# Presentation: 942151

## Forward Physicswith a new RHIC II Detector (R2D)

- Peter SteinbergBrookhaven National LaboratoryChemistry Department

## Color Glass Condensate

- Probing the initial-state nuclearwave function with p(d)+A

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## Is hydro just good at the “sweet spot”(midrapidity @ top energies) or isthere a broader systematic?

- Is hydro just good at the “sweet spot”(midrapidity @ top energies) or isthere a broader systematic?

## Serious problems with our understandingthe details of the source, even whenhydro works otherwise.

- Serious problems with our understandingthe details of the source, even whenhydro works otherwise.

## Relevance of Forward Physics

- 	Reduces ambiguities
- Limiting fragmentation
- 	“Energy scan” at a fixed beam energy?
- Baryon dynamics
- 	Still an open issue, esp. effect of longutindal 	expansion
- HBT (PID, γ) in the forward direction
- 	Do 2-particle correlations weaken?
- 	Does longitudinal expansion affect HBT puzzle?
- Long range correlations in η _and_ φ
- 	Imagine v2 _vs. p__T_ in 11 units of η...

## R2D Detector Design from EoI(2 high-rapidity arms)

- R2D Detector Design from EoI(2 high-rapidity arms)

## Everything Counts

- Full tracking & EM calorimetery out to beam rapidity - truly full acceptance
- Particle identification as far as possible, e.g. to separate baryons from mesons
- Full tracking & EM calorimetery out to beam rapidity - truly full acceptance
- Particle identification as far as possible, e.g. to separate baryons from mesons
- Full tracking & EM calorimetery out to beam rapidity - truly full acceptance
- Particle identification as far as possible, e.g. to separate baryons from mesons
- Full tracking & EM calorimetery out to beam rapidity - truly full acceptance
- Particle identification as far as possible, e.g. to separate baryons from mesons
- Full tracking & EM calorimetery out to beam rapidity - truly full acceptance
- Particle identification as far as possible, e.g. to separate baryons from mesons
- Full tracking & EM calorimetery out to beam rapidity - truly full acceptance
- Particle identification as far as possible, e.g. to separate baryons from mesons
- Full tracking & EM calorimetery out to beam rapidity - truly full acceptance
- Particle identification as far as possible, e.g. to separate baryons from mesons
- Full tracking & EM calorimetery out to beam rapidity - truly full acceptance
- Particle identification as far as possible, e.g. to separate baryons from mesons
- Full tracking & EM calorimetery out to beam rapidity - truly full acceptance
- Particle identification as far as possible, e.g. to separate baryons from mesons
- Full tracking & EM calorimetery out to beam rapidity - truly full acceptance
- Particle identification as far as possible, e.g. to separate baryons from mesons
- Full tracking & EM calorimetery out to beam rapidity - truly full acceptance
- Particle identification as far as possible, e.g. to separate baryons from mesons
- Full tracking & EM calorimetery out to beam rapidity - truly full acceptance
- Particle identification as far as possible, e.g. to separate baryons from mesons
- Full tracking & EM calorimetery out to beam rapidity - truly full acceptance
- Particle identification as far as possible, e.g. to separate baryons from mesons
- Full tracking & EM calorimetery out to beam rapidity - truly full acceptance
- Particle identification as far as possible, e.g. to separate baryons from mesons
- Full tracking & EM calorimetery out to beam rapidity - truly full acceptance
- Particle identification as far as possible, e.g. to separate baryons from mesons
- Full tracking & EM calorimetery out to beam rapidity - truly full acceptance
- Particle identification as far as possible, e.g. to separate baryons from mesons

## Need to test hydro awayfrom the “sweet spot”

- Need to test hydro awayfrom the “sweet spot”

- Where doeshydro reallybreak down?

- _Does the “hadronic foam”__get in the way of perfect fluid?_

## In principle, RHIC can compete with HERA at low-xNeed to push as far forward as possible, with high rate to push out in Q2

- In principle, RHIC can compete with HERA at low-xNeed to push as far forward as possible, with high rate to push out in Q2

## Forward J/ψ’s tell us about the structureof the nuclear target...

- Forward J/ψ’s tell us about the structureof the nuclear target...

- ...and they showFeynman (xF) scaling.Worth studying out to η≈3

## An often-missed point:“Feynman-x scaling” and “limiting fragmentation”are essentially the same thing

- An often-missed point:“Feynman-x scaling” and “limiting fragmentation”are essentially the same thing

## “Limiting Fragmentation”

- “Limiting Fragmentation”

## Lots of interest in “energy scans” at RHIC,but we may be able to study similarphysics simply by pushing out in y.RHIC II becomes a comprehensive facility.

- Lots of interest in “energy scans” at RHIC,but we may be able to study similarphysics simply by pushing out in y.**RHIC II becomes a **_**comprehensive**_** facility.**

## Longitudinal Dynamics

- RapidThermalization

- Explosion → gaussian dN/dy

- We need to think seriouslyabout longitudinal physics(I.C., 3D hydro simulations!)

## v1,v3!

- v1,v3!

- Paul Stankus

## Or is it just parton-parton scattering?

- Or is it just parton-parton scattering?

## Everything Counts

- Particle spectra out to the kinematic limit
- Total yields to study the initial state entropy.
- Local and global fluctuations as a probe of thermalization (and phase transitions)
- Chemical equilibrium: local or global in rapidity? Flavor fluctuations as a probe of thermalization
- Validity of the hydrodynamic description away from midrapidity
- Centrality and species dependence of limiting fragmentation
- Leading particles in p+p, p+A and A+A

## Only accessible with a 

- _large-acceptance_ (i.e. not STAR/PHENIX)
- _multi-particle_ (not BRAHMS)
- _spectrometer_ (not PHOBOS)

**Without a detector that satisfies these requirements, ****many basic questions will remain unanswered ****even at RHIC II**

- Many interesting questions in the forward regime.

## R2D

- RHIC ][ Detector

- “May the strong force be with you”

## R2D Expression of Interest, nucl-ex/0503002

- R2D Expression of Interest, nucl-ex/_0503002_

## Interesting uses of the strong force

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