# Presentation: 354145

## Updated Status and Plansof the PHOBOS Experiment

- Gunther Roland/MIT

**Presentations to **
**RHIC Planning Group and PAC**
**12/03 and 12/05 2003**

##                   Collaboration (Dec 2003)

- Birger Back, Mark Baker, Maarten Ballintijn, Donald Barton, Bruce Becker, Russell Betts,
- Abigail Bickley, Richard Bindel, Andrzej Budzanowski, Wit Busza (Spokesperson), Alan Carroll,
- Patrick Decowski, Edmundo Garcia, Tomasz Gburek, Nigel George, Kristjan Gulbrandsen,
- Stephen Gushue, Clive Halliwell, Joshua Hamblen, Adam Harrington, Conor Henderson,
- David Hofman, Richard Hollis, Roman Holynski, Burt Holzman, Aneta Iordanova, Erik Johnson,
- Jay Kane, Nazim Khan, Piotr Kulinich, Chia Ming Kuo, Jang Woo Lee, Willis Lin, Steven Manly,
- Alice Mignerey, Gerrit van Nieuwenhuizen, Aaron Noell, Rachid Nouicer, Andrzej Olszewski,
- Robert Pak, Inkyu Park, Heinz Pernegger, Corey Reed, Louis Remsberg, Christof Roland,
- Gunther Roland, Joe Sagerer, Pradeep Sarin, Pawel Sawicki, Iouri Sedykh, Wojtek Skulski,
- Chadd Smith, Peter Steinberg, George Stephans, Andrei Sukhanov, Ray Teng,
- Marguerite Belt Tonjes, Adam Trzupek, Carla Vale, Robin Verdier, Gábor Veres, Bernard Wadsworth, Frank Wolfs,  Barbara Wosiek, Krzysztof Wozniak, Alan Wuosmaa, Bolek Wyslouch, Jinlong Zhang
- 	ARGONNE NATIONAL LABORATORY	BROOKHAVEN NATIONAL LABORATORY
- 	INSTITUTE OF NUCLEAR PHYSICS, KRAKOW	MASSACHUSETTS INSTITUTE OF TECHNOLOGY
- 	NATIONAL CENTRAL UNIVERSITY, TAIWAN	UNIVERSITY OF ILLINOIS AT CHICAGO
- 	UNIVERSITY OF MARYLAND	UNIVERSITY OF ROCHESTER

## PHOBOS Future

**Complete Baseline Program in the next 3-4 Runs**
**Essential Items**
**Long Au+Au Run **
**Energy Scan (63 GeV + 1 addt’l Energy)**
**Species Scan (Cu+Cu + 1 addt’l Species)**
**p+p Reference Data**
**Budget constraints link near-term and long-term RHIC running considerations**

## PHOBOS  Status

## RHIC Status

**Unique State of Matter formed in Au+Au**
**Very High Density**
**Equilibrated Strangeness production**
**Collective Behavior in Early Stage**
**Opaque to fast partons**
**What are the initial conditions that lead to these properties?**
**Systematic Study vs **
**Energy Density**
**System Size**
**Rapidity, x****f**
**Data continue to surprise us**

## PHOBOS Detector 2004 (+beyond)

**PHOBOS Detector 2004 (+beyond)**

**Final Configuration**
**Compared to Au+Au Run II:**
**15x faster DAQ **
**2.5x higher PID reach**
**new forward Proton Calorimeters**
**p+p, d+Au Spectrometer Trigger**
**SpecCal for high pT trigger in Au+Au**

- SpecCal

## PHOBOS Capabilities: Multiplicity Array

**PHOBOS Capabilities: Multiplicity Array**

- QM’04 Preview

***PHOBOS preliminary***
**h****+**** + h****-****    *****Au-Au data***

**Phys. Rev. Lett. 91, 052303 (2003)**

**130 GeV: PRL 89:222301, 2002**

## PHOBOS Capabilities: Spectrometer

**p****T ****(GeV/c)**

**0.05**

**0.5**

**5.0**

**Stopping**
**particles**

**dE/dx**

**ToF**

**Continuous Particle ID from low to high p****T**

- QM’04 Preview

- p

- K

- 

**E****loss**** (MeV)**

**dE/dx**

**p (GeV)**

**p (GeV)**

## PHOBOS Capabilities: Spectrometer

**PHOBOS Capabilities: Spectrometer**

**Acceptance *****forward***** of mid-rapidity: 0 < ******** < 2.5**

**Spectrometer **
**Acceptance**

## PHOBOS Future

**Complete Baseline Program in the next 3-4 Runs**
**Essential Items**
**Long Au+Au Run **
**Energy Scan (63 GeV + 1 addt’l Energy)**
**Species Scan (Cu+Cu + 1 addt’l Species)**
**p+p Reference Data**
**Budget constraints link near-term and long-term RHIC running considerations**

## PHOBOS Future

**Complete Baseline Program in the next 3-4 Runs**
**Essential Items**
**Long Au+Au Run ****(Run IV)**
**Energy Scan (63 GeV + 1 addt’l Energy)**
**Species Scan (Cu+Cu + 1 addt’l Species)**
**p+p Reference Data**
**Budget constraints link near-term and long-term RHIC running considerations**

**Crucial Link to d+Au!**

**must-do items**
**in white paper**

## Charged Hadron dN/d Distribution in d+Au

**Parton saturation model prediction ****D. Kharzeev et al., hep-ph/0212316**

**Charged Hadron dN/d******** Distribution in d+Au**

**First result on d+Au min bias multiplicity**
**Many features reminiscent of lower energy p+A data**
**Important lessons for Saturation Model**

** ****nucl-ex/0311009 (subm.to PRL)**

## Charged Hadron dN/d Distribution in d+Au

- Comparison to Parton Saturation and RQMD Models

**Charged Hadron dN/d******** Distribution in d+Au**

**AMPT/HIJING close to data (-5.4 < ******** < 4)**

** ****nucl-ex/0311009 (subm.to PRL)**

## Particle Ratios in d+Au: p/p vs Centrality

**First particle ratio data from d+Au**
**Constant p/p ratio vs centrality **
**Disagreement with expectations/models**

- nucl-ex/0309013 - submitted to PRC

- Au+Au
**Phys. Rev. C 67, 021901R (2003)**** **

## d+Au pT Spectra

**d+Au p****T**** Spectra**

**Phys. Rev. Lett. ****91, 072302 (2003)**

**Au+Au**

**d+Au**

## RHIC d+Au/Au+Au results conclusively 

**show that high p****T**** suppression**
**at mid-rapidity is unique to Au+Au**

## Vitev, CIPANP’03

**Vitev, CIPANP’03**

## Scheduling Considerations

**We considered 27wk/yr, 37wk/yr, 32wk/yr, 37wk/1.5yr, 54wk/2yr scenarios**
**54wk/2yr scenario not workable**
**Scheduling of ****energy/species scan early on critical**** for PHOBOS**

## Species Scan 

**For many observables**
**rapid change from p+p to peripheral Au+Au**
**large uncertainty in <N****part****> for peripheral events**
**Fe+Fe**** overlaps with well-measured <N****part****> range in Au+Au**
**AGS/SPS results on Si+Si vs Pb+Pb show violations of <N****part****> scaling**

**Au+Au**

## Energy Scan

**Energy Scan**

**2x increase in particle density: ****Change from high-p****T ****enhancement to strong suppression**

**SPS**

**RHIC**

- [                          ]

- [     ]

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## Energy Scan

**Shape of excitation function between SPS and RHIC? **

**NA49, SQM’03**

## Summary

**PHOBOS/RHIC Data Set is expanding rapidly**
**Exciting (and puzzling) results in Au+Au and d+Au**
**Further insight from**
**Energy Scan**
**Species Scan**
**p+p reference data**
**Unique**** contributions from PHOBOS**
**Multiplicity Array**
**Spectrometer**
**Very difficult scheduling **
**Timing of species/energy scans is crucial to fully exploit PHOBOS (and RHIC) capabilities**