# Presentation: 912801

##  Day-1 Physics   with   

- The RHIC Era Begins
**S. Victoria Greene**
**Vanderbilt University **
**for the PHENIX Collaboration**
**APS Centennial**
**24 March, 1999**

##  Physics Goals for the Relativistic Heavy Ion Collider and for PHENIX

- The ultimate purpose for constructing RHIC is to produce, observe, and study the Quark-Gluon Plasma (QGP)
- The QGP is a state of matter in which the quarks are no longer confined within hadrons and mesons.  This state has been predicted to exist, but there have been no uncontested observations so far.
- The purpose of the PHENIX experiment is to detect and characterize the QGP.
- The biggest challenge facing participants in this quest is that theoretical guidance for observable signatures remains  ambiguous.
- The reward for success will be a glimpse at the state of the universe as it was 10 s after the big bang.

- S. V. Greene

- 24 March 99

##  Design Parameters for the Relativistic Heavy Ion Collider

- RHIC is now nearing completion at Brookhaven National Laboratory and is expected to begin physics operation this November.
- The accelerator will produce collisions between heavy ions up to Au at center-of-mass energies up to  200 • A  GeV
- The design luminosity is 2 X 1026 cm-2 s-1.
- The year-1 luminosity should be 1% of the design goal, with an expected integrated luminosity of 50  b-1.
- For comparison:
- AGS -
- CERN
- LHC

- S. V. Greene

- 24 March 99

- Collaboration  (author list from QM’97 publication)

- S. V. Greene

- 24 March 99

##    The Detection of the Quark-Gluon Plasma 

- A major challenge facing experimenters in the field is that signatures of plasma formation are numerous and theory gives no single clear direction.
- Some primary examples include:
- Deconfinement
- R() ~ 0.13 fm < R(J/) ~ 0.29 fm < R(’ ) ~ 0.56 fm
-  Chiral Symmetry Restoration
- Mass, width, branching ratio of   to e+e-, K+K-  with M < 5 Mev
- Baryon susceptibility, color fluctuations, anti-baryon production
- DCC’s, Isospin fluctuations
- Thermal Radiation of Hot Gas
- Prompt , Prompt * to e+e-, +-
-  Strangeness and Charm Production
- Production of K+, K-  mesons
- Production of , J/, D mesons
-  Jet Quenching
- High pT jet via leading particle spectra
-  Space-Time Evolution
- HBT Correlations of ± ±, K± K±

- S. V. Greene

- 24 March 99

##      Design Philosophy  

- <date/time>

-      Design Philosophy

-  We make the basic assumption that the QGP will be difficult to observe.
- We believe that the QGP will not manifest itself by a single clear signature.  This expectation  is based on observations made so far at AGS and CERN.
- We expect that the QGP will instead be the most consistent description of a number of observations.
- Thus, we plan to produce as large a set of experimental observables as is consistent with geometry and money
- The result is a complex system of layered detectors which measure hadrons, electrons, muons, photons

- See www.phenix.bnl.gov

**FOR MORE INFO...**

##  Acceptance of Final Configuration  

- <date/time>

-  Acceptance of Final Configuration

##      PHENIX - The Plan

- <date/time>

-      **PHENIX - The Plan**

-  **Central Tracking**
** ****Arm  East**

## PHENIX - The Reality 

- <date/time>

**PHENIX - The Reality**

**First  RICH vessel**

##  Multiplicity Measurements

- <date/time>

-  **Multiplicity Measurements**

- Parameters for MVD:
- Two concentric barrels of 300 m Si strips
- Two end-plates of Si pads
- Total coverage: -2.5 <   < +2.5

##   Central Tracking

- <date/time>

-   **Central Tracking**

-  High resolution tracking
- Three sub-systems:
- Drift Chamber
- Pixel-pad Chambers
- Time Expansion Chamber

## High resolution

High granularity

- <date/time>

_*High*_ resolution
_*High*_ granularity

**Electromagnetic****Calorimeter**

## Excellent PID for hadrons

Measure time difference between Beam-Beam (START) counters and “TOF” wall or EmCal elements.
Beam-Beam:
2 x 64 Cerenkov radiators + PMT’s
 ~ 50 ps 
Time-of-Flight (TOF) wall:
~ 2000 PMT’s reading out ~1000 “slats”
 ~ 80 ps
EmCal:
Both PbSc and PbGl have timing capability(greatly extends coverage)
(PbSc) ~ 300 ps
(PbGl) ~ 400 ps

- <date/time>

**Excellent PID for hadrons**
- Measure time difference between Beam-Beam (START) counters and “TOF” wall or EmCal elements.
- Beam-Beam:
- 2 x 64 Cerenkov radiators + PMT’s
-  ~ 50 ps
- Time-of-Flight (TOF) wall:
- ~ 2000 PMT’s reading out ~1000 “slats”
-  ~ 80 ps
- EmCal:
- Both PbSc and PbGl have timing capability(greatly extends coverage)
- (PbSc) ~ 300 ps
- (PbGl) ~ 400 ps

**Particle Identification Using Time-of-flight**

**Calculation by B.A. Cole**

- WA 98

## Particle Identification Using  Cerenkov

- <date/time>

**Particle Identification Using  Cerenkov**

**Excellent electron/hadron discrimination**
- Key Features:
- Ring imaging Cherenkov with gaseous radiator
- Radiator gas:ethane (n = 1.00082) or methane (n = 1.00044)
- Electron identification efficiency: Close to 100% for a single electron with momentum less than ~ 4 GeV/c
- Pion rejection factor: > 103 for a single charged pion with momentum less than ~ 4 GeV/c
- Ring angular resolution: ~ 1 degree in both and 
- Two ring separation:  ~  few degrees in both and 

## Particle Identification using dE/dx

- <date/time>

**Particle Identification ****using dE/dx**

- Additional quality PID information, especially for electron/hadron rejection, from energy loss measurements in TEC:
- Key parameters:
- Total of 29,312 channels on day 1. 42,944 channels after upgrade.
- Determines particle species using dE/dx informatione /   < 2% at 500 MeV/c with Xe gas  e/   ~ 5% at 500 MeV/c with P10 gas.

##  Muon Detectors

- <date/time>

-  **Muon Detectors**

- System of tracking (muTr), identifiers (muID) and absorbers (magnet yoke + muID plates) to absorb hadrons and identify muons with high resolution sufficient to separate
-  from -
- J/  from  ’  ( (M) ~ 90 MeV )
- (1s) from (2s+3s)
- muTr
- 3 stations of 3 cathode strip chambers (CSC) each
- Each CSC consists obtains s ~ 60 m from
- one fine cathode plane,  ~ 100 m
- one coarse cathode plane at a stereo angle of 22.5 degrees  to the fine cathode plane and has a resolution of ~ 3 mm
- anode plane which is perpendicular to the fine cathode plane and has a resolution of~ 3 mm.
- muID
- 6 walls of steel absorber interleaved with layers of plastic proportional tubes of the Iarocci type
- Low energy muon threshold of ~2.2 GeV.

## Data Acquisition

- <date/time>

**Data Acquisition**

- A distributed system designed to read out PHENIX in a “deadtime-less” mode
- Key parameters:
- Recording rate: 20 MB/s
- Level 1 trigger rate: 25 kHz
- Au-Au rate at design luminosity: ~100 Hz

## Vector Mesons in PHENIX

- <date/time>

**Vector Mesons in PHENIX**

- Rate is not the major problem:
- This represents:
- ~10 weeks at   1%  design luminosity
-   ~1 week  at  10%  design luminosity
-   ~1 week  at 100% design luminosity     (without a trigger)
-   ~1 week  at  10 x  design luminosity     (without a trigger)

**Calculation by Y. Akiba**

## Physics in PHENIX

- <date/time>

- **Physics in PHENIX**

- Can measuredecay in “all” channels:
- K+K-
- e+e-
- +-
- In-medium effects could alter branching ratios (Lissauer and Shuryak)
- Trade-off between precision of TOF wall and acceptance of EmCal
- One ~ E859 measurement / day

**Calculation by C. Maguire**

##   0 Detection

- <date/time>

-   0 **Detection**

- Relies on
- Extensive WA80/93/98 experience
- Excellent energy resolution
- Excellent granularity
- Reasonable rates out to at least    pT ~ 10 GeV   ( ~ 10  / hour )   pT ~ 20 GeV   ( ~ 0.1 / hour )
_*Unless*_ there is jet quenching...

## The Year-1 Physics

- <date/time>

**The Year-1 Physics**

- All measurements will be   minimum bias until RHIC reaches  10% of design luminosity
- Topics arranged according to PHENIX Physics working group:
- Global Event - most topics available
- dNch/d  vs.   with MVD
- other centrality measures such as ZDC
- dEt/d  vs.  with EMCal
- 0  pt spectra
- Hadrons - most topics available and can be correlated with global event characterization
- inclusive distributions of identified particles such as ’s, protons, K’s,
- Thermal Photons and Pairs
-  inclusive photons with pt>500-700 MeV
- 0 ’s with pt > 1.5 GeV/c

## Hard Scattering - single particle topics only (no pairs)
high  pt 0 ’s 
identified  , K 
flavor measurements pt<2 GeV/c using TOF and pt>4 GeV/c using Cerenkov    
Light Vector Mesons - some modes available
 to KK
Dalitz with identified electrons 
Decays to e+e- require two arms
Heavy Flavor
possible open charm measurements at pt>~2GeV/c via single electrons  
Spin
accelerator commissioning

- high  pt 0 ’s
- identified  , K
- flavor measurements pt<2 GeV/c using TOF and pt>4 GeV/c using Cerenkov
- Light Vector Mesons - some modes available
-  to KK
- Dalitz with identified electrons
- Decays to e+e- require two arms
- Heavy Flavor
- possible open charm measurements at pt>~2GeV/c via single electrons
- Spin
- accelerator commissioning

**The Year-1 Physics**

- S. V. Greene

- 24 March 99