# Presentation: 670828

## Essential Measurements to be made at RHIC using the PHOBOS Detector

- Mark D. Baker
- Brookhaven National Laboratory
- for the PHOBOS Experiment

- BNL 08-SEP-2004
- Physics Advisory Committee Meeting

##                     Collaboration (Oct. 2004)

**Birger Back,**** ****Mark Baker, Maarten Ballintijn, Donald Barton, Russell Betts, ****Abigail Bickley****, **
**Richard Bindel****, ****Wit**** Busza (Spokesperson), Alan Carroll, Zhengwei Chai, Patrick Decowski, **
**Edmundo Garc****í****a, Tomasz Gburek, Nigel George, Kristjan Gulbrandsen, Clive Halliwell, **
**Joshua Hamblen****, ****Adam Harrington****, ****Michael Hauer****, ****Conor Henderson****, David Hofman, **
**Richard Hollis****, Roman Hołyński, Burt Holzman, ****Aneta Iordanova****, ****Jay Kane****, ****Nazim Khan****, **
**Piotr Kulinich, ****Chia Ming Kuo****, Willis Lin, Steven Manly, Alice Mignerey, **
**Gerrit van Nieuwenhuizen, Rachid Nouicer, Andrzej Olszewski, Robert Pak, Inkyu Park, **
**Heinz Pernegger, ****Corey Reed****, Christof Roland, Gunther Roland, ****Joe Sagerer****, ****Helen Seals****, **
**Iouri Sedykh, Wojtek Skulski, Chadd Smith, ****Maciej Stankiewicz****, Peter Steinberg, **
**George Stephans, Andrei Sukhanov, Marguerite Belt Tonjes, Adam Trzupek, Carla Vale,**** **
**Sergei Vaurynovich****, Robin Verdier, Gábor Veres, ****Peter Walters****, ****Edward Wenger****, **
**Frank Wolfs,  Barbara Wosiek, Krzysztof Woźniak, Alan Wuosmaa, Bolek Wysłouch**
**	****ARGONNE NATIONAL LABORATORY****	****BROOKHAVEN NATIONAL LABORATORY**
**	****INSTITUTE OF NUCLEAR PHYSICS PAN, KRAKOW****	****MASSACHUSETTS INSTITUTE OF TECHNOLOGY**
**	****NATIONAL CENTRAL UNIVERSITY, TAIWAN****	****UNIVERSITY OF ILLINOIS AT CHICAGO**
**	****UNIVERSITY OF MARYLAND****	****UNIVERSITY OF ROCHESTER**

- Mark D. Baker

## The PHOBOS Detector (2004)

**Spectrometer**

**Paddle Trigger Counter**

**NIM A 499 (2003) 603**

**Octagon**

**TOF**

**SpecTrig**

**T0 counter**

**4-******** Multiplicity Detector**
**Comprehensive centrality measures**
**Magnetic Spectrometer + ToF**** **
**Extends to very low pT**
**Good rejection of weak decays**

- Mark D. Baker

## Physics Publications (Sept. 2003)

**Phys. Rev. Lett. 85 , 3100 (2000)**
**Phys. Rev. Lett. 87, 102301 (2001)**
**Phys. Rev. Lett. 87, 102303 (2001)**
**Phys. Rev. C 65 , 31901R (2002)**
**Phys. Rev. Lett. 88 , 22302 (2002)**
**Phys. Rev. C 65 , 061901R (2002)**
**Phys. Rev. Lett. 89 , 222301 (2002)**
**Phys. Rev. C 67, 021901R (2003)**
**Phys. Rev. Lett. 91, 052303 (2003)**
**nucl-ex/0301017, subm. to PRL**
**nucl-ex/0302015, subm. to PLB**
**Phys. Rev. Lett. 91, 072302 (2003)**
**nucl-ex/0309013, subm. to PRC-RC**

- & Comparable # in the pipeline!

- Mark D. Baker

## Physics Publications (Sept. 2004)

**Phys. Rev. Lett. 87, 102301 (2001)**** **
**Phys. Rev. Lett. 87, 102303 (2001)****	**
**Phys. Rev. C 65 , 31901R (2002)****	****	**
**Phys. Rev. Lett. 88 , 22302 (2002) ****	**
**Phys. Rev. C 65 , 061901R (2002) ****	**
**Phys. Rev. Lett. 89 , 222301 (2002) **
**Phys. Rev. C 67, 021901R (2003) **
**Phys. Rev. Lett. 91, 052303 (2003)**
**nucl-ex/0301017, subm. to PRL**
**Phys. Lett. B 578, 072302 (2003)**
**Phys. Rev. Lett. 91, 072302 (2003)**
**Phys. Rev. C 70, 011901R (2004)**
**Phys. Rev. Lett. 93, 082301 (2004)****	****dN/d******** for dAu**
**nucl-ex/0401006, subm. to PRL****	****	****PID at very low p****T**
**nucl-ex/0405003, subm. to PRL****	****	****Energy dependence of R(AA) **
**Phys. Rev. C 70, 021902R (2004)****	****	****Geometric dN/d******** scaling**
**nucl-ex/0406017, subm. to PRC-RC****	****R(dAu) vs. ********	**
**nucl-ex/0406021, subm. to PRL****	****	****v****2**** vs. ********’ at 4 energies****                         **
**nucl-ex/0407012, subm. to PRC-RC****	****v****2**** vs. ********, centrality, p****T**
**nucl-ex/0409001, subm. to PRC-RC****	****HBT vs p****T****, y at 62.4, 200**** ****	****      **
**nucl-ex/0409003, subm. to PRC-RC****	****pbar/p for pp****	**

- >700 citations total

**~20 more in pipeline!**

- Physics Publications (Sept. 2004)

- Mark D. Baker

## Physics Publications (Sept. 2004)

**Phys. Rev. Lett. 87, 102301 (2001)**** **
**Phys. Rev. Lett. 87, 102303 (2001)****	**
**Phys. Rev. C 65 , 31901R (2002)****	****	**
**Phys. Rev. Lett. 88 , 22302 (2002) ****	**
**Phys. Rev. C 65 , 061901R (2002) ****	**
**Phys. Rev. Lett. 89 , 222301 (2002) **
**Phys. Rev. C 67, 021901R (2003) **
**Phys. Rev. Lett. 91, 052303 (2003)**
**nucl-ex/0301017, subm. to PRL**
**Phys. Lett. B 578, 072302 (2003)**
**Phys. Rev. Lett. 91, 072302 (2003)**
**Phys. Rev. C 70, 011901R (2004)**
**Phys. Rev. Lett. 93, 082301 (2004)****	****dN/d******** for dAu**
**nucl-ex/0401006, subm. to PRL****	****	****PID at very low p****T**
**nucl-ex/0405003, subm. to PRL****	****	****Energy dependence of R(AA) **
**Phys. Rev. C 70, 021902R (2004)****	****	****Geometric dN/d******** scaling**
**nucl-ex/0406017, subm. to PRC-RC****	****R(dAu) vs. ********	**
**nucl-ex/0406021, subm. to PRL****	****	****v****2**** vs. ********’ at 4 energies****                         **
**nucl-ex/0407012, subm. to PRC-RC****	****v****2**** vs. ********, centrality, p****T**
**nucl-ex/0409001, subm. to PRC-RC****	****HBT vs p****T****, y at 62.4, 200**** ****	****      **
**nucl-ex/0409003, subm. to PRC-RC****	****pbar/p for pp****	**

- >700 citations total

**~20 more in pipeline!**

- Physics Publications (Sept. 2004)

**(1****st**** Run IV paper)**

**(2****nd**** Run IV paper)**

**(3****rd**** Run IV paper)**

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- AuAu energies:
**19.6, 55.9, 62.4**
- 130., 200.

- Mark D. Baker

## Results from dAu - an update

**PRL 91 (2003) 072302-5**

**dN/d******** data from **
**nucl-ex/0403033**
**J.Phys.G30 (2004) S1133**

- RdA(pT)?

- Mark D. Baker

## Results from dAu - an update

**dN/d******** data from **
**nucl-ex/0403033**
**J.Phys.G30 (2004) S1133**

- RdA(pT)!

**nucl-ex/0406017**

- Mark D. Baker

## The program: vary energy and geometry 

- Varying the geometry (A,b):

- Npart

- eccentricity

-  jet quenching
- vary overall path length
- vary asymmetry
-  Elliptic (and directed) flow
-  Study A dependence at   fixed eccentricity.

- Mark D. Baker

## Surprise from 19.6 & 62.4 GeV AuAu: 

**nucl-ex/0406021**

- Longitudinal scaling
- of elliptic flow

- ’=||-ybeam

- v**2**

- Mark D. Baker

## Surprise from 19.6 GeV AuAu: 

- Surprise from 19.6 GeV AuAu:

**PRC 70 (2004) 021902R**

- Where are the minijets?

- Energy & Centrality Dependences Factorize

- Mark D. Baker

## RAA ratios at 200 and 62.4 GeV (AuAu)

***PHOBOS***

- Large variation of RAA  with centrality
- <Npart> from 61 to 335
- <Ncoll> from 76 to 820
- 0 < b < 10.5 fm

**PLB (2004) 578297**

**arXiv:nucl-ex/0405003**

- Mark D. Baker

## RAA ratios at 200 and 62.4 GeV (AuAu)

**arXiv:nucl-ex/0405003**

- RAA ratios at 200 and 62.4 GeV (AuAu)

- Mark D. Baker

## RAA ratios at 200 and 62.4 GeV (AuAu)

**For b<10.5 fm:**

**arXiv:nucl-ex/0405003**

- RAA ratios at 200 and 62.4 GeV (AuAu)

- Mark D. Baker

## RAA ratios at 200 and 62.4 GeV (AuAu)

**For b<10.5 fm:**

**Energy-independent**
**Weak function of N****part****, p****T**

**arXiv:nucl-ex/0405003**

- RAA ratios at 200 and 62.4 GeV (AuAu)

- Mark D. Baker

## Another surprise from energy variation

**For b<10.5 fm:**

-  Initial state: NN, Ncoll/Npart, Qs(?)
-  System:      , B, Nch,
-  Partonic:     xT, dE/dx

- Varying the beam energy changes:

**arXiv:nucl-ex/0405003**

- Why does the energy dependence factorize?

- Mark D. Baker

## What Have We Learned?& what are the essential measurements w/              ?

- Study the systematics of this “medium” (vary A & sNN).
-  **Furthermore, we have *****discovered***** that much of the data can be expressed in terms of **_***simple scaling rules***_** which suggest the existence of strong global **_***constraints***_** or some kind of universality in the mechanism of the production of hadrons in high energy collisions (possible connection to ideas of parton saturation).**
- Study these simple scaling rules systematically.
- Will they survive further scrutiny?

- What Have We Learned?& what are the essential measurements w/              ?

**http://www.phobos.bnl.gov/Publications/PublicDocuments/****PhobosWhitePaper.pdf  (or .ps)**

## Benefits of very light ions (SiSi e.g.)

- Clearly different from AuAu
- study flow, “jet quenching”
- Extensive low energy comparison data exists (CC,SiSi,SiAl,SS...)
- See BUP refs. 3-15 for a partial listing

**NA49 (C. Hohne et al.), NPA715 (2003) 474c**

- Mark D. Baker

## Benefits of intermediate ions (CuCu) 

- Npart~100 is better determined for central CuCu than for AuAu
- Overlaps both AuAu & SiSi
- Geometry different.
- study flow, “jet quenching”

**nucl-ex/0301017**

- Mark D. Baker

## Benefits of a short pp run @ 400-500 GeV 

- Benefits of a short pp run @ 400-500 GeV

- Compare pp@400 to AA@200.
- Better systematics within a single experiment.
- Better coverage than UA5
- Better statistical power.

**J.Phys.G30 (2004) S1133**** nucl-ex/0403033**

- Mark D. Baker

## Proposed scenario (updated)

- Boundary conditions
- Run CuCu as the light ion species this year
- RHIC will run 7 weeks of pp200 physics
- Phobos does not request _*any*_ pp @ 200 GeV.
- 31 - 10 weeks of setup - 7 weeks pp200
- 14 weeks:
- 200 GeV CuCu (10 weeks physics)
- 62.4 GeV CuCu (3 weeks incl. setup)
- 22.5 GeV CuCu (3 days incl. setup)
- 400 GeV pp (4 days incl. setup)

- Mark D. Baker

## Fallback Scenario (updated)

- Constrained to 10 weeks
- 27 weeks of cryo., still 7 weeks of pp200
- RHIC becomes RppC
- 31 weeks, but 11 weeks for pp @ 200 GeV
- 10 weeks:
- 200 GeV CuCu (7 weeks physics)
- 62.4 GeV CuCu (2.5 weeks incl. setup)
- 22.5 GeV CuCu (3 days incl. setup)

- Mark D. Baker

## Scenarios at a glance

*** = including energy-change setup time**

**d****2****N****ch****/d********d******
**d****2****N/dydp****T**
**HBT**

**d****2****N****ch****/d********d******
**d****2****N/dydp****T**
**HBT**

**d****2****N****ch****/d********d******

**dN****ch****/d******

- Mark D. Baker

## Run VI + ??

- Highest priority: SiSi @ 3 energies
- Other possibilities depend on results
- Longer 19.6 GeV AuAu
- 200 GeV SiAu
- Au-d(yellow)
- ???

- Mark D. Baker

## Summary

- Many new interesting results from Phobos
- Rate of publication growing exponentially.
- “Golden” opportunity in Run V
- RHIC tuned for Cu ions
- PHOBOS-specific features
- Unique  coverage
- Total Nch event-by-event
- Unique centrality measures
- Run CuCu at 200, 62.4 and 22.5 GeV!
- Run VI
- SiSi at 200, 62.4 and 24 GeV
- & base further running on what we learn...

- Mark D. Baker