total
- number of embedded  tracks. Function of
- the number of data tracks.

## Relative spatial resolution 

## Track association efficiency

- Efficiency of association cuts as
- function of transverse momentum
- for 60-80% peripheral events

- no cut

- cut on all
- subsystems

- Plot the distributions of TEC track
- association with the collision vertex:
- 1) without making any association cut
- on any subsystem; 2) making 3-
- (or 2- ) cuts on all subsystems.
- Find the ratio of the maxima
- of these distributions, which will be
- the association cut efficiency.

## Surviving probability and physical background  

- Physical background correction
- function is found through simulation
- as ratio of the total number of particles
- found in the TEC to the number of
- primary particles found in the TEC.

- Pions

- Kaons

- Probability that hadrons would
- decay prior reaching the TEC

## Transverse momentum spectra 

- PHENIX preliminary

- 0-5%
- 5-15%
- 15-30%
- 30-60%
- 60-80%
- 80-92%

## Comparison with the Drift Chamber results

- 0-10% central events

- 60-80% peripheral events

- Drift Chamber
- (nucl-ex/0109003)
- Time Expansion
- Chamber

- Drift Chamber
- (nucl-ex/0109003)
- Time Expansion
- Chamber

- PHENIX preliminary

- PHENIX preliminary

## Presentations by UCR

- Hardware:
- 	1. “Front-End Electronics for the PHENIX Time Expansion Chamber”,
-            2001 Nuclear Science Symposium and Medical Imaging Conference,
-            November 4-10, 2001, San Diego (published proceedings).
-       2. “The Time Expansion Chamber of the PHENIX Experiment at
-            the Relativistic Heavy Ion Collider”, 2002 Spring Meeting of the
-            California Section of the American Physical Society, March 29-30,
-            Davis, California
- Analysis:
-       1. “Study of charged hadrons with the PHENIX Time Expansion Chamber”,
-           XIV National Nuclear Summer School, July 28 – August 10, 2002,
-           Santa Fe, New Mexico.
-       2. “Study of charged hadrons with the PHENIX Time Expansion Chamber”,
-           poster presentation at XV International Conference on Ultra-Relativistic
-           Nucleus-Nucleus Colli

## Upgrade

- Ongoing upgrade into the Transition Radiation Detector (capable of pion/electron separation for momenta beyond 50 GeV) by:
- 	a) electronically instrumenting from 4 to 6 planes,
- 	b) installing polypropelene fiber radiators in front of  	 each wire plane,
- 	c) use xenon-helium-methane (Xe-He-CH4) gas mixture.
- 	(All work to be finished by the middle of December 2002)
- 2)	Possible construction of the TEC in the PHENIX West Central Arm (2005).